Tire

Abstract

To improve steering stability performance while achieving light weight.SOLUTION: This tire comprises a recess 20 formed in a manner that in a non-load state filled with prescribed inner pressure and mounted to a prescribed rim in a belt layer 7 of a three-piece structure, the width W2 of a second belt 72 from the inside in a tire radial direction is within the range 85[%]≤W2 / Wp≤95[%] with respect to the sectional width Wp of a carcass layer 4, and continuous in a tire circumferential direction on the tire outer surface outside the winding-up end 4c of the carcass layer 4 of a side wall 2 in the tire radial direction and inside a tire maximum width position in the tire radial direction in a manner that a contour line on a merida cross surface includes a plurality of circular arcs different in curvature radius.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a tire.

Background Art

[0002] For example, Patent Document 1 describes a pneumatic tire provided with a belt composed of at least three belt layers on the outer side in the tire radial direction of the carcass.

[0003] For example, Patent Document 2 describes a pneumatic tire in which recesses continuous in the tire circumferential direction are formed on the outer surface of the tire in the sidewall portion in order to achieve weight reduction while maintaining the durability performance of the bead portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, from the viewpoint of improving the transport efficiency of vehicles, in order to increase the actual loading capacity, weight reduction of tires has been demanded. Therefore, a structure in which the original four belt layers are reduced to three is conceivable. However, when the belt layer is structured with three layers, a phenomenon occurs in which the handling stability performance deteriorates.

[0006] An object of this invention is to provide a tire capable of improving the handling stability performance while achieving weight reduction.

Means for Solving the Problems

[0007] In order to achieve the above object, a tire according to one aspect of the present invention includes a tread portion, a pair of sidewall portions disposed on both sides of the tread portion, a pair of bead portions disposed on the inner side in the tire radial direction of each sidewall portion, at least one carcass layer spanned between the pair of bead portions, and a belt layer disposed in a three-sheet structure on the outer side in the tire radial direction of the carcass layer. In a no-load state where the tire is mounted on a specified rim and filled with a specified internal pressure, the width W2 in the tire width direction of the second belt from the inner side in the tire radial direction is formed in a range of 85[%] ≦ W2 / Wp ≦ 95[%] with respect to the cross-sectional width Wp of the carcass layer. Each of the bead portions has a bead core and a bead filler disposed on the outer side in the tire radial direction of the bead core. The carcass layer has a main body portion that is wound from the inner side to the outer side of the tire around the bead core and the bead filler and is located between the pair of bead portions, and a wound-up portion that is wound up on the outer side in the tire width direction of the bead core and the bead filler. When the width between the pair of bead portions in the non-rim assembled state is set to the specified rim width, a recess is provided on the outer surface of the tire on the outer side in the tire radial direction of the wound-up end of the carcass layer of at least one of the sidewall portions and on the inner side in the tire radial direction of the maximum tire width position, and the contour line in the meridian cross-section is composed of a plurality of arcs with different radii of curvature. A straight line drawn so as to be in contact with the outer contours of the sidewall portion and the bead portion in the meridian cross-section is defined as a tangent line L1, a point of contact where the tangent line L1 and the outer contour of the sidewall portion are in contact is defined as a contact point P1, a straight line passing through the wound-up end of the carcass layer and perpendicularly intersecting the main body portion is defined as a perpendicular line L2, and a straight line passing through the contact point P1 and perpendicularly intersecting the main body portion is defined as a perpendicular line L3. When the area A [mm 2 of the region surrounded by the outer contours of the sidewall portion and the bead portion and the tangent line L1, the area S [mm 2 of the region surrounded by the outer contours of the sidewall portion and the bead portion, the main body portion, the perpendicular line L2, and the perpendicular line L3, and the thickness G1 [mm] of the bead filler measured along the perpendicular line L2 satisfy the relationship of 0.10×(G1 - 17) ≦ A / (S + A) ≦ 0.05×(G1 - 10).

Advantages of the Invention

[0008] According to the present invention, it is possible to improve the handling stability while reducing the weight.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by this embodiment. In addition, the components of this embodiment include those that are replaceable and self-evidently replaceable while maintaining the identity of the invention. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope self-evident to those skilled in the art.

[0011] In the following description, the tire radial direction refers to the direction orthogonal to the tire rotation axis (not shown) which is the rotation axis of the pneumatic tire of the embodiment, the inner side in the tire radial direction refers to the side facing the tire rotation axis in the tire radial direction, and the outer side in the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. Also, the tire circumferential direction refers to the circumferential direction around the tire rotation axis as the central axis. Further, the tire width direction refers to the direction parallel to the tire rotation axis, the inner side in the tire width direction refers to the side facing the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is orthogonal to the tire rotation axis and passes through the center of the tire width of the pneumatic tire, and the tire equatorial plane CL coincides with the tire width direction center line which is the central position in the tire width direction of the pneumatic tire. The tire equator line refers to a line on the tire equatorial plane CL along the tire circumferential direction of the pneumatic tire. Also, the cross-section in the tire meridian direction (meridian cross-sectional view) refers to the cross-section when the tire is cut by a plane including the tire rotation axis.

[0012] In this embodiment, as an example, a pneumatic radial tire for heavy loads mounted on heavy load vehicles such as trucks and buses will be described.

[0013] The pneumatic tire of the embodiment has an annular structure centered on the tire rotation axis. As shown in FIG. 1, the pneumatic tire includes a pair of bead cores 5, a pair of bead fillers 6, a carcass layer 4, a belt layer 7, a tread rubber 11, a pair of sidewall rubbers 12, and a pair of rim cushion rubbers 13.

[0014] The pair of bead cores 5 is formed by winding one or a plurality of bead wires made of steel in an annular and multiple manner, and is embedded in the bead portion 3 to constitute the cores of the bead portions 3 on both sides in the tire width direction.

[0015] The pair of bead fillers 6 are respectively arranged on the outer side in the tire radial direction of the pair of bead cores 5 to reinforce the bead portion 3.

[0016] The carcass layer 4 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies. The carcass layer 4 is toroidally spanned between both bead cores 5 to constitute the skeleton of the tire. Further, both end portions of the carcass layer 4 are wound back and locked outward in the tire width direction so as to wrap the bead core 5 and the bead filler 6. Further, the carcass ply of the carcass layer 4 is formed by coating a plurality of carcass cords made of steel with a coat rubber and performing rolling processing. In the case of a radial tire, it has a cord angle (defined as the inclination angle of the longitudinal direction of the carcass cord with respect to the tire circumferential direction) of 80° or more and 90° or less in absolute value, and in the case of a bias tire, 30° or more and 45° or less. As shown in FIG. 2, the carcass layer 4 has a main body portion 4a and a winding-up portion 4b at both end portions spanned between both bead cores 5. The main body portion 4a is a portion mainly disposed inside the bead core 5 and the bead filler 6 in the tire width direction, and is wound up from the inside to the outside of the tire around the bead core 5 and the bead filler 6 and is located between the pair of bead portions 3. The winding-up portion 4b is a portion that is continuous with the main body portion 4a and is mainly located outside the bead core 5 and the bead filler 6 in the tire width direction, and the end wound up outside the bead core 5 and the bead filler 6 in the tire width direction forms the winding-up end 4c of the carcass layer 4.

[0017] The belt layer 7 has a three-ply structure formed by laminating three belt plies (belts) 71 to 73 in order from the inner side in the tire radial direction, and is disposed so as to surround the outer circumference of the carcass layer 4. These belt plies 71 to 73 include a pair of intersecting belts 71 and 72 and a belt cover 73. The pair of intersecting belts 71 and 72 are formed by covering a plurality of belt cords made of steel with a coating rubber and performing rolling processing. The pair of intersecting belts 71 and 72 have a cord angle (defined as the inclination angle of the longitudinal direction of the belt cord with respect to the tire circumferential direction) of 12° or more and 24° or less in absolute value. Also, the pair of intersecting belts 71 and 72 have cord angles of opposite signs to each other, and are laminated with the longitudinal directions of the belt cords intersecting each other (having a so-called cross-ply structure). The belt cover 73 is formed by covering a plurality of belt cords made of steel with a coating rubber and performing rolling processing. The belt cover 73 has a cord angle of 12° or more and 24° or less in absolute value. Also, the belt cover 73 is laminated on the outer side in the tire radial direction of the intersecting belt 72 and has the same sign cord angle as the intersecting belt 72.

[0018] The tread rubber 11 is disposed on the outer side in the tire radial direction of the carcass layer 4 and the belt layer 7 to constitute the tread portion 1 of the pneumatic tire. The tread rubber 11 has a tread surface (tread tread surface) 1a on the outer peripheral surface that contacts the road surface during running.

[0019] A pair of sidewall rubbers 12 are respectively disposed on the outer sides in the tire width direction of the carcass layer 4 to constitute the sidewall portions 2 on both sides in the tire width direction.

[0020] A pair of rim cushion rubbers 13 respectively extend from the inner side in the tire radial direction to the outer side in the tire width direction of the bead core 5 and the folded-back portion of the carcass layer 4 to constitute the rim fitting surface of the bead portion 3.

[0021] Further, as shown in FIG. 1, the pneumatic tire of the embodiment includes a plurality (five in FIG. 1) of circumferential main grooves 1b provided on the tread surface 1a with the tire equatorial plane CL as a boundary, and six rows of land portions 1c partitioned by the circumferential main grooves 1b.

[0022] The circumferential main groove 1b extends along the tire circumferential direction and has an annular structure that continuously extends over the entire circumference of the tire. The circumferential main groove 1b is defined as a groove having the obligation to display a wear indicator as defined in JATMA.

[0023] The groove width is measured as the maximum value of the distance between the opposing groove walls or edges at the opening edge portion on the tread surface in a non-loaded state where the tire is mounted on a specified rim and filled with a specified internal pressure.

[0024] The groove depth is measured as the maximum value of the distance from the tread surface to the groove bottom in a non-loaded state where the tire is mounted on a specified rim and filled with a specified internal pressure. Further, in a configuration having partial uneven portions or sipes at the groove bottom, these are excluded from the measurement.

[0025] The specified rim refers to the "Standard Rim" defined in JATMA, the "Design Rim" defined in TRA, or the "MEASURING RIM" defined in ETRTO. The specified internal pressure refers to the "Maximum Air Pressure" defined in JATMA, the maximum value of the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined in TRA, or the "INFLATION PRESSURES" defined in ETRTO. Note that the state where the tire is mounted on a specified rim and filled with a specified internal pressure is referred to as an inflated state.

[0026] In the pneumatic tire of the embodiment, as shown in FIGS. 2 and 3, a recess 20 continuous in the tire circumferential direction is provided on the outer surface of at least one of the sidewall portion 2 and the bead portion 3. Hereinafter, the configuration related to the recess 20 will be described.

[0027] When the width between the pair of bead portions 3 in the non-rim assembled state is set to the specified rim width, the recess 20 is disposed radially outside the winding end 4c of the carcass layer 4 and radially inside the tire maximum width position P in the tire diameter direction. In other words, in the recess 20, a contact point P1 described later is located radially inside the tire maximum width position P, and a contact point P2 described later is located radially outside the winding end 4c of the carcass layer 4. By providing such a recess 20, the amount of rubber in the vicinity of the bead portion 3 can be suppressed, and the tire weight can be reduced.

[0028] The specified rim width (Wr) is the width of a specified rim (the "Applicable Rim" specified by JATMA, the "Design Rim" specified by TRA, or the "Measuring Rim" specified by ETRTO).

[0029] The contour line of the recess 20 in the meridian cross section is composed of a plurality of arcs with different radii of curvature and is smoothly curved. For example, the contour line of the recess 20 can be formed by a combination of an arc convex outward in the tire width direction and an arc convex inward in the tire width direction. In particular, among the plurality of arcs constituting the contour line of the recess 20, the innermost arc and the outermost arc in the tire diameter direction are preferably convex outward in the tire width direction.

[0030] As shown in FIG. 1, for the pneumatic tire, a straight line drawn so as to be in contact with the outer contours of the sidewall portion 2 and the bead portion 3 in the meridian cross section is defined as a tangent line L1, a point where the tangent line L1 and the outer contour of the sidewall portion 2 are in contact is defined as a contact point P1, a straight line passing through the winding end 4c of the carcass layer 4 and perpendicularly intersecting the main body portion 4a is defined as a perpendicular line L2, and a straight line passing through the contact point P1 and perpendicularly intersecting the main body portion 4a is defined as a perpendicular line L3. When this is done, the area A [mm 2 of the region (the hatched portion in the figure) surrounded by the outer contours of the sidewall portion 2 and the bead portion 3 and the tangent line L1, and the area S [mm of the region (the hatched portion of the figure) surrounded by the outer contours of the sidewall portion 2 and the bead portion 3, the main body portion 4a, the perpendicular line L2, and the perpendicular line L3 2The thickness G1 [mm] of the bead filler 6 measured along the perpendicular line L2 satisfies the relationship of 0.10×(G1 - 17) ≦ A / (S + A) ≦ 0.05×(G1 - 10).

[0031] By adopting such a structure, the pneumatic tire can maintain good durability of the bead part 3, which is a concern when a recess 20 is provided near the bead part 3 for weight reduction of the tire. That is, in the pneumatic tire, the recess 20 is arranged on the outer side in the tire radial direction with respect to the winding end 4c of the carcass layer 4 in the sidewall part 2 and on the inner side in the tire radial direction with respect to the tire maximum width position P. Since the area of the recess 20 (area A), the amount of rubber on the outer side in the radial direction than the winding end 4c (area S), and the thickness G1 of the bead filler 6 are set in the above - mentioned relationship, the thickness G1 of the bead filler 6 can be increased according to the ratio of the area of the recess 20, the distortion near the winding end 4c caused by providing the recess 20 can be dispersed, and the durability of the bead part 3 can be ensured well.

[0032] When the area A, the area S, and the thickness G1 of the bead filler 6 of the pneumatic tire satisfy the relationship of 0.10×(G1 - 17) < A / (S + A), a sufficient amount of rubber for dispersing distortion can be ensured, and the effect of improving the durability performance of the bead part 3 can be expected sufficiently. Also, when the area A, the area S, and the thickness G1 of the bead filler 6 of the pneumatic tire satisfy the relationship of A / (S + A) < 0.05×(G1 - 10), a sufficient area of the recess 20 can be ensured, and the effect of reducing the tire weight can be expected sufficiently. Further, in the pneumatic tire of the embodiment, it is preferable that the area A, the area S, and the thickness G1 of the bead filler 6 satisfy the relationship of 0.10×(G1 - 16) ≦ A / (S + A) ≦ 0.05×(G1 - 12). Note that the value of the ratio A / (S + A) is not particularly limited, but is preferably 0.05 to 0.25.

[0033] As shown in FIG. 3, for a pneumatic tire, when the point where the tangent line L1 contacts the outer contour of the bead portion 3 is defined as the contact point P2, a straight line L4 connecting the contact point P2 and a point P3 which is 10 [mm] away from the contact point P2 along the outer contours of the sidewall portion 2 and the bead portion 3 toward the outer side in the tire radial direction, it is preferable that the outer contours of the sidewall portion 2 and the bead portion 3 located between the contact point P2 and the point P3 are positioned on the outer side in the tire width direction. Thereby, for the pneumatic tire, the outer contour between the point P3 and the contact point P2 bulges outward in the tire width direction, and the shape (outer contour) of the recessed portion 20 is improved. Thus, it is possible to secure the amount of rubber near the turned-up end 4c, which is advantageous for improving the durability of the bead portion 3.

[0034] Furthermore, as shown in FIG. 3, for the pneumatic tire, a straight line L5 connecting the contact point P2 and a point P4 which is 15 [mm] away from the contact point P2 along the outer contours of the sidewall portion 2 and the bead portion 3 toward the outer side in the tire radial direction, it is preferable that the outer contours of the sidewall portion 2 and the bead portion 3 located between the contact point P2 and the point P4 are positioned on the outer side in the tire width direction. Thereby, for the outer contour between the point P4 and the contact point P2 of the pneumatic tire, it also bulges outward in the tire width direction, and the shape (outer contour) of the recessed portion 20 is improved. Thus, it is possible to secure the amount of rubber near the turned-up end 4c, which is advantageous for improving the durability of the bead portion 3.

[0035] As shown in Fig. 2, for a pneumatic tire, when the thickness of the bead filler 6 measured on a straight line passing through the contact point P2 where the tangent line L1 contacts the outer contour of the bead part 3 and perpendicular to the main body part 4a is G2 [mm], the ratio G2 / G1 of the thickness G2 to the thickness G1 is preferably in the range of 0.55 ≦ G2 / G1 ≦ 0.90, and more preferably in the range of 0.60 ≦ G2 / G1 ≦ 0.85. Thereby, the pneumatic tire can secure a volume of the bead filler 6 excellent in flex fatigue resistance and fracture characteristics, which is advantageous for improving the durability of the bead part 3. When G2 / G1 of the pneumatic tire is 0.55 or more, it is possible to avoid a shortage of the rubber amount and sufficiently suppress the strain near the turning-up end 4c, and a sufficient effect of improving the durability performance can be expected. Further, when G2 / G1 of the pneumatic tire is 0.90 or less, it is possible to avoid a shortage of the rubber amount in the sidewall part 2 and make it difficult to cause failures such as ozone cracks.

[0036] For a pneumatic tire, when the area of the region occupied by the bead filler 6 in the aforementioned area S is S1 [mm 2 , the ratio S1 / S of the area S1 to the area S preferably satisfies the relationship of 0.25 ≦ S1 / S ≦ 0.50, and more preferably satisfies the relationship of 0.30 ≦ S1 / S ≦ 0.45. Thereby, the pneumatic tire can secure a volume of the bead filler 6 excellent in flex fatigue resistance and fracture characteristics, which is advantageous for improving the durability of the bead part 3. When S1 / S of the pneumatic tire is 0.25 or more, it is possible to avoid a shortage of the rubber amount and sufficiently suppress the strain near the end of the carcass layer 4, and a sufficient effect of improving the durability performance can be expected. Further, when S1 / S of the pneumatic tire is 0.50 or less, it is possible to avoid a shortage of the rubber amount in the sidewall part 2 and make it difficult to cause failures such as ozone cracks.

[0037] As shown in Fig. 2, for a pneumatic tire, when the distance along the tire radial direction from the point on the tire radial direction innermost side of the bead part 3 (the tip of the bead toe) 3a to the winding-up end 4c is defined as H1, and the distance along the tire radial direction from the point on the tire radial direction innermost side of the bead part 3 (the tip of the bead toe) 3a to the contact point P2 is defined as H2, the ratio H2 / H1 of these is preferably 1.1 or more and 1.5 or less. Thereby, since the shape of each part in the bead part 3 becomes better, it is advantageous for improving the durability of the bead part 3.

[0038] In the pneumatic tire of the present embodiment, the bead filler 6 preferably has a two-layer structure composed of an upper bead filler 6a and a lower bead filler 6b. When such a two-layer structure bead filler 6 is used in the pneumatic tire, the elongation at break of the upper bead filler 6a is preferably 400 [%] or more, more preferably 450 [%] or more. By using a bead filler 6 with a high elongation at break in the pneumatic tire, breakage near the end of the carcass layer 4 due to repeated strain during rolling is suppressed, which is advantageous for improving the durability performance of the bead part 3. In the pneumatic tire of the embodiment, the upper limit of the elongation at break of the upper bead filler 6a is not particularly limited, but it is preferably 800 [%] or less, for example. Also, in the pneumatic tire of the embodiment, the range of the elongation at break of the lower bead filler 6b is not particularly limited, but it is preferably 50 [%] or more and 250 [%] or less, for example.

[0039] The elongation at break is a value [%] measured at room temperature (23 [°C]) in accordance with JIS K6251.

[0040] When using the two-layer bead filler 6 as described above in a pneumatic tire, the elastic modulus of the upper bead filler 6a at 60 °C is preferably 4.0 [MPa] or more and 8.0 [MPa] or less, more preferably 4.5 [MPa] or more and 7.5 [MPa] or less. Also, in the pneumatic tire, the elastic modulus of the lower bead filler 6b at 60 °C is preferably 14.0 [MPa] or more and 20.0 [MPa] or less, more preferably 15.0 [MPa] or more and 19.0 [MPa] or less. Thereby, in the pneumatic tire, the physical properties of the upper bead filler 6a and the lower bead filler 6b when the bead filler 6 has a two-layer structure are improved, which is advantageous for improving the durability performance of the bead portion 3. When the elastic moduli of the upper bead filler 6a and the lower bead filler 6b at 60 °C in the pneumatic tire are within the above ranges, the deformation of the bead portion 3 during load application becomes small, and the strain at the end of the carcass layer 4 also decreases, so that the effect of improving the durability performance is sufficiently expected. When the elastic moduli of the upper bead filler 6a and the lower bead filler 6b at 60 °C in the pneumatic tire are within the above ranges, the elongation at break of the bead filler 6 can be improved, and the effect of improving the durability performance is sufficiently expected.

[0041] The elastic modulus at 60 °C is a value [MPa] measured under the conditions of an initial strain of 10 [%], an amplitude of ±2 [%], a frequency of 20 [Hz], and 60 °C using a viscoelastic spectrometer in accordance with JIS K6394.

[0042] When using the two-layer bead filler 6 as described above in a pneumatic tire, the area S2 [mm 2 of the upper bead filler 6a and the area S3 [mm 2Preferably, the relationship of 0.30 ≦ S3 / S2 ≦ 0.80 is satisfied, more preferably, the relationship of 0.40 ≦ S3 / S2 ≦ 0.70 is satisfied. For the pneumatic tire, by providing the upper bead filler 6a and the lower bead filler 6b in a well-balanced manner as described above, it is advantageous for improving the durability performance of the bead portion 3. That is, when the pneumatic tire has a large elongation at break of the upper bead filler 6a, the area of the upper bead filler 6a is large, so that the strain near the end of the carcass layer 4 can be dispersed, and the durability performance of the bead portion 3 can be improved. On the other hand, when the pneumatic tire has a high elastic modulus of the lower bead filler 6b, the deformation of the entire bead portion 3 during load application is suppressed, and the durability performance of the bead portion 3 can be improved. By setting the area as described above, the pneumatic tire can achieve a good balance between the areas of the upper bead filler 6a and the lower bead filler 6b, effectively draw out the above-described effects, and comprehensively enhance the durability performance of the bead portion 3.

[0043] As shown in FIG. 3, when the shortest distance between the rolled-up end 4c measured on the perpendicular line L2 and the outer surface of the tire in the outer direction of the tire width direction is defined as G3, and the distance between the rolled-up end 4c measured on the extension line of the rolled-up portion 4b and the outer surface of the recess 20 is defined as G4, the distance G3 is preferably 7.0 [mm] or more and 14.0 [mm] or less, more preferably 8.0 [mm] or more and 13.0 [mm] or less, and the distance G4 is preferably 10.0 [mm] or more and 40.0 [mm] or less, more preferably 15.0 [mm] or more and 37.0 [mm] or less. Thereby, a sufficient distance from the rolled-up end 4c to the outer contour of the tire can be ensured, the strain between the rolled-up end 4c and the outer contour of the tire can be dispersed, which is advantageous for improving the durability of the bead portion 3. When the distances G3 and G4 are smaller than the above-described ranges, a sufficient amount of rubber cannot be ensured, the strain of the rolled-up end 4c cannot be sufficiently dispersed, and the effect of improving the durability cannot be sufficiently expected. When the distances G3 and G4 are larger than the above-described ranges, the effect of reducing the tire weight cannot be sufficiently expected.

[0044] In the pneumatic tire of the embodiment, the breaking elongation of the rubber constituting the sidewall rubber 12 is preferably 450 [%] or more, more preferably 500 [%] or more. Further, in the pneumatic tire, the elastic modulus of the rubber constituting the sidewall rubber 12 at 60 ° C is preferably 2.5 [MPa] or more and 5.5 [MPa] or less, more preferably 3.5 [MPa] or more and 5.0 [MPa] or less. Thus, the pneumatic tire can suppress the breakage near the turning-up end 4c due to the repeated strain during rolling by increasing the breaking elongation of the sidewall rubber 12, which is advantageous for improving the durability performance of the bead portion 3. Further, the pneumatic tire can compensate for the reduced rigidity of the sidewall portion 2 by providing the concave portion by increasing the elastic modulus of the sidewall rubber 12, which is advantageous for reducing the strain of the bead portion 3 and improving the durability. When the breaking elongation of the rubber constituting the sidewall rubber 12 of the pneumatic tire is 450 [%] or more, the breakage of the rubber in the peripheral portion of the carcass layer 4 due to the repeated strain during rolling can be suppressed, and the durability performance of the bead portion 3 can be sufficiently improved. Incidentally, the upper limit of the breaking elongation of the sidewall rubber 12 of the pneumatic tire is not particularly limited, but may be, for example, 800 [%] or less. When the elastic modulus of the rubber constituting the sidewall rubber 12 at 60 [° C] is 2.5 [MPa] or more, the rigidity of the sidewall portion 2 can be sufficiently ensured, and when it is 5.5 [MPa] or less, the breaking elongation of the sidewall rubber 12 can be maintained well, and the effect of improving the durability performance is sufficiently expected.

[0045] In the pneumatic tire of the embodiment, as shown in FIG. 3, the crack suppression rubber layer 14 can also be arranged so as to cover the turned-up end 4c of the carcass layer 4. The crack suppression rubber layer 14 is preferably arranged so as to be in contact with both the sidewall rubber 12 and the rim cushion rubber 13. Further, in the pneumatic tire of the embodiment, when providing the steel reinforcing layer 21 described later, it is preferably arranged so as to cover not only the turned-up end 4c of the carcass layer 4 but also the end portion of the steel reinforcing layer 21. Similarly, in the pneumatic tire of the embodiment, when providing the organic fiber reinforcing layer 22 described later, it is preferably arranged so as to cover not only the turned-up end 4c of the carcass layer 4 but also the end portion of the organic fiber reinforcing layer 22. When the pneumatic tire is provided with such a crack suppression rubber layer 14, its elongation at break is preferably set to 400 [%] or more, more preferably 450 [%] or more. By increasing the elongation at break of the crack suppression rubber layer 14 in this way, the pneumatic tire can suppress breakage near the turned-up end 4c due to repeated strain during rolling, which is advantageous for improving the durability of the bead portion. Note that the upper limit of the elongation at break of the crack suppression rubber layer 14 of the pneumatic tire is not particularly limited, but it is preferably 800 [%] or less, for example.

[0046] In the pneumatic tire of the embodiment, as shown in FIG. 2, the steel reinforcing layer 21 can also be arranged along the outer surfaces of the main body portion 4a and the turned-up portion 4b of the carcass layer 4. The steel reinforcing layer 21 is one in which a steel cord is coated with a coating rubber. When the pneumatic tire is provided with the steel reinforcing layer 21, it is preferable that the end portion 21a on the side of the turned-up portion 4b is separated from the position of the turned-up end 4c toward the inner side in the tire radial direction. The distance between the end portion 21a on the side of the turned-up portion 4b of the steel reinforcing layer 21 and the turned-up end 4c in the tire radial direction is preferably 5 [mm] or more and 25 [mm] or less, more preferably 7 [mm] or more and 20 [mm] or less. Further, for the steel reinforcing layer 21, it is preferable that the end portion 21b on the side of the main body portion 4a is separated from the position of the turned-up end 4c toward the outer side in the tire radial direction. The distance between the end portion 21b on the side of the main body portion 4a of the steel reinforcing layer 21 and the turned-up end 4c in the tire radial direction is preferably 5 [mm] or more and 25 [mm] or less, more preferably 7 [mm] or more and 20 [mm] or less. Thus, by providing the steel reinforcing layer 21 in the pneumatic tire and setting its arrangement as described above, the rigidity of the bead portion 3 can be improved, the deformation of the bead portion 3 due to deflection can be suppressed, which is advantageous for improving the durability performance of the bead portion 3.

[0047] In the pneumatic tire of the embodiment, as shown in FIG. 2, the organic fiber reinforcing layer 22 can also be disposed on the outer side in the tire width direction of the turned-up portion 4b of the carcass layer 4. The organic fiber reinforcing layer 22 is formed by coating organic fiber cords with coating rubber. In the pneumatic tire of the embodiment, when the above-described steel reinforcing layer 21 is provided, it is preferable to provide two layers of the organic fiber reinforcing layer 22 on the outer peripheral side (outer side in the tire width direction) on the turned-up portion 4b side of the steel reinforcing layer 21 as shown in the figure. When the pneumatic tire is provided with the organic fiber reinforcing layer 22, the outer end 22a in the tire radial direction is preferably located on the outer side in the tire radial direction than the turned-up end 4c, and the inner end 22b in the tire radial direction is preferably located on the inner side in the tire radial direction than the center 5a of the bead core 5. Further, it is preferable that the outer end 22a in the tire radial direction of the organic fiber reinforcing layer 22 is separated from the recess 20 by 6 [mm] or more. Thus, the pneumatic tire can suppress the deformation due to bending by providing the organic fiber reinforcing layer 22 and setting its arrangement as described above, and is advantageous for suppressing the strain near the turned-up end 4c of the carcass layer 4 and improving the durability performance.

[0048] As shown in FIG. 1, the configuration of the belt layer 7 of the pneumatic tire of the embodiment is defined. Hereinafter, the details of the belt layer 7 will be described.

[0049] The belt layer 7 has a three-ply structure as described above. Therefore, the pneumatic tire can achieve weight reduction on the outer side in the tire radial direction including the tread portion 1 where the belt layer 7 is disposed. Moreover, the pneumatic tire can achieve weight reduction on the inner side in the tire radial direction where the bead portion 3 is disposed in the casing extending from the carcass layer 4 to the bead portion 3 by providing the above-described recess 20. Therefore, the pneumatic tire can improve the handling stability performance because the weight balance between the outer side and the inner side in the tire radial direction is balanced.

[0050] Further, in a no-load state where the belt layer 7 is mounted on a specified rim and filled with a specified internal pressure, the width W2 in the tire width direction of the second belt 72 from the inner side in the tire radial direction is formed in a range of 85[%] ≦ W2 / Wp ≦ 95[%] with respect to the cross-sectional width Wp of the carcass layer 4. The cross-sectional width Wp of the carcass layer 4 is the largest cross-sectional dimension in the tire width direction of the carcass cords excluding the coat rubber of the carcass layer 4, and is the dimension between both outermost sides in the tire width direction of the carcass cords. By setting the width W2 of the second belt 72 of the belt layer 7 within the above range with respect to the cross-sectional width Wp of the carcass layer 4, this pneumatic tire can sufficiently expect the effects of weight reduction and further improvement of handling stability performance, and can contribute to the groove crack resistance performance by protecting the inner side in the tire radial direction of the circumferential main groove 1b. Further, for the belt layer 7, it is preferable that the width W2 of the second belt 72 is set to 89[%] ≦ W2 / Wp ≦ 95[%] or less with respect to the cross-sectional width Wp of the carcass layer 4.

[0051] Further, in a no-load state where the belt layer 7 is mounted on a specified rim and filled with a specified internal pressure, the width W3 in the tire width direction of the third belt 73 from the inner side in the tire radial direction and the width W2 in the tire width direction of the second belt 72 satisfy the relationship of 10[mm] ≦ W2 - W3 ≦ 30[mm], and preferably satisfy the relationship of 15[mm] ≦ W2 - W3 ≦ 25[mm]. Further, in a no-load state where the belt layer 7 is mounted on a specified rim and filled with a specified internal pressure, the width W1 in the tire width direction of the first belt 71 from the inner side in the tire radial direction and the width W2 in the tire width direction of the second belt 72 satisfy the relationship of -35[mm] ≦ W2 - W1 ≦ -15[mm], and preferably satisfy the relationship of -30[mm] ≦ W2 - W1 ≦ -20[mm]. By setting the widths W3 and W1 of the first and third belts 71 and 73 with respect to the width W2 of the second belt 72 within the above range in the three-layer belt layer 7, this pneumatic tire can sufficiently expect the effects of weight reduction and further improvement of handling stability performance, and can contribute more to the groove crack resistance performance.

[0052] Further, for the belt layer 7, the belt cords of at least two belts are in the range of 12° or more and 24° or less in absolute value with respect to the tire circumferential direction. In the pneumatic tire of the embodiment, among the three belt layers 7, it is preferable that the belt cords of the first belt 71 and the second belt 72, which are cross belts, are at an angle within the above range. Also, in the pneumatic tire of the embodiment, among the three belt layers 7, it is preferable that the belt cords of the first belt 71 and the second belt 72, which are cross belts, are in the range of 14° or more and 22° or less in absolute value. In addition, in the pneumatic tire of the embodiment, it is preferable that the belt cord of the third belt 73 is in the range of 14° or more and 22° or less in absolute value. By setting the angle of the belt cord of at least the second belt with respect to the tire circumferential direction within the above range in the three-layer belt layer 7 of the pneumatic tire, the effect of further improving the handling stability performance can be sufficiently expected, and the effect of improving the durability performance by suppressing the diameter growth can be expected.

[0053] Also, in the unloaded state where the belt layer 7 is mounted on a specified rim and filled with a specified internal pressure, the width W2 of the second belt 72 is formed in the range of 70% ≤ W2 / Wr ≤ 105% with respect to the specified rim width Wr. In the pneumatic tire of the embodiment, it is preferable that the width W2 of the second belt 72 is in the range of 85% ≤ W2 / Wr ≤ 105% with respect to the specified rim width Wr. By setting the width W2 of the second belt 72 within the above range with respect to the specified rim width Wr, the pneumatic tire can sufficiently expect the effect of further improving the handling stability performance and can contribute to the groove crack resistance performance.

[0054] Incidentally, in this embodiment, as described above, a pneumatic tire has been described as an example of the tire. This pneumatic tire can be filled with air, an inert gas such as nitrogen, and other gases. However, the characteristic configuration of the pneumatic tire described in this embodiment can be arbitrarily applied to other tires within the scope obvious to those skilled in the art. Examples of other tires include airless tires and solid tires.

Example

[0055] Figures 4 and 5 are charts showing the results of the performance tests of the pneumatic tire according to the embodiment. Hereinafter, a performance evaluation test conducted on a conventional pneumatic tire, a comparative example pneumatic tire, and an example pneumatic tire according to the embodiment will be described. The performance evaluation test was conducted on the tire weight and handling stability performance.

[0056] For the tire weight, the mass of a pneumatic tire of tire size 11R22.5 was measured in a non-rim assembled state and indexed. This evaluation was performed by an index evaluation with the conventional example as a reference (100), and the smaller the numerical value, the lighter the tire weight, indicating that the tire has been weight-reduced.

[0057] For the evaluation test of the handling stability performance, a pneumatic tire of the above tire size was mounted on a test vehicle (), and a sensory evaluation was performed on the ride comfort performance and the wandering performance on a dry road surface and indexed. This evaluation was performed by an index evaluation with the conventional example as a reference (100), and the larger the numerical value, the higher the handling stability performance.

[0058] The conventional pneumatic tire mainly has a four-ply belt layer structure and no recesses.

[0059] The comparative example pneumatic tire mainly has a three-ply belt layer structure but no recesses.

[0060] The example pneumatic tire mainly has a three-ply belt layer structure with recesses.

[0061] And as shown in the test results, it can be seen that the pneumatic tire of this example has improved tire weight (weight reduction) and handling stability performance compared with the conventional example.

[0062] This disclosure includes the following inventions. [Invention 1] A tread portion, A pair of sidewall portions disposed on both sides of the tread rubber, A pair of bead portions disposed on the inner side in the tire diameter direction of each of the sidewall portions; At least one carcass layer spanned between the pair of bead portions; A belt layer disposed in a three-sheet structure on the outer side in the tire diameter direction of the carcass layer; and including In a non-loaded state where the tire is mounted on a specified rim and filled with a specified internal pressure, the width W2 in the tire width direction of the second belt from the inner side in the tire diameter direction is formed in a range of 85[%] ≦ W2 / Wp ≦ 95[%] with respect to the cross-sectional width Wp of the carcass layer; Each of the bead portions has a bead core and a bead filler disposed on the outer side in the tire diameter direction of the bead core; The carcass layer has a main body portion wound from the inner side to the outer side of the tire around the bead core and the bead filler and located between the pair of bead portions, and a wound-up portion wound on the outer side in the tire width direction of the bead core and the bead filler; When the width between the pair of bead portions in the non-rim assembled state is set to the specified rim width, A recess is provided on the outer surface of the tire on the outer side in the tire diameter direction of the wound-up end of the carcass layer of at least one of the sidewall portions and on the inner side in the tire diameter direction of the maximum tire width position, which is continuous in the tire circumferential direction and the contour line in the meridian cross-section is composed of a plurality of arcs with different radii of curvature; When a straight line drawn so as to be in contact with the outer contours of the sidewall portion and the bead portion in the meridian cross-section is defined as a tangent line L1, a point where the tangent line L1 and the outer contour of the sidewall portion are in contact is defined as a contact point P1, a straight line passing through the wound-up end of the carcass layer and perpendicularly intersecting the main body portion is defined as a perpendicular line L2, and a straight line passing through the contact point P1 and perpendicularly intersecting the main body portion is defined as a perpendicular line L3, The area A [mm 2 of the region surrounded by the outer contours of the sidewall portion and the bead portion and the tangent line L1, and the area S [mm 2and the thickness G1 [mm] of the bead filler measured along the perpendicular line L2 satisfies the relationship of 0.10×(G1 - 17) ≦ A / (S + A) ≦ 0.05×(G1 - 10). Tire. [Invention 2] In the belt layer, the width W3 in the tire width direction of the third belt from the inner side in the tire radial direction and the width W2 in the tire width direction of the second belt satisfy the relationship of 10 [mm] ≦ W2 - W3 ≦ 30 [mm], and the width W1 in the tire width direction of the first belt from the inner side in the tire radial direction and the width W2 in the tire width direction of the second belt satisfy the relationship of -35 [mm] ≦ W2 - W1 ≦ -15 [mm]. The tire according to Invention 1. [Invention 3] In the belt layer, the belt cords of at least two belts are in the range of 12 [deg] or more and 24 [deg] or less in absolute value with respect to the tire circumferential direction. The tire according to Invention 1 or 2. [Invention 4] In the belt layer, in the unloaded state where it is mounted on a specified rim and filled with a specified internal pressure, the width W2 of the second belt is formed in the range of 70 [%] ≦ W2 / Wr ≦ 105 [%] with respect to the specified rim width Wr. The tire according to any one of Inventions 1 to 3.

Explanation of Signs

[0063] 1 Tread portion 2 Sidewall portion 3 Bead portion 4 Carcass layer 4a Body portion 4b Turn-up portion 4c Turn-up end 5 Bead core 6 Bead filler 7 Belt layer 71, 72, 73 Belts

Claims

1. A tread portion, A pair of sidewall portions disposed on both sides of the tread portion, A pair of bead portions disposed on the inner side in the tire diameter direction of each sidewall portion, At least one carcass layer spanned between the pair of bead portions, A belt layer disposed in a three-sheet structure on the outer side in the tire diameter direction of the carcass layer, Including, In a no-load state where the tire is mounted on a specified rim and filled with a specified internal pressure, the width W2 in the tire width direction of the second belt from the inner side in the tire diameter direction is 85 [%] ≤ W2 / Wp ≤ 95 [%] with respect to the cross-sectional width Wp of the carcass layer. It is formed in the following range, Each of the bead portions has a bead core and a bead filler disposed on the outer side in the tire diameter direction of the bead core, The carcass layer has a main body portion that is wound from the inner side to the outer side of the tire around the bead core and the bead filler and is located between the pair of bead portions, and a wound-up portion that is wound up on the outer side in the tire width direction of the bead core and the bead filler. It has, When the width between the pair of bead portions in the non-rim assembled state is set to the specified rim width, On the outer surface of the tire that is radially outside the winding end of the carcass layer of at least one of the sidewall portions and radially inside the maximum tire width position, there is a concave portion that is continuous in the tire circumferential direction and whose contour line in the meridian cross-section is composed of a plurality of arcs with different radii of curvature. It has, When a straight line drawn so as to be in contact with the outer contours of the sidewall portion and the bead portion in the meridian cross-section is defined as a tangent line L1, a point where the tangent line L1 and the outer contour of the sidewall portion are in contact is defined as a contact point P1, a straight line passing through the winding end of the carcass layer and perpendicular to the main body portion is defined as a perpendicular line L2, and a straight line passing through the contact point P1 and perpendicular to the main body portion is defined as a perpendicular line L3, The area A [mm ２ of the region surrounded by the outer contour of the sidewall portion and the bead portion and the tangent line L1, the area S [mm ２ of the region surrounded by the outer contour of the sidewall portion and the bead portion, the main body portion, the perpendicular line L2, and the perpendicular line L3, and the thickness G1 [mm] of the bead filler measured along the perpendicular line L2 satisfy the relationship of 0.10×(G1−17)≦A / (S + A)≦0.05×(G1−10). Tire.

2. In the belt layer, the width W3 in the tire width direction of the third belt from the inner side in the tire diameter direction and the width W2 in the tire width direction of the second belt satisfy the relationship of 10 [mm] ≤ W2 - W3 ≤ 30 [mm], and the width W1 in the tire width direction of the first belt from the inner side in the tire diameter direction and the width W2 in the tire width direction of the second belt satisfy the relationship of -35 [mm] ≤ W2 - W1 ≤ -15 [mm]. The tire according to Claim 1. The tire according to claim 1.

3. The belt layer is such that the belt cords of at least two belts are in the range of 12 [deg] or more and 24 [deg] or less in absolute value with respect to the tire circumferential direction. The tire according to claim 1.

4. In the unloaded state where the belt layer is mounted on a specified rim and filled with a specified internal pressure, the width W2 of the second belt is formed in the range of 70 [%] ≤ W2 / Wr ≤ 105 [%] with respect to the specified rim width Wr. The tire according to claim 1.

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