JP2014162268A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire 10 achieving an increase in longitudinal stiffness while suppressing an increase in torsional rigidity.SOLUTION: A tire 10 comprises: a tread 56; a pair of side walls 60; a pair of beads 62; a carcass 64 laid over between one bead 62 and the other bead 62 along the inside of the tread 56 and the side walls 60; and a thin layer 72 laid over between one bead 62 and the other bead 62 along the carcass 64. The carcass 64 comprises a first ply 76 and a second ply 78 located outside the first ply 76. Each of the first ply 76 and the second ply 78 comprises many cords arranged in parallel. A modulus of angles that each cord makes with respect to an equatorial plane is 70° or more. The thin layer 72 is located between the first ply 76 and the second ply 78. The thin layer 72 consists of cross-linked rubber. A tensile stress at the time of the 100% extension of the thin layer 72 is 1.5 MPa or more and not more than 3.0 MPa.

Description

  The present invention relates to a pneumatic tire. Specifically, the present invention relates to a pneumatic tire for a two-wheeled vehicle.

  Tire stiffness affects performance. The tire includes members such as a tread, a sidewall, a carcass, and a bead. In the tire, the rigidity is controlled by adjusting the specifications of these members. Examination examples regarding this rigidity control are disclosed in Japanese Patent Application Laid-Open Nos. 2006-142922 and 2009-057008.

JP 2006-142922 A JP 2009-057008 A

  With the increase in size of two-wheeled vehicles, tires having high longitudinal rigidity are required from the viewpoint of traction during acceleration and turning force.

  The tire includes a carcass spanned between the beads on both sides. A carcass usually consists of two plies. These plies contain a large number of codes in parallel. An angle formed by each cord with respect to the equator plane (hereinafter referred to as an inclination angle) affects the longitudinal rigidity. From the viewpoint of high longitudinal rigidity, a small inclination angle may be adopted.

  The inclination angle of the cord affects the tightening of the tire by the carcass. A small tilt angle results in tight tightening.

  When the two-wheeled vehicle turns, the tire is twisted in the traveling direction by the rider's steering. The above-described tightening of the tire by the carcass affects the resistance to torsion, in other words, the torsional rigidity. A small tilt angle results in high torsional stiffness.

  Torsional stiffness affects the response to steering. High torsional stiffness results in a fast response. If this response is too fast, it will be difficult to hold the vehicle body stably. Such a tire is inferior in handling stability.

  From the viewpoint of high longitudinal rigidity, a cord having high rigidity may be adopted for the carcass. Also in this case, the tire has high torsional rigidity. Also in this tire, the response to steering is fast, and it becomes difficult to hold the vehicle body stably.

  An object of the present invention is to provide a pneumatic tire in which an increase in longitudinal rigidity is achieved while suppressing an increase in torsional rigidity.

  The pneumatic tire according to the present invention has a tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the tread, and each positioned radially inward of the sidewalls. A pair of beads, a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall, and between the one bead and the other bead along the carcass It is equipped with a thin layer. The carcass includes a first ply and a second ply located outside the first ply. Each of the first ply and the second ply includes a plurality of cords arranged in parallel. The absolute value of the angle formed by each cord with respect to the equator plane is 70 ° or more. The thin layer is located between the first ply and the second ply. This thin layer is made of a crosslinked rubber. The tensile stress at 100% elongation of the thin layer is 1.5 MPa or more and 3.0 MPa or less.

  Preferably, in this pneumatic tire, the thickness of the thin layer is not less than 0.3 mm and not more than 2.0 mm.

  Preferably, in the pneumatic tire, a ratio of a radial height from the bead base line to the end of the thin layer to a radial height from the bead base line to the end of the tread surface is 0.7 or less. It is.

  In the pneumatic tire according to the present invention, a thin layer is located between the first ply and the second ply of the carcass. This thin layer contributes to the longitudinal rigidity of the tire. With this tire, great traction can be obtained during acceleration. A large turning force can be obtained during turning.

  In this tire, the thin layer has a proper tensile stress at 100% elongation. For this reason, when the tire is twisted by the rider's steering, the tire has an appropriate torsional rigidity. In other words, the thin layer of the tire absorbs the stress around the steering shaft acting on the tire while generating resistance to torsion. This tire responds appropriately to steering. This tire is excellent in stability. According to the present invention, it is possible to obtain a tire in which an increase in longitudinal rigidity is achieved while suppressing an increase in torsional rigidity.

FIG. 1 is a perspective view showing a two-wheeled vehicle according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a part of the pneumatic tire mounted on the front wheel of the two-wheeled vehicle of FIG. FIG. 3 is a cross-sectional view showing a part of the pneumatic tire mounted on the rear wheel of the two-wheeled vehicle of FIG.

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

  FIG. 1 shows a two-wheeled vehicle 2. The two-wheeled vehicle 2 includes a front wheel 4 and a rear wheel 6. A pneumatic tire 8 is incorporated in the front wheel 4. The tire 8 is also referred to as a front tire. A pneumatic tire 10 different from the front tire 8 is incorporated in the rear wheel 6. The tire 10 is also referred to as a rear tire. A set of tires including the front tire 8 and the rear tire 10 is also referred to as a tire pair 12. In other words, the tire pair 12 includes a front tire 8 and a rear tire 10.

  FIG. 2 shows the front tire 8. In FIG. 2, the vertical direction is the radial direction of the tire 8, the horizontal direction is the axial direction of the tire 8, and the direction perpendicular to the paper surface is the circumferential direction of the tire 8. In FIG. 2, an alternate long and short dash line CLF represents the equator plane of the tire 8. The shape of the tire 8 is symmetric with respect to the equator plane except for the tread pattern.

  In FIG. 2, the tire 8 is incorporated in the rim 14. The rim 14 is a regular rim. The tire 8 is filled with air. The internal pressure of the tire 8 is a normal internal pressure.

  Unless otherwise stated, the dimensions and angles of the members of the tire 8 are measured in a state where the tire 8 is incorporated in a normal rim and the tire 8 is filled with air so as to have a normal internal pressure. At the time of measurement, no load is applied to the tire 8. In the present specification, the normal rim means a rim defined in a standard on which the tire 8 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 8 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. The same applies to the rear tire 10 described later.

  The tire 8 includes a tread 16, a wing 18, a sidewall 20, a bead 22, a carcass 24, a band 26, an inner liner 28, a chafer 30 and a thin layer 32. The tire 8 is a tubeless type.

  The tread 16 has a shape protruding outward in the radial direction. The tread 16 forms a tread surface 34 that contacts the road surface. Although not shown, the tread surface 34 has a groove. A tread pattern is formed by this groove. The tread 16 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  In FIG. 2, what is indicated by reference numeral PF is an end of the tread surface 34. The tire 8 exhibits the maximum axial width at the end PF. In other words, the end PF is a point on the outer surface of the tire 8 that indicates the maximum width in the axial direction.

  The wing 18 is located between the tread 16 and the sidewall 20. The wing 18 is joined to each of the tread 16 and the sidewall 20. The wing 18 is made of a crosslinked rubber having excellent adhesiveness.

  The sidewall 20 extends substantially inward in the radial direction from the tread 16. The sidewall 20 is located outside the carcass 24 in the axial direction. The sidewall 20 prevents the carcass 24 from being damaged. The sidewall 20 is made of a crosslinked rubber having excellent cut resistance and weather resistance.

  The bead 22 is located radially inward of the sidewall 20. The bead 22 includes a core 36 and an apex 38 that extends radially outward from the core 36. The core 36 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 38 is tapered outward in the radial direction. The apex 38 is made of a highly hard crosslinked rubber.

  The carcass 24 includes a first ply 40 and a second ply 42. The first ply 40 and the second ply 42 are bridged between the beads 22 on both sides, and extend along the tread 16 and the sidewall 20.

  The first ply 40 is folded around the core 36 from the inner side to the outer side in the axial direction. By this folding, the main portion 44 and the folding portion 46 are formed in the first ply 40. The main portion 44 extends from the equator plane toward the left and right cores 36. The folded portion 46 extends substantially outward in the radial direction from the main portion 44. In the tire 8, the end 48 of the turned-up portion 46 is located near the end PF of the tread surface 34.

  The second ply 42 is located outside the first ply 40 on the equator plane. The second ply 42 extends from the equator plane toward the core 36. The second ply 42 extends from one bead 22 to the other bead 22 via the equator plane. In the tire 8, the end 50 of the second ply 42 is located radially inward from the end 48 of the folded portion 46. The portion of the end 50 of the second ply 42 is positioned between the main portion 44 of the first ply 40 and the folded portion 46 in the axial direction. The portion of the end 50 of the second ply 42 may be located on the outer side in the axial direction than the folded portion 46.

  In the tire 8, the second ply 42 is not folded around the core 36. As described above, the carcass 24 includes two plies, and the first ply 40 is folded around the core 36. The structure of the carcass 24 is also referred to as “1-1” structure. The carcass 24 may be composed of two plies, and these plies may be folded around the core 36. The structure of the carcass 24 is referred to as a “2-0” structure. The carcass 24 may be formed from three or more plies. From the viewpoint of the mass of the tire 8, the carcass 24 is preferably formed from three plies, and more preferably formed from two plies.

  Although not shown, each of the first ply 40 and the second ply 42 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 70 ° or more and 90 ° or less. In other words, the carcass 24 of the tire 8 has a radial structure. In the tire 8, by setting the absolute value of the angle to 70 ° or more, the influence of the carcass 24 on the longitudinal rigidity can be suppressed. From this viewpoint, the absolute value of this angle is preferably 75 ° or more. In the tire 8, the absolute value of the angle is preferably 88 ° or less from the viewpoint that a sufficient camber thrust is obtained. When the absolute value of the angle is set to be less than 90 °, preferably, the inclination direction of the cord of the first ply 40 with respect to the equator plane is the inclination direction of the cord of the second ply 42 with respect to the equator plane. Is the opposite.

  In the tire 8, the cord of the carcass 24 is made of an organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The band 26 is located inside the tread 16 in the radial direction. The band 26 is located outside the carcass 24 in the radial direction. In the tire 8, the band 26 is laminated on the carcass 24 without interposing other members. Although not shown, the band 26 is made of a cord and a topping rubber. The cord is wound in a spiral. The band 26 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. The band 26 can contribute to the radial rigidity of the tire 8. The band 26 can suppress the influence of centrifugal force that acts during traveling. The tire 8 is excellent in high speed stability. The cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The inner liner 28 is located inside the carcass 24. The inner liner 28 is joined to the inner surface of the carcass 24. The inner liner 28 is made of a crosslinked rubber. For the inner liner 28, rubber having excellent air shielding properties is used. A typical base rubber of the inner liner 28 is butyl rubber or halogenated butyl rubber. The inner liner 28 maintains the internal pressure of the tire 8.

  The chafer 30 is located in the vicinity of the bead 22. When the tire 8 is incorporated into the rim 14, the chafer 30 contacts the rim 14. By this contact, the vicinity of the bead 22 is protected. In this embodiment, the chafer 30 is made of cloth and rubber impregnated in the cloth.

  The thin layer 32 is bridged between the beads 22 on both sides along the carcass 24. The thin layer 32 extends from one bead 22 to the other bead 22 via the equator plane. The end 52 of the thin layer 32 is located radially inward from the end 48 of the folded portion 46 of the first ply 40. The end 52 of the thin layer 32 is located near the end 50 of the second ply 42. In the tire 8, the end 52 of the thin layer 32 is located radially inward from the end 50 of the second ply 42. The end 52 of the thin layer 32 may be located radially outside the end 50 of the second ply 42. The end 52 of the thin layer 32 may coincide with the end 50 of the second ply 42 in the radial direction.

  In the tire 8, the thin layer 32 is located outside the main portion 44 of the first ply 40. The thin layer 32 is laminated with the main portion 44. A second ply 42 is located outside the thin layer 32. The second ply 42 is laminated with the thin layer 32.

  In the tire 8, the thin layer 32 can contribute to the longitudinal rigidity of the tire 8. In the tire 8, the thin layer 32 is located between the main portion 44 of the first ply 40 and the second ply 42. For this reason, the thin layer 32 is bent integrally with the first ply 40 and the second ply 42. The integrity of the thin layer 32 and the carcass 24 in the tire 8 is remarkable compared to the integrity of another tire in which the thin layer 32 is disposed outside the second ply 42 or inside the first ply 40. is there. In the tire 8, the thin layer 32 can effectively contribute to the increase in the longitudinal rigidity. Moreover, as described above, the inclination angle of the cord of the carcass 24 is 70 ° or more. As a result, the movement of the cord included in the carcass 24 is suppressed, so that the thin layer 32 can contribute more effectively to the increase in the longitudinal rigidity. Since the tire 8 has high longitudinal rigidity, a large traction can be obtained during acceleration. A large turning force can be obtained during turning.

  In the tire 8, bending in the zone from the end portion of the tread 16 to the sidewall 20, in other words, in the buttress zone is large. As described above, in the tire 8, the thin layer 32 extends from one bead 22 to the other bead 22 via the equator plane. In the tire 8, a thin layer 32 is disposed in the buttress zone. In the tire 8, the thin layer 32 can effectively contribute to the increase in the longitudinal rigidity. In the tire 8, a large traction can be obtained during acceleration. A large turning force can be obtained during turning.

  When the two-wheeled vehicle 2 turns, the tire 8 is twisted in the traveling direction by the rider's steering. In the tire 8, the thin layer 32 disposed between the first ply 40 and the second ply 42 is made of a crosslinked rubber. In other words, the thin layer 32 does not include cords that are juxtaposed like the ply of the carcass 24. Moreover, as will be described later, the thin layer 32 has an appropriate tensile stress at 100% elongation (also referred to as 100% modulus). For this reason, when the tire 8 is twisted by the rider's steering, the tire 8 has an appropriate torsional rigidity. In other words, the thin layer 32 absorbs the stress around the steering shaft acting on the tire 8 while generating resistance to torsion. The tire 8 responds appropriately to steering. The tire 8 is excellent in stability. As described above, the thin layer 32 of the tire 8 can contribute to an increase in the longitudinal rigidity. Therefore, according to the present invention, it is possible to obtain the tire 8 in which the increase in the longitudinal rigidity is achieved while suppressing the increase in the torsional rigidity.

  In the tire 8, the thin layer 32 has a tensile stress MF at 100% elongation of 1.5 MPa to 3.0 MPa. By setting the tensile stress MF to 1.5 MPa or more, the thin layer 32 can contribute to an increase in longitudinal rigidity. Moreover, since the torsional rigidity is appropriately maintained, the tire 8 appropriately responds to steering. From this viewpoint, the tensile stress MF is preferably 1.8 MPa or more. By setting the tensile stress MF to 3.0 MPa or less, the thin layer 32 effectively absorbs the stress around the steering shaft. Even in this case, since the torsional rigidity is appropriately maintained, the tire 8 appropriately responds to the steering. Since the increase in the longitudinal rigidity is appropriately suppressed, a good riding comfort is maintained. In this respect, the tensile stress MF is preferably 2.5 MPa or less. As described above, the tire 8 is incorporated in the front wheel 4 of the two-wheeled vehicle 2. When the two-wheeled vehicle 2 turns, the degree of twisting of the tire 8 is greater than that of the tire 10 attached to the rear wheel 6. From the viewpoint of easy steering, the tensile stress MF is more preferably 2.2 MPa or less.

In the present application, the tensile stress MF is measured in accordance with the provisions of “JIS-K6251”. The conditions are as follows.
Specimen shape = No. 4 dumbbell Environmental temperature = 23 ° C
Test machine = Toyo Seiki Seisakusho Co., Ltd. trade name "Strograph"
Tensile speed = 500mm / min

  In FIG. 2, a solid line BLF represents a baseline. The base line BLF is a line that defines the rim diameter (see JATMA) of the rim 14 on which the tire 8 is mounted. The base line BLF extends in the axial direction. The double arrow AF represents the height in the radial direction from the base line BLF to the end 52 of the thin layer 32. A double-headed arrow BF represents the radial height from the base line BLF to the end PF of the tread surface 34.

  In the tire 8, the ratio of the height AF to the height BF is preferably 0.7 or less. By setting this ratio to 0.7 or less, the thin layer 32 can effectively contribute to an increase in longitudinal rigidity. In the tire 8, a large traction can be obtained during acceleration. A large turning force can be obtained during turning. In this respect, the ratio is more preferably equal to or less than 0.5. From the viewpoint of easy manufacture of the tire 8 and the influence on the cost, this ratio is preferably 0.1 or more, and more preferably 0.3 or more. In light of the influence on torsional rigidity, this ratio is more preferably 0.4 or more.

  In FIG. 2, the double arrow TF represents the thickness of the thin layer 32. This thickness TF is measured along the equator plane.

  In the tire 8, the thickness TF is preferably 0.3 mm or greater and 2.0 mm or less. By setting the thickness TF to be 0.3 mm or more, the thin layer 32 can effectively contribute to the increase in the longitudinal rigidity while suppressing the influence of the thin layer 32 on the torsional rigidity. From this viewpoint, the thickness TF is more preferably 0.4 mm or more. By setting the thickness TF to be equal to or less than 2.0 mm, an increase in the longitudinal rigidity is appropriately suppressed, so that a good riding comfort is maintained. From this viewpoint, the thickness TF is more preferably 1.5 mm or less. From the viewpoint that the thin layer 32 effectively absorbs the stress around the steering shaft and the tire 8 appropriately responds to steering, the thickness TF is more preferably 0.8 mm or less.

  FIG. 3 shows the rear tire 10. In FIG. 3, the vertical direction is the radial direction of the tire 10, the horizontal direction is the axial direction of the tire 10, and the direction perpendicular to the paper surface is the circumferential direction of the tire 10. In FIG. 3, an alternate long and short dash line CLR represents the equator plane of the tire 10. The shape of the tire 10 is symmetrical with respect to the equator plane except for the tread pattern. Except for the shape of the tire 10, the tire 10 has substantially the same configuration as that of the tire 8 shown in FIG.

  In FIG. 3, the tire 10 is incorporated in a rim 54. The rim 54 is a regular rim. The tire 10 is filled with air. The internal pressure of the tire 10 is a normal internal pressure.

  Similar to the tire 8 shown in FIG. 2, the tire 10 includes a tread 56, a wing 58, a sidewall 60, a bead 62, a carcass 64, a band 66, an inner liner 68, a chafer 70, and a thin layer 72. . The tire 10 is a tubeless type.

  In FIG. 3, what is indicated by reference sign PR is the end of the tread surface 74. The tire 10 has the maximum axial width at the end PR. In other words, the end PR is a point on the outer surface of the tire 10 that indicates the maximum width in the axial direction.

  The carcass 64 of the tire 10 includes a first ply 76 and a second ply 78, like the carcass 64 of the tire 10 shown in FIG. The first ply 76 and the second ply 78 are bridged between the beads 62 on both sides, and extend along the tread 56 and the sidewall 60.

  The first ply 76 is folded around the core 80 from the inner side to the outer side in the axial direction. The main portion 82 of the first ply 76 extends from the equatorial plane toward the left and right cores 80. The folded portion 84 extends substantially outward in the radial direction from the main portion 82. In the tire 10, the end 86 of the folded portion 84 is located near the end PR of the tread surface 74.

  The second ply 78 is located outside the first ply 76 on the equator plane. The second ply 78 extends from the equator plane toward the core 80. The second ply 78 extends from one bead 62 to the other bead 62 via the equator plane. In the tire 10, the end 88 of the second ply 78 is positioned radially inward from the end 86 of the folded portion 84. The end 88 portion of the second ply 78 is positioned between the main portion 82 of the first ply 76 and the folded portion 84 in the axial direction. Also in the tire 10, as in the tire 8 shown in FIG. 2, the end 88 portion of the second ply 78 may be positioned on the outer side in the axial direction than the folded portion 84.

  The carcass 64 of the tire 10 has a “1-1” structure, similar to the tire 8 shown in FIG. The carcass 64 may have a “2-0” structure.

  Although not shown, each of the first ply 76 and the second ply 78 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 70 ° or more and 90 ° or less. In other words, the carcass 64 of the tire 10 has a radial structure. In the tire 10, the absolute value of the angle is set to 70 ° or more, so that the influence of the carcass 64 on the longitudinal rigidity can be suppressed. From this viewpoint, the absolute value of this angle is preferably 75 ° or more. In the tire 10, the absolute value of the angle is preferably 88 ° or less from the viewpoint that a sufficient camber thrust can be obtained. When the absolute value of the angle is set to be less than 90 °, preferably, the inclination direction of the cord of the main portion 82 of the first ply 76 with respect to the equator plane is the inclination direction of the cord of the second ply 78 with respect to the equator plane. Is the opposite.

  In the tire 10, the cord of the carcass 64 is made of an organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The thin layer 72 is bridged between the beads 62 on both sides along the carcass 64. The thin layer 72 extends from one bead 62 to the other bead 62 via the equator plane. The end 90 of the thin layer 72 is located radially inward from the end 86 of the folded portion 84 of the first ply 76. The end 90 of this thin layer 72 is located near the end 88 of the second ply 78. In the tire 10, the end 90 of the thin layer 72 is located radially inward from the end 88 of the second ply 78. The end 90 of the thin layer 72 may be located radially outward from the end 88 of the second ply 78. The end 90 of the thin layer 72 may coincide with the end 88 of the second ply 78 in the radial direction.

  In the tire 10, the thin layer 72 is located outside the main portion 82 of the first ply 76. The thin layer 72 is laminated with the main portion 82. A second ply 78 is located outside the thin layer 72. The second ply 78 is laminated with the thin layer 72.

  In the tire 10, the thin layer 72 can contribute to the longitudinal rigidity of the tire 10. In the tire 10, the thin layer 72 is located between the main portion 82 of the first ply 76 and the second ply 78. Therefore, the thin layer 72 is bent integrally with the first ply 76 and the second ply 78. The integrity of the thin layer 72 and the carcass 64 in the tire 10 is remarkable as compared to the integrity of another tire in which the thin layer 72 is disposed outside the second ply 78 or inside the first ply 76. is there. In the tire 10, the thin layer 72 can effectively contribute to the increase in longitudinal rigidity. Moreover, as described above, the inclination angle of the carcass 64 cord is 70 ° or more. As a result, the movement of the cord included in the carcass 64 is suppressed, so that the thin layer 72 can contribute more effectively to the increase in the longitudinal rigidity. Since the tire 10 has high longitudinal rigidity, large traction can be obtained during acceleration. A large turning force can be obtained during turning.

  In the tire 10, the bending in the buttress zone is large. In the tire 10, a thin layer 72 is disposed in the badless zone. In the tire 10, the thin layer 72 can effectively contribute to the increase in longitudinal rigidity. Since the tire 10 has high longitudinal rigidity, large traction can be obtained during acceleration. A large turning force can be obtained during turning.

  When the two-wheeled vehicle 2 turns, the tire 10 is twisted in the traveling direction by the rider's steering. In the tire 10, the thin layer 72 disposed between the first ply 76 and the second ply 78 is made of a crosslinked rubber, like the thin layer 32 of the tire 8 shown in FIG. Moreover, as will be described later, the thin layer 72 has an appropriate tensile stress at 100% elongation. For this reason, when the tire 10 is twisted, the tire 10 has an appropriate torsional rigidity. In other words, the thin layer 72 absorbs the stress around the steering shaft that acts on the tire 10 while generating resistance to torsion. The tire 10 responds appropriately to steering. The tire 10 is excellent in stability. As described above, in the tire 10, the thin layer 72 can contribute to an increase in the longitudinal rigidity. Therefore, according to the present invention, it is possible to obtain the tire 10 in which the increase in the longitudinal rigidity is achieved while suppressing the increase in the torsional rigidity.

  In the tire 10, the tensile stress MR when the thin layer 72 is stretched at 100% modulus is 1.5 MPa or more and 3.0 MPa or less. By setting the tensile stress MR to 1.5 MPa or more, the thin layer 72 can contribute to the increase in longitudinal rigidity. Moreover, since the torsional rigidity is appropriately maintained, the tire 10 appropriately responds to steering. In this respect, the tensile stress MR is more preferably 1.8 MPa or more. As described above, the tire 10 is incorporated in the rear wheel 6 of the two-wheeled vehicle 2. In the two-wheeled vehicle 2, the rear wheel 6 mainly transmits the driving force to the road surface. Therefore, from the viewpoint of traction, the tensile stress MR is more preferably 2.0 MPa or more. By setting the tensile stress MR to 3.0 MPa or less, the thin layer 72 effectively absorbs the stress around the steering axis. Even in this case, since the torsional rigidity is appropriately maintained, the tire 10 appropriately responds to the steering. Since the increase in the longitudinal rigidity is appropriately suppressed, a good riding comfort is maintained. From this viewpoint, the tensile stress MR is preferably 2.5 MPa or less.

  In the present application, the tensile stress MR of the thin layer 72 is measured in the same manner as the thin layer 32 of the tire 8 shown in FIG.

  In FIG. 3, a solid line BLR represents a baseline. The base line BLR is a line that defines the rim diameter (see JATMA) of the rim 54 on which the tire 10 is mounted. The base line BLR extends in the axial direction. The double-headed arrow AR represents the height in the radial direction from the base line BLR to the end 90 of the thin layer 72. A double-headed arrow BR represents the height in the radial direction from the base line BLR to the end PR of the tread surface 74.

  In the tire 10, the ratio of the height AR to the height BR is preferably 0.7 or less. By setting this ratio to 0.7 or less, the thin layer 72 can effectively contribute to an increase in longitudinal rigidity. Since the tire 10 has high longitudinal rigidity, large traction can be obtained during acceleration. A large turning force can be obtained during turning. In this respect, the ratio is more preferably equal to or less than 0.5 and still more preferably equal to or less than 0.4. From the viewpoint of easy manufacturing of the tire 10 and the influence on the cost, this ratio is preferably 0.1 or more, and more preferably 0.3 or more.

  In FIG. 3, the double arrow TR represents the thickness of the thin layer 72. This thickness TR is measured along the equator plane.

  In the tire 10, the thickness TR is preferably 0.3 mm or greater and 2.0 mm or less. By setting the thickness TR to 0.3 mm or more, the thin layer 72 can effectively contribute to the increase in the longitudinal rigidity while suppressing the influence of the thin layer 72 on the torsional rigidity. In this respect, the thickness TR is more preferably 0.4 mm or more. By setting the thickness TR to 2.0 mm or less, an increase in the longitudinal rigidity is appropriately suppressed, so that a good riding comfort is maintained. In this respect, the thickness TR is more preferably 1.5 mm or less.

  In the two-wheeled vehicle 2 in FIG. 1, the front tire 8 in FIG. 2 is incorporated in the front wheel 4, and the rear tire 10 in FIG. 3 is incorporated in the rear wheel 6. As described above, in the front tire 8, an increase in longitudinal rigidity is achieved while suppressing an increase in torsional rigidity. Also in the rear tire 10, an increase in longitudinal rigidity is achieved while suppressing an increase in torsional rigidity. Therefore, also in the tire pair 12 including the front tire 8 and the rear tire 10, an increase in the longitudinal rigidity is achieved while suppressing the influence on the torsional rigidity. In the tire pair 12, a large traction is obtained during acceleration. A large turning force can be obtained during turning. Moreover, since the torsional rigidity is appropriately maintained, the tire pair 12 appropriately responds to steering. The tire pair 12 is excellent in stability.

  In the two-wheeled vehicle 2, the front wheels 4 mainly maintain the directionality, and the rear wheels 6 mainly transmit driving force. From this viewpoint, it is preferable that the torsional rigidity is more important than the longitudinal rigidity in the front tire 8, and the vertical rigidity is more important than the torsional rigidity in the rear tire 10.

  The front tire 8 employs the low modulus thin layer 32 and the rear tire 10 employs the high modulus thin layer 72 from the viewpoint that the torsional rigidity is emphasized in the front tire 8 and the longitudinal rigidity is emphasized in the rear tire 10. Is preferred. Specifically, the difference (MR−MF) between the tensile stress MR of the thin layer 72 of the rear tire 10 and the tensile stress MF of the thin layer 32 of the front tire 8 is preferably 0.2 MPa or more. From the viewpoint of rigidity balance, this difference is preferably 0.5 MPa or less.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A tire according to Example 1 having the basic configuration shown in FIG. 2 and shown in Table 1 below was obtained. The tire size was 120 / 70ZR17. This tire is a front tire. The absolute value of the angle formed with respect to the equator plane of the carcass cord (hereinafter, the cord angle) was 82 ° (degrees). The tensile stress MF at 100% elongation of the thin layer was 2.0 MPa. The thickness TF of the thin layer was 2.0 mm. The ratio (AF / BF) of the radial height AF from the base line BLF to the end of the thin layer to the radial height BF from the base line BLF to the end PF of the tread surface was 0.4.

[Comparative Example 1]
A tire of Comparative Example 1 was obtained in the same manner as in Example 1 except that the thin layer was not provided. The comparative example 1 is a conventional front tire.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as in Example 1 except that a thin layer was not provided and the cord angle was set to 60 °.

[Comparative Example 3]
A tire of Comparative Example 3 was obtained in the same manner as Example 1 except that a thin layer was provided outside the carcass.

[Example 2-6]
A tire of Example 2-6 was obtained in the same manner as in Example 1 except that the ratio (AF / BF) was as shown in Table 2 below.

[Example 7-10 and Comparative Example 4-5]
Tires of Examples 7-10 and Comparative Example 4-5 were obtained in the same manner as Example 1 except that the tensile stress MF was as shown in Table 3 below.

[Examples 11-16]
Tires of Examples 11-16 were obtained in the same manner as in Example 1 except that the thickness TF was as shown in Table 4 below.

[Examples 17-19 and Comparative Example 6]
Tires of Examples 17-19 and Comparative Example 6 were obtained in the same manner as Example 1 except that the cord angles were as shown in Table 5 below.

[Example 20]
A tire of Example 20 having the basic configuration shown in FIG. 3 and shown in Table 6 below was obtained. The tire size was 190 / 55ZR17. This tire is a rear tire. The absolute value of the angle formed with respect to the equator plane of the carcass cord (hereinafter, the cord angle) was 82 ° (degrees). The tensile stress MR at 100% elongation of the thin layer was 2.0 MPa. The thin layer had a thickness TR of 2.0 mm. The ratio (AR / BR) of the radial height AR from the base line BLR to the end of the thin layer to the radial height BR from the base line BLR to the end PR of the tread surface was 0.4.

[Comparative Example 7]
A tire of Comparative Example 7 was obtained in the same manner as in Example 20 except that the thin layer was not provided. The comparative example 7 is a conventional rear tire.

[Comparative Example 8]
A tire of Comparative Example 8 was obtained in the same manner as Example 20 except that a thin layer was not provided and the cord angle was 60 °.

[Comparative Example 9]
A tire of Comparative Example 9 was obtained in the same manner as Example 20 except that a thin layer was provided outside the carcass.

[Examples 21-26]
Tires of Examples 21 to 26 were obtained in the same manner as Example 20 except that the ratio (AF / BF) was as shown in Table 7 below.

[Examples 27-30 and Comparative Example 10-11]
Tires of Examples 27-30 and Comparative Example 10-11 were obtained in the same manner as Example 20 except that the tensile stress MR was as shown in Table 8 below.

[Examples 31-36]
Tires of Examples 31 to 36 were obtained in the same manner as Example 20 except that the thickness TR was as shown in Table 9 below.

[Examples 37-39 and Comparative Example 12]
Tires of Examples 37 to 39 and Comparative Example 12 were obtained in the same manner as Example 1 except that the cord angles were as shown in Table 10 below.

[Experiment 1 (Evaluation of front tire)]
[Maneuvering stability and ride comfort]
The prototype tire was mounted on the front wheel of a sports-type two-wheeled vehicle (4-cycle) with a displacement of 1000 cc and filled with air so that the internal pressure was 250 kPa. The size of the front wheel rim was 17 × MT3.50. The rear wheel was fitted with the tire of Comparative Example 7 and filled with air so that the internal pressure was 290 kPa. The size of the rear wheel rim was 17 × MT6.00. This motorcycle was run on a circuit course with asphalt on the road surface, and sensory evaluation was performed by the rider. The evaluation items are stability as steering stability, responsiveness, traction and turning force, and riding comfort. The results are shown in Tables 1 to 5 below as indices with 10 points being the perfect score. Larger numbers are preferable.

  As shown in Tables 1 to 5, the tires of the examples have higher evaluation than the tires of the comparative examples. From this evaluation result, the superiority of the present invention is clear.

[Experiment 2 (Rear Tire Evaluation)]
[Maneuvering stability and ride comfort]
The prototype tire was mounted on the rear wheel of a sports type two-wheeled vehicle (4-cycle) with a displacement of 1000 cc, and air was filled so that the internal pressure was 290 kPa. The size of the rear wheel rim was 17 × MT6.00. The front wheel was fitted with the tire of Comparative Example 1 and filled with air so that the internal pressure was 250 kPa. The size of the front wheel rim was 17 × MT3.50. This motorcycle was run on a circuit course with asphalt on the road surface, and sensory evaluation was performed by the rider. The evaluation items are stability as steering stability, responsiveness, traction and turning force, and riding comfort. The results are shown in Tables 6 to 10 below as indices with 10 points being the perfect score. Larger numbers are preferable.

  As shown in Tables 6 to 10, the tires of the examples have higher evaluation than the tires of the comparative examples. From this evaluation result, the superiority of the present invention is clear.

[Experiment 3 (Evaluation of tire pair)]
[Maneuvering stability and ride comfort]
As shown in Table 11 below, front tires and rear tires as prototype tires were respectively mounted on the front and rear wheels of a sports-type two-wheeled vehicle (4-cycle) having a displacement of 1000 cc. The front wheel was filled with air so that the internal pressure was 250 kPa. The size of the front wheel rim was 17 × MT3.50. The rear wheels were filled with air so that the internal pressure was 290 kPa. The size of the rear wheel rim was 17 × MT6.00. This motorcycle was run on a circuit course with asphalt on the road surface, and sensory evaluation was performed by the rider. The evaluation items are stability as steering stability, responsiveness, traction and turning force, and riding comfort. This result is shown in Table 11 as an index with a maximum of 10 points. Larger numbers are preferable.

  As shown in Table 11, the performance of the tire pair is improved by using the tire of the example. From this evaluation result, the superiority of the present invention is clear.

  The tire described above can be applied to various two-wheeled vehicles.

2 ... two-wheeled motor vehicle 4 ... front wheel 6 ... rear wheel 8 ... front tire 10 ... rear tire 12 ... tire pair 14, 54 ... rim 16, 56 ... tread 18, 58 ... Wing 20, 60 ... Side wall 22,62 ... Bead 24,64 ... Carcass 32,72 ... Thin layer 34,74 ... Tread surface 40,76 ... No. One ply 42, 78 ... Second ply 52 ... End of thin layer 32 90 ... End of thin layer 72

Claims (3)

A tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the tread, a pair of beads each positioned radially inward of the sidewall, the tread and the above A carcass spanned between one bead and the other bead along the inside of the sidewall, and a thin layer spanned between the one bead and the other bead along the carcass And
The carcass includes a first ply and a second ply located outside the first ply,
Each of the first ply and the second ply includes a plurality of cords arranged in parallel,
The absolute value of the angle that each cord makes with the equator plane is 70 ° or more,
The thin layer is located between the first ply and the second ply;
This thin layer consists of crosslinked rubber,
A pneumatic tire in which the tensile stress at 100% elongation of the thin layer is 1.5 MPa or more and 3.0 MPa or less.   The pneumatic tire according to claim 1, wherein the thin layer has a thickness of 0.3 mm to 2.0 mm.   The ratio of the radial height from the bead base line to the end of the thin layer to the radial height from the bead base line to the end of the tread surface is 0.7 or less. Pneumatic tires.

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