Pneumatic tire

Abstract

To provide a pneumatic tire which is excellent in durability of a bead filler and resistance to external damage of a side wall.SOLUTION: A carcass 4 has a first ply 41 laminated at the relatively inner side in the tire radial direction on a tread 3, and a second ply 42 laminated at the relatively outer side in the tire radial direction on the tread 3. Each of a wind-up end 41e of the first ply and a wind-up end 42e of the second ply is arranged at the outer side in the tire radial direction of the outer end in the tire radial direction of a bead filler 1b with a gap of 80% or more of the length in the tire radial direction of a bead filler 1b. One of the wind-up end 41e of the first ply and the wind-up end 42e of the second ply is arranged at a position overlapping a raised part 7 provided in a buttress region 2B of a side wall 2, and the tire width direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a pneumatic tire having a raised portion provided in a buttress-free area of a sidewall.

Background Art

[0002] For the purpose of improving the running performance on rough roads such as muddy roads and rocky fields, a pneumatic tire having a raised portion provided in a buttress-free area of a sidewall is known. In such a tire, since a traction effect due to shear resistance can be obtained when running on a rough road, the rough road wear resistance is improved. Furthermore, since an effect of protecting against external injury factors such as curbs and sharp corners of rock surfaces by distancing them from the outer surface of the sidewall (protection effect) can be obtained, the impact resistance of the sidewall (hereinafter sometimes simply referred to as "impact resistance") is improved.

[0003] However, since the raised portion provided in the buttress-free area involves a local thickness change of the sidewall, it has a portion where strain is likely to concentrate. Therefore, when the positional relationship with other tire components such as a bead filler is not appropriate, there is a risk that the durability may decrease due to the occurrence of cracks caused by the concentration of strain. For example, in the pneumatic tire described in Patent Document 1, since the bead filler and the raised portion are relatively close to each other, it is considered that the durability of the bead filler may decrease due to the concentration of strain.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire excellent in the durability of a bead filler and the impact resistance of a sidewall.

Means for Solving the Problem

[0006] The pneumatic tire of the present disclosure is a pair of bead parts, a pair of sidewalls extending radially outward of the tire from each of the pair of bead parts, a tread continuous with the radially outer ends of each of the pair of sidewalls in the tire radial direction, a bead filler embedded in the bead part, a raised portion provided in at least one buttless region of the pair of sidewalls, and a carcass wound upward from the inner side to the outer side in the tire width direction so as to sandwich the bead filler, and includes the carcass has a first ply laminated relatively radially inward in the tread and a second ply laminated relatively radially outward in the tread, the winding-up ends of the first ply and the winding-up ends of the second ply are each disposed radially outward of the radially outer end of the bead filler via a distance of 80% or more of the radial length of the bead filler in the tire radial direction, the winding-up ends of the first ply and the winding-up ends of the second ply are each disposed at positions overlapping the raised portion in the tire width direction.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0008] An embodiment of the pneumatic tire of the present disclosure will be described with reference to the drawings.

[0009] The pneumatic tire T shown in FIGS. 1 and 2 is a pneumatic radial tire intended for running on rough roads including muddy areas and rocky terrains. The pneumatic tire T includes a pair of bead portions 1, a pair of sidewalls 2 extending radially outward of the tire diameter from each of the pair of bead portions 1, and a tread 3 continuous with the radially outer ends of each of the pair of sidewalls 2 in the tire diameter direction. Further, the pneumatic tire T includes a bead filler 1b embedded in the bead portion 1, a raised portion 7 provided in at least one buttress region 2B of the pair of sidewalls 2, and a carcass 4 wound upward from the inner side to the outer side in the tire width direction so as to sandwich the bead filler 1b.

[0010] Here, the tire diameter direction is the direction along the diameter of the tire T and corresponds to the vertical direction in the drawings. In FIGS. 1 and 2, the upper side is the radially outer side of the tire, and the lower side is the radially inner side of the tire. The tire width direction is the direction parallel to the rotation axis of the tire T and corresponds to the left-right direction in the drawings. The side approaching the tire equatorial plane TE (the left side in FIG. 2) is the inner side in the tire width direction, and the side away from the tire equatorial plane TE (the right side in FIG. 2) is the outer side in the tire width direction. The tire circumferential direction is the direction around the rotation axis of the tire T.

[0011] An annular bead core 1a is embedded in the bead portion 1. The bead core 1a is formed by covering a convergent body such as a steel wire with rubber. The bead filler 1b is disposed radially outward of the bead core 1a in the tire diameter direction. The bead filler 1b is formed of rubber having a triangular cross section extending radially outward from the bead core 1a. A rim strip rubber 11 forming the outer surface of the bead portion 1 is provided on the radially outer side of the bead filler 1b in the tire width direction. A sidewall rubber 12 forming the outer surface of the sidewall 2 is provided on the radially outer side of the rim strip rubber 11.

[0012] The carcass 4 forms a toroidal shape between a pair of bead portions 1, and its ends are wound up (i.e., turned up) so as to sandwich the bead core 1a and the bead filler 1b. In other words, the carcass 4 is provided with a series of turned-up portions arranged on the outer side in the tire width direction of the bead core 1a and the bead filler 1b on the main body portion extending from the tread 3 through the sidewall 2 to the bead portion 1. On the inner peripheral side of the carcass 4, an inner liner 14 having an excellent function of preventing gas permeation is provided to hold the air pressure.

[0013] The carcass 4 has a plurality of plies (carcass plies) laminated on each other. In the present embodiment, the carcass 4 has a first ply 41 laminated relatively on the inner side in the tire radial direction in the tread 3 and a second ply 42 laminated relatively on the outer side in the tire radial direction in the tread 3. The first ply 41 and the second ply 42 are each formed by covering a plurality of cords arranged in a direction substantially orthogonal to the tire circumferential direction with rubber. As the material of this cord, metals such as steel and organic fibers such as polyester, rayon, nylon, and aramid are preferably used.

[0014] In the tread 3, a belt layer 5 laminated on the outer side in the tire radial direction of the carcass 4 and a belt reinforcing layer 6 laminated on the outer side in the tire radial direction of the belt layer 5 are embedded. The belt layer 5 has a plurality of plies (belt plies) laminated on each other. The belt ply is formed by covering a plurality of cords arranged in a direction inclined with respect to the tire circumferential direction with rubber. As the material of this cord, steel is preferably used. In the present embodiment, the belt layer 5 is composed of two plies 51, 52, and the cords cross each other in opposite directions between the plies.

[0015] The belt reinforcement layer 6 has one or more plies (reinforcing plies). The reinforcing ply is formed by covering a cord extending substantially in the tire circumferential direction with rubber. As the material of this cord, the above-described organic fiber is preferably used. By covering the end portion of the belt layer 5 with the belt reinforcement layer 6, it is possible to suppress the lifting of the belt ply during high-speed running and improve the high-speed durability. On the outer side in the tire radial direction of the belt reinforcement layer 6, a tread rubber 13 forming the outer surface of the tread 3 is provided. Although not shown, the tread rubber 13 is provided with various grooves such as circumferential grooves and lug grooves constituting the tread pattern.

[0016] The pneumatic tire T of the present embodiment is not a so-called side support type run-flat tire, and a side reinforcing rubber layer having a crescent cross-sectional shape is not provided on the sidewall 2. However, the present invention is not limited to this, and the tire T may be a side support type run-flat tire provided with a side reinforcing rubber layer on the sidewall 2.

[0017] As described above, the raised portion 7 is provided in the buttressless region 2B of the sidewall 2. The buttressless region 2B is a region on the outer side in the tire radial direction of the sidewall 2, more specifically, a region on the outer side in the tire radial direction than the tire maximum width position 2M, and is a portion that does not come into contact with the ground during normal running on a flat paved road. On a soft road such as a muddy ground or a sand field, the tire sinks due to the weight of the vehicle, so that the buttressless region 2B comes into contact with the ground pseudo-statically, and a traction effect due to the shearing resistance of the raised portion 7 can be obtained. The tire maximum width position 2M is the position where the profile line 2p of the sidewall 2 in the tire meridian cross-section is farthest from the tire equatorial plane TE in the tire width direction.

[0018] The raised portion 7 protrudes from the profile line 2p of the sidewall 2. The profile line 2p is the contour of the sidewall 2 excluding protrusions such as rim protectors. In FIGS. 1 and 2, a part of the profile line 2p is shown by a dashed line. The profile line 2p is formed by a series of arcs that smoothly connect a plurality of arcs with different radii of curvature. The profile line 2p may be formed by a single arc, the radius of curvature may change continuously, or it may include a straight line in part. A plurality of raised portions 7 are arranged on the sidewall 2 at intervals in the tire circumferential direction. The tire meridian cross-section shown in FIGS. 1 and 2 longitudinally cuts one of the plurality of raised portions 7.

[0019] The raised portion 7 extends along the tire radial direction. In the present embodiment, the length of the raised portion 7 in the tire radial direction is larger than the length of the raised portion 7 in the tire circumferential direction. An inclined surface 71 that gradually reduces the raised height toward the outside in the tire radial direction is formed at the outer end of the raised portion 7 in the tire radial direction. An inclined surface 72 that gradually reduces the raised height toward the inside in the tire radial direction is formed at the inner end of the raised portion 7 in the tire radial direction. The inner end of the raised portion 7 in the tire radial direction (the boundary between the profile line 2p and the inclined surface 72) is located outside the tire maximum width position 2M in the tire radial direction. The tire meridian cross-section of the raised portion 7 includes a pair of inclined surfaces 71 and 72 rising from the profile line 2p and a top surface 73 connecting them. The top surface 73 has a step 73s for changing the raised height. The raised height is obtained as the height in the tire width direction with respect to the profile line 2p.

[0020] In the buttless region 2B, an annular rib 8 is provided that extends annularly along the tire circumferential direction across the raised portion 7. Similar to the raised portion 7, the annular rib 8 protrudes from the profile line 2p of the sidewall 2. In the present embodiment, the annular rib 8 has a top portion that protrudes outward in the tire width direction from the top surface 73 of the raised portion 7. However, it is not limited thereto, and the annular rib 8 may be formed flush with the raised portion 7. The raised height at the step 73s of the top surface 73 is greater than the raised height of the annular rib 8. Note that the shapes of the raised portion 7 and the annular rib 8 are not particularly limited.

[0021] As shown in FIG. 3, it is preferable that the top portion of the annular rib 8 is formed at the mold parting position Ps, which is the boundary between the tread mold 30 for molding the tread 3 and the side mold 20 for molding the sidewall 2. The mold parting position Ps may sometimes be identified from the parting line formed on the outer surface of the buttless region 2B. In the tire meridian cross section, the annular rib 8 has a stratovolcano shape in which the slope gently curves and constricts. However, it is not limited to this, and other shapes such as a rectangular shape, a trapezoidal shape, or a triangular shape may be adopted.

[0022] The top portion of the annular rib 8 is set, for example, at a position where the distance Da shown in FIG. 1 is in the range of 20 to 40 mm. The distance Da is obtained as the tire radial direction distance from the outermost diameter position of the tire T to the top portion of the annular rib 8. Further, the top portion of the annular rib 8 is set, for example, at a position where the distance Db shown in FIG. 1 is 75% or more of the tire cross-sectional half-width HW. The distance Db is obtained as the tire width direction distance from the tire equatorial plane TE to the top portion of the annular rib 8. The tire cross-sectional half-width HW is obtained as the tire width direction distance from the tire equatorial plane TE to the tire maximum width position 2M.

[0023] The winding-up ends 41e of the first ply 41 and the winding-up ends 42e of the second ply 42 are each disposed radially outside the radially outer end of the bead filler 1b through a distance of 80% or more of the tire radial length L1b of the bead filler 1b. Accordingly, the tire radial distances D41e from the radially outer end of the bead filler 1b to the winding-up ends 41e and D42e from the radially outer end of the bead filler 1b to the winding-up ends 42e are both 80% or more of the tire radial length L1b.

[0024] Also, the winding-up ends 41e of the first ply 41 and the winding-up ends 42e of the second ply 42 are each disposed at a position overlapping the raised portion 7 in the tire width direction. That is, the winding-up ends 41e, 42e are both disposed within the projection area A7 of the raised portion 7 toward the inner side in the tire width direction. Since the winding-up ends 41e, 42e appropriately separated from the bead filler 1b are disposed overlapping the raised portion 7, a space between the bead filler 1b and the raised portion 7 is ensured, and the bead filler 1b has excellent durability. Moreover, by disposing the winding-up ends 41e, 42e within the projection area A7 of the raised portion 7, the rigidity of the raised portion 7 is increased, and the sidewall 2 also has excellent cut resistance.

[0025] From the viewpoint of enhancing the above improvement effect, the tire radial distances D41e, D42e are preferably 90% or more, more preferably 100% or more, of the tire radial length L1b respectively. In arranging the winding-up end 42e disposed relatively closer to the inner side in the tire radial direction among the winding-up ends 41e, 42e at an appropriate height, the tire radial distance D42e is preferably 120% or less of the tire radial length L1b. From the viewpoint of appropriately separating the raised portion 7 from the bead filler 1b, the tire radial distance D7 from the radially outer end of the bead filler 1b to the radially inner end (the boundary between the top surface 73 and the inclined surface 72) of the top surface 73 of the raised portion 7 is preferably 100% or more of the tire radial length L1b.

[0026] In this embodiment, the winding end 41e of the first ply 41 is disposed radially outward of the tire diameter than the winding end 42e of the second ply 42. As a result, since the winding end 42e is covered from the outside in the tire width direction by the first ply 41, it is possible to effectively improve the durability by suppressing the generation of cracks starting from the winding end 42e. However, the present invention is not limited to this, and the winding end 41e may be disposed radially inward of the tire diameter than the winding end 42e.

[0027] In this embodiment, the winding end 41e of the first ply 41 and the winding end 42e of the second ply 42 are each disposed radially inward of the tire diameter than the mold cut position Ps. In the sidewall 2, in the region radially outward of the tire diameter than the mold cut position Ps, the bending during load application tends to be large. Therefore, by disposing each of the winding ends 41e and 42e radially inward of the tire diameter than the mold cut position Ps, it is possible to more appropriately suppress the concentration of strain at the winding ends 41e and 42e and improve the durability.

[0028] Since the winding ends 41e and 42e are both locations where strain tends to concentrate, it is beneficial for improving durability to keep these appropriately separated from each other. From such a viewpoint, it is preferable that a distance of 15 mm or more is provided in the tire diameter direction between the winding end 41e of the first ply 41 and the winding end 42e of the second ply 42. That is, the distance Dc in the tire diameter direction between the winding end 41e and the winding end 42e is preferably 15 mm or more.

[0029] In this embodiment, the winding end 41e of the first ply 41 and the winding end 42e of the second ply 42 are each disposed at a position that does not overlap with the inclined surface 72 in the tire width direction. That is, the winding ends 41e and 42e are both disposed outside the projection area A72 of the inclined surface 72 in the tire width direction. The projection area A72 of the inclined surface 72 tends to be a region where strain relatively easily concentrates within the projection area A7 of the raised portion 7. Therefore, according to such a configuration, it is possible to more appropriately suppress the concentration of strain at the winding ends 41e and 42e and improve the durability.

[0030] In this embodiment, the height of the raised portion 7 is relatively small in the region between the inclined surface 71 and the step 73s, and is relatively large in the region between the step 73s and the inclined surface 72. According to such a configuration, since the portion where the height of the raised portion 7 is relatively large is provided near the tire maximum width position 2M, it contributes to the improvement of puncture resistance. Further, the winding-up ends 41e of the first ply 41 and the winding-up ends 42e of the second ply 42 are respectively arranged at positions overlapping with the region between the step 73s and the inclined surface 72 in the tire width direction. Thereby, since the winding-up ends 41e and 42e are arranged in the region where the height of the raised portion is relatively large, the distortion generated in them can be suppressed and the durability can be improved.

[0031] The maximum raised height position 7M is the position that is the most radially outward in the tire in the portion where the height of the raised portion 7 is the largest (that is, the top surface 73 is the farthest from the profile line 2p in the tire width direction). In this embodiment, the maximum raised height position 7M is set at the radially outer end of the step 73 in the tire width direction. The height of the raised portion 7 gradually decreases from the maximum raised height position 7M toward the radially inner side of the tire. In this way, since the height of the raised portion is increased at the radially outer portion of the tire where it is easy to contact the puncture factor in the region between the step 73s and the inclined surface 72, it contributes to the improvement of puncture resistance. However, it is not limited to this. For example, it may have a shape that extends with a constant raised height from the maximum raised height position 7M toward the radially inner side of the tire and then continues to the inclined surface 72.

[0032] The maximum raised height position 7M is arranged radially inner of the mold cut position Ps. As described above, in the region radially outer of the mold cut position Ps, the bending during load application tends to be large. Since the maximum raised height position 7M tends to have relatively concentrated strain among the raised portions 7, it is preferably sufficiently separated from the mold cut position Ps. From such a viewpoint, the radial distance Dd between the mold cut position Ps and the maximum raised height position 7M is preferably 50% or more, and more preferably 70% or more of the radial distance De between the maximum raised height position 7M and the inclined surface 72.

[0033] The winding-up ends 41e and 42e are both arranged on the inner side in the tire diameter direction with respect to the maximum bulge height position 7M. Also, when considering the outer region Xa in the tire diameter direction and the remaining inner region Xb in the tire diameter direction when bisecting the region from the maximum bulge height position 7M to the inclined surface 72, it is preferable that the winding-up end 41e, which is relatively positioned on the outer side in the tire diameter direction, is arranged within the region Xa, and the winding-up end 42e, which is relatively positioned on the inner side in the tire diameter direction, is arranged within the region Xb. Thereby, the winding-up end 41e is arranged in a region where the bulge height is relatively large, and since the winding-up end 42e is covered by the first ply 41, the distortion generated in them can be suppressed and the durability can be improved.

[0034] The positional relationships such as those of the bead filler 1b, the bulge portion 7, and the winding-up ends 41e and 42e described so far only need to be applied to at least one of the pair of sidewalls 2. However, in order to enhance the improvement effect, it is preferable that they are applied to both of the pair of sidewalls 2. In the present embodiment, the positional relationships of the respective members shown in FIG. 2 are also applied to the sidewall 2 on the left side in FIG. 1.

[0035] The shapes, dimensions, etc. described in this specification are based on the normal state of no load in which the tire is mounted on a normal rim and filled with the normal internal pressure, unless otherwise specified. The normal rim is the rim defined for each tire in the standard system including the standard on which the tire is based. For example, it is the "Standard Rim" in JATMA, the "Design Rim" in TRA, or the "Measuring Rim" in ETRTO. The normal internal pressure is the air pressure defined for each tire in the standard system including the standard on which the tire is based. It is the "Maximum Air Pressure" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, or the "INFLATION PRESSURE" in ETRTO.

[0036] As described above, the pneumatic tire T of the present embodiment includes a pair of bead portions 1, a pair of sidewalls 2 extending radially outward in the tire diameter direction from each of the pair of bead portions 1, a tread 3 connected to the radially outer ends of each of the pair of sidewalls 2 in the tire diameter direction, a bead filler 1b embedded in the bead portion 1, a raised portion 7 provided in at least one buttress region 2B of the pair of sidewalls 2, and a carcass 4 wound upward from the inner side to the outer side in the tire width direction so as to sandwich the bead filler 1b. The carcass 4 has a first ply 41 laminated relatively radially inward in the tread 3 and a second ply 42 laminated relatively radially outward in the tread 3. The winding ends 41e of the first ply 41 and the winding ends 42e of the second ply 42 are each disposed radially outward of the radially outer end of the bead filler 1b via a distance of 80% or more of the radial length L1b of the bead filler 1b in the tire diameter direction, and the winding ends 41e of the first ply 41 and the winding ends 42e of the second ply 42 are each disposed at a position overlapping the raised portion 7 in the tire width direction.

[0037] According to such a configuration, since the intervals between the bead filler 1b and the winding ends 41e, 42e and between the bead filler 1b and the raised portion 7 are appropriately ensured, the bead filler 1b has excellent durability. Moreover, since the winding ends 41e, 42e are disposed at positions overlapping the raised portion 7 in the tire width direction, the rigidity of the raised portion 7 is increased, so that the sidewall 2 has excellent resistance to external damage.

[0038] It is preferable that the winding end 41e of the first ply 41 is disposed radially outward of the winding end 42e of the second ply 42 in the tire diameter direction. According to such a configuration, since the winding end 42e of the second ply 42 is covered from the outer side in the tire width direction by the first ply 41, the generation of cracks starting from the winding end 42e can be suppressed, and the durability can be effectively improved.

[0039] The winding-up ends 41e of the first ply 41 and the winding-up ends 42e of the second ply 42 are each preferably arranged on the inner side in the tire diameter direction with respect to the mold parting position Ps. According to such a configuration, the concentration of strain at the winding-up ends 41e, 42e can be more appropriately suppressed, and the durability can be enhanced.

[0040] It is preferable that an interval of 15 mm or more is provided in the tire diameter direction between the winding-up end 41e of the first ply 41 and the winding-up end 42e of the second ply 42. According to such a configuration, since the winding-up ends 41e, 42e are arranged at an appropriate distance from each other, the concentration of strain at the winding-up ends 41e, 42e can be more appropriately suppressed, and the durability can be enhanced.

[0041] An inclined surface 72 for gradually reducing the bulge height toward the inner side in the tire diameter direction is formed at the inner end in the tire diameter direction of the bulge 7, and the winding-up end 41e of the first ply 41 and the winding-up end 42e of the second ply 42 are each preferably arranged at a position not overlapping with the inclined surface 72 in the tire width direction. According to such a configuration, the concentration of strain at the winding-up ends 41e, 42e can be more appropriately suppressed, and the durability can be enhanced.

[0042] The pneumatic tire of the present disclosure can be adopted as various tires such as passenger cars, light trucks, trucks, and buses.

[0043] The pneumatic tire of the present disclosure is not limited to the above-described embodiments at all, and various improvements and modifications are possible without departing from the spirit thereof.

Description of Reference Numerals

[0044] 1 Bead portion 1b Bead filler 2 Sidewall 2B Battless region 3 Tread 4 Carcass 7 Bulge 41 First ply 41e Winding-up end of the first ply 42 Second ply 42e Hoisting end of the second ply 72 Inclined surface Ps Mold parting position

Claims

1. A pair of bead portions, A pair of sidewalls extending radially outward in the tire diameter direction from each of the pair of bead portions, A tread continuous with the radially outer ends in the tire diameter direction of each of the pair of sidewalls, A bead filler embedded in the bead portion, A raised portion provided in at least one buttress region of the pair of sidewalls, And a carcass wound up from the inside to the outside in the tire width direction so as to sandwich the bead filler, The carcass has a first ply laminated relatively radially inward in the tire diameter direction in the tread and a second ply laminated relatively radially outward in the tire diameter direction in the tread, The wound-up ends of the first ply and the wound-up ends of the second ply are each disposed radially outside the radially outer end of the bead filler via a distance of 80% or more of the radial length of the bead filler in the tire diameter direction, The wound-up ends of the first ply and the wound-up ends of the second ply are each disposed at a position overlapping the raised portion in the tire width direction. A pneumatic tire.

2. The wound-up end of the first ply is disposed radially outside the wound-up end of the second ply. The pneumatic tire according to claim 1.

3. The wound-up ends of the first ply and the wound-up ends of the second ply are each disposed radially inside the mold parting position. The pneumatic tire according to claim 1 or 2.

4. A space of 15 mm or more is provided in the tire diameter direction between the wound-up end of the first ply and the wound-up end of the second ply. The pneumatic tire according to any one of claims 1 to 3.

5. On the inner end of the raised portion in the tire radial direction, an inclined surface is formed that gradually reduces the raised height toward the inner side in the tire radial direction. The turned-up end of the first ply and the turned-up end of the second ply are each arranged at a position that does not overlap with the inclined surface in the tire width direction. The pneumatic tire according to any one of claims 1 to 4.

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