JP4583944B2 - Motorcycle tires - Google Patents

Description

  The present invention relates to a motorcycle tire.

  A radial tire including a belt in which a belt cord is spirally wound at an angle of 5 ° or less with respect to the equator plane is used in a motorcycle. This belt structure is called a jointless structure. By adopting this jointless structure, the stability and durability of a motorcycle when traveling at high speed are improved.

  As the performance of vehicles progresses, there is a need to improve the limit performance of tires. In particular, since the vehicle is held stably under high speed and high load during turning, further improvement in tire rigidity is achieved. Tires are made of various materials including rubber and cords. In order to improve tire rigidity, studies are being made on increasing the rigidity of the rubber member, increasing the number of various plies in which the cord is embedded in the topping rubber, increasing the rigidity of the cord itself, and the like. All of these cause an increase in tire mass.

  Japanese Patent Laid-Open No. 8-52737 discloses a method for manufacturing a radial tire for a motorcycle, in which a tire with increased tire rigidity and improved handling stability can be manufactured without increasing the tire mass. In the mold used in the vulcanization process included in this tire manufacturing method, the axial distance between the bead heels provided in the left and right beads is 1.10 times to 1.30 times wider than the normal rim width in which the tire is incorporated. Is set to

  Organic fibers such as nylon and polyester are widely used for cords used as constituent members of tires. Since the tire immediately after vulcanization is in a high temperature state, if the tire using such a cord is left as it is, the tire may be deformed.

Japanese Patent Laid-Open No. 5-139105 discloses a PCI (Post Cure Inflation) rim that can cool a tire immediately after vulcanization without deformation, and can suppress a gap amount between the tire and the rim when the rim is assembled. . The tire immediately after vulcanization is cooled in a state where it is incorporated in this PCI rim and filled with air.
JP-A-8-52737 JP-A-5-139105

  As described above, when the tire is vulcanized with a mold in which the axial distance between the bead heels is set to be wider than the normal rim width in which the tire is incorporated, the tire mass is not increased. Tire stiffness is improved. When this tire is assembled in a regular rim and filled with air, the shoulder height of the tire is lowered. When the height of the shoulder is lowered, a compressive force acts on the shoulder of the tire. In addition, since the tension of the belt cord is also reduced, this tire is inferior in steering stability during turning.

  An object of the present invention is to provide a motorcycle tire having improved steering stability during turning without increasing the tire mass.

  The motorcycle tire according to the present invention has a tread whose outer surface forms a tread surface, a pair of sidewalls extending substantially inward in the radial direction from the end of the tread, and further extending substantially inward in the radial direction from the sidewall. A pair of beads, a carcass spanned between both beads along the inside of the tread and the sidewall, and a belt laminated with the carcass on the radially inner side of the tread are provided. The carcass includes a carcass ply. The carcass ply includes a carcass cord. The absolute value of the angle formed by the carcass cord with respect to the tire equatorial plane is 70 ° or more and 90 ° or less. The belt includes a first belt ply at the center and a pair of second belt plies on both sides of the first belt ply. The first belt ply and the second belt ply are adjacent to each other in the tire axial direction. The length of the tread surface to which the left and right tread ends are connected is the circumferential length LT, and the ratio of the circumferential length L2 of the second belt ply to half of the circumferential length LT is 10% or more and 40% or less. The first belt ply includes a first belt-like ply spirally wound in the tire circumferential direction. The first belt-like ply includes a first belt cord and a first topping rubber. The absolute value of the angle formed with respect to the equator plane of the first belt cord is 5 ° or less. This first belt cord is non-heat-shrinkable. The second belt ply includes a second belt-like ply that is spirally wound in the tire circumferential direction. The second belt-like ply includes a second belt cord and a second topping rubber. The absolute value of the angle formed with respect to the equator plane of the second belt cord is 5 ° or less. This second belt cord is heat-shrinkable.

  Preferably, in the tire, the thermal contraction of the second belt cord is optimized by filling the tire in a high temperature state after vulcanization molding with air and cooling the tire.

  Preferably, the tire uses a PCI rim for the cooling. This PCI rim includes a bead fitting portion. The bead fitting portion includes a bead heel contact portion. The ratio of the axial distance between the left and right bead heel contact portions with respect to the regular rim width is 95% or more and 105% or less.

  Preferably, the tire includes a bead ring on which an outer surface of the bead is formed, the bead ring includes a bead heel forming portion, and a ratio of an axial distance between the left and right bead heel forming portions with respect to a normal rim width. Is vulcanized by a mold of 105% or more and 120% or less.

  The motorcycle tire has excellent handling stability during turning because the belt cord tension at the shoulder of the tire is increased without increasing the tire mass.

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

  FIG. 1 is a sectional view showing a part of a pneumatic tire 2 according to an embodiment of the present invention together with a rim 4. 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 6, a sidewall 8, a bead 10, a carcass 12, a belt 14, and an inner liner 16. In FIG. 1, an arrow line WR represents a normal rim width. The tire 2 is a tubeless type pneumatic tire 2.

  The tread 6 is made of a crosslinked rubber and has a shape protruding outward in the radial direction. The tread 6 forms a tread surface 18 that contacts the road surface. A groove 20 is carved in the tread surface 18. The groove 20 forms a tread pattern. In the tread 6, the vicinity of the tread end 22 is a shoulder.

  The sidewall 8 extends from the tread end 22 substantially inward in the radial direction. The sidewall 8 is made of a crosslinked rubber. The sidewall 8 absorbs an impact from the road surface by bending. Further, the sidewall 8 prevents the carcass 12 from being damaged.

  The bead 10 extends from the sidewall 8 substantially inward in the radial direction. The bead 10 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. In FIG. 1, a point BH represents a bead heel.

  The carcass 12 includes a carcass ply 28. The carcass ply 28 is spanned between the beads 10 on both sides, and extends along the inside of the tread 6 and the sidewall 8. The carcass ply 28 is wound around the core 24 from the inner side toward 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 70 ° 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 belt 14 is located on the radially outer side of the carcass 12. The belt 14 is laminated with the carcass 12. The belt 14 reinforces the carcass 12. The belt 14 includes a first belt ply 30 at the center and a pair of second belt plies 32 on both sides thereof. The first belt ply 30 and the second belt ply 32 are adjacent to each other in the tire axial direction.

The first belt ply 30 is obtained by winding the first belt-shaped ply in a spiral shape in the tire circumferential direction. The first belt-like ply includes one or a plurality of first belt cords extending in the longitudinal direction and a first topping rubber. The first belt cord extends substantially in the circumferential direction. The absolute value of the angle formed with respect to the equator plane of the first belt cord is 5 ° or less. This first belt cord has a so-called jointless structure. This first belt cord is non-heat-shrinkable. Preferred materials for the first belt cord are aramid fiber, carbon fiber and steel. From the viewpoint of a decrease in running performance due to an increase in tire mass, the material of the first belt cord is more preferably an aramid fiber and a carbon fiber. More preferably, it is an aramid fiber. In the present specification, non-heat-shrinkage means heating from 20 ° C. to 150 ° C. at a heating rate of 10 ° C./min, holding at this temperature for 10 minutes, and then 150 ° C. at a cooling rate of 10 ° C./min. This shows that the dimensional change rate of the cord when cooled to 20 ° C. is less than 1%. Here, the dimensional change rate of the cord is expressed by ((L ₀ −L) / L ₀ · 100) when the cord length before heating is L ₀ and the cord length after cooling is L. The

  The second belt ply 32 is obtained by winding the second belt-like ply in a spiral shape in the tire circumferential direction. The second belt-like ply includes one or more second belt cords extending in the longitudinal direction and a second topping rubber. The second belt cord extends substantially in the circumferential direction. The absolute value of the angle formed with respect to the equator plane of the second belt cord is 5 ° or less. This second belt cord also has a so-called jointless structure. This second belt cord is a heat-shrinkable wire. The material of the second belt cord is different from the material of the first belt cord. Preferable materials for the second belt cord include nylon fiber, polyester fiber, rayon fiber and polyethylene naphthalate fiber. In addition, a composite fiber in which two or more kinds of fibers are combined, such as a combination of an aramid fiber and a nylon fiber, may be used. Further, a rubber composition having the same composition may be used for the first topping rubber and the second topping rubber. In the present specification, the term “heat shrinkability” means that the dimensional change rate of the cord described above is 1% or more.

  The inner liner 16 is joined to the inner peripheral surface of the carcass 12. 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.

  In order to obtain the motorcycle tire 2, first, a raw cover is formed in a preliminary forming step. This raw cover consists of various uncrosslinked rubber compositions and various cords. The raw cover is a tire molded body before vulcanization molding and is also called a green tire.

  Next, in the vulcanization process, the raw cover is pressurized and heated. In this step, first, the raw cover is put into the mold 34. The raw cover is pressed by the cavity surface of the mold 34 and the bladder. The raw cover is heated at the same time. By this pressurization and heating, the rubber composition of the raw cover flows. Furthermore, the rubber composition of the raw cover causes a crosslinking reaction by heating. The rubber composition of the raw cover is completely cross-linked and the tire 2 is formed. Thereafter, the tire 2 is taken out from the mold 34 and incorporated into the PCI rim 46. Next, the tire 2 is filled with air and cooled in this state, whereby the tire 2 shown in FIG. 1 is obtained.

  FIG. 2 is a cross-sectional view showing a part of a mold 34 used in a vulcanization process included in the method for manufacturing the tire 2 of FIG. In FIG. 2, the vertical direction is the same as the radial direction of the tire 2, the horizontal direction is the same as the axial direction of the tire 2, and the direction perpendicular to the paper surface is the same as the circumferential direction of the tire 2. This alternate long and short dash line LL is a tire equatorial plane equivalent line. This mold 34 is attached to a vulcanizer. The right side of the tire equatorial plane equivalent line LL is the upper side of the vulcanizer. The left side of the tire equator equivalent line LL is the lower side of the vulcanizer. The mold 34 includes a tread segment 36 where the outer surface of the tread 6 is formed, an upper mold side mold 38 and a lower mold side mold 40 where the outer surface of the sidewall 8 is formed, and an upper bead where the outer surface of the bead 10 is formed. A ring 42 and a lower bead ring 44 are provided. This mold 34 is a split mold. Note that a two-piece mold may be used as the mold 34.

  The upper bead ring 42 includes a bead heel forming portion P1, and the lower bead ring 44 includes a bead heel forming portion P2. A double arrow line WP represents an axial distance between the bead heel forming portions P1 and P2. The ratio of the axial distance WP to the normal rim width WR is 105% or more and 120% or less. By setting this ratio to 105% or more, the shape in the vicinity of the tread end 22 changes particularly in the tire 2 after the rim assembly. As the carcass cord is stretched along with this shape change, the tension of the cord increases. Also in the rubber member, the internal stress increases with this shape change. Therefore, in the tire 2 incorporated in the regular rim 4, the tire rigidity is improved. The tire 2 with improved tire rigidity is excellent in handling stability. From this viewpoint, the ratio is more preferably 110% or more. By setting this ratio to 120% or less, excessive tire rigidity can be prevented. In addition, it is possible to prevent the tire 2 from being incorporated into the rim 4. From this viewpoint, the ratio is more preferably 115% or less.

  FIG. 3 is a cross-sectional view showing a state in which the tire 2 of FIG. 1 is incorporated in the PCI rim 46. FIG. 4 is a partially enlarged cross-sectional view in which a part of the tire 2 of FIG. 3 is enlarged. The PCI rim 46 is provided with a bead fitting portion 48. The bead fitting portion 48 includes a bead heel contact portion P3. 4 represents the shape of the tire 2 from the shoulder in the free state before being incorporated into the PCI rim 46 after the vulcanization process to the bead 10 through the tread end 22. The arrow line WB represents the axial distance between the bead heels BH on the left and right of the tire 2 in this free state. In the present specification, the free state means a state where the tire 2 is not incorporated in the rim 4.

  The second belt cord used in the tire 2 is heat shrinkable. The tire 2 that has been vulcanized and released from the mold 34 is in a high temperature state. When the tire 2 in the high temperature state is cooled as it is, the tire 2 is deformed because the second belt cord contracts. Therefore, the tire 2 in a high temperature state after the vulcanization process is attached to the PCI rim 46. The tire 2 mounted on the PCI rim 46 is filled with air in the range of 90% to 100% of the standard internal pressure. In this state, the tire 2 is cooled. Since the tire 2 is cooled by being filled with air, the second belt cord is given appropriate heat shrinkage. Since the tension of the second belt cord is moderately increased by the thermal contraction action, the rigidity of the shoulder on which the second belt cord is disposed is also appropriately increased. The tire 2 with moderately increased rigidity at the shoulder is excellent in steering stability during turning. Since excessive deformation is prevented in the tire 2 that has undergone this cooling step, the tire 2 is also excellent in dimensional stability.

  In FIG. 1, the arrow line LT represents the length of the tread surface 18 to which the left and right tread ends 22 are connected. The arrow line L1 represents the circumferential length of the first belt ply 30. A double arrow line L2 represents the circumferential length of the second belt ply 32.

  The ratio of the circumferential length L2 to half of the circumferential length LT is 10% or more and 40% or less. By setting this ratio to 10% or more, the ratio of the second belt ply 32 to the belt 14 increases. As described above, since the tension of the second belt cord provided in the second belt ply 32 is increased by the thermal contraction action, the rigidity at the shoulder where the second belt ply 32 is arranged is appropriately improved. Such a tire 2 is excellent in steering stability during turning. From this viewpoint, the ratio is more preferably 15% or more, and particularly preferably 20% or more. By setting this ratio to 40% or less, the rigidity of the tread 6 in the axial direction is optimized, so that the steering stability is excellent both when the vehicle goes straight and when it turns. In this respect, the ratio is more preferably equal to or less than 30%.

  The ratio of the circumferential length L1 to the circumferential length LT is preferably 60% or more and 90% or less. By setting this ratio to 60% or more, the ratio of the first belt ply 30 disposed in the center of the belt 14 to the belt 14 increases. Since the elastic modulus of the first belt cord is higher than that of the second belt cord, a region where the tread rigidity is moderately increased expands outward in the axial direction. Such a tire 2 is excellent in steering stability during straight traveling. In this respect, the ratio is more preferably equal to or greater than 70%. By setting this ratio to 90% or less, the tire 2 bends appropriately during turning. Such a tire 2 is excellent in steering stability during turning. In this respect, the ratio is more preferably equal to or less than 85%, and particularly preferably equal to or less than 80%.

  In FIG. 3, a double arrow line WQ represents an axial distance between the left and right bead heel contact portions P3. The ratio of the axial distance WQ to the normal rim width WR is 95% or more and 105% or less. This axial distance WQ is equal to the regular rim width WR. As described above, the tire 2 is formed of the mold 34 in which the axial distance WP between the bead heel forming portions P1 and P2 is larger than the normal rim width WR. Therefore, when the tire 2 is incorporated in the PCI rim 46, the curvature of the tread 6 particularly at the shoulder is reduced. When the curvature of the tread 6 is reduced, the reinforcing effect of the carcass 12 by the belt 14 spirally wound in the circumferential direction on the radially outer side of the carcass 12 is reduced. However, in the tire 2, the heat-shrinkable second belt cord is disposed in the shoulder region where the curvature of the tread 6 is reduced. As described above, since the inside of the tire 2 is filled with air, the second belt cord of the tire 2 attached to the PCI rim 46 is in a state in which excessive heat shrinkage is suppressed. The second belt cord in this state is thermally contracted in accordance with the degree of curvature reduction of the tread 6. Therefore, in the tire 2, even if the curvature of the tread 6 decreases after the rim assembly, the reinforcing effect of the carcass 12 by the belt 14 is maintained.

  Further, when the tire 2 cooled by the PCI rim 46 is incorporated into the regular rim 4, the axial distance WQ between the bead heel contact portions P3 of the PCI rim 46 and the regular rim width WR are equal. There is no gap between the bead 10 and the rim 4. Therefore, both fit well. In the tire 2 in which the bead 10 is fitted to the rim 4 well, vibration during traveling can be prevented.

  The size and angle of each part of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim 4 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 regular rim 4 means the rim 4 defined in the standard on which the tire 2 relies. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims 4. 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 motorcycle tire having the basic configuration shown in FIG. 1 and having the specifications shown in Table 1 was obtained. The tire size is 190 / 50ZR17. One carcass ply was used for the carcass. The cord material used for the carcass ply is nylon fiber. The angle formed with respect to the circumferential direction of this cord is 90 °. The fineness of this cord is 1400 dtex / 2. The density of this cord is 40 ends. As the belt, a first belt ply and a second belt ply were used. The cord material used for the first belt ply is aramid fiber. The angle formed with respect to the circumferential direction of this cord is 0 °. The fineness of this cord is 1670 dtex / 2. The density of this cord is 54 ends. The cord material used for the second belt ply is nylon fiber. The angle formed with respect to the circumferential direction of this cord is 0 °. The fineness of this cord is 1400 dtex / 2. The density of this cord is 54 ends. The ratio of the circumferential length L2 of the second belt ply to the half of the circumferential length LT of the tread surface to which the left and right tread ends are tied is 18%. The axial distance WP between the bead heel forming portions P1 and P2 provided in the mold used in the vulcanization process is 113% of the normal rim width WR. The axial distance WQ between the bead heel contact portions P3 on the left and right of the PCI rim used in the cooling process is the same as the normal rim width WR.

[Comparative Examples 3 and 4 and Examples 3 and 4]
A motorcycle tire was obtained in the same manner as in Example 1 except that the ratio of the peripheral length L2 of the second belt ply to the half of the peripheral length LT of the tread surface was as shown in Table 1 below.

[Examples 2 and 5]
Example 1 except that the ratio of the axial distance WP between the bead heel forming portions P1 and P2 provided in the mold used in the vulcanization process with respect to the regular rim width WR is as shown in Table 1 below. Similarly, a motorcycle tire was obtained.

[Example 6]
The motorcycle is the same as in Example 1 except that the ratio of the axial distance WQ between the bead heel contact portions on the left and right of the PCI rim used in the cooling process with respect to the regular rim width WR is as shown in Table 1 below. Tires were obtained.

[Comparative Examples 1 and 2]
Only the first belt ply is used as the belt, and the ratio of the axial distance WP between the bead heel forming portions P1 and P2 provided in the mold used in the vulcanization process for the normal rim width WR and the normal rim width WR A motorcycle tire was obtained in the same manner as in Example 1 except that the ratio of the axial distance WQ between the bead heel contact portions on the left and right of the PCI rim used in the cooling process was as shown in Table 1 below. .

[Real car evaluation]
A prototype tire was mounted on the rear wheel of a commercially available motorcycle having a displacement of 1000 cm ³ . The rim was MT17 × 6.00 and the tire internal pressure was 250 kPa. The front wheels are equipped with commercially available conventional tires. The tire size of this front wheel is 120 / 70ZR17. On the circuit course, turning at a speed of 100 km / h and straight running at a speed of 250 km / h were performed, and the rider performed a sensory evaluation with a perfect score of 5.0. Larger values indicate better results. Evaluation items are a sense of rigidity, responsiveness during turning, and operability during turning. The results are shown in Table 1 below.

  As shown in Table 1, it was confirmed that the motorcycle tires of the examples were excellent in steering stability during turning. From this evaluation result, the superiority of the present invention is clear.

  The motorcycle tire according to the present invention can be mounted on various vehicles.

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 a cross-sectional view showing a part of a mold used in a vulcanization process included in the tire manufacturing method of FIG. 1. FIG. 3 is a cross-sectional view showing a state where the tire of FIG. 1 is incorporated in a PCI rim. 4 is a partially enlarged cross-sectional view in which a part of the tire of FIG. 3 is enlarged.

Explanation of symbols

2 ... tyre 4 ... rim 6 ... tread 8 ... side wall 10 ... bead 12 ... carcass 14 ... belt 16 ... inner liner 18 ... tread surface 20. ..Groove 22 ... tread end 24 ... core 26 ... apex 28 ... carcass ply 30 ... first belt ply 32 ... second belt ply 34 ... mold 36 ... -Tread segment 38 ... Upper mold side mold 40 ... Lower mold side mold 42 ... Upper bead ring 44 ... Lower bead ring 46 ... PCI rim 48 ... Bead fitting section

Claims (1)

A tread whose outer surface forms a tread surface, a pair of sidewalls extending substantially inward in the radial direction from an end of the tread, a pair of beads extending further inward in the radial direction from the sidewall, and a tread and a sidewall A carcass spanned between both beads along the inner side, and a belt laminated with the carcass on the inner side in the radial direction of the tread;
This carcass has a carcass ply,
The carcass ply includes a carcass cord, and an absolute value of an angle formed by the carcass cord with respect to a tire equatorial plane is 70 ° or more and 90 ° or less,
This belt has a first belt ply in the center and a pair of second belt plies on both sides of the first belt ply,
The first belt ply and the second belt ply are adjacent to each other in the tire axial direction,
The length of the tread surface to which the left and right tread ends are tied is the circumferential length LT, and the ratio of the circumferential length L2 of the second belt ply to half of the circumferential length LT is 14% or more and 36% or less,
The first belt ply includes a first belt ply spirally wound in the tire circumferential direction, and the first belt ply includes a first belt cord and a first topping rubber, and an equatorial surface of the first belt cord. The absolute value of the angle formed with respect to is less than 5 °, the first belt cord is non-heat-shrinkable,
The second belt ply comprises a second belt ply spirally wound in the tire circumferential direction, and the second belt ply includes a second belt cord and a second topping rubber, and the equator surface of the second belt cord. the absolute value of the angle formed with respect is 5 ° or less, Ri the second belt cords heat shrinkable der,
The tire in a high temperature state after vulcanization is filled with air and cooled, so that the thermal contraction of the second belt cord is optimized.
A PCI rim is used for the cooling, the PCI rim has a bead fitting portion, the bead fitting portion has a bead heel contact portion, and a space between the right and left bead heel contact portions with respect to a normal rim width. The ratio of the axial distance is 95% or more and 105% or less,
It has a bead ring on which the outer surface of the bead is formed. This bead ring has a bead heel forming portion, and the ratio of the axial distance between the right and left bead heel forming portions to the normal rim width is 110% to 115%. Motorcycle tire vulcanized by a mold .

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