JP2000225816A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of a failure from a tip part of a carcass ply and to improve durability of a bead part. SOLUTION: By bending a carcass ply 16 from a bead core 12 to a ply tip P, that is, a folding part 16B having the ply tip P arranged in a tire radial outside part of a straight line K passing a tire radial outside tip 18A of a rim flange 18 within cross section along a tire rotary shaft and securing an actual length of the carcass ply 16, tensile force acting on a steel cord is gradually mitigated from the surrounding of the bead core 12 to the ply tip P of the carcass ply 16 through a mutual action between adjacent rubber and radial distortion of the ply tip P can be reduced. By locating the ply tip P at a radial inside, tire peripheral direction shearing distortion at the time of load traveling can be reduced. As a result, a failure (separation) from the ply tip P can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having improved bead durability.

[0002]

2. Description of the Related Art Conventionally, in a pneumatic radial tire, in order to prevent a failure from the end of a carcass ply, various measures have been taken regarding the position of the end, the structure of a bead core, a reinforcing method, the shape of a bead portion, and the like. Was.

[0003]

Generally, the radial strain due to the tension of the ply decreases as the position of the end of the ply moves outward in the tire radial direction. On the other hand, the tire circumferential shear strain during load running decreases. There was a trade-off problem of increasing.

The present invention has been made in view of the above circumstances, and has as its object to provide a pneumatic tire that can prevent a failure from an end of a carcass ply and can improve the durability of a bead portion.

[0005]

According to a first aspect of the present invention, there is provided a main body extending from one bead core to the other bead core, and provided from the inside of the tire to the outside around the bead core provided continuously with the main body. With a folded part,
A pneumatic tire provided with a carcass composed of at least one ply composed of a plurality of cords arranged in parallel with each other, wherein a tire rim flange has a tire radially outer side when viewed in a cross section along a tire rotation axis. A folded portion having a ply end disposed on the tire radial direction outside of a straight line K passing through the end has at least one bent portion, and the ply end is defined as P, and the intersection of the ply and the straight line K is defined as an intersection. When Q, the actual length of the ply between the ply end P and the intersection point Q is 1.3 times or more the length of a straight line connecting the ply end P and the intersection point Q. It is characterized by doing.

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

[0007] When the pneumatic tire is filled with air to increase the internal pressure, and when rolling under load, tension acts on the cord of the ply.

Among the bead portions, the outer portion of the bead core in the radial direction of the tire, particularly the outer portion of the rim flange in the tire radial direction beyond the straight line K passing through the outer end of the rim flange in the radial direction of the tire, is well movable at the time of internal pressure filling and rolling. Part.

In the pneumatic tire according to the first aspect, the ply from the bead core to the end of the ply, that is, the ply arranged in the tire radial direction outside the straight line K passing through the tire radial outside end of the rim flange. By bending the folded portion having an end in a cross section along the tire rotation axis and securing the actual length of the ply, the tension acting on the cord is applied to the adjacent member (rubber) from the periphery of the bead core to the end of the ply. Through the interaction between the ply and the ply, thereby reducing the ply end distortion in the radial direction. Further, by positioning the end of the ply radially inward, it is possible to reduce the tire circumferential shear strain during load running.

As a result, a failure (separation) from the end of the ply can be prevented.

The length of a straight line connecting the ply end P and an intersection Q of the ply and a straight line K passing through the tire radially outer end of the rim flange is defined by the length of the ply between the ply end P and the intersection Q. If the actual length is less than 1.3 times, the radial distortion of the end of the ply cannot be sufficiently reduced.

[0012] When the end of the ply is positioned radially inward without bending the ply from the bead core to the end of the ply in the cross section along the tire rotation axis, the ply from the bead core to the end of the ply is formed. The actual length cannot be ensured, and the ply may be pulled out when tension is applied.

It is particularly effective to apply the present invention to a flat tire having a flat rate of 70% or less.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, a perpendicular line perpendicular to the ply on the inner surface side of the tire passing through the height position of the rim flange contact point is defined as L. The ply end P is located on the perpendicular L or inside the perpendicular L in the tire radial direction.

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

The height position of the rim flange contact point (here,
A point on the outer surface of the bead portion that is separated from the straight line K by 5 mm outward in the tire radial direction. ) Through the inner ply of the tire (ie,
The outer portion in the tire radial direction relative to the perpendicular L perpendicular to the main body portion) is a portion where the circumferential shear strain increases.

In the pneumatic tire according to the second aspect, the ply end P passes through the rim flange contact point height position and is on a perpendicular L perpendicular to the ply on the inner surface side of the tire or radially inward of the perpendicular L from the perpendicular L. Because it is located, the ply end P
The circumferential shear strain acting on the surface can be suppressed.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, reinforcing rubber is provided on both sides in the axial direction of the folded portion, and the axial direction of the folded portion is provided. The hardness of the inner reinforcing rubber is 80 to 90 degrees, and the hardness of the reinforcing rubber on the outer side in the axial direction of the folded portion is 65 to 90 degrees.
It is characterized by 75 degrees.

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

A reinforcing rubber having a hardness of 80 to 90 degrees is provided on the inside of the folded portion in the axial direction, and a hardness of 65 to 75 is provided on the outside of the folded portion in the axial direction.
By providing the reinforcing rubber with a certain degree, the tension acting on the ply can be reduced.

The hardness of the reinforcing rubber on the inner side in the axial direction is 80.
If it is less than the degree, the rigidity of the bead part is low, the bead part is overly collapsed under load, or it is not preferable because it moves too much in the circumferential direction. Extrusion work becomes difficult.

If the hardness of the reinforcing rubber on the outer side in the axial direction is less than 65 degrees, the effect of relaxing strain is insufficient. Reinforced rubber hardness is 75
Exceeding the degree causes the rubber to become brittle. For example, the rubber is liable to be cracked by being subjected to a large repetitive strain in the axial direction due to the reaction force from the rim flange (strain during load rolling).

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
The cord of the bent portion is plastically deformed before vulcanization.

Next, the operation of the pneumatic tire according to claim 4 will be described.

If the cord at the bent portion is elastically deformed, a force for returning the cord to its original shape (straight line) is always applied. This force acts on the ply end, which is not preferable.

On the other hand, when the cord at the bent portion is plastically deformed as in the present invention, the force for returning the cord to the original shape (straight line) does not act on the cord, so that an extra force is applied to the end of the ply. It is preferable because no force acts.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects,
The cord is a steel cord.

Next, the operation of the pneumatic tire according to claim 5 will be described.

When comparing a carcass ply using a steel cord with a carcass ply using an organic fiber cord, the carcass ply using a steel cord has more failures from the ply end. In the present invention, since the distortion of the end of the ply can be sufficiently reduced, even when a steel cord is used for the carcass ply, it is possible to sufficiently prevent the failure from the end of the ply, and This is particularly effective for a pneumatic tire using a steel cord for the cord.

[0030]

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

In the present embodiment, the carcass 14 is composed of one carcass ply 16, but the carcass ply 16 may be two or more.

The carcass ply 16 includes a plurality of steel cords (not shown) extending in a radial direction arranged in parallel with each other, and the plurality of steel cords are formed on a thin coating rubber (not shown). It is of a normal structure buried.

The carcass ply 16 has one bead portion 1
A body portion 16A extending from one bead core 12 to the bead core 12 of the other bead portion 11, and a folded portion 16 having a terminal side folded around the bead core 12 from the tire inner side to the outer side;
B.

The folded portion 16B is formed by a straight line K whose ply end P passes through the radially outer end 18A of the rim flange 18 in the tire radial direction.
(Parallel to the tire rotation axis), and is disposed at least one or more bent portions, in this embodiment, the first bent portion 16 from the bead core 12 side.
Ba, the second bent portion Bb and the third bent portion 16Bc
It has two bends.

The first bent portion 16Ba, the second bent portion Bb, and the third bent portion 16Bc are formed by plastically deforming the carcass ply 16 (steel cord) during tire manufacturing.

The actual length of the carcass ply 16 between the ply end P and the point of intersection Q is 1. The length of the straight line connecting the ply end P and the point of intersection Q between the carcass ply 16 and the line K is 1.
It is set to three times or more.

Further, the rim flange contact point height position 20
, The ply end P is located on the perpendicular L or radially inward of the perpendicular L with respect to the main body 16A of the carcass ply 16.

The bead portion 11 includes a bead core 12.
A stiffener 22 for securing the rigidity of the bead portion 11 is provided on the outer side in the tire radial direction.

The bead core 1 of the carcass ply 16
On the side opposite to 2, a chafer 24 made of an organic fiber cord such as steel cord or nylon is arranged. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

In the pneumatic tire 10 of this embodiment, the carcass ply 1 from the bead core 12 to the ply end P
6, the tire radially outer end 18 of the rim flange 18
A folded portion 16B having a ply end P disposed radially outside of the straight line K passing through A is bent in a cross section along a tire rotation axis (not shown), and the carcass ply 1 is bent.
6, the tension acting on the steel cord is applied to the carcass ply 1 from around the bead core 12.
The ply end 6 is gradually relaxed through the interaction between the member (rubber) adjacent to the ply end P, and the radial distortion of the ply end P can be reduced. In addition, by positioning the ply end P on the inner side in the radial direction, it is possible to reduce the tire circumferential shear strain during load running.

Thus, a failure (separation) from the ply end P can be prevented.

If the actual length of the carcass ply 16 between the ply end P and the intersection point Q is less than 1.3 times the length of the straight line connecting the ply end P and the intersection point Q, the carcass ply 16 The radial distortion of the ply end P cannot be sufficiently reduced.

Further, the carcass ply 16 from the bead core 12 to the ply end P of the carcass ply 16 is not bent in a cross section along the tire rotation axis.
When the ply end P of the carcass ply 16 is positioned radially inward, the actual length of the carcass ply 16 from the bead core 12 to the ply end P of the carcass ply 16 cannot be secured, and when the tension is applied, the carcass ply 16 There is a risk of being pulled out.

Further, since the ply end P is located on a perpendicular line L passing through the rim flange contact point height position 20 and perpendicular to the carcass ply 16 or on the radially inner side of the perpendicular line L, the ply end P The acting circumferential shear strain can be suppressed.

In the pneumatic tire 10 of the present embodiment, the folded portion 16B has three bent portions of the first bent portion 16Ba, the second bent portion Bb, and the third bent portion 16Bc. However, the present invention is not limited to this, and it is sufficient that the present invention has at least one or more bent portions. As shown in FIG.
May have only the first bent portion 16Ba and the second bent portion 16Bb as shown in FIG.
May be provided, and although not shown, 4
It may have more than one bend.

Further, as shown in FIG. 4, a first stiffener 26 is arranged inside the first bent portion 16Ba in the axial direction, and a second stiffener 28 is arranged outside the first bent portion 16Ba in the axial direction. In addition, the third stiffener 30 may be arranged radially outside the first bent portion 16Ba.

In this case, the hardness of each stiffener is
Hardness of third stiffener 30 <second stiffener 2
It is preferable to set the hardness of the second stiffener 28 to the hardness of the second stiffener 28 <the hardness of the first stiffener 26.

Further, the hardness of the first stiffener 26 is 80 to 90 degrees, and the hardness of the second stiffener 28 is 65 to 90 degrees.
Preferably, it is set at 75 degrees.

In this way, the tension acting on the carcass ply 16 can be effectively reduced.

The hardness of the first stiffener 26 is 8
If the angle is less than 0 degree, the rigidity of the bead portion 11 becomes low, and the bead portion 11 is excessively tilted under load or moves in the circumferential direction. Rubber kneading and extrusion operations during the production of the rubber.

The second tiffener 28 has a hardness of 6
If it is less than 5 degrees, the effect of relaxing the strain is insufficient, and if it exceeds 75 degrees, the rubber becomes brittle. For example, it receives a large repetitive strain in the axial direction due to the reaction force from the rim flange 18 (strain during load rolling). As a result, cracks tend to occur.

It is particularly effective to apply the present invention to a flat tire having a flat rate of 70% or less. (Test Example) Next, in order to confirm the effect of the present invention, a conventional tire having a tire size of 275 / 70R225 and a tire of the embodiment to which the present invention was applied were prepared, and the tire was tested with a drum tester. Was subjected to an endurance test.

The tire of the embodiment has the structure shown in FIG. 4 (the hardness of the first stiffener 26 is 85 degrees, the hardness of the second stiffener 28 is 70 degrees, the hardness of the third stiffener 30 is 60 degrees, and the ply ends are ply ends). The actual length of the carcass ply 16 between the ply end P and the intersection Q is 1.8 to 2.2 times the length of the straight line connecting the P and the intersection Q.) As shown in FIG. 5, a tire (the stiffener 21 has a hardness of 85 ° and the stiffener 22 has a fold end 16B of the carcass ply 16 that is substantially linear and the ply end P is located outside the perpendicular L in the tire radial direction). Hardness 60 degrees.)
It is.

In the drum test, the normal internal pressure (JATMA Y
Air pressure corresponding to the maximum load capacity in the applicable size and ply rating in EAR BOOK. ), Standard rim (described in JATMA YEAR BOOK), speed 6
At 0km / h, the maximum load (JATMA YEAR BOOK
Maximum load capacity in the application size ply rating in the. ) Of 150% load.

The evaluation was performed by measuring the time until the ply end separation occurred in the bead portion of the test tire. In addition, the result was represented by an index with the time until the ply end separation occurred in the conventional tire as 100.

As a result of the test, the time required for the ply end separation to occur in the tire of the example to which the present invention was applied was 140 with respect to 100 of the conventional tire, and the durability of the bead portion was greatly increased. It turned out to be better.

[0057]

As described above, since the pneumatic tire of the present invention has the above-described configuration, it is possible to prevent a failure from the end of the carcass ply and to improve the durability of the bead portion. Has excellent effects.

[Brief description of the drawings]

FIG. 1 is a sectional view of a bead portion of a pneumatic tire according to one embodiment of the present invention.

FIG. 2 is a sectional view of a bead portion of a pneumatic tire according to another embodiment of the present invention.

FIG. 3 is a sectional view of a bead portion of a pneumatic tire according to still 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 cross-sectional view of a bead portion of a conventional pneumatic tire used for a test.

[Explanation of symbols]

 Reference Signs List 10 pneumatic tire 11 bead portion 12 bead core 14 carcass 16 carcass ply 16A main body portion 16B folded portion 16Ba first bent portion 16Bb second bent portion 16Bc third bent portion P ply end 26 first stiffener (reinforcing rubber) 28 Second stiffener (reinforced rubber)

Claims (5)

[Claims] 1. A main body extending from one bead core to the other bead core, and a folded portion provided continuously from the bead core and folded around the bead core from inside to outside of the tire, and are arranged in parallel with each other. A pneumatic tire provided with a carcass comprising at least one ply composed of a plurality of cords, the straight line passing through a tire radially outer end of a rim flange when viewed in a cross section along a tire rotation axis. A folded portion having a ply end disposed radially outside the tire from K has at least one or more bent portions, where P is the ply end, and Q is the intersection of the ply and the straight line K. The actual length of the ply between the ply end P and the intersection point Q is 1.3 times or more the length of a straight line connecting the ply end P and the intersection point Q. And air in Tire. 2. When a perpendicular line passing through the rim flange contact point height position and perpendicular to the ply on the tire inner surface is defined as L, the ply end P is on the perpendicular line L or has a tire diameter larger than the perpendicular line L. The pneumatic tire according to claim 1, wherein the pneumatic tire is located on an inner side in the direction. 3. A reinforcing rubber is provided on both sides of the folded portion in the axial direction. The hardness of the reinforcing rubber on the inner side in the axial direction of the folded portion is 80 to 90 degrees, and the hardness of the rubber on the outer side in the axial direction of the folded portion is increased. The pneumatic tire according to claim 1 or 2, wherein the reinforcing rubber has a hardness of 65 to 75 degrees. 4. The pneumatic tire according to claim 1, wherein the cord at the bent portion is plastically deformed before vulcanization. 5. The pneumatic tire according to claim 1, wherein the cord is a steel cord.