JP6662045B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In recent years, run flat tires having a load support layer inside a sidewall have been developed and are becoming popular. A 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 decreases due to puncture, the support layer supports the vehicle weight. The run flat tire can travel a certain distance even in a punctured state. A vehicle equipped with the run flat tire does not require a spare tire. 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.

JP 2008-155855 A JP 2013-071468 A

  As described above, the support layer is made of a high-hardness crosslinked rubber. The support layer is hard. A rigid support layer affects longitudinal rigidity. A tire having this support layer is unlikely to bend. For this reason, a run flat tire is inferior in ride comfort to a normal tire without this support layer.

  A soft support layer facilitates deformation of the tire. For this reason, the ride comfort of the tire is improved by employing the soft support layer. However, the degree of deformation of this tire in a punctured state is greater than that of a run flat tire having a hard support layer. The large deformation affects the durability of the tire in a punctured state (also referred to as run flat durability). It is difficult to improve ride comfort of run-flat tires without impairing run-flat durability.

  An object of the present invention is to provide a pneumatic tire in which ride comfort is improved without impairing run-flat durability.

  The pneumatic tire according to the present invention is mounted on a rim. The tire includes a tread, a first sidewall, a second sidewall, a first bead, a second bead, a carcass, and a support layer. The first sidewall extends substantially inward in the radial direction from a first end of the tread. The first bead is located radially inward of the first sidewall. The second sidewall extends substantially inward in the radial direction from the second end of the tread. The second bead is located radially inward of the second sidewall. The carcass is bridged between the first bead and the second bead along the inside of the first sidewall, the tread, and the second sidewall. On the side of the first sidewall, the support layer is located inside the carcass in the axial direction. The rim includes a first sheet and a second sheet. The first bead portion is fitted to the first sheet. The portion of the second bead is fitted to the second sheet. When the rim diameter of the rim in the first sheet is a first rim diameter and the rim diameter of the rim in the second sheet is a second rim diameter, the first rim diameter of the tire is called the second rim diameter. Larger than the nominal rim diameter. The inner portion of the carcass on the side of the second sidewall is thinner than the inner portion of the carcass on the side of the first sidewall.

  Preferably, in the pneumatic tire, the ratio of the maximum thickness to the thickness of the outer portion of the carcass at the position where the support layer exhibits the maximum thickness is 3 or more and 5 or less.

  Preferably, in the pneumatic tire, when the axially outer end on the side of the first sidewall is a first reference point, and the axially outer end on the side of the second sidewall is a second reference point, The ratio of the thickness of the inner part of the carcass at the second reference point to the thickness of the inner part of the carcass at the first reference point is 0.9 or less.

  Preferably, in the pneumatic tire, the equator of the tire is located between the center of the tire and the second end in the axial direction.

  Preferably, in the pneumatic tire, a difference between a length from the first reference point to the equator and a length from the first reference point to the center is 5 mm or more and 15 mm or less.

  In the pneumatic tire according to the present invention, the nominal of the first rim diameter is larger than the nominal of the second rim diameter. In other words, in this tire, a portion from the first sidewall to the first bead (hereinafter, first side portion) is shorter than a portion from the second sidewall to the second bead (hereinafter, second side portion). .

  In this tire, a load supporting layer is provided on a short first side portion. This support layer contributes to bending rigidity. In this tire, the deformation of the first side portion is suppressed. Since the small deformation suppresses heat generation, the first side portion is not easily damaged. This first side portion contributes to run flat durability.

  In this tire, the inner part of the carcass on the side of the second sidewall is thinner than the inner part of the carcass on the side of the first sidewall. Moreover, the second side portion is longer than the first side portion. The second side is thin and long. This second side portion is easily bent. This second side portion contributes to ride comfort.

  In this tire, the first side portion contributes to run flat durability, and the second side portion contributes to ride comfort. With this tire, the ride comfort is improved without impairing the run flat durability.

  In a tire mounted on a vehicle, a portion located inside the vehicle (hereinafter, the rear side of the tire) is less likely to radiate heat than a portion located outside the same (hereinafter, the front side of the tire). For this reason, the rear side of the tire is more easily damaged than the front side. In particular, in running in a punctured state, that is, in run flat running, the rear side of the tire is easily damaged.

  As described above, in the tire of the present invention, the first side portion contributes to run flat durability, and the second side portion contributes to ride comfort. Therefore, by mounting the tire on the vehicle such that the first side portion is located inside the vehicle, the effect of the tire is sufficiently exhibited.

FIG. 1 is a sectional view showing a part of a pneumatic tire according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing a right side portion of the tire of FIG. FIG. 3 is a cross-sectional view illustrating a left side portion of the tire of FIG. 1. FIG. 4 is a schematic diagram showing an outline of the tire shown in FIG. 1 in a use state. FIG. 5 is a sectional view showing a right side portion of a pneumatic tire according to another embodiment of the present invention. FIG. 6 is a cross-sectional view showing a left portion of the tire of FIG.

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

[First embodiment]
FIG. 1-3 shows the pneumatic tire 2. FIG. 2 shows a right side portion of the cross section of the tire 2 shown in FIG. FIG. 3 shows a left portion of the cross section of the tire 2 shown in FIG. In each of FIGS. 1-3, the up-down 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. 1, reference symbol PE represents a radially outer end of the tire 2. This outer end PE is also called the equator. In FIG. 1, the solid line CL passes through the equator PE. The solid line CL extends in the radial direction. In FIG. 1, a solid line CL is the equatorial plane of the tire 2.

  The tire 2 includes a tread 4, a penetrating portion 6, a pair of sidewalls 8, a pair of clinches 10, a pair of beads 12, a carcass 14, a belt 16, a pair of edge bands 18, a band 20, a pair of cushion layers 22, A liner 24, a pair of insulations 26, a pair of chafers 28, and a load support layer 30 are provided. The tire 2 is a tubeless type. The tire 2 is for a passenger car.

  The tread 4 has a shape convex outward in the radial direction. The outer surface of the tread 4 forms a tread surface 32 that contacts the road surface. A groove 34 is formed in the tread 4. The grooves 34 form a tread pattern. The tread 4 has a base layer 36 and a cap layer 38. The cap layer 38 is located radially outside the base layer 36. The cap layer 38 is laminated on the base layer 36. The base layer 36 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 36 is a natural rubber. The cap layer 38 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  The penetrating part 6 is made of conductive crosslinked rubber. The penetrating part 6 penetrates the tread 4. One end of the penetrating portion 6 is exposed on the tread surface 32. The other end of the penetrating portion 6 is in contact with the band 20. In the tire 2, the penetrating portion 6 extends in the circumferential direction.

  In FIG. 2, reference symbol PT1 represents a specific position on the outer surface of the tire 2. This position PT1 is one axially outer end of the outer surface of the tread 4. In the tire 2, this position PT1 is also a boundary between the tread 4 and one sidewall 8a (first sidewall). In the present invention, this position PT1 is referred to as the first end of the tread 4. In FIG. 3, reference symbol PT2 represents a specific position on the outer surface of the tire 2. This position PT2 is the other axially outer end of the outer surface of the tread 4. In the tire 2, this position PT2 is also a boundary between the tread 4 and the other sidewall 8b (second sidewall). In the present invention, this position PT2 is referred to as the second end of the tread 4.

  In the tire 2, the first sidewall 8a extends substantially inward in the radial direction from the first end PT1 of the tread 4. The second sidewall 8b extends substantially inward in the radial direction from the second end PT2 of the tread 4.

  A radially outer portion of each sidewall 8 is joined to the tread 4. A radially inner portion of the sidewall 8 is joined to the clinch 10. The sidewall 8 is made of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 8 prevents the carcass 14 from being damaged.

  One clinch 10a (first clinch) of the pair of clinches 10 is located radially inward of the first sidewall 8a. The other clinch 10b (second clinch) is located radially inside the second sidewall 8b.

  Each clinch 10 is located outside the bead 12 and the carcass 14 in the axial direction. The clinch 10 is made of a crosslinked rubber having excellent wear resistance. The clinch 10 abuts the flange of the rim.

  One bead 12a (first bead) of the pair of beads 12 is located inside the first clinch 10a in the axial direction. As described above, the first clinch 10a is located radially inside the first sidewall 8a. The first bead 12a is located inside the first sidewall 8a in the radial direction. The other bead 12b (second bead) is located inside the second clinch 10b in the axial direction. As described above, the second clinch 10b is located inside the second sidewall 8b in the radial direction. The second bead 12b is located inside the second sidewall 8b in the radial direction.

  Each bead 12 has an inner part 40 and an outer part 42. The outer part 42 is located outside the inner part 40 in the axial direction.

  The inner part 40 includes an inner core 44 and an inner apex 46. Specifically, the inner part 40 includes an inner core 44 and an inner apex 46. The inner core 44 has a ring shape. Although not shown, the inner core 44 includes a wound non-stretchable wire. A typical material of the wire is steel. The inner apex 46 is made of a high-hardness crosslinked rubber. The inner apex 46 covers the inner core 44 and extends radially outward from the inner core 44. The radially outer portion of the inner apex 46 has a tapered shape.

  The outer part 42 includes an outer core 48 and an outer apex 50. Specifically, the outer part 42 includes an outer core 48 and an outer apex 50. The outer core 48 has a ring shape. Although not shown, the outer core 48 includes a wound non-stretchable wire. A typical material of the wire is steel. The outer apex 50 is made of a high-hardness crosslinked rubber. The outer apex 50 covers the outer core 48 and extends substantially radially outward from the outer core 48. A radially outer portion of the outer apex 50 has a tapered shape.

  In the tire 2, the inner apex 46 is joined to the outer apex 50 at the radially inner portion of each bead 12. In this portion, the inner apex 46 and the outer apex 50 are formed integrally.

  The carcass 14 includes a carcass ply 52. The carcass 14 of the tire 2 includes one carcass ply 52. The carcass 14 may be formed from two or more carcass plies 52.

  The carcass ply 52 is bridged between the first bead 12a and the second bead 12b. The carcass ply 52 extends along the inside of the first sidewall 8a, the tread 4, and the second sidewall 8b. Although not shown, the carcass ply 52 is composed of a number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each code with respect to the equatorial plane is 75 ° to 90 °. In other words, the carcass 14 has a radial structure. The cord is made of organic fibers. Preferred organic fibers include polyethylene terephthalate fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber and aramid fiber. From the viewpoint that a carcass 14 having high rigidity is obtained, an aramid fiber is more preferable as the organic fiber for this cord.

  In this tire 2, the inner part 40 of the bead 12 is located inside the carcass ply 52 in the axial direction. The outer part 42 is located outside the carcass ply 52 in the axial direction. Specifically, the end of the carcass ply 52 is sandwiched between the inner part 40 and the outer part 42. As described above, the inner apex 46 and the outer apex 50 are formed integrally at the radially inner portion of the bead 12. In this tire 2, the carcass ply 52 is not folded around the bead 12 unlike the conventional tire. Such a structure of the carcass 14 in the part of the bead 12 is also called an insert structure. In other words, the bead 12 of the tire 2 has an “insert structure”.

  The belt 16 is located radially inside the tread 4. The belt 16 is laminated with the carcass 14. The belt 16 reinforces the carcass 14. The belt 16 includes an inner layer 54 and an outer layer 56. In the tire 2, the width of the inner layer 54 is slightly larger than the width of the outer layer 56 in the axial direction. Although not shown, each of the inner layer 54 and the outer layer 56 is composed of a number of cords arranged in parallel and a topping rubber. Each code is inclined with respect to the equatorial plane. A typical absolute value of the tilt angle is 10 ° or more and 35 ° or less. The inclination direction of the cord of the inner layer 54 with respect to the equatorial plane is opposite to the inclination direction of the cord of the outer layer 56 with respect to the equatorial plane. The preferred material of the cord is steel. Organic fibers may be used for the cord. Preferred organic fibers include polyethylene terephthalate fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber and aramid fiber. The axial width of the belt 16 is preferably at least 0.7 times the maximum width of the tire 2. The belt 16 may include three or more layers.

  Each edge band 18 is located radially outside the belt 16 and near the end of the belt 16. Although not shown, the edge band 18 is made of a cord and a topping rubber. The cord is spirally wound. This band 20 has a so-called jointless structure. The cord extends substantially circumferentially. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. Since the end of the belt 16 is restrained by this cord, lifting of the belt 16 is suppressed. The cord is made of organic fibers. Preferred organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

  The band 20 is located radially outside the belt 16. In the axial direction, the width of the band 20 is larger than the width of the belt 16. Although not shown, the band 20 is made of a cord and a topping rubber. The cord is spirally wound. This band 20 has a so-called jointless structure. The cord extends substantially circumferentially. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. Since the belt 16 is restrained by this cord, lifting of the belt 16 is suppressed. The 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 the band 20 having high rigidity can be obtained, an aramid fiber is more preferable as the organic fiber for this cord.

  Each cushion layer 22 is laminated with the carcass 14 near the end of the belt 16. The cushion layer 22 is made of a soft crosslinked rubber. The cushion layer 22 absorbs stress at the end of the belt 16. The cushion layer 22 contributes to suppressing lifting of the belt 16.

  The inner liner 24 is located inside the carcass 14. The inner liner 24 is joined to the inner surface of the carcass 14 near the equatorial plane. 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 holds the internal pressure of the tire 2.

  Each insulation 26 is located inside the sidewall 8 in the axial direction. One insulation 26 a (first insulation) is sandwiched between the load support layer 30 (hereinafter simply referred to as a support layer) and the inner liner 24. The other insulation 26b (second insulation) is sandwiched between the inner liner 24 and the portion of the carcass 14 and the second bead 12b that includes the inner apex 46. The insulation 26 is made of a crosslinked rubber having excellent adhesiveness. The first insulation 26 a is firmly joined to the support layer 30 and also firmly to the inner liner 24. The second insulation 26 b is firmly joined to the carcass 14 and the inner apex 46, and is firmly joined to the inner liner 24. The insulation 26 suppresses the peeling of the inner liner 24 on the inner side in the axial direction of the sidewall 8.

  One chafer 28a (first chafer) of the pair of chafers 28 is located near the first bead 12a. The other chafer 28b (second chafer) is located near the second bead 12b. When the tire 2 is mounted on the rim, each chafer 28 abuts the rim. By this contact, the vicinity of each bead 12 is protected. In this embodiment, chafer 28 is integral with clinch 10. Therefore, the material of the chafer 28 is the same as the material of the clinch 10. The chafer 28 may be made of a cloth and rubber impregnated in the cloth.

  The support layer 30 is located axially inward of the first sidewall 8a. This support layer 30 is located axially inward of the carcass 14. The support layer 30 is sandwiched between the carcass 14 and the inner liner 24 (specifically, the first insulation 26a). The support layer 30 is located radially outward of the inner apex 46 in the first bead 12a. In the tire 2, the support layer 30 is laminated on the inner apex 46.

  In this tire 2, the support layer 30 is tapered inward and outward in the radial direction. This support layer 30 has a shape similar to a crescent moon. The thickness of the support layer 30 is measured, for example, along the normal to the inner surface of the support layer in the cross section shown in FIG. In the tire 2, the support layer 30 has a maximum thickness t1 at a position indicated by reference numeral PQ1 on the inner surface of the support layer 30.

  The support layer 30 is made of a high-hardness crosslinked rubber. When the tire 2 is punctured, the support layer 30 supports the load. Due to this support layer 30, the tire 2 can travel a certain distance even in a punctured state. The tire 2 is also called a run flat tire. The tire 2 is a side reinforcement type.

  In the tire 2, the hardness of the support layer 30 is preferably 60 or more and 85 or less. By setting the hardness to 60 or more, when the internal pressure of the tire 2 decreases due to puncture, the support layer 30 can effectively contribute to supporting the vehicle weight. In this respect, the hardness is more preferably equal to or greater than 65. By setting the hardness to 85 or less, the influence of the support layer 30 on the deflection of the first sidewall 8a is suppressed. In the tire 2, the riding comfort is appropriately maintained. In this respect, the hardness is more preferably equal to or less than 80.

  In the present application, the hardness is JIS-A hardness. This hardness is measured by a type A durometer at 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 FIG.

  In the tire 2, a portion from the first sidewall 8a to the first bead 12a (hereinafter, a first side portion 58a) includes a first rim protector 60a. The first rim protector 60a protrudes outward in the axial direction. The first rim protector 60a extends in the circumferential direction. The first rim protector 60a prevents the rim flange on which the tire 2 is mounted from being damaged. In the tire 2, the first rim protector 60a includes a first sidewall 8a and a first clinch 10a.

  In the tire 2, a portion from the second sidewall 8b to the second bead 12b (hereinafter, the second side portion 58b) includes the second rim protector 60b. The second rim protector 60b protrudes outward in the axial direction. The second rim protector 60b extends in the circumferential direction. The second rim protector 60b prevents the rim flange on which the tire 2 is mounted from being damaged. In the tire 2, the second rim protector 60b includes a second sidewall 8b and a second clinch 10b.

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

  In the method of manufacturing the tire 2, a number of elements including the inner liner 24 are combined on the outer surface of the core to obtain a raw cover (unvulcanized tire 2). In this manufacturing method, the raw cover is assembled on the outer surface of the core.

  In this manufacturing method, the raw cover is put into a mold (not shown) together with the core. After loading, the mold is closed. The inner surface of the raw cover is in contact with the core. The outer surface of the raw cover abuts 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 pressed 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. As described above, the method of manufacturing the tire 2 using the core is also referred to as a core method. By using a mold having an uneven pattern on the cavity surface, an uneven pattern is formed on the tire 2. The cavity surface forms the outer surface of the tire 2.

  FIG. 4 shows a use state of the tire 2. As shown in FIG. 4, the tire 2 is mounted on the rim 64.

  As the rim 64 to which the tire 2 is attached, for example, a split rim is used. The rim 64 has a pair of half rims 66. One half rim 66a (first half rim) of the pair of half rims 66 includes a first sheet 68a and a first flange 70a. The other half rim 66b (second half rim) includes a second sheet 68b and a second flange 70b. The rim 64 includes a first sheet 68a, a second sheet 68b, a first flange 70a, and a second flange 70b. The first bead 12a (first bead portion 72a) is fitted into the first sheet 68a. The first bead portion 72a contacts the first flange 70a. A portion of the second bead 12b (hereinafter, a second bead portion 72b) is fitted to the second sheet 68b. The second bead portion 72b contacts the second flange 70b.

  In this tire 2, the first side portion 58a has a length smaller than the length of the second side portion 58b. Therefore, when the rim diameter of the rim 64 of the first sheet 68a is the first rim diameter and the rim diameter of the rim 64 of the second sheet 68b is the second rim diameter, the first rim diameter is larger than the second rim diameter. Is also big. In the tire 2, the side where the first side portion 58a is located is the large diameter side, and the side where the second side portion 58b is located is the small diameter side. Therefore, in the tire 2, the nominal diameter of the rim diameter on the large diameter side (namely, the nominal diameter D1 of the first rim) is larger than the nominal diameter of the rim diameter on the minor diameter side (namely, the nominal diameter D2 of the second rim diameter). In the present invention, the "nominal of the rim diameter" is synonymous with the "nominal of the rim diameter" included in the "nominal of the tire" in the JATMA standard.

  In the present invention, the shape of the rim 64 on which the tire 2 is mounted is unique compared to the shape of a normal rim having the same left and right rim diameters (hereinafter, a normal rim). This rim 64 is special. For the tire 2 of the present invention, for example, two regular rims of a split type having different rim diameters are prepared, and the rim 64 is formed by combining a half rim of one regular rim and a half rim of the other regular rim. Can be configured. Since the rim 64 thus configured is configured by combining two normal rims, in the present invention, the rim according to the normal rim is also referred to as a quasi-normal rim. Further, in this specification, the normal rim means a rim defined in a standard on which the tire depends. The “standard rim” in the JATMA standard, the “Design Rim” in the TRA standard, and the “Measuring Rim” in the ETRTO standard are regular rims.

  As described above, in the tire 2, the nominal diameter D1 of the first rim diameter is larger than the nominal diameter D2 of the second rim diameter. In other words, in the tire 2, the first side portion 58a is shorter than the second side portion 58b in the radial direction.

  As shown in FIG. 1, in the tire 2, the support layer 30 is located on the inner side in the axial direction of the carcass 14 on the side of the first sidewall 8. In other words, the first side portion 58a includes the support layer 30. As described above, the first side portion 58a is shorter than the second side portion 58b. That is, the support layer 30 is provided on the short first side portion 58a. Moreover, the inside portion of the carcass 14 on the side of the first sidewall 8a is thicker than the inside portion of the carcass 14 on the side of the second sidewall 8b. The first side portion 58a is short and thick. This support layer 30 contributes to bending rigidity. In the tire 2, the deformation of the first side portion 58a is suppressed. Since the small deformation suppresses heat generation, the first side portion 58a is hardly damaged. The first side portion 58a contributes to run flat durability.

  As is apparent from FIG. 1, in the tire 2, the support layer 30 is not provided on the inner side of the carcass 14 in the axial direction on the side of the second sidewall 8b. On the other hand, on the side of the first sidewall 8a, the support layer 30 is provided inside the carcass 14 in the axial direction. In the tire 2, the inner portion of the carcass 14 on the side of the second sidewall 8b is thinner than the inner portion of the carcass 14 on the side of the first sidewall 8a. Moreover, the second side portion 58b is longer than the first side portion 58a. The second side portion 58b is thin and long. The second side portion 58b is easily bent. The second side portion 58b contributes to riding comfort.

  In FIG. 1, a double-headed arrow TP1 indicates the thickness of the inner portion of the carcass 14 at a first reference point P1 described later. The double arrow TP2 is the thickness of the inner portion of the carcass 14 at a second reference point P2 described later. Each of the thicknesses TP1 and TP2 is represented by an axial length from the carcass 14 to the inner surface of the tire 2.

  As described above, in the tire 2, the support layer 30 is not provided on the side of the second sidewall. In the tire 2, the ratio of the thickness TP2 to the thickness TP1 is about 0.2.

  In this tire 2, the first side portion 58a contributes to run flat durability, and the second side portion 58b contributes to ride comfort. In the tire 2, an improvement in ride comfort is achieved without impairing run-flat durability.

  In the tire 2 mounted on a vehicle (four-wheeled vehicle), a portion located inside the vehicle (hereinafter, the back side of the tire 2) radiates heat more than a portion located outside (the front side of the tire 2). Hateful. For this reason, the rear side of the tire 2 is more easily damaged than the front side. In particular, the back side of the tire 2 is easily damaged in running in a punctured state, that is, in run flat running.

  As described above, in the tire 2, the first side portion 58a contributes to run flat durability, and the second side portion 58b contributes to ride comfort. Therefore, by mounting the tire 2 on the vehicle such that the first side portion 58a is located inside the vehicle, the effect of the tire 2 is sufficiently exhibited. From this viewpoint, the first side portion 58a is located inside the vehicle (also referred to as the NS side), and the second side portion 58b is located outside the vehicle (also referred to as the S side). The tire 2 is preferably mounted on a vehicle.

  In FIG. 1, a two-dot chain line L1 is a contour of a virtual outer surface of the first side portion 58a obtained assuming that there is no first rim protector 60a. Usually, this contour L1 is represented by at least one arc. Reference symbol P1S in FIG. 1 is a radially outer edge of the first rim protector 60a. The two-dot chain line L1 is in contact with a line representing the contour of the outer surface of the first protector 60a at the outer edge P1S. 1 is the radial inner edge of the first rim protector 60a. The two-dot chain line L1 is in contact with another line representing the contour of the outer surface of the first protector 60a at the inner edge P1U.

  In FIG. 1, the two-dot chain line L2 is the contour of the virtual outer surface of the second side portion 58b obtained assuming that there is no second rim protector 60b. Usually, the contour L2 is represented by at least one arc. Reference symbol P2S in FIG. 1 is a radially outer edge of the second rim protector 60b. The two-dot chain line L2 is in contact with a line representing the contour of the outer surface of the second protector 60b at the outer edge P2S. Reference symbol P2U in FIG. 1 is the radial inner edge of the second rim protector 60b. The two-dot chain line L2 is in contact with another line representing the contour of the outer surface of the second protector 60b at the inner edge P2U.

  In this tire 2, the maximum width in the axial direction, that is, the so-called cross-sectional width, is not a net outer surface including the first rim protector 60a and the second rim protector 60b, but a portion of the first rim protector 60a by a contour L1, It is obtained based on the virtual outer surface in which the portion of the two-limb protector 60b is represented by the contour L2.

  In FIG. 1, reference numeral P1 is one axially outer end of the virtual outer surface. The outer end P1 is an axially outer end of the tire 2 on the side of the first sidewall 8a. In the present invention, the outer end P1 is referred to as a first reference point. In FIG. 1, reference numeral P2 is the other axially outer end of the virtual outer surface. The outer end P2 is an axially outer end of the tire 2 on the side of the second sidewall 8b. In the present invention, the outer end P2 is referred to as a second reference point.

  The axial length WM from the first reference point P1 to the second reference point P2 is the cross-sectional width of the tire 2. In FIG. 1, PH is a position on the outer surface of the tire 2 corresponding to a half position of the cross-sectional width WM, in other words, a position corresponding to the center of the tire 2 in the axial direction. This position PH is the axial center of the tire 2 in the cross section shown in FIG.

  The outer surface of the tire 2 shown in FIG. 1 corresponds to the cavity surface of the mold. Therefore, the axial width WM, the first reference point P1, the second reference point P2, and the position PH in FIG. 1 are determined based on the contour of the cavity surface of the mold.

  After the tire 2 is mounted on the rim 64, the inside of the tire 2 is filled with air. Thereby, the internal pressure of the tire 2 is adjusted. The tire 2 expands when the inside is filled with air. Thereby, the tire 2 is deformed. For this reason, the profile of the tire 2 whose internal pressure has been adjusted is different from the profile of the tire 2 represented by the cavity surface of the mold.

  In FIG. 4, the outline of the tire 2 whose internal pressure has been adjusted (hereinafter, the outline after adjustment) is indicated by a solid line. The contour after the adjustment is confirmed in the tire 2 in which the tire 2 is incorporated into the semi-regular rim and the internal pressure is adjusted to 180 kPa. The dotted line is a contour represented by the cavity surface of the mold (hereinafter, contour before adjustment). The outline represented by the dotted line corresponds to the outer surface of the tire 2 in the cross section of the tire 2 shown in FIG.

  As described above, the carcass 14 of the tire 2 includes a large number of cords. In the side portion 58 of the tire 2, these cords extend substantially in the radial direction. When the tire 2 is inflated, tension is applied to each cord. In the inflated tire 2, the tension acting on these cords is uniform.

  As described above, in the tire 2, the first side portion 58a includes the support layer 30. Although the first side portion 58a is shorter than the second side portion 58b, the rigidity of the first side portion 58a is higher than the rigidity of the second side portion 58b. For this reason, as shown in FIG. 4, the tire 2 expands so that its large diameter side is pulled toward the small diameter side. The center PH of the tire 2 in the contour before adjustment shifts to the side of the second side portion 58b. The first side portion 58a rises and has a form substantially along the radial direction. The first side portion 58a contributes to the longitudinal rigidity of the tire 2. A large longitudinal rigidity may affect the riding comfort of the tire 2. In running in a punctured state, that is, in run-flat running, the strain acting on the support layer 30 may lack uniformity. Non-uniform distortion affects the durability in run-flat running, that is, the run-flat durability.

  In this tire 2, as shown in FIG. 1, the equator PE of the tire 2 is located between the center PH of the tire 2 and the second end PT2 of the tread 4 in the axial direction. As described above, the contour of the outer surface of the tire 2 in the cross section of the tire 2 shown in FIG. 1 corresponds to the cavity surface of the mold. In the tire 2, the cavity surface of the mold has an axial length from the equator PE to the first reference point P1 (a double-pointed arrow W1 in FIG. 1) that is an axial length from the equator PE to the second reference point P2. It is designed to be larger than the height (double arrow W2 in FIG. 1). In other words, in this tire 2, the axial width of the portion of the tread 4 from the equatorial plane on the first end PT1 side is larger than the axial width of the portion on the second end PT2 side of the tread 4 from the equatorial plane. It is comprised so that it may have. This configuration effectively suppresses the influence of the first side portion 58a on the vertical rigidity due to the shift of the center PH described above. With this tire 2, good riding comfort is maintained. In the run flat running, since the strain is suppressed from acting unevenly on the support layer 30, the tire 2 maintains good run flat durability. In the tire 2, run-flat durability and ride comfort can be further improved. From this viewpoint, in the tire 2, as shown in FIG. 1, the equator PE is preferably located between the center PH and the second end PT2 in the axial direction. Further, the difference between the length W1 and the length WH is preferably 5 mm or more, and this difference is preferably 15 mm or less. The difference is more preferably 7 mm or more, and more preferably 13 mm or less. Note that the width WM in FIG. 1 is in a relation equal to the sum of the length W1 and the length W2. The length WH is the axial length from the center PH to the first reference point P1, and has a relationship equal to half the width WM.

  As described above, in the tire 2, the inner portion of the carcass 14 on the side of the second sidewall 8b is thinner than the inner portion of the carcass 14 on the side of the first sidewall 8a. Therefore, in the tire 2, the support layer 30 needs to appropriately contribute to the rigidity in order to support the vehicle weight during run flat running.

  In FIG. 2, the double-headed arrow e1 indicates the thickness of the outer portion of the carcass 14 at the position PQ1 where the support layer 30 has the maximum thickness t1. The thickness e1 is obtained by measuring the length from the carcass 14 to the virtual outer surface of the first side portion 58a along the normal of the inner surface for measuring the maximum thickness t1. The thickness e1 does not include the thickness of the first rim protector 60a.

  In the tire 2, the ratio of the maximum thickness t1 to the thickness e1 is preferably 3 or more, and more preferably 5 or less. When the ratio is set to 3 or more, the support layer 30 effectively contributes to the bending rigidity. The support layer 30 supports the vehicle weight during run-flat running. In the tire 2, by providing the support layer 30 only on the side of the first sidewall 8a, it is possible to travel a certain distance even in a punctured state. Moreover, since there is no need to provide the support layer 30 on the side of the second sidewall 8b as on the side of the first sidewall 8a, the tire 2 has a more comfortable ride than conventional tires having support layers on both sides. Excellent. In this respect, the ratio is more preferably equal to or greater than 3.0 and still more preferably equal to or greater than 3.5. By setting this ratio to 5 or less, the influence of the support layer 30 on the rigidity is suppressed. In the tire 2, the vertical rigidity is appropriately maintained. The tire 2 has excellent ride comfort. In this respect, the ratio is more preferably equal to or less than 5.0, and still more preferably equal to or less than 4.5.

  In the tire 2, the maximum thickness t1 of the support layer 30 is preferably 5 mm or more, and more preferably 11 mm or less. When the thickness t1 is set to 5 mm or more, the support layer 30 effectively contributes to the bending rigidity. The support layer 30 supports the vehicle weight during run-flat running. In the tire 2, by providing the support layer 30 only on the side of the first sidewall 8a, it is possible to travel a certain distance even in a punctured state. Moreover, since there is no need to provide the support layer 30 on the side of the second sidewall 8b as on the side of the first sidewall 8a, the tire 2 has a more comfortable ride than conventional tires having support layers on both sides. Excellent. In this respect, the thickness t1 is more preferably equal to or greater than 6 mm, and still more preferably equal to or greater than 7 mm. By setting the ratio to be equal to or less than 11 mm, the effect of the support layer 30 on the rigidity can be suppressed. In the tire 2, the vertical rigidity is appropriately maintained. The tire 2 has excellent ride comfort. In this respect, the ratio is more preferably equal to or less than 10 mm, and still more preferably equal to or less than 9 mm.

  In FIG. 3, the double arrow e2 indicates the thickness of the outer portion of the carcass 14 at the position PQ2. The thickness e2 is obtained by measuring the length from the carcass 14 to the virtual outer surface of the second side portion 58b along the normal to the outer surface of the carcass 14. The thickness e2 does not include the thickness of the second rim protector 60b.

  In the tire 2, the second sidewall 8b is preferably configured to have a thickness e2 equivalent to the thickness e1 of the first sidewall 8a. In other words, the ratio of the thickness e2 to the thickness e1 is preferably 0.9 or more, and more preferably 1.1 or less. Thereby, the influence of the second sidewall 8b on the rigidity is appropriately suppressed. With this tire 2, good riding comfort is maintained.

  The position PQ2 in FIG. 3 described above corresponds to the position PQ1 in FIG. Specifically, the position PQ2 is such that the ratio of the radial height HQ2 from the reference line SBL2 to the position PQ2 in FIG. 3 to the radial height HE2 from the reference line SBL2 to the equator PE in FIG. This is the position on the outer surface of the carcass where the ratio of the radial height HQ1 from the reference line SBL1 to the position PQ1 is equal to the radial height HE1 from the reference line SBL1 to the equator PE. The heights HQ1, HE1, HQ2 and HE2 are determined based on the contour of the cavity surface of the mold. The reference line SBL1 corresponds to a first baseline described later, and the reference line SBL2 corresponds to a second baseline described later.

  In FIG. 4, a solid line BL1 is a first baseline. The first base line is a line that defines the first rim diameter of the rim 64 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 baseline is a line that defines the second rim diameter of the rim 64. This second baseline extends in the axial direction.

  In FIG. 4, the double-headed arrow H1 indicates the position in the radial direction of the tire 2 from the first baseline to the maximum, that is, the radial height from the radial outer end. The height H1 is a cross-sectional height of the tire 2 obtained based on the first baseline. The double-headed arrow H2 indicates the radial height from the second baseline to the radially outer end. The height H2 is a cross-sectional height of the tire 2 obtained based on the second baseline.

  In FIG. 4, the double-headed arrow WMa represents the maximum width of the tire 2 in the axial direction. The width WMa is a cross-sectional width of the tire 2 in an inflated state. The sectional width WMa in FIG. 4 is obtained in the same manner as the sectional width WM shown in FIG. However, the sectional width WM of FIG. 1 is based on the outer surface represented by the cavity surface of the mold, and is different from the sectional width WMa of FIG.

  In the present invention, the sectional height H1, the sectional height H2, and the sectional width WMa are measured in a state where the tire 2 is mounted on the rim 64 and 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 a normal internal pressure defined in a standard on which the tire 2 depends, in consideration of the application and the size. Since the tire 2 shown in FIG. 1 is for a passenger car, the cross-section height H1, the cross-section height H2, and the cross-section width WMa are measured in a state where air is filled so that the internal pressure of the tire 2 becomes 180 kPa. . 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. I do.

  In this tire 2, the cross-sectional width WMa is preferably 195 mm or more, and more preferably 285 mm or less. By setting the cross-sectional width WMa to 195 mm or more, the tire 2 including the support layer 30 having an appropriate shape and size can be obtained. In this respect, the cross-sectional width WMa is more preferably equal to or greater than 200 mm. By setting the cross-sectional width WMa to 285 mm or less, the support layer 30 properly contributes to the rigidity of the tire 2. In the tire 2, good run flat durability is maintained. In this respect, the sectional width WMa is more preferably equal to or less than 280 mm.

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

  In the tire 2, the first aspect ratio F1 is preferably equal to or greater than 0.30, and more preferably equal to or less than 0.45. By setting the first aspect ratio F1 to 0.30 or more, the tire 2 including the support layer 30 having an appropriate shape and size can be obtained. In this respect, the first aspect ratio F1 is more preferably equal to or greater than 0.35. By setting the first aspect ratio F1 to 0.45 or less, the support layer 30 appropriately contributes to the rigidity of the tire 2. In the tire 2, good run flat durability is maintained. In this respect, the first aspect ratio F1 is more preferably equal to or less than 0.40.

  In the tire 2, the second aspect ratio F2 is preferably equal to or greater than 0.40, and more preferably equal to or less than 0.55. By setting the second aspect ratio F2 to 0.40 or more, the bending of the second side portion 58b is appropriately maintained. With this tire 2, good riding comfort is obtained. In this respect, the second aspect ratio F2 is more preferably equal to or greater than 0.45. By setting the second aspect ratio F2 to 0.55 or less, the influence of the second side portion 58b on the rigidity can be suppressed. Since the unevenness of the support layer 30 is prevented from acting unevenly in the first side portion 58a, good run flat durability is maintained. In this respect, the second aspect ratio F1 is more preferably equal to or less than 0.50.

  The tire 2 is of a different diameter bead type. Thereby, the rigidity of the tire 2 is controlled, and the run-flat durability and the riding comfort are improved. From the viewpoint that each of the first side portion 58a and the second side portion 58b effectively contributes to the rigidity and obtain good run-flat durability and ride comfort, the second rim having the nominal diameter D1 of the first rim diameter is used. The ratio of the diameter to the nominal diameter D2 is preferably 1.06 or more. From the viewpoint that the rigidity difference between the first side portion 58a and the second side portion 58b is appropriately maintained, the torsion of the tire 2 in the inflated state is suppressed, and the durability and wear resistance can be improved. This ratio is preferably 1.19 or less.

  As described above, the first side portion 58a of the tire 2 is shorter than the second side portion 58b. The short first side portion 58a contributes to bending rigidity. In the tire 2, good run flat durability is obtained. In this respect, the nominal D1 of the first rim diameter is preferably 18 inches or more. From the viewpoint that the support layer 30 having an appropriate shape and size is obtained, the nominal D1 of the first rim diameter is preferably 23 inches or less.

  As described above, the second side portion 58b of the tire 2 is longer than the first side portion 58a. The long second side portion 58b contributes to bending. Since the increase in the vertical rigidity is suppressed, the tire 2 provides a good ride quality. From the viewpoint of the formation of the long second side portion 58b, the nominal D2 of the second rim diameter is preferably 21 inches or less. From the viewpoint that the influence of the long second side portion 58b on the rigidity balance is suppressed, the nominal D2 of the second rim diameter is preferably 16 inches or more.

[Second embodiment]
5 and 6 show a pneumatic tire 74 according to another embodiment. FIG. 5 shows a right side portion of the cross section of the tire 74. FIG. 6 shows a left portion of the cross section of the tire 74. 5 and 6, the up-down direction is the radial direction of the tire 74, the left-right direction is the axial direction of the tire 74, and the direction perpendicular to the paper surface is the circumferential direction of the tire 74.

  The tire 74 includes a tread 76, a penetrating portion 78, a pair of sidewalls 80, a pair of clinch 82, a pair of beads 84, a carcass 86, a belt 88, a pair of edge bands 90, a band 92, a pair of cushion layers 94, A liner 96, a pair of insulations 98, a pair of chafers 100 and a pair of load support layers 102 are provided.

  In the tire 74, a load support layer 102b (hereinafter, a second support layer) is provided not only on the side of the first sidewall 80a but also on the side of the second sidewall 80b. Except for the second support layer 102b, the tire 2 has substantially the same configuration as that of the tire 2 shown in FIG.

  The second support layer 102b is located axially inward of the second sidewall 80b. The second support layer 102b is located axially inward of the carcass 86. The second support layer 102b is sandwiched between the carcass 86 and the inner liner 96 (specifically, the second insulation 98b). The second support layer 102b is located radially outside the inner apex 104 in the second bead 84b. In the tire 74, the second support layer 102b is laminated on the inner apex 104.

  In the tire 74, a radially inner portion of the second support layer 102b has a tapered shape. The radially outer portion of the second support layer 102b also has a tapered shape. The second support layer 102b may be configured to have a similar shape to a crescent moon, like the first load support layer 102a (hereinafter, first support layer).

  In this tire, the second support layer 102b is thinner than the first support layer 102a. In other words, the second support layer 102b has a thickness smaller than the thickness of the first support layer 102a. Specifically, the ratio of the maximum thickness of the second support layer 102b to the maximum thickness of the first support layer 102a is 0.9 or less.

  In the tire 74, the second support layer 102b is made of a crosslinked rubber. The second support layer 102b is made of a crosslinked rubber equivalent to the crosslinked rubber of the first support layer 102a. The second support layer 102b and the first support layer 102a are made of a crosslinked rubber equivalent to the crosslinked rubber of the support layer 30 of the tire 2 shown in FIG.

  In the tire 74, the first side portion 106a includes the dimple 108. Although not shown, in the tire 74, a large number of dimples 108 are provided in the first side portion 106a. These dimples 108 are arranged at intervals in the circumferential direction.

  In FIG. 5, the thin solid line L1 is the contour of the virtual outer surface of the first side portion 106a. This virtual outer surface represents the outline of the outer surface of the first side portion 106a, which is obtained assuming that there is no dimple 108. This virtual outer surface is synonymous with the virtual outer surface represented by the two-dot chain line L1 in FIG.

  In the tire 74, the second side portion 106b includes the rim protector 110. The rim protector 110 protrudes outward in the axial direction. The rim protector 110 extends in the circumferential direction. The rim protector 110 prevents the rim flange on which the tire 74 is mounted from being damaged. In the tire 74, the rim protector 110 includes the second sidewall 80b and the second clinch 82b.

  In FIG. 6, the two-dot chain line L2 is the contour of the virtual outer surface of the second side portion 106b. This virtual outer surface represents the contour of the outer surface of the second side portion 106b obtained assuming that the rim protector 110 is not provided. Reference symbol P2S in FIG. 6 is a radially outer edge of the rim protector 110. The two-dot chain line L2 is in contact with a line representing the contour of the outer surface of the rim protector 110 at the outer edge P2S. Reference symbol P2U in FIG. 6 is the radial inner edge of the rim protector 110. The two-dot chain line L2 is in contact with another line representing the contour of the outer surface of the rim protector 110 at the inner edge P2U. This virtual outer surface is synonymous with the virtual outer surface represented by a two-dot chain line L2 in FIG.

  In this tire 74, the nominal of the first rim diameter is larger than the nominal of the second rim diameter. As with the tire 2 shown in FIG. 1, in the tire 74, the first side portion 106a is shorter than the second side portion 106b.

  In the tire 74, the first support layer 102a is located on the inner side of the carcass 86 in the axial direction on the side of the first sidewall 80a. As described above, the first side portion 106a is shorter than the second side portion 106b. That is, the first support layer 102a is provided on the short first side portion 106a. In addition, since the first support layer 102a is thicker than the second support layer 102b, the carcass 86 on the first side wall 80a side despite the second support layer 102b being provided on the second side portion 106b. Is thicker than the inside portion of the carcass 86 on the side of the second sidewall 80b. The first side portion 106a is short and thick. The first support layer 102a contributes to bending rigidity. In the tire 74, the deformation of the first side portion 106a is suppressed. Since the small deformation suppresses heat generation, the first side portion 106a is hardly damaged. The first side portion 106a contributes to run flat durability.

  In the tire 74, the rim protector 110 is not provided on the first side portion 106a. In the tire 74, the influence of the rim protector 110 on the mass is suppressed. In the tire 74, good rolling resistance is maintained.

  In the tire 74, on the side of the second sidewall 80b, the second support layer 102b is provided inside the carcass 86 in the axial direction. As described above, the second support layer 102b is thinner than the first support layer 102a. For this reason, in the tire 74, even though the second side portion 106b has the second support layer 102b, the inner portion of the carcass 86 on the side of the second sidewall 80b is on the side of the first sidewall 80a. Is thinner than the inner part of the carcass 86 at Moreover, the second side portion 106b is longer than the first side portion 106a. The second side portion 106b is thin and long. The second side portion 106b is easily bent. The second side portion 106b contributes to riding comfort.

  In this tire, no dimple 108 is provided on the second side portion 106b. In the tire 74, the rigidity of the second side portion 106b is appropriately maintained. In the tire 74, the influence of the second side portion 106b on the steering stability is suppressed.

  In the tire 74, similarly to the tire 2 shown in FIG. 1, the first side portion 106a contributes to run flat durability, and the second side portion 106b contributes to ride comfort. With the tire 74, the ride comfort is improved without impairing the run flat durability. Therefore, also in the tire 74, by mounting the tire 74 on the vehicle such that the first side portion 106a is located inside the vehicle, the effect of the tire 74 is sufficiently exhibited. From this viewpoint, the first side portion 106a is located inside the vehicle (also referred to as the NS side), and the second side portion 106b is located outside the vehicle (also referred to as the S side). The tire 74 is preferably mounted on a vehicle.

  In FIG. 5, reference numeral P1 is one axially outer end of the virtual outer surface. The outer end P1 is an axially outer end on the side of the first sidewall 80a of the tire 74. In the present invention, the outer end P1 is referred to as a first reference point. This first reference point P1 is synonymous with the first reference point P1 in the tire 2 shown in FIG. The double arrow TP1 is the thickness of the inside portion of the carcass 86 at the first reference point P1. The thickness TP1 is represented by an axial length from the carcass 86 to the inner surface of the tire 74. In FIG. 6, reference numeral P2 is the other axially outer end of the virtual outer surface. The outer end P2 is an axially outer end of the tire 74 on the side of the second sidewall 80b. In the present invention, the outer end P2 is referred to as a second reference point. This second reference point P2 is synonymous with the second reference point P2 in the tire 2 shown in FIG. The double-headed arrow TP2 is the thickness of the inside portion of the carcass 86 at the second reference point P2. The thicknesses TP1 and TP2 are each represented by an axial length from the carcass 86 to the inner surface of the tire 74.

  In the tire 74, the ratio of the thickness TP2 to the thickness TP1 is preferably 0.9 or less. Thereby, the second side portion 106b contributes to riding comfort. In this respect, the ratio is more preferably equal to or less than 0.8, and further preferably equal to or less than 0.7. Particularly preferably, the support layer 102 is not provided on the side of the second sidewall 80b as in the tire 2 shown in FIG.

  Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be construed as being limited based on the description of the examples.

[Example 1]
The tire shown in FIGS. 1-3 was manufactured. The cross-sectional width WMa of this tire is 245 mm, the first aspect ratio F1 is 0.35, and the second aspect ratio F2 is 0.45. The first rim diameter nominal D1 is 20 inches and the second rim diameter nominal D2 is 18 inches. Therefore, the ratio (D1 / D2) of the nominal diameter D1 of the first rim diameter to the nominal diameter D2 of the second rim diameter was 1.11.

  In the first embodiment, a support layer having a thickness t1 of 8 mm is provided on the side of the first sidewall. Since the thickness e1 of the first sidewall is 2 mm, the ratio of the thickness t1 to the thickness e1 is 4.0. No support layer is provided on the side of the second sidewall. The thickness e2 of the second sidewall is 2 mm.

  The cavity surface of the mold for the tire of Example 1 has an axial length W1 from the first reference point to the equator of 125 mm and an axial length W2 from the second reference point to the equator of 125 mm. Is configured. Therefore, the difference between this length W1 and the axial length (WM / 2) from the first reference point to the center of the tire was 0 mm.

[Comparative Example 1]
Comparative Example 1 is a conventional run flat tire. The size of this tire is 245 / 40R19. Since the nominal rim diameter on both sides is the same, the ratio (D1 / D2) is 1.00. Load support layers were provided on both sides, and the thickness of each support layer was 8 mm. The thickness of the sidewalls on both sides was 2 mm. Therefore, the ratio (t1 / e1) is 4.0.

  The cavity surface of the mold for Comparative Example 1 has an axial length W1 from the first reference point to the equator of 125 mm, and the cavity surface of the mold from the second reference point to the equator similarly to the mold for the tire of Example 1. The axial length W2 is configured to be 125 mm. Therefore, the difference (W1-WM / 2) between this length W1 and the axial length (WM / 2) from the first reference point to the center of the tire was 0 mm.

[Comparative Example 2]
A tire of Comparative Example 1 was obtained in the same manner as in Example 1 except that a support layer was also provided on the side of the second sidewall. The thickness t2 of the support layer on the side of the second sidewall was 8 mm.

[Examples 2 and 3]
The first aspect ratio F1 and the second aspect ratio F2 are as shown in Table 1 below, and the ratio (D1 / D2) is changed by changing the nominal D1 of the first rim diameter and the nominal D2 of the second rim diameter. The tires of Examples 2 and 3 were obtained in the same manner as in Example 1 except that the tires were set to 1.

[Example 4]
The first aspect ratio F1 was as shown in Table 1 below, and the nominal (D1 / D2) of the first rim diameter was changed, and the ratio (D1 / D2) was changed as shown in Table 1 in the same manner as in Example 1. Thus, a tire of Example 4 was obtained.

[Example 5-10]
Tires of Examples 5 to 10 were obtained in the same manner as in Example 1 except that the thickness (t1) of the support layer was changed and the ratio (t1 / e1) was as shown in Table 2 below.

[Examples 11-16]
The tires of Examples 11 to 16 were obtained in the same manner as in Example 1 except that the width (W1) and the width (W2) were changed and the difference (W1-WM / 2) was as shown in Table 3 below.

[Example 17]
The tire shown in FIGS. 5-6 was manufactured. The cross-sectional width WMa of this tire is 245 mm, the first aspect ratio F1 is 0.35, and the second aspect ratio F2 is 0.45. The first rim diameter nominal D1 is 20 inches and the second rim diameter nominal D2 is 18 inches. Therefore, the ratio (D1 / D2) of the nominal diameter D1 of the first rim diameter to the nominal diameter D2 of the second rim diameter was 1.11.

  In Example 17, a support layer is provided on each of the first sidewall and the second sidewall. By adjusting the thickness of each support layer, the ratio (TP2 / TP1) of the thickness TP2 of the inner portion of the carcass at the second reference point to the thickness TP1 of the inner portion of the carcass at the first reference point is 0.1. 6 is set.

[Example 18-21 and Comparative Example 3]
Tires of Example 18-21 and Comparative Example 3 were obtained in the same manner as in Example 17 except that the thickness TP2 was adjusted and the ratio (TP2 / TP1) was as shown in Table 4 below. In Example 18, no support layer was provided on the side of the second sidewall.

[Ride comfort]
The tire was mounted on a rim, and the tire was filled with air so that the internal pressure became 230 kPa. The tire was mounted on a commercially available passenger car (displacement: 2000 cc). The tire was mounted such that the small diameter side of the tire was located outside (S side) in the width direction of the vehicle, and the large diameter side was located inside (NS side) in the width direction of the vehicle. For the rim, select the first half rim (made of aluminum alloy) with reference to the nominal D1 of the first rim diameter, and select the second half rim (made of aluminum alloy) with reference to the nominal D2 of the second rim diameter. A split rim (quasi-normal rim) constituted 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. The driver was allowed to drive this car on a racing circuit to evaluate ride comfort. No one except the driver is in the car. The results are shown in Tables 1-4 below, using an index with Comparative Example 1 being 100. The larger the value, the better.

[Run flat durability]
The tire was mounted on a rim, and the tire was filled with air to adjust the internal pressure to 180 kPa. The tire was mounted on a drum type running test machine, and a vertical load of 7.5 kN was applied to the tire. A punctured state was reproduced by using the internal pressure of the tire as normal pressure, and the tire was run on a drum having a radius of 1.7 m at a speed of 80 km / h. The running distance until the tire was broken was measured. The results are shown in Tables 1-4 below with index values with Comparative Example 1 being 100. The larger the value, the better. Note that the quasi-regular rim used in the evaluation of ride comfort was used as the rim.

[Overall performance]
The total value of the index value of the riding comfort and the index value of the run flat durability was calculated, and the result is shown in the following Table 1-4 as the overall performance. The larger the value, the better.

  As shown in Table 1-4, the tire of the example has a higher evaluation than the tire of the comparative example. From the evaluation results, the superiority of the present invention is clear.

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

2, 74 ... tire 4, 76 ... tread 8, 8a, 8b. 80, 80a, 80b ... sidewalls 10, 10a, 10b, 82, 82b ... clinch 12, 12a, 12b, 84, 84b ... beads 14, 86 ... carcass 30, 102, 102a, 102b ... Load support layer (support layer)
32 tread surface 34 groove 52 carcass ply 58a, 58b, 106a, 106b side part 60a, 60b rim protector 64 rim 68a, 68b sheet 72a , 72b: Bead part 108: Dimple 110: Rim protector

Claims (4)

Attached to the rim, a tread, a first sidewall, a second sidewall, a first bead, a second bead, a carcass, and a support layer,
The first sidewall extends substantially inward in the radial direction from a first end of the tread,
The first bead is located radially inward of the first sidewall,
The second sidewall extends radially inward from a second end of the tread,
The second bead is located radially inward of the second sidewall,
The carcass is stretched between the first bead and the second bead along the inside of the first sidewall, the tread and the second sidewall,
On the side of the first sidewall, the support layer is located inside the carcass in the axial direction,
The rim includes a first sheet and a second sheet, a portion of the first bead is fitted to the first sheet, a portion of the second bead is fitted to the second sheet, and the first sheet When the rim diameter of the rim is the first rim diameter and the rim diameter of the rim in the second seat is the second rim diameter, the nominal diameter of the first rim of the tire is the nominal diameter of the second rim. Greater than
The inner portion of the carcass on the side of the second side wall rather thin than the inner portion of the carcass on the side of the first side wall,
A pneumatic tire, wherein, in the axial direction, the equator of the tire is located between the center of the tire and the second end .   2. The pneumatic tire according to claim 1, wherein a ratio of the maximum thickness to a thickness of an outer portion of the carcass at a position where the support layer has a maximum thickness is 3 or more and 5 or less.   When the axially outer end of the tire on the side of the first sidewall is a first reference point, and the axially outer end of the tire on the side of the second sidewall is a second reference point, The pneumatic tire according to claim 1 or 2, wherein a ratio of a thickness of the inner portion of the carcass at the second reference point to a thickness of the inner portion of the carcass is 0.9 or less. The pneumatic tire according to claim 3 , wherein a difference between a length from the first reference point to the equator and a length from the first reference point to the center is 5 mm or more and 15 mm or less.

Images