JP2012056555A - Tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire for a motorcycle, in which the tire is excellent in both of turning performance and turning stability.SOLUTION: The tire 2 for a motorcycle includes a tread 4, a pair of side walls 6, a pair of beads 8, a carcass 10, a band 12, a pair of reinforcing layers 14 and a pair of cushioning layers 16. The tire 2 has a radial structure, and a band cord of the band 12 is helically-wound in a circumference direction. An absolute value of an angle made by a reinforcing cord of the reinforcing layer 14 with respect to the circumference direction is 20° or more and 45° or less. A ratio (X1/TW) of a distance X1 to a half-width TW of the tread is 0.35 or more and 0.50 or less. A ratio (X2/TW) of the distance X2 from an outer end in the axial direction of the cushioning layer to the equator to the half-width TW of the tread is 0.8 or more and less than 1.0.

Description

  The present invention relates to a motorcycle tire.

  Highways are being developed, and high-speed driving performance is required even for motorcycles. A radial tire is excellent in high-speed running performance. Radial tires are also used in motorcycles. In this radial structure tire, there is a tire in which a cord of a band layer is spirally wound in the circumferential direction from the viewpoint of riding comfort and straight running stability. This tire has excellent grounding properties.

  On the other hand, this tire tends to have an excessively small tread rigidity during turning. Camber thrust and cornering force tend to be too small during turning. In particular, in a large motorcycle, a so-called waist break phenomenon may occur, and steering stability may be impaired.

  JP-A-3-231003 discloses a tire in which a reinforcing layer is provided outside the band layer. This reinforcing layer is located in the shoulder portion of the tread. In the tire provided with this reinforcing layer, the rigidity of the tread is improved. Large camber thrust and cornering force can be obtained during turning. However, in this tire, when an external force is applied from the road surface during turning, the stability of the turning (turning stability) deteriorates, for example, the tire is shaken to cause vibration or vibration of the vehicle body. Further, when the width of the reinforcing layer is increased, the rigidity of the tread is increased, and the ride comfort in the straight traveling is deteriorated.

  Japanese Patent Application Laid-Open No. 10-181310 discloses a tire in which the angle of the reinforcing cord of the reinforcing layer is 70 degrees to 90 degrees. Thereby, this tire is made so that the rigidity of the tread shoulder portion does not become too large. In this tire, the vibration of the vehicle body and the like are suppressed while the waist breaking phenomenon during turning is suppressed. This tire achieves both cornering performance and cornering stability as compared with the tire disclosed in JP-A-3-231003.

JP-A-3-231003 Japanese Patent Laid-Open No. 10-181310

  Even in the tire disclosed in Japanese Patent Application Laid-Open No. 10-181310, the rigidity of the tread is improved by the reinforcing layer. Even in this tire, the contact pressure of the tread portion that contacts the ground during turning is high. Even in this tire, road surface followability is impaired by providing the reinforcing layer. Also in this tire, further improvement in turning performance and turning stability is desired.

  An object of the present invention is to provide a tire excellent in both turning performance and turning stability.

A motorcycle tire according to the present invention includes a tread whose outer surface forms a tread surface, a pair of sidewalls, a pair of beads, and one bead and the other bead along the inside of the tread and the sidewall. A pair of reinforcements stacked with a carcass spanned between them, a band laminated on the outer side in the radial direction of the carcass, and a band outside the band in the radial direction and spaced apart with an equatorial plane in the tire axial direction And a pair of buffer layers stacked on the outer side in the radial direction of the reinforcing layer. This carcass includes a large number of carcass cords arranged in parallel. The absolute value of the angle formed by each carcass cord with respect to the equator plane is 70 ° or more and 90 ° or less. This band has a band code. This band cord is spirally wound in the tire circumferential direction. The reinforcing layer includes a number of reinforcing cords. The absolute value of the angle formed by each reinforcing cord with respect to the tire circumferential direction is not less than 20 ° and not more than 45 °. The buffer layer is made of a crosslinked buffer rubber. This buffer layer covers the radially outer peripheral surface of the reinforcing layer. The ratio (X1 / TW) of the distance X1 from the inner end in the axial direction of the buffer layer to the equator and the half width TW of the tread is 0.35 or more and 0.50 or less. The ratio (X2 / TW) of the distance X2 from the outer end in the axial direction of the buffer layer to the equator and the half width TW of the tread is 0.8 or more and less than 1.0.

  Preferably, in the tire, the tread is made of a crosslinked tread rubber. The complex elastic coefficient (Ed) of the buffer rubber is made smaller than the complex elastic coefficient (Et) of the tread rubber. Preferably, the ratio (Ed / Et) between the complex elastic modulus (Ed) of the buffer rubber and the complex elastic coefficient (Et) of the tread rubber is 0.7 or more and less than 1.0.

  Preferably, in this tire, a ratio (DH / TH) of the buffer layer thickness DH to the tread thickness TH is not less than 0.20 and not more than 0.50.

  Preferably, in this tire, the thickness A at the inner end in the tire axial direction of the buffer layer is larger than the thickness B at the center.

  Preferably, the thickness of the buffer layer is gradually reduced from the inner end in the tire axial direction to the center. The ratio (B / A) of the central thickness B to the thickness A at the inner end in the tire axial direction is 0.5 or more.

  In the tire according to the present invention, the tread rigidity is improved by the reinforcing layer. Furthermore, it is suppressed by the buffer layer that road surface followability is impaired, and this tire is excellent in grip performance. This tire has both turning performance and turning stability.

FIG. 1 is a cross-sectional view showing a part of a tire according to an embodiment of the present invention. FIG. 2 is a partially enlarged sectional view indicated by an arrow II in FIG. FIG. 3 is an explanatory view showing a part of the reinforcing layer of the tire of FIG. 1. FIG. 4 is a cross-sectional view showing a part of a tire according to another embodiment of the present invention. FIG. 5 is a cross-sectional view showing a buffer layer of the tire of FIG. FIG. 6A is a cross-sectional view illustrating a buffer layer of still another tire according to the present invention, and FIG. 6B is a cross-sectional view illustrating a buffer layer of still another tire according to the present invention. is there.

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

  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. An alternate long and short dash line CL in FIG. 1 represents the equator plane of the tire 2. The tire 2 has a substantially bilaterally symmetrical shape with the equator plane CL as the center. The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a band 12, a reinforcing layer 14, a buffer layer 16, an inner liner 18 and a chafer 20. The tire 2 is attached to a motorcycle.

  The tread 4 is made of a crosslinked tread rubber. This tread rubber is excellent in wear resistance. The tread 4 has a shape protruding outward in the radial direction. The tread 4 includes a tread surface 22. The tread surface 22 is in contact with the road surface. Grooves 24 and 26 are carved on the tread surface 22. The grooves 24 and 26 form a tread pattern. The grooves 24 and 26 may not be cut in the tread 4.

  A double arrow TW in FIG. 1 indicates the half width of the tread from the equator plane CL to the edge of the tread 4. The half width TW is measured along the tread surface 22, and a double-headed arrow TH indicates the thickness of the tread 4. The half width TW and the thickness TH are measured by the cross section shown in FIG.

  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 28 and an apex 30 that extends radially outward from the core 28. The core 28 has a ring shape. The core 28 is formed by winding a non-stretchable wire. Typically, steel wire is used for the core. The apex 30 is tapered outward in the radial direction. The apex 30 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a carcass ply 32. The carcass ply 32 is spanned between the beads 8 on both sides, and extends along the inside of the tread 4 and the sidewall 6. The carcass ply 32 is folded around the core 28 from the inner side to the outer side in the axial direction.

  Although not shown, the carcass ply 32 includes a large number of carcass cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each carcass cord with respect to the equator plane CL is normally 70 ° to 90 °. In other words, the carcass 10 has a radial structure. This carcass 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.

  The band 12 is laminated on the outer side in the radial direction of the carcass. The band 12 covers the outer peripheral surface of the carcass 10. The band 12 reinforces the tread 4. Although not shown, the band 12 is composed of a band cord and a topping rubber. This band cord extends substantially in the circumferential direction and is wound spirally. The band 12 has a so-called jointless structure. This band cord is usually made of organic fibers. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The inner liner 18 is joined to the inner peripheral surface of the carcass 10. The inner liner 18 is made of a crosslinked rubber. For the inner liner 18, rubber having excellent air shielding properties is used. The inner liner 18 plays a role of maintaining the internal pressure of the tire 2. The chafer 20 is located in the vicinity of the bead 8. When the tire 2 is incorporated in the rim, the chafer 20 comes into contact with the rim. By this contact, the vicinity of the bead 8 is protected.

  The pair of buffer layers 16 are positioned with the equatorial plane CL spaced apart from each other in the tire axial direction. The buffer layer 16 is laminated on the outer side in the radial direction of the reinforcing layer 14. The buffer layer 16 is made of a cross-linked buffer rubber. A double arrow X1 in FIG. 1 indicates the distance from the equator plane CL to the inner end of the buffer layer 16 in the tire axial direction. A double-headed arrow X2 indicates the distance from the equatorial plane CL to the outer end of the buffer layer 16 in the tire axial direction. A double-headed arrow DW indicates the width of the buffer layer 16 in the tire axial direction. The width DW is a distance from the axially inner end to the outer end of the buffer layer 16. The distances X1 and X2 and the width DW are measured in the cross section shown in FIG.

  A point P <b> 1 in FIG. 2 indicates an intersection of the perpendicular line drawn from the inner end of the buffer layer 16 to the tread surface 22 and the tread surface 22. A point P <b> 2 indicates the intersection of the perpendicular drawn from the outer end of the buffer layer 16 to the tread surface 22 and the tread surface 22. This distance X1 is measured as the distance from the equator plane CL to the point P1. This distance X2 is measured as the distance from the equator plane CL to the point P2. This width DW is measured as the distance from the point P1 to the point P2. The distances X1 and X2 and the width DW are measured along the tread surface 22. A double arrow DH indicates the thickness of the buffer layer 16.

  The pair of reinforcing layers 14 are stacked on the outer side in the radial direction of the band. The reinforcing layers 14 are positioned with the equator plane CL spaced apart from each other in the tire axial direction. The reinforcing layer 14 includes a number of reinforcing cords 34 and a topping rubber 36.

  A one-dot chain line L1 in FIG. 3 indicates the tire circumferential direction. An alternate long and short dash line L <b> 2 indicates the axis of the reinforcing cord 34. The angle α is an angle formed by the one-dot chain line L1 and the one-dot chain line L2. A double-headed arrow DW indicates the width of the reinforcing layer 14. This width DW is the same as the width DW of the buffer layer 16. A double arrow RH indicates the thickness of the reinforcing layer 14. The reinforcing cord 34 is passed through the center in the thickness direction of the topping rubber 36 of the reinforcing layer 14.

  In the tire 2, the reinforcing layer 14 having a width DW is located from the position of the distance X1 from the equatorial plane CL toward the outside in the axial direction in the tire axial direction. The rigidity of the tread 4 where the reinforcing layer 14 is located is improved. During the turning of the motorcycle, the tread surface 22 where the reinforcing layer 14 is located contacts the ground. Thereby, sufficient camber thrust is obtained. Further, in a large motorcycle, a so-called “crushed” state can be suppressed.

  In general, the tread 4 is easily provided with rigidity by providing the reinforcing layer 14 widely. A large camber thrust can be obtained by turning. On the other hand, when the rigidity of the tread 4 is improved, the road surface followability is easily impaired. For this reason, grip property and riding comfort are liable to be impaired. In the tire 2, the buffer layer 16 is laminated on the outer side in the radial direction of the reinforcing layer 14. In the tire 2, it is suppressed that the road surface followability of the tread 4 is impaired.

  In the tire 2, the ratio (X1 / TW) between the distance X1 and the half width TW of the tread 4 is set to 0.35 or more and 0.50 or less. The ratio (X2 / TW) between the distance X2 and the half width TW of the tread 4 is 0.8 or more and less than 1.0. When the absolute value of the angle α formed by the reinforcing cord of the reinforcing layer 14 with respect to the circumferential direction is 20 ° or more and 45 ° or less, a large camber thrust is obtained. By providing the buffer layer 16, it is suppressed that grip property is impaired. The tire 2 is excellent in turning performance.

  The tire 2 is provided with the buffer layer 16 on the outer side of the reinforcing layer 14, so that the road surface followability is prevented from being impaired. As a result, the tire 2 can easily follow a road surface cap or the like even during turning. The tire is prevented from being shaken by the external force received from the road surface. The tire 2 is excellent in turning stability. In the tire 2, turning stability and turning performance are compatible.

  In the tire 2, since the reinforcing layer 14 and the buffer layer 16 covering the reinforcing layer 14 have the same width DW, the rigidity of the tread 4 is suppressed from changing rapidly in the tire axial direction. The tire 2 is superior in stability at the time of transition between straight traveling and cornering compared to a tire having a conventional reinforcing layer.

  By setting the ratio (X1 / TW) between the distance X1 and the half width TW to be 0.35 or more, the influence on the straight running stability due to the improved rigidity of the tread 4 is suppressed. In the tire 2, the road surface followability is prevented from being impaired by further including the buffer layer 16. By providing this buffer layer 16, in the tire 2, it is suppressed that the riding comfort in the straight traveling is impaired. When this ratio (X1 / TW) is 0.5 or less, turning stability and turning performance are improved.

  By setting the ratio (X2 / TW) of the distance X2 to the half width TW to be 0.8 or more, the functions of turning stability and turning performance during turning can be sufficiently exhibited. In particular, it can contribute to turning stability and turning performance when the bank angle is large. On the other hand, the tire 2 having this ratio (X2 / TW) of 0.9 or less is excellent in productivity. Further, the tire 2 having the ratio (X2 / TW) of 0.9 or less has excellent durability.

  In the buffer layer 16, the ratio of the thickness DH of the buffer layer 16 to the thickness TH of the tread 4 (DH / TH) is preferably 0.20 or more from the viewpoint of road surface followability. More preferably, this ratio (DH / TH) is 0.25 or more. On the other hand, the tire 2 having a small thickness TH of the buffer layer 16 is suppressed from impairing the rigidity of the tread 4. From this viewpoint, the ratio (DH / TH) is preferably 0.50 or less. More preferably, this ratio (DH / TH) is 0.40 or less, and particularly preferably, this ratio (DH / TH) is 0.35 or less.

  Similarly, from the viewpoint of this road surface followability, the complex elastic coefficient (Ed) of the buffer rubber of the buffer layer 16 is preferably smaller than the complex elastic coefficient (Et) of the tread rubber of the tread 4. In this respect, the complex elastic modulus ratio (Ed / Et) is preferably less than 1.0. Further, it is preferably 0.9 or less. On the other hand, the tire 2 having a relatively large ratio (Ed / Et) is suppressed from impairing the rigidity of the tread 4. In this respect, the ratio (Ed / Et) is preferably equal to or greater than 0.7. Furthermore, it is preferably 0.8 or more.

  The tread 4 may be made of a base rubber and a cap rubber laminated on the outer side in the radial direction of the base rubber. Further, here, the tire 2 as a rear tire of the motorcycle has been described as an example. The present invention can be similarly applied to a front tire of a motorcycle.

  FIG. 4 shows a tire 38 according to another embodiment of the present invention. The tire 38 includes a buffer layer 40 instead of the buffer layer 16. The other configuration of the tire 38 is the same as that of the tire 2, and the description thereof is omitted.

  As shown in FIG. 4, in the buffer layer 40, the thickness at the axially inner end and the axially outer end is greater than the thickness at the axial center. A double arrow A in FIG. 5 indicates the thickness of the inner end in the axial direction of the buffer layer 40. A double arrow B indicates the thickness at the center in the axial direction. A double arrow C indicates the thickness of the outer end in the axial direction of the buffer layer 40. In the tire 38, the thickness is gradually reduced from the thickness A to the thickness B from the axially inner end of the buffer layer 40 toward the center. The buffer layer 40 is gradually increased from a thickness B to a thickness C from the axial center to the outer end.

  In the tire 38, the tread surface 22 where the reinforcing layer 14 is not located in the straight traveling is mainly grounded. The tread surface 22 on which the reinforcing layer 14 is located during the turning travel is mainly grounded. When shifting from straight traveling to turning, the tread surface 22 that contacts the tread surface 22 where the reinforcing layer 14 is located moves from the tread surface 22 where the reinforcing layer 14 is not located.

  In the tire 38, the thickness A is increased. Thereby, when the tread surface 22 which contacts the tread surface 22 where the reinforcing layer 14 is located moves from the tread surface 22 where the reinforcing layer 14 is not located, a sudden change in rigidity is suppressed. Thereby, the discomfort experienced by the rider when shifting from straight traveling to turning traveling is reduced.

  Similarly, when the vehicle travels from turning to straight traveling, the rigidity is prevented from changing abruptly. Thereby, the discomfort experienced by the rider when shifting from turning to straight traveling is reduced. The tire 38 is excellent in stability at the time of transition between straight traveling and turning traveling.

  In the tire 38, the thickness A of the inner end in the axial direction of the buffer layer 40 is increased, but the thickness B of the center is not increased. In the tire 38, even if the thickness A is increased, the rigidity of the tread 4 in the portion where the center of the buffer layer 40 is located is suppressed. The tire 38 is excellent in transition stability without impairing the turning performance.

  Further, in the tire 38, the thickness A at the inner end in the axial direction can be set to an appropriate thickness from the viewpoint of stability at the time of transition, and the central thickness B can be set to an appropriate thickness from the viewpoint of turning performance and turning stability. From this point of view, the tire 38 can exhibit an effect of excellent stability at the time of transition without impairing the turning performance and the turning stability.

  In the tire 38, the tread surface 22 on which the inner end in the axial direction of the buffer layer is located is mainly grounded when shifting from straight traveling to turning traveling. When the motorcycle equipped with the tire 38 is further pushed down, the tread surface 22 where the center of the buffer layer in the axial direction is located is mainly grounded. Since the thickness of the buffer layer 40 gradually decreases from the thickness A to the thickness B, a rapid change in the rigidity of the tread 4 is suppressed. The tire 38 is excellent in stability even in a process in which the motorcycle that is turning is pushed down.

  While the motorcycle equipped with the tire 38 is turning, the tread surface 22 on which the reinforcing layer 14 is located is grounded. When the motorcycle is further pushed down to a so-called full bank state, the tread surface 22 on the outer side in the axial direction of the tread 4 is grounded. In the process from further turning down to the so-called full bank running, the portion of the tread surface 22 where the reinforcing layer 14 is located and the tread surface 22 outside the axial direction where the reinforcing layer 14 is not located moves.

  In the tire 38, the thickness C is greater than the thickness B. In the process of being brought down, the rigidity of the tread 4 is prevented from changing abruptly. The discomfort experienced by the rider when shifting from turning to so-called full bank traveling is reduced. Similarly, the discomfort experienced by the rider when shifting from full bank travel to turning travel is reduced. The tire 38 is also excellent in stability at the time of transition between turning and full bank traveling that has not reached full bank traveling.

  FIG. 6A shows a cross section of still another buffer layer 42. A double arrow A in FIG. 6A indicates the thickness of the inner end in the axial direction of the buffer layer 42. A double arrow B indicates the thickness at the center in the axial direction. A double arrow C indicates the thickness of the outer end of the buffer layer 42 in the axial direction. A double-headed arrow D indicates an intermediate thickness between the axial center and the axial outer end. In the buffer layer 42, the thickness A is gradually reduced from the thickness A to the thickness D from the axial inner end toward the middle between the axial center and the axial outer end. The thickness is gradually increased from the thickness D to the thickness C from the middle between the axial center and the axial outer end of the buffer layer 42 toward the axial outer end.

  A tire provided with a buffer layer 42 instead of the buffer layer 40 can exhibit an effect of excellent stability at the time of transition without impairing the turning performance and the turning stability, similarly to the tire 38.

  FIG. 6B shows a cross section of still another buffer layer 44. A double arrow A in FIG. 6B indicates the thickness of the inner end in the axial direction of the buffer layer 44. A double arrow B indicates the thickness at the center in the axial direction. A double arrow C indicates the thickness of the outer end of the buffer layer 44 in the axial direction. In the buffer layer 44, the thickness is gradually decreased from the thickness A to the thickness B from the axially inner end toward the axial center. Thickness B and thickness C are made equal. The thickness is constant from the axial center to the axially outer end.

  A tire including the reinforcing layer 44 instead of the reinforcing layer 40 is excellent in stability at the time of transition between straight traveling and turning traveling. Even in the tire including the reinforcing layer 44, the effect of excellent stability at the time of transition between the straight traveling and the cornering can be exhibited without damaging the cornering performance and cornering stability.

  In the present invention, unless otherwise specified, the dimensions and angles of the members 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 of Example 1 having the basic structure shown in FIG. 1 and having the specifications shown in Table 1 was obtained. The tire size is 180 / 55R17. The carcass ply includes a carcass cord formed by twisting two yarns made of nylon fibers. The fineness of this yarn is 1890 dtex. The density of the carcass cord is 46 / 5cm. The absolute value of the angle formed by the carcass cord with respect to the equator plane is 90 °. This band layer includes a band cord formed by twisting two yarns made of aromatic polyamide fibers. The fineness of this yarn is 1500 dtex. The density of the band cord is 50 / 5cm. This band cord is spirally wound in the circumferential direction. The angle formed by the band cord with respect to the equator plane is substantially 0 °. This reinforcing layer includes a reinforcing cord formed by twisting two yarns made of nylon fibers. The fineness of this yarn is 840 dtex. The density of the reinforcing cord is 28 / 5cm. The absolute value of the angle formed by the reinforcing cord with respect to the circumferential direction is 30 °.

[Comparative Example 1]
A tire of Comparative Example 1 was obtained in the same manner as Example 1 except that the buffer layer was not provided.

[Example 2-4 and Comparative Example 2-4]
As shown in Table 1, tires of Examples 2 to 4 and Comparative Examples 2 to 4 were the same as Example 1 except that the ratio (X1 / TW) and ratio (X2 / TW) were changed. Got.

[Example 5-9]
As shown in Table 2, tires of Examples 5 to 9 were obtained in the same manner as Example 1 except that the thickness of the buffer layer was changed and the thickness ratio (DH / TH) was changed.

[Examples 10-14]
As shown in Table 3, tires of Examples 10 to 14 were obtained in the same manner as in Example 1 except that the complex elastic modulus ratio (Ed / Et) of the buffer layer was changed.

[Evaluation Test 1]
The prototype tires of Examples 1 to 14 and Comparative Examples 1 to 4 were mounted on the rear wheels of a two-wheeled vehicle (4 cycles) having a displacement of 600 cc. The rim was MT5.50 × 17, and the air pressure inside the tire was 290 kPa. A commercial tire is mounted on the front wheel. In the circuit course composed of dry asphalt road, the rider's sensory evaluation was performed on the turning stability, turning limitability and straight running stability. The turning stability is a sensory evaluation of the shake of the vehicle body that occurs when turning over a gap on the road surface during turning. The turning limit property is an evaluation of the height of the limit speed in turning. It can be said that the higher the limit speed, the higher the turning performance. This sensory evaluation was rated at 10 points, and was evaluated by relative evaluation. In this evaluation, the evaluation of the conventional tire of Comparative Example 1 was set to the reference value 5.0, and the relative evaluation of other tires was performed. Larger values indicate better results. The results are shown in Tables 1 to 3 below.

  As shown in Tables 1 to 3, the tires of the examples are highly evaluated for both turning stability and turning performance. Further, the tires of the examples are not impaired in straight running stability. From this evaluation result, the superiority of the present invention is clear.

[Example 15]
A pneumatic tire of Example 15 having the basic structure shown in FIG. 4 and having the specifications shown in Table 4 was obtained. As the thickness DH of the buffer layer of the tire, the thickness A of the inner end in the axial direction of the buffer layer is used. This tire has the same configuration as the tire of Example 1 except that the buffer layer is different.

[Example 16-20]
As shown in Table 4, from Example 16 except that the ratio (B / A) of the thickness A at the inner end in the axial direction of the buffer layer to the thickness B at the center (B / A) was changed. 20 tires were obtained.

[Evaluation Test 2]
The prototype tires of Examples 1 and 15 to 20 were mounted on the rear wheels of the two-wheeled vehicle (four cycles) used in the travel evaluation 1. The air pressure inside the tire was 290 kPa. Like the running evaluation 1, the turning stability, turning limitability, and straight running stability were sensorially evaluated by the rider. Furthermore, the rider's sensory evaluation of the stability at the time of transition between straight running and turning. In this evaluation, the evaluation of the tire of Example 1 was used as a reference value, and the relative evaluation of other tires was performed. Larger values indicate better results. The results are shown in Table 4 below.

  As shown in Table 4, the tires of Examples 15 to 20 were not significantly impaired in turning stability, turning performance, and straight running stability as compared with the tire of Example 1. Furthermore, in the tires of Examples 15 to 20, an excellent effect was confirmed in the stability at the time of transition. From this evaluation result, the superiority of the present invention is clear.

2, 38 ... Tire 4 ... Tread 6 ... Side wall 8 ... Bead 10 ... Carcass 12 ... Band 14 ... Reinforcement layer 16, 40, 42, 44 ... Buffer Layer 18 ... Inner liner 20 ... Chafer 22 ... Tread surface 24, 26 ... Groove 28 ... Core 30 ... Apex 32 ... Carcass ply 34 ... Reinforcement cord 36 ... Topping rubber

Claims (6)

A tread whose outer surface forms a tread surface, a pair of sidewalls, a pair of beads, a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall, A band laminated on the outer side of the carcass in the radial direction, a pair of reinforcing layers laminated on the outer side of the band in the radial direction and spaced apart from each other in the tire axial direction, and the outer side of the reinforcing layer in the radial direction A pair of buffer layers laminated to each other,
This carcass is provided with a large number of carcass cords arranged in parallel, and the absolute value of the angle formed by each carcass cord with respect to the equator plane is 70 ° or more and 90 ° or less,
This band is equipped with a band cord, this band cord is spirally wound in the tire circumferential direction,
The reinforcing layer includes a large number of reinforcing cords, and an absolute value of an angle formed by each reinforcing cord with respect to the tire circumferential direction is 20 ° to 45 °,
This buffer layer is made of a crosslinked buffer rubber and covers the radially outer peripheral surface of the reinforcing layer,
The ratio (X1 / TW) of the distance X1 from the axially inner end of the buffer layer to the equator and the half width TW of the tread is 0.35 or more and 0.50 or less, and from the axially outer end of the buffer layer to the equator A motorcycle tire having a ratio (X2 / TW) of the distance X2 of the tread and the half width TW of the tread of 0.8 or more and less than 1.0. The tread is made of a cross-linked tread rubber,
The tire according to claim 1, wherein a complex elastic coefficient (Ed) of the buffer rubber is smaller than a complex elastic coefficient (Et) of the tread rubber.   The tire according to claim 2, wherein a ratio (Ed / Et) of a complex elastic modulus (Ed) of the buffer rubber to a complex elastic coefficient (Et) of the tread rubber is 0.7 or more and less than 1.0.   The tire according to any one of claims 1 to 3, wherein a ratio (DH / TH) of a thickness DH of the buffer layer to a thickness TH of the tread is 0.20 or more and 0.50 or less.   The tire according to any one of claims 1 to 4, wherein a thickness A of an inner end in the tire axial direction of the buffer layer is larger than a thickness B of the center. The thickness of the buffer layer is gradually reduced from the tire axial direction inner end to the center,
The tire according to claim 5, wherein a ratio (B / A) of a central thickness B to a thickness A of the inner end in the tire axial direction is 0.5 or more.

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