CN104723804B - Pneumatic radial tire - Google Patents

Abstract

An object of the present invention is to improve the durability of the bead portion while suppressing the increase in tire mass and the occurrence of air holes. The pneumatic radial tire is provided with: a fiber reinforcement layer provided outside the turn-up portion of the carcass ply; a metal reinforcement layer provided between the turn-up portion and the fiber-reinforcement layer; and a rubber pad interposed between the bead filler strip It is arranged between the fiber reinforced layer, where the distance from the lower end of the rubber pad to the upper end of the metal reinforced layer is taken as H0, the distance from the upper end of the metal reinforced layer to the rolled-up end of the ply is taken as H1, and the distance from the rolled-up end to the fiber The distance from the upper end of the reinforced layer is H2, the distance between the upper ends of the fiber reinforced layers is H3, and the distance from the upper end of the rubber pad to the upper end of the fiber reinforced layer is H4, set as: H1/H0=0.80-1.0; H2/H4= 0.60‑0.90; H3/H4＝0.80‑1.0; both H0 and H1 are greater than any one of H2 and H4.

Description

Pneumatic radial tire

technical field

The invention relates to a pneumatic radial tire.

Background technique

In a pneumatic radial tire, particularly a pneumatic radial tire for heavy loads, it is necessary to improve the durability of the bead portion. In order to improve the durability of the bead portion, it is effective to reduce the strain at the turn-up end of the carcass by suppressing the deformation of the bead portion. Therefore, generally, a reinforcing layer called a chafer is provided along the turned-up portion of the carcass (see Patent Document 1).

Patent Document 2 discloses that as such a reinforcing layer, a steel cord reinforcing layer containing steel cords and a fiber cord reinforcing layer containing organic fibers are provided, and the upper end of the steel cord reinforcing layer is lower than the cord. The rolled up end of the layer, and the upper end of the fiber cord reinforced layer is higher than the rolled up end, on this basis, the rubber compound is arranged inside the fiber cord reinforced layer. Patent Document 3 also discloses that, as the reinforcing layer of the bead portion, a cord reinforcing layer including steel cords and an additional cord layer including fiber cords are provided.

Prior art literature:

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2013-1223

Patent Document 2: Japanese Patent Laid-Open No. 63-110006

Patent Document 3: Japanese Patent Application Laid-Open No. 8-324214

Contents of the invention

The problem to be solved by the invention

As described above, by providing reinforcement around the turned-up portion of the carcass by providing a metal reinforcement layer including steel cords and a fiber-reinforced layer including organic fiber cords, the strain at the turned-up end of the carcass can be dispersed. , thereby improving the durability of the bead portion. However, providing a plurality of reinforcing layers in this way reduces the interval between the ends of the members. Therefore, air is easily entrapped in the tire manufacturing process, and air holes are easily generated in the vulcanized tire. On the other hand, although the occurrence of air pockets can be suppressed by increasing the distance between the ends of the members, the increase in the distance between the ends of the members tends to increase the thickness of the bead portion and cause tire deformation. main reason for the weight.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic radial tire capable of suppressing increase in tire mass, suppressing generation of air holes, and improving durability of bead portions.

Solution to the problem

The pneumatic radial tire according to Embodiment 1 includes: a bead core embedded in the bead portion; a bead filler disposed outside the bead core in the tire radial direction; wrapping the bead core inwardly and rolling outwardly; at least one fiber-reinforced layer comprising organic fiber cords disposed outside the rolled-up portion of the carcass; a metal reinforcing layer comprising a metal cord between the turn-up portion and the fiber-reinforced layer; and a rubber pad for covering the turn-up end of the carcass ply from the tire axially outer side and interposed between the beads The filler strip is arranged between the fiber reinforced layer. On the outer side in the tire axial direction of the bead core, the upper end of the metal reinforcement layer is located closer to the inner side of the tire radial direction than the turn-up end, and the upper end of the fiber-reinforced layer is located further inward than the turn-up end. The upper end of the rubber pad is located closer to the outer side of the tire radial direction than the upper end of the fiber reinforced layer, and the lower end of the rubber pad is between the rolled part and the metal reinforcement. between layers. And, the tire radial distance from the lower end of the rubber pad to the upper end of the metal reinforcement layer is taken as H0, the tire radial distance from the upper end of the metal reinforcement layer to the rolled-up end is taken as H1, and the The tire radial distance from the rolled-up end to the upper end of the fiber-reinforced layer having the closest upper end in the tire radial direction is H2, and the distance from the upper end of the rubber pad to the fiber-reinforced layer having the closest upper end in the tire radial direction The tire radial distance of the upper end is H4, H1/H0 is 0.80-1.0, H2/H4 is 0.60-0.90, and both H0 and H1 are larger than any one of H2 and H4.

Regarding the pneumatic radial tire according to the second embodiment, in the above-mentioned first embodiment, at least two fiber-reinforced layers are provided, and the distance in the tire radial direction between the upper ends of the at least two fiber-reinforced layers is H3, H1/H0 is 0.80-1.0, H2/H4 is 0.60-0.90, H3/H4 is 0.80-1.0, and both H0 and H1 are larger than any one of H2, H3 and H4.

Regarding the pneumatic radial tire according to Embodiment 3, in Embodiment 1 or 2, the rubber pad is formed in such a manner that the part closer to the outer side in the tire radial direction than the turn-up end is closer to the radial direction. The thickness gradually becomes thinner towards the outside.

Regarding the pneumatic radial tire of Embodiment 4, in any one of Embodiments 1 to 3, the bead filler includes: a lower side filler that surrounds the bead core; and an upper side filler strip, which is arranged on the outer side of the tire radial direction of the lower side filler strip, and the rubber hardness is lower than that of the lower side filler strip, and the rubber hardness of the rubber pad is lower than that of the lower side filler strip. The rubber hardness of the side filler rubber strips, and the rubber hardness of the rubber pad is equal to or higher than that of the upper side filler rubber strips.

With respect to the pneumatic radial tire of Embodiment 5, in Embodiment 4, the lower end of the rubber pad is located in the axial direction of the tire relative to the interface between the lower rubber filler and the upper rubber filler. The outer end is closer to the inner side in the tire radial direction.

Regarding the pneumatic radial tire according to Embodiment 6, in Embodiment 4 or 5, a pad is arranged on the outer side of the bead filler in the tire axial direction, and the pad is sandwiched between the Between the gasket and the upper rubber filling strip, the rubber hardness of the gasket is equal to or higher than that of the upper rubber filling strip.

In the pneumatic radial tire of Embodiment 7, in any one of Embodiments 1-6, H1/H2 is 1.3-1.8.

The effect of the invention

According to the present embodiment, it is possible to suppress an increase in tire mass, suppress the occurrence of air holes, and improve the durability of the bead portion.

Description of drawings

Fig. 1 is a half sectional view showing a pneumatic radial tire of a first embodiment.

Fig. 2 is a cross-sectional view showing a bead portion of the pneumatic radial tire of the first embodiment.

Fig. 3 is an enlarged cross-sectional view showing a part of the bead portion.

Fig. 4 is a sectional view showing a bead portion of a pneumatic radial tire of a second embodiment.

Fig. 5 is a sectional view showing a bead portion of a pneumatic radial tire of a third embodiment.

6 is a cross-sectional view showing a bead portion of a pneumatic radial tire of a comparative example.

Explanation of reference signs

10 pneumatic radial tires

12, 12A, 12B bead part

18 plies

18B roll up part

18E Coiled end

26 bead core

28 bead filler

32 fiber reinforced layers,

32A First fiber reinforced layer

32AE upper end

32B Second fiber reinforced layer

32BE upper end

32C fiber reinforced layer

34 metal reinforcement layer

34E upper end

38 pads

38A upper end

38B lower end

40 Lower filler strips

42 Filling strips on the upper side

44 interface

44A Axial outer end of tire

detailed description

(first embodiment)

FIG. 1 shows a pneumatic radial tire 10 according to a first embodiment, showing a half cross-sectional view in a state of being mounted on a predetermined rim 1 .

When mounted on a specified rim, it means that the tire is mounted on a specified rim determined according to the specification corresponding to the tire size, and is filled with a normal internal pressure determined according to the specification corresponding to the same tire size, and is in a no-load state. Here, the standard rim refers to, for example, "standard rim" in the JATMA standard, "Design Rim" in the TRA standard, and "Measuring Rim" in the ETRTO standard. In addition, the normal internal pressure refers to, for example, the "maximum air pressure" corresponding to the maximum load capacity of a single wheel in the JATMA standard, the "maximum value" described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, ETRTO "INFLATION PRESSURE" in the specifications. The rim is not shown in Figs. 2-6, and the dimension setting of this embodiment is based on the shape when it is mounted on a predetermined rim.

In this specification, the tire axial direction refers to a direction parallel to the tire rotation axis, which has the same meaning as the tire width direction, and is indicated by a reference symbol Y in the drawings. In addition, the tire radial direction (the meridian direction) refers to a direction perpendicular to the tire rotation axis, and is indicated by a reference sign Z in the drawings.

The tire 10 of the embodiment includes: a pair of left and right bead portions 12; a pair of sidewall portions 14 extending outward in the tire radial direction from the bead portions 12; The radially outer end portions are disposed between the two sidewall portions 14 in such a manner as to each other.

A carcass layer 18 is buried inside the tire 10 , and the carcass layer 18 extends between the pair of bead portions 12 . The carcass layer 18 extends from the tread portion 16 through the sidewall portion 14 , and both ends thereof are engaged with the bead portion 12 . A belt layer 20 is provided on the outer peripheral side of the carcass 18 of the tread portion 16 for reinforcing the tread portion 16 at the outer periphery of the carcass 18 . The carcass 18 is formed by covering ply cords with a topping rubber, and the ply cords are arranged in a direction substantially perpendicular to the tire circumferential direction. Steel cords and organic fiber cords are used as the ply cords.

Inside the carcass 18 is provided an inner liner 22 as an air-permeable rubber layer constituting the inner peripheral surface of the tire 10 . In addition, in the sidewall portion 14 , a sidewall rubber 24 for constituting the outer wall surface of the tire 10 is provided on the outer side of the carcass layer 18 .

As shown enlarged in FIG. 2 , embedded in the bead portion 12 are: an annular bead core 26 composed of a cluster formed by winding rubber-coated bead wires in layers; The bead filler strip 28 made of the present invention is arranged on the outer side of the bead core 26 in the tire radial direction.

The carcass layer 18 wraps around the bead core 26 from the inner side in the tire axial direction and is rolled outward. Specifically, in the carcass 18 , the main body portion 18A extending from the sidewall portion 14 is arranged along the axially inner side surface of the bead core 26 and the bead filler 28 , and passes through the bead core 26 . Roll the underside out (ie, fold back). The turn-up portion 18B is arranged along the axially outer side surfaces of the bead core 26 and the bead filler 28 , and its tip (ie, the upper end of the turn-up portion 18B) becomes a turn-up end 18E. In addition, reference numeral 30 denotes an edge tape for wrapping the rolled-up end 18E.

Around the carcass 18 of the bead portion 12 are provided: a fiber reinforcement layer 32 including organic fiber cords; and a metal reinforcement layer 34 including metal cords. Specifically, a fiber-reinforced layer 32 is provided outside the turn-up portion 18B of the carcass 18 (that is, outside in the tire axial direction), and a metal-reinforced layer 34 is provided between the turn-up portion 18B and the fiber-reinforced layer 32 . .

In the present embodiment, the metal reinforcing layer 34 is a steel chafer using a steel cord as a metal cord, which is formed by covering the steel cord with a topping rubber, which is relatively strong to the tire. The circumferential direction is arranged obliquely at an inclination angle of, for example, 20°-50°. The metal reinforcement layer 34 is provided along the outer surface of the turn-up portion 18B so as to reinforce the turn-up portion 18B of the carcass 18 from the outside. In this example, the metal reinforcing layer 34 is provided on the outer surface of the carcass 18 so as to wrap around the carcass 18 in the bead portion 12 . That is, the metal reinforcement layer 34 wraps around the carcass 18 from the inner side in the tire axial direction and is rolled outward, and is adjacent to the main body portion 18A of the carcass 18 on the inner side of the bead core 26 in the tire axial direction, and is provided along the inner surface thereof. , and adjacent to the turn-up portion 18B on the outer side in the tire axial direction of the bead core 26 and provided along the outer side surface thereof.

In addition, the metal reinforcement layer 34 is not limited to wrapping the carcass 18 from the inside and being rolled outward as shown in FIG. 2 , and may be rolled up from a position inside the bead core 26 in the tire radial direction. In FIG. 2 , reference numeral 36 denotes edge strips installed at both ends of the metal reinforcement layer 34 , respectively.

The fiber-reinforced layer 32 is a reinforcing layer using, for example, nylon fiber cords as organic fiber cords, which are formed by covering the organic fiber cords with a topping rubber with respect to the tire circumferential direction by, for example, The inclination angle of 20°-50° is arranged obliquely. The fiber-reinforced layer 32 is provided on the outer side of the metal-reinforced layer 34 on the outer side of the bead core 26 in the tire axial direction. In this example, the fiber-reinforced layer 32 is provided in two layers, that is, a first fiber-reinforced layer 32A on the inner side in the tire axial direction and a second fiber-reinforced layer 32B on the outer side.

The first fiber-reinforced layer 32A is provided on the outside of the bead core 26 in the tire axial direction so as to cover the upper end (that is, the outer end in the tire radial direction) 34E of the metal reinforcing layer 34 from the outside. The first fiber-reinforced layer 32A extends outward in the tire radial direction beyond the upper end 34E of the metal-reinforced layer 34 . In this example, the first fiber-reinforced layer 32A is arranged only on the outside of the bead core 26 in the tire axial direction, and is not rolled inward of the bead core 26 .

The second fiber-reinforced layer 32B is overlapped on the outer surface of the first fiber-reinforced layer 32A, and extends outward in the tire radial direction beyond the upper end 34E of the metal-reinforced layer 34 . In this example, the second fiber-reinforced layer 32B is rolled inward in the tire axial direction over the lower end of the first fiber-reinforced layer 32A, and is overlapped with the metal-reinforced layer 34 at the inner rolled-in portion.

A rubber pad 38 for covering the turn-up end 18E of the carcass 18 from the axially outer side is provided on the axially outer side of the bead filler 28 . The rubber pad 38 is a rubber member provided between the bead filler strip 28 and the fiber-reinforced layer 32 . The portion 18B is disposed between the fiber reinforced layer 32 , and further, as enlarged in FIG. 3 , is disposed between the rolled portion 18B and the metal reinforced layer 34 to form a terminal.

As shown in FIG. 2 , the cross-sectional shape of the interface 29 between the rubber pad 38 and the bead filler 28 is formed in a substantially linear shape without bending, zigzag, etc., that is, the rubber pad 38 moves along the bead filler 28 smoothly. configuration. In addition, the rubber pad 38 is formed such that a portion 38P on the outer side in the tire radial direction than the turned-up end 18E of the carcass 18 gradually becomes thinner toward the outer side in the radial direction. In this way, the ply 18 is formed so that the thickness gradually becomes thinner at a position closer to the outer side than the rolled-up end 18E, whereby the thickness of the rubber pad 38 near the rolled-up end 18E can be ensured while reducing the fiber reinforcement. The thickness of the upper end of the layer 32 or the upper end of the rubber pad 38 can suppress the generation of air holes.

On the outside of the bead core 26 in the tire axial direction, terminal positions of the above-mentioned members are set as follows. The upper end 34E of the metal reinforcement layer 34 is located further inward in the tire radial direction than the turned-up end 18E of the carcass 18 . The upper end of the fiber-reinforced layer 32 is located further outside in the tire radial direction than the rolled-up end 18E. Specifically, the upper end 32AE of the first fiber-reinforced layer 32A and the upper end 32BE of the second fiber-reinforced layer 32B are located on the outer side in the tire radial direction than the turn-up end 18E. In addition, the upper end 32AE of the first fiber-reinforced layer 32A is located on the outer side in the tire radial direction than the upper end 32BE of the second fiber-reinforced layer 32B. The upper end 38A of the rubber pad 38 is located closer to the outer side in the tire radial direction than the upper end of the fiber-reinforced layer 32 (specifically, the upper end 32AE of the first fiber-reinforced layer 32A). In addition, as mentioned above, since the lower end 38B of the rubber pad 38 is disposed between the rolled portion 18B and the metal reinforcement layer 34, the lower end 38B of the rubber pad 38 is located closer to the radial direction of the tire than the upper end 34E of the metal reinforcement layer 34. inside position.

Here, as shown in FIG. 2, the distance in the tire radial direction from the lower end 38B of the rubber pad 38 to the upper end 34E of the metal reinforcement layer 34 (that is, the interval in the tire radial direction Z) is H0, and the distance from the metal reinforcement layer 34 The tire radial distance from the upper end 34E to the rolled-up end 18E is H1. At this time, H0 and H1 are set to be substantially the same. Specifically, H1/H0 is set within the range of 0.80-1.0 (0.80≦H1/H0≦1.0).

In addition, assuming that the tire radial distance from the rolled-up end 18E to the upper end 32BE of the second fiber-reinforced layer 32B as the next step is H2, the distance from the upper end 32BE of the second fiber-reinforced layer 32B to the next step is The tire radial distance from the upper end 32AE of the first fiber reinforced layer 32A is H3, and the tire radial distance from the upper end 32AE of the first fiber reinforced layer 32A to the upper end 38A of the rubber pad 38 as the next step is H4. At this time, H2, H3, and H4 are set to be substantially the same. Specifically, set H2/H4 within the range of 0.60-0.90 (0.60≦H2/H4≦0.9), and set H3/H4 within the range of 0.80-1.0 (0.80≦H3/H4≦1.0) . More preferably, H2/H4 and H3/H4 are set within the range of 0.80-0.90.

Further, both H0 and H1 are set to be larger than any one of H2, H3 and H4. That is, H0>H2, H0>H3, H0>H4, H1>H2, H1>H3, and H1>H4. Preferably, 1.3≦H1/H2≦1.8.

In this way, the distances H0 and H1 between the member ends on both sides of the upper end 34E of the metal-reinforced layer 34 are set to be greater than the distances H2 and H3 between the member ends on both sides of the upper ends 32AE and 32BE of the fiber-reinforced layer 32 . , H4, and on this basis, setting the intervals H0 and H1 at the ends of each member to be approximately the same, and setting H2, H3, and H4 to be approximately the same, can suppress the increase in tire mass and suppress air holes generation, and at the same time, the durability of the bead portion 12 can be improved. Specifically, in order to suppress the occurrence of air holes while suppressing the increase in tire mass, it is very effective to set the intervals between the ends of the respective members equally. However, compared with the upper ends 32AE, 32BE of the fiber-reinforced layer 32 , the upper end 34E of the metal-reinforced layer 34 tends to concentrate strain more easily and is thicker, so it is likely to be a cause of air pockets. Therefore, by setting both of H0 and H1 to be greater than any one of H2, H3, and H4, it is possible to appropriately distribute the intervals between the ends of the members in the limited height dimension of the bead portion 12, thereby suppressing an increase in tire mass. While suppressing the occurrence of air pockets, the durability can be improved.

There is no particular limitation on the terminal positions of the metal-reinforced layer 34 and the second fiber-reinforced layer 32B on the inner side of the bead core 26 in the tire axial direction. In this embodiment, the terminal 32BF of the second fiber-reinforced layer 32B is located The terminal end 34F of the tire 34 is positioned closer to the outer side in the tire radial direction, and is provided so as to cover the terminal end 34F.

In the present embodiment, the bead filler 28 includes: a lower bead filler 40 having a circular cross section and surrounding the bead core 26 ; and an upper bead filler 42 disposed on the lower bead filler 40 . radially outer side of the tire, and the rubber hardness is lower than that of the rubber filler strip 40 on the lower side. The interface 44 between the lower bead filler 40 and the upper bead filler 42 is formed as a curved surface protruding outward in the tire radial direction. The upper bead filler 42 has a tapered shape toward the outer side in the tire radial direction, and the tip of the upper bead filler 42 is arranged on the outer side in the tire radial direction than the upper end 38A of the rubber pad 38 .

The rubber hardness ( K1 ) of the above rubber pad 38 is set to be lower than the rubber hardness ( K3 ) of the lower side bead filler 40 and equal to or greater than the rubber hardness ( K2 ) of the upper side bead filler 42 . That is, K2≦K1<K3 is set, more preferably K2<K1<K3. According to this, the movement of the bead core 26 can be suppressed while ensuring the adhesiveness with surrounding members. In addition, by providing the rubber pad 38 with high hardness, movement of the wound-up end 18E of the carcass 18 can be suppressed. But it is not particularly limited. Preferably, each hardness is based on Shore A (°) according to JIS K6253. The rubber hardness of the lower side filler strip 40 is 80-95 (more preferably 85-90). The rubber hardness of the strip 42 is 55-70 (more preferably 56-65), and the rubber hardness of the rubber pad 38 is 65-80 (more preferably 70-78). In addition, reference numeral 45 denotes a bead cover for the bead core 26 .

In addition, in this embodiment, as shown in FIGS. 2 and 3 , the lower end 38B of the rubber pad 38 is located closer to the axially outer end 44A of the interface 44 between the lower side filler strip 40 and the upper side filler strip 42 . The radially inner position of the tire. Thus, the rubber pad 38 is interposed between the carcass layer 18 and the metal reinforcement layer 34 on the outside of the highly rigid underfill rubber strip 40 . Therefore, it is possible to suppress the cords of the carcass 18 from being broken between the highly rigid underside bead filler 40 and the metal reinforcement layer 34 , thereby improving durability.

In addition, in the present embodiment, the gasket 46 is disposed on the outer side of the bead filler 28 in the tire axial direction. The gasket 46 clamps the rubber pad 38 together with the upper side filler strip 42 . From the viewpoint of reducing the strain applied to the turned-up end 18E of the carcass 18 , the spacer 46 is preferably made of a rubber material having a hardness equal to or greater than that of the upper side filler bead 42 .

(second embodiment)

Fig. 4 is a sectional view showing a bead portion 12A of a pneumatic radial tire of a second embodiment. In the second embodiment, the structure of the fiber-reinforced layer 32 is different from that of the first embodiment.

That is, in this example, not only the second fiber-reinforced layer 32B but also the first fiber-reinforced layer 32A is wound around the bead core 26 to the inside thereof. In addition, on the outer side in the tire axial direction of the bead core 26, the upper end 32BE of the second fiber-reinforced layer 32B is located closer to the outer side in the tire radial direction than the upper end 32AE of the first fiber-reinforced layer 32A, that is, the second fiber-reinforced layer 32B It is provided so as to cover the upper end 32AE of the first fiber-reinforced layer 32A from the outside. In addition, on the inner side of the bead core 26 in the tire axial direction, the terminal end 32AF of the first fiber-reinforced layer 32A is located on the outer side in the tire radial direction than the terminal end 32BF of the second fiber-reinforced layer 32B and the terminal end 34F of the metal-reinforced layer 34, And it is provided so that it may cover the terminal end 34F of the metal reinforcement layer 34 from inside.

In this way, when the fiber-reinforced layer 32 is composed of two layers 32A and 32B, any one of the upper ends 32AE and 32BE may be positioned radially outward in the tire axial direction outer side of the bead core 26 . , is not particularly limited. In addition, both layers may be rolled inwardly on the inner side of the bead core 26 in the tire axial direction, and the positional relationship between the terminal ends 32AF and 32BF on the inner side at this time may be located on the outer side in the tire radial direction. Regarding the second embodiment, the other structures and effects are the same as those of the first embodiment, and the description thereof will be omitted here.

(third embodiment)

Fig. 5 is a sectional view showing a bead portion 12B of a pneumatic radial tire of a third embodiment. The third embodiment differs from the first embodiment in that the fiber-reinforced layer 32 is constituted by one layer.

That is, in this example, a single fiber-reinforced layer 32C is provided, and the upper end 32CE of the fiber-reinforced layer 32C is located on the outer side in the tire radial direction than the turn-up end 18E of the carcass 18 on the outer side in the tire axial direction of the bead core 26 . , and is located closer to the inner side in the tire radial direction than the upper end 38A of the rubber pad 38 .

And, similar to the first embodiment, H1/H0 is set within the range of 0.80-1.0, on this basis, the tire radial distance from the rolled-up end 18E to the upper end 32CE of the fiber-reinforced layer 32C is H2, The distance in the tire radial direction from the upper end 32CE of the fiber-reinforced layer 32C to the upper end 38A of the rubber pad 38 as the next stepped portion is H4, and H2 and H4 are set to be substantially the same. Specifically, H2/H4 is set within the range of 0.60-0.90 (0.60≦H2/H4≦0.90), more preferably within the range of 0.80-0.90. In addition, both H0 and H1 are set to be greater than any one of H2 and H4, that is, H0>H2, H0>H4, H1>H2, and H1>H4. Preferably, 1.3≦H1/H2≦1.8.

In this way, when the fiber-reinforced layer 32 is constituted by one layer, as described above, by setting the interval between the ends of each member, it is possible to suppress the increase in tire mass and suppress the occurrence of air holes, thereby improving the bead portion. 12 durability. Regarding the third embodiment, other structures and effects are the same as those of the first embodiment, and the description thereof will be omitted here.

(other implementations)

The fiber-reinforced layer 32 may also be provided in three or more layers. In this case, the fiber-reinforced layer is selected from the turned-up end of the carcass layer to the upper end having the smallest radial distance on the outer side in the tire radial direction, and the distance between the upper end of the fiber-reinforced layer and the turned-up end is obtained. tire radial distance, and take it as H2. In addition, the distance in the tire radial direction between the upper ends of the plurality of fiber-reinforced layers is H3. Further, the fiber-reinforced layer is selected from the upper end of the rubber pad to the upper end with the smallest radial distance in the radial inner side of the tire, and the tire radial distance between the upper end of the fiber-reinforced layer and the upper end of the rubber pad is obtained. distance, and take it as H4. And, about these H2, H3, and H4, it is sufficient to set the intervals between the ends of the respective members in the same manner as in the first embodiment.

The pneumatic radial tire according to the present embodiment is suitable as a heavy-duty pneumatic tire for heavy-duty vehicles such as trucks, buses, industrial vehicles, and construction vehicles because of its excellent bead portion durability.

Some embodiments have been described above, but these embodiments are presented as examples and are not intended to limit the scope of the present invention. These novel embodiments can be implemented in other various embodiments, and various omissions, substitutions, and changes can be made without departing from the gist of the present invention.

【Example】

In order to specifically illustrate the structure and effect of the above-mentioned embodiment, a pneumatic radial tire for heavy load (size: 11R22.516PR, rim: 22.5×7.50) was trial-produced, and the performance evaluation was carried out. The evaluation method is as follows.

(1) Whether there are air holes

After the tire is vulcanized and molded, use a bubble detector to detect whether there are air pockets with a radius of more than 5 mm. Those without air pockets are indicated by "○", and those with air pockets are indicated by "X".

(2) Bead Durability

The tire mounted on the rim was filled with an internal pressure of 900kPa, pressed against a steel drum with a radius of 1.7m and a smooth surface with 210% of the JATMA standard load, and driven at a speed of 40km/h for 168 hours. The load was increased by 10% every 168 hours, and the vehicle was driven until the bead portion was damaged. The room temperature was set at 40°C. About the time until failure, comparative example 1 was set as 100, and it expressed as an index. The larger the numerical value, the better the durability.

(3) Tire quality

The mass of the tire was measured, and relative to Comparative Example 1, those with a mass increase of less than 3% were indicated by "○", and those with a mass increase of more than 3% were indicated by "×".

Table 1 shows the structures of the tires of Examples 1-5 and Comparative Examples 1-4. Examples 1-3 are examples of the structure of the bead portion shown in FIG. 2 having the above-mentioned first embodiment, and Example 4 is an example of the structure of the bead portion shown in FIG. 5 of the above-mentioned third embodiment. 5 is an example of the structure of the bead portion shown in FIG. 4 having the above-mentioned second embodiment. Comparative Example 1 is an example in which a fiber-reinforced layer is not provided as shown in FIG. 6 , and in FIG. 6 , members corresponding to members already described in the first embodiment are given the same reference numerals. Comparative Examples 2-4 are based on the bead portion structure shown in FIG. 2 as in Examples 1-3, but the setting of the interval between the ends of each member is different. In Embodiments 1-5, the lower end 38B of the rubber pad 38 is located closer to the inner side in the tire radial direction than the axially outer end 44A of the rubber filling strip interface 44 .

In Examples and Comparative Examples, as the metal cords constituting the metal reinforcing layer 34, steel cords having a twisted structure of 3+8×0.22HT, which are arranged at an inclination of 30° with respect to the tire circumferential direction, are used. . As the organic fiber cords constituting the fiber-reinforced layer 32 , 2991 dtex nylon fiber cords were used, and the nylon fiber cords were arranged at an inclination of 40° with respect to the tire circumferential direction.

【Table 1】

As shown in Table 1, Examples 1 to 5 of the present embodiment suppressed the increase in tire mass and prevented the generation of air holes, while improving the durability of the bead portion, relative to Comparative Example 1 as a comparative test. In particular, in Examples 1-3 and 5 in which two fiber-reinforced layers were properly arranged, the durability of the bead portion was remarkably improved. In contrast, in Comparative Example 2, although the fiber-reinforced layer was added, the distance between the rolled-up end of the carcass ply and the upper end of the metal-reinforced layer was small, and the distance between the fiber-reinforced layers was also small, so Air pockets are generated, and the durability of the bead portion is also poor. In Comparative Example 3, since the intervals between the ends of the members were too wide, the amount of increase in tire mass was large. In Comparative Example 4, since the interval H1 of the member ends near the upper end of the metal-reinforced layer is equal to or smaller than the interval H2 between the member ends between the fiber-reinforced layers, the durability of the bead portion is also inferior.

Claims (7)

1. A pneumatic radial tire, characterized in that, The pneumatic radial tire has: A bead core embedded in the bead portion; a bead filler disposed outside the bead core in the tire radial direction; at least one fiber-reinforced layer comprising organic fiber cords disposed axially outside of the turn-up portion of the ply; a metal reinforcement layer comprising a fiber-reinforced layer disposed on the turn-up portion and the fiber-reinforced layer metal cords in between; and a rubber pad covering the rolled-up end of the ply from the axially outer side of the tire and interposed between the bead filler strip and the fiber-reinforced layer, On the outer side in the tire axial direction of the bead core, the upper end of the metal reinforcement layer is located closer to the inner side of the tire radial direction than the turn-up end, and the upper end of the fiber-reinforced layer is located further inward than the turn-up end. The upper end of the rubber pad is located closer to the outer side of the tire radial direction than the upper end of the fiber reinforced layer, and the lower end of the rubber pad is between the rolled part and the metal reinforcement. set between layers, The tire radial distance from the lower end of the rubber pad to the upper end of the metal reinforcement layer is H0, the tire radial distance from the upper end of the metal reinforcement layer to the rolled-up end is H1, and the The tire radial distance from the rolled-up end to the upper end of the fiber-reinforced layer having the closest upper end in the tire radial direction is H2, and the distance from the upper end of the rubber pad to the fiber-reinforced layer having the closest upper end in the tire radial direction is taken as H2. The tire radial distance at the upper end is H4, H1/H0 is 0.80-1.0, H2/H4 is 0.60-0.90, and both H0 and H1 are larger than any one of H2 and H4. 2. The pneumatic radial tire according to claim 1, wherein: The pneumatic radial tire is provided with at least two fiber-reinforced layers, the tire radial distance between the upper ends of the at least two fiber-reinforced layers is H3, H1/H0 is 0.80-1.0, and H2/H4 is 0.60-0.90 , H3/H4 is 0.80-1.0, and both H0 and H1 are greater than any one of H2, H3 and H4. 3. The pneumatic radial tire according to claim 1, wherein: The rubber pad is formed such that a portion closer to the outer side in the tire radial direction than the rolled-up end gradually becomes thinner toward the outer side in the radial direction. 4. The pneumatic radial tire according to claim 1, wherein: The bead filler includes: a lower bead filler for surrounding the bead core; and an upper bead filler arranged outside the lower bead filler in the tire radial direction, and the rubber the hardness is lower than the rubber hardness of the underfill rubber strip, The rubber hardness of the rubber pad is lower than that of the lower rubber filling strip, and the rubber hardness of the rubber pad is equal to or higher than that of the upper filling rubber strip. 5. The pneumatic radial tire according to claim 4, wherein: The lower end of the rubber pad is located closer to the inner side in the tire radial direction than the axially outer end of the interface between the lower bead filler and the upper bead filler. 6. The pneumatic radial tire according to claim 4, wherein: A liner is disposed on the outer side of the bead filler strip in the tire axial direction, the rubber pad is sandwiched between the liner and the upper side filler strip, and the rubber hardness of the liner is the same as that of the upper side filler strip. The rubber hardness of the side filler strip is equal to or higher than that. 7. The pneumatic radial tire according to claim 1, wherein: H1/H2 is 1.3-1.8.