JP5145205B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  The tire includes a pair of beads and a carcass spanned between the two beads. The bead includes a core and an apex. The core is ring-shaped and includes a plurality of non-stretchable wires. The apex extends radially outward from the core. Apex is made of a highly hard crosslinked rubber. The carcass includes a carcass ply. The carcass ply is usually folded around the core.

  FIG. 7 is a schematic view showing a part of the manufacturing situation of a conventional tire. FIG. 7 shows a former 2, a carcass ply 4, and a bead 10 including a core 6 and an apex 8. The carcass ply 4 is wound around the former 2. A bead 10 is combined with the carcass ply 4. The carcass ply 4 is folded around the bead 10. Although not shown, in the former 2, members such as sidewalls and treads are assembled to form a low cover (also referred to as an uncrosslinked tire). This raw cover is put into a mold in the vulcanization step, and a tire is obtained.

When the tire is incorporated into the rim, the vicinity of the bead 10 contacts the rim. From the viewpoint of improving tire performance, various studies have been made on the configuration of the bead 10. Japanese Patent Laid-Open No. 2001-97010 discloses a tire in which the rigidity of the bead is adjusted by using a bead wire structure without applying an additional reinforcing member such as a wire insert or a flipper. In this tire, the radially outer position of the bead wire structure is the same as or outside the rim line position.
JP 2001-97010 A

  As described above, in the conventional manufacturing method, the carcass ply 4 is folded back by the bead 10. From the viewpoint of weight reduction and rigidity control, if the size of the apex 8 is reduced while the shape of the core 6 is left as it is, a space is formed when the carcass ply 4 is folded, and air is caught in the bead 10. . In this case, air remains in the formed bead 10. The quality of such a tire is not sufficient. By simply reducing the size of the apex 8, it is not possible to obtain a light weight and high quality tire.

  An object of the present invention is to provide a high-quality pneumatic tire that is lightweight and excellent in handling stability.

  The pneumatic tire according to the present invention includes a pair of beads. Each of the beads has a core including a wire extending in the circumferential direction. The number of strands of this core is 2 or more. The number of turns of the core is at least three times the number of strands. When the tire is mounted on a regular rim having a flange, the radially outer position of the wire is radially inner than the radially outer end of the flange.

  Preferably, in this tire, the ratio of the cross-sectional area of the wire to the cross-sectional area of the bead is 70% or more.

  Preferably, in this tire, the number of strands is two.

  Preferably, in this tire, the number of turns is eight.

  In the pneumatic tire according to the present invention, the wires included in the core are wound in the circumferential direction while being aligned so that the number of strands is two or more and the number of turns is three times or more of the number of strands. Yes. This core can appropriately contribute to the rigidity of the tire. This tire is excellent in handling stability. When the tire is mounted on the regular rim, the radially outer position of the wire is radially inward from the outer end of the flange of the regular rim. This tire is also excellent in responsiveness during turning. Since this core can prevent the formation of a space when the carcass ply is folded back, the entrainment of air into the bead is suppressed. This tire is of high quality because the occurrence of poor air residues can be prevented. In this tire, when an apex is provided on the bead, the size of the apex can be reduced. It is also possible to remove the apex from the constituent members of the tire. With this tire, weight reduction can be achieved. Such a tire can contribute to an improvement in productivity.

  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 12 according to an embodiment of the present invention together with a regular rim 14. FIG. 2 is an enlarged cross-sectional view showing a part of FIG. 1 and 2, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The tire 12 has a substantially bilaterally symmetric shape with a one-dot chain line CL in FIG. 1 as the center. This alternate long and short dash line CL represents the equator plane of the tire 12. 1 and 2, the tire 12 is mounted on a regular rim 14 (hereinafter, rim 14). The tire 12 is for a two-wheeled vehicle. The tire 12 is a tubeless type. The rim 14 includes a bead seat 16 that extends in the axial direction, and a flange 18 that extends radially outward from the bead seat 16. The rim 14 is an MT type deep bottom rim defined by the JATMA standard.

  The tire 12 includes a tread 20, a sidewall 22, a bead 24, a carcass 26, a belt 28, and an inner liner 30.

  The tread 20 is made of a crosslinked rubber having excellent wear resistance. The tread 20 has a shape protruding outward in the radial direction. The tread 20 includes a tread surface 32. The tread surface 32 is in contact with the road surface. A groove 34 is carved in the tread surface 32. The groove 34 forms a tread pattern. The groove 34 may not be cut in the tread 20.

  The sidewall 22 extends substantially inward in the radial direction from the end of the tread 20. The sidewall 22 is made of a crosslinked rubber. The side wall 22 absorbs an impact from the road surface by bending. Furthermore, the sidewall 22 prevents the carcass 26 from being damaged.

  The bead 24 is located substantially inward of the sidewall 22 in the radial direction. The bead 24 includes a core 36. The core 36 has a ring shape.

  The core 36 includes a wire 38 and a topping rubber 40 extending in the circumferential direction. The wire 38 is non-stretchable. The material of the wire 38 is steel.

  As shown in the drawing, the cross sections of the 16 wires 38 are aligned in two rows in the axial direction and eight steps in the radial direction. In the present specification, the number of rows in the cross section arranged in the axial direction is referred to as the number of strands of the core 36. In the tire 12, the number of strands of the core 36 is two. In the present specification, the number of steps in the cross section arranged in the radial direction is the number of turns of the core 36. In the tire 12, the number of turns of the core 36 is eight. In the tire 12, the number of cross-sections of the wires 38 included in the core 36 is indicated by the product of the number of strands and the number of turns. In the drawing, the radially outer position of the wire 38 included in the core 36 is shown as a point PA.

  The tire 12 is not provided with an apex made of a highly hard crosslinked rubber and having a tapered shape in the radial direction. Accordingly, an end 42 (hereinafter, an outer end 42 of the core 36) located on the radially outer side of the core 36 corresponds to the outer end 44 of the bead 24. The bead 24 may be provided with an apex. In this case, since the apex is disposed on the outer side in the radial direction of the core 36, the end located on the outer side in the radial direction of the apex corresponds to the outer end 44 of the bead 24.

  The carcass 26 includes a carcass ply 46. The carcass 26 may be composed of two or more carcass plies 46. As shown in the figure, the carcass ply 46 is bridged between the beads 24 on both sides, and extends along the inside of the tread 20 and the sidewalls 22. The carcass ply 46 is folded around the core 36 from the inner side to the outer side in the axial direction. An end 48 of the carcass ply 46 is located on the radially outer side with respect to the outer end 42 of the core 36. The end 48 of the carcass ply 46 may be located radially inward from the outer end 42 of the core 36.

  Although not shown, the carcass ply 46 includes a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is usually 70 ° to 90 °. In other words, the carcass 26 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. A carcass 26 having a bias structure may be employed.

  The belt 28 is located outside the carcass 26 in the radial direction. The belt 28 is laminated with the carcass 26. The belt 28 reinforces the carcass 26. The belt 28 includes an inner layer 50 and an outer layer 52. Although not shown, each of the inner layer 50 and the outer layer 52 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The absolute value of the tilt angle is not less than 10 ° and not more than 35 °. The cord inclination direction of the inner layer 50 is opposite to the cord inclination direction of the outer layer 52. A preferred material for the cord is steel. An organic fiber may be used for the cord. In the tire 12, a band having a cord extending substantially in the circumferential direction may be provided outside the belt 28 in the radial direction from the viewpoint of improving high-speed stability.

  The inner liner 30 is joined to the inner peripheral surface of the carcass 26. The inner liner 30 is made of a crosslinked rubber. The inner liner 30 is made of rubber having excellent air shielding properties. The inner liner 30 plays a role of maintaining the internal pressure of the tire 12.

  In the tire 12, the core 36 is formed using a ribbon composed of a plurality of wires 38 and a topping rubber 40.

  FIG. 3 is a cross-sectional perspective view showing a part of the ribbon 54 used for forming the core 36. In FIG. 3, the double arrow line A represents the longitudinal direction of the ribbon 54, and the double arrow line B represents the width direction of the ribbon 54. As shown, the ribbon 54 includes four wires 38. These wires 38 are arranged at equal intervals in the width direction. Each of these wires 38 extends in the longitudinal direction and is covered with a topping rubber 40. In the method for manufacturing the tire 12, the wire 38 and the topping rubber 40 are extruded by an extruder to form the ribbon 54, and then the ribbon 54 is wound to form a ring-shaped laminate.

  FIG. 4 is a cross-sectional perspective view showing a part of the laminated body 56 used for forming the core 36. In FIG. 3, the double arrow line C represents the circumferential direction of the stacked body 56, the double arrow line D represents the radial direction of the stacked body 56, and the double arrow line B represents the width of the stacked body 56. It represents the direction. The width direction of the laminated body 56 coincides with the width direction of the ribbon 54. In the laminated body 56, the ribbon 54 is wound in the circumferential direction. As described above, since the wire 38 included in the ribbon 54 extends in the longitudinal direction of the ribbon 54, the wire 38 included in the laminated body 56 is also wound in the circumferential direction. As shown in the figure, the laminate 56 is formed by winding the ribbon 54 eight times.

  In the method for manufacturing the tire 12, the laminate 56 is divided in half in the width direction. By this division, the core 36 wound in the circumferential direction while the wires 38 are aligned is formed. In the tire 12, the laminated body 56 is divided in half to form the core 36, and thus the number of wires 38 included in the core 36 is two. In FIG. 4, the plane along the two-dot chain line DL is a split plane.

  In the tire 12 manufacturing method, the core 36 may be formed by other methods. FIG. 5 is a schematic view showing a state of formation of the core 36 by another method. FIG. 5 shows a drum 58 for forming the core 36. In FIG. 5, the horizontal direction is the axial direction, and the vertical direction is the radial direction. The direction perpendicular to the paper surface is the circumferential direction.

  The drum 58 includes a main body 60, a small diameter portion 62, and a movable portion 64. The small diameter portion 62 is located outside the main body 60 in the axial direction. The small diameter portion 62 has an outer diameter smaller than the outer diameter of the main body 60. The small diameter portion 62 is formed integrally with the main body 60. The movable portion 64 is located on the outer side in the axial direction of the small diameter portion 62. The movable part 64 has an outer diameter larger than the outer diameter of the small diameter part 62. The outer diameter of the movable part 64 is equivalent to the outer diameter of the main body 60. The movable part 64 is configured to move in the axial direction. In the drum 58, the movable portion 64 abuts on the small diameter portion 62, whereby a groove 66 is formed in the portion of the small diameter portion 62. The groove 66 extends in the circumferential direction.

  When the core 36 is formed using the drum 58, a cord 68 in which one wire 38 is covered with the topping rubber 40 is prepared. The cord 68 is wound around the groove 66 to form the core 36 having two strands and eight turns. Also in this case, the wire 38 is wound while being aligned, and the core 36 is formed. The movable portion 64 is moved outward in the axial direction from the core 36 and is taken out from the small diameter portion 62. A core 36 having two strands and eight turns may be formed by winding a ribbon made of two wires 38 and a topping rubber 40 around the groove 66.

  The core 36 formed as described above is supplied to the former 2. Other members constituting the tire 12 such as the carcass ply 46 are also supplied to the former 2.

  FIG. 6 is a schematic diagram showing a part of the manufacturing status of the tire 12 of FIG. In FIG. 6, the former 2, the carcass ply 46, and the core 36 are shown. In FIG. 6, the horizontal direction is the axial direction, and the vertical direction is the radial direction. The direction perpendicular to the paper surface is the circumferential direction.

  The former 2 includes a main body 70 and a movable portion 72. Although not shown, the main body 70 is composed of a plurality of segments and is configured to be able to expand the diameter. The movable portion 72 is located outside the main body 70 in the axial direction. The movable part 72 has an outer diameter smaller than the outer diameter of the main body 70. The movable portion 72 is configured to move inward in the axial direction when the diameter of the main body 70 is increased.

  In this manufacturing method, the core 36 is combined with the carcass ply 46 wound around the former 2. Next, the carcass ply 46 is folded back by the core 36.

  In FIG. 6, the point PB represents the radially outer position of the core 36 before the vulcanization process. Point PC represents the radially outer position of the wire 38 included in the core 36 before the vulcanization process. As shown in the drawing, the radially outer position PB and the outer surface 74 of the main body 70 are substantially equal in the radial direction. Since the carcass ply 46 is folded back while being in contact with the core 36, an excessive space is not formed between the carcass ply 46 and the core 36. From the viewpoint of preventing space formation, it is preferable that the outer position PB is set to a position equivalent to the position of the outer surface 76 of the carcass ply 46 wound around the main body 70 in the radial direction. In the tire 12, since no apex is provided, the outer position PC of the wire 38 is preferably set to a position equivalent to the position of the outer surface 74 of the main body 70 in the radial direction.

  In this manufacturing method, air entrainment into the bead 24 can be suppressed, so that occurrence of defective air remaining is prevented. The tire 12 is of high quality. According to this manufacturing method, even if an apex is adopted for the tire 12, the size of the apex can be reduced without impairing the quality of the tire 12. The tire 12 manufactured in this way is lightweight and can contribute to a reduction in production cost.

  In this manufacturing method, after the carcass ply 46 is folded, the movable portion 72 is moved inward in the axial direction while the diameter of the main body 70 of the former 2 is expanded, and the shape of the carcass ply 46 is adjusted. Members such as the sidewall 22 and the tread 20 are further combined to obtain a raw cover. The raw cover is put into a mold held at a predetermined temperature. The raw cover is pressed between the cavity surface of the mold and the outer surface of the bladder. The raw cover is heated by heat conduction from the bladder and the mold. While the rubber composition of the low cover flows by the pressurization and heating, the rubber composition causes a crosslinking reaction, and the tire 12 of the present invention is obtained.

  As shown in FIG. 2, when the tire 12 is mounted on the rim 14, the tire 12 abuts against the bead seat 16 and the flange 18. In this mounted state, the radially outer position PA of the wire 38 included in the core 36 is on the radially inner side of the outer end 78 of the flange 18. Since the core 36 can appropriately contribute to the rigidity, the tire 12 is excellent in responsiveness when turning.

  In the tire 12, the number of turns is three times or more the number of strands. In other words, the ratio of the number of turns to the number of strands is 3 or more. By setting this ratio to 3 or more, the core 36 can appropriately contribute to the rigidity of the tire 12 while restraining air from being caught in the bead 24. The tire 12 has high quality and excellent handling stability. If this ratio is excessive, the outer position PA will be radially outward from the outer end 78 of the flange 18. In this case, the responsiveness at the time of turning will be inhibited. In the tire 12, this ratio is preferably set to 5 or less from the viewpoint that the response at the time of turning can be appropriately maintained. This ratio is more preferably set to 4 from the viewpoint that a tire 12 excellent in handling stability and riding comfort can be obtained.

  In the tire 12, the number of strands is preferably 2 from the viewpoint that air entrainment into the bead 24 is suppressed. From the viewpoint that the core 36 can effectively contribute to the rigidity of the tire 12, the number of turns is preferably 6 or more and 8 or less, and 8 is particularly preferable. As described above, in the tire 12, the number of strands is 2 and the number of turns is 8. The tire 12 is excellent in steering stability and ride comfort because the core 36 can effectively contribute to rigidity.

  In the tire 12, the wires 38 included in the core 36 are appropriately aligned and the rigidity is adjusted, so that the amount of rubber used in the bead 24 can be reduced. In the tire 12, the production cost can be reduced and the weight can be reduced without impairing the steering stability. From this viewpoint, the ratio of the cross-sectional area of the wire 38 to the cross-sectional area of the bead 24 (hereinafter referred to as area ratio) is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more. From the viewpoint of durability, the area ratio is preferably 98% or less. The cross-sectional area of the wire 38 means the sum of all cross-sectional areas of the wire 38 included in the cross section of the core 36. In the tire 12, the bead 24 includes the core 36, and thus the cross-sectional area of the core 36 corresponds to the cross-sectional area of the bead 24. The cross-sectional area of the core 36 includes the cross-sectional area of the topping rubber 40 that constitutes the core 36. When the bead 24 includes the core 36 and the apex 8, the sum of the cross-sectional area of the core 36 and the cross-sectional area of the apex 8 is the cross-sectional area of the bead 24.

  In FIG. 2, the double arrow line HA represents the radial height from the radially outer position PA of the wire 38 to the outer end 44 of the bead 24. A double arrow line HB represents the height in the radial direction from the radially outer position PA of the wire 38 to the radially inner position PD of the wire 38. This height HB is also called the core 36 height.

  In the tire 12, the height HA is preferably 10 mm or less from the viewpoint of reducing production costs and achieving weight reduction. From the viewpoint that durability can be appropriately maintained, the height HA is preferably 0.5 mm or more.

  In the tire 12, the height HB is preferably 8 mm or more from the viewpoint that the remaining of air in the core 36 is suppressed and a high-quality tire 12 can be obtained. From the viewpoint of handling stability and riding comfort, the height HB is preferably 16 mm or less.

  In the tire 12, the outer diameter of the wire 38 included in the core 36 is preferably 0.5 mm or more and 1.5 mm or less. By setting the outer diameter to 0.5 mm or more, the core 36 can appropriately contribute to the rigidity of the tire 12. The tire 12 is excellent in handling stability. By setting the outer diameter to 1.5 mm or less, excessive rigidity due to the core 36 can be suppressed, and steering stability can be appropriately maintained.

  In the tire 12, from the viewpoint of durability, the breaking strength of the wire 38 is preferably 1 kN / piece or more. Since it is preferable that the wire 38 does not break, the upper limit of the breaking strength is not specified. This breaking strength is measured based on JIS G 3510.

  In the present invention, the dimension and angle of each member of the tire 12 are measured in a state where the tire 12 is incorporated in the regular rim 14 and the tire 12 is filled with air so as to have a regular internal pressure. During the measurement, no load is applied to the tire 12. In the present specification, the normal rim 14 means the rim 14 defined in the standard on which the tire 12 depends. “Standard rim 14” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims 14. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 12 depends. “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. In the case of the passenger car tire 12, the dimensions and angles are measured in a state where the internal pressure is 180 kPa.

  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 configuration shown in FIG. 1 and having the specifications shown in Table 1 below was obtained. The size of this tire is “120/60 ZR17”. In this tire, the cross section of the core includes a cross section of 16 wires. The number of strands S of this core is 2, and the number of turns T is 8. The ratio (T / S) of the number of turns T to the number of strands S is 4. The outer diameter of this wire is 0.96 mm. This tire is not provided with an apex. This is indicated as “B” in Table 1. The radial height (HA + HB) from the radially inner position PD of the wire to the outer end of the bead is 9 mm. The ratio of the cross-sectional area of the wire to the cross-sectional area of the bead (hereinafter referred to as area ratio) is 92%. When this tire is mounted on a rim (rim size: MT3.50 × 17), the radially outer position of the wire is disposed radially inward from the outer end of the flange of the rim. This arrangement state is displayed as “Y” in Table 1.

[Examples 2 to 3 and Comparative Examples 3 to 5]
Tires were obtained in the same manner as in Example 1 except that the number of turns T was changed and the ratio (T / S) and area ratio were changed as shown in Table 1 below. In Comparative Example 5, in the state of being mounted on the rim, the radially outer position of the wire is disposed on the radially outer side than the outer end of the flange. This arrangement state is displayed as “N” in Table 1.

[Examples 4 to 7]
A tire was obtained in the same manner as in Example 1 except that an apex was provided and the height (HA + HB) and area ratio were as shown in Table 1 below. The presence of an apex is displayed as “A” in Table 1.

[Comparative Examples 1 and 2]
Comparative Example 1 is a conventional tire. Comparative Example 2 is a tire formed by removing the apex from the constituent members of Comparative Example 1. The number of strands S of the core provided in each of Comparative Example 1 and Comparative Example 2 is 4, and the number of turns T is 3.

[Check remaining air]
The cross section of the bead portion of the prototype tire was visually observed to check for the presence of remaining air. The observation results are shown in Table 1 below as “G” when no air remaining is confirmed and “N” when air remaining is confirmed.

[Durability evaluation]
The prototype tire was assembled on a regular rim (size: MT3.50 × 17) and filled with air to adjust the tire internal pressure to a normal internal pressure (225 kPa). A test machine having a drum having a diameter of 1.5 m was subjected to a running test of the tire by applying a load (1.79 N) of 1.5 times the maximum load capacity to the tire. The speed was 65 km / h and the running time was 100 hours. After completion of the running test, the tire surface was visually observed to check for cracks. After this confirmation, the prototype tire was dismantled and the internal damage situation was confirmed. The observation results are shown in Table 1 below as “G” when no cracks or internal damage was confirmed, and as “N” when these were confirmed.

[Steering stability evaluation]
The prototype tire was mounted on the front wheel of a commercially available motorcycle (4 cycles) with a displacement of 400 cc and filled with air so that its internal pressure was 225 kPa. A commercially available tire (size: “160 / 60ZR17”) was attached to the rear wheel, and air was filled so that the internal pressure was 250 kPa. This motorcycle was run on a circuit course whose road surface is asphalt, and a sensory evaluation by a rider was performed. The evaluation items are the limit height during turning, responsiveness and response. The results are shown in Table 1 below as index values with Comparative Example 1 taken as 100. The larger this value, the better.

[Evaluation of tire mass]
The mass of the prototype tire was measured. The results are shown in Table 1 below as index values with Comparative Example 1 taken as 100. The smaller this value, the lighter the tire mass.

  As shown in Table 1, the tires of the examples are excellent in durability and handling stability with no air remaining. In the tire of this embodiment, weight reduction is also achieved. From this evaluation result, the superiority of the present invention is clear.

  The pneumatic tire according to the present invention can be applied not only to a two-wheeled vehicle but also to a passenger car.

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 cross-sectional view showing a part of FIG. FIG. 3 is a cross-sectional perspective view showing a part of the ribbon used for forming the core. FIG. 4 is a schematic view showing a part of the laminate used for forming the core. FIG. 5 is a schematic diagram showing a core formation state by another method. FIG. 6 is a schematic view showing a part of the manufacturing situation of the tire of FIG. FIG. 7 is a schematic diagram showing a part of a conventional tire manufacturing situation.

Explanation of symbols

2 ... Former 4, 46 ... Carcass ply 6,36 ... Core 8 ... Apex 10, 24 ... Bead 12 ... Tire 14 ... Rim 16 ... Bead seat 18 ... Flange 20 ... Tread 22 ... Side wall 26 ... Carcass 28 ... Belt 30 ... Inner liner 32 ... Tread surface 34 ... Groove 38 ... Wire 40 ...・ Topping rubber 50 ... Inner layer 52 ... Outer layer 54 ... Ribbon 56 ... Laminate

Claims (4)

A tire comprising a pair of beads,
Each of the beads has a core including a wire extending in the circumferential direction,
The number of strands of this core is 2 or more,
The number of turns of the core is more than three times the number of strands,
When this tire is mounted on a regular rim with a flange,
A pneumatic tire in which a radially outer position of the wire is radially inner than a radially outer end of the flange.   The tire according to claim 1, wherein a ratio of a cross-sectional area of the wire to a cross-sectional area of the bead is 70% or more.   The tire according to claim 1 or 2, wherein the number of strands is two.   The tire according to claim 3, wherein the number of turns is eight.

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