pneumatic tires

Abstract

To provide a pneumatic tire configured so that the tire easily rolls straight and yet air resistance during high-speed rotation can be reduced to easily achieve low-fuel consumption.SOLUTION: A tire 1 comprises: a pair of bead cores 26 positioned with an interval in a width direction; a carcass 15 laid over the pair of bead cores 26; a belt 16 arranged at an outer periphery side of the carcass 15; an inner liner 18 arranged at an inner periphery side of the carcass 15; and a fiber material 19 arranged between the inner liner 18 and the carcass 15. The fiber material 19 is extended along an inner peripheral surface of the carcass 15 from an outside position closer to the outside in the width direction than a belt end 23 to an inside position closer to the inside in the width direction than the outside position. Fibers of the fiber material 19 are extended in a direction nearly perpendicular to a circumferential direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to pneumatic tires. [Background technology]

[0002] Conventionally, there is a pneumatic tire described in Patent Document 1. This pneumatic tire includes a reinforcing layer disposed between an inner liner and a carcass. The reinforcing layer includes an overlapping portion that overlaps an edge of a belt disposed on the outer circumferential side of the carcass when viewed from the radial direction. The reinforcing layer includes organic fibers. The organic fibers extend at an angle of 0° or more and 70° or less with respect to the circumferential direction of the tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-199758 Summary of the Invention [Problem to be solved by the invention]

[0004] In the pneumatic tire, the organic fibers extend at an angle of 0° to 70° relative to the circumferential direction, which gives the tire a tendency to deflect relative to the circumferential direction. This makes it difficult for the tire to roll straight in the direction of travel, which makes the tire more susceptible to wear and reduces the ride comfort. Patent Document 1 also states that if the angle of the organic fibers relative to the circumferential direction exceeds 70°, the reinforcing effect of the shoulders is insufficient, and the effect of preventing the shoulders from lifting up during high-speed driving is insufficient. However, if the shoulders can be rounded (curved) radially inward when the tire rotates at high speeds, the tire's air resistance during high-speed rotation can be reduced, which is preferable because it can achieve low fuel consumption.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a pneumatic tire that is easy to roll straight, reduces air resistance during high-speed rotation, and facilitates the realization of low fuel consumption. [Means for solving the problem]

[0006] The pneumatic tire of the present invention comprises a pair of bead cores spaced apart in the width direction, a carcass stretched across the pair of bead cores, a belt arranged on the outer periphery of the carcass, an inner liner arranged on the inner periphery of the carcass, and a fibrous material arranged between the inner liner and the carcass, wherein the fibrous material extends along the inner periphery of the carcass from an outer position located widthwise outside the belt end to an inner position located widthwise inside the outer position, and the fibers of the fibrous material extend in a direction approximately perpendicular to the circumferential direction.

[0007] In this specification, when the belt has a multi-layer structure of two or more layers, the belt end is referred to as the most diameter It is defined as the outer edge in the width direction of the belt located on the inner side in the width direction.

[0008] According to the present invention, the fibers of the fibrous material extend in a direction substantially perpendicular to the circumferential direction, which allows the tire to roll straight in the direction of travel. This reduces tire wear and improves ride comfort. Furthermore, by placing highly rigid fibrous material in areas with small radii of curvature where stress tends to concentrate, the moment (bending moment) required to bend those areas can be increased, preventing the tire from expanding radially due to centrifugal force when the tire rotates at high speed, thereby preventing the rounded shoulder shape from collapsing. Therefore, even when centrifugal force is applied to the tire when the tire rotates at high speed, the shoulders tend to maintain their rounded shape, preventing changes in airflow and suppressing the generation of unnecessary turbulence. This reduces the tire's air resistance and improves fuel economy. [Effects of the Invention]

[0009] The pneumatic tire according to the present invention is easy to roll in a straight line, and also reduces air resistance during high-speed rotation, making it easy to achieve low fuel consumption. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a half cross-sectional view of a pneumatic tire according to an embodiment of the present invention, taken along the radial and width directions of the pneumatic tire. FIG. [Figure 2] 2 is an enlarged cross-sectional view of the vicinity of a shoulder on one side in the width direction in FIG. 1. FIG. [Figure 3] 1 is a schematic cross-sectional view for explaining advantages that can be obtained by providing a fibrous material in a pneumatic tire. FIG. [Figure 4] FIG. 3 is an enlarged cross-sectional view corresponding to FIG. 2 of a comparative example pneumatic tire in which no fibrous material is present. [Figure 5] FIG. 1 is a cross-sectional view along the width direction and the radial direction showing the outer shape of one widthwise side portion of a pneumatic tire of a comparative example when inflated and when rotating at high speed, in which the outer shape when inflated is shown by dotted lines and the outer shape when rotating at high speed is shown by solid lines. [Figure 6] FIG. 6 is an enlarged cross-sectional view of the shoulder periphery in FIG. 5. [Figure 7] FIG. 1 is a cross-sectional view along the width direction and the radial direction showing the outer shape of the pneumatic tire of Example 2 at one width direction side portion when inflated and the outer shape of the pneumatic tire of Comparative Example at one width direction side portion when inflated, in which the outer shape of the pneumatic tire of Comparative Example is shown by dotted lines and the outer shape of the pneumatic tire of Example 2 is shown by solid lines. [Figure 8] FIG. 8 is an enlarged cross-sectional view of the shoulder periphery in FIG. 7. [Figure 9] FIG. 1 is a cross-sectional view along the width direction and the radial direction showing the outline of the shoulder of the pneumatic tire of Example 2 when rotating at high speed and the outline of the shoulder of the pneumatic tire of Comparative Example when rotating at high speed, superimposed on each other, in which the outline of the pneumatic tire of Comparative Example is shown by dotted lines and the outline of the pneumatic tire of Example 2 is shown by solid lines. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that, when multiple embodiments or variations are included below, it is assumed from the beginning that new embodiments will be constructed by appropriately combining their characteristic parts. Furthermore, in the following examples, the same components in the drawings will be given the same reference numerals, and redundant explanations will be omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios of length, width, height, etc. of each component between different drawings do not necessarily match. Furthermore, among the components described below, components that are not described in the independent claims that represent the highest concept are optional components and are not essential components. Furthermore, in the following description, when a belt has a multi-layer structure of two or more layers, the belt end will be referred to as the most diameter The width direction is defined as the outer end in the width direction of the belt (belt layer) located on the inner side in the width direction. Furthermore, when the belt has a multi-layer structure of two or more layers, the belt length is defined as the length of the belt located on the innermost side in the width direction. Furthermore, in the following description, the width direction is the width direction of the pneumatic tire 1, the radial direction is the radial direction of the pneumatic tire 1, and the circumferential direction is the circumferential direction of the pneumatic tire 1. The width direction, radial direction, and circumferential direction are perpendicular to each other.

[0012] FIG. 1 is a half cross-sectional view taken along the width and radial directions of a pneumatic tire 1 according to one embodiment of the present invention, including the radial and width directions of the pneumatic tire 1. As shown in FIG. 1, the pneumatic tire (hereinafter simply referred to as the tire) 1 includes a tread 10, a pair of shoulders 11, a pair of sidewalls 12, and a pair of beads 13. The tread 10 is disposed in the center in the width direction and includes a contact surface 10a that comes into contact with the road surface. The tread 10 is made of, for example, cross-linked rubber. A plurality of grooves 24 is provided on the outer peripheral surface of the tread 10. As is well known, the plurality of grooves 24 serve to drain rainwater that has entered between the road surface and the tire 1, thereby ensuring a contact area between the road surface and the tire 1.

[0013] The shoulders 11, sidewalls 12, and beads 13 form the side surfaces of the tire 1 and are provided on both sides of the tire 1 in the width direction. The shoulders 11, sidewalls 12, and beads 13 extend radially inward from both widthwise ends of the tread 10. In this embodiment, the contact edge E of the tire 1 is defined as the boundary between the tread 10 and the shoulders 11. The sidewalls 12 are rubber layers between the shoulders 11 and the beads 13 and are the most flexible part of the tire 1. The sidewalls 12 protect the carcass 15 (see FIG. 2) and prevent its elongation. The tire 1 may have annular ribs on the lateral sides. In this case, the annular ribs may be defined as the boundaries between the shoulders and the sidewalls. The contact edge E refers to both widthwise ends of the part of the tire 1 that comes into contact with the ground when the tire 1 is mounted on a standard rim, the internal pressure is adjusted to the standard internal pressure, and a standard load is applied (regular rims, etc., are the same as those described in JP 2020-131965 A).

[0014] The shoulders 11 are shoulder portions of the tire 1, and protrude outward in the width direction from both ends of the tread 10 in the width direction and extend radially inward. Like the tread 10, the shoulders 11 are provided in an annular shape along the circumferential direction. The sidewalls 12 extend radially inward from the shoulders 11 and are also provided in an annular shape along the circumferential direction. The sidewalls 12 include the portions that protrude most outward in the width direction of the tire 1, and are gently curved so as to be convex outward.

[0015] The bead 13 extends radially inward from the sidewall 12 and is formed in a ring shape along the circumferential direction. The bead 13 is a portion that is fixed to the rim of a wheel and constitutes the inner circumferential portion of the tire 1. The bead 13 is gently curved so as to convex toward the inside, and is located more inward than the sidewall 12 in the width direction.

[0016] The tire 1 includes a bead core 26 and a bead filler 27. The bead core 26 and the bead filler 27 are provided on both sides of the bead 13 in the width direction. The bead core 26 is a ring-shaped member made of bundled steel wires covered with rubber. The bead filler 27 is made of hard rubber and functions to increase the rigidity of the bead 13. The bead filler 27 is disposed radially outward of the bead core 26.

[0017] FIG. 2 is an enlarged cross-sectional view of the vicinity of a shoulder 11 on one side in the width direction in FIG. 1. As shown in FIG. 2, the tire 1 includes a carcass 15, a belt 16, a belt reinforcing material 17, an inner liner 18, and a pair of fiber materials 19. The carcass 15 is a cord layer covered with rubber. The carcass 15 includes carcass plies and forms a tire framework that withstands loads, impacts, air pressure, etc. The carcass 15 has a radial structure in which carcass cords are arranged extending in a direction perpendicular to the circumferential direction. The rubber layer that covers and protects the carcass 15 is generally made up of multiple rubber materials such as tread rubber and sidewall rubber.

[0018] The carcass ply constituting the carcass 15 is laid across the bead core 26 from the inner side in the width direction and folded back toward the sidewall 12 so as to wrap around the bead core 26 and the bead filler 27. In the example shown in FIG. 2 , a ply end 15E, which is the end of the carcass ply, is located on the sidewall 12. When the carcass 15 includes two carcass plies, the ply end of the other carcass ply is generally located on the bead 13.

[0019] The belt 16 is disposed between the tread 10 and the carcass 15. In the width direction, the belt 16 is installed over the entire area where it radially overlaps the tread 10 and over a portion of the shoulder 11. The belt 16 is a reinforcing band stretched in the circumferential direction, and it tightens the carcass 15 to increase the rigidity of the tread 10. The belt 16 has a two-layer structure, for example, made of a steel belt including a steel cord, and includes two steel belts 16a and 16b. However, the number of belts to be stacked is not limited to two. In addition, a belt including a tire cord using aramid fiber may be used instead of the steel belt. Alternatively, the belt may be configured with only one layer. By providing the belt 16, the rigidity of the tire 1 can be ensured, and the contact state between the tread 10 and the road surface can be improved.

[0020] The belt reinforcement 17 is disposed between the belt 16 and the tread 10. The belt reinforcement 17 has, for example, a two-layer structure and includes two cap plies 17a and 17b. The cap plies 17a and 17b are formed of, for example, insulating organic fiber layers such as polyamide fiber, and are covered with a topping rubber. The belt reinforcement 17 is installed for purposes such as improving durability and reducing road noise during driving. The number of laminated cap plies is not limited to two. The belt reinforcement 17 is disposed in the entire area where it radially overlaps the tread 10 and in a partial area of ​​the shoulder 11 in the width direction. An outer end 22 of the belt reinforcement 17 extends outward in the width direction beyond the belt 16.

[0021] The inner liner 18 is a rubber layer for maintaining air pressure and is attached to the inner surface of the carcass 15. The inner liner 18 is made of, for example, air-permeable rubber and prevents air from leaking from the tire cavity to the outside. The fibrous material 19 is an annular member and is disposed between the inner liner 18 and the carcass 15. A pair of fibrous materials 19 are disposed on both sides in the width direction, for example, disposed approximately symmetrically with respect to the tire equatorial plane with a gap in the width direction. The fibrous material 19 extends along the inner circumferential surface of the carcass 15 from an outer position located outward in the width direction from the belt end 23 to an inner position located inward in the width direction from the outer position. Here, the belt end 23 is the outer end in the width direction of the belt 6b located most inward in the width direction of the two-layer belt 16.

[0022] At least a portion of the fiber material 19 is arranged in a range (hereinafter referred to as a first range) from a position where the fiber material 19 substantially overlaps with the belt end 23 in the radial direction to a length along the inner circumferential surface of the carcass 15 that corresponds to 15% of the belt length in a cross section along the width direction and the radial direction (a cross section including the width direction and the radial direction). Here, the belt length is the length of the belt 6b located most inward in the width direction in the two-layer belt 16. In addition, the position where the fiber material 19 substantially overlaps with the belt end 23 in the radial direction may be defined as a position included in the range from a position shifted inward in the width direction along the inner circumferential surface of the carcass 15 by 1% of the belt length from the position where the fiber material 19 radially overlaps with the belt end 23 to a position shifted outward in the width direction along the inner circumferential surface of the carcass 15 by 1% of the belt length from the position where the fiber material 19 radially overlaps with the belt end 23.

[0023] 1 and 2, all of the fibrous material 19 is disposed in the first range, and more precisely, the fibrous material 19 is disposed in a cross section along the width and radial directions from a position where it radially overlaps with the belt end 23 to a position shifted laterally by a length along the inner circumferential surface of the carcass 15 that corresponds to 15% of the belt length. If the fibrous material extends beyond the position where it overlaps with the ply end 15E in the width direction, the tire rigidity may increase, which may affect the ride comfort of a vehicle equipped with the tire. Therefore, it is preferable that the fibrous material be disposed in a range from a position where it substantially overlaps with the belt end 23 in the radial direction to a position where it overlaps with the ply end 15E in the width direction, with respect to the direction along the inner circumferential surface of the carcass 15.

[0024] The fibrous material 19 is formed, for example, by aligning fibers and embedding them in a rubber composition. The base rubber of the rubber composition may be, for example, natural rubber, acrylonitrile-butadiene rubber (NBR), isoprene rubber (IR), isobutylene rubber (IIR), butadiene rubber (BR), styrene-butadiene rubber (SBR), or a blend of these. The fibers may be organic fibers, such as nylon fibers, rayon fibers, polyester fibers such as polyethylene terephthalate (PET) fibers and polyethylene naphthalate (PEN) fibers, aramid fibers, polyvinyl alcohol fibers, or steel cords. The fibers contained in the fibrous material 19 extend along the inner circumferential surface of the carcass in a direction substantially perpendicular to the circumferential direction. The Young's modulus of the fibrous material 19 may be any value, but is preferably 20 GPa or more, and more preferably 150 GPa or more.

[0025] <Advantages of arranging the fiber material of the present disclosure> 3 is a schematic cross-sectional view for explaining the advantages that can be obtained by installing the fiber material 19. When a bending moment M acts on the cross section shown in FIG. 3, the following formula (1) holds. 1 / ρ=M / (EI) (1) where ρ is the radius of curvature [cm] and E is the modulus of elasticity of the material [kg / cm 2 ] and I is the second moment of area [cm4 ] and E·I is the bending stiffness [kg·cm 2 ].

[0026] In the above formula (1), the second moment of area I is a factor that is independent of the material and depends only on the shape. Therefore, by placing a material with a high Young's modulus E in a location with a small radius of curvature ρ, the bending moment M in that location can be increased. Furthermore, the shoulder 11 has fewer belts 16 than the center portion in the width direction, making it less rigid. Therefore, by placing a highly rigid fiber material 19 in a location with a small radius of curvature where stress tends to concentrate, the moment (bending moment) required to bend that location can be increased. This prevents the tire 1 from expanding radially due to centrifugal force during high-speed tire rotation, which would cause the rounded shoulder shape to collapse. As a result, the shoulder 11 can more easily maintain its rounded shape even when centrifugal force is applied to the tire 1 during high-speed tire rotation, making it less likely for the airflow to change, suppressing the generation of unnecessary turbulence and reducing the air resistance of the tire 1.

[0027] Furthermore, when the fibers contained in the fiber material 19 extend in a direction approximately perpendicular to the circumferential direction, the tire 1 tends to roll straight and is less likely to become excessively hard, which tends to improve the ride comfort of a vehicle using the tire 1. Specifically, when the fibers of the fiber material extend in a direction that includes a circumferential extension component, the tire has a tendency to be biased relative to the circumferential direction, which is the direction of rotation of the tire, making it difficult for the tire 1 to roll straight in the direction of travel. Specifically, when the fibers of the fiber material extend in a direction that includes a large circumferential extension component, there is a risk that the reinforcing performance of the shoulder 11 will be excessively high, which may cause the tire 1 to become hard and result in a deterioration in ride comfort.

[0028] In contrast, when the fibers of the fiber material 19 extend in a direction approximately perpendicular to the circumferential direction, the tire 1 tends to roll straight in the direction of travel and does not become excessively stiff. Therefore, when the fibers of the fiber material 19 extend in a direction approximately perpendicular to the circumferential direction, not only can air resistance be reduced, but the tire 1 with appropriate rigidity can rotate smoothly and the ride comfort tends to be good.

[0029] (Air resistance and vertical stiffness test) The inventors of the present application produced the following tires of Examples 1 to 5 and a tire of a comparative example, and calculated the air resistance and vertical rigidity of each tire through tests.

[0030] [Example 1] A tire was produced that differed only in the position of the fiber material compared to the tire described in Figures 1 and 2. Acrylonitrile-butadiene rubber (NBR) was used as the base rubber of the rubber composition, and nylon fibers were used as the fibers. The fiber material was produced by embedding and integrating the nylon fibers into the rubber composition. The tire of Example 1 was produced by arranging the fiber material in a cross section along the width and radial directions (a cross section including the width and radial directions) from the belt end to a position shifted laterally along the inner circumferential surface of the carcass for a length of 10% of the belt length. The nylon fibers were arranged to extend in a direction approximately perpendicular to the circumferential direction.

[0031] [Example 2] 1 and 2 were produced. A tire of Example 2 was produced in comparison with Example 1, except that the fibrous material was arranged from the belt end to a position shifted laterally along the inner circumferential surface of the carcass for a length of 15% of the belt length in a cross section along the width direction and the radial direction.

[0032] [Example 3] In comparison with Example 1, the tire of Example 3 was different only in that the fiber material was positioned from the end of the belt to a position shifted to the side along the inner surface of the carcass for a length of 20% of the belt length in the cross section along the width direction and the radial direction.

[0033] [Example 4] In comparison with Example 1, the tire of Example 4 was a tire that differed only in that the fiber material was positioned in a cross section along the width and radial directions from the end of the belt to a position 35% of the belt length along the inner surface of the carcass.

[0034] [Example 5] In comparison with Example 1, the tire of Example 5 was different only in that the fiber material was positioned from the end of the belt to a position shifted to the side along the inner surface of the carcass for a length of 45% of the belt length in the cross section along the width direction and the radial direction.

[0035] [Comparative Example] In comparison with Example 1, a tire was taken as a comparative example, which differed only in that no fibrous material was disposed between the inner liner and the carcass.

[0036] <Evaluation of air resistance reduction> In order to objectively determine the effect of reducing air resistance, the inventors measured the drag, i.e., the force acting on a tire placed in an air flow, in the same direction as the flow and parallel to the flow, for each tire produced, and calculated the drag coefficient Cd (drag coefficient) using the following equation (2). Cd=D / (1 / 2ρU 2 S)···(2) where D is the drag force generated, ρ is the air density, and ρ is 1.225 kg / m 3 ]. U is the representative speed, which is the relative speed between the tire and the air, and is set to 27.8 [m / s]. S is the representative area of ​​the object. The inventors calculated Cd from these values ​​and the frontal projected area. Cd is expressed as a relative index where the value of the comparative example is set to 100. The smaller the index, the smaller the air resistance.

[0037] In Examples 1-5, acrylonitrile-butadiene rubber (NBR) was used as the base rubber of the rubber composition, and nylon fibers were used as the fibers, and the nylon fibers were embedded and integrated into the rubber composition to create a fibrous material. However, even when other base rubbers and other fibers were used, the values ​​of the drag coefficient Cd and the values ​​of the longitudinal stiffness described below did not change significantly.

[0038] <Vertical stiffness evaluation> Vertical stiffness is the radial stiffness of the tire. Each tire was mounted on a 19x7.0J rim at an air pressure of 250 kPa, and the vertical stiffness was calculated by dividing the change in vertical force between vertical loads of 4.5 kN ± 490 N with a camber angle of 0° by the change in vertical deflection. Vertical stiffness is expressed as a relative index, with the value of the comparative example set to 100. A higher index indicates greater vertical stiffness. Excessive stiffness may result in a decrease in ride comfort. In this way, ride comfort can be evaluated by calculating vertical stiffness.

[0039] [Table 1]

[0040] Table 1 shows the calculated Cd value and longitudinal stiffness for each tire. As shown in Table 1, air resistance gradually decreased as the length of the fiber material from the belt end increased, and air resistance plateaued and stopped decreasing when the length of the fiber material was 35% of the belt length. This is presumably because, when the fiber material extends beyond the point on the sidewall 12 where it bulges outward most in the width direction, it comes close to the wheel, which has high stiffness, and the extended fiber material portion no longer contributes to tire deformation. Therefore, by setting the length of the fiber material to a length longer than 0% and less than 35% of the belt length, air resistance can be reduced and the cost of the fiber material can be reduced.

[0041] Furthermore, from the viewpoint of longitudinal rigidity, up to Example 2, where the length of the fiber material is 15% of the belt length, the increase in longitudinal rigidity can be suppressed to within 4% compared to the comparative example, and the longitudinal rigidity does not increase significantly. On the other hand, in Example 3, where the length of the fiber material is 20% of the belt length, the longitudinal rigidity increases by 8%, which may affect the ride comfort. Therefore, from the viewpoint of ride comfort, Examples 1 and 2 are preferable. Note that if the fibers contained in the fiber material are extended in a direction that includes a large circumferential extension component, this undesirably causes circumferential deflection of the tire, and also increases the longitudinal rigidity of the fiber material. Therefore, there is a risk that the ride comfort may be significantly affected.

[0042] The inventors of the present invention identified the shapes of the tire of Example 2 and the tire of Comparative Example during high-speed rotation through computer simulation and investigated the degree of rounding (curvature) of the shoulders. Specifically, the inventors investigated the degree of rounding of the shoulders when the tires were rotated at 100 km / h in each computer simulation.

[0043] Fig. 4 is a cross-sectional view corresponding to Fig. 2 of a comparative tire 101 in which no fibrous material 19 is present. Fig. 5 is a cross-sectional view along the width direction and the radial direction showing the change in the outer shape of one widthwise side portion of the tire 101 when inflated and when rotating at high speed (when centrifugal force is applied), with the outer shape when inflated indicated by dotted lines and the outer shape when rotating at high speed indicated by solid lines. Fig. 6 is an enlarged cross-sectional view of a shoulder 111 in Fig. 5. Note that "when inflated" refers to when the tire 101 is inflated to a predetermined air pressure and stationary, and "when rotating at high speed" refers to when the inflated tire 101 is rotating at high speed.

[0044] As shown in Fig. 5, when the tire 101 rotates at high speed, centrifugal force acts on the tire 101, making it easier for the tread to deform radially outward. Also, as shown in Fig. 6, in the tire 101 that does not have a fibrous material, the outer shape of the shoulder 111 also expands significantly radially outward when rotating at high speed compared to when inflated, making it difficult for the shoulder 111 to maintain its rounded shape.

[0045] Next, the difference in shape between the tire of Example 2 and the tire of the Comparative Example when inflated will be described. Fig. 7 is a cross-sectional view along the width direction and the radial direction showing the outer shape of one widthwise side portion of tire 1 of Example 2 when inflated and the outer shape of one widthwise side portion of the tire of the Comparative Example when inflated, superimposed on each other, in which the outer shape of the tire of the Comparative Example is shown by dotted lines and the outer shape of the tire of Example 2 by solid lines. Fig. 8 is an enlarged cross-sectional view of the shoulder area in Fig. 7.

[0046] 7 and 8, in the tire of Example 2, the radially inner portion 80 of the shoulder bulges radially inward compared to the tire of the comparative example due to the placement of the fibrous material. However, the outer shape of other parts of the tire of Example 2 is almost the same as the outer shape of the tire of the comparative example. Therefore, the placement of the fibrous material does not change the aesthetic appearance of the tire very much.

[0047] Next, the difference in the shape of the shoulder between the tire of Example 2 and the tire of the Comparative Example during high-speed rotation will be described. Fig. 9 is a cross-sectional view taken along the width direction and the radial direction, showing the outline of the shoulder of the tire of Example 2 during high-speed rotation and the outline of the shoulder of the tire of the Comparative Example during high-speed rotation superimposed on each other, in which the outline of the tire of the Comparative Example is shown by a dotted line and the outline of the tire of Example 2 by a solid line.

[0048] As shown in Figure 9, during high-speed rotation, the inner circumferential surface 90b of the shoulder of the tire of Example 2 curves more radially inward than the inner circumferential surface 190b of the shoulder of the tire of the comparative example, thereby achieving a significant rounding of the inner circumferential surface 90b of the shoulder of the tire of Example 2 toward the radially inward direction. As a result, during high-speed rotation, the outer circumferential surface 90a of the shoulder of the tire of Example 2 is also less likely to deform radially outward, and curves more radially inward than the outer circumferential surface 190a of the shoulder of the tire of the comparative example, thereby achieving a significant rounding of the outer circumferential surface 90a of the shoulder of the tire of Example 2 toward the radially inward direction. Therefore, by arranging the fibrous material in the locations described in detail above, the outer circumferential surface 90a of the shoulder can be rounded during high-speed rotation, reducing air resistance during high-speed rotation and, as a result, improving fuel economy.

[0049] The present disclosure is not limited to the above-described embodiment and its modified examples, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents. For example, in the above-described embodiment, the fiber material 19 extends laterally along the inner circumferential surface of the carcass 15 from a position that substantially overlaps the belt end 23 in the radial direction in a cross section along the width direction and the radial direction. However, the fiber material may extend laterally along the inner circumferential surface of the carcass from a position that is located more inward in the width direction than the position that substantially overlaps the belt end in the radial direction in a cross section along the width direction and the radial direction. [Explanation of symbols]

[0050] 1 tire, 10 tread, 11 shoulder, 12 sidewall, 13 bead, 15 carcass, 15E ply end, 16 belt, 16a, 16b steel belt ply, 17 belt reinforcement, 17a, 17b cap ply, 18 inner liner, 19 fiber material, 22 widthwise outer end of belt reinforcement, 23 belt end, 24 groove, 26 bead core, 27 bead filler, 80 radially inner portion of shoulder.

Claims

1. a pair of bead cores spaced apart in the width direction; a carcass that is placed over the pair of bead cores; a belt disposed on an outer peripheral side of the carcass; a belt reinforcement disposed between the belt and the tread; an inner liner disposed on the inner circumferential side of the carcass; a fibrous material disposed between the inner liner and the carcass; Equipped with the fibrous material extends along an inner circumferential surface of the carcass from an outer position located outward of a belt end in the width direction to an inner position located inward of the outer position in the width direction, The fibers of the fibrous material extend in a direction substantially perpendicular to the circumferential direction, the belt is configured with a plurality of layers, and the outer end of the belt in the width direction is the outer end of the layer located most radially inner, the belt reinforcing member has a portion that extends outward in the width direction from an outer end of the belt in the width direction and is located radially inward from the outer end of the belt in the width direction, A pneumatic tire, wherein, in the width direction, the fiber material has a portion extending from inside to outside with respect to an outer end of the belt reinforcing material in the width direction.

2. 2. The pneumatic tire according to claim 1, wherein at least a portion of the fiber material is arranged in a range of a length along an inner circumferential surface of the carcass that corresponds to 15% of the belt length from a position that substantially overlaps with the belt end in the radial direction, in a cross section along the width direction and the radial direction.

3. 3. The pneumatic tire according to claim 2, wherein all of the fiber material is arranged in a range of a length along an inner circumferential surface of the carcass from a position where the fiber material substantially overlaps with the belt end in the radial direction, the length corresponding to 35% of the belt length.

4. The pneumatic tire according to claim 2 , wherein all of the fibrous material is disposed in the range.

5. The pneumatic tire according to claim 1 , wherein the fiber material has a Young's modulus of 20 GPa or more.

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