JP2008001177A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire 2 which is excellent in durability and mainly used for a small-sized truck. <P>SOLUTION: The tire 2 comprises a pair of beads 10, a carcass 12 laid between both beads 10, and a cord reinforcing layer 18 wound around the beads 10. The carcass 12 comprises a first carcass ply 28, a second carcass ply 30, and a third carcass ply 32. The first carcass ply 28 and the second carcass ply 30 are wound around the beads 10. The third carcass ply 32 is disposed without being wound around the beads 10. The cord reinforcing layer 18 is positioned between the first carcass ply 28 and the second carcass ply 30. The cord reinforcing layer 18 comprises an inside portion 44 positioned on axially inside of the beads 10, and an outside portion 46 positioned on axially outside of the beads 10. An upper end 50 of the inside portion 44 is positioned on the inside of an upper end 48 of the outside portion 46 in a radial direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire mainly used for a light truck.

  As vehicles become more sophisticated and highways are being developed, opportunities for small trucks to travel at high speeds while carrying cargo are increasing. In addition to the vehicle main body, the load by the loaded cargo acts on the tire mounted on the small truck. This load is large. In such a tire, the rigidity in the vicinity of the bead is increased in order to support the vehicle.

Japanese Unexamined Patent Publication No. Hei 8-132818 discloses a pneumatic radial tire that has improved durability and productivity while reducing the weight of the tire. This tire includes an outer carcass ply wound around the core of the bead and an inner carcass ply positioned inside the outer carcass ply without being wound around the core. The tire is configured such that the distance from the lower edge of the core to the lower end of the carcass ply is smaller than the distance from the lower edge to the upper end of the bead apex.
JP-A-8-132818

  When the tire is bent, the vicinity of the bead is inclined outward in the axial direction. During traveling, the vicinity of the bead and the flange of the rim repeatedly contact and separate. Thereby, chafing may occur in the tire. Such a tire is inferior in durability.

  When the tire is bent, the vicinity of the bead is deformed. This deformation causes distortion between the clinch and the carcass. The load acting on the tire mounted on the small truck is large. For this reason, in this tire, excessive distortion may occur between the clinch and the carcass. Excessive distortion causes looseness between this clinch and the carcass. Such a tire is inferior in durability.

  Some tires have increased clinch to increase durability. Tires with thick clinch have a large mass.

  An object of the present invention is to provide a pneumatic tire excellent in durability.

  The pneumatic tire according to the present invention includes a pair of beads, a carcass spanned between the two beads, and a cord reinforcing layer wound around the beads. The carcass includes a first carcass ply, a second carcass ply, and a third carcass ply. The first carcass ply and the second carcass ply are wound around the bead. The third carcass ply is arranged without being wound around the bead. The cord reinforcing layer is located between the first carcass ply and the second carcass ply. The cord reinforcing layer includes an inner portion located on the inner side in the axial direction of the bead and an outer portion located on the outer side in the axial direction of the bead. The upper end of the inner part is located inside the upper end of the outer part in the radial direction.

  Preferably, in this tire, the ratio of the height in the radial direction of the inner portion to the height in the radial direction up to a point where the maximum width in the axial direction is reached is not less than 40% and not more than 60%.

  Preferably, in this tire, the ratio of the difference between the radial height of the outer portion and the radial height of the inner portion to the radial height up to a point having the maximum axial width is 10% or more and 20% or less. It is.

  Preferably, in the tire, the cord reinforcing layer includes a reinforcing cord made of an organic fiber. Preferably, in the tire, the reinforcing cord is a nylon fiber.

  In this tire, the configuration of the carcass including the first carcass ply, the second carcass ply, and the third carcass ply is optimized, and the tire is provided with a cord reinforcing layer wound around the bead, so that the vicinity of the bead The rigidity is effectively increased. In this tire, deformation near the bead is small. For this reason, chafing and looseness do not occur in this tire. This tire is excellent in durability. In this tire, since it is not necessary to increase the clinch to increase the rigidity in the vicinity of the bead, the tire mass does not increase.

  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. FIG. 2 is a partially enlarged sectional view showing the tire 2 of FIG. 1 and 2, 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. In FIG. 2, a solid line BBL represents a bead base line. The tire 2 includes a tread 4, a sidewall 6, a clinch 8, a bead 10, a carcass 12, a belt 14, an inner liner 16, and a cord reinforcing layer 18. The tire 2 is a tubeless type pneumatic tire. The tire 2 is mounted on a small truck.

  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 groove 22 is carved in the tread surface 20. The groove 22 forms a tread pattern.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is made of a crosslinked rubber. The sidewall 6 absorbs an impact from the road surface by bending. Further, the sidewall 6 prevents the carcass 12 from being damaged.

  The clinch 8 further extends inward in the radial direction from the sidewall 6. The clinch 8 comes into contact with the rim when the tire 2 is incorporated into the rim. By this contact, the vicinity of the bead 10 is protected. This clinch 8 is made of a crosslinked rubber in consideration of wear resistance.

  The bead 10 is located inside the clinch 8 in the axial 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.

  The carcass 12 is bridged between the beads 10 on both sides, and extends along the inside of the tread 4, the sidewall 6, and the clinch 8. The carcass 12 includes a first carcass ply 28, a second carcass ply 30, and a third carcass ply 32. The first carcass ply 28 is wound around the core 24 of the bead 10 from the inner side toward the outer side in the axial direction. The second carcass ply 30 is located outside the first carcass ply 28 and is wound around the core 24 from the inner side toward the outer side in the axial direction. Therefore, the wound second carcass ply 30 is positioned on the inner side in the axial direction of the wound first carcass ply 28. The third carcass ply 32 is located outside the first carcass ply 28 and the second carcass ply 30. A part of the third carcass ply 32 is located on the outer side in the axial direction of the wound first carcass ply 28. The lower end 34 of the third carcass ply 32 reaches the vicinity of the core 24. The third carcass ply 32 is arranged without being wound around the core 24. In the tire 2, the winding end 36 of the first carcass ply 28 is located radially outside the winding end 38 of the second carcass ply 30. The lower end 34 of the third carcass ply 32 is located radially inward from the winding end 38 of the second carcass ply 30.

  Although not shown, the first carcass ply 28 is composed of a first cord and a topping rubber. The absolute value of the angle formed by the first cord with respect to the equator plane is usually 75 ° or more and 90 ° or less. The second carcass ply 30 includes a second cord and a topping rubber. The absolute value of the angle formed by the second cord with respect to the equator plane is usually 75 ° or more and 90 ° or less. The third carcass ply 32 includes a third cord and a topping rubber. The absolute value of the angle formed by the third cord with respect to the equator plane is usually 75 ° or more and 90 ° or less. In other words, the tire 2 is a radial tire. In the tire 2, when the absolute value of the angle formed by the first cord, the second cord, and the third cord with respect to the equator plane is less than 90 °, the angle formed by the first cord with respect to the equator plane is The angle that the second cord makes with the equator plane is opposite, and the angle that the second cord makes with the equator plane is opposite to the angle that the third cord makes with the equator plane, This carcass 12 is configured.

  The first cord, the second cord, and the third cord are usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. In the tire 2, the first cord, the second cord, and the third cord are made of polyester fibers. In the tire 2, the first cord, the second cord, and the third cord are made of the same fiber. Two of the first cord, the second cord, and the third cord may be the same fiber. The first cord, the second cord, and the third cord may be made of different 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 an inner belt ply 40 and an outer belt ply 42. In the tire 2, the axial width of the inner belt ply 40 is wider than the axial width of the outer belt ply 42. Although not shown, each of the inner belt ply 40 and the outer belt ply 42 includes a belt cord and a topping rubber. This belt cord is inclined with respect to the equator plane. The absolute value of the angle formed by the belt cord with respect to the equator plane is usually 10 ° to 35 °. The angle formed by the belt cord of the inner belt ply 40 with respect to the equator plane is opposite to the angle formed by the belt cord of the outer belt ply 42 with respect to the equator plane. The belt cord is preferably steel. An organic fiber may be used for this belt cord. 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 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.

  The cord reinforcing layer 18 is wound around the core 24 of the bead 10 and is positioned between the first carcass ply 28 and the second carcass ply 30. The cord reinforcing layer 18 increases the rigidity in the vicinity of the bead 10. The cord reinforcing layer 18 includes an inner portion 44 and an outer portion 46. The outer portion 46 is located on the outer side in the axial direction of the bead 10 and extends outward in the radial direction from the vicinity of the core 24. The upper end 48 of the outer portion 46 reaches the apex 26 of the bead 10. The inner portion 44 is located on the inner side in the axial direction of the bead 10 and extends outward in the radial direction from the vicinity of the core 24. The upper end 50 of the inner portion 44 reaches the apex 26. The upper end 50 of the inner portion 44 is located inside the upper end 48 of the outer portion 46 in the radial direction. The tire 2 is configured such that the radial height of the inner portion 44 is lower than the radial height of the outer portion 46. In the tire 2, the upper end 48 of the outer portion 46 is located inside the upper end 52 of the apex 26 in the radial direction. The upper end 50 of the inner portion 44 is located inside the upper end 52 of the apex 26 in the radial direction. The upper end 48 of the outer portion 46 may be located on the radially outer side of the apex 26. The upper end 50 of the inner portion 44 may be located on the radially outer side of the apex 26.

  Although not shown, the cord reinforcing layer 18 is made of a reinforcing cord and a topping rubber. The reinforcing cord is inclined with respect to the radial direction. The absolute value of the angle formed by the reinforcing cord with respect to the radial direction is usually 10 ° to 35 °. The reinforcing cord is preferably an organic fiber. Examples of the organic fiber include polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber. From the viewpoint of improving durability, the reinforcing cord is particularly preferably a nylon fiber. In the tire 2, a nylon fiber having a fineness of 940 dtex / 2 is used for the reinforcing cord.

  The tire 2 includes a cord reinforcing layer 18 wound around the bead 10 in addition to an optimized configuration of the carcass 12 including the first carcass ply 28, the second carcass ply 30 and the third carcass ply 32. Therefore, the rigidity in the vicinity of the bead 10 is effectively enhanced. In the tire 2, the deformation near the bead 10 is small. For this reason, in this tire 2, chafing and looseness do not occur. The tire 2 is excellent in durability.

  In the tire 2, it is not necessary to increase the thickness of the clinch 8 in order to increase the rigidity in the vicinity of the bead 10, so that the tire mass does not increase.

  As described above, in the tire 2, the upper end 50 of the inner portion 44 is positioned inside the upper end 48 of the outer portion 46 in the radial direction. On the inner side in the radial direction of the upper end 50 of the inner portion 44, the inner portion 44 and the outer portion 46 are located on both sides in the axial direction of the apex 26. In other words, the inner portion 44 and the outer portion 46 overlap each other on the radially inner side of the upper end 50 of the inner portion 44. On the radially outer side of the upper end 50 of the inner part 44, the outer part 46 is located on the outer side in the axial direction of the apex 26, and the inner part 44 is not disposed on the inner side in the axial direction of the apex 26. Therefore, in the tire 2, the upper end 50 of the inner portion 44 and the upper end 48 of the outer portion 46 are arranged in a region extending from the sidewall 6 to the clinch 8 as compared with a tire arranged so as to have the same height in the radial direction. The characteristics do not change abruptly. In the tire 2, the rigidity is improved while maintaining appropriate bending. In the tire 2, durability is enhanced without impairing the ride comfort.

  In the region from the sidewall 6 to the clinch 8, when the tire 2 is bent, the outer surface of the tire 2 is stretched in the radial direction. As described above, the radial height of the outer portion 46 is higher than the radial height of the inner portion 44. The outer portion 46 effectively suppresses deformation due to the stretching. Thereby, the distortion which arises between the clinch 8 and the carcass 12 with the bending of the tire 2 is suppressed. In the tire 2, looseness does not occur. The tire 2 is excellent in durability.

  In FIG. 2, a point PA represents a point having the maximum axial width. A double arrow line HA represents the height in the radial direction from the bead base line to this point PA. A double arrow line HB is a height in the radial direction from the bead base line to the upper end 48 of the outer portion 46. This radial height HB is the radial height of the outer portion 46. A double arrow line HC is a radial height from the bead base line to the upper end 50 of the inner portion 44. The radial height HC is the radial height of the inner portion 44.

  In the tire 2, the ratio of the radial height HC of the inner portion 44 to the radial height HA is preferably 40% or more and 60% or less. By setting this ratio to 40% or more, the cord reinforcing layer 18 effectively increases the rigidity in the vicinity of the bead 10. In the tire 2, chafing and looseness do not occur. The tire 2 is excellent in durability. In this respect, the ratio is more preferably equal to or greater than 45%, and particularly preferably equal to or greater than 50%. By setting this ratio to 60% 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 58%, and particularly preferably equal to or less than 55%.

  In the tire 2, the ratio of the radial height HB of the outer portion 46 to the radial height HA is preferably 50% or more and 80% or less. By setting this ratio to 50% or more, the cord reinforcing layer 18 effectively increases the rigidity in the vicinity of the bead 10. In the tire 2, chafing and looseness do not occur. The tire 2 is excellent in durability. From this viewpoint, the ratio is more preferably 55% or more, and particularly preferably 60% or more. By setting this ratio to 80% 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 75%, and particularly preferably equal to or less than 70%.

  In the tire 2, the ratio of the difference (HB−HC) between the radial height HB of the outer portion 46 and the radial height HC of the inner portion 44 to the radial height HA is 10% or more and 20% or less. Is preferred. By setting this ratio to 10% or more, the rigidity in the vicinity of the bead 10 is effectively enhanced. In the tire 2, chafing and looseness do not occur. The tire 2 is excellent in durability. Since the upper end 48 of the outer portion 46 and the upper end 50 of the inner portion 44 are appropriately separated from each other in the radial direction, a sudden characteristic change is suppressed in the region from the sidewall 6 to the clinch 8. Since the tire 2 bends appropriately, the ride comfort can be maintained. From this viewpoint, the ratio is more preferably 12% or more, and particularly preferably 15% or more. By setting this ratio to 20% or less, the cord reinforcing layer 18 can effectively contribute to the improvement of the rigidity in the vicinity of the bead 10. From this viewpoint, the ratio is more preferably 18% or less.

  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.

  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 light truck tire 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 / 75R15. The carcass includes a first carcass ply, a second carcass ply, and a third carcass ply. The first carcass ply and the second carcass ply are wound around the core of the bead from the inner side toward the outer side in the axial direction. The third carcass ply is located outside the first carcass ply and the second carcass ply, and is arranged without being wound around the core. A nylon fiber having a fineness of 940 dtex / 2 is used for the reinforcing cord of the cord reinforcing layer. The ratio (HC / HA × 100) of the radial height HC of the inner part to the radial height HA is 50%. The ratio (HB / HA × 100) of the radial height HB of the outer portion to the radial height HA is 60%. Therefore, the ratio of the difference (HB−HC) between the radial height HB of the outer portion and the radial height HC of the inner portion to the radial height HA ((HB−HC) / HA × 100) is 10 %.

[Examples 2 and 3]
A tire was obtained in the same manner as in Example 1 except that the ratio (HC / HA × 100) was as shown in Table 1 below.

[Comparative Examples 2 and 3 and Example 4]
A tire was obtained in the same manner as in Example 1 except that the ratio (HC / HA × 100) and the ratio (HB / HA × 100) were as shown in Table 1 below.

[Comparative Example 4]
A tire was obtained in the same manner as in Example 1 except that the carcass was not provided with the third carcass ply.

[Comparative Example 1]
It is a conventional tire that is commercially available. This tire is not provided with a cord reinforcing layer.

[Durability evaluation]
A prototype tire was mounted on the rim of a drum durability tester. The internal pressure of the prototype tire was set to a pressure corresponding to the maximum air pressure specified in JATMA standards. A load corresponding to 200% of the maximum load load specified in the JATMA standard was applied to the contact surface between the prototype tire and the drum, and the drum was rotated at a speed of 20 km / h. When the test time reached 400 hours, the prototype tire was removed from the testing machine, the prototype tire was disassembled, and the damage state was confirmed. The results are shown in Table 1 as index values. The larger this value, the better the durability.

  As shown in Table 1, the tires of the examples are excellent in durability. From this evaluation result, the superiority of the present invention is clear.

  According to the invention.

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 partially enlarged sectional view showing the tire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Tire 4 ... Tread 6 ... Side wall 8 ... Clinch 10 ... Bead 12 ... Carcass 14 ... Belt 16 ... Inner liner 18 ... Cord reinforcement layer 20 ... Tread surface 22 ... Groove 24 ... Core 26 ... Apex 28 ... First carcass ply 30 ... Second carcass ply 32 ... Third carcass ply 34 ... Lower end 36, 38 ... winding end 40 ... inner belt ply 42 ... outer belt ply 44 ... inner portion 46 ... outer portion 48, 50, 52 ... upper end

Claims (5)

A pair of beads, a carcass spanned between both beads, and a cord reinforcing layer wound around the beads,
The carcass includes a first carcass ply, a second carcass ply, and a third carcass ply,
The first carcass ply and the second carcass ply are wound around the bead,
This third carcass ply is arranged without being wrapped around this bead,
The cord reinforcing layer is located between the first carcass ply and the second carcass ply,
The cord reinforcing layer includes an inner portion located on the inner side in the axial direction of the bead and an outer portion located on the outer side in the axial direction of the bead.
A pneumatic tire in which the upper end of the inner portion is located inside the upper end of the outer portion in the radial direction.   2. The tire according to claim 1, wherein a ratio of a radial height of the inner portion to a radial height up to a point where the axial maximum width is 40% or more and 60% or less.   The ratio of the difference between the radial height of the outer portion and the radial height of the inner portion to the radial height up to a point having the maximum axial width is 10% or more and 20% or less. Tire described in.   The tire according to any one of claims 1 to 3, wherein the cord reinforcing layer includes a reinforcing cord made of an organic fiber. The tire according to any one of claims 1 to 4, wherein the reinforcing cord is a nylon fiber.

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