JP4965167B2 - 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 ply is called a cut ply. This belt ply contributes to the grip force of the tire. This tire is excellent in turning performance. However, this tire 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. Such a belt ply is called a jointless belt ply (JLB ply). 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.

Japanese Laid-Open Patent Publication No. 2001-187514 discloses a radial tire for a motorcycle that maintains excellent ride performance when traveling straight and has excellent turning performance. This tire includes a band layer located on the outer side in the radial direction of the carcass and a tread reinforcing layer disposed in the vicinity of the shoulder of the tread. The band layer includes a band cord spirally wound in the circumferential direction. This band layer is the aforementioned JLB ply. The tread reinforcement layer includes a reinforcement cord that is disposed to be inclined with respect to the circumferential direction. This tread reinforcing layer is the aforementioned cut ply. This tire has the advantages of a JLB ply and a cut ply.
JP 2001-187514 A

  In the case of a straight traveling tire, the center of the tread is mainly grounded. When turning, the rider tilts the motorcycle inward. Therefore, when turning (particularly full bank), the tread shoulder is mainly grounded. At the time of transition from straight traveling to turning traveling, the ground contact point transitions from the center to the shoulder. At the time of transition from turning to straight traveling, the ground contact point shifts from the shoulder to the center.

  In the tire of the above publication, the tread reinforcing layer is laminated on the outer side or the inner side of the band layer in the vicinity of the shoulder. Therefore, the characteristics of the tread in the range from the center to the shoulder change abruptly with the inner end positioned on the inner side in the axial direction of the tread reinforcing layer as a boundary. In this tire, the transition from the straight traveling to the turning traveling and the transition from the turning traveling to the straight traveling are not smooth. A rider who drives a vehicle equipped with the tire feels uncomfortable while driving.

  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, and that makes a smooth transition from straight running to turning.

  A pneumatic tire for a motorcycle according to the present invention includes a tread whose outer surface forms a tread surface, a full belt positioned radially inward of the tread, and a pair of edge belts spaced apart in the axial direction. I have. This full belt consists of a first belt ply. The first belt ply includes a first cord that is spirally wound substantially along the circumferential direction. The first belt ply includes a center portion located in the center and a pair of side portions located on both sides of the center portion. The density of the first cord in the side portion is smaller than the density of the first cord in the center portion. The edge belt includes a second belt ply and a third belt ply located on the inner side in the radial direction of the second belt ply. The second belt ply includes a second cord. The absolute value of the angle formed by the second cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °. The second belt ply overlaps the side portion in the axial direction. The third belt ply includes a third cord. The absolute value of the angle formed by the third cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °. The third belt ply overlaps the side portion in the axial direction. The ratio of the axial width of the edge belt to the width of the tread is 15% or more and 40% or less.

  Preferably, in this tire, the ratio of the density of the first cord in the side portion to the density of the first cord in the center portion is not less than 30% and not more than 70%. Preferably, in the tire, the first cord is an aramid fiber. Preferably, in the tire, the second cord and the third cord are aramid fibers. Preferably, in this tire, the density of the first code in the center portion is 20 ends or more and 40 ends or less.

  Since the tire according to the present invention includes the first cord in which the first belt ply of the full belt is substantially spirally wound in the circumferential direction, the tire has excellent straight running stability during high speed running. Edge belts that are spaced apart in the axial direction increase the rigidity of the shoulder and contribute to the grip force during turning. In this tire, sufficient camber thrust is generated during turning. This tire is excellent in turning performance. The first belt ply is configured such that the density of the first cord in the side portion located near the shoulder is smaller than the density of the first cord in the center portion. Thereby, rigidity can be appropriately maintained in the vicinity of the shoulder where the second belt ply and the third belt ply are arranged so as to overlap the side portions in the axial direction. In this tire, the characteristics do not change abruptly between the center of the tread and the shoulder. During traveling, the ground contact portion of the tire can smoothly transition. This tire is excellent in operability.

  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 full belt 12, an edge belt 14, an inner liner 16 and a chafer 18. 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 20 that contacts the road surface. A tread pattern may be formed by grooving the tread surface 20.

  The sidewall 6 extends substantially inward in the radial direction from the end 22 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 extends from the sidewall 6 substantially inward in the radial direction. The bead 8 includes a core 24 and an apex 26 that extends radially outward from the core 24. The core 24 has a ring shape and includes a plurality of non-stretchable wires (typically steel wires). The apex 26 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 28. The carcass ply 28 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 28 is wound around the core 24 from the inner side to the outer side in the axial direction.

  Although not shown, the carcass ply 28 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 16 is joined to the inner peripheral surface of the carcass 10. The inner liner 16 is made of a crosslinked rubber. The inner liner 16 is made of rubber having a low air permeability. 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 18 made of a single rubber may be used.

  The full belt 12 is located inside the tread 4 in the radial direction. The full belt 12 is located on the radially outer side of the carcass 10. The full belt 12 reinforces the carcass 10. The full belt 12 includes a first belt ply 30. The first belt ply 30 includes a center portion 32 located in the center and a pair of side portions 34 located on both sides of the center portion 32. The side portion 34 is located in the vicinity of the shoulder 36 of the tread 4.

  The edge belt 14 is located on the radially outer side of the carcass 10. The edge belt 14 is located in the vicinity of the shoulder 36. The left and right edge belts 14 are spaced apart in the axial direction. The edge belt 14 includes a second belt ply 38 and a third belt ply 40 located on the inner side in the radial direction of the second belt ply 38. In the tire 2, the axial width of the second belt ply 38 is larger than the axial width of the third belt ply 40. The axial width of the second belt ply 38 may be smaller than the axial width of the third belt ply 40.

  The second belt ply 38 is laminated on the outer side in the radial direction of the side portion 34. In other words, the second belt ply 38 overlaps the side portion 34 in the axial direction. The third belt ply 40 is laminated on the inner side in the radial direction of the side portion 34. In other words, the third belt ply 40 overlaps the side portion 34 in the axial direction. In the tire 2, the position of the inner end 42 of the second belt ply 38 matches the position of the inner end 44 of the side portion 34. The inner end 46 of the third belt ply 40 is on the outer side in the axial direction of the inner end 44 of the side portion 34. The inner end 42 of the second belt ply 38 may be disposed outside the inner end 44 of the side portion 34 in the axial direction. The position of the inner end 46 of the third belt ply 40 may coincide with the position of the inner end 44 of the side portion 34 in the axial direction.

  Although not shown, the second belt ply 38 is composed of a second cord and a second topping rubber. The second cord is inclined with respect to the circumferential direction. The absolute value of the angle formed by the second cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °. The third belt ply 40 includes a third cord and a third topping rubber. The third cord is inclined with respect to the circumferential direction. The absolute value of the angle formed by the third cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °. The second belt ply 38 and the third belt ply 40 are so-called “cut plies”. In the tire 2, the angle formed by the second cord with respect to the circumferential direction is opposite to the angle formed by the third cord with respect to the circumferential direction. The angle formed by the second cord in one edge belt 14 with respect to the circumferential direction is opposite to the angle formed by the second cord in the other edge belt 14 with respect to the circumferential direction. In the tire 2, the same cord is used for the second cord and the third cord. The same crosslinked rubber is used for the second topping rubber and the third topping rubber.

  Examples of the second cord and the third cord include nylon fiber, aramid fiber, polyethylene naphthalate fiber, polyester fiber, rayon fiber, glass fiber, and carbon fiber. From the viewpoint of increasing the rigidity of the tire 2 and contributing to the gripping force of the tire 2 and reducing the weight of the tire, the second cord and the third cord are aramid fibers. Is particularly preferred. In the tire 2, aramid fibers are used for the second cord and the third cord.

  FIG. 2 is an enlarged exploded perspective view showing a part of the first belt ply 30 of the tire 2 of FIG. In FIG. 2, an arrow line A represents the circumferential direction of the tire 2. The first belt ply 30 includes a first cord 48 and a first topping rubber 50. The first cord 48 is spirally wound substantially along the circumferential direction. The absolute value of the angle formed by the first cord 48 with respect to the circumferential direction 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 circumferential direction is 5.0 ° or less is the “substantially circumferential direction”. The structure of the first cord 48 is referred to as a jointless structure. The first belt ply 30 is a so-called “jointless belt ply (JLB ply)”. Examples of the first cord 48 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. In this respect, the first cord 48 is particularly preferably an aramid fiber and steel. From the viewpoint of weight reduction of the tire mass, the first cord 48 is particularly preferably an aramid fiber. In the tire 2, an aramid fiber is used for the first cord 48.

  As shown in FIG. 2, in the tire 2, the interval between the first cords 48 in the side portion 34 is wider than the interval between the first cords 48 in the center portion 32. Therefore, the number of first cords 48 that exist per unit width of the side portion 34 is smaller than the number of first cords 48 that exist per unit width of the center portion 32. In other words, in the tire 2, the density of the first cord 48 in the side portion 34 is smaller than the density of the first cord 48 in the center portion 32. Therefore, in the first belt ply 30, the rigidity of the side portion 34 is lower than the rigidity of the center portion 32. In the present specification, the number of the first cords 48 per 5 cm width in the cross section perpendicular to the longitudinal direction of the first cords 48 is expressed as the density (ends) of the first cords 48.

  In the tire 2, the center 52 of the tread 4 is mainly grounded when traveling straight. The center 52 is provided with a first cord 48 spirally wound substantially along the circumferential direction. The first cord 48 restrains the carcass 10. The tire 2 is excellent in straight running stability during high speed running.

  When turning, the rider tilts the motorcycle inward. Therefore, the shoulder 36 of the tread 4 is mainly grounded during turning (particularly full bank). As described above, the edge belt 14 is disposed in the vicinity of the shoulder 36. The edge belt 14 includes a second cord and a third cord that are disposed to be inclined with respect to the circumferential direction. The edge belt 14 increases the rigidity of the shoulder 36 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.

  At the time of transition from straight traveling to turning traveling, the ground contact point transitions from the center 52 to the shoulder 36. As described above, in the tire 2, the density of the first cord 48 in the side portion 34 is smaller than the density of the first cord 48 in the center portion 32. Accordingly, the rigidity can be appropriately maintained in the vicinity of the shoulder 36 in which the second belt ply 38 and the third belt ply 40 are arranged so as to overlap the side portions 34 in the axial direction. In the tire 2, the characteristics do not change abruptly in the range from the center 52 of the tread 4 to the shoulder 36. In such a tire 2, the ground contact point can smoothly transition during the transition from the straight traveling to the turning traveling. In the tire 2, the ground contact point can smoothly transition even when transitioning from turning to straight traveling. The tire 2 is excellent in operability.

  In the tire 2, the ratio (DS / DC × 100) of the density DS of the first cord 48 in the side portion 34 to the density DC of the first cord 48 in the center portion 32 is 30% or more and 70% or less. preferable. By setting this ratio to 30% or more, the rigidity of the side portion 34 can be appropriately maintained. In the tire 2, the edge belt 14 can effectively contribute to the grip force at the time of turning. The tire 2 is excellent in turning performance. In this respect, the ratio is more preferably equal to or greater than 40%, and particularly preferably equal to or greater than 50%. By setting this ratio to 70% or less, excessive rigidity of the side portion 34 can be suppressed. The rigidity of the shoulder 36 can be appropriately maintained. In the tire 2, the characteristics do not change abruptly in the range from the center 52 of the tread 4 to the shoulder 36. 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 this respect, the ratio is more preferably equal to or less than 65%, and particularly preferably equal to or less than 60%.

  In the tire 2, the density DC of the first cord 48 in the center portion 32 is preferably 20 ends or more and 40 ends or less. By setting the density DC to 20 ends or more, the rigidity of the center portion 32 is appropriately increased. The center portion 32 effectively restrains the carcass 10. The tire 2 is excellent in straight running stability during high speed running. In this respect, the density DC is more preferably 25 ends or more, and particularly preferably 30 ends or more. By setting the density DC to 40 ends or less, excessive rigidity of the tire 2 can be suppressed. In the tire 2, riding comfort can be maintained. In this respect, the density DC is more preferably 38 ends or less, and particularly preferably 35 ends or less.

  In the tire 2, it is preferable that the fineness of the first cord 48 is 440 dtex / 2 or more from the viewpoint of contribution to straight running stability during high speed running. From the viewpoint of suppressing excessive rigidity of the tire 2, the fineness of the first cord 48 is preferably 1100 dtex / 2 or less.

  In FIG. 1, a double arrow line WT is an axial distance between the ends 22 of the tread 4 located on the left and right. This axial distance WT is the width of the tread 4. A double arrow line WE is an axial width of the edge belt 14. In this tire 2, the inner end 42 of the second belt ply 38 that is closest to the tire 2 equatorial plane in the axial direction and the outer side of the second belt ply 38 that is closest to the end 22 of the tread 4 in the axial direction. This axial width WE is obtained by measuring the axial distance from the end 54.

  In the tire 2, the ratio (WE / WT × 100) of the axial width WE of the edge belt 14 to the width WT of the tread 4 is 15% or more and 40% or less. By setting this ratio to 15% or more, the edge belt 14 can effectively contribute to the grip force during turning. The tire 2 is excellent in turning performance. In this respect, the ratio is more preferably 19% or more and particularly preferably 23% or more. By setting this ratio to 40% or less, 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 less than 35%, and particularly preferably equal to or less than 30%.

  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.

  FIG. 3 is a cross-sectional view showing a part of a pneumatic tire 56 according to another embodiment of the present invention. In FIG. 3, the vertical direction is the radial direction of the tire 56, the horizontal direction is the axial direction of the tire 56, and the direction perpendicular to the paper surface is the circumferential direction of the tire 56. The tire 56 has a substantially bilaterally symmetric shape with the one-dot chain line CL in FIG. 3 as the center. This alternate long and short dash line CL represents the equator plane of the tire 56. The tire 56 includes a tread 58, a sidewall 60, a bead 62, a carcass 64, a full belt 66, an edge belt 68, an inner liner 70, and a chafer 72. The tire 56 is the same as the tire 2 in FIG. 1 except for the configuration of the full belt 66 and the edge belt 68. The tire 56 is a tubeless type pneumatic tire.

  The full belt 66 is located inside the tread 58 in the radial direction. The full belt 66 is located outside the carcass 64 in the radial direction. The full belt 66 reinforces the carcass 64. The full belt 66 includes a first belt ply 74. Although not shown, the first belt ply 74 includes a first cord and a first topping rubber. The first cord is spirally wound along the circumferential direction. The absolute value of the angle formed by the first cord with respect to the circumferential direction is 5 ° or less, particularly 2 ° or less. This structure of the first cord is referred to as a jointless structure. The first belt ply 74 is a so-called “jointless belt ply (JLB ply)”. In the tire 56, the first cord is an aramid fiber.

  In the tire 56, the first belt ply 74 includes a center portion 76 located in the center and a pair of side portions 78 located on both sides of the center portion 76. The side portion 78 is located in the vicinity of the shoulder 80 of the tread 58. Although not shown, the density of the first cord in the side portion 78 is smaller than the density of the first cord in the center portion 76. In the first belt ply 74, the rigidity of the side portion 78 is lower than the rigidity of the center portion 76.

  The edge belt 68 is located on the radially outer side of the carcass 64. The edge belt 68 is located inside the full belt 66 in the radial direction. The edge belt 68 is located in the vicinity of the shoulder 80. The left and right edge belts 68 are spaced apart in the axial direction. The edge belt 68 may be located on the radially outer side of the full belt 66.

  The edge belt 68 includes a second belt ply 82 and a third belt ply 84. Although not shown, the second belt ply 82 is composed of a second cord and a second topping rubber. The second cord is inclined with respect to the circumferential direction. The absolute value of the angle formed by the second cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °. The third belt ply 84 includes a third cord and a third topping rubber. The third cord is inclined with respect to the circumferential direction. The absolute value of the angle formed by the third cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °. The second belt ply 82 and the third belt ply 84 are so-called “cut plies”. In the tire 56, the angle formed by the second cord with respect to the circumferential direction is opposite to the angle formed by the third cord with respect to the circumferential direction. The angle formed by the second cord in one edge belt 68 with respect to the circumferential direction is opposite to the angle formed by the second cord in the other edge belt 68 with respect to the circumferential direction. In the tire 56, aramid fibers are used for the second cord and the third cord.

  In the tire 56, the second belt ply 82 is laminated on the radially inner side of the side portion 78 of the first belt ply 74. In other words, the second belt ply 82 overlaps the side portion 78 in the axial direction. The third belt ply 84 is laminated on the inner side in the radial direction of the second belt ply 82. Accordingly, the third belt ply 84 also overlaps the side portion 78 in the axial direction. In the tire 56, the inner end 86 of the second belt ply 82 coincides with the inner end 88 of the side portion 78 in the axial direction. The inner end 86 of the second belt ply 82 may be disposed on the outer side in the axial direction of the inner end 88 of the side portion 78.

  In the tire 56, the center 90 of the tread 58 is mainly grounded when traveling straight. The center 90 is provided with a first cord 48 spirally wound substantially along the circumferential direction. This first cord restrains the carcass 64. The tire 56 is excellent in straight running stability during high speed running.

  When turning, the rider tilts the motorcycle inward. Therefore, the shoulder 80 of the tread 58 is mainly grounded during turning (particularly full bank). As described above, the edge belt 68 is disposed in the vicinity of the shoulder 80. The edge belt 68 includes a second cord and a third cord that are disposed to be inclined with respect to the circumferential direction. The edge belt 68 increases the rigidity of the shoulder 80 of the tire 56 and contributes to the grip force during turning. In the tire 56, sufficient camber thrust is generated during turning. The tire 56 is excellent in turning performance.

  At the time of transition from straight traveling to turning traveling, the ground contact point transitions from the center 90 to the shoulder 80. As described above, in the tire 56, the density of the first cord in the side portion 78 is smaller than the density of the first cord in the center portion 76. Thus, the rigidity can be appropriately maintained in the vicinity of the shoulder 80 in which the second belt ply 82 and the third belt ply 84 are arranged so as to overlap the side portions 78 in the axial direction. For this reason, in the range from the center 90 to the shoulder 80 of the tread 58, the characteristics do not change abruptly. In such a tire 56, the ground contact point can smoothly transition during the transition from the straight traveling to the turning traveling. The tire 56 can smoothly transition to the ground contact point even when transitioning from turning to straight traveling. The tire 56 is excellent in operability.

  In the tire 56, the ratio (DS / DC × 100) of the density DS of the first cord in the side portion 78 to the density DC of the first cord in the center portion 76 is preferably 30% or more and 70% or less. From the viewpoint of obtaining good turning performance, this ratio is more preferably 40% or more, and particularly preferably 50% or more. In the range from the center 90 to the shoulder 80 of the tread 58, the tire 56 in which a rapid change in characteristics is suppressed is excellent in operability. This ratio is more preferably 65% or less, and particularly preferably 60% or less.

  In the tire 56, the density DC of the first cord of the center portion 76 is preferably 20 ends or more and 40 ends or less. This density DC is more preferably 25 ends or more, and particularly preferably 30 ends or more, from the viewpoint that good straight running stability can be obtained during high-speed traveling. From the viewpoint that the riding comfort of the tire 56 can be maintained, the density DC is more preferably 38 ends or less, and particularly preferably 35 ends or less.

  In FIG. 3, a double arrow line WT is an axial distance between the ends 92 of the tread 58 located on the left and right. This axial distance WT is the width of the tread 58. A double arrow line WE is an axial width of the edge belt 68.

  In the tire 56, the ratio (WE / WT × 100) of the axial width WE of the edge belt 68 to the width WT of the tread 58 is 15% or more and 40% or less. By setting this ratio to 15% or more, the edge belt 68 can effectively contribute to the grip force during turning. The tire 56 is excellent in turning performance. In this respect, the ratio is more preferably 19% or more and particularly preferably 23% or more. By setting this ratio to 40% or less, excessive rigidity of the tire 56 is suppressed. In the tire 56, riding comfort can be maintained. In this respect, the ratio is more preferably equal to or less than 35%, and particularly preferably equal to or less than 30%.

  In the tire 56, the fineness of the first cord 48 is preferably 440 dtex / 2 or more from the viewpoint of contribution to straight running stability during high-speed running. From the viewpoint of suppressing excessive rigidity of the tire 56, the fineness of the first cord 48 is preferably 1100 dtex / 2 or less.

  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. In this tire, the side portion of the first belt ply is sandwiched between the second belt ply and the third belt ply. The fineness of the first cord used in the center portion of the first belt ply is 1100 dtex / 2. The angle formed by the first cord with respect to the circumferential direction is substantially 0 °. The fineness of the second cord used for the second belt ply is 1100 dtex / 2. The fineness of the third cord used for the third belt ply is 1100 dtex / 2. The absolute value of the angle formed by the second cord and the third cord with respect to the circumferential direction is 40 °. The ratio (WE / WT × 100) of the axial width WE of the edge belt to the width WT of the tread is 23%. The density DC of the first code in the center portion is 30 ends. The density DS of the first cord in the side portion is 15 ends. Therefore, the ratio (DS / DC × 100) of the density DS of the first cord in the side portion to the density DC of the first cord in the center portion is 50%.

[Comparative Examples 1 and 2 and Examples 4 and 5]
A tire was obtained in the same manner as in Example 1 except that the ratio (WE / WT × 100) was as shown in Table 1 below.

[Comparative Example 3 and Examples 2, 3, 6 and 7]
The tire was the same as in Example 1 except that the ratio (DS / DC × 100) was changed by changing the density DS of the first cord in the side portion while keeping the density DC of the first cord in the center portion constant. Got.

[Example 8]
A pneumatic tire for a motorcycle of Example 8 having the basic configuration shown in FIG. 3 and having the specifications shown in Table 1 below was obtained. The tire size is 185 / 55ZR17. In this tire, the second belt ply of the edge belt is laminated on the radially inner side of the side portion of the first belt. A third belt ply is laminated on the inner side in the radial direction of the second belt ply. The fineness of the first cord used in the center portion of the first belt ply is 1100 dtex / 2. The angle formed by the first cord with respect to the circumferential direction is substantially 0 °. The fineness of the second cord used for the second belt ply is 1100 dtex / 2. The fineness of the third cord used for the third belt ply is 1100 dtex / 2. The absolute value of the angle formed by the second cord and the third cord with respect to the circumferential direction is 40 °. The ratio (WE / WT × 100) of the axial width WE of the edge belt to the width WT of the tread is 23%. The density DC of the first code in the center portion is 30 ends. The density DS of the first cord in the side portion is 15 ends. Therefore, the ratio (DS / DC × 100) of the density DS of the first cord in the side portion to the density DC of the first cord in the center portion is 50%.

[Comparative Example 4]
Comparative Example 4 is a conventional tire that is commercially available. 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 5]
Comparative Example 5 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 speed of the vehicle (about 280 km / h) from 250 km / h, straight running stability, grip force during turning, and smoothness during transition Sex was evaluated. The results are shown in Table 1 below. The straight running stability and the grip force at the time of turning are represented by index values. A larger index value indicates better performance. As for the smoothness at the time of transition, the case where the smoothness is excellent is indicated as A, the case where it is inferior is indicated as C, and the space between the two is indicated as B.

  As shown in Table 1, the tires of the examples are excellent in straight running stability and turning performance, and the transition from straight running to turning is smooth. 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. FIG. 2 is an enlarged exploded perspective view showing a part of the first belt ply of the tire of FIG. 1. FIG. 3 is a cross-sectional view showing a part of a pneumatic tire according to another embodiment of the present invention.

Explanation of symbols

2, 56 ... Tire 4, 58 ... Tread 6, 60 ... Sidewall 8, 62 ... Bead 10, 64 ... Carcass 12, 66 ... Full belt 14, 68 ... Edge belt 16, 70 ... Inner liner 18, 72 ... Chafer 20 ... Tread surface 22, 92 ... End 24 ... Core 26 ... Apex 28 ... Carcass ply 30, 74: First belt ply 32, 76: Center part 34, 78 ... Side part 36, 80 ... Shoulder 38, 82 ... Second belt ply 40, 84 ... Third belt Ply 42, 44, 46, 86, 88 ... Inner end 48 ... First cord 50 ... First topping rubber 52, 90 ... Center 54 ... Outer end

Claims (5)

A tread whose outer surface forms a tread surface, a full belt located inside the tread in the radial direction, and a pair of edge belts spaced apart in the axial direction;
This full belt consists of the first belt ply,
The first belt ply includes a first cord spirally wound substantially along the circumferential direction,
The first belt ply is composed of a center portion located in the center and a pair of side portions located on both sides of the center portion,
The density of the first cord in the side portion is smaller than the density of the first cord in the center portion,
The edge belt includes a second belt ply and a third belt ply located radially inward of the second belt ply,
This second belt ply has a second cord,
The absolute value of the angle formed by the second cord with respect to the circumferential direction is 10 ° or more and 80 ° or less,
This second belt ply overlaps this side part in the axial direction,
This third belt ply has a third cord,
The absolute value of the angle formed by the third cord with respect to the circumferential direction is not less than 10 ° and not more than 80 °, and the third belt ply overlaps with the side portion in the axial direction,
A pneumatic tire for a motorcycle, wherein a ratio of an axial width of the edge belt to a width of the tread is 15% or more and 23 % or less.   The tire according to claim 1, wherein the ratio of the density of the first cord in the side portion to the density of the first cord in the center portion is 30% or more and 70% or less.   The tire according to claim 1 or 2, wherein the first cord is an aramid fiber.   The tire according to any one of claims 1 to 3, wherein the second cord and the third cord are aramid fibers.   The tire according to any one of claims 1 to 4, wherein the density of the first code in the center portion is 20 ends or more and 40 ends or less.

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