Pneumatic tire

Abstract

The present invention provides a pneumatic tire (2) with excellent durability. The tire (2) has a tread (4), sidewalls (6), beads (8), and a carcass (10). The bead (8) has a core portion (18) and a filler (20). The carcass (10) has four plies (22, 24, 26, 28). The carcass (10) has a cross-ply structure. The side profile of the tire (2) includes a bending point (PB) that protrudes outward in the axial direction. The radial position of the bending point (PB) is substantially the same as the radial position of the outer end (EF) of the filler (20). The side profile may also have two or more bending points.

Description

Technical Field

[0001] The present invention relates to pneumatic tires. More specifically, the present invention relates to improvements in the side profile of tires. Background Art

[0002] For pneumatic tires used in industrial vehicles such as forklifts, durability and low cost are required. Industrial vehicles travel at low speeds, so high performance during high-speed driving is not required for these tires. In light of this situation, industrial vehicle tires use so-called bias tires. A bias tire suitable for industrial vehicles is disclosed in Japanese Unexamined Patent Application Publication No. 2018-99926. This bias tire has a reinforcing layer. This reinforcing layer can contribute to the durability of the tire.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-99926

[0004] Industrial vehicles are used for handling heavy objects, etc. Therefore, a large load is applied to industrial vehicle tires. Moreover, the addition and removal of this load are repeated. In this tire, large compressive deformations and subsequent recoveries are repeated. This compressive deformation mainly occurs in the side portion of the tire. Cracks, peeling, and other damages may occur in the side portion due to this compressive deformation. This damage hinders the long life of the tire. A tire with excellent durability is desired. Summary of the Invention

[0005] An object of the present invention is to provide a pneumatic tire with excellent durability.

[0006] The pneumatic tire of the present invention includes a tread, a pair of sidewalls, a pair of beads, and a carcass. Each sidewall extends radially inward substantially from an end of the tread. Each bead is located at a position substantially axially inward of the sidewall. The bead has a core portion and a filler extending radially outward substantially from the core portion. The carcass is provided between one bead and the other bead along the inside of the tread and the sidewall. The carcass has a bias structure. The tire has a pair of side profiles. Each side profile includes one or more bending points that protrude axially outward. The radial position of one bending point is substantially the same as the radial position of the outer end of the filler.

[0007] The number of bending points in each side profile may also be 2 or more. Preferably, the radial position of any bending point is substantially the same as the radial position of the maximum width point of the side profile.

[0008] The carcass may also have a turned-up end. Preferably, the radial position of any bending point is substantially the same as the radial position of the turned-up end.

[0009] The carcass may also have two or more turned-up ends. Preferably, the radial position of one bending point is substantially the same as the radial position of one turned-up end, and the radial positions of the other bending points are substantially the same as the radial positions of the other turned-up ends.

[0010] Preferably, the number of bending points in each side profile is 3 or more. The carcass may also have three or more curled ends in a region that coincides with or is outside the outer end of the filler in the radial direction. Preferably, bending points exist at positions that are substantially coincident with the positions of the respective curled ends in the radial direction.

[0011] Preferably, the number of bending points in each side profile is 4 or more.

[0012] Preferably, the radial position of each bending point coincides with the outer end of the filler, the maximum width point of the side profile, or the radial position of any curled end.

[0013] Each bending point is clamped by two sections located on the side profile. Preferably, each section is a straight line or a curve that bulges inward in the axial direction.

[0014] Preferably, the bending angle θ of each bending point is 175° or less.

[0015] The thickness of the pneumatic tire of the present invention is larger at the bending points and smaller at other positions. In this tire, deformation is dispersed. Particularly at positions where a large compressive stress is applied, that is, at positions that coincide with the outer end of the filler, concentration of deformation can be suppressed. Damage is difficult to occur in this tire. The durability of this tire is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention.

[0017] Figure 2 is showing Figure 1 an enlarged cross-sectional view of a part of the pneumatic tire.

[0018] Figure 3 is showing Figure 2 an enlarged cross-sectional view of a part of the pneumatic tire.

[0019] Figure 4 is a cross-sectional view showing a part of a pneumatic tire according to another embodiment of the present invention.

[0020] Figure 5 is showing Figure 4 an enlarged cross-sectional view of a part of the pneumatic tire.

[0021] Figure 6 is showing Figure 4 an enlarged cross-sectional view of another part of the pneumatic tire.

[0022] Figure 7 is showing Figure 4 an enlarged cross-sectional view of yet another part of the pneumatic tire.

[0023] Figure 8 is an enlarged cross-sectional view of still another other part of the pneumatic tire indicated by Figure 4 .

[0024] Explanation of reference numerals: 2, 48... pneumatic tire; 4... tread; 6, 50... sidewall; 8, 52... bead; 10, 54... carcass; 12... breaker; 18, 56... core; 20, 58... filler; 22, 60... first ply; 24, 62... second ply; 26, 64... third ply; 28, 66... fourth ply; 30... first main part; 32... first folded-back part; 34... second main part; 36... second folded-back part; 38... third main part; 40... third folded-back part; 42... fourth main part; 44... fourth folded-back part; EF... outer end of the filler; E1... first folded-back end; E2... second folded-back end; E3... third folded-back end; E4... fourth folded-back end; PB... bending point; PB1... first bending point; PB2... second bending point; PB3... third bending point; PB4... fourth bending point; Pm... maximum width point; S1... first section; S2... second section; S3... third section; S4... fourth section. Detailed Description of the Preferred Embodiments

[0025] Hereinafter, the present invention will be described in detail with appropriate reference to the drawings and based on preferred embodiments.

[0026] Figure 1 and Figure 2 shows the pneumatic tire 2. Figure 1 shows a meridional section of the tire 2. In Figure 1 , the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In Figure 1 , the center line CL coincides with the equatorial plane of the tire 2. The tire 2 has a structure that is mirror-symmetric with respect to the equatorial plane except for the tread pattern described later. In Figure 1 , the auxiliary line BL represents the baseline. The baseline BL defines the diameter of the rim on which the tire 2 is mounted. In Figure 1 , the arrow Ht represents the height of the tire 2 from the baseline BL. The height Ht is measured along the radial direction. In Figure 1 , the reference numeral Pm is the maximum width point. The distance between the two maximum width points Pm is the maximum value of the axial dimension of the tire 2.

[0027] The tire 2 has a tread 4, a pair of sidewalls 6, a pair of beads 8, a carcass 10, and a breaker 12. A tube (not shown) is inserted into the tire 2. The tire 2 may also be a tubeless type. The tire 2 is mounted on an industrial vehicle such as a forklift.

[0028] The tread 4 has a tread surface 14 that comes into contact with the road surface. A plurality of grooves 16 are engraved in the tread 4. Each groove 16 extends substantially axially. The tread pattern is formed by these grooves 16. The tread 4 is formed of a crosslinked rubber having excellent abrasion resistance, heat resistance, and grip. The tread 4 may also have a base layer and a top layer. The tread 4 may also have three or more layers.

[0029] Each sidewall 6 extends substantially radially inward from the end of the tread 4. The radially outer end of the sidewall 6 is joined to the tread 4. The sidewall 6 is formed of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 6 prevents damage to the carcass 10. The material of the sidewall 6 may be the same as that of the tread 4. The sidewall 6 may also have a bead portion in the region on its radially inner side. The bead portion can be formed of a crosslinked rubber having excellent abrasion resistance.

[0030] Each bead 8 is located axially inside the sidewall 6 and at a radially inner position. The bead 8 includes a core portion 18 and a filler 20 that extends radially outward from the core portion 18. The core portion 18 is annular and includes a wound non-stretchable wire. A typical material of the wire is steel. The filler 20 tapers toward the radially outer front end. The filler 20 has an outer end EF (radially outer end). The filler 20 is composed of a crosslinked rubber with high hardness. The filler 20 may also have a shape in which the change in thickness along the radial direction is small (in other words, a sheet shape).

[0031] The carcass 10 is stretched between the beads 8 on both sides and along the tread 4 and the sidewall 6. The carcass 10 has a first ply 22, a second ply 24, a third ply 26, and a fourth ply 28. The number of plies is 4. Although not shown, each ply is composed of a plurality of ply cords arranged side by side and skim coat. The absolute value of the angle formed by each ply cord with respect to the equatorial plane CL is 30° or more and 70° or less. The inclination direction of the ply cords of one ply with respect to the equatorial plane CL is opposite to the inclination direction of the ply cords of the ply that overlaps with the said ply. In other words, the carcass 10 has a bias structure. A tire 2 having a bias structure for the carcass 10 is called a bias tire. The ply cords are composed of organic fibers. As preferred organic fibers, polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers can be exemplified. The number of plies may be 3 or less, or may be 5 or more.

[0032] The first ply 22 turns back from the axially inner side toward the outer side around the core portion 18. By this turning back, a first main portion 30 and two first turning-back portions 32 are formed in the first ply 22. In Figure 1 and Figure 2 one of the first turning-back portions 32 is shown. The first turning-back portion 32 has a first turning-back end E1.

[0033] The second ply 24 is folded back from the axially inner side toward the outer side around the core portion 18. By this folding back, a second main portion 34 and two second folded-back portions 36 are formed in the second ply 24. In Figure 1 and Figure 2 one of the second folded-back portions 36 is shown. This second folded-back portion 36 has a second folded-back end E2. This second folded-back end E2 is located at a position radially inner than the first folded-back end E1.

[0034] The third ply 26 is folded back from the axially inner side toward the outer side around the core portion 18. By this folding back, a third main portion 38 and two third folded-back portions 40 are formed in the third ply 26. In Figure 1 and Figure 2 one of the third folded-back portions 40 is shown. This third folded-back portion 40 has a third folded-back end E3. This third folded-back end E3 is located at a position radially inner than the second folded-back end E2.

[0035] The fourth ply 28 is folded back from the axially inner side toward the outer side around the core portion 18. By this folding back, a fourth main portion 42 and two fourth folded-back portions 44 are formed in the fourth ply 28. In Figure 1 and Figure 2 one of the fourth folded-back portions 44 is shown. This fourth folded-back portion 44 has a fourth folded-back end E4. This fourth folded-back end E4 is located at a position radially inner than the third folded-back end E3.

[0036] The buffer layer 12 is located at a position radially inner than the tread 4. The buffer layer 12 is laminated with the carcass 10. In other words, the buffer layer 12 is located at a position between the tread 4 and the carcass 10. The buffer layer 12 strengthens the carcass 10. Although not shown, the buffer layer 12 is composed of a plurality of cords arranged side by side and skim rubber. Each cord is inclined with respect to the equatorial plane CL. The absolute value of the inclination angle is usually 30° or more and 70° or less. The buffer layer 12 may also have a plurality of layers.

[0037] In the tire 2 of the present invention, the region of the tire 2 that can be visually observed from an infinite distance in the axial direction is called the "side surface". In the present invention, Figure 1 the contour of the side surface in the meridian cross section shown is called the side surface contour. The tire 2 has a pair of side surface contours. In the present embodiment, the shape of one side surface contour is substantially line-symmetric with respect to the center line CL with the shape of the other side surface contour. In Figure 1 and Figure 2 one of the side surface contours is shown. This side surface contour is located at a position axially right of the center line CL.

[0038] Figure 3 is an enlarged cross-sectional view showing a part of the pneumatic tire 2 of Figure 2 . In Figure 3 the illustration of the carcass 10 is omitted.Figure 3 A part of the side profile is shown. This side profile has a bending point PB (Bending Point). As is clear from Figure 1 and Figure 2 the number of bending points PB in this side profile is 1. This bending point PB is clamped by a first section S1 and a second section S2. The first section S1 is located radially outside the bending point PB. The second section S2 is located radially inside the bending point PB. In the present embodiment, the first section S1 is a straight line and the second section S2 is a curve (specifically, an arc). The second section S2 bulges inward in the axial direction.

[0039] In Figure 3 a first tangent T1 and a second tangent T2 are shown. The first tangent T1 is connected to the first section S1 at the bending point PB. The second tangent T2 is connected to the second section S2 at the bending point PB. As described above, the first section S1 is a straight line. The first tangent T1 extends in the same direction as the first section S1. In the present invention, a straight line extending in the same direction as the direction of a section that is a straight line is called the tangent of that section.

[0040] In Figure 3 the arrow θ is the angle between the first tangent T1 and the second tangent T2. The angle θ is measured counterclockwise from the tangent (i.e., the first tangent T1) of the section on the radially outer side (i.e., the first section S1) to the tangent (i.e., the second tangent T2) of the section on the radially inner side (i.e., the second section S2). Additionally, in the side profile to the left of the center line CL, the angle θ is measured clockwise from the tangent of the section on the radially outer side to the tangent of the section on the radially inner side.

[0041] At the bending point PB, the side profile bends. Therefore, the angle θ is not 180°. In Figure 3 the angle θ is less than 180°. In other words, the bending point PB bulges outward in the axial direction. Hereinafter, the angle θ is referred to as the "bending angle".

[0042] In Figure 3 the arrow HB represents the height of the bending point PB from the baseline BL, and the arrow HF represents the height of the outer end EF of the filler 20 from the baseline BL. The heights HB and HF are measured along the radial direction.

[0043] As is clear from Figure 3 the height HB and the height HF are substantially the same. In other words, the radial positions of the bending point PB and the outer end EF of the filler 20 are substantially the same. In the present invention, when the absolute value of the difference between the two heights is 5% or less of the height Ht of the tire 2 (refer to Figure 1 ), these heights are regarded as "substantially the same". In other words, the height HB satisfies the following formula.

[0044] -0.05 ≤ (HB - HF) / Ht ≤ 0.05

[0045] As described according to Figure 3 As is clear, in the tire 2 having a bending point PB protruding outwardly, the thickness near the bending point PB is large, and the thickness at a position away from the bending point PB is small. When the tire 2 is flexed, stress tends to concentrate at the outer end EF of the filler 20. In the tire 2 having a bending point PB protruding outwardly at a position substantially coinciding with the position of the outer end EF in the radial direction, the deformation is dispersed due to the non-uniformity of the rubber thickness. The bending point PB suppresses damage common to the bias tire 2 (such as peeling of the cord from the skim coat, peeling of the sidewall 6 from the carcass 10, etc.). Despite the large number of plies, the durability of this tire 2 is excellent.

[0046] From the viewpoint of dispersing deformation, the bending angle θ is preferably 175° or less, more preferably 172° or less, and particularly preferably 170° or less. From the viewpoint of the rigidity of the tire 2, the bending angle θ is preferably 150° or more.

[0047] In Figure 3 , the imaginary line IL represents the contour assuming that the bending point PB does not exist. As is clear from the comparison between this contour IL and the side profile, the thickness of the tire 2 at positions other than the bending point PB is small. Therefore, this tire 2 is light. Moreover, this tire 2 can be obtained at low cost.

[0048] As described above, the bending point PB is clamped by a straight line (first section S1) and a curve protruding inwardly in the axial direction (second section S2). Both of the sections clamping the bending point PB may be straight lines. Both of the sections clamping the bending point PB may be curves protruding inwardly. One or both of the sections clamping the bending point PB may be curves protruding outwardly in the axial direction. The combinations of the two sections clamping the bending point PB are as follows.

[0049] Straight line - straight line

[0050] Straight line - inwardly protruding curve

[0051] Straight line - outwardly protruding curve

[0052] Inwardly protruding curve - inwardly protruding curve

[0053] Inwardly protruding curve - outwardly protruding curve

[0054] Outwardly protruding curve - outwardly protruding curve

[0055] From the viewpoint of dispersing deformation, it is preferable that the bending point PB is clamped by a straight line or an inwardly protruding curve. The preferred combinations of the two sections are as follows.

[0056] Straight line - Straight line

[0057] Straight line - Concave curve

[0058] Concave curve - Concave curve

[0059] The most preferred combination is: Concave curve - Concave curve.

[0060] The side profile may also have a plurality of bending points PB. From the viewpoint of dispersion deformation, the number of bending points PB is preferably more than two, more preferably more than three, and particularly preferably more than four. The number is preferably 8 or less.

[0061] In the present invention, the dimensions and angles of each component of the tire 2 are measured in a state where the tire 2 is assembled on a regular rim and filled with air so as to become a regular internal pressure. When measuring, no load is applied to the tire 2. In this specification, a regular rim means a rim specified in the specifications on which the tire 2 is based. The "standard rim" in the JATMA specification, the "Design Rim" in the TRA specification, and the "Measuring Rim" in the ETRTO specification are regular rims. In this specification, a regular internal pressure means the internal pressure specified in the specifications on which the tire 2 is based. The "maximum air pressure" in the JATMA specification, the "maximum value" described in the "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA specification, and the "INFLATION PRESSURE" in the ETRTO specification are regular internal pressures.

[0062] Figure 4 is a cross-sectional view showing a part of the pneumatic tire 48 according to another embodiment of the present invention. The structure of the part of the tire 48 that is not Figure 4 shown is the same as the structure of the Figure 1 shown tire 2. The tire 48 has a tread (not shown), a pair of sidewalls 50, a pair of beads 52, a carcass 54, and a buffer layer (not shown). An inner tube is inserted into the tire 48. The tire 48 may also be a tubeless type. The tire 48 is mounted on an industrial vehicle such as a forklift. In Figure 4 the drawing reference numeral Pm denotes the maximum width point.

[0063] The structure and material of the tread are the same as the structure and material of the Figure 1 shown tread 4. The structure and material of the sidewall 50 are the same as the structure and material of the Figure 1 shown sidewall 6. The structure and material of the bead 52 are the same as the structure and material of the Figure 1The structures and materials of the bead 8 shown are the same. Therefore, the bead 52 has a core 56 and a filler 58.

[0064] The carcass 54 is the same as Figure 1 and Figure 2 the carcass 10 shown, and includes a first ply 60, a second ply 62, a third ply 64, and a fourth ply 66. The first ply 60 has a first turned-back end E1. The second ply 62 has a second turned-back end E2. The third ply 64 has a third turned-back end E3. The fourth ply 66 has a fourth turned-back end E4.

[0065] The tire 48 has a pair of side profiles. The shape of one side profile is substantially line-symmetric with respect to the center line to the shape of the other side profile. Figure 4 The side profile located at a position to the right of the center line is shown. This side profile has a first bending point PB1, a second bending point PB2, a third bending point PB3, and a fourth bending point PB4.

[0066] Figure 5 is an enlarged cross-sectional view of a part of the pneumatic tire 48 showing Figure 4 . Figure 5 The first bending point PB1 is shown in. The side profile bends at the first bending point PB1. The first bending point PB1 is clamped by a first section S1 and a second section S2. The first section S1 is located radially outside the first bending point PB1. The second section S2 is located radially inside the first bending point PB1. In the present embodiment, the first section S1 is a curve (specifically, an arc), and the second section S2 is a curve (specifically, an arc). The first section S1 bulges axially outward. The second section S2 bulges axially inward. The bending angle θ of the first bending point PB1 is less than 180°. The first bending point PB1 bulges axially outward.

[0067] In Figure 5 , the arrow HB1 represents the height of the first bending point PB1 from the baseline BL, and the arrow Hm represents the height of the maximum width point Pm from the baseline BL. The heights HB1 and Hm are measured along the radial direction.

[0068] As is clear from Figure 5 , the difference between the height HB1 and the height Hm is very small. The height HB1 and the height Hm are substantially the same. In other words, the radial positions of the first bending point PB1 and the maximum width point Pm are substantially the same. The heights HB1 and Hm satisfy the following formula.

[0069] -0.05 ≤ (HB1 - Hm) / Ht ≤ 0.05

[0070] The first bending point PB1 bulges outward, so the thickness of the tire 48 near the first bending point PB1 is relatively large. When the tire 48 flexes, stress is likely to concentrate at the maximum width point Pm. In the tire 48 where there is a bending point bulging outward at a position radially consistent with the maximum width point Pm, deformation is difficult to concentrate at the maximum width point Pm. The first bending point PB1 suppresses damages common in the bias tire 48 (such as the peeling of the cord and the skim coat, the peeling of the sidewall 50 and the carcass 54, etc.). Despite the large number of plies, the tire 48 has excellent durability.

[0071] From the viewpoint of dispersing deformation, the bending angle θ of the first bending point PB1 is preferably 175° or less, more preferably 172° or less, and particularly preferably 170° or less. From the viewpoint of the rigidity of the tire 48, the bending angle θ is preferably 150° or more. The first section S1 can be a straight line or a curve bulging inward. The second section S2 can be a straight line or a curve bulging outward. Preferably, the first section S1 is a straight line or a curve bulging inward, and the second section S2 is a straight line or a curve bulging inward.

[0072] Figure 6 It represents Figure 4 An enlarged cross-sectional view of another part of the pneumatic tire 48. Figure 6 The second bending point PB2 is shown in []. The side profile bends at the second bending point PB2. The second bending point PB2 is clamped by the second section S2 and the third section S3. The second section S2 is located radially outside the second bending point PB2. The third section S3 is located radially inside the second bending point PB2. In the present embodiment, the second section S2 is a curve (specifically, an arc), and the third section S3 is a curve (specifically, an arc). The second section S2 bulges inward in the axial direction. The third section S3 bulges inward in the axial direction. The bending angle θ of the second bending point PB2 is less than 180°. The second bending point PB2 bulges outward in the axial direction.

[0073] In Figure 6 the arrow HB2 represents the height of the second bending point PB2 from the baseline BL, and the arrow HE1 represents the height of the first turning end E1 from the baseline BL. The heights HB2 and HE1 are measured along the radial direction.

[0074] As is clear from Figure 6 the height HB2 is substantially the same as the height HE1. In other words, the radial position of the second bending point PB2 is substantially the same as the radial position of the first turning end E1. The heights HB2 and HE1 satisfy the following formula.

[0075] -0.05 ≤ (HB2 - HE1) / Ht ≤ 0.05

[0076] The second bending point PB2 bulges outward, so the thickness of the tire 48 near the second bending point PB2 is relatively large. When the tire 48 flexes, stress is likely to concentrate at the turning end. In the tire 48 where there is a bending point bulging outward at a position radially consistent with the turning end, deformation is difficult to concentrate at the turning end. The second bending point PB2 suppresses damages common to the bias tire 48 (such as the peeling of the cord from the skim coat, the peeling of the sidewall 50 from the carcass 54, etc.). Despite the relatively large number of plies, the tire 48 has excellent durability.

[0077] From the perspective of dispersing deformation, the bending angle θ of the second bending point PB2 is preferably 175° or less, more preferably 172° or less, and particularly preferably 170° or less. From the perspective of the rigidity of the tire 48, the bending angle θ is preferably 150° or more. The second section S2 can be a straight line or a curve bulging outward. The third section S3 can be a straight line or a curve bulging outward. Preferably, the second section S2 is a straight line or a curve bulging inward, and the third section S3 is a straight line or a curve bulging inward.

[0078] Figure 7 It represents Figure 4 Another enlarged cross-sectional view of a part of the inflated tire 48. Figure 7 The third bending point PB3 is shown in [the figure]. The side profile bends at the third bending point PB3. The third bending point PB3 is clamped by the third section S3 and the fourth section S4. The third section S3 is located radially outside the third bending point PB3. The fourth section S4 is located radially inside the third bending point PB3. In the present embodiment, the third section S3 is a curve (specifically, an arc), and the fourth section S4 is a straight line. The third section S3 bulges inward in the axial direction. The bending angle θ of the third bending point PB3 is less than 180°. The third bending point PB3 bulges outward in the axial direction.

[0079] In Figure 7 [the figure], the arrow HB3 represents the height of the third bending point PB3 from the baseline BL, and the arrow HE2 represents the height of the second turning end E2 from the baseline BL. The heights HB3 and HE2 are measured along the radial direction.

[0080] As is clear from Figure 7 [the figure], the height HB3 is substantially the same as the height HE2. In other words, the radial position of the third bending point PB3 is substantially the same as the radial position of the second turning end E2. The heights HB3 and HE2 satisfy the following formula.

[0081] -0.05 ≤ (HB3 - HE2) / Ht ≤ 0.05

[0082] The third bending point PB3 bulges outward, so the thickness of the tire 48 near the third bending point PB3 is relatively large. When the tire 48 flexes, stress is likely to concentrate at the turning end. In the tire 48 where there is a bending point bulging outward at a position radially consistent with the position of the turning end, deformation is difficult to concentrate at the turning end. The third bending point PB3 suppresses damages common to the bias tire 48 (such as the peeling of the cord from the skim coat, the peeling of the sidewall 50 from the carcass 54, etc.). Despite the large number of plies, the tire 48 has excellent durability.

[0083] From the perspective of dispersing deformation, the bending angle θ of the third bending point PB3 is preferably 175° or less, more preferably 172° or less, and particularly preferably 170° or less. From the perspective of the rigidity of the tire 48, the bending angle θ is preferably 150° or more. The third section S3 can be a straight line or a curve bulging outward. The fourth section S4 can be a curve bulging inward or a curve bulging outward. Preferably, the third section S3 is a straight line or a curve bulging inward, and the fourth section S4 is a straight line or a curve bulging inward.

[0084] Figure 8 is a schematic representation of Figure 4 an enlarged cross-sectional view of another part of the inflated tire 48. Figure 8 The fourth bending point PB4 is shown. The side profile bends at the fourth bending point PB4. The fourth bending point PB4 is clamped by the fourth section S4 and the fifth section S5. The fourth section S4 is located radially outside the fourth bending point PB4. The fifth section S5 is located radially inside the fourth bending point PB4. In the present embodiment, the fourth section S4 is a straight line and the fifth section S5 is a curve (specifically, an arc). The fifth section S5 bulges inward in the axial direction. The bending angle θ of the fourth bending point PB4 is less than 180°. The fourth bending point PB4 bulges outward in the axial direction.

[0085] In Figure 8 the figure, the arrow HB4 represents the height of the fourth bending point PB4 from the baseline BL, and the arrow HE3 represents the height of the third turning end E3 from the baseline BL. The heights HB4 and HE3 are measured along the radial direction.

[0086] As is clear from Figure 8 the figure, the height HB4 and the height HE3 are substantially the same. In other words, the radial positions of the fourth bending point PB4 and the third turning end E3 are substantially the same. The heights HB4 and HE3 satisfy the following formula.

[0087] -0.05 ≤ (HB4 - HE3) / Ht ≤ 0.05

[0088] The fourth bending point PB4 bulges outward, so the thickness of the tire 48 near the fourth bending point PB4 is relatively large. When the tire 48 flexes, stress is likely to concentrate at the turning end. In the tire 48 where there is a bending point that bulges outward at a position radially consistent with the position of the turning end, deformation is difficult to concentrate at the turning end. The fourth bending point PB4 suppresses damages common in bias tires 48 (such as the peeling of cords from the skim coat, the peeling of the sidewall 50 from the carcass 54, etc.). Despite having a relatively large number of plies, the tire 48 has excellent durability.

[0089] From the perspective of dispersing deformation, the bending angle θ of the fourth bending point PB4 is preferably 175° or less, more preferably 172° or less, and particularly preferably 170° or less. From the perspective of the rigidity of the tire 48, the bending angle θ is preferably 150° or more. The fourth section S4 can be a curve that bulges inward or a curve that bulges outward. The fifth section S5 can be a straight line or a curve that bulges outward. Preferably, the fourth section S4 is a straight line or a curve that bulges inward, and the fifth section S5 is a straight line or a curve that bulges inward.

[0090] As is clear from Figure 8 In the radial direction, the position of the outer end EF of the filler 58 coincides with the position of the third turning end E3. Therefore, the height HE3 is also the height HF of the outer end EF. The radial position of the fourth bending point PB4 is substantially the same as the radial position of the outer end EF of the filler 58. The heights HB4 and HF satisfy the following formula.

[0091] -0.05 ≤ (HB4 - HF) / Ht ≤ 0.05

[0092] The fourth bending point PB4 suppresses damages caused by the third turning end E3 and also suppresses damages caused by the filler 58.

[0093] The position of the outer end EF of the filler 58 can also be different from the position of the third turning end E3. In this case, preferably, there is a bending point whose radial position is substantially the same as the radial position of the third turning end E3, and there is a bending point whose radial position is substantially the same as the radial position of the outer end EF.

[0094] As is clear from Figure 4 The tire 48 does not have a bending point whose radial position coincides with the radial position of the fourth turning end E4. The fourth turning end E4 is located axially outside the bead 52. Therefore, stress is difficult to concentrate at the fourth turning end E4. Even without a bending point whose radial position coincides with the radial position of the fourth turning end E4, damages at the fourth turning end E4 can be suppressed.

[0095] In the tire 48, there are bending points at the following positions:

[0096] (1) A position substantially consistent with the position of the outer end EF of the filler 58,

[0097] (2) A position substantially consistent with the position of the maximum width point Pm, and

[0098] (3) A position substantially consistent with the position of the turning-back end.

[0099] The bending point may also exist only at the following positions:

[0100] (1) A position substantially consistent with the position of the outer end EF of the filler 58, and

[0101] (2) A position substantially consistent with the position of the maximum width point Pm.

[0102] The bending point may also exist only at the following positions:

[0103] (1) A position substantially consistent with the position of the outer end EF of the filler 58, and

[0104] (3) A position substantially consistent with the position of the turning-back end.

[0105] In this tire 48, the first turning-back end E1 and the second turning-back end E2 are located radially outside the position of the outer end EF of the filler 58. The position of the third turning-back end E3 is radially consistent with the position of the outer end EF of the filler 58. This tire 48 has three curling ends (E1, E2, and E3) in a region that is radially consistent with or outside the outer end EF of the filler 58. In at least one of the curling ends located in this region, it is preferable that there is a bending point with a consistent radial position. The number of curling ends having a bending point with a consistent radial position and located in this region is more preferably 2 or more, and particularly preferably 3 or more. It is preferable that there are bending points with consistent radial positions in all the curling ends located in this region.

[0106] The types of side profiles based on the presence or absence of bending points with consistent radial positions are as follows.

[0107]

[0108]

[0109] Even in any type, it is preferable that there is a bending point with a radial position consistent with the outer end EF of the filler 58.

[0110] Ideally, the tire 48 has bending points at all the following positions:

[0111] (1) A position substantially consistent with the position of the outer end EF of the filler 58,

[0112] (2) A position substantially consistent with the position of the maximum width point Pm, and

[0113] (3) A position that is consistent with the outer end EF of the filler along the radial direction or is substantially consistent with the position of each of all the rolled-up ends in a region located outside the outer end EF.

[0114] Examples

[0115] Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be construed restrictively based on the descriptions of these examples.

[0116] [Example 1]

[0117] A forklift tire as shown in Figures 1 - 3 was manufactured. The size of this tire is "7.00 - 12 12PR". The carcass of this tire has a first ply, a second ply, a third ply, and a fourth ply. The first ply has a first turned-back end, the second ply has a second turned-back end, the third ply has a third turned-back end, and the fourth ply has a fourth turned-back end. The first turned-back end, the second turned-back end, and the third turned-back end are located outside the outer end of the filler in the radial direction. The fourth turned-back end is located outside the bead in the axial direction. The side profile has one bending point. The position of this bending point is substantially consistent with the position of the outer end of the filler in the radial direction.

[0118] [Examples 2 - 9 and Comparative Examples 1 - 2]

[0119] Except that the number and position of the bending points were set as shown in Tables 1 - 3 below, the tires of Examples 2 - 9 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1.

[0120] [Comparative Example 3]

[0121] Except that no bending point was formed in the side profile and a reinforcing layer was inserted into the carcass, the tire of Comparative Example 3 was obtained in the same manner as in Example 1. This reinforcing layer is similar to the reinforcing layer disclosed in Japanese Unexamined Patent Application Publication No. 2018 - 99926.

[0122] [Durability]

[0123] The tire was assembled on a "12×5.00S" rim, and air was filled into this tire so that the internal pressure became 850 kPa. This tire was installed on a drum - type running test machine and run under the following conditions.

[0124] Speed: 20 km / h

[0125] Load: 18.69 kN

[0126] Ambient temperature: 25 - 30 °C

[0127] The driving distance was measured until damage occurred on the side of the tire. The results are shown as indices in Tables 1 to 3 below. The larger the value, the greater the driving distance.

[0128] [Cost]

[0129] The rubber amount of the tire was calculated. The results are shown as indices in Tables 1 to 3 below.

[0130] The smaller the value, the less the rubber amount.

[0131] [Comprehensive Evaluation]

[0132] Grading was performed according to the following criteria.

[0133] A: Durability is 120 or more and cost is less than 100

[0134] B: Durability is 110 or more and less than 120, and cost is less than 100

[0135] C: Durability is less than 110

[0136] The results are shown in Tables 1 to 3 below.

[0137]

Table 1

[0138] Table 1 Evaluation Results

[0139]

[0140]

Table 2

[0141] Table 2 Evaluation Results

[0142]

[0143]

Table 3

[0144] Table 3 Evaluation Results

[0145]

[0146] As shown in Tables 1 to 3, the durability of the tires of each example is excellent. From this evaluation result, the superiority of the present invention is obvious.

[0147] Industrial Applicability

[0148] The pneumatic tire of the present invention can be mounted on various vehicles.

Claims

1. A pneumatic tire having a tread, a pair of sidewalls, a pair of beads, and a carcass, characterized in that, each sidewall extends substantially radially inward from an end portion of the tread, each bead is located at a position substantially radially inward of the sidewall, the bead has a core portion and a filler extending substantially radially outward from the core portion, the carcass is provided between one bead and the other bead along the inner sides of the tread and the sidewalls, the carcass has a cross-ply structure, the carcass has: a first turned-back end, and a second turned-back end located radially inward of the first turned-back end, and the first turned-back end and the second turned-back end are located radially outside of the radially outer end of the filler, the pneumatic tire has a pair of side profiles, each side profile includes three or more bending points protruding axially outward, the radial position of one bending point is substantially the same as the radial position of the radially outer end of the filler, the radial position of another bending point is substantially the same as the radial position of the second turned-back end, the radial position of yet another bending point is substantially the same as the radial position of the first turned-back end, the "substantially the same" means that the ratio of the absolute value of the difference between two heights to the height of the tire is 5% or less.

2. The pneumatic tire according to claim 1, characterized in that, the carcass has a third turned-back end located radially inward of the second turned-back end, the side profile includes four or more bending points protruding axially outward, the radial position of one bending point is substantially the same as the radial position of the third turned-back end.

3. The pneumatic tire according to claim 1 or 2, characterized in that, each bending point is clamped by two sections located on the side profile, each section is a straight line or a curve protruding axially inward.

4. The pneumatic tire according to claim 1 or 2, characterized in that, the bending angle θ of each bending point is 175° or less.

Images