pneumatic tires

Abstract

We offer pneumatic tires that provide excellent durability while incorporating different colored rubber on the sidewall. [Solution] The pneumatic tire 1 according to the embodiment is provided with a different colored rubber portion 32 on the sidewall 30, which is made of rubber with a lower carbon black content than the rubber constituting the sidewall 30, and the length C in the tire radial direction from the outer end of the different colored rubber portion 32 in the tire radial direction to the annular projection 47 formed at the boundary between the sector of the tire vulcanization mold and the side plate is 8% or more and 28% or less of the tire cross-sectional height H, and the tire thickness from the inner surface to the outer surface in the tire axial cross-section in the tire axial state when the tire is not filled with normal rim assembly pressure is smaller at the tire axial center CL than at the contact end E.

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] For the purpose of improving the visibility and designability of tires, there is known a sidewall formed of a different-color rubber composition such as white rubber for pattern portions such as characters, symbols provided on the sidewall, and lines or figures provided continuously or discontinuously in the tire circumferential direction. This type of sidewall is formed, for example, by disposing a different-color rubber while radially dividing a predetermined portion of the unvulcanized black rubber forming the sidewall, providing a black cover rubber layer on the different-color rubber, and then vulcanizing the formed green tire in a predetermined mold, and then grinding a part of the cover rubber layer to expose the different-color rubber as a pattern portion.

[0003] As a technique related to a sidewall in which a different-color rubber is disposed, for example, Patent Document 1 discloses that in order to suppress a black residue phenomenon in which black rubber is partially exposed in a pattern portion, the volume of the different-color rubber is set to 60% or more and 70% or less of the volume of the black rubber.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A tire having a sidewall in which a different-color rubber is disposed as in Patent Document 1 has an interface between the different-color rubber and the black rubber, so that the number of interfaces increases compared to a tire having only a black sidewall, and the durability is likely to decrease. In particular, when the sectional height of the tire becomes small, strain concentrates near the outer end in the tire radial direction of the different-color rubber, and separation is likely to occur.

[0006] In view of the above, an embodiment of the present invention aims to provide a pneumatic tire that exhibits excellent durability while having a different colored rubber on the sidewall. [Means for solving the problem]

[0007] The present invention includes embodiments shown below.

[0008] [1] A pneumatic tire formed in a tire vulcanizing mold having a pair of bead portions arranged spaced apart in the tire axial direction, a pair of sidewalls provided radially outward from the pair of bead portions, a tread provided between the pair of sidewalls, a carcass ply locked from the tread through the sidewalls to the bead portion, and a different colored rubber portion provided on the tire axially outward of the carcass ply on the sidewall, made of rubber with a lower carbon black content than the rubber constituting the sidewall, a sector forming at least a part of the tread, and a side plate in contact with the sector and forming at least a part of the sidewall, wherein the length in the tire radial direction from the radially outward end of the different colored rubber portion to an annular projection formed at the boundary between the sector and the side plate that is continuous in the tire circumferential direction is 8% or more and 28% or less of the tire cross-sectional height, and the tire thickness from the inner surface to the outer surface in the tire axial cross-section in a tire axial state without filling of the normal rim assembly pressure is smaller at the tire axial center than at the contact edge.

[0009] [2] A pneumatic tire formed in a tire vulcanization mold having a pair of bead portions arranged spaced apart in the tire axial direction, a pair of sidewalls provided radially outward from the pair of bead portions, a tread provided between the pair of sidewalls, a carcass ply locked from the tread through the sidewalls to the bead portion, and a different colored rubber portion provided on the tire axially outward from the carcass ply in the sidewall, and made of rubber with a lower carbon black content than the rubber constituting the sidewall, and a sector forming at least a part of the tread, and a side plate in contact with the sector and forming at least a part of the sidewall The tire is a pneumatic tire in which, within the region sandwiched by the contact edges of the tread, the central region is defined as the area of ​​60% of the contact width centered on the axial center of the tire, and the area of ​​the central region is defined as the area of ​​the opening area of ​​the recess provided in the central region to the area of ​​the central region, and the area of ​​the opening area of ​​the recess provided in the shoulder region is defined as the area of ​​the shoulder region to the area of ​​the shoulder region, and the central void ratio is defined as the ratio of the opening area of ​​the recess provided in the central region to the area of ​​the shoulder region, and the central void ratio is defined as the ratio of the opening area of ​​the recess provided in the shoulder region to the area of ​​the shoulder region, the central void ratio is greater than the shoulder void ratio.

[0010] [3] The pneumatic tire according to [1] or [2] above, wherein the tread comprises a belt in which a plurality of cords are covered with rubber, and a tread rubber provided on the radially outer side of the belt, and the inclination angle of the cords with respect to the circumferential direction of the tire is 22 degrees or more and 28 degrees or less.

[0011] [4] The pneumatic tire according to any one of [1] to [3] above, wherein the tread comprises a belt in which a plurality of cords are covered with rubber, and a tread rubber provided on the outer side of the belt in the radial direction of the tire, and the rubber hardness of the tread rubber is 52 or more and 68 or less.

[0012] [5] The pneumatic tire according to any one of [1] to [4] above, wherein the bead portion comprises a bead core and a bead filler provided on the radially outer side of the bead core, and the radially outer end of the bead filler is arranged to overlap with the differently colored rubber portion in the axial direction of the tire.

[0013] [6] The pneumatic tire according to any one of [1] to [5] above, wherein the tread comprises a belt in which a plurality of cords are covered with rubber, and a tread rubber provided on the radially outer side of the belt, the tread rubber comprising a cap rubber layer on which a tread surface is formed, and a base rubber layer provided on the radially inner side of the cap rubber layer and having a lower rubber hardness than the cap rubber layer, the rubber thickness of the cap rubber layer at the axial center of the tire is smaller than the rubber thickness of the cap rubber layer at a position 37.5% of the contact width outward from the axial center of the tire.

[0014] [7] The pneumatic tire according to any one of [1] to [6] above, wherein the tread is provided with at least three main grooves, including at least one center main groove and a pair of shoulder main grooves located on both sides of the center main groove in the tire axial direction, and the groove depth of the center main groove is greater than the groove depth of the shoulder main grooves.

[0015] [8] A pneumatic tire according to any one of [1] to [6] above, wherein, of the region sandwiched between the contact edges of the tread, the central region is defined as the area of ​​60% of the contact width centered on the axial center of the tire, and the area outside the central region in the axial direction of the tire is defined as the shoulder region, and a main groove extending in the circumferential direction of the tire is provided in the central region, and no main groove extending in the circumferential direction of the tire is provided in the shoulder region. [Effects of the Invention]

[0016] According to an embodiment of the present invention, in a pneumatic tire with different colored rubber arranged on the sidewall, the occurrence of separation can be suppressed and durability can be improved. [Brief explanation of the drawing]

[0017] [Figure 1] Half-sectional view of a pneumatic tire according to the first embodiment of the present invention [Figure 2] Developed view showing the tread pattern of the pneumatic tire of FIG. 1 [Figure 3] Developed view showing the tread pattern of a pneumatic tire according to Modification Example 1 of the present invention [Figure 4] Half-sectional view of a pneumatic tire according to Modification Example 2 of the present invention [Figure 5] Half-sectional view of a pneumatic tire according to Modification Example 3 of the present invention [Figure 6] Half-sectional view of a pneumatic tire according to Modification Example 4 of the present invention

MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments will be described with reference to the drawings.

[0019] In the drawings, reference numeral CL indicates the tire equatorial plane and corresponds to the center in the tire axial direction. Here, the tire radial direction is a direction perpendicular to the tire rotation axis, and is indicated by reference numeral RD in the drawing. The inner side in the tire radial direction is a direction approaching the tire rotation axis, and the outer side in the tire radial direction is a direction away from the tire rotation axis. The tire axial direction is a direction parallel to the tire rotation axis, and is indicated by reference numeral WD in the drawing. The inner side in the tire axial direction is a direction approaching the center CL in the tire axial direction, and the outer side in the tire axial direction is a direction away from the center CL in the tire axial direction. The tire circumferential direction is a direction on the circumference centered on the tire rotation axis, and is indicated by arrow CD in the drawing.

[0020] Also, in the drawings, reference numeral E indicates the grounding end of the tire. The grounding end E is the outermost position in the tire axial direction WD on the ground contact surface. The ground contact surface refers to the surface of the tread portion that contacts the road surface when the tire is mounted on a regular rim, filled with a regular internal pressure, placed vertically on a flat road surface, and a regular load is applied.

[0021] The regular rim is the rim defined for each tire in a standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the standard rim, and in the case of TRA and ETRTO, it is the "Measuring Rim".

[0022] The regular load is the load defined for each tire in a standard system including the standards on which the tire is based. In the case of JATMA, it is the maximum load capacity, in the case of TRA, it is the maximum value described in the above table, and in the case of ETRTO, it is the "LOAD CAPACITY".

[0023] The regular internal pressure is the "maximum air pressure" in the JATMA standard, the "maximum value" described in "TIRELOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard.

[0024] In addition, in this specification, "overlap" includes not only the case where tire components such as bead fillers, carcass plies, belt plies, and tread rubbers directly contact and overlap each other, but also the case where they overlap through another member in between.

[0025] (1) Basic Structure of Pneumatic Tire 1 The pneumatic tire 1 according to an embodiment shown in FIGS. 1 and 2 includes a pair of left and right bead portions 20, a pair of left and right sidewalls 30 extending radially outward from the bead portions 20 in the tire diameter direction, and a tread 40 connecting the radially outer ends of the sidewalls 30 in the tire diameter direction to form a ground contact surface. The pneumatic tire 1 of this embodiment is a low-profile pneumatic tire with a tire cross-sectional height H of 85 mm or more and 150 mm or less. Note that the tire cross-sectional height H is the length in the tire diameter direction from the inner diameter surface to the outer diameter surface of the unloaded pneumatic tire 1 mounted on the regular rim and filled with the regular internal pressure.

[0026] Each of the pair of bead portions 20 has a ring-shaped bead core 21 embedded in it. On the outer side of the bead core 21 in the tire radial direction, there is a bead filler 22 made of hard rubber that tapers outward in the tire radial direction. On the bead portion 20, a rim strip rubber 3 is provided on the outer side of the bead filler 22 in the tire axial direction WD. The rim strip rubber 3 is a rubber member that forms the outer surface of the bead portion 20 and contacts a wheel rim (not shown) on which the pneumatic tire 1 is mounted.

[0027] The pneumatic tire 1 includes a carcass 50 that is toroidally spanned between a pair of bead portions 20. The carcass 50 is secured by folding back around the bead core 21 in the tire axial direction from the inside to the outside, from the tread 40 through the sidewall 30 to the bead portion 20. An inner liner 2 is provided on the inner surface of the carcass 50 as an air-permeable rubber layer.

[0028] A side reinforcement layer 80 is provided on the outer side of the tire axial direction WD of the bead filler 22 in the bead portion 20, and a rim strip rubber 3 is provided on the outer side of the tire (i.e., the outer side of the tire axial direction WD) of the carcass 50 in the bead portion 20. A sidewall rubber 31 and a different colored rubber portion 32 are provided on the outer side of the tire of the carcass 50 in the sidewall 30. A belt 70 is provided on the outer side of the tire radial direction RD of the carcass 50 in the tread 40, and a belt reinforcement layer 73 and tread rubber 41 are laminated on the outer side of the tire radial direction RD of the belt 70.

[0029] As shown in Figure 1, an annular projection 47 extending in the tire circumferential direction CD is provided near the boundary between the sidewall 30 and the tread 40. The annular projection 47 is provided continuously around the entire circumference of the tire circumferential direction CD. The annular projection 47 is provided at the boundary position (parting line) PL between the sector, which is the mold for forming the tread 40, and the side plate, which is the mold for forming the sidewall 30.

[0030] (2) Belt 70 The belt 70 consists of at least two intersecting belt plies, in which the belt cords are arranged at an inclination angle of 10 to 35 degrees, preferably 22 to 28 degrees, with respect to the tire circumferential direction CD. In this example, it has a two-layer structure with a first belt ply 71 located on the inside of the tire radial direction RD and a second belt ply 72 located on its outer circumference. Of these, the first belt ply 71 is the widest belt, and its outer end in the tire axial direction WD corresponds to the outer end 70A in the tire axial direction of the belt 70. Steel cords or high-tensile organic fiber cords can be used as the belt cords.

[0031] In this example, a belt reinforcing layer 73 is provided on the outer side of the belt 70 in the tire radial direction RD, i.e., between the belt 70 and the tread rubber 41. The belt reinforcing layer 73 is composed of cap plies having cords that extend substantially parallel to the tire circumferential direction CD.

[0032] Furthermore, a rubber layer 74 is provided between the tire axial WD end of the first belt ply 71 and the carcass 50, which does not contain cord reinforcing materials such as organic fibers or steel cords.

[0033] (3) Carcass 50 The carcass 50 comprises two carcass plies, namely a first carcass ply 51 and a second carcass ply 52, which are laminated so that the constituent cords extend inclined with respect to the tire circumferential direction CD and the constituent cords are facing in opposite directions. The carcass plies 51 and 52 are in the form of sheets made of multiple parallel cords covered with rubber. The multiple cords of the carcass plies 51 and 52 may be, for example, organic fiber cords such as polyester fibers, rayon fibers, aramid fibers, nylon fibers, or steel cords.

[0034] The first carcass ply 51 consists of a first main body portion 51A that extends from the tread 40 through the sidewall 30 to the bead core 21 of the bead portion 20, and a first folded portion 51B that extends from the first main body portion 51A and is folded back around the bead core 21 from the inside to the outside in the tire axial direction WD.

[0035] The first main body portion 51A passes through the inner side of the tire axial direction WD of the bead filler 22 and reaches the inner side of the tire radial direction RD of the bead core 21. The first folded portion 51B is wound up from the inner side of the tire radial direction RD of the bead core 21, passing through the outer side of the tire axial direction WD of the bead filler 22, and out to the outer side of the tire radial direction RD.

[0036] The second carcass ply 52 consists of a second main body portion 52A that extends from the tread 40 through the sidewall 30 to the bead core 21 of the bead portion 20, and a second folded portion 52B that extends from the second main body portion 52A and is folded back around the bead core 21 from the inside to the outside in the tire axial direction WD.

[0037] The second main body portion 52A is positioned on the tread 40 on the radial side of the first main body portion 51A, extends along the outer surface of the first main body portion 51A toward the bead portion 20, passes between the first main body portion 51A and the bead filler 22, and reaches the inner side of the bead core 21 in the radial direction RD. The second folded portion 52B is wound up from the inner side of the bead core 21 in the radial direction RD, passes between the bead filler 22 and the first folded portion 51B, and is wound outwards in the radial direction RD.

[0038] The first carcass ply 51 has a first folded portion 51B that extends inward in the tire axial direction WD from the outer end 70E of the belt 70. That is, the first folded end 51BE, which is the outer end of the first folded portion 51B in the tire radial direction RD, is located inward in the tire axial direction WD from the outer end 70E of the belt 70 and is positioned to overlap with the belt 70 in the direction normal to the first folded portion 51B. In this example, the first folded end 51BE is located inward in the tire axial direction WD from the outer end 72E of the second belt ply 72 and is positioned to overlap with the tire axial direction WD end of the second belt ply 72 in the direction normal to the first folded portion 51B.

[0039] In this example, a rubber layer 74 is provided between the first belt ply 71 of the belt 70 and the outer end RD in the tire radial direction of the first folded portion 51B, so that the first folded end 51BE of the first folded portion 51B does not directly contact the first belt ply 71 of the belt 70, but overlaps with it via the rubber layer 74.

[0040] The second carcass ply 52 has a second folded portion 52B that extends radially RD outward from the tip (i.e., outer end in the tire radial direction) 22A of the bead filler 22, and terminates before the outer end 70A of the belt 70. More specifically, the second folded end 52BE, which is the outer end in the tire radial RD of the second folded portion 52B, is positioned so as not to overlap with the belt 70 in the direction normal to the second folded portion 52B, but to overlap with the tread rubber 41. The second folded end 52BE of the second folded portion 52B is sandwiched between the second main body portion 52A of the second carcass ply 52 and the first folded portion 51B of the first carcass ply 51.

[0041] (4) Tread 40 The tread 40 is provided with tread rubber 41 on the outer circumference side (outer side in the tire radial direction) of the belt reinforcement layer 73. The tread rubber 41 has a two-layer structure consisting of a cap rubber layer 42 having a tread surface that contacts the road surface, and a base rubber layer 43 arranged on the inner side of the cap rubber layer 42 in the tire radial direction RD. The tread rubber 41 covers the outer end of the sidewall rubber 31 provided on the sidewall 30 in the tire radial direction RD. Alternatively, the tread rubber 41 and sidewall rubber 31 may be arranged such that the outer end of the sidewall rubber 31 in the tire radial direction RD covers the axial end WD of the tread rubber 41 from the outside.

[0042] The cap rubber layer 42 has multiple main grooves 44A and 44B formed in it, extending along the tire circumferential direction CD and spaced apart in the tire axial direction WD. In this example, there is a pair of center main grooves 44A located on both sides of the tire axial center CL, and a pair of shoulder main grooves 44B located outside of them.

[0043] The cap rubber layer 42 is divided into multiple land sections 45A, 45B, and 45C in the tire axial direction WD by multiple main grooves 44A and 44B. Specifically, it is provided with a center land section 45A sandwiched between a pair of center main grooves 44A, 44A, a pair of left and right intermediate land sections 45B sandwiched between the center main groove 44A and the shoulder main groove 44B, and a pair of left and right shoulder land sections 45C formed between the shoulder main groove 44B and the contact end E. Each land section 45A, 45B, and 45C is provided with a lateral groove 46 extending in a direction intersecting the tire circumferential direction CD.

[0044] The base rubber layer 43 consists of a rubber layer with a substantially constant thickness, provided on the radially outer side of the belt reinforcement layer 73. The base rubber layer 43 may be made of a rubber composition having the same rubber hardness as the rubber composition that constitutes the cap rubber layer 42. Alternatively, the base rubber layer 43 may be made of a rubber composition with lower rubber hardness than the rubber composition that constitutes the cap rubber layer 42.

[0045] It is preferable to use a rubber composition with a rubber hardness in the range of 52 to 68 for the cap rubber layer 42 and base rubber layer 43 that constitute the tread rubber 41.

[0046] In this specification, rubber hardness is defined as JIS K6253-1-2012 3.2 durometer hardness, and is measured using a Type A durometer for general rubber (medium hardness) in an atmosphere of 23°C.

[0047] In the pneumatic tire 1 of this embodiment, when the tire is mounted on a regular rim and the internal pressure is not filled (regular rim mounting, internal pressure not filled), the tire thickness THc at the center of the tire axial WD cross section is smaller than the tire thickness Te at the contact end E.

[0048] Here, the tire thickness THc at the axial center CL of the tire is the tire thickness at the normal to the tire surface profile at the axial center CL, and the tire thickness Te at the contact end E is the tire thickness at the normal to the tire surface profile at the contact end E. The tire surface profile is the contour line of the outer surface of the tread 40 excluding the main grooves 44A and 44B, and is usually defined by a curve formed by smoothly connecting multiple arcs.

[0049] In other words, as shown in Figures 1 and 2, the tire thickness THc at the center CL in the tire axial direction is the length in the normal direction of the outer surface of the tread 40 from the outer surface of the cap rubber layer 42 that constitutes the outer surface of the tire to the inner surface of the inner liner 2 that constitutes the inner surface of the tire, when no grooves such as the main groove 44A or lateral groove 46 are provided at the center CL in the tire axial direction, and when a groove is provided at the center CL in the tire axial direction, it is the length in the normal direction of the outer surface of the tread 40 from the opening surface of the groove to the inner surface of the inner liner 2.

[0050] Furthermore, the tire thickness The at the contact end E is the length in the normal direction of the outer surface of the tread 40 from the outer surface of the cap rubber layer 42 to the inner surface of the inner liner 2 if there are no grooves such as lateral grooves 46 at the contact end E, and the length in the normal direction of the outer surface of the tread 40 from the opening of the groove to the inner surface of the inner liner 2 if there are grooves at the contact end E.

[0051] (5) Sidewall 30 The sidewall 30 is provided with sidewall rubber 31 and a different colored rubber portion 32. The sidewall rubber 31 is joined to the axial WD end of the tread rubber 41 at the outer end of the tire radial RD, and to the outer end of the radial RD of the rim strip rubber 3 at the inner end of the tire radial RD. The sidewall rubber 31, like the tread rubber 41 and rim strip rubber 3, is made of a black rubber composition (black rubber) that contains carbon black as a reinforcing filler.

[0052] In this embodiment, the discolored rubber portion 32 is made of white rubber, but it may be made of rubber colored in any color as long as it has a lower carbon black content than the sidewall rubber 31. The white rubber composition constituting the discolored rubber portion 32 can be any known white rubber composition commonly used for this application, and is not particularly limited.

[0053] For example, the discolored rubber portion 32 does not contain carbon black as a reinforcing filler, but is made of a rubber composition containing fillers other than carbon black, such as silica, talc, or clay (i.e., non-carbon black fillers). The sidewall rubber 31 is made of a rubber composition that is softer (lower hardness) and less rigid than the rim strip rubber 3. The discolored rubber portion 32 can be made of a rubber composition that is harder and less rigid than the black rubber composition containing carbon black that makes up the rim strip rubber 3 and the sidewall rubber 31. For example, the rubber hardness of the rim strip rubber 3 can be set to 60-85, the rubber hardness of the sidewall rubber 31 to 50-70, and the rubber hardness of the discolored rubber portion 12 to 40-70.

[0054] The discolored rubber portion 32 is arranged in an annular shape along the circumferential direction in a portion of the radial direction of the sidewall 30. A portion of the outer surface of the discolored rubber portion 32 is covered by a cover rubber layer (not shown) made of black rubber of the same color as the sidewall rubber 31, and the exposed portion of the discolored rubber portion 32 that is not covered becomes the discolored indicator portion 33.

[0055] The contrasting color display section 33 displays predetermined patterns, characters, symbols, designs, or lines and figures that are continuously or discontinuously arranged in the circumferential direction of the tire, using a color different from that of the sidewall rubber on the outer surface of the tire. This contrasting color display section 33 may be provided protruding from the outer surface of the tire. Furthermore, the contrasting color display section 33 may be provided in an annular shape continuously along the circumferential direction CD of the tire, or it may be provided discontinuously along the circumferential direction depending on the shape of the display.

[0056] As shown in Figure 1, the different-colored rubber portion 32 is provided at a position where the length C of the radial RD of the tire, from the outer end 32E1 in the tire radial direction to the annular projection 47 provided near the boundary between the sidewall 30 and the tread 40, is 8% to 28% of the tire cross-sectional height H. Preferably, the length C is 17% to 26% of the tire cross-sectional height H. By setting the ratio of the length C from the outer radial end 32E1 of the different-colored rubber portion 32 to the annular projection 47 to the tire section height H to 8% or more, the interface between the different-colored rubber portion 32 and the sidewall rubber 31 on the outer radial RD of the tire can be positioned away from the boundary between the tread 40 and the sidewall 30 where distortion is likely to occur, thereby suppressing the occurrence of separation. Furthermore, by setting the ratio of length C to tire section height H to 17% or more, durability can be further improved. Furthermore, by setting this ratio to 28% or less, the different-colored rubber portion 32 can be positioned in a conspicuous location on the sidewall 30, allowing the different-colored rubber to be exposed without exposing the black sidewall rubber in areas displaying patterns, letters, etc., thus preventing deterioration of appearance quality. In addition, the interface 4 between the different-colored rubber portion 32 and the sidewall rubber 31 on the inner side of the tire radial direction RD can be positioned away from the rim strip rubber 3 that contacts the wheel rim when mounted on the vehicle, thereby suppressing the occurrence of separation. By setting this ratio to 26% or less, the different-colored rubber can be exposed without exposing the sidewall rubber over a wide area in the tire radial direction, and the occurrence of separation can be further suppressed.

[0057] Furthermore, in this embodiment, the different-colored rubber portion 32 is provided such that the length D in the tire radial direction from the inner end 6a in the tire axial direction of the interface 6 between the different-colored rubber portion 32 and the upper sidewall rubber 32A to the first folded end 51BE of the first folded portion 51B of the first carcass ply 51 is 3.0% or more and 30% or less of the tire cross-sectional height H.

[0058] The different-colored rubber portion 32 may be provided at a position that includes the tire's maximum width position P1, or the different-colored rubber portion 32 may be provided such that the different-colored indicator portion 33 is located at the tire's maximum width position P1. Here, the tire's maximum width position P1 is the position where the length of the tire axial direction WD of the pneumatic tire 1 is at its maximum when it is mounted on a regular rim, subjected to regular internal pressure, and loaded with a regular load.

[0059] As shown in Figure 1, the discolored rubber portion 32 is provided in the region of the sidewall 30 on the inner side of the tire radial direction RD, extending from the outer surface of the tire in the tire axial direction WD to the first folded portion 51B of the first carcass ply 51. By providing the discolored rubber portion 32 in this way, the discolored rubber portion 32 radially divides the black sidewall rubber 31 near the center of the tire radial direction RD, forming an upper sidewall rubber 31A located on the outer side of the discolored rubber portion 32 in the tire radial direction RD and a lower sidewall rubber 31B located on the inner side of the discolored rubber portion 32 in the tire radial direction RD.

[0060] In this embodiment, the sidewall rubber 31 is divided in the tire radial direction RD by the different colored rubber portion 32, but the sidewall rubber 31 may be provided between the different colored rubber portion 32 and the first folded portion 51B of the first carcass ply 51, and the upper sidewall rubber 31A and the lower sidewall rubber 31B may be connected.

[0061] Furthermore, the outer end 32E1 of the different-colored rubber portion 32 in the tire radial direction may be located radially outward from the outer end (tip) 22E of the bead filler 22 in the tire radial direction, and the inner end 32E2 of the different-colored rubber portion 32 in the tire radial direction may be located radially inward from the tip 22E of the bead filler 22. In other words, the tip 22E of the bead filler 22 may be positioned to overlap with the different-colored rubber portion 32 in the tire axial direction WD via the first folded portion 51B and the second folded portion 52B of the carcass 50. In this embodiment, the tip 22E of the bead filler 22 extends radially outward to a position where it overlaps with the different-colored indicator portion 33 in the tire axial direction WD.

[0062] By positioning the tip 22E of the bead filler 22 so as to overlap with the discolored rubber portion 32 in the tire axial direction WD, the rigidity of the sidewall 30 can be increased and distortion of the entire sidewall can be suppressed. In addition, since the discolored rubber portion 32 does not overlap with the bead filler 22 in the tire axial direction WD across the entire tire radial direction, ride comfort is less likely to deteriorate.

[0063] In this embodiment, both ends of the different-colored rubber portion 32 in the tire radial direction are inclined to narrow as they move inward in the tire axial direction, and the radial length of the different-colored rubber portion 32 on the outer surface of the tire is set to be longer than the radial length on the inner surface of the tire.

[0064] Furthermore, the cross-sectional shape of the different-colored rubber portion 32 can be provided in various shapes. For example, both ends of the different-colored rubber portion 32 in the tire radial direction may be inclined to widen as they move inward in the tire axial direction, both ends of the different-colored rubber portion 32 in the tire radial direction may be provided substantially parallel to the tire axial direction, or one end of the different-colored rubber portion 32 in the tire radial direction may be inclined with respect to the tire axial direction, and the other end in the tire radial direction may be provided substantially parallel to the tire axial direction.

[0065] Furthermore, in this embodiment, the interface 5 between the lower sidewall rubber 31B and the rim strip rubber 3 is inclined so that it moves inward in the tire radial direction RD as it moves outward in the tire axial direction WD, and is inclined substantially parallel to the same direction as the interface 4 between the different colored rubber portion 32 and the lower sidewall rubber 31B.

[0066] In this embodiment, the inner end 32E2 of the differently colored rubber portion 32 in the tire radial direction is located further inward RD in the tire radial direction than the outer end 3E of the rim strip rubber 3 in the tire radial direction, and overlaps with the outer end of the rim strip rubber 3 in the tire radial direction via the lower sidewall rubber 31B in the tire axial direction.

[0067] (6) Side reinforcement layer 80 The side reinforcement layer 80 is a rubber layer formed by arranging multiple reinforcing cords, each made of steel cords or organic fiber cords, in parallel at predetermined intervals and covering them with rubber. The side reinforcement layer 80 is provided between the bead filler 22 and the second folded portion 52B. The inner end 80E2 of the side reinforcement layer 80 in the tire radial direction is positioned to overlap with the bead core 21 in the tire axial direction WD, extends outward in the tire radial direction RD along the outer side of the bead filler 22 in the tire axial direction WD, and terminates at least further outward in the tire radial direction RD than the lower sidewall rubber 31B.

[0068] In other words, the side reinforcement layer 80 has its inner end 80E2 in the tire radial direction located further inward RD than the inner end 5E in the tire axial direction of the interface 5 between the rim strip rubber 3 and the lower sidewall rubber 31B, and its outer end 80E1 in the tire radial direction is located further outward RD than the inner end 4E in the tire axial direction of the interface 4 between the lower sidewall rubber 31B and the different colored rubber portion 32.

[0069] Furthermore, the outer end 80E1 of the side reinforcement layer 80 in the tire radial direction may be positioned to overlap with the different colored rubber portion 32 in the tire axial direction WD, or to overlap with the different colored display portion 33 of the different colored rubber portion 32 in the tire axial direction WD, or to overlap with the upper sidewall rubber 31A in the tire axial direction WD. In addition, the outer end 80E1 of the side reinforcement layer 80 in the tire radial direction RD may be positioned inside the tire radial direction RD of the tire maximum width position P1, or outside the tire radial direction RD of the tire maximum width position P1.

[0070] (7) Effects In the pneumatic tire 1 of this embodiment, the length C in the tire radial direction from the outer end 32E1 of the different-colored rubber portion 32 to the annular projection 47 is 8% to 28% of the tire cross-sectional height, and a distance from the vicinity of the boundary between the sidewall 30 and the tread 40 is ensured. As a result, the stress acting on the interface between the different-colored rubber portion 32 and the upper sidewall rubber 31A can be reduced, the occurrence of separation at the interface can be suppressed, and durability can be improved.

[0071] In a low-profile pneumatic tire with a tire cross-sectional height H of 85 mm to 150 mm, as in this embodiment, strain tends to concentrate near the boundary between the tread 40 and the sidewall 30. Therefore, by setting the length C as described above to secure a distance from the boundary between the tread 40 and the sidewall 30, the stress acting on the interface between the discolored rubber portion 32 and the upper sidewall rubber 31A can be reduced.

[0072] Furthermore, in the pneumatic tire 1 of this embodiment, the tire thickness from the inner surface to the outer surface in the axial cross-section of the tire in the state where the internal pressure of the rim assembly is not filled is smaller at the center of the tire in the axial direction than at the contact edge, so that the tread 40 is more prone to bending deformation. As a result, the bending of the entire tire is more easily distributed to the tread 40, which suppresses bending deformation that occurs in the sidewall 30, suppresses the occurrence of separation at the interface between the different colored rubber portion 32 and the sidewall rubber 31, and improves durability.

[0073] In particular, in the case of low-profile pneumatic tires with a tire cross-sectional height H of 150 mm or less, if the different-colored display section 33 is placed in a conspicuous position on the sidewall 30, the different-colored rubber section 32 will be placed near the tire's maximum width position P1, which is prone to deformation when a load is applied. However, in this embodiment, since the tread 40 is configured to be easily flexed and deformed, deformation near the tire's maximum width position P1 is reduced, effectively suppressing the occurrence of separation at the interface between the different-colored rubber section 32 and the sidewall rubber 31, thereby improving durability.

[0074] In this embodiment, by setting the angle of the belt cord provided on the belt 70 with respect to the tire circumferential direction CD to 22 degrees or more and 28 degrees or less, the tread 40 can be restrained in the tire radial direction while allowing a moderate deformation. This suppresses bending deformation in the sidewall 30 without impairing the tire's running performance, thereby suppressing the occurrence of separation at the interface of the different colored rubber portion 32 and improving durability.

[0075] Furthermore, by adjusting the belt angle of the belt cord with respect to the tire circumferential CD within the above range, the tire's contact pressure becomes uniform, and the strain is distributed throughout the tire, thereby suppressing deflection deformation in the sidewall 30 and bead portion 20.

[0076] In this embodiment, by positioning the tip 22E of the bead filler 22 to overlap with the discolored rubber portion 32 when viewed from the tire axial direction, the interface between the discolored rubber portion 32 and the sidewall rubber 31 can be reinforced, thereby suppressing the occurrence of separation at the interface of the discolored rubber portion 32 and improving durability.

[0077] Furthermore, in the pneumatic tire 1 of this embodiment, the first folded portion 51B of the first carcass ply 51 extends inward in the tire axial direction beyond the outer end 70E of the belt 70, and the first folded end 51BE is positioned to overlap with the belt 70 in the direction normal to the folded portion 51B. This increases rigidity near the boundary between the tread 40 and the sidewall 30, suppressing distortion and preventing separation at the interface 6 between the different colored rubber portion 32 and the upper sidewall rubber 31A, thereby improving durability.

[0078] As in this embodiment, by positioning the first folded end 51BE further inward in the tire axial direction WD than the tire axial outer end 72E of the second belt ply 72, and positioning the first folded end 51BE so as to overlap with the second belt ply 72 in the direction normal to the first folded portion 51B, the reinforcing effect near the boundary between the tread 40 and the sidewall 30 is enhanced, and the occurrence of separation at the interface 6 can be further suppressed.

[0079] Furthermore, the second folded portion 52B of the second carcass ply 52 extends radially outward RD beyond the interface 6 between the different-colored rubber portion 32 and the upper sidewall rubber 31A, and the second folded end 52BE is positioned to overlap with the tread rubber 41 via the upper sidewall rubber 31A. This increases the rigidity near the interface 6 between the different-colored rubber portion 32 and the upper sidewall rubber 31A, suppresses the occurrence of separation at the interface 6, and improves durability.

[0080] The second folded end 52BE does not overlap with the belt 70 in the direction normal to the second folded portion 52B, and a distance is maintained between them. As a result, the ends of the belt plies 71, 72 and carcass plies 51, 52, which are prone to strain concentration, are not positioned to overlap near the boundary between the tread rubber 41 and the sidewall rubber 31, thereby improving tire durability, and also making it less likely for air to remain between components during tire manufacturing.

[0081] In this embodiment, the length D in the radial direction of the tire from the inner end 6a of the interface 6 in the tire axial direction to the first folded end 51BE of the first folded portion 51B is set to 3.0% or more and 30% or less of the tire cross-sectional height H. When the length D is 3.0% or more of the tire cross-sectional height H, it is possible to increase the rigidity near the discolored rubber portion 32 while ensuring the distance between the interface 6 and the first folded portion 51B, thereby improving tire durability. Furthermore, when the length D is 30% or less of the tire cross-sectional height H, the weight does not increase excessively, and rolling resistance does not worsen, thus preventing a decrease in fuel efficiency.

[0082] As in this embodiment, by providing a side reinforcing layer 80 between the bead filler 22 and the second folded portion 52B, the overall rigidity of the sidewall 30 can be increased, the applied load can be reduced, and the strain on the interfaces 4 and 6 between the different colored rubber portion 32 and the sidewall rubber 31 can be suppressed.

[0083] (8) Example of change Next, examples of modifications will be described. Various modifications can be made to the above embodiments without departing from the spirit of the invention. Several examples of modifications will be described below, but any one of the examples of modifications described below may be applied to the above embodiments, or any two or more of the examples of modifications described below may be applied in combination. In addition to the examples of modifications below, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. In the figures showing the examples of modifications, parts that are the same as in the above embodiments are denoted by the same reference numerals as in the above embodiments.

[0084] (8-1) Example of change 1 In this modification example, the void ratios for each region are set such that the central void ratio (TC) of the tread 40 is greater than the shoulder void ratio (TS) of the shoulder region.

[0085] Specifically, as shown in Figure 3, if the contact width TW is defined as the length of the tire axial direction WD in the area sandwiched between the contact edges E in the tread 40, that is, the distance between the contact edges E on both sides of the tire axial direction WD, then the central region TC is the area within 60% of the contact width TW centered on the tire axial center CL. The shoulder region TS is the area from the central region TC to the contact edges E on both sides of the tire axial direction WD.

[0086] The central void ratio is the ratio of the opening area of ​​the recess provided in the central region TC to the area of ​​the central region TC, that is, the ratio of the area of ​​the non-grounded portion to the central region TC. The shoulder void ratio is the ratio of the opening area of ​​the recess provided in the shoulder region TS to the area of ​​the shoulder region TS, that is, the ratio of the area of ​​the non-grounded portion to the shoulder region TS.

[0087] Here, the area of ​​the non-contact portion is the sum of the opening areas of the main grooves 44A, 44B and the lateral groove 46. Furthermore, if narrow grooves called sipes, with a width of 1.5 mm or less, are provided in the central region TC or the shoulder region TS, the opening area of ​​these narrow grooves is also included in the area of ​​the non-contact portion.

[0088] In this modified example, the central void ratio is greater than the shoulder void ratio, making the tread 40 more susceptible to flex deformation. This distributes the strain that tends to concentrate in the sidewall 30 during load input to the central region of the tread, suppressing flex deformation in the sidewall 30 and preventing separation at the interface between the discolored rubber portion 32 and the sidewall rubber 31.

[0089] (8-2) Example of modification 2 As shown in Figure 4, in Modification Example 2, the rubber thickness TGc of the cap rubber layer 42 of the tread 40 at the axial center CL of the tire is set to be smaller than the rubber thickness TGs of the cap rubber layer 42 at a position 37.5% of the contact width TW away from the axial center CL of the tire. In addition, in this Modification Example, the base rubber layer 43 uses a rubber composition with a lower rubber hardness than the rubber composition that constitutes the cap rubber layer 42.

[0090] In this modified example, the thickness of the cap rubber layer 42 is set smaller at the tire axial center CL compared to positions further away from the tire axial center CL towards the outside of the tire axial direction WD, making the tread 40 more susceptible to flex deformation. This distributes the load that tends to concentrate on the sidewall 30 during load input to the tread 40, suppressing flex deformation in the sidewall 30 and preventing separation at the interface between the different colored rubber portion 32 and the sidewall rubber 31.

[0091] (8-3) Example of modification 3 As shown in Figure 5, in modification example 3, the groove depth DA of the center main groove 44A is deeper than the groove depth DB of the shoulder main groove 44B. By providing groove depths for the center main groove 44A and the shoulder main groove 44B in this way, the tread 40 becomes more susceptible to flex deformation, and the strain that tends to concentrate in the sidewall 30 when a load is applied is concentrated in the central region of the tread 40, thereby suppressing the flex deformation that occurs in the sidewall 30 and preventing separation at the interface between the different colored rubber portion 32 and the sidewall rubber 31.

[0092] In Figure 5, the case in which two center main grooves 44A and two shoulder main grooves 44B are provided is explained. However, in cases where three or more main grooves are provided on the tread 40, such as when one center main groove is provided in the tire axial center CL of the tread 40 and shoulder main grooves are provided on both sides of it in the tire axial direction, resulting in three main grooves on the tread 40, or when intermediate main grooves and shoulder main grooves are provided on both sides of one center main groove in the tire axial direction, resulting in five main grooves on the tread 40, the groove depth of the center main groove is made deeper than the groove depth of the shoulder main groove. This distributes the strain that tends to concentrate on the sidewall 30 when a load is applied to the central region of the tread, suppressing the deflection deformation that occurs in the sidewall 30 and preventing the occurrence of separation at the interface between the different colored rubber portion 32 and the sidewall rubber 31.

[0093] (8-4) Example of modification 4 As shown in Figure 6, in modification example 4, the central region TC is defined as the area within the region sandwiched by the contact edges E of the tread 40, where 60% of the contact width TW is centered on the tire axial center CL, and the shoulder region TS is defined as the region from the central region TC to the contact edges E on both sides of the tire axial direction WD. In this case, a main groove 44A extending in the tire circumferential direction CD is provided in the central region TC, while a main groove extending in the tire circumferential direction CD is not provided in the shoulder region TS.

[0094] In this modified example as well, the tread 40 becomes more susceptible to flexural deformation, distributing the load that tends to concentrate on the sidewall 30 during load input to the tread 40, thereby suppressing the flexural deformation that occurs in the sidewall 30, and preventing separation at the interface between the different-colored rubber portion 32 and the sidewall rubber 31.

[0095] (8-5) Example of modification 5 The present invention is not limited to low-profile pneumatic tires with a tire cross-sectional height H of 150 mm or less, as described in the above embodiments, but is also applicable to pneumatic tires with a tire cross-sectional height H exceeding 150 mm.

[0096] (9) Examples The following are examples, but the present invention is not limited to these examples.

[0097] To demonstrate the effects of the above embodiments, pneumatic tires of Examples 1-3 and Comparative Examples 1 and 2 were prototyped.

[0098] The pneumatic tires of Examples 1-3 and Comparative Examples 1 and 2 are radial tires of size 165 / 60R15 with the cross-sectional shape shown in Figure 1 and the tread pattern shown in Figure 2, and the length C in the radial direction of the tire differs from the outer radial end 32E1 of the different colored rubber portion 32 to the annular projection 47. The length C, tire cross-sectional height H, and the ratio of length C to tire cross-sectional height H in the pneumatic tires of Examples 1-3 and Comparative Examples 1 and 2 are shown in Table 1.

[0099] In all examples, the cross-sectional height was 99 mm, and the configuration was the same except for length C.

[0100] The durability performance of each of these tires was evaluated. The evaluation methods are as follows:

[0101] • Durability Performance: Durability performance tests were conducted in accordance with the method specified in JIS D4230. If no failures such as separation were observed after completing test stage 3, the tire was subjected to continued load, and the distance traveled until failure was observed was measured and expressed as an index with the value of Example 1 set to 100. A higher index indicates better durability performance.

[0102] • Appearance Quality: The obtained pneumatic tires were visually inspected to see if black rubber had entered the discolored areas. If no black rubber had entered, it was marked with "○", and if black rubber had entered, it was marked with "×".

[0103] [Table 1]

[0104] The results are shown in Table 1. In Examples 1 to 3, separation was less likely to occur at the interface between the different-colored rubber portion 32 and the upper sidewall rubber 31A, demonstrating excellent durability. Furthermore, in Examples 1 to 3, the black rubber did not penetrate the different-colored display portion, resulting in excellent appearance quality. On the other hand, Comparative Example 1 showed inferior durability compared to Examples 1-3. Furthermore, in Comparative Example 2, black rubber had seeped into the areas with different colored markings. [Explanation of Symbols]

[0105] 1...Pneumatic tire, 2...Inner liner, 3...Rim strip rubber, 20...Bead section, 21...Bead core, 22...Bead filler, 30...Sidewall, 31...Sidewall rubber, 32...Different color rubber section, 33...Different color indicator section, 40...Tread, 41...Tread rubber, 42...Cap rubber layer, 43...Base rubber layer, 44A...Center main groove, 44B...Shoulder main groove, 45A...Center land section, 45B...Intermediate land section, 45C...Shoulder land section, 46...Lateral groove, 47...Annular projection, 50...Carcass, 51...First carcass ply, 51A...First main body section, 51B...First folded section, 52...Second carcass ply, 52A...Second main body section, 52B...Second folded section, 70...Belt, 71...First belt ply, 72...Second belt ply

Claims

1. A pair of bead sections are spaced apart in the axial direction of the tire, A pair of sidewalls provided radially outward from the pair of bead portions of the tire, A tread provided between a pair of sidewalls, A carcass ply that is locked from the tread through the sidewall to the bead portion, A different colored rubber portion is provided on the tire axial side of the carcass ply in the sidewall, and is made of rubber with a lower carbon black content than the rubber constituting the sidewall. Equipped with, In a pneumatic tire formed by a tire vulcanization mold having a sector that forms at least a portion of the tread and a side plate that abuts against the sector and forms at least a portion of the sidewall, The length in the radial direction of the tire from the outer end of the discolored rubber portion in the tire radial direction to the annular projection formed at the boundary between the sector and the side plate, which is continuous in the tire circumferential direction, is 8% or more and 28% or less of the tire cross-sectional height. A pneumatic tire in which, in a standard rim-mounted, uninflated state, the tire thickness from the inner surface to the outer surface in the axial cross-section of the tire is smaller at the axial center than at the contact edge.

2. A pair of bead sections are spaced apart in the axial direction of the tire, A pair of sidewalls provided radially outward from the pair of bead portions of the tire, A tread provided between a pair of sidewalls, A carcass ply that is locked from the tread through the sidewall to the bead portion, A different colored rubber portion is provided on the tire axial side of the carcass ply in the sidewall, and is made of rubber with a lower carbon black content than the rubber constituting the sidewall. Equipped with, In a pneumatic tire formed by a tire vulcanization mold having a sector that forms at least a portion of the tread and a side plate that abuts against the sector and forms at least a portion of the sidewall, The length C in the tire's radial direction from the outer end of the discolored rubber portion in the tire's radial direction to the annular projection formed at the boundary between the sector and the side plate, which is continuous in the tire's circumferential direction, is 8% or more and 28% or less of the tire's cross-sectional height H. A pneumatic tire in which, within the area sandwiched by the contact edges of the tread, the central region is defined as the area of ​​60% of the contact width centered on the axial center of the tire, the area outside the central region in the axial direction is defined as the shoulder region, the ratio of the opening area of ​​the recess provided in the central region to the area of ​​the central region is defined as the central void ratio, and the ratio of the opening area of ​​the recess provided in the shoulder region to the area of ​​the shoulder region is defined as the shoulder void ratio, wherein the central void ratio is greater than the shoulder void ratio.

3. The pneumatic tire according to claim 1 or 2, wherein the tread comprises a belt in which a plurality of cords are covered with rubber, and a tread rubber provided on the radially outer side of the belt, and the inclination angle of the cords with respect to the circumferential direction of the tire is 22 degrees or more and 28 degrees or less.

4. The tread comprises a belt in which multiple cords are covered with rubber, and a tread rubber provided on the radially outer side of the belt. The pneumatic tire according to claim 1 or 2, wherein the rubber hardness of the tread rubber is 52 or more and 68 or less.

5. The bead portion comprises a bead core and a bead filler provided on the radially outer side of the bead core. The pneumatic tire according to claim 1 or 2, wherein the outer end of the bead filler in the radial direction of the tire is arranged to overlap with the discolored rubber portion in the axial direction of the tire.

6. The tread comprises a belt in which multiple cords are covered with rubber, and tread rubber provided on the outer side of the belt in the radial direction of the tire. The tread rubber comprises a cap rubber layer on which a tread surface is formed, and a base rubber layer provided on the inner side of the cap rubber layer in the tire radial direction, with a lower rubber hardness than the cap rubber layer. The pneumatic tire according to claim 1 or 2, wherein the rubber thickness of the cap rubber layer at the axial center of the tire is smaller than the rubber thickness of the cap rubber layer at a position 37.5% of the contact width away from the axial center of the tire outward in the axial direction of the tire.

7. The tread is provided with at least three main grooves, including at least one center main groove and a pair of shoulder main grooves located on both sides of the center main groove in the tire axial direction. The pneumatic tire according to claim 1 or 2, wherein the groove depth of the center main groove is deeper than the groove depth of the shoulder main groove.

8. Of the region enclosed by the contact edges of the tread, the central region is defined as the area representing 60% of the contact width centered on the axial center of the tire, and the area outside the central region in the axial direction is defined as the shoulder region. The pneumatic tire according to claim 1 or 2, wherein a main groove extending in the circumferential direction of the tire is provided in the central region, and a main groove extending in the circumferential direction of the tire is not provided in the shoulder region.

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