Pneumatic tires

Abstract

To provide a pneumatic tire 2 that is excellent in durability.SOLUTION: A tire 2 includes a tread 4, a side wall 6, a bead 8, and a carcass 10. The bead 8 includes a core 18 and a filler 20. The carcass 10 includes four plies 22, 24, 26, and 28. The carcass 10 has a bias structure. A side profile of the tire 2 includes a projected inflection point PB projected outward in an axial direction. A location in a radial direction of the inflection point PB substantially coincides with a location in a radial direction of an outer end EF of the filler 20. The side profile may include two or more inflection points.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire, and more particularly to an improvement in the side profile of the tire. [Background technology]

[0002] Pneumatic tires used in industrial vehicles such as forklifts are required to be durable and low cost. Since industrial vehicles run at low speeds, high performance at high speeds is not required for these tires. For these reasons, so-called bias tires are used for industrial vehicles. JP 2018-99926 A discloses a bias tire suitable for industrial vehicles. This bias tire has a reinforcing layer. This reinforcing layer can contribute to the durability of the tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP2018-99926A Summary of the Invention [Problem to be solved by the invention]

[0004] Industrial vehicles are used for transporting heavy objects, etc. Therefore, tires for industrial vehicles are subjected to a large load. Moreover, the application and removal of this load is repeated. In these tires, large compressive strain and subsequent recovery are repeated. This compressive strain occurs mainly in the side portions of the tire. This compressive strain can cause damage such as cracks and peeling in the side portions. This damage impedes the long life of the tire. Tires with excellent durability are desired.

[0005] An object of the present invention is to provide a pneumatic tire having excellent durability. [Means for solving the problem]

[0006] A pneumatic tire according to the present invention has a tread, a pair of sidewalls, a pair of beads, and a carcass. Each sidewall extends from an end of the tread in a generally radially inward direction. Each bead is located generally axially inward from the sidewall. The bead has a core and a filler extending from the core in a generally radially outward direction. The carcass is bridged between one bead and the other bead along the inner side 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 are convex axially outward. The radial position of one bending point substantially coincides with the radial position of the outer end of the filler.

[0007] The number of inflection points in each side profile may be 2 or more. Preferably, the radial position of any inflection point substantially coincides with the radial position of the maximum width point of the side profile.

[0008] The carcass may have a turned-up end. Preferably, the radial position of any bending point substantially coincides with the radial position of the turned-up end.

[0009] The carcass may have two or more turn ends. Preferably, the radial position of one bending point substantially coincides with the radial position of one turn end and the radial position of another bending point substantially coincides with the radial position of another turn end.

[0010] Preferably, the number of bending points in each side profile is 3 or more. The carcass may have three or more turn-up ends in a zone that is radially coincident with or outboard of the outer ends of the fillers. Preferably, the bending points are located at positions that are substantially radially coincident with the positions of the respective turn-up ends.

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

[0012] Preferably, the radial position of each inflection point is: (1) The outer end of the filler (2) The maximum width point of the side profile or (3) Either winding end The radial position of the

[0013] Each bending point is bounded by two segments on the side profile, each of which is preferably a straight line or an axially inwardly convex curve.

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

[0015] The thickness of the pneumatic tire according to the present invention is large at the bending points and small at other points. In this tire, strain is dispersed. In particular, concentration of strain is suppressed at positions where large compressive stress is applied, that is, positions that coincide with the outer ends of the fillers. This tire is less susceptible to damage. This tire has excellent durability. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view showing a portion of a pneumatic tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view showing a portion of the pneumatic tire of FIG. [Diagram 3] FIG. 3 is an enlarged cross-sectional view showing a portion of the pneumatic tire of FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a portion of a pneumatic tire according to another embodiment of the present invention. [Diagram 5] FIG. 5 is an enlarged cross-sectional view showing a portion of the pneumatic tire of FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing another part of the pneumatic tire of FIG. [Figure 7]FIG. 7 is an enlarged cross-sectional view showing still another part of the pneumatic tire of FIG. [Figure 8] FIG. 8 is an enlarged cross-sectional view showing still another part of the pneumatic tire of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[0018] A pneumatic tire 2 is shown in Figures 1 and 2. Figure 1 shows a cross section of the tire 2 along a meridian. 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. This tire 2 has a structure that is mirror-symmetrical with respect to the equatorial plane, except for the tread pattern described later. In Figure 1, the auxiliary line BL represents a 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 symbol Pm represents the maximum width point. The distance between the two maximum width points Pm is the maximum value of the axial size of the tire 2.

[0019] 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 be of a tubeless type. The tire 2 is mounted on an industrial vehicle such as a forklift.

[0020] The tread 4 has a tread surface 14 that comes into contact with the road surface. A plurality of grooves 16 are formed in the tread 4. Each groove 16 generally extends in the axial direction. These grooves 16 form a tread pattern. The tread 4 is formed of a crosslinked rubber that has excellent abrasion resistance, heat resistance, and grip. The tread 4 may have a base layer and a cap layer. The tread 4 may have three or more layers.

[0021] Each sidewall 6 extends radially inwardly from an end of the tread 4. A radially outer end of each sidewall 6 is joined to the tread 4. Each sidewall 6 is formed of a crosslinked rubber having excellent cut resistance and weather resistance. Each sidewall 6 prevents damage to the carcass 10. The material of the sidewall 6 may be the same as the material of the tread 4. Each sidewall 6 may have a clinch in its radially inner zone. The clinch may be formed of a crosslinked rubber having excellent abrasion resistance.

[0022] Each bead 8 is located axially and radially inward of the sidewall 6. The bead 8 includes a core 18 and a filler 20 extending radially outward from the core 18. The core 18 is ring-shaped and includes a wound inelastic wire. The wire is typically made of steel. The filler 20 tapers radially outward. The filler 20 has an outer end EF (radially outer end). The filler 20 is made of high-hardness crosslinked rubber. The filler 20 may have a shape with little change in thickness along the radial direction (in other words, a sheet shape).

[0023] The carcass 10 is laid between the beads 8 on both sides and is aligned with 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 four. Although not shown, each ply is made of a plurality of cords arranged in parallel and a topping rubber. The absolute value of the angle that each cord makes with respect to the equatorial plane CL is 30° or more and 70° or less. The inclination direction of the cord of one ply with respect to the equatorial plane CL is opposite to the inclination direction of the cord of the ply overlapping with this ply with respect to the equatorial plane CL. In other words, the carcass 10 has a bias structure. A tire 2 in which the carcass 10 has a bias structure is called a bias tire. The cord is made of organic fiber. Examples of preferred organic fibers include polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber. The number of plies may be three or less, or five or more.

[0024] The first ply 22 is folded back around the core 18 from the inside to the outside in the axial direction. By this folding back, the first ply 22 is formed with a first main portion 30 and two first turned-up portions 32. One first turned-up portion 32 is shown in Figures 1 and 2. The first turned-up portion 32 has a first turned-up end E1.

[0025] The second ply 24 is folded back around the core 18 from the inside to the outside in the axial direction. By this folding back, the second ply 24 is formed with a second main portion 34 and two second folded back portions 36. One second folded back portion 36 is shown in FIGS. 1 and 2. The second folded back portion 36 has a second folded back end E2. The second folded back end E2 is located radially inward of the first folded back end E1.

[0026] The third ply 26 is folded back around the core 18 from the inside to the outside in the axial direction. By this folding back, the third ply 26 is formed with a third main portion 38 and two third folded back portions 40. One third folded back portion 40 is shown in FIGS. 1 and 2. The third folded back portion 40 has a third folded back end E3. The third folded back end E3 is located radially inward of the second folded back end E2.

[0027] The fourth ply 28 is folded back around the core 18 from the inside to the outside in the axial direction. By this folding back, the fourth ply 28 is formed with a fourth main portion 42 and two fourth turned-up portions 44. One fourth turned-up portion 44 is shown in FIGS. 1 and 2. The fourth turned-up portion 44 has a fourth turned-up end E4. The fourth turned-up end E4 is located radially inward of the third turned-up end E3.

[0028] The breaker 12 is located radially inward of the tread 4. The breaker 12 is laminated with the carcass 10. In other words, the breaker 12 is located between the tread 4 and the carcass 10. The breaker 12 reinforces the carcass 10. Although not shown, the breaker 12 is made of a plurality of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equatorial plane CL. The general absolute value of the inclination angle is 30° or more and 70° or less. The breaker 12 may have a plurality of layers.

[0029] In the tire 2 according to the present invention, an area that can be viewed from an infinite distance in the axial direction of the tire 2 is referred to as a "side surface." In the present invention, the contour of the side surface in the meridian cross section shown in FIG. 1 is referred to as a side profile. The tire 2 has a pair of side profiles. In this embodiment, the shape of one side profile is substantially linearly symmetrical with the shape of the other side profile with respect to the center line CL. One side profile is shown in FIGS. 1 and 2. This side profile is located to the right of the center line CL in the axial direction.

[0030] FIG. 3 is an enlarged cross-sectional view showing a part of the pneumatic tire 2 in FIG. 2. In FIG. 3, the carcass 10 is omitted. In FIG. 3, a part of a side profile is shown. This side profile has a bending point PB. As is clear from FIGS. 1 and 2, the number of bending points PB in this side profile is 1. This bending point PB is sandwiched between a first segment S1 and a second segment S2. The first segment S1 is located outside the bending point PB in the radial direction. The second segment S2 is located inside the bending point PB in the radial direction. In this embodiment, the first segment S1 is a straight line, and the second segment S2 is a curved line (specifically, a circular arc). The second segment S2 is convex axially inward.

[0031] In Fig. 3, a first tangent T1 and a second tangent T2 are shown. The first tangent T1 is tangent to the first segment S1 at the bending point PB. The second tangent T2 is tangent to the second segment S2 at the bending point PB. As described above, the first segment S1 is a straight line. The first tangent T1 extends in the same direction as the direction of the first segment S1. In the present invention, a straight line extending in the same direction as the direction of a straight segment is referred to as a tangent to this segment.

[0032] In Fig. 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 radially outer segment (i.e., the first segment S1) to the tangent (i.e., the second tangent T2) of the radially inner segment (i.e., the second segment S2). Note that in the side profile to the left of the center line CL, the angle θ is measured clockwise from the tangent of the radially outer segment to the tangent of the radially inner segment.

[0033] At the bending point PB, the side profile is bent. Therefore, the angle θ is not 180°. In FIG. 3, the angle θ is smaller than 180°. In other words, the bending point PB is convex outward in the axial direction. Hereinafter, the angle θ is referred to as the "bending angle."

[0034] 3, arrow HB represents the height of inflection point PB from baseline BL, and arrow HF represents the height of outer end EF of filler 20 from baseline BL. Heights HB and HF are measured along the radial direction.

[0035] As is clear from Fig. 3, the height HB substantially coincides with the height HF. In other words, the radial position of the bending point PB substantially coincides with the radial position of the outer end EF of the filler 20. In the present invention, when the ratio of the absolute value of the difference between the two heights to the height Ht of the tire 2 (see Fig. 1) is 5% or less, these heights are considered to be "substantially coincident". In other words, the height HB satisfies the following formula: -0.05 ≦ (HB - HF) / Ht ≦ 0.05

[0036] As is clear from FIG. 3, in a tire 2 having an outwardly convex bend point PB, the tire has a large thickness in the vicinity of the bend point PB and a small thickness at a position away from the bend point PB. When the tire 2 flexes, stress is likely to concentrate at the outer end EF of the filler 20. In a tire 2 having an outwardly convex bend point PB at a position substantially coinciding with the position of the outer end EF in the radial direction, strain is dispersed due to unevenness in the rubber thickness. The bend point PB suppresses damage that is likely to occur in bias tires 2 (peeling between the cord and the topping rubber, peeling between the sidewall 6 and the carcass 10, etc.). This tire 2 has excellent durability despite having a large number of plies.

[0037] From the viewpoint of dispersion of strain, the bending angle θ is preferably equal to or less than 175°, more preferably equal to or less than 172°, and particularly preferably equal to or less than 170°. From the viewpoint of rigidity of the tire 2, the bending angle θ is preferably equal to or greater than 150°.

[0038] In Fig. 3, the imaginary line IL represents a profile when it is assumed that the bending point PB does not exist. As is clear from a comparison between the profile IL and the side profile, the thickness of the tire 2 at positions other than the bending point PB is small. Therefore, the tire 2 is lightweight. Moreover, the tire 2 can be obtained at low cost.

[0039] As described above, the bending point PB is sandwiched between a straight line (first segment S1) and a curved line (second segment S2) that convex inward in the axial direction. Both of the segments that sandwich the bending point PB may be straight lines. Both of the segments that sandwich the bending point PB may be curved lines that convex inward in the axial direction. One or both of the segments that sandwich the bending point PB may be curved lines that convex outward in the axial direction. The combinations of two segments that sandwich the bending point PB are shown below. Straight line - Straight line Straight line - inwardly convex curve Straight line - outwardly convex curve Inwardly convex curve - Inwardly convex curve Inwardly convex curve - outwardly convex curve Outwardly convex curve - Outwardly convex curve

[0040] From the viewpoint of strain distribution, it is preferable that the bending point PB is sandwiched between straight lines or inwardly convex curves. Preferable combinations of two segments are shown below. Straight line - Straight line Straight line - inwardly convex curve Inwardly convex curve - Inwardly convex curve

[0041] The most preferred combination is: Inwardly convex curve - Inwardly convex curve It is.

[0042] The side profile may have a plurality of bending points PB. From the viewpoint of strain dispersion, the number of bending points PB is preferably 2 or more, more preferably 3 or more, and particularly preferably 4 or more. This number is preferably 8 or less.

[0043] 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 mounted on a regular rim and filled with air so as to have a regular internal pressure. No load is applied to the tire 2 during measurement. In this specification, regular rim means a rim defined in the standard on which the tire 2 is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are regular rims. In this specification, regular internal pressure means an internal pressure defined in the standard on which the tire 2 is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures.

[0044] Fig. 4 is a cross-sectional view showing a part of a pneumatic tire 48 according to another embodiment of the present invention. The structure of the portions of the tire 48 not shown in Fig. 4 is the same as that of the tire 2 shown in Fig. 1. The tire 48 has a tread (not shown), a pair of sidewalls 50, a pair of beads 52, a carcass 54, and a breaker (not shown). A tube is inserted into the tire 48. The tire 48 may be of a tubeless type. The tire 48 is mounted on an industrial vehicle such as a forklift. In Fig. 4, the symbol Pm indicates the maximum width point.

[0045] The structure and material of the tread are the same as those of the tread 4 shown in Fig. 1. The structure and material of the sidewall 50 are the same as those of the sidewall 6 shown in Fig. 1. The structure and material of the bead 52 are the same as those of the bead 8 shown in Fig. 1. Thus, the bead 52 has a core 56 and a filler 58.

[0046] 1 and 2, the carcass 54 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 turnup end E1. The second ply 62 has a second turnup end E2. The third ply 64 has a third turnup end E3. The fourth ply 66 has a fourth turnup end E4.

[0047] The tire 48 has a pair of side profiles. The shape of one side profile is substantially symmetrical with respect to the center line to the shape of the other side profile. Fig. 4 shows the side profile located to the right of the center line. The side profile has a first bending point PB1, a second bending point PB2, a third bending point PB3, and a fourth bending point PB4.

[0048] FIG. 5 is an enlarged cross-sectional view showing a part of the pneumatic tire 48 of FIG. 4. FIG. 5 shows a first bending point PB1. The side profile is bent at the first bending point PB1. This first bending point PB1 is sandwiched between a first segment S1 and a second segment S2. The first segment S1 is located outside the first bending point PB1 in the radial direction. The second segment S2 is located inside the first bending point PB1 in the radial direction. In this embodiment, the first segment S1 is a curve (specifically, a circular arc), and the second segment S2 is a curve (specifically, a circular arc). The first segment S1 is convex outward in the axial direction. The second segment S2 is convex inward in the axial direction. The bending angle θ of the first bending point PB1 is smaller than 180°. This first bending point PB1 is convex outward in the axial direction.

[0049] 5, the arrow HB1 represents the height of the first inflection 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.

[0050] As is clear from Fig. 5, the difference between the height HB1 and the height Hm is slight. The height HB1 substantially coincides with the height Hm. In other words, the radial position of the first bending point PB1 substantially coincides with the radial position of the maximum width point Pm. The heights HB1 and Hm satisfy the following formula. -0.05 ≦ (HB1 - Hm) / Ht ≦ 0.05

[0051] Since the first bend point PB1 is outwardly convex, the thickness of the tire 48 in the vicinity of this first bend point PB1 is large. When the tire 48 flexes, stress is likely to concentrate at the maximum width point Pm. In a tire 48 in which an outwardly convex bend point exists at a position coincident with the position of this maximum width point Pm in the radial direction, distortion is unlikely to concentrate at this maximum width point Pm. This first bend point PB1 suppresses damage that is common in bias tires 48 (peeling between the cord and the topping rubber, peeling between the sidewall 50 and the carcass 54, etc.). This tire 48 has excellent durability despite having a large number of plies.

[0052] From the viewpoint of strain dispersion, 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 segment S1 may be a straight line or an inwardly convex curve. The second segment S2 may be a straight line or an outwardly convex curve. Preferably, the first segment S1 is a straight line or an inwardly convex curve, and the second segment S2 is a straight line or an inwardly convex curve.

[0053] FIG. 6 is an enlarged cross-sectional view showing another part of the pneumatic tire 48 of FIG. 4. FIG. 6 shows a second bending point PB2. The side profile is bent at the second bending point PB2. This second bending point PB2 is sandwiched between a second segment S2 and a third segment S3. The second segment S2 is located outside the second bending point PB2 in the radial direction. The third segment S3 is located inside the second bending point PB2 in the radial direction. In this embodiment, the second segment S2 is a curve (specifically, a circular arc), and the third segment S3 is a curve (specifically, a circular arc). The second segment S2 is convex inward in the axial direction. The third segment S3 is convex inward in the axial direction. The bending angle θ of the second bending point PB2 is smaller than 180°. This second bending point PB2 is convex outward in the axial direction.

[0054] 6, an arrow HB2 represents the height of the second bending point PB2 from the baseline BL, and an arrow HE1 represents the height of the first folded end E1 from the baseline BL. The heights HB2 and HE1 are measured along the radial direction.

[0055] 6, the height HB2 is substantially equal to the height HE1. In other words, the radial position of the second bending point PB2 is substantially equal to the radial position of the first folded end E1. The heights HB2 and HE1 satisfy the following formula. -0.05 ≦ (HB2 - HE1) / Ht ≦ 0.05

[0056] Since the second bending point PB2 is outwardly convex, the thickness of the tire 48 is large in the vicinity of this second bending point PB2. When the tire 48 flexes, stress is likely to concentrate at the folded end. In a tire 48 in which an outwardly convex bending point exists at a position that coincides with the position of this folded end in the radial direction, distortion is unlikely to concentrate at this folded end. This second bending point PB2 suppresses damage that is likely to occur in bias tires 48 (peeling between the cord and the topping rubber, peeling between the sidewall 50 and the carcass 54, etc.). This tire 48 has excellent durability despite having a large number of plies.

[0057] From the viewpoint of strain dispersion, 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 viewpoint of the rigidity of the tire 48, the bending angle θ is preferably 150° or more. The second segment S2 may be a straight line or an outwardly convex curve. The third segment S3 may be a straight line or an outwardly convex curve. Preferably, the second segment S2 is a straight line or an inwardly convex curve, and the third segment S3 is a straight line or an inwardly convex curve.

[0058] FIG. 7 is an enlarged cross-sectional view showing still another part of the pneumatic tire 48 of FIG. 4. FIG. 7 shows a third bending point PB3. The side profile is bent at the third bending point PB3. This third bending point PB3 is sandwiched between a third segment S3 and a fourth segment S4. The third segment S3 is located outside the third bending point PB3 in the radial direction. The fourth segment S4 is located inside the third bending point PB3 in the radial direction. In this embodiment, the third segment S3 is a curve (specifically, a circular arc), and the fourth segment S4 is a straight line. The third segment S3 is convex inward in the axial direction. The bending angle θ of the third bending point PB3 is smaller than 180°. This third bending point PB3 is convex outward in the axial direction.

[0059] 7, an arrow HB3 represents the height of the third bending point PB3 from the baseline BL, and an arrow HE2 represents the height of the second folded end E2 from the baseline BL. The heights HB3 and HE2 are measured along the radial direction.

[0060] 7, the height HB3 is substantially equal to the height HE2. In other words, the radial position of the third bending point PB3 is substantially equal to the radial position of the second folded end E2. The heights HB3 and HE2 satisfy the following formula: -0.05 ≦ (HB3 - HE2) / Ht ≦ 0.05

[0061] Since the third bend point PB3 is outwardly convex, the thickness of the tire 48 is large in the vicinity of this third bend point PB3. When the tire 48 flexes, stress is likely to concentrate at the turned-up end. In a tire 48 in which an outwardly convex bend point exists at a position that coincides with the position of this turned-up end in the radial direction, strain is unlikely to concentrate at this turned-up end. This third bend point PB3 suppresses damage that is likely to occur in bias tires 48 (peeling between the cord and the topping rubber, peeling between the sidewall 50 and the carcass 54, etc.). This tire 48 has excellent durability despite having a large number of plies.

[0062] From the viewpoint of strain dispersion, 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 viewpoint of the rigidity of the tire 48, the bending angle θ is preferably 150° or more. The third segment S3 may be a straight line or an outwardly convex curve. The fourth segment S4 may be an inwardly convex curve or an outwardly convex curve. Preferably, the third segment S3 is a straight line or an inwardly convex curve, and the fourth segment S4 is a straight line or an inwardly convex curve.

[0063] FIG. 8 is an enlarged cross-sectional view showing still another part of the pneumatic tire 48 of FIG. 4. FIG. 8 shows a fourth bending point PB4. The side profile is bent at the fourth bending point PB4. This fourth bending point PB4 is sandwiched between a fourth segment S4 and a fifth segment S5. The fourth segment S4 is located outside the fourth bending point PB4 in the radial direction. The fifth segment S5 is located inside the fourth bending point PB4 in the radial direction. In this embodiment, the fourth segment S4 is a straight line, and the fifth segment S5 is a curved line (specifically, a circular arc). The fifth segment S5 is convex inward in the axial direction. The bending angle θ of the fourth bending point PB4 is smaller than 180°. This fourth bending point PB4 is convex outward in the axial direction.

[0064] 8, an arrow HB4 represents the height of the fourth bending point PB4 from the baseline BL, and an arrow HE3 represents the height of the third folded end E3 from the baseline BL. The heights HB4 and HE3 are measured along the radial direction.

[0065] 8, the height HB4 is substantially equal to the height HE3. In other words, the radial position of the fourth bending point PB4 is substantially equal to the radial position of the third folded end E3. The heights HB4 and HE3 satisfy the following formula: -0.05 ≦ (HB4 - HE3) / Ht ≦ 0.05

[0066] Since the fourth bend point PB4 is outwardly convex, the thickness of the tire 48 is large in the vicinity of this fourth bend point PB4. When the tire 48 flexes, stress is likely to concentrate at the folded end. In a tire 48 in which an outwardly convex bend point exists at a position that coincides with the position of this folded end in the radial direction, distortion is unlikely to concentrate at this folded end. This fourth bend point PB4 suppresses damage that is likely to occur in bias tires 48 (peeling between the cord and the topping rubber, peeling between the sidewall 50 and the carcass 54, etc.). This tire 48 has excellent durability despite having a large number of plies.

[0067] From the viewpoint of strain dispersion, 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 viewpoint of the rigidity of the tire 48, the bending angle θ is preferably 150° or more. The fourth segment S4 may be an inwardly convex curve or an outwardly convex curve. The fifth segment S5 may be a straight line or an outwardly convex curve. Preferably, the fourth segment S4 is a straight line or an inwardly convex curve, and the fifth segment S5 is a straight line or an inwardly convex curve.

[0068] 8, the position of the outer end EF of the filler 58 coincides with the position of the third folded end E3 in the radial direction. Therefore, the height HE3 is also the height HF of the outer end EF. The radial position of the fourth bending point PB4 substantially coincides with the radial position of the outer end EF of the filler 58. The height HB4 and the height HF satisfy the following formula. -0.05 ≦ (HB4 - HF) / Ht ≦ 0.05 The fourth bending point PB4 suppresses damage caused by the third folded end E3 and also suppresses damage caused by the filler 58.

[0069] The position of the outer end EF of the filler 58 may be different from the position of the third turned end E3. In this case, it is preferable that there is a bending point whose radial position substantially coincides with the radial position of the third turned end E3 and that there is a bending point whose radial position substantially coincides with the radial position of the outer end EF.

[0070] 4, the tire 48 does not have a bending point that coincides with the radial position of the fourth turned end E4. The fourth turned end E4 is located axially outward of the bead 52. Therefore, stress is unlikely to concentrate on the fourth turned end E4. Even if there is no bending point that coincides with the radial position of the fourth turned end E4, damage to the fourth turned end E4 can be suppressed.

[0071] In this tire 48, (1) A position that substantially coincides with the position of the outer end EF of the filler 58 (2) A position substantially corresponding to the position of the maximum width point Pm and (3) A position that substantially coincides with the position of the folded end There is a bending point at

[0072] The bending point is (1) A position that substantially coincides with the position of the outer end EF of the filler 58 and (2) A position substantially corresponding to the position of the maximum width point Pm It may be present only in

[0073] The bending point is (1) A position that substantially coincides with the position of the outer end EF of the filler 58 and (3) A position that substantially coincides with the position of the folded end It may be present only in

[0074] In this tire 48, the first turned-up end E1 and the second turned-up end E2 are located radially outward from the outer end EF of the filler 58. The position of the third turned-up end E3 coincides with the outer end EF of the filler 58 in the radial direction. This tire 48 has three turned-up ends (E1, E2, and E3) in a zone that coincides with the outer end EF of the filler 58 in the radial direction or is outside this outer end EF. It is preferable that at least one of the turned-up ends in this zone has a bending point whose radial position coincides with that of the turned-up ends. The number of turned-up ends in this zone that have bending points whose radial positions coincide with that of the turned-up ends is more preferably 2 or more, and particularly preferably 3 or more. It is preferable that each of all turned-up ends in this zone has a bending point whose radial position coincides with that of the turned-up ends.

[0075] The types of side profiles, based on the presence or absence of bending points with the same radial position, are shown below. Maximum width point First folded end Second folded end Third folded end Type 1 Yes No No No Type 2 Yes Yes No No Type 3 Yes No Yes No Type 4 Yes No No Yes Type 5 Yes Yes Yes No Type 6 Yes Yes No Yes Type 7 Yes No Yes Yes Type 8 Yes Yes Yes Yes Type 9 None None None None Type 10 None Yes None None Type 11 No No Yes No Type 12 No No No Yes Type 13 No Yes Yes No Type 14 No Yes No Yes Type 15 No No Yes Yes Type 16 No Yes Yes Yes In either type, it is preferable that there be an inflection point that coincides with the radial position of the outer end EF of the filler 58.

[0076] Ideally, the tire 48 is (1) A position that substantially coincides with the position of the outer end EF of the filler 58 (2) A position substantially corresponding to the position of the maximum width point Pm and (3) a position substantially corresponding to each of the positions of all the winding ends in a zone that is radially coincident with the outer end EF of the filler 58 or is outside this outer end EF All of the above have bending points. EXAMPLES

[0077] The effects of the present invention will be clarified by the following examples, but the present invention should not be construed as being limited based on the description of these examples.

[0078] [Example 1] A tire for a forklift truck shown in Fig. 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-up end, the second ply has a second turned-up end, the third ply has a third turned-up end, and the fourth ply has a fourth turned-up end. The first turned-up end, the second turned-up end, and the third turned-up end are located radially outward from the outer end of the filler. The fourth turned-up end is located axially outward from the bead. The side profile has one bending point. The position of this bending point substantially coincides with the position of the outer end of the filler in the radial direction.

[0079] [Examples 2-9 and Comparative Examples 1-2] Tires of Examples 2-9 and Comparative Examples 1-2 were obtained in the same manner as in Example 1, except that the number and positions of bending points were as shown in Tables 1-3 below.

[0080] [Comparative Example 3] A tire of Comparative Example 3 was obtained in the same manner as in Example 1, except that no bending point was formed in the side profile and a reinforcing layer was inserted in the carcass. This reinforcing layer is similar to the reinforcing layer disclosed in JP 2018-99926 A.

[0081] [Durability] The tire was mounted on a rim of "12x5.00S" and filled with air so that the internal pressure of the tire was 850 kPa. The tire was mounted on a drum-type running test machine and run under the following conditions. Speed: 20km / h Load: 18.69kN Environmental temperature: 25-30℃ The distance traveled until damage occurred to the side of the tire was measured. The results are shown as an index in Table 1-3 below. The higher the value, the greater the distance traveled.

[0082] [cost] The amount of rubber in the tire was calculated. The results are shown as an index in Table 1-3 below. The smaller the value, the less rubber there is.

[0083] [comprehensive evaluation] The ratings were made according to the following criteria: A: Durability is 120 or more and the cost is less than 100 B: Durability is between 110 and 120, and cost is less than 100 C: Durability is less than 110 The results are shown in Tables 1-3 below.

[0084] [Table 1]

[0085] [Table 2]

[0086] [Table 3]

[0087] As shown in Tables 1 to 3, the tires according to the respective examples are excellent in durability. From these evaluation results, the superiority of the present invention is clear. [Industrial Applicability]

[0088] The pneumatic tire according to the present invention can be mounted on various vehicles. [Explanation of symbols]

[0089] 2. 48... Pneumatic tires 4. Tread 6, 50···Sidewall 8, 52... bead 10, 54... Carcass 12. Circuit breaker 18, 56... core 20, 58... Filler 22, 60...First ply 24, 62...Second ply 26, 64...Third ply 28, 66... ​​4th ply 30...First main part 32 First fold 34...Second main section 36 Second fold 38 Third main part 40 Third fold 42 Fourth main part 44 Fourth fold EF: Outer end of filler E1 First folded end E2 Second folded end E3 Third folded end E4 Fourth folded 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 segment S2: Second segment S3: Third segment S4: Fourth segment

Claims

1. A pneumatic tire having a tread, a pair of sidewalls, a pair of beads, and a carcass, Each sidewall extends generally radially inward from an edge of the tread, Each bead is located approximately radially inward from the sidewall, The bead has a core and a filler extending generally radially outward from the core, The carcass is bridged between one bead and the other bead along the inner side of the tread and the sidewall, The carcass has a bias structure, The carcass has a first turned-up end and a second turned-up end located radially inward from the first turned-up end, The pneumatic tire has a pair of side profiles, Each side profile includes three or more axially outwardly convex inflection points; a radial position of one bending point substantially coincides with a radial position of an outer end of the filler; The radial position of the other bending point substantially coincides with the radial position of the second folded end, A pneumatic tire, wherein the radial position of another bending point substantially coincides with the radial position of the first folded end.

2. The carcass has a third turned-up end located radially inward from the second turned-up end, The side profile includes four or more inflection points that are convex axially outward, The pneumatic tire according to claim 1 , wherein a radial position of one bending point substantially coincides with a radial position of the third turn-up end.

3. A pneumatic tire having a tread, a pair of sidewalls, a pair of beads, and a carcass, Each sidewall extends generally radially inward from an edge of the tread, Each bead is located approximately radially inward from the sidewall, The bead has a core and a filler extending generally radially outward from the core, The carcass is bridged between one bead and the other bead along the inner side of the tread and the sidewall, The carcass has a bias structure, the carcass has a turned-up end located radially inward from a maximum width point of the tire, The pneumatic tire has a pair of side profiles, Each side profile includes 3 to 8 inflection points that are convex axially outward; a radial position of one bending point substantially coincides with a radial position of an outer end of the filler; The radial position of the other bending point substantially coincides with the radial position of the folded end, A pneumatic tire in which the radial position of another bending point substantially coincides with the radial position of the maximum width point.

4. Each bending point is sandwiched between two segments on the side profile, 4. The pneumatic tire according to claim 1, wherein each of the segments is a straight line or an axially inwardly convex curve.

5. 5. The pneumatic tire according to claim 1, wherein the bending angle θ of each bending point is 175° or less.

Images