Pneumatic tire

Abstract

To suppress radiation sound caused by vibration of a tread and to suppress deterioration of uniformity.SOLUTION: A pneumatic tire 2 includes: a tread 4 having a tread surface 22 that comes into contact with a road surface; a belt 14 located radially inside the tread 4; and an edge band 17 that covers an axial end of the belt 14. The belt 14 includes: a first belt ply 61 provided so as to pass through an equatorial plane C; and a second belt ply 62 located radially outside the first belt ply 61. The second belt ply 62 is provided such that an axial center 623 thereof is inclined to an axial first side. The edge band 17 is provided only on an axial second side and covers an axial second end 612 of the first belt ply 61.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] A pneumatic tire has a tread and a belt located radially inside the tread. Patent Document 1 discloses a pneumatic tire that aims to suppress radiated noise caused by vibration of the tread. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-159740 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of the pneumatic tire disclosed in Patent Document 1, the belt has a first belt ply that is long in the axial direction and a second belt ply that is short in the axial direction. The second belt ply is biased toward a first axial side (one axial side). The rigidity of the belt differs between the first axial side and the opposite second axial side, and the vibration mode of the tread differs between the first axial side and the second axial side. As a result, it is possible to suppress radiated noise due to tread vibration.

[0005] Since the second belt ply is biased toward the first side in the axial direction, the rigidity of the second side of the tread is reduced, which causes localized bulges on the tread surface and reduces the uniformity of the pneumatic tire. An object of the present invention is to provide a pneumatic tire that can suppress noise radiation due to vibration of the tread and also suppress deterioration of uniformity. [Means for solving the problem]

[0006] The pneumatic tire of the present invention comprises a tread having a tread surface that comes into contact with the road surface, a belt located radially inside the tread, and an edge band that covers the axial end of the belt, the belt having a first belt ply that passes through the equatorial plane and a second belt ply that is located radially outside the first belt ply, the second belt ply being arranged with its axial center biased toward the first axial side, and the edge band being arranged only on the second axial side and covering the end of the first belt ply on the second axial side. [Effects of the Invention]

[0007] According to the pneumatic tire of the present invention, it is possible to suppress radiated noise due to vibration of the tread, and also possible to suppress deterioration of uniformity. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a portion of a pneumatic tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory plan view of the tire shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Details of the embodiment of the present invention] The present invention will now be described based on preferred embodiments with reference to the drawings.

[0010] The pneumatic tire of the present invention (hereinafter also referred to simply as "tire") is mounted on a rim. Air is filled inside the tire, and the internal pressure of the tire is adjusted. A tire mounted on a rim is also called a tire-rim assembly. A tire-rim assembly has a rim and a tire mounted on the rim.

[0011] In the present invention, a state in which a tire is mounted on a normal rim, the internal pressure of the tire is adjusted to a normal internal pressure, and no load is applied to the tire is referred to as a normal state. In this disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the normal state.

[0012] In the meridian section of the tire, the dimensions and angles of each part that cannot be measured when the tire is mounted on a regular rim are measured on the cross section obtained by cutting the tire along a plane containing the rotation axis. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads on the tire mounted on a regular rim. The tire configuration that cannot be confirmed when the tire is mounted on a regular rim is confirmed on the cross section.

[0013] A genuine rim is a rim specified in the standard on which the tire is based. The "standard rim" included in the applicable rim in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are genuine rims.

[0014] Normal tire pressure refers to the pressure specified in the standard on which the tire is based. The "maximum tire pressure" in the JATMA standard, the "maximum tire pressure" listed in the TRA standard's "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0015] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0016] The tire has a tread portion, a pair of bead portions, and a pair of sidewall portions. The tread is the part of the tire that comes into contact with the road, the bead is the part that fits onto the rim, and the sidewall is the part that connects the tread and the bead.

[0017] FIG. 1 is a cross-sectional view showing a portion of a pneumatic tire 2 (hereinafter also simply referred to as "tire 2") according to one embodiment of the present invention. The tire 2 is a tire for a passenger car. In FIG. 1, the tire 2 is mounted on a rim R. The rim R is a regular rim. The inside of the tire 2 is filled with air, and the internal pressure of the tire 2 is adjusted.

[0018] FIG. 1 shows a portion of a cross section (also called a meridian cross section) of the tire 2 taken along a plane including the rotation axis of the tire 2. In FIG. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the plane of FIG. 1 is the circumferential direction of the tire 2. In FIG. 1, a dashed dotted line CL represents the equatorial plane of the tire 2. 1, with respect to the equatorial plane CL, the right side is defined as the “axial first side,” and the left side is defined as the “axial second side.” As will be described later, the tire 2 of this embodiment has an asymmetric shape with respect to the equatorial plane CL.

[0019] The solid line BBL extending in the axial direction is the bead base line, which defines the rim radius (see JATMA, etc.).

[0020] The symbol PW denotes the axial outer end of the tire 2. The outer end PW is determined based on the outline of the outer surface of the tire 2 in a normal state. If the outer surface has decorations such as patterns or letters, the outer end PW is determined based on the outline of a virtual outer surface obtained assuming that there is no decoration. The outer end PW is the position where the tire 2 has the widest width (hereinafter referred to as the widest position).

[0021] The symbol PC is the equator of the tire 2. The equator PC is the radially outer edge of the tire, and the radially outer edge is determined based on the outline of the outer surface of the tire 2 in a normal state. If there is a groove on the equatorial plane CL, the equator PC is determined based on the outline of a virtual outer surface obtained assuming that there is no groove.

[0022] The symbol PE indicates the ground contact edge. The ground contact edge PE is a position on the outer surface of the tread 4, and is the axially outer end of the contact patch of the tire 2 with the road surface. The ground contact edge PE is the axially outer end of the contact patch obtained by placing a load of 80% of the load index on a tire 2 mounted on a standard rim and with an internal pressure of 230 kPa, setting the camber angle to 0°, and bringing the tire 2 into contact with a flat road surface. The load index is specified, for example, in the JATMA standard, and is an index that represents the maximum mass that can be loaded on a tire under specified conditions, i.e., its maximum load capacity.

[0023] The tire 2 has a tread 4 , a pair of sidewalls 6 , a pair of clinches 8 , a pair of beads 10 , a carcass 12 , a belt 14 , an edge band 17 , a pair of chafers 18 , and an inner liner 20 .

[0024] The tread 4 has a tread surface 22 that comes into contact with the road surface. The tread 4 is located radially outward of the belt 14. The tread 4 is made of cross-linked rubber that takes into consideration wear resistance, grip performance, and the like. The tread 4 has a plurality of grooves 24 (four in the illustrated example) cut into the tread surface 22 along the circumferential direction. The grooves 24 are circumferential grooves that extend continuously in the circumferential direction and are arranged in parallel in the axial direction. Of the four grooves 24, the circumferential grooves located outermost on both sides in the axial direction are shoulder grooves 24s.

[0025] The tread 4 has, by the plurality of grooves 24, two shoulder land portions 26s located on both axially outer sides, and one or more center land portions 26c located between the two shoulder land portions 26s. In the embodiment shown in Fig. 1, five land portions 26 are provided on the tread 4, each defined by four grooves 24. Of the five land portions 26, the land portions 26 located outermost on both sides in the axial direction are shoulder land portions 26s. The remaining three land portions 26 are center land portions 26c.

[0026] The sidewalls 6 are continuous with the edges of the tread 4. The sidewalls 6 are located radially inward of the tread 4. The sidewalls 6 extend from the edges of the tread 4 along the carcass 12. The sidewalls 6 are made of crosslinked rubber in consideration of cut resistance. The clinch 8 is located radially inside the sidewall 6. The clinch 8 comes into contact with the rim R. The clinch 8 is made of crosslinked rubber in consideration of wear resistance.

[0027] The bead 10 is located axially inside the clinch 8. The bead 10 is located radially inside the sidewall 6. The bead 10 has a core 28, an inner apex 30, and an outer apex 32. The core 28 is ring-shaped. Although not shown, the core 28 includes a steel wire. The inner apex 30 and the outer apex 32 are made of cross-linked rubber with high rigidity.

[0028] The chafer 18 is located radially inside the bead 10. The chafer 18 contacts the rim R. The chafer 18 is made of a cloth and rubber impregnated into the cloth. The carcass 12 is located inside the tread 4, the pair of sidewalls 6, and the pair of clinches 8. The carcass 12 bridges between one bead 10 and the other bead 10. The carcass 12 has a radial structure.

[0029] The carcass 12 of this embodiment is made up of one carcass ply 34. The carcass ply 34 is folded back from the inside to the outside in the axial direction around the core 28. The carcass ply 34 has a ply body 36 that spans between one core 28 and the other core 28, and a pair of turn-up portions 38 that are continuous with the ply body 36 and are folded back from the inside to the outside in the axial direction around the core 28.

[0030] The carcass ply 34 includes a number of carcass cords arranged in parallel. Although not shown, each carcass cord intersects the equator plane. The carcass cords are made of organic fibers such as nylon fibers, rayon fibers, polyester fibers, and aramid fibers. The carcass cords are covered with a topping rubber, although not shown.

[0031] The inner liner 20 is located inside the carcass 12. The inner liner 20 constitutes the inner surface of the tire 2. The inner liner 20 is made of crosslinked rubber with a low gas permeability coefficient. The inner liner 20 maintains the internal pressure of the tire 2.

[0032] The belt 14 is located radially inside the tread 4 and radially outside the carcass 12. The belt 14 has at least two layers laminated in the radial direction. In the embodiment shown in FIG. 1, the belt 14 has two layers: a first belt ply 61 and a second belt ply 62. Of the two layers, the layer located radially inside is the first belt ply 61, and the layer located radially outside is the second belt ply 62. As shown in FIG. 1, the first belt ply 61 has a larger axial dimension (wider width) than the second belt ply 62.

[0033] The first belt ply 61 is disposed evenly on the first axial side and the second axial side. That is, the axial center of the first belt ply 61 is located on the equatorial plane CL. In contrast, the second belt ply 62 is disposed so as to pass through the equatorial plane CL, but its axial center 623 is disposed so as to be offset toward the first axial side. That is, the axial center 623 of the second belt ply 62 is not positioned on the equatorial plane CL, but is positioned in an area on the first axial side of the equatorial plane CL. This results in the tire 2 having an asymmetric shape with respect to the equatorial plane CL. Ends 611, 612 on both axial sides of the first belt ply 61 are positioned axially outward of ends 621, 622 on both axial sides of the second belt ply 62.

[0034] FIG. 2 is an explanatory plan view showing a part of a tread portion of the tire 2 shown in FIG. 1. The first belt ply 61 has a large number of first belt cords 615 arranged in parallel. These first belt cords 615 are covered with a topping rubber. The first belt cords 615 are inclined with respect to the equatorial plane CL. For ease of explanation, FIG. 2 shows only a part of the first belt ply 61 and other parts in the circumferential direction. The second belt ply 62 has a large number of parallel arranged second belt cords 625. The second belt cords 625 are covered with a topping rubber. The second belt cords 625 are inclined with respect to the equator plane CL. The first belt cord 615 and the second belt cord 625 are made of steel.

[0035] 1, the edge band 17 is located radially between the tread 4 and a part of the belt 14. The edge band 17 covers the axial end of the belt 14. In other words, the edge band 17 is laminated on the end of the belt 14.

[0036] An end 172 on the second axial side of the edge band 17 is located on the second axial side (axially outer side) of an end 612 on the second axial side of the first belt ply 61. An axial dimension J from the end 612 on the second axial side of the first belt ply 61 to the end 172 on the second axial side of the edge band 17 is, for example, not less than 3 mm and not more than 10 mm. The edge band 17 is provided only on the second axial side (left side in FIG. 1 ) and covers an end 612 on the second axial side of the first belt ply 61. The edge band 17 partially covers the end portions of the first belt ply 61, including the end 612. In this respect, too, the tire 2 has an asymmetric shape with respect to the equatorial plane CL.

[0037] The edge band 17 includes a spirally wound band cord 175 (see FIG. 2). The band cord 175 extends substantially in the circumferential direction. Specifically, the angle that the band cord 175 forms with the circumferential direction is 5° or less. The edge band 17 may have a jointless structure. The band cord 175 is covered with a topping rubber (not shown). In this embodiment, a cord made of organic fiber is used as the band cord 175. Examples of organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber.

[0038] Although not shown, the tire 2 may have a band located between the tread 4 and the belt 14. The band has a band cord covered with a topping rubber, and covers, for example, the entire belt 14. In this case, the edge band 17 covers the axial end of the belt 14, including the second axial end of the band.

[0039] [Specific configuration of tread portion] In this embodiment, the tread portion includes the tread 4, the belt 14, and the edge band 17. As described above, the belt 14 has the first belt ply 61 and the second belt ply 62 located radially outward of the first belt ply 61.

[0040] For example, as in a passenger car tire, the first and second belt plies 61 and 62, which are inclined belt layers, have belt cords 615 and 625, respectively. When the inclination angle of these belt cords 615 and 625 with respect to the circumferential direction is large, the first, second, and third vibration modes in the cross-sectional direction may become modes in which the tread surface 22 vibrates significantly in the high frequency range of 400 Hz to 2 kHz. This may result in a large radiated sound.

[0041] Therefore, as in this embodiment, the belt 14 has a first belt ply 61 with a large axial dimension and a second belt ply 62 with a small axial dimension. With this configuration, the axial center portion of the tread 4 is less likely to expand in the tire radial direction, suppressing the expansion of the tread surface 22 in the circumferential direction (vibration amplitude), and reducing radiated noise.

[0042] Furthermore, in this embodiment, as described above, the first belt ply 61 is evenly disposed on the first axial side and the second axial side. The second belt ply 62 has its axial center 623 biased toward the first axial side. With this configuration, the rigidity of the tread portion differs between the region on the first axial side and the region on the second axial side, and the vibration of the tread portion occurs in different modes. As a result, the peak level of the sound is reduced, and it is possible to more effectively suppress the radiated sound caused by the vibration of the tread portion.

[0043] When the tire 2 of this embodiment is mounted on a vehicle, the first axial side (the right side in FIG. 1) of the tire 2 is preferably on the inside in the vehicle mounting direction, that is, the vehicle inner side. In the vehicle, a lateral force is generated inward in the vehicle mounting direction from the pair of left and right tires 2. For this reason, by mounting the tires 2 on the vehicle as described above, steering stability (toe-in effect) when traveling straight is improved.

[0044] [Arrangement of the first belt ply 61 and the second belt ply 62] As shown in FIG. 1 , the axial dimension of the first belt ply 61 is W1. The axial dimension of the second belt ply 62 is W2. The axial dimension from an end 611 on the first axial side of the first belt ply 61 to an end 621 on the first axial side of the second belt ply 62 is S1. The axial dimension from an end 612 on the second axial side of the first belt ply 61 to an end 622 on the second axial side of the second belt ply 62 is S2. In this case, in the tire 2 of this embodiment, W1, W2, S1, and S2 have the following relationship.

[0045] W1>W2 W2 / W1 is 0.2 or more and 0.7 or less (0.2≦W2 / W1≦0.7 Formula 1) S2 / S1 is 2.0 or more and 8.0 or less (2.0≦S2 / S1≦8.0...Equation 2)

[0046] The axial dimension W1 of the first belt ply 61 is larger than the axial dimension W2 of the second belt ply 62 (W1>W2). However, if W1 is too larger than W2, the region of low rigidity in the tread portion becomes too wide, the amplitude of the vibration mode does not decrease, and the effect of suppressing radiated sound may decrease. For this reason, W2 / W1 is 0.2 or more. On the other hand, if W1 is as small as W2, sufficient separation of vibration modes may not be achieved, so W2 / W1 is 0.7 or less.

[0047] A region including only the first belt ply 61 where the first belt ply 61 and the second belt ply 62 do not overlap becomes a low-rigidity region of the tread portion. If the difference in axial dimensions (S1, S2) of such a low-rigidity region between the first axial side and the second axial side is too small, vibration modes may not be sufficiently separated, resulting in a reduced effect of reducing radiated sound. On the other hand, if the difference in the axial dimensions (S1, S2) of the low rigidity region between the first axial side and the second axial side is too large, large amplitude vibrations may occur in the first belt ply 61, which may reduce the noise reduction effect. Therefore, the ratio S2 / S1 regarding the axial dimension of the low rigidity region is 2.0 or more and 8.0 or less.

[0048] On the first axial side, the axial dimension S1 is, for example, not less than 3 mm and not more than 10 mm. On the second axial side, the axial dimension S2 is, for example, not less than 6 mm and not more than 80 mm.

[0049] The axial center position (center 623) of the second belt ply 62 does not coincide with the equator PC, but is shifted toward the first axial side. Specifically, the ratio (E / [F×½]) of the axial dimension E from the axial center position (center 623) to the equator PC to ½ of the axial dimension F of the tread 4 is 0.3 or more and 0.5 or less. The axial dimension F (see FIG. 1) is the axial dimension between the axially first grounding end PE and the axially second grounding end PE. Half of the axial dimension F corresponds to the axial dimension from the equator PC to the axially first grounding end PE (or the axially second grounding end PE).

[0050] [About Edge Band 17] As described above, the edge band 17 is provided only on the second axial side (the left side in FIG. 1) and covers the end 612 of the first belt ply 61 on the second axial side. The second belt ply 62 has an axial center 623 biased toward the first axial side, so that the shoulder region including the shoulder land portion 26s on the second axial side has lower rigidity than the first axial side. An edge band 17 having a circumferential cord is provided in the shoulder region on the second axial side, which has lower rigidity. This edge band 17 suppresses localized bulging of the tread surface 22 of the tire 2 due to centrifugal force. The roundness of the tire 2 is maintained, and deterioration of uniformity is suppressed.

[0051] By suppressing deterioration of the uniformity, the feeling of impact related to the ride comfort and the low-frequency vibration that is a cause of lateral force variation are suppressed. In other words, the ride comfort performance of a vehicle equipped with the tire 2 of this embodiment is improved. In addition, an increase in conicity is prevented, improving handling stability. Furthermore, the contact shape with the road surface is prevented from localized extension of the contact length on the axially outer side, suppressing local increases in contact pressure in the shoulder land portions 26s located on the axially outer side. This prevents uneven contact pressure distribution and suppresses uneven wear of the tire 2. Road input is absorbed across the entire tread surface 22, reducing the sound pressure of interior noise across the entire range, improving noise resistance.

[0052] The axial dimension X of the edge band 17 is equal to or greater than 0.1×S2 and equal to or less than 0.6×S2 (0.1×S2≦X≦0.6×S2). If the axial dimension X of the edge band 17 is too large, the rigidity of the tread portion on the axial second side increases, and the difference in rigidity between the axial first side and the axial second side of the tread portion decreases. This may result in a decrease in the dispersion of the vibration mode. Therefore, it is preferable that the axial dimension X is 0.6 × S2 or less.

[0053] On the other hand, if the axial dimension X of the edge band 17 is too small, the rigidity of the tread portion on the second axial side may decrease, which may reduce the effect of suppressing local bulging of the tread surface 22. Therefore, the axial dimension X is preferably 0.1 × S2 or more.

[0054] The arrangement of the edge band 17 and the shoulder groove 24s on the axial second side will be described. As shown in Fig. 1, the axial dimension of the shoulder land portion 26s on the axial second side is designated as "Z." The axial dimension Z is the axial dimension from the opening edge of the shoulder groove 24s to the axial second side ground contact edge PE. The distance between the axially inner end 171 of the edge band 17 and the shoulder groove 24s on the second axial side is defined as "Y." The distance Y is the axial dimension from the opening edge of the shoulder groove 24s to the end 171 of the edge band 17.

[0055] The ratio (Y / Z) of the distance Y to the axial dimension Z is equal to or greater than 0.2 and equal to or less than 0.6.

[0056] The edge band 17 appears to have a plurality of band cords 175 arranged side by side (see FIG. 2). The band cords 175 are cords made of organic fibers, such as nylon fibers or aramid fibers. It is preferable that the edge band 17 has a different shape depending on whether the band cord 175 is made of nylon fiber or aramid fiber. Even if the material of the band cord 175 is different, the first belt ply 61 has a larger axial dimension than the second belt ply 62 (W1>W2), and the above-described configurations are adopted.

[0057] First, a case where the band cord 175 is made of aramid fiber will be described. As shown in FIG. 1, the axial dimension from the end 612 on the second axial side of the first belt ply 61 to the end 622 on the second axial side of the second belt ply 62 is S2.

[0058] Aramid fiber has a relatively high tensile strength (compared to nylon fiber). Therefore, if the axial dimension X of the edge band 17 is too large, the rigidity of the second axial side of the tread portion increases, which may reduce the dispersion effect of the vibration mode. Therefore, when the edge band 17 contains aramid fiber as the band cord 175, the axial dimension X thereof is preferably 0.2×S2 or less.

[0059] However, if the axial dimension X of the edge band 17 is too small, the difference in rigidity between the axial outer and inner sides on the second axial side of the tread portion may become too large. This may weaken the ability of the edge band 17 to suppress localized bulging of the tread surface 22. Therefore, it is preferable that the axial dimension X of the edge band 17 be 0.1 × S2 or more.

[0060] In this way, when the band cord 175 is made of aramid fiber, the axial dimension X of the edge band 17 and the axial dimension S2 have the following relationship. 0.1×S2≦X≦0.2×S2 That is, the axial dimension X of the edge band 17 is equal to or greater than 0.1×S2 and equal to or less than 0.2×S2. When the band cord 175 is made of aramid fiber, the axial dimension X of the edge band 17 is smaller than the axial dimension S2, as compared to when the band cord 175 is made of nylon fiber (described later).

[0061] The relationship between the edge band 17 and the first and second belt ply 61 and 62 will be described. The tensile strength of a 50 mm width of one or both of the first belt ply 61 and the second belt ply 62 may be 28,000 N or more. In this case, if the tensile strength of the band cord 175 of the edge band 17 is low, the effect of the edge band 17 in suppressing local bulging of the tread surface 22 may be weakened.

[0062] Therefore, it is preferable that the band cord 175 of the edge band 17 is made of aramid fiber, which has a relatively high tensile strength. That is, when the tensile strength is 28000 N or more, the edge band 17 has band cords 175 containing aramid fiber arranged side by side. This makes it possible to improve tire uniformity, uneven wear, ride comfort, handling stability, and noise resistance.

[0063] In the present invention, the tensile strength of the first belt ply 61 (second belt ply 62) is expressed as the product of the strength at break of the belt cord 615 (625) and the cord density, that is, the product of the tensile strength of the belt cord 615 (625) and the ends. The strength at break of the belt cord is measured in accordance with the provisions of JIS L1017, and its unit is Newton (N). Note that "ends" refers to the number of belt cords present per 5 cm width in a cross section perpendicular to the extension direction of the belt cords of the belt ply.

[0064] Next, a case where the band cord 175 is made of nylon fiber will be described. As shown in FIG. 1, the axial dimension from the end 612 on the second axial side of the first belt ply 61 to the end 622 on the second axial side of the second belt ply 62 is S2.

[0065] Nylon fiber has a relatively low tensile strength (compared to aramid fiber), so if the axial dimension of the edge band 17 is too small, the effect of the edge band 17 in suppressing localized bulging of the tread surface 22 may be reduced. Therefore, when the edge band 17 includes nylon fibers as the band cord 175, the axial dimension X thereof is preferably 0.5×S2 or more.

[0066] However, if the axial dimension of the edge band 17 is too large, the rigidity of the axial second side of the tread portion increases, which may reduce the dispersion effect of the vibration mode. Therefore, the axial dimension X of the edge band 17 is preferably 0.6 × S2 or less.

[0067] In this way, when the band cord 175 is made of nylon fiber, the axial dimension X of the edge band 17 and the axial dimension S2 have the following relationship. 0.5×S2≦X≦0.6×S2 That is, the axial dimension X of the edge band 17 is equal to or greater than 0.5×S2 and equal to or less than 0.6×S2. When the band cord 175 is made of nylon fiber, the axial dimension X of the edge band 17 is larger than the axial dimension S2, compared to when the band cord 175 is made of aramid fiber.

[0068] The relationship between the edge band 17 and the first and second belt ply 61 and 62 will be described. The tensile strength of a 50 mm width of one or both of the first belt ply 61 and the second belt ply 62 may be 20,500 N or less. In this case, if the tensile strength of the band cord 175 of the edge band 17 is high, the effect of the edge band 17 in dispersing the vibration mode may be reduced.

[0069] Therefore, it is preferable that the band cord 175 of the edge band 17 is made of nylon fiber having a relatively low tensile strength. That is, when the tensile strength is 20,500 N or less, the edge band 17 has band cords 175 containing nylon fiber arranged side by side. This makes it possible to improve tire uniformity, uneven wear, ride comfort, handling stability, and noise resistance.

[0070] [Modification of tread portion] As a modification of the tread portion, the ratio (W2 / W1) of the axial dimension W1 of the first belt ply 61 to the axial dimension W2 of the second belt ply 62 may be different from the above-mentioned "Formula 1" (however, for the definitions of the axial dimensions W1 and W2, see Figure 1). That is, W1>W2 is the same as in the above embodiment that satisfies the above "Formula 1," but as a modified example of the tread portion (modified example 1), W1 and W2 have the following relationship.

[0071] W2 / W1 is less than 0.2 (W2 / W1<0.2). Or, W2 / W1 is greater than 0.7 (W2 / W1>0.7).

[0072] As another variation of the tread portion, the ratio (S2 / S1) of the axial dimension S2 to the axial dimension S1 may be different from the above-mentioned "Formula 2" (however, for the definitions of the axial dimensions S1 and S2, see Figure 1). That is, W1>W2 is the same as in the above embodiment that satisfies the above "Formula 2," but as a modified example of the tread portion (modified example 2), S1 and S2 have the following relationship.

[0073] S2 / S1 is less than 2.0 (S2 / S1<2.0). Or, S2 / S1 is greater than 8.0 (S2 / S1>8.0).

[0074] The tire 2 may have both the first and second variations in the configurations of W1, W2, S1, and S2.

[0075] [Regarding tire 2 of this embodiment] As described above, the belt 14 included in the tire 2 according to this embodiment includes the first belt ply 61 and the second belt ply 62. The first belt ply 61 is provided passing through the equatorial plane CL. The second belt ply 62 is located radially outward of the first belt ply 61. The second belt ply 62 is provided such that its axial center 623 is biased toward the first axial side.

[0076] This configuration causes the tread portion to vibrate in different modes between the first axial region and the second axial region, lowering the peak sound level and making it possible to more effectively suppress sound radiation due to vibration of the tread portion. In the present embodiment, as described above, the axial center 623 of the second belt ply 62 is biased toward the first axial side, and therefore the shoulder region including the shoulder land portion 26s on the second axial side has lower rigidity than the first axial side.

[0077] Therefore, the edge band 17 is provided only on the second axial side, covering the end 612 on the second axial side of the first belt ply 61. In other words, the edge band 17 is provided in the shoulder region on the second axial side, which has low rigidity. The edge band 17 suppresses localized bulging of the tread surface 22 of the tire 2 due to centrifugal force. The roundness of the tire 2 is maintained, and deterioration of uniformity is suppressed.

[0078] As described above, according to the present invention, a pneumatic tire 2 can be obtained that can suppress radiation noise due to vibration of the tread 4 and also suppress deterioration of uniformity. [Industrial Applicability]

[0079] The above-described technology that enables the performance of the tire 2 to be improved can be applied to various tires.

[0080] [Note] The present invention includes the following aspects. (1) Pneumatic tires are a tread having a tread surface that comes into contact with a road surface; a belt located radially inside the tread; an edge band covering an axial end of the belt; and The belt has a first belt ply provided passing through an equator plane and a second belt ply located radially outward of the first belt ply, the second belt ply is provided such that its axial center is offset toward the first axial side, The edge band is provided only on the second axial side and covers the end of the first belt ply on the second axial side.

[0081] (2) The axial dimension of the first belt ply is W1, The axial dimension of the second belt ply is W2, an axial dimension S1 from an end of the first belt ply on the first side in the axial direction to an end of the second belt ply on the first side in the axial direction, When the axial dimension from the end of the first belt ply on the second side in the axial direction to the end of the second belt ply on the second side in the axial direction is S2, W1>W2 W2 / W1 is 0.2 or more and 0.7 or less S2 / S1 is 2.0 or more and 8.0 or less The pneumatic tire of (1) above.

[0082] (3) The pneumatic tire according to (1) or (2), wherein the axial dimension of the edge band is 0.1×S2 or more and 0.6×S2 or less.

[0083] (4) The edge band has a band cord containing aramid fiber, the first belt ply has an axial dimension larger than that of the second belt ply, When the axial dimension from the end of the first belt ply on the second side in the axial direction to the end of the second belt ply on the second side in the axial direction is S2, The pneumatic tire according to any one of (1) to (3), wherein the axial dimension of the edge band is 0.1×S2 or more and 0.2×S2 or less.

[0084] (5) The edge band has a band cord containing nylon fibers, the first belt ply has an axial dimension larger than that of the second belt ply, When the axial dimension from the end of the first belt ply on the second side in the axial direction to the end of the second belt ply on the second side in the axial direction is S2, The pneumatic tire according to any one of (1) to (3), wherein the axial dimension of the edge band is 0.5×S2 or more and 0.6×S2 or less.

[0085] (6) The tensile strength of one or both of the first belt ply and the second belt ply in a width of 50 mm is 28000 N or more, The pneumatic tire according to any one of (1) to (4), wherein the edge band has a band cord containing aramid fiber.

[0086] (7) The tensile strength of one or both of the first belt ply and the second belt ply in a width of 50 mm is 20,500 N or less, The pneumatic tire according to any one of (1) to (3) or (5), wherein the edge band has a band cord containing nylon fiber.

[0087] (8) A pneumatic tire according to any one of (1) to (7), wherein the first axial side is on the inside in the vehicle mounting direction.

[0088] (9) The tread has two shoulder land portions located on both axially outer sides and one or more center land portions located between the two shoulder land portions by forming a plurality of grooves on the tread surface along the circumferential direction, The pneumatic tire according to any one of (1) to (8), wherein the ratio of the distance between the axially inner end of the edge band and the shoulder groove on the axial second side to the axial dimension of the shoulder land portion on the axial second side is 0.2 or more and 0.6 or less.

[0089] (10) The axial dimension of the first belt ply is W1, When the axial dimension of the second belt ply is W2, W1>W2 The pneumatic tire according to (1), wherein W2 / W1 is less than 0.2 or greater than 0.7.

[0090] (11) The first belt ply has a larger axial dimension than the second belt ply, an axial dimension S1 from an end of the first belt ply on the first side in the axial direction to an end of the second belt ply on the first side in the axial direction, When the axial dimension from the end of the first belt ply on the second side in the axial direction to the end of the second belt ply on the second side in the axial direction is S2, The pneumatic tire according to (1), wherein S2 / S1 is less than 2.0 or greater than 8.0.

[0091] (12) The pneumatic tire according to any one of (1) to (11), wherein the ratio of the axial dimension of the second belt ply from the axial center position to the equator to half of the axial dimension of the tread is 0.3 or more and 0.5 or less. [Explanation of symbols]

[0092] 2. Pneumatic tires 4. Tread 14. Belt 17. Edge band 22 Tread surface 24... Groove 26s··· Shoulder land area 26c··· Center Land Section 61 First belt ply 62 Second belt ply 175··· Band cord 611... Axial first end of first belt ply 612.... Axial second end of first belt ply 621... Axial first end of second belt ply 622.... Axial second end of second belt ply 623... Axial center of second belt ply E: Axial dimension from the axial center position of the second belt ply to the equator F... Axial dimension of tread CL...Equatorial plane PC...equator S1: Axial dimension S2: Axial dimension W1: Axial dimension of the first belt ply W2: Axial dimension of the second belt ply X: Axial dimension of edge band

Claims

1. a tread having a tread surface that comes into contact with a road surface; a belt located radially inside the tread; an edge band covering an axial end of the belt; and The belt has a first belt ply provided passing through an equator plane and a second belt ply located radially outward of the first belt ply, the second belt ply is provided such that its axial center is offset toward the first axial side, the edge band is provided only on the second axial side and covers the end of the first belt ply on the second axial side, Pneumatic tires.

2. The axial dimension of the first belt ply is W1, The axial dimension of the second belt ply is W2, an axial dimension S1 from an end of the first belt ply on a first side in the axial direction to an end of the second belt ply on the first side in the axial direction, When an axial dimension from an end of the first belt ply on the second side in the axial direction to an end of the second belt ply on the second side in the axial direction is S2, W1>W2 W2 / W1 is 0.2 or more and 0.7 or less S2 / S1 is 2.0 or more and 8.0 or less The pneumatic tire according to claim 1 ,

3. The axial dimension of the edge band is 0.1×S2 or more and 0.6×S2 or less. The pneumatic tire according to claim 1 .

4. The edge band has a band cord containing aramid fiber, the first belt ply has an axial dimension larger than that of the second belt ply, When an axial dimension from an end of the first belt ply on the second side in the axial direction to an end of the second belt ply on the second side in the axial direction is S2, The axial dimension of the edge band is 0.1×S2 or more and 0.2×S2 or less. The pneumatic tire according to claim 1 .

5. The edge band has a band cord containing nylon fibers, the first belt ply has an axial dimension larger than that of the second belt ply, When an axial dimension from an end of the first belt ply on the second side in the axial direction to an end of the second belt ply on the second side in the axial direction is S2, The axial dimension of the edge band is 0.5×S2 or more and 0.6×S2 or less. The pneumatic tire according to claim 1 .

6. A tensile strength of a 50 mm width of one or both of the first belt ply and the second belt ply is 28000 N or more, The edge band has a band cord containing aramid fiber. The pneumatic tire according to claim 1 or claim 4.

7. A tensile strength of a 50 mm width of one or both of the first belt ply and the second belt ply is 20,500 N or less, The edge band has a band cord containing nylon fibers. The pneumatic tire according to claim 1 or claim 5.

8. The first axial side is the inner side in the vehicle mounting direction. The pneumatic tire according to claim 1 .

9. The tread has two shoulder land portions located on both axially outer sides and one or more center land portions located between the two shoulder land portions by forming a plurality of grooves on the tread surface along the circumferential direction, a ratio of a distance between an axially inner end of the edge band and the shoulder groove on the axially second side to an axial dimension of the shoulder land portion on the axially second side is 0.2 or more and 0.6 or less; The pneumatic tire according to claim 1 .

10. The axial dimension of the first belt ply is W1, When the axial dimension of the second belt ply is W2, W1>W2 W2 / W1 is less than 0.2, or W2 / W1 is greater than 0.7; The pneumatic tire according to claim 1 .

11. the first belt ply has an axial dimension larger than that of the second belt ply, an axial dimension S1 from an end of the first belt ply on a first side in the axial direction to an end of the second belt ply on the first side in the axial direction, When an axial dimension from an end of the first belt ply on the second side in the axial direction to an end of the second belt ply on the second side in the axial direction is S2, S2 / S1 is less than 2.0, or S2 / S1 is greater than 8.0; The pneumatic tire according to claim 1 .

12. a ratio of an axial dimension of the second belt ply from an axial center position to an equator to half of an axial dimension of the tread is 0.3 or more and 0.5 or less; The pneumatic tire according to claim 1 .

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