JP2015174511A - Pneumatic tire for all-terrain vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire 2 for all-terrain vehicle, which achieves improvement of steering stability without increase in weight.SOLUTION: A carcass 10 of a tire 2 is formed of a carcass ply 32. The carcass ply 32 is folded back around a core 28. In the carcass ply 32, by being folded in the manner, are formed a main part 34a and a folded part 34b. A belt 10 of the tire 2 comprises an inner lay 40a and an outer layer 40b. In the tire 2, an outer end 44 of a reinforcement layer 18 is provided between the inner layer 40a and the main part 34a. An inner end 46 of the reinforcement layer 18 is provided between an apex of a bead 8 and the main part 34a. A length L2 of a part where the reinforcement layer 18 overlaps the apex 30 is 5 mm to 50 mm. A length L3 of a part where the reinforcement layer 18 overlaps the inner layer 40a is 5 mm to 30 mm.

Description

  The present invention relates to a pneumatic tire for all-terrain vehicles.

  All Terrain Vehicle (hereinafter ATV) travels mainly on bad roads such as rocky land, sandy land, and muddy ground. Engines and suspensions installed in recent ATVs have high performance. In the tire used for this ATV, improvement in steering stability is required.

  A tire is configured by combining a number of members. The performance of the tire is controlled by adjusting the combination of these members and the characteristics of each member. Cut resistance is important for tires traveling on rough roads. From the viewpoint of improving durability, various studies have been made on the configuration of the sidewall portion of the tire. Examples of this study are disclosed in Japanese Patent Laid-Open Nos. 03-213408 and 05-0428803.

Japanese Patent Laid-Open No. 03-213408 Japanese Patent Laid-Open No. 05-042883

  The carcass ply that forms the tire carcass may be folded around the core of the bead. By this folding, a folded portion is formed. The folded portion having a large height can contribute to the rigidity of the tire. This tire is excellent in handling stability. However, this turn-up part affects the tire mass and production cost.

  The tire bead includes a core and an apex. An apex having a large height can contribute to the rigidity of the tire. This tire is excellent in handling stability. However, this apex affects the tire mass and production costs.

  The carcass ply includes a large number of cords arranged in parallel. The carcass ply may be configured such that these cords have a small inclination angle. In this case, the tread portion has high rigidity. In this tire, the tread surface does not sufficiently contact the road surface. Insufficient ground contact impairs steering stability.

  An object of the present invention is to provide a pneumatic tire for an all-terrain vehicle in which improvement in handling stability is achieved without increasing mass.

  The pneumatic tire for an all-terrain vehicle according to the present invention includes a tread whose outer surface forms a tread surface, a pair of sidewalls that extend substantially inward in the radial direction from the end of the tread, and each of which is more than the sidewall. A pair of beads positioned substantially inside in the radial direction, a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall, and a carcass on the radially inner side of the tread. A belt to be laminated and a pair of reinforcing layers each extending substantially inward in the radial direction from an end of the belt are provided. The bead includes a core and an apex extending radially outward from the core. The carcass is composed of one carcass ply. The carcass ply is folded around the core from the inner side to the outer side in the axial direction. By this folding, a main portion and a folding portion are formed on the carcass ply. The belt includes an inner layer and an outer layer. In the axial direction, the end of the inner layer is located outside the end of the outer layer. The outer end of the reinforcing layer is located between the inner layer and the main part. The inner end of the reinforcing layer is located between the apex and the main part. The carcass ply includes a large number of carcass cords arranged in parallel. The absolute value of the angle formed by each carcass cord with respect to the equator plane is 60 ° or more and 90 ° or less. The apex length L1 is not less than 20 mm and not more than 60 mm. The apex has a complex elastic modulus E * of 60 MPa to 120 MPa. The length L2 where the reinforcing layer overlaps with the apex is 5 mm or more and 50 mm or less. The length L3 at which this reinforcing layer overlaps with the inner layer is 5 mm or more and 30 mm or less.

  Preferably, in the all-terrain vehicle pneumatic tire, the ratio of the length L2 to the length L1 is not less than 0.25 and not more than 0.85.

  Preferably, in the pneumatic tire for an all-terrain vehicle, the reinforcing layer includes a plurality of reinforcing cords arranged in parallel. The absolute value of the angle formed by each reinforcing cord with respect to the circumferential direction is not less than 60 ° and not more than 90 °.

  Preferably, in the all-terrain vehicle pneumatic tire, the reinforcing cord intersects with the carcass cord.

  In the pneumatic tire for all-terrain vehicles according to the present invention, improvement in handling stability is achieved without increasing the mass.

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 plan view showing a part of the carcass ply forming the carcass of the tire of FIG. FIG. 3 is a side view showing a part of the reinforcing layer of the tire of FIG. 1.

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

  FIG. 1 shows an all-terrain vehicle pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal 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. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equator plane except for the tread pattern.

  The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 10, an inner liner 14, a chafer 16, and a reinforcing layer 18. The tire 2 is a tubeless type. The tire 2 is mounted on an all-terrain vehicle (ATV). In the tire 2, the internal pressure is adjusted to 15 to 45 kPa.

  The tread 4 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. Although not shown, the tread surface 20 has grooves. A tread pattern is formed by this groove. The tread 4 has a base layer 22 and a cap layer 24. The cap layer 24 is located on the outer side in the radial direction of the base layer 22. The cap layer 24 is laminated on the base layer 22. The base layer 22 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 22 is natural rubber. The cap layer 24 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The side wall 6 prevents the carcass 10 from being damaged. The sidewall 6 includes a rib 26. The rib 26 protrudes outward in the axial direction. Damage to the flange of the rim on which the tire 2 is mounted is prevented by the ribs 26.

  The bead 8 is located substantially inward of the sidewall 6 in the radial direction. The bead 8 includes a core 28 and an apex 30 that extends radially outward from the core 28. The core 28 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 30 is tapered outward in the radial direction. The apex 30 is made of a highly hard crosslinked rubber. From the viewpoint that the apex 30 can appropriately contribute to the rigidity of the tire 2, the complex elastic modulus E * of the apex 30 is preferably 60 MPa or more, and preferably 120 MPa or less.

In this specification, the complex elastic modulus E * of the apex 30 is measured in accordance with the provisions of “JIS K 6394”. The measurement conditions are as follows.
Viscoelastic spectrometer: "VESF-3" from Iwamoto Seisakusho
Initial strain: 10%
Dynamic strain: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

  The carcass 10 includes a carcass ply 32. In the tire 2, the number of carcass plies 32 constituting the carcass 10 is one. In other words, the carcass 10 includes a single carcass ply 32. In the tire 2, the portion of the tread 4 is more flexible than that of a tire provided with a carcass composed of two or more carcass plies 32. In the tire 2, the tread surface 20 is in sufficient contact with the road surface. Especially when traveling on rough roads, good grounding performance is exhibited. The carcass 10 can contribute to the steering stability of the tire 2. Moreover, the mass of the tire 2 is lighter than that of a tire having a carcass made of two or more carcass plies 32. The carcass 10 can contribute to weight reduction of the tire 2.

  In the tire 2, the carcass ply 32 is bridged between the beads 8 on both sides, and extends along the tread 4 and the sidewall 6. The carcass ply 32 is folded around the core 28 from the inner side to the outer side in the axial direction. By this folding, the carcass ply 32 is formed with a main portion 34a and a folding portion 34b.

  FIG. 2 shows a part of the carcass ply 32 of the tire 2. In FIG. 2, the horizontal direction is the axial direction of the tire 2, the vertical direction is the circumferential direction of the tire 2, and the direction perpendicular to the paper surface is the radial direction of the tire 2.

  As shown in the figure, the carcass ply 32 includes a large number of carcass cords 36 and a topping rubber 38 arranged in parallel. In the tire 2, each carcass cord 36 is inclined with respect to the equator plane. The carcass cord 36 may be orthogonal to the equator plane.

  In FIG. 2, an angle α represents an angle formed by the carcass cord 36 with respect to the equator plane. In the tire 2, the absolute value of the angle α is 60 ° or more. The tread 4 portion of the tire 2 has appropriate rigidity. Therefore, the driver can intentionally slide the tire 2. The carcass ply 32 of the tire 2 can contribute to slidability. The tire 2 is excellent in handling stability. In the tire 2, the upper limit of the absolute value of the angle α is 90 °. In other words, the absolute value of the angle α is 90 ° or less. That is, the carcass 10 of the tire 2 has a radial structure. In FIG. 2, the carcass cord 36 covered with the topping rubber 38 is represented by a solid line.

  In the tire 2, the carcass cord 36 is made of an organic fiber. More specifically, the carcass cord 36 is formed by twisting a plurality of filaments made of organic fibers. From the viewpoint of the strength of the carcass cord 36, the fineness of the filament is preferably 940 dtex or more and 2100 dtex or less. Preferred carcass cord 36 configurations are 940 dtex / 2 and 2100 dtex / 2. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, and aramid fibers. Examples of the polyester fiber include polyethylene terephthalate fiber and polyethylene naphthalate fiber.

  The belt 10 is located on the inner side in the radial direction of the tread 4. The belt 10 is laminated with the carcass 10. The belt 10 reinforces the carcass 10. The axial width of the belt 10 is preferably 0.7 times or more the maximum width of the tire 2.

  The belt 10 includes an inner layer 40a and an outer layer 40b. The belt 10 may include three or more layers 40. As is apparent from FIG. 1, in the axial direction, the end 42a of the inner layer 40a is located outside the end 42b of the outer layer 40b. In the tire 2, the width of the inner layer 40a is larger than the width of the outer layer 40b in the axial direction. In the tire 2, the end 42 a of the inner layer 40 a is the end of the belt 10.

  Although not shown, each of the inner layer 40a and the outer layer 40b 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 inclination angle is 15 ° or more and 50 ° or less. The inclination direction of the cord of the inner layer 40a with respect to the equator plane is opposite to the inclination direction of the cord of the outer layer 40b with respect to the equator plane.

  In the tire 2, the cords included in each layer of the belt 10 are made of organic fibers. More specifically, the cord is formed by twisting a plurality of filaments made of organic fibers. From the viewpoint of the strength of the cord, the fineness of the filament is preferably 940 dtex or more and 2100 dtex or less. Preferred code configurations are 940 dtex / 2 and 2100 dtex / 2. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, and aramid fibers. Examples of the polyester fiber include polyethylene terephthalate fiber and polyethylene naphthalate fiber.

  The inner liner 14 is located inside the carcass 10. The inner liner 14 is joined to the inner surface of the carcass 10. The inner liner 14 is made of a crosslinked rubber. The inner liner 14 is made of rubber having excellent air shielding properties. A typical base rubber of the inner liner 14 is butyl rubber or halogenated butyl rubber. The inner liner 14 maintains the internal pressure of the tire 2.

  The chafer 16 is located in the vicinity of the bead 8. When the tire 2 is incorporated into the rim, the chafer 16 comes into contact with the rim. By this contact, the vicinity of the bead 8 is protected. In this embodiment, the chafer 16 is made of cloth and rubber impregnated in the cloth. The material of the chafer 16 may be the same as that of the clinch, and the chafer 16 may be integrated with the clinch.

  The reinforcing layer 18 extends from the end 42a of the belt 10 substantially inward in the radial direction along the main portion 34a of the carcass ply 32. As is apparent from FIG. 1, the reinforcing layer 18 is located outside the main portion 34a. The reinforcing layer 18 is laminated with the main portion 34a. The tire 2 is provided with one reinforcing layer 18. Two or more reinforcing layers 18 may be provided on the tire 2.

  In the tire 2, the outer end 44 of the reinforcing layer 18 is located inside the belt 10 in the radial direction. The outer end 44 of the reinforcing layer 18 is positioned inside the end 42a of the belt 10 in the axial direction. The outer end 44 of the reinforcing layer 18 is located outside the end 42b of the outer layer 40b forming a part of the belt 10 in the axial direction. The outer end 44 of the reinforcing layer 18 is located between the inner layer 40a forming the other part of the belt 10 and the main portion 34a. More specifically, the outer end 44 of the reinforcing layer 18 is sandwiched between the inner layer 40a and the main portion 34a.

  In the tire 2, the inner end 46 of the reinforcing layer 18 is located inside the tip 48 of the apex 30 in the radial direction. The inner end 46 of the reinforcing layer 18 is located outside the core 28 in the radial direction. In the tire 2, the inner end 46 of the reinforcing layer 18 is located inside the apex 30 in the axial direction. The inner end 46 of the reinforcing layer 18 is located outside the main portion 34a of the carcass ply 32 in the axial direction. In the tire 2, the inner end 46 of the reinforcing layer 18 is located between the apex 30 and the main portion 34a. More specifically, the inner end 46 of the reinforcing layer 18 is sandwiched between the apex 30 and the main portion 34a.

  In FIG. 3, a part of the reinforcing layer 18 of the tire 2 is shown together with the carcass ply 32. In FIG. 3, the left-right direction is the circumferential direction of the tire 2, the up-down direction is the radial direction of the tire 2, and the direction perpendicular to the paper surface is the axial direction of the tire 2. FIG. 3 shows a state when the tire 2 of FIG. 1 is viewed from the side surface.

  As shown in the drawing, the reinforcing layer 18 includes a plurality of reinforcing cords 50 and a topping rubber 52 arranged in parallel. In the tire 2, each reinforcing cord 50 is inclined with respect to the circumferential direction. The reinforcing cord 50 may be orthogonal to the circumferential direction. In FIG. 3, the reinforcing cord 50 covered with the topping rubber 52 of the reinforcing layer 18 and the carcass cord 36 covered with the topping rubber 38 of the carcass ply 32 are represented by solid lines.

  In FIG. 3, an angle β represents an angle formed by the reinforcing cord 50 with respect to the circumferential direction. In the present specification, the angle β is indicated by an angle formed by the reinforcing cord 50 with respect to the solid line LP in FIG. The solid line LP represents the position indicated by the symbol PB in FIG. As shown in FIG. 1, the position PB has a radial height (double arrow H1 in FIG. 1) from the bead base line (solid line BBL in FIG. 1). It is a position that is half of the middle double arrow H0). That is, the angle β is an angle formed by the reinforcing cord 50 with respect to the circumferential direction, which is obtained at a position where the height H1 is half the cross-sectional height H0 of the tire 2. The bead base line is a line that defines a rim diameter (see JATMA) of a rim (not shown) on which the tire 2 is mounted. The cross-sectional height H0 is indicated by the radial height from the bead baseline to the equator.

  In the tire 2, the absolute value of the angle β is 60 ° or more. By setting the absolute value of the angle β to 60 ° or more, the reinforcing layer 18 can contribute to the rigidity of the sidewall 6 portion. The reinforcing layer 18 brings good controllability to the tire 2. The tire 2 is excellent in handling stability. In the tire 2, the upper limit of the absolute value of the angle β is 90 °. In other words, the absolute value of the angle β is 90 ° or less.

  As shown in FIG. 3, in the tire 2, it is preferable that the reinforcing cord 50 of the reinforcing layer 18 intersects the carcass cord 36 of the carcass ply 32. In the tire 2, the side wall 6 has moderate rigidity. The tire 2 is excellent in handling stability.

  In the tire 2, the reinforcing cord 50 is made of an organic fiber. More specifically, the reinforcing cord 50 is formed by twisting a plurality of filaments made of organic fibers. From the viewpoint of the strength of the reinforcing cord 50, the fineness of the filament is preferably 940 dtex or more and 2100 dtex or less. Preferred reinforcement cord 50 configurations are 940 dtex / 2 and 2100 dtex / 2. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, and aramid fibers. Examples of the polyester fiber include polyethylene terephthalate fiber and polyethylene naphthalate fiber.

  In the tire 2, the left and right reinforcing layers 18 are arranged apart from each other in the axial direction. In the tire 2, the reinforcing layer 18 does not exist on the equator plane. In the tire 2, the tread 4 portion is flexible. In the tire 2, the tread surface 20 is in sufficient contact with the road surface. Especially when traveling on rough roads, good grounding performance is exhibited. The tire 2 is excellent in handling stability. Moreover, the absence of the reinforcing layer 18 on the equator plane can contribute to weight reduction. In the tire 2, improvement in steering stability is achieved without increasing the mass.

  In the tire 2, the reinforcing layer 18 is located between the sidewall 6 and the carcass 10. This reinforcing layer 18 prevents the occurrence of a cut due to the collision of crushed stone or the like. The tire 2 is excellent in puncture resistance.

  In the tire 2, the reinforcing layer 18 overlaps the inner layer 40a in the radial direction, but does not overlap the outer layer 40b. In the tire 2, the rigidity of the end 42a of the belt 10 is not excessive. In the tire 2, a good grounding property can be maintained. The tire 2 is excellent in handling stability.

  In the tire 2, the reinforcing layer 18 overlaps with the apex 30 in the axial direction, but does not overlap with the core 28. In the tire 2, the influence on the mass by the reinforcing layer 18 is effectively suppressed. This reinforcing layer 18 can reduce production costs.

  In FIG. 1, what is indicated by reference sign PC is a reference position of the apex 30 that forms part of the bead 8. This position PC is the center of the width of the apex 30 at the end on the core 28 side. A double-headed arrow L1 represents the length from the position PC to the tip 48 of the apex 30. In the present specification, this length L1 is the length of the apex 30. A double-headed arrow L2 represents the length from the inner end 46 of the reinforcing layer 18 to the tip 48 of the apex 30. In this specification, this length L2 is a length in which the reinforcing layer 18 overlaps the apex 30. This length L2 is measured along the apex 30. A double-headed arrow L3 represents the length from the outer end 44 of the reinforcing layer 18 to the end 42a of the inner layer 40a. In this specification, this length L3 is a length in which the reinforcing layer 18 overlaps the inner layer 40a. This length L3 is measured along the inner layer 40a. A double-headed arrow L4 represents the length from the end 42a of the inner layer 40a to the end 42b of the outer layer 40b. This length L4 is equivalent to half of the difference between the width of the inner layer 40a and the width of the outer layer 40b.

  In the tire 2, the length L1 is 20 mm or more and 60 mm or less. The apex 30 can effectively contribute to the rigidity of the tire 2 by setting the length L1 to 20 mm or more. In the tire 2, improvement in slidability, traction, and controllability is achieved. The tire 2 is excellent in handling stability. By setting the length L1 to 60 mm or less, the influence of the apex 30 on the rigidity can be suppressed. In the tire 2, slidability and riding comfort can be appropriately maintained.

  In the tire 2, the length L2 is not less than 5 mm and not more than 50 mm. By setting the length L2 to 5 mm or more, the overlap between the reinforcing layer 18 and the apex 30 can effectively contribute to the rigidity of the tire 2. In the tire 2, improvement in slidability, traction, and controllability is achieved. The tire 2 is excellent in handling stability. By setting the length L2 to 50 mm or less, the influence on the rigidity due to the overlap between the reinforcing layer 18 and the apex 30 can be suppressed. In the tire 2, slidability, controllability, and riding comfort can be appropriately maintained. Since the length of the reinforcing layer 18 that overlaps the apex 30 is appropriately adjusted, the mass of the tire 2 having the reinforcing layer 18 is appropriate. Moreover, the reinforcing layer 18 can contribute to a reduction in production cost.

  In the tire 2, the ratio of the length L2 to the length L1 is preferably 0.25 or more and 0.85 or less. By setting this ratio to 0.25 or more, the overlap between the reinforcing layer 18 and the apex 30 can effectively contribute to the rigidity of the tire 2. In the tire 2, an improvement in controllability is achieved. The tire 2 is excellent in handling stability. By setting this ratio to 0.85 or less, the influence on the rigidity due to the overlap between the reinforcing layer 18 and the apex 30 can be suppressed. In the tire 2, the controllability can be appropriately maintained. Since the length of the reinforcing layer 18 that overlaps the apex 30 is appropriately adjusted, the mass of the tire 2 having the reinforcing layer 18 is appropriate. Moreover, the reinforcing layer 18 can contribute to a reduction in production cost.

  In the tire 2, the length L3 is 5 mm or more and 30 mm or less. In the tire 2 in which the length L3 is set to 5 mm or more, the overlapping state between the reinforcing layer 18 and the inner layer 40a can be maintained even if stress repeatedly acts during traveling. The tire 2 is excellent in durability. In the tire 2 in which the length L3 is set to 30 mm or less, the influence on the rigidity due to the overlap between the reinforcing layer 18 and the inner layer 40a is suppressed. Since the good grounding property is maintained, the tire 2 is excellent in handling stability.

  In the tire 2, the length L4 is preferably 10 mm or more. In the tire 2 in which the length L4 is set to 10 mm or more, the rigidity of the end 42a portion of the belt 10 is not excessive. In the tire 2, a good grounding property can be maintained. The tire 2 is excellent in handling stability. In this respect, the length L4 is more preferably 20 mm or more, further preferably 30 mm or more, and particularly preferably 40 mm or more. From the viewpoint of reinforcing the carcass 10, the length L4 is preferably 60 mm or less.

  In the present invention, the size and angle of each member 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. In the case of the passenger car tire 2, 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 for ATV 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 AT20 × 10R9. The carcass of this tire consists of one carcass ply. The absolute value of the angle α of the carcass cord included in the carcass ply is 80 ° (degrees). This tire includes one reinforcing layer between the carcass and the sidewall. The absolute value of the angle β of the reinforcing cord included in the reinforcing layer is 80 °. The inclination direction of the reinforcing cord is opposite to the inclination direction of the carcass cord. The reinforcing cord intersects with the carcass cord. This is indicated by “Y” in the table. The apex length L1 is 45 mm. The complex elastic modulus E * of this apex is 90 MPa. The length L2 where the reinforcing layer overlaps with the apex is 25 mm. Therefore, the ratio of the length L2 to the length L1 is 0.56. The length L3 where the reinforcing layer overlaps with the inner layer is 10 mm.

[Comparative Example 3]
A tire was obtained in the same manner as in Example 1 except that the carcass was composed of two carcass plies.

[Comparative Example 1]
Comparative Example 1 is a conventional tire. In Comparative Example 1, no reinforcing layer is provided. The carcass of this comparative example 1 consists of two carcass plies. The absolute value of the angle formed by the carcass cord included in each carcass ply with respect to the equator plane is 80 °. The apex length L1 is 45 mm. Apex has a complex elastic modulus E * of 90 MPa.

[Comparative Example 2]
Comparative Example 2 is a conventional tire. In Comparative Example 2, no reinforcing layer is provided. The carcass of this comparative example 2 consists of one carcass ply. The absolute value of the angle formed by the carcass cord included in the carcass ply with respect to the equator plane is 90 °. The apex length L1 is 45 mm. Apex has a complex elastic modulus E * of 90 MPa.

[Example 2-3 and Comparative Example 4]
A tire was obtained in the same manner as in Example 1 except that the angle α was as shown in Table 2 below.

[Examples 4-8 and Comparative Example 5]
A tire was obtained in the same manner as in Example 1 except that the specification of the reinforcing layer was as shown in Table 3 below. In Example 5, the reinforcing cord of the reinforcing layer does not intersect with the carcass cord of the carcass ply. This is represented as “N” in the table.

  In Comparative Example 5, no reinforcing layer is provided. The carcass of this comparative example 5 consists of one carcass ply. The absolute value of the angle formed by the carcass cord included in the carcass ply with respect to the equator plane is 80 °. The apex length L1 is 45 mm. Apex has a complex elastic modulus E * of 90 MPa.

[Example 10 and Comparative Example 7]
A tire was obtained in the same manner as in Example 1 except that the length L1 was as shown in Table 4 below and the ratio L2 / L1 was changed.

[Example 9 and Comparative Example 6]
Tires were obtained in the same manner as in Example 1 except that the length L1 and the length L2 were as shown in Table 4 below and the ratio L2 / L1 was changed.

[Examples 11-12 and Comparative Example 8-9]
A tire was obtained in the same manner as in Example 1 except that the complex elastic modulus E * of Apex was as shown in Table 5 below.

[Examples 13-16 and Comparative Example 10]
A tire was obtained in the same manner as in Example 1 except that the length L2 was as shown in Table 6 below and the ratio L2 / L1 was changed.

[Examples 17-19 and Comparative Examples 11-14]
Tires were obtained in the same manner as in Example 1 except that the length L1 and the length L2 were as shown in Tables 7 and 8 below and the ratio L2 / L1 was changed.

[Example 20-21 and Comparative Example 15-16]
A tire was obtained in the same manner as in Example 1 except that the length L3 was as shown in Table 8 below.

[Maneuvering stability and ride comfort]
The tire was assembled in a “9 × 8.0 AT” rim and filled with air so that the internal pressure of the tire was 25 kPa. This tire was mounted on a sports type ATV with a displacement of 450 cc. The driver was allowed to drive the ATV on a dirt course composed of an unpaved road surface to evaluate the handling stability and ride comfort. Steering stability was evaluated from the viewpoint of slidability, traction and controllability. The results are shown in Tables 1 to 8 below as indices. Larger numbers are preferable.

[Mass of tire]
The mass of the tire was measured. The results are shown in Tables 1 to 8 below. The smaller the value, the lighter.

[durability]
The tire was assembled in a “9 × 8.0 AT” rim and filled with air so that the internal pressure of the tire was 25 kPa. This tire was mounted on a drum-type running test machine, and a load twice as large as the load corresponding to the maximum use internal pressure in the JATMA internal pressure-load correspondence table was applied to the tire. This tire was run on a drum having a radius of 1.7 m at a speed of 80 km / h. The appearance of the tire after traveling for 3000 km was observed to confirm the presence or absence of damage. The results are shown in Tables 1 to 8 below. The case where damage is recognized is represented by “NG”, and the case where damage is not observed is represented by “G”.

  As shown in Tables 1 to 8, the tire of the example has a higher evaluation than the tire of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The tire described above can be applied to various vehicles.

2 ... Tire 4 ... Tread 6 ... Sidewall 8 ... Bead 10 ... Carcass 12 ... Belt 18 ... Reinforcement layer 20 ... Tread surface 28 ... Core 30 ..Apex 32 ... carcass ply 34a ... main part 34b ... turned part 36 ... carcass cords 40a, 40b, 40 ... layers 42a, 42b ... ends 44 ... outer ends 46 ... inner end 48 ... tip 50 ... reinforcement cord

Claims (4)

A tread whose outer surface forms a tread surface; a pair of sidewalls each extending substantially inward in the radial direction from an end of the tread; a pair of beads each positioned substantially inward in the radial direction from the sidewall; A carcass spanned between one bead and the other bead along the inside of the tread and the sidewall, and a belt laminated with the carcass on the radially inner side of the tread, respectively, from the end of the belt A pair of reinforcing layers extending substantially inward in the radial direction,
The bead includes a core and an apex extending radially outward from the core;
The carcass consists of one carcass ply,
The carcass ply is folded around the core from the inner side to the outer side in the axial direction,
By this folding, a main part and a folding part are formed in this carcass ply,
The belt includes an inner layer and an outer layer;
In the axial direction, the end of the inner layer is located outside the end of the outer layer,
The outer end of the reinforcing layer is located between the inner layer and the main part,
The inner end of the reinforcing layer is located between the apex and the main part,
The carcass ply includes a plurality of carcass cords arranged in parallel;
The absolute value of the angle formed by each carcass cord with respect to the equator plane is 60 ° or more and 90 ° or less,
The apex length L1 is 20 mm or more and 60 mm or less,
The complex elastic modulus E * of this apex is 60 MPa or more and 120 MPa or less,
The length L2 where the reinforcing layer overlaps with the apex is 5 mm or more and 50 mm or less,
A pneumatic tire for all-terrain vehicles, wherein the length L3 of the reinforcing layer overlapping with the inner layer is 5 mm or more and 30 mm or less.   The pneumatic tire for all-terrain vehicles according to claim 1, wherein a ratio of the length L2 to the length L1 is 0.25 or more and 0.85 or less. The reinforcing layer includes a plurality of reinforcing cords arranged in parallel,
The pneumatic tire according to claim 1 or 2, wherein an absolute value of an angle formed by each reinforcing cord with respect to a circumferential direction is 60 ° or more and 90 ° or less.   The pneumatic tire for all-terrain vehicles according to claim 3, wherein the reinforcing cord intersects with the carcass cord.

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