JP6766418B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire. Specifically, the present invention relates to a side reinforced type run-flat tire.

The development of the expressway network and the improvement of the performance of vehicles are progressing. Vehicles tend to run at high speeds for long periods of time. Tires mounted on vehicles are being developed with an emphasis on improving steering stability, riding comfort and high-speed durability.

In recent years, run-flat tires having a load-bearing layer inside the sidewall have been developed and are becoming widespread. High hardness crosslinked rubber is used for this support layer. This run-flat tire is called a side reinforcement type.

In this type of run-flat tire, when the internal pressure drops due to a flat tire, the support layer supports the vehicle weight. With run-flat tires, it is possible to travel a certain distance even in a flat tire. Vehicles equipped with these run-flat tires do not need to have spare tires on hand. This run-flat tire contributes to securing the interior space of the vehicle. Examples of such tires are disclosed in JP-A-2008-155855 and JP-A-2013-071468.

The tires are built into the rim. In this assembly, the bead portion of the tire is fitted to the rim. In the rim, the part where the bead part is fitted is called a bead sheet. The rim diameter of the rim is represented based on the outer diameter of the bead sheet.

The shape of the tire is usually symmetrical with respect to the equatorial plane, except for the tread pattern. That is, the length of the part from one sidewall to the bead (hereinafter, the first side part) is the same as the length of the part from the other sidewall to the bead (hereinafter, the second side part). is there. In the rim on which this tire is mounted, the left and right rim diameters are the same.

In a four-wheeled vehicle, tires are arranged on the right side portion of the vehicle and the left side portion thereof. For this reason, in a 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. The asymmetric tread pattern is typical.

The length of the side portion affects the deflection of the tire. The long side portion contributes to bending, and the short side portion contributes to rigidity. Therefore, for example, by configuring the first side portion to be longer than the second side portion, it is possible to control the left and right deflection of the tire and study the improvement of tire performance. Examples of this study are disclosed in, for example, Japanese Patent Application Laid-Open No. 06-092104 and Japanese Patent Application Laid-Open No. 05-139109.

In a tire configured so 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 so that the left and right rim diameters are different is used. This tire is also called a different diameter bead type.

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

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

Run-flat tires are required to be able to travel a certain distance even in a flat tire. Therefore, the support layer has a considerable thickness. This tire is considerably heavier than a normal tire. Large mass affects the rolling resistance of the tire.

With tires mounted on a vehicle, heat is more likely to be trapped in a portion located inside the vehicle in the width direction than in a portion located outside the tire. Heat affects the durability of tires. Since the run-flat tire is provided with a support layer, heat tends to accumulate. In this tire, the support layer provided for running in a punctured state (hereinafter referred to as run-flat running) may affect the durability.

As mentioned above, the short side portion contributes to the rigidity. The short side part invites a small volume. The side portion having a small volume contributes to weight reduction, and heat is less likely to accumulate in this side portion. Therefore, if the run-flat tire is a bead type with a different diameter, it may be possible to improve the durability while maintaining the rigidity of the tire appropriately and achieving both steering stability and riding comfort. However, in a different diameter bead type tire, when the tire is filled with air, there is a difference in the inflated state between the part having a small rim diameter nominal and the part having a large rim diameter nominal, and the tire There is a problem that the ground contact shape tends to be distorted. In this tire, there is a difference between the outer diameter of the portion having a small rim diameter nominal and the outer diameter of the portion having a large rim diameter nominal, which may cause a large conicity. If the rigidity of the long side portion is increased in order to suppress the increase in conicity, the riding comfort will be reduced.

An object of the present invention is to provide a pneumatic tire in which steering stability and ride comfort are improved while suppressing an increase in conicity.

The pneumatic tire according to the present invention is used by being attached to a rim. The tire comprises 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 inside the first sidewall. The second bead is located radially inside 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 inside the tread in the radial direction. The support layer is located axially inside the carcass on the side of the second sidewall. The band is located between the belt and the tread and covers the belt. The band comprises a strip-shaped ply spirally wound outward in the radial direction of the belt. The band-shaped ply includes a band cord. The cross section of the band includes a large number of cross sections of the strip-shaped ply arranged in parallel in the axial direction. In the cross section of the band, the ratio of the distance between the cross section of one strip ply and the cross section of the other strip ply located next to the cross section of the one strip ply to the width of the cross section of the strip ply is 0 or more. It is 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 into which the first bead portion is fitted and a second sheet into which the second bead portion is fitted. When the rim diameter of this rim in the first seat is the first rim diameter and the rim diameter of this rim in the second seat is the second rim diameter, the name of the second rim diameter in this tire is the first. Larger than the nominal rim diameter.

Preferably, in the pneumatic tire, when the points that divide the axial width of the belt into three equal parts are the points PB1 and the point PB2 from the side of the first end of the belt, the first of the belts. In the zone from one end to the point PB1, the ratio of the interval to the width of the cross section of the belt-shaped 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 interval to the width of the cross section of the strip-shaped 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 interval to the width of the cross section of the strip-shaped 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 second rim diameter and the nominal first rim diameter is 1 inch or more and 3 inches or less.

Preferably, in this pneumatic tire, the nominal first rim diameter is 16 inches or more and 20 inches or less.

Preferably, in this pneumatic tire, the band cord is made of aramid fibers.

In the pneumatic tire according to the present invention, the nominal diameter of the second rim is larger than the nominal diameter of the first rim. 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). This second side portion contributes to weight reduction even though it has a support layer. Although a support layer is provided on the second side portion, heat is unlikely to accumulate. This second side portion contributes to durability. By mounting this tire on the vehicle so that the second side portion is located inside, the durability can be further improved.

This tire expands so that the second side portion on the large diameter side is pulled by the first side portion on the small diameter side. The equatorial plane of the tire shifts to the smaller diameter side, and the second side part on the larger diameter side stands up. As a result, the carcass on the second side portion extends substantially along the radial direction. This carcass profile effectively contributes to tire support. Due to the increased lateral stiffness, this tire provides good steering stability. With this tire, even if the internal pressure drops due to a flat tire, the second side portion can sufficiently support the vehicle weight. With this tire, it is possible to travel a certain distance even in a flat tire state.

In this tire, the first side is longer than the second side. This first side portion contributes to bending. This tire provides a good ride because the longitudinal stiffness is properly maintained. By mounting this tire on the vehicle so that the first side portion is located on the outside, it is possible to further improve the riding comfort.

In this tire, the band covering the belt consists of a spirally wound strip ply. The cross section of this band includes a large number of cross sections of strip-shaped plies arranged in parallel in the axial direction. In this tire, the band has the width of the cross section of this strip ply, in which the distance between the cross section of one strip ply and the cross section of the other strip ply located next to the cross section of this one strip ply. It 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 a tire having this band, in the expanded state, a difference is unlikely to occur between the outer diameter of the portion having a small rim diameter nominal and the outer diameter of the portion having a large rim diameter nominal. With this tire, the increase in conicity is suppressed.

According to the present invention, it is possible to obtain a pneumatic tire in which the steering stability and the riding comfort are improved while suppressing the increase in conicity.

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

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

FIG. 1 shows the pneumatic tire 2. In detail, 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 left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. The tire 2 is incorporated in the rim 4. The inside of the tire 2 is filled with air. As a result, the internal pressure of the tire 2 is adjusted.

FIG. 2 shows the left side portion of the cross section of the tire 2 shown in FIG. FIG. 3 shows the right side portion of the cross section of the tire 2 shown in FIG. In each of FIGS. 2 and 3, the vertical direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2.

As will be described later, this tire 2 is obtained by pressurizing and heating a low cover (uncrosslinked tire 2) in a mold (not shown). At this time, the low cover is pressed against the cavity surface of the mold. As a result, 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.

In FIGS. 2 and 3, the reference numeral PE represents the radial outer end of the tire 2. This outer edge 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. The solid line EL is the equatorial plane of the tire 2. In the present invention, the equatorial plane EL is specified based on the cavity plane of the mold. As is clear from FIGS. 2 and 3, the shape of the tire 2 is asymmetric with respect to the equatorial plane.

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

The tread 6 has a shape that is convex 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. A tread pattern is formed by the groove 36. The tread 6 has a cap layer 38 and a base layer 40. The cap layer 38 is located on the outer side in the radial direction of the base layer 40. The cap layer 38 is laminated on the base layer 40. The cap layer 38 is made of crosslinked rubber having excellent wear resistance, heat resistance and grip. The base layer 40 covers the band 32. The base layer 40 is made of crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 40 is a natural rubber. In FIG. 2, reference numeral PT1 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, reference numeral PT2 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 of the pair of sidewalls 10, the sidewall 10a (first sidewall), extends substantially inward in the radial direction from the first end PT1 of the tread 6. The other sidewall 10b (second sidewall) extends substantially inward in the radial direction from the second end PT2 of the tread 6.

The radial outer portion of each sidewall 10 is joined to the tread 6. The radial inner portion of the sidewall 10 is joined to the clinch 12. The sidewall 10 is made of crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 10 prevents damage to the carcass 16.

One of the pair of clinches 12 (first clinch) is located substantially inside the first sidewall 10a in the radial direction. The other clinch 12b (second clinch) is located approximately 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 crosslinked rubber having excellent wear resistance. The clinch 12 comes into contact with the flange 42 of the rim 4.

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

Each bead 14 comprises 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 comprises an inner core 48 and an inner apex 50. Specifically, the inner part 44 is composed of 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 wire is steel. The inner apex 50 is made of high hardness crosslinked rubber. The inner apex 50 covers the inner core 48 and extends substantially outward in the radial direction from the inner core 48. The radial outer portion of the inner apex 50 has a tapered shape.

The outer part 46 comprises an outer core 52 and an outer apex 54. In particular, the outer part 46 is composed of 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 wire is steel. The outer apex 54 is made of a high hardness 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 radial outer portion of the outer apex 54 has a tapered shape.

In this tire 2, the inner apex 50 is joined to the outer apex 54 at the radial 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 is composed of one 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 consists of a number of parallel cords and topping rubber. The absolute value of the angle each code makes with respect to the equatorial plane EL is 75 ° to 90 °. In other words, the carcass 16 has a radial structure. The cord consists of organic fibers. Preferred organic fibers include polyethylene terephthalate fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. Aramid fibers are more preferred as the organic fibers for this cord from the viewpoint of obtaining a carcass 16 having high rigidity.

In this tire 2, the inner part 44 of the bead 14 is located 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 radial inner portion of the bead 14. In this tire 2, the carcass ply 56 is not folded around the bead 14 like a conventional tire. In the present invention, the structure of the carcass 16 having the carcass ply 56 whose end is sandwiched between the inner part 44 and the outer part 46 is referred to as an "insert structure". Although not shown, when the carcass is composed of carcass ply folded around the bead, the structure of this carcass is referred to as the "folded structure".

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

In this 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 consists of a number of parallel cords and topping rubbers. Each cord is inclined with respect to the equatorial plane. The general absolute value of the tilt angle is 10 ° or more and 35 ° or less. The direction of inclination of the cord of the inner layer 58 with respect to the equatorial plane is opposite to the direction of inclination of the cord of the outer layer 60 with respect to the equatorial plane. The preferred material for the cord is steel. Organic fibers may be used for the cord. Preferred organic fibers include polyethylene terephthalate fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

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. At the center of the belt 18 in the axial direction, the equatorial plane EL intersects the belt 18.

In FIG. 1, reference numerals PB1 and PB2 represent specific points on the outer surface of the belt 18. The point PB1 is on the side of the first end 62a of the belt 18, and the point PB2 is on the side of the second end 62b 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 this 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 on 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 the outer zone ZS. The zone from point PB1 to point PB2 is referred to as central zone ZC. The zone from the point PB2 to the second end 62b of the belt 18 is referred to as the inner zone ZU.

Each edge band 20 is located on the radial outside of the belt 18 and in the vicinity of the end 62 of the belt 18. Although not shown, the edge band 20 comprises a cord and a topping rubber. The cord is spirally wound. 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 consists of organic fibers. Preferred 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 soft crosslinked rubber. The cushion layer 22 absorbs the stress of the end 62 of the belt 18. The cushion layer 22 contributes to suppressing the lifting of the belt 18.

The inner liner 24 is located inside the carcass 16. In the vicinity of the equatorial plane, the inner liner 24 is joined to the inner surface of the carcass 16. The inner liner 24 is made of 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 holds 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 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 suppresses the peeling of the inner liner 24 inside the sidewall 10 in the axial direction.

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. This contact protects the vicinity of the bead 14. 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 consist of a cloth and rubber impregnated in the cloth.

One of the support layers 30a (first support layer) of the pair of support layers 30 is located axially inside the first sidewall 10a. The first support layer 30a is located on the side of the first sidewall 10a on the inner side in the axial direction of the carcass 16. The other support layer 30b (second support layer) is located axially inside the second sidewall 10b. The second support layer 30b is located axially inside the carcass 16 on the side of the second sidewall 10b. Each support layer 30 is sandwiched between the carcass 16 and the inner liner 24. The support layer 30 is located radially outside 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 is tapered inward and tapered outward in the radial direction. The support layer 30 has a shape similar to that of a crescent moon. The support layer 30 is made of crosslinked rubber. When the tire 2 is punctured, the support layer 30 supports the vehicle weight. Due to the support layer 30, the tire 2 can travel a certain distance even in a punctured state. This tire 2 is also called a run-flat tire. This tire 2 is a side reinforcement type.

In this tire 2, the hardness of the support layer 30 is preferably 60 or more and 85 or less. By setting this hardness to 60 or more, when the internal pressure of the tire 2 is reduced due to a flat tire, the support layer 30 can effectively contribute to the support of the vehicle weight. From this point of view, the hardness is more preferably 65 or more. By setting this hardness to 85 or less, the influence of the support layer 30 on the bending of the sidewall 10 portion is suppressed. With this tire 2, the riding comfort is properly 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 by a type A durometer in an environment of 23 ° C. in accordance with the provisions of "JIS-K6253". More specifically, hardness is measured by pressing a type A durometer onto the cross section shown in FIGS. 2 and 3.

The band 32 is located on the outer side of the belt 18 in the radial direction. 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 is composed of a band cord and a topping rubber. The band cord is wound in a spiral. 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 this band cord, the lifting of the belt 18 is suppressed. The band cord is made of organic fibers. Preferred organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. From the viewpoint that a band 32 having an appropriate rigidity can be obtained, a cord made of aramid fiber is more preferable as the band cord. The band 32 contributes to weight reduction and reduction of rolling resistance.

Although not shown, the band cord is composed of a plurality of yarns twisted together. 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 preferably 3 or less. The number of times the raw yarn is twisted is preferably 40 times / 10 cm or more, and preferably 80 times / 10 cm or less. Further, when a cord made of aramid fiber is used for the band cord, the fineness of this raw yarn is preferably 600 dtex or more, 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 by using the band-shaped ply 64 shown in FIG. The band 32 includes a band-shaped ply 64. The strip-shaped ply 64 is in the form of a tape. The band-shaped ply 64 includes a band cord 66, and the band cord 66 is covered with a topping rubber 68. In other words, the band-shaped ply 64 includes a band cord 66 and a topping rubber 68.

The band-shaped ply 64 shown in FIG. 4 includes a plurality of band cords 66. Specifically, the strip ply 64 includes five band cords 66. These band cords 66 are arranged in parallel in the width direction of the band-shaped ply 64.

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

In FIG. 4, the double-headed arrow WP is the width of the strip-shaped ply 64. In the tire 2, the width WP of the strip-shaped ply 64 is not particularly limited, but usually this width WP is appropriately set in the range of 5 mm or more and 30 mm or less. The width WP of the strip-shaped ply 64 is synonymous with the width of the cross section of the strip-shaped ply 64, which will be described later.

In the tire 2, the band 32 moves the band-shaped ply 64 to the outside of the belt 18 in the radial direction, for example, from the side of the first end 62a of the belt 18 toward the side of the second end 62b, or the belt 18. It is formed by spirally winding from the side of the second end 62b toward the side of the first end 62a. 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 band-shaped ply 64, and these cross sections are in the axial direction. Is parallel to.

FIG. 5 shows the cross section of the band 32 along 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 left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 5, the double-headed arrow DP is the distance between the cross section of one strip ply 64 and the cross section of the other strip ply 64 located next to the cross section of this one strip ply 64.

As shown in FIG. 5, in the outer zone ZS, there is a gap between the cross section of one strip ply 64 and the cross section of the other strip ply 64 located next to the cross section of this one strip ply 64. They are lined up without. In the central zone ZC, a gap is provided between the cross section of one strip ply 64 and the cross section of the other strip ply 64 located next to the cross section of this one strip ply 64. That is, the interval DP in the central zone ZC (hereinafter, also referred to as interval DPC) is larger than the interval DP in the outer zone ZS (hereinafter, also referred to as interval DPS). In the inner zone ZU, the gap in the above-mentioned central zone ZC is between the cross section of one strip ply 64 and the cross section of the other strip ply 64 located next to the cross section of this one strip ply 64. There is a larger gap than. 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. As described above, in the tire 2, the winding pitch of the band-shaped ply 64 in each zone is adjusted when the band 32 is formed.

The tire 2 described above is used by being mounted on the rim 4 and being filled with air. As the rim 4, for example, a halved rim is used. The rim 4 includes a pair of half rims 70. Each half rim 70 includes a bead seat 72. The bead 14 portion of the tire 2 is fitted to the bead sheet 72. 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 the 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 a first seat 72a. The other half rim 70b (second half rim) includes a second seat 72b. The rim 4 includes a first sheet 72a and a second sheet 72b.

In the tire 2, the portion from the first sidewall 10a to the first bead 14a (first side portion 76a) is the portion from the second sidewall 10b to the second bead 14b (second side portion 76b). ) Has a length larger than the length. Therefore, when the rim diameter of the rim 4 on the first sheet 72a is the first rim diameter and the rim diameter of the rim 4 on the second sheet 72b is the second rim diameter, the first rim diameter is larger 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. Therefore, in this tire 2, the nominal diameter of the rim on the large diameter side (that is, the nominal D2 of the second rim diameter) is larger than the nominal diameter of the rim diameter on the small diameter side (that is, the nominal D1 of the first rim diameter). This tire 2 is a different diameter bead type. In the present invention, the "nominal rim diameter" is synonymous with the "nominal rim diameter" included in the "nominal tire" in the JATTA standard.

In the present invention, the shape of the rim 4 on which the tire 2 is mounted is peculiar as compared with the shape of a normal rim (hereinafter referred to as a regular rim) having the same left and right rim diameters. This rim 4 is special. For the tire 2 of the present invention, for example, by preparing two split type regular rims having different rim diameters and combining the half rim 70a of one regular rim and the half rim 70b of the other regular rim, this is achieved. The rim 4 can be configured. Since the rim 4 configured in this way is configured by combining two regular rims, in the present invention, the rim according to the regular rim is also referred to as a semi-regular rim. Further, as used herein, the term "regular rim" means a rim defined in the standard on which Tire 2 relies. The "standard rim" in the JATTA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims.

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

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

In this manufacturing method, a strip ply 64 is prepared for the formation of the band 32. Then, as described above, in each of the outer zone ZS, the central zone ZC, and the inner zone ZU, the band-shaped ply 64 is spirally formed on the outer side in the radial direction of the belt 18 while adjusting the winding pitch of the band-shaped ply 64. The band 32 is formed by winding around.

In this manufacturing method, the low cover is charged into a mold (not shown) together with the core. After loading, the mold is closed. The inner surface of the low cover is in contact with the core. The outer surface of the low cover is in contact with the cavity surface of the mold. The low cover is sandwiched between the cavity surface of the mold and the outer surface of the core and pressed. The low cover is pressurized and heated in the mold. The low cover rubber composition flows by pressurization and heating. The rubber undergoes a cross-linking reaction by heating, and the tire 2 is obtained. The method of manufacturing the tire 2 using the core in this way is also called the core method.

As described above, in the tire 2, a cord made of aramid fibers (hereinafter, aramid cord) is preferably adopted for the members such as the carcass 16 and the band 32 from the viewpoint of rigidity. The adoption of this aramid cord contributes to the reduction of rolling resistance and the improvement of durability in a punctured state. However, the elongation of this aramid cord is quite small. Therefore, it is difficult to manufacture the tire 2 including the member containing the aramid cord by the manufacturing method including the step of inflating the low cover and adjusting its shape, that is, the shaping step. On the other hand, in the core method, it is not necessary to inflate the low cover to adjust its shape. In this core construction method, the tire 2 can be molded without changing the shape of the low cover. According to this core construction method, the tire 2 can be stably manufactured even if a member including an aramid cord having a small elongation is used. This core method contributes to the reduction of rolling resistance of the tire 2 and the improvement of durability in a punctured state.

As described above, the shape of the tire 2 is asymmetric with respect to the equatorial plane EL. The shape of the tire 2 can be formed, for example, by combining two tires having the same nominal cross-sectional width but different nominal aspect ratios and different rim diameters on their respective equatorial planes. Specifically, for example, the shape of the tire represented by the "tire designation" of 245 / 45R18 constitutes the shape on the small diameter side, and the shape of the tire represented by the "tire designation" of 245 / 35R20. 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 the "nominal tire" of 245 / 45R18 and the outer surface of the tire represented by the "nominal tire" of 245 / 35R20. The outer surface of the core reflects the inner surface of the tire 2 represented by the "tire designation" of 245 / 45R18 and the inner surface of the tire represented by the "tire designation" of 245 / 35R20.

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

A support layer 30 is provided on the side portion 76 of the tire 2. Therefore, heat tends to accumulate in the side portion 76. However, in this 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. Although the second support layer 30b is provided on the second side portion 76b, heat is unlikely to accumulate in the second side portion 76b. 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 inside, 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 mentioned above, the carcass 16 of the tire 2 contains a large number of cords. Due to the expansion, tension acts on each cord. In the inflated tire 2, the tension acting on these cords is uniform.

In FIG. 1, the 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 this rim width WR. The alternate long and short dash line CL is the center line in the width direction of the rim 4. In the manufacture of the tire 2, a mold having a cavity surface arranged so that the equatorial surface EL substantially coincides with the center line CL in the axial direction is used. In a conventional tire having the same nominal diameter on the left and right rims, when the inside is filled with air and the tire is expanded, the equatorial 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 expanded so that its large diameter side is pulled toward the small diameter side. Therefore, the equatorial plane EL of the tire 2 is shifted to the small diameter side, and the second side portion 76b on the large diameter side stands up. In the inflated tire 2, the carcass 16 on the second side portion 76b extends substantially along the radial direction. The profile of the carcass 16 (also referred to as the carcass line) effectively contributes to the support of the tire 2. Since the lateral rigidity is increased, good steering stability can be obtained with this tire 2. In the tire 2, even if the internal pressure is lowered due to a flat tire, the second side portion 76b can sufficiently support the vehicle weight. With this tire 2, it is possible to travel a certain distance even in a punctured state.

In this 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 vertical rigidity is properly maintained, a good ride comfort can be obtained with this tire 2. By mounting the tire 2 on the vehicle so that the first side portion 76a is located on the outside, the riding comfort can be further improved.

In the tire 2, the band 32 includes a band-shaped ply 64 spirally wound outward in the radial direction of the belt 18. Specifically, the band 32 comprises a strip-shaped ply 64 spirally wound outward in the radial direction of the belt 18. The cross section of the band 32 includes a large number of cross sections of the strip-shaped plies 64 arranged in parallel in the axial direction.

In the tire 2, in the cross section of the band 32, the distance DP between the cross section of one strip ply 64 and the cross section of the other strip ply 64 located next to the cross section of this one strip ply 64 is appropriately adjusted. Has been done. Specifically, the ratio of the interval DP to the width WP of the cross section of the strip-shaped ply 64 is 0 or more and 1 or less. By setting this ratio to 0 or more, the cross section of one strip ply 64 and the cross section of the other strip ply 64 located next to the cross section of this one strip ply 64 do not overlap. The band 32 is formed. In this tire 2, the influence of the band 32 on the mass 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 this tire 2, by setting the ratio of the interval DP to the width WP to 0 or more and 1 or less, preferably, by setting this ratio to 0.0 or more and 1.0 or less, the mass of the tire 2 is increased. And the binding force of this band 32 are well-balanced.

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

FIG. 6 shows the usage state of the tire 2. In FIG. 6, what is shown by the solid line is the outline of the tire 2. What is shown by a dotted line is the outline of a tire 78 (hereinafter, referred to as a reference tire) having a band formed by spirally winding a strip-shaped ply at a constant pitch. Both contours have been confirmed with the tires 2 and 78 incorporated into the semi-regular rim and the internal pressure adjusted to 230 kPa. Except for the band of the reference tire 78, it has the same configuration as the tire 2 shown in FIG. 1-3. 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 strip-shaped ply cross section and the cross section of the one strip-shaped ply are next to each other. It is arranged at equal intervals with the cross section of the other strip-shaped ply located in. In this band, the rigidity on the side of the first end of the belt is equivalent to the rigidity on the side of the second end. 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 side portion is larger than the degree of swelling of the right side portion. In this reference tire 78, since the rigidity of the band is uniform in the axial direction, this difference in the degree of swelling is due to the fact that the rigidity of the first side portion is smaller than that of the second side portion. It is believed that. In this reference tire 78, since the outer diameter of the left side portion is larger than the outer diameter of the right side portion, the left side, that is, from the side of the first end of the belt (not shown) to the right side, that is, the side of the second end. A large conicity is generated toward it.

On the other hand, in the tire 2 of the present invention, the band 32 has a cross section of one strip ply 64 and another cross section of the strip ply 64 located next to the cross section of the strip ply 64 in the cross section thereof. The distance DP with and from is set to 0 or more and 1 or less with respect to the width WP of the cross section of the strip-shaped ply 64, and the distance DP on the side of the second end 62b 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 this tire 2, as shown in FIG. 6, with respect to the swelling of the tire 2 due to air filling, the degree of swelling of the first end 62a side of the belt 18, that is, the left side portion is the side of the second end 62b. That is, it is almost the same as the degree of swelling of the right side portion. In the tire 2 having the band 32, in the expanded state, the outer diameter of the left side portion, that is, the portion having a small rim diameter designation is different from the outer diameter of the right side portion, that is, the portion having a large rim diameter designation. Is unlikely to occur. With this tire 2, the increase in conicity is suppressed.

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

In the tire 2, the number of band-shaped plies 64 used for forming the band 32 is not particularly limited. For example, three strip-shaped 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 strip-shaped ply 64, or the entire band 32 may be formed by one strip-shaped ply 64. May be formed with. From the viewpoint that the band 32 effectively restrains the belt 18, it is preferable that the entire band 32 is composed of one band-shaped ply 64. In this case, the interval DP of the strip ply 64 is gradually changed from the interval DPS to the interval DPC at the boundary between the outer zone ZS and the central zone ZC, and from the interval DPC at the boundary between the central zone ZC and the inner zone ZU. It is gradually changed to the interval DPU.

As described above, in the tire 2, the band 32 has, in its cross section, one cross section of the strip ply 64 and another cross section of the strip ply 64 located next to the cross section of the one strip ply 64. The interval DP is set to be 0 or more and 1 or less with respect to the width WP of the cross section of the strip-shaped ply 64, and the interval DP on the side of the second end 62b of the belt 18 is on the side of the first end 62a of the belt 18. It is configured to be larger than the interval DP in. In particular, in this tire 2, the interval DPC in the central zone ZC is larger than the interval DPS in the outer zone ZS, and the interval DPU in the inner zone ZU is larger than the interval DPC in the central zone ZC. As a result, with respect to the swelling of the tire 2 due to 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 of the long first side portion 76a during expansion is larger than that of the short second side portion 76b. Therefore, the left side portion of the tire 2 on which the first side portion 76a is arranged tends to expand.

In this tire, the ratio of the interval DPS of the band-shaped ply 64 to the width WP of the band-shaped ply 64 in the outer zone ZS is preferably 0.2 or less. The band 32 effectively suppresses the swelling of the left side 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 the increase in conicity is suppressed. From this point of view, this ratio is 0, i.e., as shown in FIG. 5A, the strip ply 64 is preferably wound tightly. More preferably, this ratio is 0.0.

In this tire 2, the deformation allowance of the short second side portion 76b at the time of expansion is smaller than that of the long first side portion 76a. Therefore, the right side portion of the tire 2 on which the second side portion 76b is arranged is unlikely to expand. Therefore, in the inner zone ZU, if the interval DPU of the strip-shaped ply 64 is small, the expansion of the right side portion of the tire 2 is excessively suppressed, and on the contrary, the balance of the left and right expansion may be lost.

In this tire 2, the ratio of the interval DPU of the strip-shaped ply 64 to the width WP of the strip-shaped ply 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 the increase in conicity is suppressed. This ratio is preferably 1 or less from the viewpoint that the binding force of the belt 18 by the band 32 is secured and good high-speed durability and steering stability are maintained. More preferably, this ratio is 1.0 or less.

In the tire 2, the interval DPC of the strip-shaped ply 64 in the central zone ZC also affects the expansion of the tire 2. That is, if this interval 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 this interval DPC is large, the expansion of the tire 2 cannot be sufficiently suppressed, and even in this case, the left and right expansion cannot be adjusted in a well-balanced manner. Moreover, since the rigidity of the band 32 is insufficient, there is a risk that performance such as steering stability will deteriorate.

In this tire 2, the central zone ZC is obtained from the viewpoint that the left side portion and the right side portion of the tire 2 achieve the same degree of swelling, the increase in conicity is suppressed, and good steering stability is maintained. The ratio of the interval DPC of the strip ply 64 to the width WP of the strip ply 64 in the above is preferably 0.2 or more, and preferably 0.8 or less. 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. From this viewpoint, the difference (D2-D1) between the nominal D2 of the second rim diameter and the nominal D1 of the first rim diameter is preferably 1 inch or more. The difference (D2-D1) is preferably 3 inches or less from the viewpoint that the carcass line is maintained and the straight running stability and the deterioration of the wear resistance are prevented.

As described above, in this 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 vertical rigidity is suppressed, a good ride comfort can be obtained with this tire 2. 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 of the long first side portion 76a on the steering stability is suppressed, the nominal D1 of the first rim diameter is preferably 16 inches or more.

As described above, in this 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, this tire 2 provides good steering stability and run-flat durability. From this point of view, the nominal D2 of the second rim diameter is preferably 17 inches or more. From the viewpoint of suppressing the influence of the short second side portion 76b on the wear resistance and riding comfort, the nominal D2 of the second rim diameter is preferably 23 inches or less.

In FIG. 1, the solid line BL1 is the first baseline. The first baseline 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 axially. The solid line BL2 is the second baseline. The second baseline corresponds to the line defining the second rim diameter of the rim 4. This second baseline extends axially.

In FIG. 1, the double-headed arrow H1 represents the radial height from the first baseline to the radial outer end PE of the tire 2. This height H1 is the cross-sectional height of the tire 2 obtained with reference to the first baseline. The double-headed arrow H2 represents the radial height from the second baseline to the radial outer end PE of the tire 2. This height H2 is the cross-sectional height of the tire 2 obtained with reference to the second baseline. The double-headed arrow W represents the maximum width of the tire 2 in the axial direction. This width W is the 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 becomes 180 kPa. W is measured. In this specification, the normal internal pressure means "maximum air pressure" in the JATTA standard, "maximum value" in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and "INFLATION PRESSURE" in the ETRTO standard. To do.

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

In this tire 2, from the viewpoint of riding comfort and steering stability, the first flatness ratio F1 is preferably 0.40 or more, and preferably 0.70 or less. Further, from the viewpoint of suppressing the influence of the carcass line on the wear resistance, the first flatness ratio F1 is more preferably 0.45 or more, and more preferably 0.65 or less.

In this tire 2, from the viewpoint of steering stability and run-flat durability, the second flatness ratio F2 is preferably 0.30 or more, and preferably 0.60 or less. Further, from the viewpoint that the wear resistance can be further improved, the second flatness 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 load larger than that of the outer portion tends to act on the inner portion in the width direction of the vehicle. In particular, when the equator is mounted on the vehicle so as to be inclined with respect to the vertical line, this tendency is remarkable when the camber angle is set to negative camber in detail. 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 located on the outer side in the width direction (also referred to as the front side or the S side) of the vehicle, and the second side portion 76b is the vehicle. It is preferable that the tire 2 is mounted on a four-wheeled vehicle so as to be located on the inner side in the width direction (also referred to as the back side or the NS side). In this case, since the first side portion 76a is arranged on the outer side in the width direction of the vehicle, which contributes less to the run-flat durability, a thin first support layer 30a can be adopted, further reducing the weight and weight. The rolling resistance can be further reduced. In some cases, the first support layer 30a can be removed from the first side portion 76a, and in this case, the weight can be further reduced and the rolling resistance can be further reduced.

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

[Example 1]
The tire shown in Fig. 1-3 was manufactured. In this Example 1, the nominal D1 of the first rim diameter is 18 inches, as shown in Table 1 below. The nominal D2 of the second rim diameter is 20 inches.

As the band cord, a cord made of aramid fiber (composition = 800 dtex / 2, number of twists = 60 times / 10 cm) was adopted. This is represented as "aramid" in the band code column of Table 1.

A band-shaped ply having a width WP set to 10 mm was used for forming the band. 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 located next to the cross section of this one strip ply. The ratio of the interval 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 flatness ratio F1 and the second flatness ratio F2 are as shown in Table 1 below. The cross-sectional width W was set to 245 mm.

In the first embodiment, a carcass having an "insert structure" is adopted. This is indicated by an "I" in the "Carcass structure" column of the table. As the cord contained in this carcass, a cord made of aramid fiber is used. For the cord included in the belt, a cord whose material is steel is used. This Example 1 is manufactured by the core method.

[Comparative Example 1-4]
Comparative Examples 1-4 are conventional tires. The shape of these tires is symmetrical with respect to the equatorial plane. The cross-sectional width W is 245 mm in each case. The flatness ratio F1, the nominal D1 of the first rim diameter, the flatness ratio F2, and the nominal D2 of the second rim diameter are as shown in Table 1 below. In Comparative Examples 1-4, the entire band is formed by using the band-shaped 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, central and inner zones. That is, the band-shaped ply was spirally wound without gaps to form the entire band. In Comparative Examples 1 and 2, a carcass having a "folded structure" is adopted. This is indicated by an "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 adopted.

[Comparative Example 5-7]
Comparative examples except that the flatness ratio F2 and the difference (D2-D1) between the nominal D2 of the second rim diameter and the nominal D1 of the first rim diameter were changed as shown in Table 1 below by changing the nominal D2 of the second rim diameter. The tire of Comparative Example 5-7 was obtained in the same manner as in 3.

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

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

[Example 5-6]
The tires of Example 5-6 were obtained in the same manner as in Example 1 except that the ratio of the outer zones (DP / WP) was set as shown in Table 3 below.

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

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

[Example 14-18]
The same as in Example 1 except that the nominal D1 of the first rim diameter and the nominal D2 of the second rim diameter are changed so that the flatness ratio F1, the flatness ratio F2 and the difference (D2-D1) are as shown in Table 6 below. The tires of Examples 14-18 were obtained.

[Example 19]
The 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)]
The rolling resistance coefficient (RRC) was measured under the following measurement conditions using a rolling resistance tester (drum diameter = 1.7 m, drum surface = smooth steel). For the rim, the first half rim (made of aluminum alloy) is selected by referring to the nominal D1 of the first rim diameter, and the second half rim (made of aluminum alloy) is selected by referring to the nominal D2 of the second rim diameter. Then, a halved rim (quasi-regular rim) composed by combining the first half rim and the second half rim was used. For 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 shown in the index in Table 1-6 below. The larger the value, the more preferable, that is, the smaller the rolling resistance coefficient (RRC).

[Tire mass]
The mass of one tire was measured. The results are shown in the index in Table 1-6 below. The larger the value, the more preferable, that is, the smaller the mass.

[Ride comfort and steering stability]
The tire was assembled into the rim and the tire was filled with air so that the internal pressure was 230 kPa. This tire was installed in a commercially available hybrid type passenger car. This tire was mounted so that the small diameter side of the tire was located on the outside (S side) in the width direction of the vehicle and the large diameter side was located on the inside (NS side) in the width direction of the vehicle. For the rim, the semi-regular rim used for measuring the rolling resistance coefficient was used. The driver was allowed to drive this passenger car on a racing circuit to evaluate ride comfort and steering stability. Only the driver is in this passenger car. The results are shown in the index in Table 1-6 below. The larger the value, the more preferable.

[Conicity]
Connicity (CON) was measured under the conditions shown below in accordance with the uniformity test method specified in "JASO C607: 2000". Measurements were made for 10 tires, and the average value of the measurement results is shown in Table 1-6 below as an index. The closer this value is to 0, the more the occurrence of conicity is suppressed, which is preferable. For the rim, the semi-regular rim used for measuring the rolling resistance coefficient was used.
Rim width: 8.5 inches Internal pressure: 210 kPa
Load: 5.3kN
Speed: 60 rpm

As shown in Table 1-6, the tires of Examples have a higher evaluation than the tires of Comparative Examples. From this evaluation result, the superiority of the present invention is clear.

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

2 ... Tires 4 ... Rims 6 ... Treads 10, 10a, 10b ... Sidewalls 12, 12a, 12b ... Clinch 14, 14a, 14b ... Beads 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 ・ ・ ・Belt 18 end 64 ... Band-shaped ply 66 ... Band cord 68 ... Topping rubber 70, 70a, 70b ... Half rim 72, 72a, 72b ... Bead sheet 74, 74a, 74b ... Bead Parts 76, 76a, 76b ... Side parts

Claims (4)

Tires that are used by attaching to the rim
It has a tread, first sidewall, second sidewall, first bead, second bead, carcass, belt, support layer and band.
The first sidewall extends substantially inward in the radial direction from the first end of the tread, and the second sidewall extends substantially inward in the radial direction from the second end of the tread.
The first bead is located radially inside the first sidewall, and the second bead is located radially inside 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 inside the tread in the radial direction.
The support layer is located on the side of the second sidewall and inside the carcass in the axial direction.
The band is located between the belt and the tread and covers the belt.
The band comprises a band-shaped ply spirally wound outward in the radial direction of the belt.
The band-shaped ply contains the band cord,
The cross section of the band includes a large number of cross sections of the strip-shaped ply arranged in parallel in the axial direction.
In the cross section of the band, the ratio of the distance between the cross section of one strip ply and the cross section of the other strip ply located next to the cross section of the one 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 comprises a first sheet into which the first bead portion is fitted and a second sheet into which the second bead portion is fitted.
When the rim diameter of this rim in the first sheet is the first rim diameter and the rim diameter of this rim in the second sheet is the second rim diameter,
Call of the second rim diameter much larger than the nominal of the first rim diameter of the tire,
In the above belt, when the points that divide the axial width of the belt into three equal parts are the points PB1 and the point PB2 from the side of the first end of the belt.
In the zone from the first end of the belt to the point PB1, the ratio of the interval to the width of the cross section of the strip-shaped 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 interval to the width of the cross section of the strip-shaped ply in the cross section of the band is 0.2 or more and 0.8 or less.
A pneumatic tire in which the ratio of the interval to the width of the cross section of the strip-shaped ply in the cross section of the band in the zone from the point PB2 to the second end of the belt is 0.8 or more and 1 or less . The pneumatic tire according to claim 1 , wherein the difference between the nominal second rim diameter and the nominal first rim diameter is 1 inch or more and 3 inches or less. The pneumatic tire according to claim 1 or 2 , 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 3 , wherein the band cord is made of aramid fiber.

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