JP2018192902A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that can reduce rolling resistance and has excellent durability.SOLUTION: In a neumatic tire 2, a belt 16 comprises an inner layer 46 and an outer layer 48. The inner layer 46 and the outer layer 48 comprise a belt cord and topping rubber, respectively. With respect to a tire equatorial plane, an absolute value of an inclination angle θ1 of the belt cord of the inner layer 46 is 28(°) or more and 38(°) or less, and an absolute value of an inclination angle θ2 of the belt cord of the outer layer 48 is 16(°) or more and 22 (°) or less. A band 18 comprises a band cord and topping rubber wound around in a circumferential direction. When the number of cross sections of the band cord included in a width in an axial direction 1 (cm) is defined as a unit number, an expansion rate is 0.06 or less when a tensile load of 660 (N) is applied to the band cord of the unit number.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  Japanese Patent Application Laid-Open No. 2015-131507 discloses a tire in which the inclination angle of the belt cord is increased. In this tire, the belt includes an inner layer and an outer layer. In the inner layer and the outer layer, the absolute value of the inclination angle of the belt cord is the same, and is not less than 35 (°) and not more than 55 (°). Thereby, rolling resistance is reduced.

JP2015-131507A

  As a result of various tests conducted by the inventors, in a tire in which the absolute value of the inclination angle of the belt cord is the same in the inner layer and the outer layer, lateral force deviation (hereinafter referred to as LFD) that occurs during rotation occurs. It was confirmed to be large. This increase in LFD increases the rolling resistance of the tire. Through various tests, it was confirmed that LDF was reduced by providing a difference in the absolute value of the inclination angle of the belt cord between the inner layer and the outer layer. And in the tire which provided the difference of this inclination angle, it was confirmed that rolling resistance is reduced.

  However, the belt plays a role of suppressing and restraining the diameter growth of the rotating tire. In a tire with a difference in inclination angle, the binding force borne by the belt cord having a small absolute value of the inclination angle with respect to the equator plane is larger than the binding force borne by the belt cord having a large absolute value of the inclination angle. large. For this reason, a belt cord having a small absolute value of the inclination angle is more likely to be damaged than a belt cord having a large absolute value of the inclination angle. This tire has room for improvement in durability.

  An object of the present invention is to provide a pneumatic tire that has reduced rolling resistance and excellent durability.

The pneumatic tire according to the present invention includes a tread whose outer surface forms a tread surface, a belt positioned inside the tread in the radial direction, and a band positioned between the tread and the belt. The belt includes an inner layer and an outer layer laminated on a radially outer side of the inner layer. Each of the inner layer and the outer layer includes a belt cord and a topping rubber. The inclination direction of the belt cord of the inner layer with respect to the equator plane is opposite to the inclination direction of the belt cord of the outer layer.
The absolute value of the inclination angle θ1 of the belt cord of the inner layer is not less than 28 (°) and not more than 38 (°) with respect to the equator plane, and the absolute value of the inclination angle θ2 of the belt cord of the outer layer is 16 (° ) Or more and 22 (°) or less.
The band includes a band cord wound in the circumferential direction and a topping rubber. The number of cross sections of the band cord included in the width in the axial direction 1 (cm) is the unit number. At this time, the elongation rate when a tensile load of 660 (N) is applied to this number of band cords is 0.06 or less.

Preferably, the complex elastic modulus Eb ^* of the topping rubber of the band is smaller than the complex elastic modulus E2 ^* of the topping rubber of the outer layer.

Preferably, the complex elastic modulus Eb ^* of the topping rubber of the band is 4.5 (MPa) or more and 7.0 (MPa) or less. The complex elastic modulus E2 ^* of the topping rubber of the outer layer is 7.5 (MPa) or more and 14.5 (MPa) or less.

  Preferably, the product of the breaking strength Fb (N) of one band cord and the number of units of the band cord is 1800 (N) or more.

  Preferably, the band cord is formed by twisting a cord made of an aramid fiber and a cord made of a nylon fiber.

  Preferably, the band cord is formed by twisting a cord made of an aramid fiber and a cord made of a polyester fiber.

  Preferably, in the axial direction, the end of the band is located outside the end of the belt. The distance from the end of the belt to the end of the band is 2 (mm) or more and 10 (mm) or less.

  Preferably, a first rubber layer is laminated between the end of the belt and the carcass.

  Preferably, the thickness of the first rubber layer is 0.2 (mm) or more and 1.0 (mm) or less.

  Preferably, a second rubber layer is laminated between the inner layer and the end of the outer layer.

  Preferably, the thickness of the second rubber layer is 0.2 (mm) or more and 1.0 (mm) or less.

  In the tire belt according to the present invention, the absolute value of the inclination angle of the belt cord of the inner layer is different from the absolute value of the inclination angle of the belt cord of the outer layer. Thereby, LFD is reduced and rolling resistance is reduced. Furthermore, the band cord extending in the circumferential direction compensates for the restraint in the circumferential direction and the radial direction due to the belt cord having a small absolute angle of inclination. This tire has excellent durability while reducing rolling resistance.

FIG. 1 is a cross-sectional view illustrating a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an explanatory view showing a part of the belt and a part of the band of the tire of FIG. FIG. 3 is a partially enlarged view of the tire of FIG. FIG. 4 is a cross-sectional view illustrating a pneumatic tire according to another embodiment of the present invention.

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

  FIG. 1 shows a pneumatic tire 2. In FIG. 1, the direction perpendicular to the paper surface is the circumferential direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. A dashed-dotted line CL in FIG. 1 represents the equator plane of the tire 2. A straight line BL indicates a bead base line. The shape of the tire 2 is symmetric with respect to the equator plane CL except for the tread pattern. The bead base line is a straight line that extends in the axial direction of the tire 2 through the position of the bead diameter defined by the standard.

  The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of beads 8, a pair of clinch 10, a carcass 12, a pair of load support layers 14, a belt 16, a band 18, an inner liner 20, and a pair of chafers 22. I have. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 24 that contacts the road surface. A groove 26 is carved in the tread surface 24. The groove 26 forms a tread pattern. The tread 4 includes a base layer 28 and a cap layer 30. The base layer 28 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 28 is natural rubber. The cap layer 30 is located on the radially outer side of the base layer 28. The cap layer 30 is laminated on the base layer 28. The cap layer 30 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  Each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. A radially outer end of the sidewall 6 is joined to the tread 4. The radially inner end of the sidewall 6 is joined to the clinch 10. This sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 6 is located outside the carcass 12 in the axial direction. The side wall 6 prevents the carcass 12 from being damaged.

  Each bead 8 is located inside the sidewall 6 in the radial direction. The bead 8 is located inside the sidewall 6 in the axial direction. The bead 8 includes an inner part 32 and an outer part 34. The inner part 32 is located inside the outer part 34 in the axial direction.

  The inner part 32 includes an inner core 36 and an inner apex 38. The inner core 36 has a ring shape. The inner core 36 includes a non-stretchable wire wound in the circumferential direction. A typical material for this wire is steel. The inner apex 38 is made of a highly hard crosslinked rubber. The inner apex 38 covers the inner core 36. The inner apex 38 extends radially outward from the inner core 36. The radially outer portion of the inner apex 38 has a tapered shape.

  The outer part 34 includes an outer core 40 and an outer apex 42. The outer core 40 has a ring shape. The outer core 40 includes a non-stretchable wire wound in the circumferential direction. A typical material for this wire is steel. The outer apex 42 is made of a highly hard crosslinked rubber. The outer apex 42 covers the outer core 40. The outer apex 42 extends radially outward from the outer core 40. The radially outer portion of the outer apex 42 has a tapered shape.

  The radially inner part of the inner part 32 and the radially inner part of the outer part 34 are joined. As a result, the inner apex 38 and the outer apex 42 are integrated.

  Each clinch 10 is located radially inward from the sidewall 6. The clinch 10 is located outside the beads 8 and the carcass 12 in the axial direction. The clinch 10 is made of a crosslinked rubber having excellent wear resistance. The clinch 10 abuts against the flange of the rim when the tire 2 is incorporated into a rim (not shown).

  The carcass 12 includes a carcass ply 44. The carcass ply 44 is bridged between the pair of beads 8. The carcass ply 44 is along the tread 4 and the sidewall 6. An end 44 a of the carcass ply 44 is sandwiched between the inner part 32 and the outer part 34. The structure of the carcass 12 is referred to as an insert structure. The carcass 12 includes a single carcass ply 44. The number of carcass plies 44 is not limited to one. The carcass 12 may be composed of two or more carcass plies 44.

  Although not shown, the carcass ply 44 includes a large number of carcass cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each carcass cord with respect to the equator plane is 75 (°) to 90 (°). In other words, the carcass 12 has a radial structure. The carcass cord is made of an organic fiber. Examples of preferable organic fibers include polyethylene terephthalate fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, aramid fiber, and polyketone fiber.

  Each load support layer 14 is located on the inner side in the axial direction of the sidewall 6. The load support layer 14 is located between the carcass 12 and the inner liner 20 in the axial direction. The load support layer 14 may be positioned inside the carcass 12 and the inner liner 20 in the axial direction. The load support layer 14 is located between the tread 4 and the bead 8 in the radial direction. The load support layer 14 tapers inward in the radial direction and also tapers outward. The load support layer 14 is curved in a shape protruding outward in the axial direction. The load support layer 14 is along the carcass 12. The load support layer 14 has a similar shape to a crescent moon. The load support layer 14 is made of a highly hard crosslinked rubber.

  When the tire 2 is punctured, the load support layer 14 supports the load. The load supporting layer 14 allows the tire 2 to travel a certain distance even in a puncture state. In other words, the tire 2 can be run flat. The tire 2 is a so-called run flat tire. The tire 2 is a side reinforcing type.

  The belt 16 is located inside the tread 4 in the radial direction. The belt 16 is laminated with the carcass 12. The belt 16 reinforces the carcass 12. The belt 16 includes an inner layer 46 and an outer layer 48. Each of the inner layer 46 and the outer layer 48 extends from the vicinity of one end of the tread 4 to the vicinity of the other end in the axial direction. In the axial direction, the width of the inner layer 46 is slightly larger than the width of the outer layer 48.

  The band 18 is located on the radially outer side of the belt 16. The band 18 extends from the vicinity of one end of the tread 4 to the vicinity of the other end in the axial direction. In the axial direction, the width of the band 18 is greater than or equal to the width of the belt 16. The band 18 covers the belt 16. The band 18 and the belt 16 constitute a reinforcing layer.

  The inner liner 20 extends along the carcass 12 and the load support layer 14. The inner liner 20 is laminated inside the carcass 12 in the radial direction. The inner liner 20 is laminated inside the load support layer 14 in the axial direction. The inner liner 20 may be laminated outside the load support layer 14 in the axial direction. The inner liner 20 may be positioned between the load support layer 14 and the carcass 12 in the axial direction. The inner liner 20 is made of a crosslinked rubber. The inner liner 20 is made of rubber having excellent air shielding properties. The inner liner 20 holds the internal pressure of the tire 2.

  The chafer 22 is located in the vicinity of the bead 8. The chafer 22 extends radially inward from the inner side in the axial direction of the inner core 36 and reaches the beat toe. The chafer 22 extends axially outward from the bead toe 50 on the radially inner side of the inner core 36 and the outer core 40. The chafer 22 is integrated with the clinch 10. The material of the chafer 22 is the same as that of the clinch 10. When the tire 2 is incorporated in the rim, the chafer 22 comes into contact with the rim sheet. By this contact, the vicinity of the bead 8 is protected. The chafer 22 may be made of cloth and rubber impregnated in the cloth.

  FIG. 2 schematically shows part of the belt 16 and part of the band 18. The vertical direction in FIG. 2 is the circumferential 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 radial direction of the tire 2.

  The inner layer 46 of the belt 16 includes a large number of belt cords 52 and a topping rubber 54 arranged in parallel. Each belt cord 52 is inclined with respect to the equator plane. A double-headed arrow θ1 represents an inclination angle of the belt cord 52 of the inner layer 46.

  The outer layer 48 includes a plurality of belt cords 56 and a topping rubber 58 which are arranged in parallel. Each belt cord 56 is inclined with respect to the equator plane. A double-headed arrow θ2 represents an inclination angle of the belt cord 56 of the outer layer 48.

  In the tire 2, the inclination direction of the belt cord 52 of the inner layer 46 is opposite to the inclination direction of the belt cord 56 of the outer layer 48 with respect to the equator plane. The absolute value of the tilt angle θ1 is larger than the absolute value of the tilt angle θ2. A preferred material for the belt cord 52 and the belt cord 56 is steel. The belt cord 52 and the belt cord 56 may be made of organic fibers.

In the tire 2, the topping rubber 54 of the inner layer 46 and the topping rubber 58 of the outer layer 48 are made of the same crosslinked rubber. The complex elastic modulus E1 ^* of the topping rubber 54 of the inner layer 46 and the complex elastic modulus E2 ^* of the topping rubber 58 of the outer layer 48 are set to the same size. The topping rubber 54 of the inner layer 46 and the topping rubber 58 of the outer layer 48 may be made of different crosslinked rubbers.

The band 18 includes a band cord 60 and a topping rubber 62. The topping rubber 62 is made of a crosslinked rubber having a complex elastic modulus Eb ^* . The band cord 60 is wound spirally. In other words, these band cords 60 are wound substantially in the circumferential direction. The band cord 60 has a so-called jointless structure. The angle of the band cord 60 with respect to the circumferential direction is 5 (°) or less, and further 2 (°) or less. The belt 16 is restrained by the band cord 60. The band 18 suppresses lifting of the belt 16.

  The band cord 60 is made of an organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, aramid fibers, and polyethylene naphthalate fibers. The band cord 60 may be composed of a plurality of organic fibers. In the example of the tire 2, the band cord 60 is formed by twisting an aramid cord made of an aramid fiber and a nylon cord made of a nylon fiber.

  FIG. 3 shows an enlarged view of the end 16a of one belt 16 in the axial direction and its periphery. As shown in FIG. 3, the tire 2 includes a pair of first rubber layers 64, a pair of second rubber layers 66, and a pair of third rubber layers 68.

  A part of each first rubber layer 64 is located between the carcass 12 and the end 46a of the inner layer 46 in the radial direction. In the axial direction, the end 64 e of the first rubber layer 64 is located outside the end 46 e of the inner layer 46. The first rubber layer 64 extends along the carcass 12. The first rubber layer 64 is made of a crosslinked rubber.

  A part of each second rubber layer 66 is located between the inner layer 46 and the end 48a of the outer layer 48 in the radial direction. In the axial direction, the end 66 e of the second rubber layer 66 is located outside the end 48 e of the outer layer 48. The second rubber layer 66 extends along the inner layer 46. The second rubber layer 66 is made of a crosslinked rubber.

  A part of each third rubber layer 68 is located between the belt 16 and the band 18 in the radial direction. In the axial direction, the end 68 e of the third rubber layer 68 is located outside the end 46 e of the inner layer 46. The third rubber layer 68 is located between the carcass 12 and the band 18 outside the end 46e of the inner layer 46 in the axial direction. In the axial direction, the end 68 e of the third rubber layer 68 is located outside the end 18 e of the band 18. The third rubber layer 68 is made of a crosslinked rubber.

  A double arrow D1 in FIG. 3 represents the distance from the end 16e of the belt 16 to the end 18e of the band 18. In the tire 2, the distance D <b> 1 is measured as the distance from the end 46 e of the inner layer 46 to the end 18 e of the band 18. This distance D1 is the distance from the normal drawn at the end 46e to the normal drawn at the end 18e. A double arrow t1 represents the thickness of the first rubber layer 64. This thickness t1 is measured at the position of the end 46e of the inner layer 46. A double arrow t <b> 2 represents the thickness of the second rubber layer 66. The thickness t2 is measured at the position of the end 48e of the outer layer 48.

  When a load is applied to the tire 2 and the tire 2 is rotated, an axial side force is generated in the tire 2. This side force occurs even when the camber angle and the slip angle are zero. This side force is referred to as lateral force deviation (also referred to as LFD). This LFD can be reduced by making the absolute value of the inclination angle θ1 of the belt cord 52 of the inner layer 46 different from the absolute value of the inclination angle θ2 of the belt cord 56 of the outer layer 48. In the tire 2 in which the difference between the absolute value of the inclination angle θ1 and the absolute value of the inclination angle θ2 is large, the LFD is small. The tire 2 having a small LFD has a reduced rolling resistance.

  In the tire 2, the absolute value of the inclination angle θ1 of the belt cord 52 of the inner layer 46 is different from the absolute value of the inclination angle θ2 of the belt cord 56 of the outer layer 48. Thereby, in this tire 2, LFD is reduced and rolling resistance is reduced.

  In the belt 16, the belt cord 52 of the inner layer 46 and the belt cord 56 of the outer layer 48 exert a binding force in the radial direction and the circumferential direction. Since the absolute value of the inclination angle θ2 is smaller than the absolute value of the inclination angle θ1, the restraining force that the belt cord 56 bears is larger than the restraining force that the belt cord 52 bears. For this reason, the tension acting on the belt cord 56 of the outer layer 48 is greater than that of the belt cord 52 of the inner layer 46. The belt cord 56 of the outer layer 48 is more likely to be damaged such as breakage than when the inclination angle θ1 and the inclination angle θ2 are the same.

  In the tire 2, the band cord 60 extending in the circumferential direction restrains the belt 16. This band 18 covers the outer layer 48. The band 18 together with the belt 16 exhibits a restraining force in the radial direction and the circumferential direction. The band cord 60 exerts a binding force in cooperation with the belt cord 52 and the belt cord 56. The band cord 60 reduces the binding force that the belt cord 56 bears. The band 18 contributes to improving the durability of the belt cord 56. This band 18 contributes to the improvement of the durability of the tire 2.

  From the viewpoint of improving the durability of the tire 2, it is preferable that the elongation percentage of the band cord 60 is small. In the tire 2 having excellent durability, the inclination angle θ2 of the belt cord 56 of the outer layer 48 can be further reduced. As a result, the difference between the absolute value of the inclination angle θ2 and the absolute value of the inclination angle θ1 of the belt cord 52 of the inner layer 46 can be increased. The tire 2 can reduce rolling resistance without impairing durability. Here, the number of cross sections of the band cord 60 included in the width of the band 18 in the axial direction 1 (cm) is defined as the unit number. At this time, from the viewpoint of the durability of the tire 2 and the reduction in rolling resistance, the elongation rate when a tensile load of 660 (N) is applied to the unit number of band cords 60 is preferably 0.06 or less (6 % Or less).

  In this invention, elongation rate is measured based on the test of elongation rate at the time of fixed load of JIS-L1017 "chemical fiber tire cord test method". This elongation rate is obtained as the elongation rate of the band cord 60 when a load of 660 (N) is applied to the unit number of band cords 60. This elongation rate is calculated | required as a ratio of the elongation amount with respect to the original length.

  When this number of units includes a numerical value after the decimal point, the temporary elongation rate is obtained using the temporary unit number obtained by rounding off the numerical value of the first decimal place. The temporary elongation rate is multiplied by the ratio of the unit number to the temporary unit number to obtain the elongation rate.

  Similarly, from the viewpoint of reducing the durability and rolling resistance of the tire 2, the product of the breaking strength Fb (N) per unit of the band cord 60 and the number of units is preferably 1800 (N) or more. .

  In the present invention, the breaking strength Fb (N) is obtained as a tensile load when the band cord 60 is broken. This tensile load is measured based on the tensile strength and elongation test of JIS-L1017 “Test method for chemical fiber tire cord”.

  The band cord 60 of the tire 2 is formed by twisting a cord made of aramid fiber and a cord made of nylon fiber. The cord made of this aramid fiber contributes to suppression of the elongation of the band cord 60. The cord made of nylon fiber is excellent in flexibility and contributes to improving the durability of the band cord 60. The band cord 60 is suppressed in elongation and also excellent in durability. Here, although an aramid fiber and a nylon fiber were demonstrated to the example, it is not restricted to this. The band cord 60 is preferably formed by twisting a cord for suppressing elongation and a cord having excellent flexibility. For example, the belt cord 56 may be formed by twisting a cord made of an aramid fiber and a cord made of a polyester fiber.

  In the tire 2 in which the absolute value of the inclination angle θ1 of the belt cord 52 is large, the restraining force that the belt cord 56 of the outer layer 48 bears is large. In the tire 2, a large burden is applied to the belt cord 56 of the outer layer 48. From the viewpoint of improving the durability of the tire 2, the absolute value of the inclination angle θ1 is 38 (°) or less, and preferably 36 (°) or less.

  On the other hand, in the tire 2 having a large inclination angle difference between the absolute value of the inclination angle θ1 and the absolute value of the inclination angle θ2 of the belt cord 56 of the outer layer 48, the LFD is small. In the tire 2, the rolling resistance is small. By increasing the inclination angle θ1, this inclination angle difference can be increased. From the viewpoint of reducing rolling resistance, the absolute value of the inclination angle θ1 is 28 (°) or more, and preferably 30 (°) or more.

  Similarly, the inclination angle difference can be increased by reducing the inclination angle θ2. From the viewpoint of reducing rolling resistance, the absolute value of the inclination angle θ2 of the belt cord 56 is preferably small. The absolute value of the inclination angle θ2 is 22 (°) or less, preferably 21 (°) or less. On the other hand, the tire 2 having a large absolute value of the inclination angle θ <b> 2 contributes to improvement of the durability of the belt cord 56. From the viewpoint of durability, the absolute value of the inclination angle θ2 is 16 (°) or more, preferably 17 (°) or more.

In the tire 2, the complex elastic modulus Eb ^* of the topping rubber 62 of the band 18 is smaller than the complex elastic modulus E2 ^* of the topping rubber 58 of the outer layer 48. As a result, compared to the case where the complex elastic modulus Eb ^* is larger than the complex elastic modulus E2 ^* , the acting stress is more easily dispersed between the band cord 60 and the belt cord 56 of the outer layer 48. This distribution of stress contributes to the reduction of the rolling resistance of the tire 2.

The band 18 having a large complex elastic modulus Eb ^* contributes to an improvement in the binding force of the belt 16. From this viewpoint, the complex elastic modulus Eb ^* is preferably 4.5 (MPa) or more, more preferably 5.0 (MPa) or more, and particularly preferably 5.5 (MPa) or more. . On the other hand, in the band 18 having a small complex elastic modulus Eb ^* , the adhesion between the topping rubber 62 and the band cord 60 is excellent. From this viewpoint, the complex elastic modulus Eb ^* is preferably 7.0 (MPa) or less, and more preferably 6.5 (MPa) or less.

The outer layer 48 having a large complex elastic modulus E2 ^* contributes to improving the durability of the belt cord 56. From this viewpoint, the complex elastic modulus E2 ^* is preferably 7.5 (MPa) or more, and more preferably 8.5 (MPa) or more. On the other hand, the outer layer 48 having a small complex elastic modulus E2 ^* has excellent adhesion between the topping rubber 58 and the belt coat. From this viewpoint, the complex elastic modulus E2 ^* is preferably 14.5 (MPa) or less, and more preferably 13.5 (MPa) or less.

  In the tire 2 in which the inclination angle θ1 and the inclination angle θ2 are different, when rolling, the inner layer 46 and the outer layer 48 have different deformation directions and deformation sizes. In particular, in the tire 2 in which the absolute value of the inclination angle θ1 and the absolute value of the inclination angle θ2 are different, the difference in the amount of deformation in the axial direction is larger than that of a tire of the same size. For this reason, the shearing force between the inner layer 46 and the outer layer 48 tends to increase in the axial direction. In the tire 2, the shearing force is reduced by the band 18 restraining the inner layer 46 and the outer layer 48. The band 18 contributes to a reduction in rolling resistance by reducing the shear force. From the viewpoint of reducing the shearing force, the distance D1 from the end 16e of the belt 16 to the end 18e of the band 18 is preferably 2 (mm) or more, and more preferably 3 (mm) or more. On the other hand, the tire 2 having a large distance D1 increases in weight. From the viewpoint of weight reduction, the distance D1 is preferably 10 (mm) or less, and more preferably 7 (mm) or less.

  Since the tire 2 includes the first rubber layer 64, shear deformation of the end portion 46a of the inner layer 46 is suppressed. By suppressing this shear deformation, rolling resistance is reduced. Further, the first rubber layer 64 suppresses the occurrence of peeling at the end 46 a of the inner layer 46. The first rubber layer 64 contributes to improving the durability of the tire 2. From the viewpoint of reducing the rolling resistance and improving the durability, the thickness t1 of the first rubber layer 64 is preferably 0.2 (mm) or more, and more preferably 0.4 (mm) or more.

  On the other hand, in the tire 2 in which the first rubber layer 64 is too thick, shear deformation of the end portion 46a of the inner layer 46 is promoted. By promoting this shear deformation, rolling resistance is increased. From the viewpoint of reducing the rolling resistance, the thickness t1 is preferably 1.0 (mm) or less, and more preferably 0.8 (mm) or less.

  Since the tire 2 includes the second rubber layer 66, shear deformation of the end portion 48a of the outer layer 48 is suppressed. By suppressing this shear deformation, rolling resistance is reduced. Further, the second rubber layer 66 suppresses the occurrence of peeling at the end 48 a of the outer layer 48. The second rubber layer 66 contributes to improving the durability of the tire 2. From the viewpoint of reducing the rolling resistance and improving the durability, the thickness t2 of the second rubber layer 66 is preferably 0.2 (mm) or more, and more preferably 0.4 (mm) or more.

  On the other hand, in the tire 2 in which the second rubber layer 66 is too thick, shear deformation of the end portion 48a of the outer layer 48 is promoted. By promoting this shear deformation, rolling resistance is increased. From the viewpoint of reducing the rolling resistance, the thickness t2 is preferably 1.0 (mm) or less, and more preferably 0.8 (mm) or less.

  The tire 2 includes a third rubber layer 68. In the axial direction, the end 68e of the third rubber layer 68 is located outside the end 16e of the belt 16. Thereby, the shear deformation of the end portion 16a of the belt 16 is suppressed. By suppressing this shear deformation, rolling resistance is reduced. Further, the occurrence of peeling at the end 16a of the belt 16 is suppressed. The third rubber layer 68 contributes to a reduction in rolling resistance and an improvement in durability of the tire 2.

In the present invention, the complex elastic modulus 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

  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.

  FIG. 4 shows another pneumatic tire 70 according to the present invention. Here, a configuration different from the tire 2 of FIG. 1 will be described. The description of the same configuration as the tire 2 is omitted. Moreover, in this description, about the structure similar to the tire 2, it demonstrates using the same code | symbol.

  The tire 70 includes a pair of clinches 72, a pair of beads 74, a carcass 76, a pair of chafers 78, and a pair of edge bands 80. The tire 70 does not include a load support layer.

  Each clinch 72 is located substantially inside the sidewall 6 in the radial direction. The clinch 72 is located outside the bead 74 and the carcass 76 in the axial direction. The clinch 72 is made of a crosslinked rubber having excellent wear resistance. The clinch 72 contacts the rim flange.

  Each bead 74 is located inside the clinch 72 in the axial direction. The bead 74 includes a core 82 and an apex 84 that extends radially outward from the core 82. The core 82 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 84 is tapered outward in the radial direction. The apex 84 is made of a highly hard crosslinked rubber.

  The carcass 76 includes a carcass ply 86. The carcass ply 86 is bridged between the beads 74 on both sides, and extends along the tread 4 and the sidewall 6. The carcass ply 86 is folded around the core 82 from the inner side toward the outer side in the axial direction. By this folding, the carcass ply 86 is formed with a main portion 86a and a folding portion 86b. The carcass ply 86 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 75 (°) to 90 (°). In other words, the carcass 76 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. The carcass 76 may be formed from two or more carcass plies 86.

  Each chafer 78 is located in the vicinity of the bead 74. When the tire 70 is incorporated into the rim, the chafer 78 contacts the rim sheet. By this contact, the vicinity of the bead 74 is protected. The chafer 78 is made of cloth and rubber impregnated in the cloth. As with the tire 2, the chafer 78 may be integrated with the clinch 72. Therefore, the material of the chafer 78 may be the same as the material of the clinch 72.

  Each edge band 80 is located radially outside the belt 16 and in the vicinity of the end 16 e of the belt 16. Although not shown, the edge band 80 is made of a cord and a topping rubber. The cord is wound in a spiral. The edge band 80 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 end 16e of the belt 16 is restrained by this cord. 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.

  Also in the tire 70, the absolute value of the inclination angle θ1 of the belt cord 52 of the inner layer 46 with respect to the equator plane is not less than 28 (°) and not more than 38 (°), and the inclination angle of the belt cord 56 of the outer layer 48 is The absolute value of θ2 is not less than 16 (°) and not more than 22 (°). Further, the elongation rate when a tensile load of 660 (N) is applied to the unit number of band cords 60 is 0.06 or less. Thereby, this tire 70 is excellent in durability while rolling resistance is reduced.

  Although not shown, the tire 70 may include a first rubber layer 64, a second rubber layer 66, and a third rubber layer 68, similar to the tire 2.

  In the tire 70, the edge band 80 restrains the end 16 a of the belt 16. Thereby, the shear deformation of the end portion 16a of the belt 16 is suppressed. By suppressing this shear deformation, rolling resistance is reduced. Further, the occurrence of peeling at the end 16a of the belt 16 is suppressed. The edge band 80 contributes to a reduction in rolling resistance and an improvement in durability of the tire 70.

  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 (run flat tire) having the basic configuration shown in FIG. 1 was obtained. The tire size was 245 / 45RF18. The absolute value of the inclination angle θ1 of the belt cord of the inner layer, the absolute value of the inclination angle θ2 of the belt cord of the outer layer, the complex elastic modulus Eb ^* of the topping rubber of the band, and the complex elastic modulus E2 of the topping rubber of the outer layer ^* Is as shown in Table 1. The tire band cord was formed by twisting a cord made of aramid fibers (1100 dtex) and a cord made of nylon fibers (940 dtex). The breaking strength Fb (N) per one of the band cords was 208 (N). In this band, the number of band cords per width (cm) was ten. The elongation rate when a tensile load of 660 (N) was applied to this unit number of band cords was 0.04. Each belt cord of the inner layer and the outer layer is made of steel, the breaking strength Fb (N) per one is 445 (N), and the unit number of belt cords per width (cm) Was nine.

[Comparative Example 1]
The absolute value of the inclination angle θ1 of the belt cord of the inner layer and the absolute value of the inclination angle θ2 of the belt cord of the outer layer were set to the same size. Otherwise, the tire was obtained in the same manner as the tire of Example 1.

[Example 2 and Comparative Example 2-3]
A tire was obtained in the same manner as the tire of Example 1, except that the absolute value of the inclination angle θ1 and the absolute value of the inclination angle θ2 were set as shown in Table 1.

[Example 3-6]
The absolute value of the inclination angle θ1, the absolute value of the inclination angle θ2, the complex elastic modulus Eb ^*, and the complex elastic modulus E2 ^* are set as shown in Table 2. Otherwise, a tire was obtained in the same manner as the tire of Example 1.

[Example 7 and Comparative Example 4]
A tire was obtained in the same manner as the tire of Example 1 except that the band cord was changed. Table 2 shows the elongation when a tensile load of 660 (N) was applied to the unit number of band cords.

[Evaluation of LFD]
Based on the uniformity test method defined in “JASO C607: 2000”, LFD was measured under the following conditions. The measurement results are shown in Tables 1 and 2. This measurement result is represented by an index with Comparative Example 1 as 100. The smaller the evaluation result, the higher the evaluation.
Internal pressure: 200 (kPa)
Load: 5.3 (kN)
Speed: 10 (km / h)

[Evaluation of rolling resistance]
Using a rolling resistance tester, the rolling resistance coefficient (RRC) of a tire incorporated in a regular rim was measured under the following measurement conditions.
Internal pressure: 250 (kPa)
Load: 6.28 (kN)
Speed: 80 (km / h)
This result is shown in the following Tables 1 and 2 as an index with Comparative Example 1 taken as 100. The evaluation result is preferably as the numerical value is smaller.

[Evaluation of durability]
The tire was incorporated into a regular rim and filled with air to an internal pressure of 230 kPa. A load of 8 (kN) was applied to the drum tester. In the traveling state at a speed of 100 km / h, the slip angle 0 (°) and the slip angle 5 (°) were switched 100 times every 9 seconds. After running, the belt cord was inspected for cuts. The results are shown in Tables 1 and 2.

  As shown in Tables 1 and 2, the tires of the examples are excellent in LFD, RRC, and durability. From this evaluation result, the superiority of the present invention is clear.

  The present invention can be widely applied to tires mounted on various vehicles.

2, 70 ... Tire 4 ... Tread 16 ... Belt 18 ... Band 24 ... Tread surface 46 ... Inner layer 48 ... Outer layer 52, 56 ... Belt cord 54, 58, 62 ... topping rubber 60 ... band cord 64 ... first rubber layer 66 ... second rubber layer 68 ... third rubber layer

Claims (11)

A tread whose outer surface forms a tread surface; a belt positioned radially inward of the tread; and a band positioned between the tread and the belt;
The belt comprises an inner layer and an outer layer laminated radially outward of the inner layer;
Each of the inner layer and the outer layer includes a belt cord and a topping rubber, and the inclination direction of the belt cord of the inner layer with respect to the equator plane is opposite to the inclination direction of the belt cord of the outer layer. ,
With respect to the equator plane, the absolute value of the inclination angle θ1 of the belt cord of the inner layer is not less than 28 (°) and not more than 38 (°), and the absolute value of the inclination angle θ2 of the belt cord of the outer layer is 16 (° ) Or more and 22 (°) or less,
The band is provided with a band cord wound in the circumferential direction and a topping rubber,
When the number of cross-sections of the band cord included in the width of 1 (cm) in the axial direction is the unit number, the elongation rate when a tensile load of 660 (N) is applied to the band cord of this unit number is 0. A pneumatic tire that is 06 or less. The tire according to claim 1, wherein the complex elastic modulus Eb ^* of the topping rubber of the band is smaller than the complex elastic modulus E2 ^* of the topping rubber of the outer layer. The complex elastic modulus Eb ^* of the topping rubber of the band is 4.5 (MPa) or more and 7.0 (MPa) or less, and the complex elastic modulus E2 ^* of the topping rubber of the outer layer is 7.5 (MPa) or more and 14 The tire according to claim 2, wherein the tire is 0.5 (MPa) or less.   The tire according to any one of claims 1 to 3, wherein a product of one breaking strength Fb (N) of the band cord and the number of units of the band cord is 1800 (N) or more.   The tire according to any one of claims 1 to 4, wherein the band cord is formed by twisting a cord made of an aramid fiber and a cord made of a nylon fiber.   The tire according to any one of claims 1 to 4, wherein the band cord is formed by twisting a cord made of an aramid fiber and a cord made of a polyester fiber. In the axial direction, the end of the band is located outside the end of the belt,
The tire according to any one of claims 1 to 6, wherein a distance from an end of the belt to an end of the band is 2 (mm) or more and 10 (mm) or less.   The tire according to any one of claims 1 to 7, wherein a first rubber layer is laminated between an end portion of the belt and the carcass.   The tire according to claim 8, wherein the thickness of the first rubber layer is 0.2 (mm) or more and 1.0 (mm) or less.   The tire according to any one of claims 1 to 9, wherein a second rubber layer is laminated between the inner layer and an end of the outer layer.   The tire according to claim 10, wherein the thickness of the second rubber layer is 0.2 (mm) or more and 1.0 (mm) or less.

Images