pneumatic tires

Abstract

To provide a pneumatic tire that can reduce weight while ensuring the durability of the bead. [Solution] When the heights of the winding ends of the first carcass ply 41, the second carcass ply 42, the first chafer 71, and the second chafer 72 are H0, H1, H2, and H3, and the heights of the winding ends of the first chafer 71 and the second chafer 72 are H4 and H5, then H1

Description

Technical Field

[0001] The present disclosure relates to pneumatic tires.

Background Art

[0002] In heavy-duty tires used for vehicles with large weights such as light trucks and truck buses, it is important to prevent the occurrence of failures starting from the turn-up ends of carcass plies. Conventionally, for the purpose of improving the durability of the bead portion, a tire provided with a cord reinforcing layer that covers the carcass ply from the inner side in the tire radial direction is known. A tire having such a structure is described in, for example, Patent Document 1. FIG. 4 shows the bead portion of the pneumatic tire described in Patent Document 1.

[0003] As shown in FIG. 4, in the bead portion 90, carcass plies 92 and 93 wound around the bead core 91 from the inner side to the outer side in the tire width direction and chafers 94 and 95 covering it from the inner side in the tire radial direction are provided. Between the bead core 91 and the carcass plies 92 and 93, a reinforcing sheet 96 made of rubber kneaded with cotton is interposed. According to this structure, although the durability of the bead portion 90 is improved by the chafers 94 and 95, there is room for further improvement because it is accompanied by an increase in weight.

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 capable of achieving weight reduction while ensuring the durability of the bead portion.

Means for Solving the Problems

[0006] The pneumatic tire of the present disclosure includes a bead core embedded in a bead portion, and a carcass layer provided with a series of upwardly wound portions wound outward in the tire width direction via the bead core in a main body portion extending from a tread portion through a sidewall portion to the bead portion, and a cord reinforcing layer provided so as to cover the carcass layer from the inner side in the tire radial direction in the bead portion. The carcass layer includes a first carcass ply and a second carcass ply wound upward outside the first carcass ply in the tire width direction. The cord reinforcing layer includes a first chafer and a second chafer wound upward outside the first chafer in the tire width direction. Further, when the heights of the winding ends of the first carcass ply, the second carcass ply, the first chafer, and the second chafer from the nominal rim diameter position are respectively H0, H1, H2, and H3, and the heights of the winding-in ends of the first chafer and the second chafer arranged on the inner side in the tire width direction of the main body portion from the nominal rim diameter position are respectively H4 and H5, H0 to H5 satisfy the following relationships. H1 < H2 < H3 0.5H1 ≤ H0 ≤ 0.7H1 0.5H4 ≤ H5 ≤ 0.7H4 0.9H1 ≤ H4 ≤ 1.1H1 Furthermore, when the thickness from the winding end of the first chafer along the normal direction of the main body portion to the main body portion is T1, the thickness from the winding end of the first chafer along the normal direction of the tire outer surface to the tire outer surface is T2, the thickness from the winding end of the second chafer along the normal direction of the main body portion to the main body portion is T3, and the thickness from the winding end of the second chafer along the normal direction of the tire outer surface to the tire outer surface is T4, T1 to T4 satisfy the following relationships. 1.6T2 ≤ T1 ≤ 1.9T2 1.5T4 ≤ T3 ≤ 1.8T4

Brief Description of the Drawings

[0007] [Figure 1]A schematic diagram of a tire meridian half-section illustrating an example of the pneumatic tire of this disclosure. [Figure 2] A cross-sectional view showing an enlarged view of the bead portion in Figure 1. [Figure 3] A schematic diagram showing the area around the winding section as viewed from the outside in the tire width direction. [Figure 4] Cross-sectional view showing the bead portion of a pneumatic tire as described in Patent Document 1 [Modes for carrying out the invention]

[0008] Embodiments of the pneumatic tire of this disclosure will be described with reference to the drawings.

[0009] As shown in Figures 1 and 2, the pneumatic tire PT of this embodiment comprises a pair of bead portions 1, a pair of sidewall portions 2 extending radially outward from each of the pair of bead portions 1, and a tread portion 3 connected to the radially outward ends of each of the pair of sidewall portions 2. A bead core 11 and a bead filler 12 are embedded in the bead portion 1. The bead core 11 is formed by winding a wire 11a (see Figure 3), such as steel wire, in a ring shape. The bead filler 12 is formed of triangular-shaped rubber extending radially outward from the bead core 11.

[0010] Here, the tire radial direction is the direction along the diameter of the tire PT. The side closer to the central axis (axis of rotation) of the tire PT is the inner side in the tire radial direction, and the side further away from the central axis of the tire PT is the outer side in the tire radial direction. The tire circumferential direction is the direction around the central axis of the tire PT. The tire width direction is the direction parallel to the central axis of the tire PT. The side closer to the tire equator TE is the inner side in the tire width direction, and the side further away from the tire equator TE is the outer side in the tire width direction. The tire equator TE is located at the center of the tire PT in the tire width direction and is perpendicular to the central axis of the tire PT when viewed from the outside in the tire radial direction.

[0011] The tire PT comprises a toroidal carcass layer 4 between a pair of bead portions 1. The carcass layer 4 is composed of two carcass plies (a first carcass ply 41 and a second carcass ply 42, described later) that are laminated together. The carcass plies are formed by covering cords 4C (see Figure 3), which are arranged in a direction substantially perpendicular to the tire circumferential direction (for example, at an angle of 80 to 90 degrees), with rubber. Organic fiber cords such as polyester, rayon, nylon, and aramid, or metal cords such as steel are preferably used for the cords 4C.

[0012] On the outer side of the carcass layer 4 in the tire width direction, a rim strip rubber 10 is provided to form the outer surface of the bead portion 1, and a sidewall rubber 20 is provided to form the outer surface of the sidewall portion 2. On the outer side of the carcass layer 4 in the tire radial direction, a tread rubber 30 is provided to form the outer surface of the tread portion 3. A belt layer 5 reinforcing the carcass layer 4 is embedded in the tread portion 3. Although not shown in the figure, various grooves forming a tread pattern are provided on the outer circumferential surface of the tread portion 3. On the inner surface of the tire, an inner liner rubber 6 made of rubber with excellent air shielding properties is provided.

[0013] The carcass layer 4 is turned up (rolled up) around the bead core 11 from the inside to the outside in the tire width direction. The carcass layer 4 has a main body portion 4b that extends from the tread portion 3 through the sidewall portion 2 to the bead portion 1, and a rolled-up portion 4t that is rolled up outwards in the tire width direction via the bead core 11. The bead core 11 and the bead filler 12 are sandwiched between the main body portion 4b and the rolled-up portion 4t, respectively. Figure 3 schematically shows the area around the rolled-up portion 4t as seen from the outside in the tire width direction, and the bead filler 12 and main body portion 4b are not shown.

[0014] The tire PT includes a cord reinforcement layer 7 provided in the bead portion 1 so as to cover the carcass layer 4 from the inside in the tire radial direction. The cord reinforcement layer 7 is wound up from the inside to the outside in the tire width direction around the carcass layer 4 in the bead portion 1. The cord reinforcement layer 7 is composed of two chafers (a first chafer 71 and a second chafer 72, described later) that are laminated together. The chafer is formed by covering cords 7C arranged in a direction intersecting the tire circumferential direction (for example, a direction forming an angle of 30 to 50 degrees) with rubber. Organic fiber cords such as nylon, rayon, polyester, and aramid are preferably used for the cords 7C.

[0015] As shown in an enlarged view in Figure 2, the carcass layer 4 includes a first carcass ply 41 and a second carcass ply 42 that is wound up on the outside in the tire width direction of the first carcass ply 41. The second carcass ply 42 is located on the outside in the tire width direction of the first carcass ply 41 in the wound-up portion 4t, and on the inside in the tire width direction of the first carcass ply 41 in the main body portion 4b of the bead portion 1. The first carcass ply 41 and the second carcass ply 42 each have wound-up ends 41a and 42a that are located on the outside in the tire width direction of the main body portion 4b.

[0016] The cord reinforcement layer 7 includes a first chafer 71 and a second chafer 72 wound up on the tire width direction outward of the first chafer 71. The second chafer 72 is located on the tire width direction outward of the first chafer 71 in the portion wound up along the winding section 4t, and on the tire width direction inward of the first chafer 71 in the portion wound up along the main body 4b. The first chafer and the second chafers 71 and 72 each have winding ends 71a and 72a located on the tire width direction outward of the main body 4b, and winding ends 71b and 72b located on the tire width direction inward of the main body 4b.

[0017] The nominal rim diameter position Pr is the position of the nominal rim diameter (the nominal size of the rim) of the regular rim described later. In the tire PT of the present embodiment, the heights of the turn-up ends 41a, 42a, 71a, and 72a of the first carcass ply 41, the second carcass ply 42, the first chafer 71, and the second chafer 72 from the nominal rim diameter position Pr are respectively H0, H1, H2, and H3, and the heights of the turn-in ends 71b and 72b of the first chafer 71 and the second chafer 72 from the nominal rim diameter position Pr are respectively H4 and H5. When H0 to H5 satisfy the following relationships. H1 < H2 < H3 (1) 0.5H1 ≤ H0 ≤ 0.7H1 (2) 0.5H4 ≤ H5 ≤ 0.7H4 (3) 0.9H1 ≤ H4 ≤ 1.1H1 (4)

[0018] Furthermore, in the tire PT of the present embodiment, the thickness from the turn-up end 71a of the first chafer 71 along the normal direction of the main body portion 4b to the main body portion 4b is T1, the thickness from the turn-up end 71a of the first chafer 71 along the normal direction of the outer surface of the tire to the outer surface of the tire is T2, the thickness from the turn-up end 72a of the second chafer 72 along the normal direction of the main body portion 4b to the main body portion 4b is T3, and the thickness from the turn-up end 72a of the second chafer 72 along the normal direction of the outer surface of the tire to the outer surface of the tire is T4. When T1 to T4 satisfy the following relationships. 1.6T2 ≤ T1 ≤ 1.9T2 (5) 1.5T4 ≤ T3 ≤ 1.8T4 (6)

[0019] There are four turn-up ends 41a, 42a, 71a, and 72a and two turn-in ends 71b and 72b arranged in the bead portion 1. Since these member ends are all locations where distortion tends to concentrate, it is important to sufficiently separate them from each other in order to enhance the durability of the bead portion 1. However, if they are separated from each other too much, distortion tends to concentrate instead. Therefore, in the present embodiment, a configuration that satisfies the relationships (1) to (6) above is adopted, thereby achieving weight reduction while ensuring the durability of the bead portion 1.

[0020] First, in the tire PT of this embodiment, by satisfying the relationships of (1) and (2) above, the winding ends 41a, 42a, 71a, and 72a are arranged in this order in stages toward the outer radial direction of the tire. As a result, the winding end 41a is covered by the second carcass ply 42, the winding end 42a is covered by the first chafer 71, and the winding end 71a is covered by the second chafer 72, each from the outside in the tire width direction. This structure helps to suppress the occurrence of cracks and the like starting from the winding ends 41a, 42a, and 71a.

[0021] Next, by satisfying the relationship in (2) above, the step between the winding end 41a and the winding end 42a (the distance in the radial direction of the tire between the member ends) is set to an appropriate size. By satisfying the relationship H0 ≤ 0.7H1, the winding end 41a is sufficiently separated from the winding end 42a, thereby suppressing the concentration of strain that occurs between them. Furthermore, by satisfying the relationship 0.5H1 ≤ H0, the structure is such that the winding end 41a is not separated too far from the winding end 42a, which is suitable for ensuring the durability of the bead portion 1.

[0022] Similarly, by satisfying the relationship in (3) above, the step between the winding end 71b and the winding end 72b is set to an appropriate size. By satisfying the relationship H5 ≤ 0.7H4, the winding end 72b can be sufficiently separated from the winding end 71b, thereby suppressing the concentration of strain that occurs between them. Furthermore, by satisfying the relationship 0.5H4 ≤ H5, the structure is such that the winding end 72b is not separated too far from the winding end 71b, which is suitable for ensuring the durability of the bead portion 1.

[0023] Moreover, by satisfying the relationship in (4) above, unlike the configuration shown in Figure 4, the height H4 of the winding end 71b is set to be approximately the same as the height H1 of the winding end 42a. As previously described, the height H5 of the winding end 72b is set to be smaller than the height H4 of the winding end 71b. With this configuration, the increase in weight can be suppressed without significantly impairing the reinforcing effect of the cord reinforcing layer 7. As heights H4 and H5 are thus suppressed, the effect of reducing material costs can also be obtained.

[0024] Furthermore, by satisfying the relationships in (5) and (6) above, the thicknesses T1 and T3 are set to an appropriate size. By satisfying the relationships 1.6T2≦T1 and 1.5T4≦T3, the distance between the winding ends 71a and 72a and the main body 4b is ensured, and the concentration of strain occurring at the winding ends 71a and 72a can be suppressed. In addition, by satisfying the relationships T1≦1.9T2 and T3≦1.8T4, the thicknesses T1 and T3 do not become excessively large, thus suppressing an increase in weight (which also has the effect of reducing material costs).

[0025] As shown in Figure 3, the first chafer 71 and the second chafer 72 each contain cords 7C extending in a direction inclined with respect to the tire circumferential direction, and the cords 7C are laminated between them so as to intersect each other in opposite directions. With this configuration, the rigidity of the bead portion 1 is increased by the effect of the cord reinforcement layer 7. Therefore, in a tire PT where the heights H4 and H5 are set relatively low as described above, the durability of the bead portion 1 can be effectively improved. However, this is not the only option, and a structure in which the cords 7C extend in the same direction between the chafers is also acceptable.

[0026] In this embodiment, H0 and H5 may have structures that satisfy the following relationship. 0.9H0≦H5≦1.1H0 (7) By satisfying the relationship in (7) above, unlike the configuration shown in Figure 4, the height H5 of the winding end 72b is set to be approximately the same as the height H0 of the winding end 41a. From the viewpoint of enhancing the effect of improving the durability of the bead portion 1, it is preferable to satisfy the relationship H0 ≤ H5. Similarly, from the viewpoint of enhancing the effect of improving the durability of the bead portion 1, it is preferable to satisfy the relationship H1 ≤ H4.

[0027] In this embodiment, the winding end 41a of the first carcass ply 41 and the winding end 72b of the second chafer 72 are both positioned radially outward from the outer diameter position of the bead core 11. This configuration is suitable for ensuring the durability of the bead portion 1. In addition, in this embodiment, the winding end 72a of the second chafer 72 is positioned radially inward from the radially outer end of the bead filler 12. This configuration is suitable for suppressing the weight increase caused by the cord reinforcement layer 7.

[0028] In this embodiment, when the tire section height is TH, the structure may satisfy the following relationship between H1 and TH. 0.1TH ≤ H1 ≤ 0.25TH (8) By satisfying the relationship in (8) above, the height H1 of the winding end 42a is set to an appropriate size. The tire section height TH is determined as the height from the nominal rim diameter position Pr to the outermost tire diameter position Pm. The outermost tire diameter position Pm is usually located on the tire equator TE. If a groove is provided on the tire equator TE, the outermost tire diameter position Pm is determined based on the virtual outer surface that fills the groove.

[0029] In this embodiment, H1 to H3 may have a structure that satisfies the following relationships (9) and (10). 1.2H1 ≤ H2 ≤ 1.5H1 (9) 1.6H1 ≤ H3 ≤ 1.9H1 (10) By satisfying the relationships in (9) and (10) above, the steps between the winding end 42a and the winding end 71a, and the steps between the winding end 71a and the winding end 72a are set to an appropriate size. Steps determined by "H1-H0", "H2-H1", "H3-H2", and "H4-H5" are formed in the carcass layer 4 and the cord reinforcement layer 7, and it is preferable that each of these four steps is 10 mm or more.

[0030] When T5 is the thickness from the winding end 42a of the second carcass ply 42 along the normal direction of the main body 4b to the main body 4b, and T6 is the thickness from the winding end 42a of the second carcass ply 42 along the normal direction of the outer surface of the tire to the outer surface of the tire, the structure in which T5 and T6 satisfy the relationship (11) below is also acceptable. 1.2T6≦T5≦1.5T6 (11) By satisfying the relationship in (11) above, the thickness T5 is set to an appropriate size. By satisfying the relationship 1.2T6≦T5, the distance between the winding end 42a and the main body 4b is secured, and the concentration of strain occurring at the winding end 42a can be suppressed. In addition, by satisfying the relationship T5≦1.5T6, the thickness T5 does not become excessively large, so the increase in weight can be suppressed (and the effect of reducing material costs can also be obtained).

[0031] In this embodiment, there are no other reinforcing layers, such as the reinforcing sheet 96 shown in Figure 4. In other words, the first carcass ply 41 is in direct contact with the bead core 11 without any other reinforcing layers interposed therebetween. This configuration is advantageous for reducing weight. Furthermore, this configuration is advantageous for securing each step of the winding ends 41a, 42a, 71a, and 72a. In contrast, if other reinforcing layers are interposed, it may become difficult to secure each step of the winding ends 41a, 42a, 71a, and 72a in relation to the member end on that reinforcing layer.

[0032] As shown in Figure 3, the bead core 11 has a structure in which a ring-shaped wire 11a is wrapped in a bead cover 11b. The bead cover 11b is a tape-like member formed by covering an organic fiber cord with rubber, and is spirally wrapped around the outer surface of the wire 11a. With this configuration, even in a structure that does not interpose other reinforcing layers such as the reinforcing sheet 96 shown in Figure 4, damage to the carcass layer 4 (especially the first carcass ply 41) caused by friction with the bead core 11 can be suppressed, and consequently the durability of the bead portion 1 can be ensured.

[0033] The tire dimensions and positional relationships described above are based on the standard unloaded condition, with the tire mounted on a standard rim and filled to the standard pressure, unless otherwise specified. A standard rim is the rim defined for each tire by each standard within the tire standard system, including the standard on which the tire is based. For example, JATMA uses "standard rim," and TRA and ETRTO use "measuring rim." Standard pressure is the air pressure defined for each tire by each standard within the tire standard system, including the standard on which the tire is based. For JATMA, it is "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is "INFLATION PRESSURE." For passenger car tires, it is usually 180kPa, but for tires marked "Extra Load" or "Reinforced," it is 220kPa.

[0034] The structure of the bead portion 1 described above only needs to be applied to at least one of the pair of bead portions 1, but from the viewpoint of enhancing the improvement effect, it is preferable that it be applied to both of the pair of bead portions 1. [Examples]

[0035] To specifically illustrate the configuration and effects of the above-described embodiment, we conducted evaluation tests on the durability and weight of the bead portion using a pneumatic radial tire for light trucks (tire size: 205 / 80R17.5), and will now explain the results.

[0036] [Durability of the bead] A tire mounted on a rim was pressed against a steel drum with a load of 70% of the JATMA standard load, and the drum was driven at a constant speed of 65 km / h. The load was increased by 18% every 24 hours, and the time until the bead broke was measured. The results for Comparative Example 1 are expressed as an index with 100, and a higher number indicates better bead durability.

[0037] [weight] The weight of the molded tires was measured. The result for Comparative Example 1 is expressed as an index with 100, where a smaller number indicates a smaller weight.

[0038] Comparative Examples 1-4 and Examples 1-4 In the bead section having the structure shown in Figure 1, the heights H4, H5 and thicknesses T1, T3, T5 were varied as shown in Table 1 to form Comparative Examples 1-4 and Examples 1-4. However, Comparative Example 2 does not have a wrapped end because each chafer is wrapped outward from the bead heel in the radial direction of the tire. In Comparative Examples 1-4, the cords extend in the same direction between the chafers. Aside from these configurations, the tire structure (including heights H0-H3 and cross-sectional height TH) is common to each example, and all satisfy the relationships in (1) and (2) above. The evaluation results are shown in Table 1.

[0039] [Table 1]

[0040] As shown in Table 1, in Examples 1 to 4, weight reduction was achieved while ensuring the durability of the bead portion.

[0041] Those skilled in the art will understand that the embodiments described above are specific examples of the following embodiments.

[0042] [1] The pneumatic tire of the present disclosure includes a bead core embedded in a bead portion, and a carcass layer provided in a main body portion extending from a tread portion through a sidewall portion to the bead portion, with a series of winding-up portions wound outward in the tire width direction via the bead core, and a cord reinforcing layer provided in the bead portion so as to cover the carcass layer from the inner side in the tire diameter direction. The carcass layer includes a first carcass ply and a second carcass ply wound outward in the tire width direction of the first carcass ply. The cord reinforcing layer includes a first chafing and a second chafing wound outward in the tire width direction of the first chafing. Also, when the heights from the nominal rim diameter position of the winding-up ends of the first carcass ply, the second carcass ply, the first chafing, and the second chafing are respectively H0, H1, H2, and H3, and the heights from the nominal rim diameter position of the winding-in ends of the first chafing and the second chafing disposed on the inner side in the tire width direction of the main body portion are respectively H4 and H5, H0 to H5 satisfy the following relationships. H1 < H2 < H3 0.5H1 ≤ H0 ≤ 0.7H1 0.5H4 ≤ H5 ≤ 0.7H4 0.9H1 ≤ H4 ≤ 1.1H1 Furthermore, when the thickness from the winding-up end of the first chafing along the normal direction of the main body portion to the main body portion is T1, the thickness from the winding-up end of the first chafing along the normal direction of the tire outer surface to the tire outer surface is T2, the thickness from the winding-up end of the second chafing along the normal direction of the main body portion to the main body portion is T3, and the thickness from the winding-up end of the second chafing along the normal direction of the tire outer surface to the tire outer surface is T4, T1 to T4 satisfy the following relationships. 1.6T2 ≤ T1 ≤ 1.9T2 1.5T4 ≤ T3 ≤ 1.8T4 According to such a configuration, weight reduction can be achieved while ensuring the durability of the bead portion.

[0043] [2] In the pneumatic tire described in [1] above, the first chafer and the second chafer may each include cords extending in a direction inclined with respect to the circumferential direction of the tire, and the cords may be laminated between them such that they intersect in opposite directions. With such a configuration, the rigidity can be increased by the effect of the cord reinforcement layer, thereby improving the durability of the bead portion.

[0044] [3] In the pneumatic tire described in [1] or [2] above, H0 and H5 may satisfy the following relationship. 0.9H0≦H5≦1.1H0 This sets the height H5 of the winding end of the second chafer to be approximately the same as the height H0 of the winding end of the first carcass ply.

[0045] [4] In any one of the above [1] to [3] pneumatic tires, when the tire section height is TH, H1 and TH may satisfy the following relationship. 0.1TH ≤ H1 ≤ 0.25TH This sets the height H1 of the winding end of the second carcass ply to an appropriate size.

[0046] [5] In any one of the above [1] to [4] pneumatic tires, H1 to H3 must satisfy the following relationship. 1.2H1 ≤ H2 ≤ 1.5H1 1.6H1 ≤ H3 ≤ 1.9H1 This sets the step between the winding end of the second carcass ply and the winding end of the first chafer, and the step between the winding end of the first chafer and the winding end of the second chafer, to an appropriate size.

[0047] [6] In any one of the pneumatic tires described in [1] to [5] above, the first carcass ply may be in direct contact with the bead core without the interposition of any other reinforcing layers. This configuration makes it easier to secure each step of the winding end while reducing weight.

[0048] The pneumatic tire of this disclosure is useful as a heavy-duty tire used in light trucks, trucks, buses, etc., because the durability of the bead portion can be ensured by the above-described configuration.

[0049] The pneumatic tire of this disclosure can be constructed in the same way as a normal pneumatic tire, except for the bead portion being configured as described above, and any conventionally known materials, shapes, structures, and manufacturing methods can be used.

[0050] This disclosure is not limited in any way to the embodiments described above, and various improvements and modifications are possible without departing from its essence. Furthermore, the configurations adopted in the embodiments described above can be adopted in any combination. [Explanation of Symbols]

[0051] 1 Bead section, 4 Carcass layer, 4b Main body section, 4t Wrap-around section, 7 Cord reinforcement layer, 7C Cord, 11 Bead core, 41 First carcass ply, 41a Wrap-around end of first carcass ply, 42 Second carcass ply, 42a Wrap-around end of second carcass ply, 71 First chafer, 71a Wrap-around end of first chafer, 71b Wrap-in end of first chafer, 72 Second chafer, 72a Wrap-around end of second chafer, 72b Wrap-in end of second chafer, PT Pneumatic tire

Claims

1. The bead core embedded in the bead section, The main body portion, extending from the tread portion through the sidewall portion to the bead portion, has a carcass layer in which a series of winding portions are provided that are wound up outward in the tire width direction via the bead core, The bead portion comprises a cord reinforcing layer provided so as to cover the carcass layer from the inside in the radial direction of the tire, The carcass layer includes a first carcass ply and a second carcass ply that is wound up on the tire width side of the first carcass ply. The cord reinforcement layer includes a first chafer and a second chafer wound up on the tire width direction outward from the first chafer. When the heights of the winding ends of the first carcass ply, the second carcass ply, the first chafer, and the second chafer from the nominal rim diameter position are H0, H1, H2, and H3, respectively, and the heights of the winding ends of the first chafer and the second chafer, which are located on the inside of the main body in the tire width direction, from the nominal rim diameter position are H4 and H5, respectively, then H0 to H5 satisfy the following relationship: H1 < H2 < H3 0.5H1≦H0≦0.7H1 0.5H4≦H5≦0.7H4 0.9H1≦H4≦1.1H1 A pneumatic tire in which T1 to T4 satisfy the following relationship, where T1 is the thickness from the winding end of the first chafer along the normal direction of the main body to the main body, T2 is the thickness from the winding end of the first chafer along the normal direction of the outer surface of the tire to the outer surface of the tire, T3 is the thickness from the winding end of the second chafer along the normal direction of the main body to the main body, and T4 is the thickness from the winding end of the second chafer along the normal direction of the outer surface of the tire to the outer surface of the tire. 1.6T2≦T1≦1.9T2 1.5T4≦T3≦1.8T4

2. The pneumatic tire according to claim 1, wherein the first chafer and the second chafer each include cords extending in a direction inclined with respect to the circumferential direction of the tire, and the cords are stacked between them such that they intersect each other in opposite directions.

3. The pneumatic tire according to claim 1, wherein H0 and H5 satisfy the following relationship. 0.9H0≦H5≦1.1H0

4. The pneumatic tire according to claim 1, wherein when the tire section height is TH, H1 and TH satisfy the following relationship. 0.1TH≦H1≦0.25TH

5. The pneumatic tire according to claim 1, wherein H1 to H3 satisfy the following relationship. 1.2H1≦H2≦1.5H1 1.6H1≦H3≦1.9H1

6. The pneumatic tire according to any one of claims 1 to 5, wherein the first carcass ply is in direct contact with the bead core without the interposition of any other reinforcing layers.

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