JP2017190002A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire 2 achieving steering stability and riding comfort while suppressing an increase in conicity.SOLUTION: A tire 2 comprises a band 32 including a spirally wound belt-shaped ply 64. In a cross section of the band 32, with respect to a cross sectional width of the belt-shaped ply 64, a ratio of interval between a cross section of one belt-shaped ply 64 and a cross section of another belt-like ply 64 is between 0 and 1. An interval on a second end 62b of a belt 18 is greater than an interval on a first end 62a of the belt 18. A rim 4 for this tire 2 comprises a first sheet 72a and a second sheet 72b. Provided that a rim diameter of the rim 4 in the first sheet 72a is defined to be a first rim diameter, while a rim diameter of the rim 4 in the second sheet 72b is defined to be a second rim diameter, a nominal D2 of the second rim diameter is greater than a nominal D1 of the first rim diameter in the tire 2.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a pneumatic tire. More specifically, the present invention relates to a side reinforcing type run flat tire.

  The development of highway networks and the advancement of vehicle performance are progressing. Vehicles tend to run for a long time at high speeds. Tires to be mounted on vehicles are being developed with an emphasis on improving handling stability, ride comfort and high-speed durability.

  In recent years, run-flat tires having a load support layer inside a sidewall have been developed and are becoming popular. For this support layer, a highly hard crosslinked rubber is used. This run flat tire is called a side reinforcement type.

  In this type of run-flat tire, when the internal pressure is reduced by puncture, the support layer supports the vehicle weight. Run-flat tires can travel a certain distance even in a puncture state. A vehicle equipped with this run flat tire does not require a spare tire. This run flat tire contributes to securing the vehicle interior space. Examples of such tires are disclosed in Japanese Patent Application Laid-Open Nos. 2008-155855 and 2013-071468.

  The tire is incorporated into the rim. In this assembly, the bead portion of the tire is fitted to the rim. The portion of the rim where the bead portion is fitted is called a bead seat. Based on the outer diameter of the bead seat, the rim diameter of the rim is expressed.

  The shape of the tire is usually symmetrical with respect to the equator plane except for the tread pattern. That is, the length from one side wall to the bead (hereinafter referred to as the first side portion) is equal to the length from the other side wall to the bead (hereinafter referred to as the second side portion). is there. In the rim to which this tire is attached, the left and right rim diameters are the same.

  In a four-wheeled vehicle, tires are arranged on the right side portion and the left side portion of the vehicle. For this reason, in the tire used for a four-wheeled vehicle, the configuration may be changed between a portion located inside and a portion located outside in the width direction of the vehicle. An asymmetric tread pattern is typical.

  The length of the side portion affects the tire deflection. The long side part contributes to bending, and the short side part contributes to rigidity. Therefore, for example, by configuring the first side portion to be longer than the second side portion, the left and right deflection of the tire may be controlled, and improvement of the tire performance may be studied. Examples of this study are disclosed in, for example, Japanese Patent Laid-Open Nos. 06-092104 and 05-139109.

  In a tire configured such that the first side portion is longer than the second side portion, the positions of the left and right beads are different. For this tire, a rim configured to have different left and right rim diameters is used. This tire is also called a different diameter bead type.

JP 2008-155855 A JP 2013-071468 A Japanese Patent Laid-Open No. 06-092104 JP 05-139109 A

  In the run flat tire, the support layer is hard. This support layer contributes to steering stability. However, this tire is inferior in riding comfort compared to a normal tire without this support layer.

  A run-flat tire is required to be able to travel a certain distance even in a punctured state. For this reason, the support layer has a considerable thickness. This tire is much heavier than a normal tire. A large mass affects the rolling resistance of the tire.

  In a tire mounted on a vehicle, heat is more likely to be accumulated in a portion located on the inner side in the width direction of the vehicle than a portion located on the outer side. Heat affects tire durability. Since the run-flat tire is provided with a support layer, heat is likely to accumulate. In this tire, the support layer provided for traveling in a puncture state (hereinafter, run-flat traveling) may affect the durability.

  As described above, the short side portion contributes to rigidity. The short side part invites a small volume. The side portion having a small volume contributes to weight reduction, and heat hardly accumulates on the side portion. Therefore, if the run-flat tire is of a different diameter bead type, there is a possibility that durability can be improved while maintaining both the steering stability and the ride comfort while appropriately maintaining the rigidity of the tire. However, when a tire of different diameter bead type is filled with air, there is a difference in the inflation state between a portion having a small rim diameter and a portion having a large rim diameter. There is a problem that the grounding shape tends to be distorted. In this tire, there is a difference between the outer diameter of the portion having a small rim diameter and the outer diameter of the portion having a large rim diameter, and there is a possibility that a large conicity is generated. If the rigidity of the long side portion is increased in order to suppress the increase in conicity, the ride comfort is lowered.

  An object of the present invention is to provide a pneumatic tire in which improvement in handling stability and riding comfort is achieved while suppressing an increase in conicity.

  The pneumatic tire according to the present invention is used by being mounted on a rim. The tire includes a tread, a first sidewall, a second sidewall, a first bead, a second bead, a carcass, a belt, a support layer, and a band. The first sidewall extends substantially inward in the radial direction from the first end of the tread. The second sidewall extends substantially inward in the radial direction from the second end of the tread. The first bead is located radially inward of the first sidewall. The second bead is located radially inward of the second sidewall. The carcass bridges between the first bead and the second bead along the inside of the first sidewall, the tread, and the second sidewall. The belt is laminated with the carcass on the inner side in the radial direction of the tread. The support layer is located on the inner side in the axial direction of the carcass on the second sidewall side. The band is located between the belt and the tread and covers the belt. The band includes a belt-like ply spirally wound on the outer side in the radial direction of the belt. The belt-like ply includes a band cord. The cross section of the band includes a large number of cross sections of the band-like plies arranged in parallel in the axial direction. In the cross section of the band, the ratio of the interval between the cross section of one belt ply and the cross section of another belt ply located next to the cross section of the single belt ply to the width of the cross section of the belt ply is 0 or more 1 or less. The interval on the second end side of the belt is larger than the interval on the first end side of the belt. The rim includes a first sheet on which the first bead portion is fitted, and a second sheet on which the second bead portion is fitted. When the rim diameter of the rim in the first seat is the first rim diameter and the rim diameter of the rim in the second seat is the second rim diameter, the designation of the second rim diameter in the tire is the first rim diameter. It is larger than the nominal rim diameter.

  Preferably, in this pneumatic tire, when the point where the axial width of the belt is equally divided into three is defined as the point PB1 and the point PB2 from the first end side of the belt, In the zone from one end to the point PB1, the ratio of the interval to the width of the cross section of the band-like ply in the cross section of the band is 0 or more and 0.2 or less. In the zone from the point PB1 to the point PB2, the ratio of the distance to the width of the cross-section of the band-like ply in the cross-section of the band is 0.2 or more and 0.8 or less. In the zone from the point PB2 to the second end of the belt, the ratio of the distance to the width of the cross section of the band-like ply in the cross section of the band is 0.8 or more and 1 or less.

  Preferably, in this pneumatic tire, the difference between the nominal diameter of the second rim and the nominal diameter of the first rim is 1 inch or more and 3 inches or less.

  Preferably, in this pneumatic tire, the nominal diameter of the first rim is not less than 16 inches and not more than 20 inches.

  Preferably, in the pneumatic tire, the band cord is made of an aramid fiber.

  In the pneumatic tire according to the present invention, the second rim diameter is larger than the first rim diameter. In other words, in this tire, the portion from the second sidewall to the second bead (second side portion) is shorter than the portion from the first sidewall to the first bead (first side portion). The second side portion contributes to weight reduction despite having the support layer. Despite the support layer being provided on the second side portion, heat hardly accumulates. This second side portion contributes to durability. The durability can be further improved by mounting the tire on the vehicle so that the second side portion is positioned inside.

  The tire expands such that the second side portion on the large diameter side is pulled by the first side portion on the small diameter side. The equator plane of the tire shifts to the smaller diameter side, and the second side portion on the larger diameter side rises. Thereby, the carcass in the second side portion extends substantially along the radial direction. This carcass profile effectively contributes to the tire support. Since the lateral stiffness increases, this tire provides good steering stability. In this tire, even if the internal pressure is reduced by puncture, the second side portion can sufficiently support the vehicle weight. This tire can travel a certain distance even in a punctured state.

  In this tire, the first side portion is longer than the second side portion. This first side portion contributes to bending. Since the longitudinal rigidity is appropriately maintained, this tire provides a good ride comfort. By mounting the tire on the vehicle so that the first side portion is located on the outer side, the ride comfort can be further improved.

  In this tire, the band covering the belt is formed of a spirally wound belt-like ply. The cross section of the band includes a large number of cross sections of the belt-like plies arranged in the axial direction. In this tire, in the cross section, the distance between the cross section of one belt-like ply and the cross section of another belt-like ply adjacent to the cross section of this one belt-like ply is the width of the cross-section of this belt-like ply. Is set to 0 or more and 1 or less, and the distance on the second end side of the belt is larger than the distance on the first end side of the belt. In the tire having this band, in the inflated state, a difference hardly occurs between the outer diameter of the portion having a small rim diameter and the outer diameter of the portion having a large rim diameter. In this tire, the increase in conicity is suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire by which the improvement of steering stability and riding comfort was achieved, suppressing the increase in conicity is obtained.

FIG. 1 is a cross-sectional view schematically showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a left portion of the tire of FIG. FIG. 3 is a cross-sectional view showing a right side portion of the tire of FIG. 1. FIG. 4 is a cross-sectional perspective view showing a part of a belt-like ply used for forming a band. FIG. 5 is a cross-sectional view showing a part of the band of the tire of FIG. 1. FIG. 6 is a schematic view showing the contour of the tire in FIG. 1 in use.

  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. Specifically, FIG. 1 shows a part of a cross section of the tire 2 along a plane including the central axis of rotation of the 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. The tire 2 is incorporated in the rim 4. The tire 2 is filled with air. Thereby, the internal pressure of the tire 2 is adjusted.

  FIG. 2 shows a left portion of the cross section of the tire 2 shown in FIG. FIG. 3 shows a right side portion of the cross section of the tire 2 shown in FIG. 2 and 3, 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.

  As will be described later, the tire 2 is obtained by pressurizing and heating a raw cover (uncrosslinked tire 2) in a mold (not shown). At this time, the raw cover is pressed against the cavity surface of the mold. Thereby, the outer surface of the tire 2 is obtained. The contour of the outer surface of the tire 2 shown in FIGS. 2 and 3 coincides with the contour of the cavity surface.

  2 and 3, the symbol PE represents the radially outer end of the tire 2. This outer end PE is also referred to as the equator. The solid line EL passes through the equator PE. The solid line EL extends in the radial direction. A solid line EL is the equator plane of the tire 2. In the present invention, the equator plane EL is specified based on the cavity surface of the mold. As apparent from FIGS. 2 and 3, the shape of the tire 2 is asymmetric with respect to the equator plane.

  The tire 2 includes a tread 6, a penetrating portion 8, a pair of sidewalls 10, a pair of clinch 12, a pair of beads 14, a carcass 16, a belt 18, a pair of edge bands 20, a pair of cushion layers 22, an inner liner 24, A pair of insulation 26, a pair of chafers 28, a pair of support layers 30 and a band 32 are provided. The tire 2 is a tubeless type. This tire 2 is for passenger cars.

  The tread 6 has a shape protruding outward in the radial direction. The tread 6 forms a tread surface 34 that comes into contact with the road surface. A groove 36 is carved in the tread 6. The groove 36 forms a tread pattern. The tread 6 has a cap layer 38 and a base layer 40. The cap layer 38 is located on the radially outer side of the base layer 40. The cap layer 38 is laminated on the base layer 40. The cap layer 38 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties. The base layer 40 covers the band 32. The base layer 40 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 40 is natural rubber. In FIG. 2, the symbol PT <b> 1 represents a specific point on the outer surface of the tire 2. This point PT1 is one axial outer end (first end) of the tread 6. In FIG. 3, the symbol PT <b> 2 represents a specific point on the outer surface of the tire 2. This point PT2 is the other axial outer end (second end) of the tread 6.

  The penetrating portion 8 is made of a conductive crosslinked rubber. The penetrating portion 8 penetrates the tread 6. One end of the penetrating portion 8 is exposed on the tread surface 34. The other end of the penetrating portion 8 is in contact with the band 32. In the tire 2, the penetrating portion 8 extends in the circumferential direction.

  One side wall 10a (first side wall) of the pair of side walls 10 extends from the first end PT1 of the tread 6 substantially inward in the radial direction. The other sidewall 10b (second sidewall) extends from the second end PT2 of the tread 6 substantially inward in the radial direction.

  The radially outer portion of each sidewall 10 is joined to the tread 6. The radially inner portion of the sidewall 10 is joined to the clinch 12. The sidewall 10 is made of a crosslinked rubber having excellent cut resistance and weather resistance. This sidewall 10 prevents the carcass 16 from being damaged.

  One clinch 12a (first clinch) of the pair of clinch 12 is positioned substantially radially inward of the first sidewall 10a. The other clinches 12b (second clinches) are located substantially inside the second sidewall 10b in the radial direction.

  Each clinch 12 is located outside the bead 14 and the carcass 16 in the axial direction. The clinch 12 is made of a crosslinked rubber having excellent wear resistance. The clinch 12 contacts the flange 42 of the rim 4.

  One bead 14a (first bead) of the pair of beads 14 is located on the inner side in the axial direction of the first clinch 12a. The first bead 14a is located on the inner side of the first sidewall 10a in the radial direction. The other bead 14b (second bead) is located on the inner side in the axial direction of the second clinch 12b. The second bead 14b is located inside the second sidewall 10b in the radial direction.

  Each bead 14 includes an inner part 44 and an outer part 46. The outer part 46 is located outside the inner part 44 in the axial direction.

  The inner part 44 includes an inner core 48 and an inner apex 50. Specifically, the inner part 44 includes an inner core 48 and an inner apex 50. The inner core 48 has a ring shape. Although not shown, the inner core 48 includes a wound non-stretchable wire. A typical material for the wire is steel. The inner apex 50 is made of a highly hard crosslinked rubber. The inner apex 50 covers the inner core 48 and extends from the inner core 48 substantially outward in the radial direction. The radially outer portion of the inner apex 50 has a tapered shape.

  The outer part 46 includes an outer core 52 and an outer apex 54. Specifically, the outer part 46 includes an outer core 52 and an outer apex 54. The outer core 52 has a ring shape. Although not shown, the outer core 52 includes a wound non-stretchable wire. A typical material for the wire is steel. The outer apex 54 is made of a highly hard crosslinked rubber. The outer apex 54 covers the outer core 52 and extends substantially outward in the radial direction from the outer core 52. The radially outer portion of the outer apex 54 has a tapered shape.

  In the tire 2, the inner apex 50 is joined to the outer apex 54 at the radially inner portion of each bead 14. In this portion, the inner apex 50 and the outer apex 54 are integrally formed.

  The carcass 16 includes a carcass ply 56. The carcass 16 of the tire 2 includes a single carcass ply 56. The carcass 16 may be formed from two or more carcass plies 56.

  The carcass ply 56 is bridged between the first bead 14a and the second bead 14b. The carcass ply 56 extends along the inside of the first sidewall 10a, the tread 6, and the second sidewall 10b. Although not shown, the carcass ply 56 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 equatorial plane EL is 75 ° to 90 °. In other words, the carcass 16 has a radial structure. The cord is made of organic fiber. Preferred organic fibers include polyethylene terephthalate fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber and aramid fiber. From the viewpoint of obtaining a carcass 16 having high rigidity, an aramid fiber is more preferable as the organic fiber for this cord.

  In the tire 2, the inner part 44 of the bead 14 is positioned inside the carcass ply 56 in the axial direction. The outer part 46 is located outside the carcass ply 56 in the axial direction. Specifically, the end of the carcass ply 56 is sandwiched between the inner part 44 and the outer part 46. As described above, the inner apex 50 and the outer apex 54 are integrally formed in the radially inner portion of the bead 14. In the tire 2, the carcass ply 56 is not folded around the bead 14 as in the conventional tire. In the present invention, the structure of the carcass 16 having the end portion sandwiched between the inner part 44 and the outer part 46 is referred to as an “insert structure”. Although not shown in the drawings, when the carcass is constituted by carcass plies folded around the bead, the structure of the carcass is referred to as a “folded structure”.

  The belt 18 is located on the inner side in the radial direction of the tread 6. The belt 18 is laminated with the carcass 16. The belt 18 reinforces the carcass 16. The belt 18 includes two layers, an inner layer 58 and an outer layer 60. The belt 18 may include three or more layers.

  In the tire 2, the width of the inner layer 58 is slightly larger than the width of the outer layer 60 in the axial direction. Although not shown, each of the inner layer 58 and the outer layer 60 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 general absolute value of the tilt angle is 10 ° or more and 35 ° or less. The inclination direction of the cord of the inner layer 58 with respect to the equator plane is opposite to the inclination direction of the cord of the outer layer 60 with respect to the equator plane. A preferred material for the cord is steel. An organic fiber may be used for the cord. Preferred organic fibers include polyethylene terephthalate fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber and aramid fiber.

  In the tire 2, the axial width of the belt 18 is preferably 0.7 times or more the maximum width of the tire 2. The maximum width is specified based on the contour of the cavity surface of the mold. The equatorial plane EL intersects the belt 18 at the center of the belt 18 in the axial direction.

  In FIG. 1, symbols PB <b> 1 and PB <b> 2 represent specific points on the outer surface of the belt 18. The point PB1 is on the first end 62a side of the belt 18, and the point PB2 is on the second end 62b side of the belt 18. In the tire 2, the axial length from the first end 62a of the belt 18 to the point PB1 is equal to the axial length from the point PB1 to the point PB2. The axial length from the point PB1 to the point PB2 is equal to the axial length from the point PB2 to the second end 62b of the belt 18. That is, the point PB1 and the point PB2 are points in the belt 18 that divide the axial width of the belt 18 into three equal parts. In the present invention, the zone from the first end 62a of the belt 18 to the point PB1 is referred to as an outer zone ZS. A zone from the point PB1 to the point PB2 is referred to as a central zone ZC. A zone from the point PB2 to the second end 62b of the belt 18 is referred to as an inner zone ZU.

  Each edge band 20 is located radially outside the belt 18 and in the vicinity of the end 62 of the belt 18. Although not shown, the edge band 20 is made of a cord and a topping rubber. The cord is wound in a spiral. The edge band 20 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. Since the end 62 of the belt 18 is restrained by this cord, the lifting of the belt 18 is suppressed. 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.

  Each cushion layer 22 is laminated with the carcass 16 in the vicinity of the end 62 of the belt 18. The cushion layer 22 is made of a soft crosslinked rubber. The cushion layer 22 absorbs stress at the end 62 of the belt 18. This cushion layer 22 contributes to suppression of lifting of the belt 18.

  The inner liner 24 is located inside the carcass 16. In the vicinity of the equator plane, the inner liner 24 is joined to the inner surface of the carcass 16. The inner liner 24 is made of a crosslinked rubber having excellent air shielding properties. A typical base rubber of the inner liner 24 is butyl rubber or halogenated butyl rubber. The inner liner 24 maintains the internal pressure of the tire 2.

  Each insulation 26 is located inside the sidewall 10 in the axial direction. The insulation 26 is sandwiched between the support layer 30 and the inner liner 24. The insulation 26 is made of a crosslinked rubber having excellent adhesiveness. The insulation 26 is firmly bonded to the support layer 30 and is also firmly bonded to the inner liner 24. The insulation 26 prevents the inner liner 24 from being peeled on the inner side in the axial direction of the sidewall 10.

  Each chafer 28 is located in the vicinity of the bead 14. When the tire 2 is incorporated into the rim 4, the chafer 28 comes into contact with the rim 4. By this contact, the vicinity of the bead 14 is protected. In this embodiment, the chafer 28 is integral with the clinch 12. Therefore, the material of the chafer 28 is the same as that of the clinch 12. The chafer 28 may be made of a cloth and rubber impregnated in the cloth.

  One support layer 30a (first support layer) of the pair of support layers 30 is located on the inner side in the axial direction than the first sidewall 10a. The first support layer 30a is located on the inner side in the axial direction of the carcass 16 on the first sidewall 10a side. The other support layer 30b (second support layer) is located on the inner side in the axial direction than the second sidewall 10b. The second support layer 30b is located on the inner side in the axial direction of the carcass 16 on the second sidewall 10b side. Each support layer 30 is sandwiched between the carcass 16 and the inner liner 24. The support layer 30 is located on the radially outer side of the inner apex 50 in the bead 14. In the tire 2, the support layer 30 is laminated with the inner apex 50.

  In the tire 2, the support layer 30 tapers inward in the radial direction and also tapers outward. This support layer 30 has a similar shape to the crescent moon. The support layer 30 is made of a crosslinked rubber. When the tire 2 is punctured, the support layer 30 supports the vehicle weight. The support layer 30 allows the tire 2 to travel a certain distance even in a puncture state. The tire 2 is also called a run flat tire. The tire 2 is a side reinforcing type.

  In the tire 2, the hardness of the support layer 30 is preferably 60 or greater and 85 or less. By setting the hardness to 60 or more, when the internal pressure of the tire 2 is reduced due to puncture, the support layer 30 can effectively contribute to the support of the vehicle weight. From this viewpoint, the hardness is more preferably 65 or more. By setting the hardness to 85 or less, the influence of the support layer 30 on the deflection of the portion of the sidewall 10 can be suppressed. In the tire 2, the riding comfort is appropriately maintained. From this viewpoint, the hardness is more preferably 80 or less.

  In the present application, the hardness is JIS-A hardness. This hardness is measured with a type A durometer in an environment of 23 ° C. in accordance with the provisions of “JIS-K6253”. More specifically, the hardness is measured by pressing a type A durometer against the cross section shown in FIGS.

  The band 32 is located on the radially outer side of the belt 18. The band 32 is located between the belt 18 and the tread 6 in the radial direction. In the axial direction, the width of the band 32 is larger than the width of the belt 18. The band 32 covers the belt 18.

  The band 32 includes a band cord and a topping rubber. The band cord is spirally wound. The band 32 has a so-called jointless structure. The band cord extends substantially in the circumferential direction. The angle of the band cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. Since the belt 18 is restrained by the band cord, lifting of the belt 18 is suppressed. The band cord is made of an organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. From the viewpoint of obtaining a band 32 having appropriate rigidity, a cord made of an aramid fiber is more preferable as the band cord. This band 32 contributes to weight reduction and reduction of rolling resistance.

  Although not shown, the band cord is formed by twisting a plurality of raw yarns. From the viewpoint of the rigidity and workability of the band cord, the number of raw yarns constituting the band cord is preferably 2 or more, and more preferably 3 or less. The number of times the raw yarn is twisted is preferably 40 times / 10 cm or more, and more preferably 80 times / 10 cm or less. Further, when a cord made of aramid fiber is used for the band cord, the fineness of the raw yarn is preferably 600 dtex or more and preferably 1700 dtex or less from the viewpoint of the rigidity and mass of the band cord.

  In the tire 2, the band 32 is formed using the belt-like ply 64 shown in FIG. 4. The band 32 includes a belt-like ply 64. The belt-like ply 64 has a tape shape. The belt-like ply 64 includes a band cord 66, and the band cord 66 is covered with a topping rubber 68. In other words, the belt-like ply 64 is composed of a band cord 66 and a topping rubber 68.

  The belt-like ply 64 shown in FIG. 4 includes a plurality of band cords 66. Specifically, the belt-like ply 64 includes five band cords 66. These band cords 66 are juxtaposed in the width direction of the belt-like ply 64.

  In the tire 2, the number of band cords 66 included in the belt-like ply 64 is not particularly limited. From the viewpoint of restraining the belt 18, the number of the band cords 66 included in the belt-like ply 64 is preferably two or more. From the viewpoint of productivity, the number of band cords 66 included in the belt-like ply 64 is preferably 20 or less.

  In FIG. 4, the double arrow WP is the width of the belt-like ply 64. In the tire 2, the width WP of the belt-like ply 64 is not particularly limited, but usually the width WP is appropriately set in a range of 5 mm to 30 mm. The width WP of the belt-like ply 64 is synonymous with the width of the cross-section of the belt-like ply 64 described later.

  In the tire 2, the band 32 has the belt-like ply 64 outward in the radial direction of the belt 18, for example, from the first end 62 a side to the second end 62 b side of the belt 18 or the belt 18. This is formed by spirally winding from the second end 62b side toward the first end 62a side. Therefore, the cross section of the band 32 included in the cross section of the tire 2 along the plane including the central axis of rotation of the tire 2 includes a large number of cross sections of the belt-like ply 64, and these cross sections are in the axial direction. Are in parallel.

  In FIG. 5, the cross section of the band 32 is shown together with the cross section of the belt 18. Specifically, FIG. 5A shows a cross section of the band 32 in the outer zone ZS. FIG. 5B shows a cross section of the band 32 in the central zone ZC. FIG. 5C shows a cross section of the band 32 in the inner zone ZC. In FIG. 5, 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. 5, a double-headed arrow DP is a distance between one cross-section of the belt-like ply 64 and another cross-section of the belt-like ply 64 positioned next to the cross-section of the one belt-like ply 64.

  As shown in FIG. 5, in the outer zone ZS, there is a gap between one cross section of the belt-like ply 64 and another cross-section of the belt-like ply 64 located next to the cross section of the one belt-like ply 64. They are lined up. In the central zone ZC, a gap is provided between one cross section of the belt-like ply 64 and another cross section of the belt-like ply 64 located next to the cross section of the one belt-like ply 64. That is, the distance DP in the central zone ZC (hereinafter also referred to as the distance DPC) is larger than the distance DP in the outer zone ZS (hereinafter also referred to as the distance DPS). In the inner zone ZU, there is a gap in the central zone ZC described above between one cross section of the belt-like ply 64 and the other cross-section of the belt-like ply 64 located next to the cross section of the one belt-like ply 64. A larger gap is provided. That is, the interval DP in the inner zone ZU (hereinafter also referred to as the interval DPU) is larger than the interval DPC in the central zone ZC. Thus, in the tire 2, when the band 32 is formed, the winding pitch of the band-like ply 64 in each zone is adjusted.

  The tire 2 described above is used by being mounted on the rim 4 and filled with air. As this rim 4, for example, a split rim is used. The rim 4 includes a pair of half rims 70. Each half rim 70 includes a bead seat 72. The bead seat 72 is fitted with the bead 14 portion of the tire 2. In the present invention, the bead sheet 72a into which the portion of the first bead 14a (first bead portion 74a) is fitted is referred to as a first sheet. The bead sheet 72b into which the portion of the second bead 14b (second bead portion 74b) is fitted is referred to as a second sheet. That is, one half rim 70a (first half rim) includes the first sheet 72a. The other half rim 70b (second half rim) includes a second sheet 72b. The rim 4 includes a first sheet 72a and a second sheet 72b.

  In the tire 2, a portion from the first sidewall 10a to the first bead 14a (first side portion 76a) is a portion from the second sidewall 10b to the second bead 14b (second side portion 76b). ). Therefore, when the rim diameter of the rim 4 in the first seat 72a is the first rim diameter and the rim diameter of the rim 4 in the second seat 72b is the second rim diameter, the first rim diameter is greater than the second rim diameter. Is also small. In the tire 2, the side where the first side portion 76a is located is the small diameter side, and the side where the second side portion 76b is located is the large diameter side. Accordingly, in the tire 2, the rim diameter on the large diameter side (that is, the rim diameter of the second rim D2) is larger than the rim diameter on the small diameter side (that is, the rim diameter of the first rim D1). The tire 2 is a different diameter bead type. In the present invention, the “nominal rim diameter” has the same meaning as the “nominal rim diameter” included in the “nominal tire” in the JATMA standard.

  In the present invention, the shape of the rim 4 on which the tire 2 is mounted is unique compared to the shape of a normal rim (hereinafter referred to as a normal rim) having the same left and right rim diameters. This rim 4 is special. For the tire 2 of the present invention, for example, two split-type regular rims having different rim diameters are prepared, and this is achieved by combining one regular rim half rim 70a and the other regular rim half rim 70b. The rim 4 can be configured. Since the rim 4 configured in this manner is configured by combining two regular rims, in the present invention, it is also referred to as a quasi-regular rim as a rim conforming to the regular rim. Further, in the present specification, the normal rim means a rim defined in a standard on which the tire 2 relies. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims.

  The tire 2 described above is manufactured as follows. In this manufacturing method, a core is prepared. Although not shown, the core has a toroidal outer surface.

  In the method for manufacturing the tire 2, a low cover (unvulcanized tire 2) is obtained by combining a number of elements including the inner liner 24 on the outer surface of the core. In this manufacturing method, the raw cover is assembled on the outer surface of the core.

  In this manufacturing method, a band-like ply 64 is prepared for forming the band 32. As described above, the belt-like ply 64 is spirally formed outside the belt 18 in the radial direction while adjusting the winding pitch of the belt-like ply 64 in each of the outer zone ZS, the central zone ZC, and the inner zone ZU. And band 32 is formed.

  In this manufacturing method, the raw cover is put into a mold (not shown) together with the core. After charging, the mold is closed. The inner surface of the low cover is in contact with the core. The outer surface of the raw cover is in contact with the cavity surface of the mold. The raw cover is pressed between the cavity surface of the mold and the outer surface of the core. The raw cover is pressurized and heated in the mold. The rubber composition of the raw cover flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and the tire 2 is obtained. Thus, the manufacturing method of the tire 2 using a core is also called a core method.

  As described above, in the tire 2, cords made of aramid fibers (hereinafter referred to as aramid cords) are preferably used for members such as the carcass 16 and the band 32 from the viewpoint of rigidity. Adoption of this aramid cord contributes to reduction of rolling resistance and improvement of durability in a puncture state. However, the growth of this aramid cord is quite small. For this reason, it is difficult to manufacture the tire 2 including the member including the aramid cord in the manufacturing method including the step of inflating the raw cover and adjusting the shape thereof, that is, the shaping step. On the other hand, in the core method, it is not necessary to inflate the raw cover to adjust its shape. With this core method, the tire 2 can be molded without any change in the shape of the raw cover. According to this core method, the tire 2 can be stably manufactured even when a member including an aramid cord having a small elongation is employed. This core method contributes to reduction of rolling resistance of the tire 2 and improvement of durability in a puncture state.

  As described above, the shape of the tire 2 is asymmetric with respect to the equator plane EL. The shape of the tire 2 can be configured, for example, by combining two tires having the same cross-sectional width, different flatness ratios, and different rim diameters in their respective equatorial planes. Specifically, for example, the shape of the small diameter side is constituted by the shape of the tire represented by “Nominal of tire” of 245 / 45R18, and the shape of the tire represented by “Nominal of tire” of 245 / 35R20 is used. By configuring the shape on the large diameter side, the shape of the tire 2 shown in FIGS. 1-3 can be obtained. In this case, the cavity surface of the mold reflects the outer surface of the tire represented by “Nominal Tire” of 245 / 45R18 and the outer surface of the tire represented by “Nominal Tire” of 245 / 35R20. The outer surface of the core reflects the inner surface of the tire 2 represented by “Tire Nominal” of 245 / 45R18 and the inner surface of the tire represented by “Tire Nominal” of 245 / 35R20.

  As described above, in the tire 2, the second side portion 76b is shorter than the first side portion 76a. The second side portion 76b contributes to weight reduction despite having the second support layer 30b. The second side portion 76b also contributes to a reduction in rolling resistance.

  A support layer 30 is provided on the side portion 76 of the tire 2. For this reason, the side portion 76 tends to accumulate heat. However, in the tire 2, since the second side portion 76b is shorter than the first side portion 76a, the volume of the second side portion 76b is small. Despite the second support layer 30b being provided on the second side portion 76b, heat is unlikely to accumulate. The second side portion 76b contributes to durability. By mounting the tire 2 on the vehicle so that the second side portion 76b is located on the inner side, the durability can be further improved.

  FIG. 1 shows a state in which the tire 2 shown in FIGS. 2 and 3 is incorporated in the rim 4 and the inside of the tire 2 is filled with air.

  When the inside of the tire 2 is filled with air, the tire 2 expands. As described above, the carcass 16 of the tire 2 includes a number of cords. Due to the expansion, tension is applied to each cord. In the tire 2 in the inflated state, the tension acting on these cords is uniform.

  In FIG. 1, a double-headed arrow WR represents the rim width of the rim 4 on which the tire 2 is mounted. The alternate long and short dash line CL passes through the center of the rim width WR. This alternate long and short dash line CL is a center line in the width direction of the rim 4. In the manufacture of the tire 2, a mold is used in which the cavity surface is adjusted so that the equator plane EL substantially coincides with the center line CL in the axial direction. In a conventional tire with the same nominal rim diameter on the left and right, when the inside is filled with air and the tire is inflated, the equator plane EL substantially coincides with the center line CL in the axial direction.

  As shown in FIG. 1, the equatorial plane EL is located on the left side of the center line CL. That is, the tire 2 is inflated so that the large diameter side is pulled to the small diameter side. For this reason, the equator plane EL of the tire 2 is shifted to the small diameter side, and the second side portion 76b on the large diameter side rises. In the tire 2 in an inflated state, the carcass 16 in the second side portion 76b extends substantially along the radial direction. The profile of the carcass 16 (also referred to as a carcass line) effectively contributes to the support of the tire 2. Since the lateral rigidity increases, the tire 2 can provide good steering stability. In the tire 2, even if the internal pressure is reduced due to puncture, the second side portion 76b can sufficiently support the vehicle weight. The tire 2 can travel a certain distance even in a punctured state.

  In the tire 2, the first side portion 76a is longer than the second side portion 76b. The first side portion 76a contributes to bending. Since the longitudinal rigidity is appropriately maintained, the tire 2 can provide a good riding comfort. By mounting the tire 2 on the vehicle so that the first side portion 76a is located on the outer side, the riding comfort can be further improved.

  In the tire 2, the band 32 includes a belt-like ply 64 spirally wound on the outer side in the radial direction of the belt 18. Specifically, the band 32 is composed of a belt-like ply 64 spirally wound on the outer side in the radial direction of the belt 18. The cross section of the band 32 includes a large number of cross sections of the belt-like plies 64 arranged in parallel in the axial direction.

  In the tire 2, in the cross section of the band 32, the interval DP between one cross section of the belt-like ply 64 and the cross section of the other belt-like ply 64 positioned next to the cross section of the one belt-like ply 64 is appropriately adjusted. Has been. Specifically, the ratio of the distance DP to the cross-sectional width WP of the belt-like ply 64 is 0 or more and 1 or less. By setting this ratio to 0 or more, the cross section of one belt-like ply 64 and the cross-section of another belt-like ply 64 positioned next to the cross section of this one belt-like ply 64 do not overlap each other. A band 32 is formed. In the tire 2, the influence on the mass by the band 32 is suppressed. By setting this ratio to 1 or less, the rigidity of the band 32 is appropriately maintained. In the tire 2, the band 32 effectively restrains the belt 18. That is, in the tire 2, the ratio of the distance DP to the width WP is set to 0 or more and 1 or less, and preferably, the ratio is set to 0.0 or more and 1.0 or less to increase the mass of the tire 2. And the binding force of the band 32 are arranged in a well-balanced manner.

  Further, in the tire 2, the distance DPU between the cross section of the belt-like ply 64 and the cross-section of the other belt-like ply 64 located next to the cross section of the belt-like ply 64 in the inner zone ZU, that is, the belt. The distance DPU on the second end 62b side of 18 is larger than the distance DPS on the outer zone ZS, that is, the distance DPS on the first end 62a side of the belt 18. Therefore, the band 32 formed of the belt-like ply 64 has a large rigidity on the first end 62a side of the belt 18 and a small rigidity on the second end 62b side.

  FIG. 6 shows the usage state of the tire 2. In FIG. 6, what is indicated by a solid line is the contour of the tire 2. What is indicated by a dotted line is an outline of a tire 78 (hereinafter referred to as a reference tire) having a band that is formed by spirally winding a belt-like ply at a constant pitch. All the contours are confirmed in a state where the tires 2 and 78 are incorporated in the quasi-regular rim and the internal pressure is adjusted to 230 kPa. Except for the band of the reference tire 78, the tire has the same configuration as the tire 2 shown in FIG. Therefore, the reference tire 78 is also a different diameter bead type.

  Although not shown, in the reference tire 78, unlike the band 32 of the tire 2 shown in FIG. 1, in the entire cross section of the band, one cross section of the band ply and the cross section of the one band ply are adjacent to each other. The cross-sections of the other belt-like plies positioned at are arranged at equal intervals. In this band, the rigidity on the first end side of the belt is equal to the rigidity on the second end side. The rigidity of this band is substantially uniform in the axial direction.

  As shown in FIG. 6, in the reference tire 78, regarding the swelling of the tire 78 due to air filling, the degree of swelling of the left part is larger than the degree of swelling of the right part. In the reference tire 78, since the rigidity of the band is uniform in the axial direction, the difference in the degree of swelling is caused by the fact that the rigidity of the first side part is smaller than that of the second side part. It is believed that. In the reference tire 78, since the outer diameter of the left portion is larger than the outer diameter of the right portion, the left end, that is, from the first end side of the belt (not shown) to the right end, that is, the second end side. A big conicity is generated.

  On the other hand, in the tire 2 of the present invention, the band 32 includes one cross-section of the belt-like ply 64 and another cross-section of the belt-like ply 64 positioned next to the cross-section of the one belt-like ply 64 in the cross-section. Is set to be not less than 1 and not more than 1 with respect to the width WP of the cross section of the belt-like ply 64, and the distance DP on the second end 62b side of the belt 18 is set to the first end 62a of the belt 18. It is configured to be larger than the interval DP on the side. In the tire 2, as shown in FIG. 6, regarding the swelling of the tire 2 by air filling, the degree of swelling of the belt 18 on the first end 62 a side, that is, the left side portion, is the second end 62 b side. That is, it is substantially equivalent to the degree of swelling of the right side portion. In the tire 2 having the band 32, in the inflated state, there is a difference between an outer diameter of a left side portion, that is, a portion having a small rim diameter, and a right portion, that is, an outer diameter of a portion having a large rim diameter. Is unlikely to occur. In the tire 2, an increase in conicity is suppressed.

  As described above, according to the present invention, it is possible to obtain the pneumatic tire 2 in which improvement in handling stability and riding comfort is achieved while suppressing increase in conicity.

  In the tire 2, the number of the belt-like plies 64 used for forming the band 32 is not particularly limited. For example, three belt-like plies 64 may be prepared, and each of the outer zone ZS, the central zone ZC, and the inner zone ZU may be formed by one belt-like ply 64, or the entire band 32 may be one belt-like ply 64. May be formed. From the standpoint that the band 32 effectively restrains the belt 18, the entire band 32 is preferably composed of a single band-like ply 64. In this case, the distance DP of the belt-like ply 64 is gradually changed from the distance DPS to the distance DPC at the boundary between the outer zone ZS and the central zone ZC, and from the distance DPC at the boundary between the central zone ZC and the inner zone ZU. The interval DPU is gradually changed.

  As described above, in the tire 2, the band 32 has one cross-section of the belt-like ply 64 in the cross-section and another cross-section of the belt-like ply 64 positioned next to the cross-section of the one belt-like ply 64. Is set to be not less than 0 and not more than 1 with respect to the width WP of the cross section of the belt-like ply 64, and the interval DP on the second end 62b side of the belt 18 is set on the first end 62a side of the belt 18. It is comprised so that it may become larger than the space | interval DP in. In particular, in the tire 2, the distance DPC in the central zone ZC is larger than the distance DPS in the outer zone ZS, and the distance DPU in the inner zone ZU is larger than the distance DPC in the central zone ZC. Thereby, regarding the swelling of the tire 2 by air filling, the same degree of swelling is achieved in the left side portion and the right side portion of the tire 2.

  In this tire, the deformation allowance when the long first side portion 76a is expanded is larger than that of the short second side portion 76b. For this reason, the left side portion of the tire 2 where the first side portion 76a is disposed is easily expanded.

  In this tire, the ratio of the distance DPS between the belt-like plies 64 to the width WP of the belt-like plies 64 in the outer zone ZS is preferably 0.2 or less. The band 32 effectively suppresses the swelling of the left portion of the tire 2 in the outer zone ZS. In the tire 2, the same degree of swelling is achieved in the left side portion and the right side portion of the tire 2, and an increase in conicity is suppressed. From this point of view, this ratio is 0, that is, the belt-like ply 64 is preferably wound without a gap as shown in FIG. More preferably, this ratio is 0.0.

  In the tire 2, the deformation margin at the time of expansion of the short second side portion 76b is smaller than that of the long first side portion 76a. For this reason, the right side portion of the tire 2 where the second side portion 76b is disposed is difficult to expand. For this reason, if the distance DPU between the belt-like plies 64 is small in the inner zone ZU, the expansion of the right side portion of the tire 2 is excessively suppressed, and on the contrary, the balance between the left and right expansions may be lost.

  In the tire 2, the ratio of the distance DPU between the belt-like plies 64 to the width WP of the belt-like plies 64 in the inner zone ZU is preferably 0.8 or more. This prevents the band 32 from excessively suppressing the expansion of the right side portion of the tire 2 in the inner zone ZU. In the tire 2, the same degree of swelling is achieved in the left side portion and the right side portion of the tire 2, and an increase in conicity is suppressed. This ratio is preferably 1 or less from the viewpoint of securing the binding force of the belt 18 by the band 32 and maintaining good high-speed durability and steering stability. More preferably, this ratio is 1.0 or less.

  In the tire 2, the distance DPC between the belt-like plies 64 in the central zone ZC also affects the expansion of the tire 2. That is, if the distance DPC is small, the expansion of the tire 2 is suppressed as a whole, and on the contrary, the left and right expansion cannot be adjusted in a well-balanced manner. If the distance DPC is large, the expansion of the tire 2 cannot be sufficiently suppressed, and also in this case, the left and right expansion cannot be adjusted in a well-balanced manner. In addition, since the rigidity of the band 32 is insufficient, there is a possibility that performance such as steering stability may be deteriorated.

  In the tire 2, the same degree of swelling is achieved in the left side portion and the right side portion of the tire 2 from the viewpoint that the increase in conicity is suppressed and good steering stability is maintained. The ratio of the distance DPC of the belt-like ply 64 to the width WP of the belt-like ply 64 in FIG. More preferably, this ratio is set to 0.5.

  As described above, the tire 2 is a different diameter bead type. As a result, the carcass line in the expanded state is controlled, and the steering stability is improved. In this respect, the difference (D2−D1) between the second rim diameter D2 and the first rim diameter D1 is preferably 1 inch or more. This difference (D2−D1) is preferably 3 inches or less from the viewpoint of maintaining the carcass line and preventing the straight running stability and the wear resistance from being deteriorated.

  As described above, in the tire 2, the first side portion 76a is longer than the second side portion 76b. The long first side portion 76a contributes to bending. Since the increase in the longitudinal rigidity can be suppressed, the tire 2 can provide a good ride comfort. From the viewpoint of forming the long first side portion 76a, the nominal D1 of the first rim diameter is preferably 20 inches or less. From the viewpoint that the influence on the steering stability by the long first side portion 76a can be suppressed, the nominal diameter D1 of the first rim diameter is preferably 16 inches or more.

  As described above, in the tire 2, the second side portion 76b is shorter than the first side portion 76a. Since the short second side portion 76b effectively increases the longitudinal rigidity, the tire 2 can obtain good steering stability and run-flat durability. From this viewpoint, the second rim diameter nominal D2 is preferably 17 inches or more. From the viewpoint that the influence on the wear resistance and the ride comfort by the short second side portion 76b can be suppressed, the nominal D2 of the second rim diameter is preferably 23 inches or less.

  In FIG. 1, a solid line BL1 is a first baseline. The first base line corresponds to a line that defines the first rim diameter of the rim 4 on which the tire 2 is mounted. This first baseline extends in the axial direction. The solid line BL2 is the second baseline. The second base line corresponds to a line that defines the second rim diameter of the rim 4. This second baseline extends in the axial direction.

  In FIG. 1, a double-headed arrow H1 represents the height in the radial direction from the first base line to the radially outer end PE of the tire 2. The height H1 is a cross-sectional height of the tire 2 obtained with reference to the first baseline. A double-headed arrow H2 represents the height in the radial direction from the second base line to the radially outer end PE of the tire 2. The height H2 is a cross-sectional height of the tire 2 obtained with reference to the second baseline. A double arrow W represents the maximum width of the tire 2 in the axial direction. The width W is a cross-sectional width of the tire 2.

  In the present invention, the cross-sectional height H1, the cross-sectional height H2, and the cross-sectional width W are measured in a state where the tire 2 is filled with air. At the time of measurement, no load is applied to the tire 2. The internal pressure of the tire 2 at the time of measurement is determined with reference to the normal internal pressure defined in the standard on which the tire 2 depends in consideration of the application and size. In the tire 2 shown in FIG. 1, since the tire 2 is for a passenger car, the cross-sectional height H1, the cross-sectional height H2, and the cross-sectional width are filled with air so that the internal pressure of the tire 2 is 180 kPa. W is measured. In this specification, the normal internal pressure means “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. To do.

  In the present invention, the flatness ratio on the small diameter side (hereinafter referred to as the first flatness ratio F1) is represented by the ratio of the cross-sectional height H1 to the cross-sectional width W. The flatness ratio on the large diameter side (hereinafter referred to as the second flatness ratio F2) is represented by the ratio of the cross-sectional height H2 to the cross-sectional width W.

  In the tire 2, the first aspect ratio F1 is preferably equal to or greater than 0.40 and is preferably equal to or less than 0.70 from the viewpoint of ride comfort and handling stability. Further, from the viewpoint that the influence on the wear resistance by the carcass line can be suppressed, the first aspect ratio F1 is more preferably 0.45 or more, and more preferably 0.65 or less.

  In the tire 2, the second aspect ratio F2 is preferably 0.30 or more and preferably 0.60 or less from the viewpoint of steering stability and run-flat durability. Furthermore, from the viewpoint that the wear resistance can be further improved, the second aspect ratio F2 is preferably 0.35 or more, and more preferably 0.55 or less.

  In the tire 2 mounted on a four-wheeled vehicle, a larger load than the outer portion tends to act on the inner portion in the width direction of the vehicle. In particular, when the vehicle is mounted on the vehicle so that the equator plane is inclined with respect to the vertical line, in particular, when the camber angle is set with a negative camber, this tendency is remarkable. In the tire 2, the first side portion 76a mainly contributes to the vertical rigidity, and the second side portion 76b mainly contributes to the lateral rigidity. From the viewpoint of ride comfort, steering stability, and run-flat durability, the first side portion 76a is positioned on the outer side in the width direction of the vehicle (also referred to as the front side or S side), and the second side portion 76b is provided on the vehicle. The tire 2 is preferably attached to a four-wheeled vehicle so as to be located on the inner side in the width direction (also referred to as a back side or NS side). In this case, since the first side portion 76a has a low contribution to the run-flat durability and is disposed on the outer side in the width direction of the vehicle, the thin first support layer 30a can be adopted, and further weight reduction and The rolling resistance can be further reduced. In some cases, the first support layer 30a can be removed from the first side portion 76a. In this case, the weight can be further reduced and the rolling resistance can be reduced.

  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]
The tire shown in FIG. 1-3 was manufactured. In Example 1, as shown in Table 1 below, the nominal rim diameter D1 is 18 inches. The nominal rim diameter D2 is 20 inches.

  As the band cord, a cord made of aramid fibers (configuration = 800 dtex / 2, number of twisting = 60 times / 10 cm) was adopted. This is represented as “aramid” in the band code column of Table 1.

  For forming the band, a band-like ply having a width WP set to 10 mm was used. In the outer zone on the first end side of the belt, in the cross section of the band, the cross section of one strip ply with respect to the width WP of the cross section of the strip ply and the other strip plies positioned next to the cross section of the single strip ply The ratio of the distance DP to the cross section (DP / WP) was set to 0.0. The ratio (DP / WP) in the outer zone is synonymous with the ratio (DPS / WP). In the central zone, this ratio (DP / WP) was set to 0.5. The ratio (DP / WP) in this central zone is synonymous with the ratio (DPC / WP). In the inner zone on the second end side of the belt, this ratio (DP / WP) was set to 1.0. The ratio (DP / WP) in this inner zone is synonymous with the ratio (DPU / WP).

  The first aspect ratio F1 and the second aspect ratio F2 are as shown in Table 1 below. The cross-sectional width W was 245 mm.

  In the first embodiment, the “insert structure” carcass is employed. This is indicated by “I” in the “Carcass structure” column of the table. A cord made of an aramid fiber is used as the cord included in the carcass. A cord made of steel is used as the cord included in the belt. This Example 1 is manufactured by the core method.

[Comparative Example 1-4]
Comparative Example 1-4 is a conventional tire. The shape of these tires is symmetric with respect to the equator plane. The cross-sectional width W is 245 mm in all cases. The flatness ratio F1, the first rim diameter D1, the flat ratio F2, and the second rim diameter D2 are as shown in Table 1 below. In Comparative Example 1-4, the entire band is formed using the belt-like ply used for forming the band of Example 1. In the formation of this band, the ratio (DP / WP) was set to 0 in each of the outer zone, the central zone and the inner zone. That is, the entire band was configured by winding the belt-like ply in a spiral shape without a gap. In Comparative Examples 1 and 2, a “folded structure” carcass is employed. This is indicated by “F” in the “Carcass structure” column of the table. In Comparative Examples 3 and 4, the same “insert structure” carcass as in Example 1 is employed.

[Comparative Example 5-7]
Comparative example except that the second rim diameter D2 is changed to change the flatness ratio F2 and the difference between the second rim diameter D2 and the first rim diameter D1 (D2-D1) as shown in Table 1 below. In the same manner as in Example 3, a tire of Comparative Example 5-7 was obtained.

[Example 2-4 and Comparative Example 8]
The tires of Example 2-4 and Comparative Example 8 were the same as Example 1 except that the second rim diameter D2 was changed and the flatness ratio F2 and difference (D2-D1) were as shown in Table 2 below. Got.

[Comparative Example 9]
A tire of Comparative Example 9 was obtained in the same manner as in Example 1 except that the outer zone ratio (DP / WP) and the inner zone ratio (DP / WP) were as shown in Table 3 below.

[Example 5-6]
A tire of Example 5-6 was obtained in the same manner as Example 1 except that the ratio of the outer zone (DP / WP) was as shown in Table 3 below.

[Example 7-10]
Tires of Examples 7-10 were obtained in the same manner as in Example 1 except that the ratio of the central zone (DP / WP) was as shown in Table 4 below.

[Example 11-13]
Tires of Examples 11-13 were obtained in the same manner as in Example 1, except that the inner zone ratio (DP / WP) was as shown in Table 5 below.

[Examples 14-18]
The first rim diameter D1 and the second rim diameter D2 were changed, and the flatness ratio F1, the flatness ratio F2 and the difference (D2−D1) were changed as shown in Table 6 below. Thus, tires of Examples 14-18 were obtained.

[Example 19]
A tire of Example 19 was obtained in the same manner as in Example 1 except that the band cord was replaced with a cord made of nylon fiber (configuration = 1400 dtex / 2, number of twists = 60 times / 10 cm).

[Rolling resistance coefficient (RRC)]
Using a rolling resistance tester (drum diameter = 1.7 m, drum surface = smooth steel), the rolling resistance coefficient (RRC) was measured under the following measurement conditions. For the rim, the first half rim (made of aluminum alloy) is selected with reference to the first rim diameter D1, and the second half rim (made of aluminum alloy) is selected with reference to the second rim diameter D2. Thus, a split rim (quasi-regular rim) constituted by combining the first half rim and the second half rim was used. In this rim, the rim width was set to 8.5 inches.
Internal pressure: 210 kPa
Load: 5.3kN
Speed: 80km / h
Temperature: 20 ° C
Break-in time: 30 minutes This result is an index and is shown in Tables 1-6 below. A larger numerical value is preferable, that is, a rolling resistance coefficient (RRC) is small.

[Mass of tire]
The mass of one tire was measured. The result is an index and is shown in the following Tables 1-6. A larger value is more preferable, that is, a smaller mass.

[Ride comfort and handling stability]
A tire was incorporated into the rim, and the tire was filled with air so that the internal pressure was 230 kPa. This tire was mounted on a commercially available hybrid type passenger car. The tire was mounted such that the small diameter side of the tire was positioned on the outer side in the width direction (S side) of the vehicle, and the large diameter side was positioned on the inner side in the width direction of the vehicle (NS side). As the rim, a quasi-normal rim used in the measurement of the rolling resistance coefficient was used. The driver was allowed to drive the passenger car on a racing circuit to evaluate ride comfort and handling stability. No one other than the driver is in this passenger car. The result is an index and is shown in the following Tables 1-6. Larger numbers are preferable.

[Conicity]
Conicity (CON) was measured under the conditions shown below in accordance with the uniformity test method defined in “JASO C607: 2000”. Ten tires were measured, and the average value of the measurement results is an index and is shown in Table 1-6 below. The closer this value is to 0, the better the occurrence of conicity is suppressed. As the rim, a quasi-normal rim used in the measurement of the rolling resistance coefficient was used.
Rim width: 8.5 inches Internal pressure: 210 kPa
Load: 5.3kN
Speed: 60rpm

  As Table 1-6 shows, in the tire of an Example, evaluation is high compared with the tire of a comparative example. From this evaluation result, the superiority of the present invention is clear.

  The tire described above can be applied to various types of four-wheeled vehicles.

2 ... Tire 4 ... Rim 6 ... Tread 10, 10a, 10b ... Sidewall 12, 12a, 12b ... Clinch 14, 14a, 14b ... Bead 16 ... Carcass 18. .. Belt 30, 30a, 30b ... support layer 32 ... band 34 ... tread surface 56 ... carcass ply 58 ... inner layer 60 ... outer layer 62, 62a, 62b ... End of belt 18 64 ... belt-like ply 66 ... band cord 68 ... topping rubber 70, 70a, 70b ... half rim 72, 72a, 72b ... bead sheet 74, 74a, 74b ... bead Part 76, 76a, 76b ... side part

Claims (5)

A tire used on a rim,
Tread, first side wall, second side wall, first bead, second bead, carcass, belt, support layer and band,
The first sidewall extends radially inward from the first end of the tread; the second sidewall extends radially inward from the second end of the tread;
The first bead is located radially inward of the first sidewall, the second bead is located radially inward of the second sidewall,
The carcass spans between the first bead and the second bead along the inside of the first sidewall, the tread and the second sidewall,
The belt is laminated with the carcass radially inside the tread;
The support layer is located on the second sidewall side on the inner side in the axial direction of the carcass;
The band is located between the belt and the tread and covers the belt;
The band includes a belt-like ply spirally wound on the outer side in the radial direction of the belt;
The belt-like ply includes a band cord,
The cross section of the band includes a large number of cross sections of the band-shaped ply arranged in the axial direction,
In the cross section of the band, the ratio of the interval between the cross section of one strip ply and the cross section of another strip ply located next to the cross section of the single strip ply to the width of the cross section of the strip ply is 0 or more 1 or less,
The interval on the second end side of the belt is larger than the interval on the first end side of the belt;
The rim includes a first sheet in which a portion of the first bead is fitted, and a second sheet in which a portion of the second bead is fitted,
When the rim diameter of the rim in the first seat is the first rim diameter, and the rim diameter of the rim in the second seat is the second rim diameter,
A pneumatic tire in which the nominal diameter of the second rim in the tire is larger than the nominal diameter of the first rim. In the belt, when the point at which the axial width of the belt is equally divided into three points from the first end side of the belt is a point PB1 and a point PB2,
In the zone from the first end of the belt to the point PB1, the ratio of the distance to the width of the cross-section of the belt-like ply in the cross-section of the band is 0 or more and 0.2 or less,
In the zone from the point PB1 to the point PB2, the ratio of the distance to the width of the cross-section of the band-like ply in the cross-section of the band is 0.2 or more and 0.8 or less,
2. The air according to claim 1, wherein, in a zone from the point PB <b> 2 to the second end of the belt, a ratio of the distance to a cross-sectional width of the belt-like ply in a cross section of the band is 0.8 or more and 1 or less. Enter tire.   The pneumatic tire according to claim 1 or 2, wherein a difference between the nominal value of the second rim diameter and the nominal value of the first rim diameter is 1 inch or more and 3 inches or less.   The pneumatic tire according to any one of claims 1 to 3, wherein the first rim diameter is 16 inches or more and 20 inches or less.   The pneumatic tire according to any one of claims 1 to 4, wherein the band cord is made of an aramid fiber.

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