JP2000085319A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong a life for a bead part of a pneumatic tire. SOLUTION: An end part 28 of a folded part 16B is covered with a chafer 22, and an inside end part 22B is separated by 10 mm or more from the end part 28. When a crack 40 is generated in the end part 28, the crack 40 progresses toward a bead core 12 side between the folded part 16B and the chafer 22, then passes through the end part 22B, progresses to a stiffner 20 side to be turned, progresses toward an outside in a tire radial direction along the chafer 22 between the chafer 22 and the stiffner 20, and crosses finally a bead part 18 in an inside-outside direction of a tire in the vicinity of the end part 28 of the part 16B to bring the bead part 18 into failure. Since the crack 40 generated in the end part 28 has a long progress route until it crosses the bead part 18 in the inside-outside direction of the tire, the bead part 18 requires a long time for the failure, that is, a life of the bead part 18 is extended compared with conventional one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having improved durability of a bead portion and suitable for a heavy-duty vehicle.

[0002]

2. Description of the Related Art Heavy vehicles such as trucks, buses, etc.
Pneumatic tires for heavy loads are used.

[0003] In a conventional heavy duty pneumatic tire, as shown in FIGS. 6 to 8, an end portion of a carcass ply 100 is provided in order to suppress a distortion generated near the end portion of the carcass ply caused by pneumatic filling or load application. 102 to 10 to 15
mm lower (inside of tire radial direction: arrow IN direction side)
, A wire chafer (reinforcement layer) 104 is arranged, or as shown in FIG. 9, above the end 102 of the carcass ply 100 (tire outside in the tire radial direction: arrow OU)
The wire chafer 104 is arranged from the position (T direction).

[0004]

However, the end portion 1 of the carcass ply 100 may be pneumatically charged or loaded.
As a result, the strain generated near the end portion 102 of the carcass ply 100 propagates to the inside and outside of the tire due to the strain. For example, as shown in FIG. There is a problem that a crack 108 crosses in the inward and outward directions of the tire, leading to failure of the bead portion 106.

[0005] As shown in FIG.
In the tire in which the wire chafer 104 is disposed from a position above the end 102 of the tire 00, a crack generated near the upper end of the wire chafer 104 propagates to the inside and outside of the tire, and the bead 106 is There is a problem that a crack 108 crosses inward and outward, leading to failure of the bead portion 106.

The present invention has been made in consideration of the above-described circumstances, and has as its object to provide a pneumatic tire capable of delaying generation of a crack crossing a bead portion and extending the life of the bead portion.

[0007]

According to a first aspect of the present invention, there is provided at least one sheet having a main body extending from one bead core to the other bead core, and a folded portion formed by folding a terminal around a pair of bead cores. A pneumatic tire provided with a carcass composed of plies, wherein the vicinity of an end of the folded portion is covered with a reinforcing layer, and the reinforcing layer disposed along the tire axial direction outer surface of the folded portion. The end portion is located on the tire radial direction inner side than the rim contact position where the bead portion starts to contact the rim flange, and the end portion of the reinforcing layer disposed along the tire axial direction inner side surface of the folded portion is It is characterized in that it is located radially inward of the end of the folded portion in the tire radial direction.

Next, the operation of the pneumatic tire according to the first aspect will be described.

Strain is generated near the end of the carcass ply due to pneumatic filling or load, and a crack may be generated near the end of the folded portion of the carcass due to the strain. In conventional pneumatic tires, cracks generated near the end of the carcass ply propagate from there to the inside and outside of the tire,
Although the bead portion failed by crossing the bead portion in and out of the tire, in the pneumatic tire of the present invention, a crack generated near the end of the folded portion firstly formed the folded portion and the tire axis of the folded portion. To the bead core side between the reinforcing layer arranged along the inner side surface in the direction, and then to the inner side in the tire axial direction after crossing the end of the reinforcing layer, and then in the tire axial direction of the reinforcing layer The tire extends radially outward along the side surface, and further from the vicinity of the end of the turn-up portion to the tire inside and outside the tire, eventually traversing the bead portion in and out of the tire and causing failure of the bead portion And reach.

That is, in the pneumatic tire of the present invention, the vicinity of the end of the folded portion is covered with the reinforcing layer, and the end of the reinforcing layer disposed along the inner side surface in the tire axial direction of the folded portion is connected to the end of the folded portion. Since it is arranged radially inward of the tire, the crack propagation path until a crack crossing in and out of the tire is generated can be longer than that of a conventional pneumatic tire. Therefore, in the pneumatic tire of the present invention, the time from the occurrence of a crack to the failure of the bead portion can be extended, and the life can be extended.

It is to be noted that the end of the reinforcing layer disposed along the tire axially outer surface of the folded portion is not located radially inward of the rim contact position where the bead portion starts to contact the rim flange. In addition, since the reinforcing layer is not fixed, the movement of the reinforcing layer itself increases, and a crack may be generated from an end of the reinforcing layer, leading to separation.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, an end of the reinforcing layer disposed along an inner side surface in the tire axial direction of the folded portion has an end. It is characterized by being at least 10 mm away from the end.

Next, the operation of the pneumatic tire according to claim 2 will be described.

[0014] In the pneumatic tire according to the second aspect, the end of the reinforcing layer disposed along the inner side surface in the tire axial direction of the folded portion is separated from the end of the folded portion by 10 mm or more, so that the crack progresses. The path can be made sufficiently long, and the life of the bead portion can be reliably extended.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, an end protection layer is provided between an end of the folded portion and the reinforcing layer. It is characterized by:

Next, the operation of the pneumatic tire according to claim 3 will be described.

In the pneumatic tire according to the third aspect, the end protection layer is provided between the end of the folded portion and the reinforcing layer.
The strain generated between the end of the folded portion and the reinforcing layer can be reduced, and the generation of the crack itself can be delayed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a pneumatic tire 10 has a pair of bead cores 12 (only one side is shown in FIG. 1) and a carcass 14 straddling the pair of bead cores 12 in a toroidal shape. are doing.

The carcass 14 is composed of one carcass ply 16 in this embodiment.

The carcass ply 16 has a plurality of cords (not shown) arranged in parallel to each other, and has a normal structure in which the plurality of cords are embedded in a thin coating rubber (not shown). Things.

The carcass ply 16 is folded around the bead core 12 arranged in the bead portion 18 from the inside to the outside in the tire axial direction.

In order to secure the rigidity of the bead portion 18, a rubber having high hardness (a side rubber layer 36 to be described later) is provided between the main body portion 16A and the folded portion 16B of the carcass ply 16.
And has a higher hardness than the inner liner 38. )
Is provided.

In the present embodiment, the end portion 28 of the folded portion 16B is provided.
The vicinity of the (end of the cord) is covered with a chafer 22 in which a plurality of cords (steel wires in the present embodiment) are arranged in parallel with each other and rubber-coated.
The structure of the chafer 22 itself is the same as that of the conventional pneumatic tire, but the arrangement method is different.

The end 22A of the chafer 22 arranged along the outer surface in the tire axial direction of the folded portion 16B is
The radially inner side of the rim contact position A where the bead portion 18 starts to contact the rim flange 26 of the rim 24 (arrow IN
Direction side).

On the other hand, the end portion 22B of the chafer 22 arranged along the inner surface of the turn-back portion 16B in the tire axial direction is
It is located radially inward of the end portion 28 of the folded portion 16B in the tire radial direction.

The chafer 22 of the present embodiment is in close contact with the folded portion 16B.

A belt 32 made up of at least two belt plies 30, in this embodiment four belt plies 30, is arranged outside the carcass ply 16 in the tire radial direction.

A tread rubber layer 34 is provided outside the belt 32 in the tire radial direction, a side rubber layer 36 is provided outside the carcass 14 in the tire radial direction, and an inner liner 38 is provided on the inner surface of the carcass 14.

Here, the distance L along the folded portion 16B between the end portion 22B of the chafer 22 and the end portion 28 of the folded portion 16B arranged along the inner surface in the tire axial direction of the folded portion 16B is 10 mm or more. Preferably, in this embodiment, the end 22B of the chafer 22 is arranged near the bead core 12, and the distance L is ensured to be 10 mm or more. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

The pneumatic tire 10 is filled with air pressure,
When the vehicle travels under a load, the bead portion 18 is repeatedly deformed in the direction indicated by the arrow B in FIG. 1, thereby causing distortion near the end portion 28 of the folded portion 16B.

Due to this distortion, the end 28 of the folded portion 16B is formed.
2A to 2E, when a crack is generated from the (cord end of the carcass ply 16), the crack 40 is formed between the folded portion 16B and the chain disposed inside the folded portion 16B in the tire axial direction. The chafer extends between the fur 22 and the bead core 12, and then extends beyond the end 22 B of the chafer 22 to the stiffener 20 and turns back, and is arranged inside the turn-back portion 16 </ b> B in the tire axial direction. 2
Between the stiffener 2 and the stiffener 20 along the chafer 22 toward the radially outer side of the tire, and finally splits in the tire inward / outward direction near the end 28 of the turn-back portion 16B to move the bead portion 18 inward / outward of the tire. Bead section 18
Failure.

That is, in the pneumatic tire 10 of the present embodiment, since the crack 40 generated from the end portion 28 of the folded portion 16B has a long propagation path until the crack 40 crosses the bead portion 18 in and out of the tire, the crack 40 is formed. It takes time until the bead portion 18 breaks down by traversing the bead portion 18 in and out of the tire, that is, the life of the bead portion 18 can be extended as compared with the related art.

If the distance L between the end 22B of the chafer 22 and the end 28 of the folded portion 16B is less than A10 mm, the propagation path of the crack 40 cannot be made sufficiently long, and the life of the bead 18 will not be long. The effect of extending is small.

The position of the end portion 22A of the chafer 22 disposed outside the folded portion 16B is the rim contact position A
If the chafer 22 is located on the outer side in the tire radial direction, the chafer 22 is not fixed, so that the chafer 22 itself moves more, and a crack may be generated from an end of the chafer 22 to cause separation.

The chafer 22 of this embodiment is
Although a plurality of steel cords are arranged in parallel with each other and subjected to rubber coating, the present invention is not limited to this, and an organic fiber cord may be used instead of the steel cord, and a structure in which a plurality of cords intersect is used. It may be a woven fabric, and any material and structure may be used as long as it has a strength that does not allow the crack 40 generated from at least the end portion 28 of the folded portion 16B to penetrate.

In the present embodiment, the chafer 22 is in contact with the outer surface of the folded portion 16B. However, the present invention is not limited to this. For example, as shown in FIGS.
A rubber layer 42 as an end protection layer may be provided so as to surround the end 28, and the chafer 22 may be arranged outside the rubber layer 42.

The rubber layer 42 allows the chafer 22
And the interlayer shear strain generated between the end portions 28 of the folded portions 16B can be reduced, and the generation of cracks can be delayed. The rubber layer 42 is preferably made of rubber having the same performance as that of a normal cushion between belts, and is preferably made of rubber having a 200% modulus of 8 to 15 PA.

As shown in FIG. 5, the chafer 2 is arranged along the outer surface of the folded portion 16B in the tire axial direction.
2 may extend along the inner surface of the main body 16A beyond the bead core 12, and the chafer 22 disposed along the inner surface in the tire axial direction of the turn-back portion 16B may be a bead core 1
2 may extend to near the lower end.

The cord of the chafer 22 of the pneumatic tire shown in FIG.
The cord of the chafer 22 of the pneumatic tire shown in FIG. 4 is inclined by 30 ° with respect to the radial direction, and the cord of the chafer 22 of the pneumatic tire shown in FIG. 5 is inclined with respect to the radial direction. It is inclined at 60 °. In addition, the inclination angle of the cord of the chafer 22 is not limited to the one in the present embodiment. (Test Example) Next, in order to confirm the effect of the present invention, a tire of a conventional example and a tire of an example to which the present invention was applied were prepared, and a durability test of a bead portion was performed by a drum tester.

In the drum test, a test tire filled with an internal pressure of 900 KPA was attached to a drum tester and the weight was 5000 kg.
And a running test was performed at a drum speed of 60 km / h.

The evaluation was made by measuring the distance at which the bead portion of the test tire failed to run due to a failure, and expressed as an index with the running distance of the conventional tire being 100. The larger the index, the longer the running distance and the higher the durability.

Example tire: A tire having the structure shown in FIG.

Conventional tire: A conventional tire shown in FIG.

The size of each test tire was 275 / 70R22.5, and the cord (steel wire) of the chafer was 60 mm in the radial direction.
° is inclined.

[0045]

[Table 1] As shown in Table 1 above, it can be seen that the tire of the example to which the present invention is applied has a longer running distance until failure of the bead portion than the conventional tire, and has excellent bead portion durability. .

[0046]

As described above, the pneumatic tire according to the first aspect has the above-described structure, and thus has an excellent effect that the life of the bead portion can be extended.

Since the pneumatic tire according to the second aspect has the above-described structure, it has an excellent effect that the growth of the crack can be reliably delayed and the life of the bead portion can be reliably extended. .

Since the pneumatic tire according to the third aspect has the above-described structure, the generation of the crack itself can be delayed, and the life of the bead portion can be extended.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view along a tire rotation axis of a pneumatic tire according to one embodiment of the present invention.

FIGS. 2A to 2E are cross-sectional views of a bead portion for explaining a progress state of a crack.

FIG. 3 is a sectional view of a bead portion of a pneumatic tire according to another embodiment of the present invention.

FIG. 4 is a sectional view of a bead portion of a pneumatic tire according to still another embodiment of the present invention.

FIG. 5 is a sectional view of a bead portion of a pneumatic tire according to still another embodiment of the present invention.

FIG. 6 is a sectional view of a bead portion of a pneumatic tire according to a conventional example.

FIG. 7 is a sectional view of a bead portion of a pneumatic tire according to another conventional example.

FIG. 8 is a sectional view of a bead portion of a pneumatic tire according to still another conventional example.

FIG. 9 is a sectional view of a bead portion of a pneumatic tire according to still another conventional example.

[Description of Signs] 10 Pneumatic tire 12 Bead core 14 Carcass 16 Carcass ply (ply) 16A Main body 16B Folding part A Rim contact position 22 Chafer (reinforcing layer) 22A End (end of reinforcing layer) 22B End ( End of reinforcement layer) 28 End (end of folded portion) 42 End protection layer

Claims (3)

[Claims] 1. A pneumatic tire provided with a carcass comprising at least one ply having a main body extending from one bead core to the other bead core and a folded portion obtained by folding a terminal around a pair of bead cores. The vicinity of the end of the folded portion is covered with a reinforcing layer, and the end of the reinforcing layer arranged along the outer surface in the tire axial direction of the folded portion is such that the bead portion starts to contact the rim flange. The rim contact position is located inward in the tire radial direction, the end of the reinforcing layer disposed along the tire axial direction inner side surface of the folded portion is located below the end of the folded portion. A pneumatic tire characterized in that: 2. The end of the reinforcing layer arranged along the inner side surface in the tire axial direction of the folded portion is at least 10 mm away from the end of the folded portion. Pneumatic tires. 3. An end protection layer is provided between an end of the folded portion and the reinforcing layer.
Or the pneumatic tire according to claim 2.