JP2001010312A - Tubeless tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress toe chipping without damaging bead durability by arrang ing a chafer, an inner liner, installation rubber and a carcass in order from a tire inner bore surface to a bead core at a tire shaft direction outside and making the chafer have a specified complex modulus of elasticity, hardness and elongation at the time of breaking. SOLUTION: A tubeless tire 1 is provided with a carcass 6 which is folded back at a bead core 5 of a bead part 4 from a tread part 2 via a side wall part 3 and is locked, an inner liner 7 arranged by being faced to a tire inner bore surface, a chafer 9 made of hard rubber and installation rubber 10 interposed between the carcass 6 and the inner liner 7. In the bead structure, a complex modulus of elasticity E, a durometer A hardness H and elongation at the time of breaking of the chafer 9 are regulated to 11 to 13 Mpa, 77 to 83 degree 5 and a range of 300 to 380%, respectively, to prevent remarkable toe chipping of the chafer 9. As a result, toe chipping can be regulated without damaging bead durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is particularly suitable for heavy duty tires such as trucks and buses. By specifying the rubber physical properties of chafers, the rim is assembled and removed while maintaining bead durability. The present invention relates to a tubeless tire capable of suppressing rubber chipping (toe chipping) in a toe portion of a bead portion at the time.

[0002]

2. Description of the Related Art A tubeless tire, particularly a heavy duty tire such as a truck or a bus, is used under a high internal pressure and a high load. Therefore, a bead portion comes into contact with a rim at an extremely high fitting pressure. For this purpose, as shown in FIG. 5A, a chafer b made of hard rubber is provided in a contact area between the toe portion at and the rim from the heel portion ah to the bead outer surface ao, as shown in FIG. I have.

In the toe portion at, the chafer b generally covers the inner end c1 of the air-impermeable inner liner rubber c and rises radially outward to form a standing piece b1.
(Referred to as a covering structure for convenience) is widely used. This is due to the high adhesiveness of the inner liner rubber c to the molding former.
When a structure in which the inner end c1 of the inner liner rubber c is exposed on the inner surface of the tire (referred to as an exposed structure for convenience) as shown in (B), the inner liner rubber is removed when the green tire is removed from the molding former. This is because the inner end c1 of c tends to be easily peeled off from the chafer b, and in order to prevent this, it takes time to remove the green tire and the production efficiency is impaired. From such a viewpoint, the coating structure is widely used.

[0004]

However, in the tire, when the rim is assembled / removed, the toe portion at is hooked on the rim flange rf and deforms as shown in FIGS. 6A and 6B. In the case of the covering structure, the maximum elongation acts on the hard upright portion b1 on the tire inner hole surface side. As a result, the upright portion near the height position of the radially inner end of the bead core e is obtained. The toe chipping k such as crack damage easily occurs in the portion b1.

[0005] In particular, in the case of heavy duty tires, tire retreading is performed in which the tread portion of old tires whose wear life has passed is replaced and recycled, but in such old tires, rubber heat and compression force during use are increased. Thereby, since the chafer b becomes harder than a new tire, the toe chipping k becomes more conspicuous, and therefore, not only the life of the new tire,
There is a problem that the life of the retreaded tire and the recyclability are greatly impaired.

Accordingly, the present invention provides a tire having the above-mentioned coated structure, which is characterized by specifying the complex elastic modulus E *, durometer A hardness, and elongation at break of the chafer without deteriorating bead durability. It aims to provide a tubeless tire that can effectively suppress toe chipping.

[0007]

In order to achieve the above object, the invention according to claim 1 of the present application is directed to a carcass that is folded and locked by a bead core of a bead portion from a tread portion to a sidewall portion, and a tire. An inner liner made of air-impermeable rubber facing the lumen surface, a chafer made of hard rubber, and a tubeless tire including an insulation rubber interposed between the carcass and the inner liner in a bead portion, With respect to a reference line X passing through a radially inner end of the bead core in the tire axial direction, a radially inner end of the inner liner and the insulation rubber is located radially inward of the reference line X, In addition, the radially outer end of the chafer is located radially outward from the reference line X, and the chafer is located on the tire lumen surface on the reference line X. Axially outwardly to the bead core, a chafer, the inner liner, while positioned insulation rubber, and the order of the carcass, the chafer 70 ° C, complex elastic modulus at 2% strain E * is 11 to 13
Mpa, durometer A hardness is 77 to 83 degrees, and elongation at break is 300 to 380%.

According to a second aspect of the present invention, a cord filler folded back by the bead core is interposed between the insulation rubber and the carcass.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 illustrates a meridional section when the tubeless tire of the present invention is formed as a heavy-duty tire, for example, for trucks and buses.

In FIG. 1, a tubeless tire 1 (hereinafter referred to as a tire 1) has a carcass 6 which is folded from a tread portion 2 to a side wall portion 3 and is locked by a bead core 5 of a bead portion 4; An inner liner 7 and a chafer 9 made of hard rubber,
An insulation rubber 10 is provided between the carcass 6 and the inner liner 7.

The carcass 6 has at least one folded portion 6b provided at both ends of a main body portion 6a extending between the bead cores 5 and 5 from the inside to the outside in the tire axial direction around the bead core 5, in this embodiment. The example formed from one carcass ply 6A is illustrated. This carcass ply 6A
Applies the carcass cord 70-90 to the tire equator C.
A so-called radial structure arranged at an angle of °, nylon, rayon, polyester, as carcass cord
Organic fiber cords such as aromatic polyamide or steel cords are preferably used.

A belt layer 11 is disposed outside the main body 6a of the carcass 6 and inside the tread portion 2. In this example, the belt layer 11 is formed by applying a belt cord using a steel cord to the tire equator C by, for example, 60 mm.
Innermost belt ply 11 arranged at an angle of about ± 10 °
A and a four-layer structure of belt plies 11B, 11C, and 11D arranged at a small angle of 30 ° or less with respect to the tire equator C. For example, one or more places where belt cords cross each other between the plies are provided. They are stacked. As the belt cord, an organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide can be used as necessary.

A space between the main body portion 6a and the folded portion 6b of the carcass 6 is filled with a bead apex rubber 12 that extends from the bead core 5 outward in the radial direction. The bead core 5 has a ring shape formed by winding a bead wire made of steel, for example. In the present example, a flat hexagonal one having a horizontally long cross section is exemplified.
The inner side in the radial direction extends along the bead bottom surface 4S, thereby increasing the fitting force with the rim over a wide range.

An inner liner 7 that forms substantially the entirety of the tire cavity is provided inside the main body 6a of the carcass 6.
Are arranged via the insulation rubber 10. The inner liner 7 is made of an air-impermeable rubber mainly composed of butyl rubber such as butyl rubber and halogenated butyl rubber, and has a radially inner end 7E, as shown in FIG.
The bead core 5 ends radially inward from a reference line X passing through the radially inner end in the tire axial direction. Thereby, the filling air is kept airtight.

The insulation rubber 10 is a high-adhesion rubber interposed between the inner liner 7 and the carcass 6 to increase the adhesive strength between the two, and natural rubber is preferably used. In the present example, the radially inner end 10E of the insulation rubber 10 terminates at the same position as the inner end 7E of the inner liner 7, so that the inner end 1E
Similarly, 0E is located radially outward of the reference line X.

In the bead portion 5, a bead core 5 is provided between the insulation rubber 10 and the carcass 6 so as to wrap the carcass body 6a and the folded portion 6b.
It is preferable to provide a code filler 13 that folds the area around a U-shape. The cord filler 13 is formed of, for example, a ply in which steel cords or organic fiber cords are arranged in parallel, and reinforces the bead portion 4 and improves bead rigidity.

The bead portion 4 is provided with a chamfer 9 for preventing rim displacement. The chafer 9 has a base 9A extending from the toe portion 4t to the heel portion 4h of the bead portion 4 facing the bead bottom surface 4S, and rises radially outward along the tire lumen surface at the toe portion 4t. And an upright piece 9B covering the inner end 7E of the inner liner 7 and an outer upright piece 9C rising radially outward along the tire outer surface at the heel portion 4h. It is equipped with

The outer vertical piece 9C is exposed on the outer surface of the tire, and the outermost exposed point P of the outermost piece 9C further extends radially outward beyond the flange contact area where the bead 4 contacts the rim flange. Position. Therefore, the outer standing piece 9C
Can improve the wear strength of the bead portion 4 in cooperation with the base portion 9A, and can prevent damage due to rim displacement. Further, in this example, the outer rising portion 9C extends to the vicinity of the outer end of the bead apex rubber 12 beyond the carcass turn-up portion 6b, and suppresses bead deformation generated during tire running.

The insulation rubber 10 has a bottom surface 10 extending from the inner end 10E to the carcass 6 (cord filler 13 in this example) substantially parallel to the bead bottom surface 4S.
S to stabilize compression under the core.

On the other hand, the radially outer end 9B1 of the inner standing piece 9B terminates radially inward of the reference line X and on the inner surface of the tire, and the inner end 7 of the inner liner 7
E is coated. As a result, the bead portion 4 moves from the tire lumen surface to the bead core 5 on the reference line X.
Up to this point, the chafer 9, the inner liner 7, the insulation rubber 10, and the carcass 6 are arranged in this order toward the outside in the tire axial direction.

Next, the complex elastic modulus E * of the chafer 9 is set to 11 to prevent the toe chipping of the chafer 9 which becomes remarkable in the bead structure having the arrangement order.
13 Mpa, the durometer A hardness H is regulated to 77 to 83 degrees, and the elongation at break is regulated to 300 to 380%.

A conventional chafer generally has a complex elastic modulus E * of about 12.0 Mpa, a durometer A hardness H of about 79 degrees, and an elongation at break EB of about 247%.
Therefore, the chafer 9 of the present application is, as compared with the conventional one,
The elongation at break EB is greatly improved while maintaining the complex elastic modulus E * and the durometer A hardness H at substantially the same level.

The “complex modulus E *” is a value measured at 70 ° C., a frequency of 10 Hz and a dynamic strain of 2% using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho, and the “durometer A hardness H” is , JIS-K6253, a durometer type A, and "elongation at break EB" is a value at a temperature of 20 to 25 ° C.

The chafer 9 has a complex elastic modulus E * of 11.0 MPa or more and a durometer A hardness H of 77 degrees or more.
3A and 3B, it is possible to reduce the set (crushing) of the rubber of the chafer 9 due to the compression as shown in FIGS. 3 (A) and 3 (B).

FIG. 3 (A) shows a case where the tire is assembled on a standard rim specified by a standard such as JATMA and the internal pressure (10 mm).
FIG. 3 (B) shows the measured amount of settling of the chafer 9 in a load state where a load of 5000 kgf was further applied, and FIG. 3 (B) shows the heel point as the origin O and along the rim surface. The measurement is performed at each position which is 5.0 mm apart on the toe side and the flange end side.

As shown in the figure, sample 1 (E * = 9.4 Mp
a, H = 75 degrees), the amount of set off of the rubber was determined in Sample 2 (E
(* = 12.0 Mpa, H = 79 °), there is not much difference in the internal pressure state, but it can be confirmed that the difference greatly increases on the flange end side in the load state. Since the set on the flange end side causes the bead portion 4 to fall outward in the tire axial direction, the amount of repetitive strain acting on the folded portion 6b of the carcass increases,
This results in a significant loss of bead durability.

Therefore, in order to maintain high bead durability, the complex elastic modulus E * of the chafer 9 is set to 11.0M.
pa and the durometer A hardness H must be 77 degrees or more.

On the other hand, in the chafer 9, the standing piece 9
Since the maximum elongation deformation occurs in B, the elongation at break must be 300% or more to withstand this elongation deformation.

Here, the rubber properties in the above range could be achieved by employing fine carbon particles such as L1 carbon as the rubber reinforcing material.

In the conventional chafer, since coarse carbon such as HAF carbon is used as the rubber reinforcing material, the complex elastic modulus E * is 11.0 Mpa or more, and the durometer A hardness H is 77 degrees or more. For example, the elongation at break is about 290% or less, such as 300%.
It was difficult to increase to more than%.

As described above, the chafer 9 of the present invention has a complex elastic modulus E * of 11.0 MPa or more, a durometer A hardness H of 77 degrees or more, and an elongation at break of 300%.
As described above, toe chipping can be effectively prevented while maintaining excellent bead durability. The complex elastic modulus E * is larger than 13.0 Mpa, and the durometer A
When the hardness H is greater than 83 degrees, it is difficult to set the elongation at break to 300% or more, and the effect of preventing toe chipping cannot be exhibited. Conversely, if the elongation at break exceeds 380%, it is difficult to set the complex elastic modulus E * to 11.0 Mpa or more and the durometer A hardness H to 77 degrees or more, leading to a decrease in bead durability. Become.

It should be noted that the present invention can be adopted as various categories of tires, such as tires for passenger cars, tires for light trucks, special tires for construction and industrial vehicles, without being limited to heavy duty tires.

[0033]

Example 1 A tire having a tire size of 11R22.5 and having a structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the toe chipping property, chafer set amount, and folded portion of each test tire were measured. (Repeated strain) and bead durability were measured, and the results are shown in Table 1. Specifications other than the physical properties of chafer are the same. Table 2 shows the compounding of the rubber used in the chafer.

(1) Toe chipping property: A sample tire is rim-assembled to an aluminum wheel rim of size 8.25 × 22.5 using a rim assembly machine (hydraulic tire chainer).
A rim removal test was performed to check for toe chipping. The aluminum wheel rim used is one whose flange is worn out and its surface is scraped, and a paste for lubrication is thinly applied to the bead portion and then wiped off with a cloth.

(2) Settling amount of chafer: FIG.
As in (B), the internal pressure (1000 kPa) and the load (500
The maximum set amount of chafer under a load of 0 kgf) was measured.

(3) Distortion amplitude: The amount of distortion at the folded portion is calculated by finite element method (FEM) analysis, and is indicated by an index with the conventional example being 100. The smaller the value, the smaller the distortion, which is preferable.

(4) Bead durability: Using a drum tester, internal pressure (1000 kPa), load (5000 kg)
f), the vehicle travels at a speed (20 km / h), and the travel distance until bead damage occurs is indicated by an index with the conventional example being 100. The larger the value, the better the durability.

[0038]

[Table 1]

[0039]

[Table 2]

As shown in Table 1, it can be confirmed that the products of Examples have improved both bead durability and toe chipping resistance.

[0041]

[Embodiment 2] The tires of Embodiment 1 (17 tires) and the conventional tire (16 tires) were prepared.
At the end of one life of 000 km or more, the above-mentioned tow chipping test was performed. The results are shown in FIG. 4 together with the rubber hardness of the chafer at the end of one life and the tire inner diameter at the toe portion.

As shown in FIG. 4, in a used tire, the inner diameter of the tire at the toe portion generally tends to increase by about 10 mm and the rubber hardness of the chafer tends to increase by about 3 to 9 degrees by running. The larger the increase in tire radius and the smaller the increase in durometer A hardness, the less the occurrence of toe chipping tends to be. However, in the used tire according to the first embodiment, the generation area YA of the toe chip
However, it can be confirmed that the area of occurrence of the used tires in the conventional example is narrower than the generation area YB, and that the number of recyclable tires can be increased.

[0043]

As described above, according to the present invention, the complex elastic modulus E *, durometer A hardness, and elongation at break of the chafer are specified, respectively, so that the toe chipping can be effected without impairing the bead durability. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the bead portion.

FIGS. 3A and 3B are diagrams showing distribution of chafer sag in an internal pressure state and a load state.

FIG. 4 is a diagram showing an occurrence state of toe chipping in a used tire.

FIGS. 5A and 5B are cross-sectional views illustrating a conventional bead structure.

FIG. 6 is a diagram illustrating a problem of the related art.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Inner liner 7E Inner end 9 Chafer 9B1 Outer end 10 Insulation rubber 10E Inner end 13 Code filler

Claims (2)

[Claims] 1. A carcass which is folded from a tread portion to a sidewall portion and is locked by a bead core of a bead portion, an inner liner which faces the inner surface of the tire and is made of an air-impermeable rubber, and a hard rubber. A chafer and a tubeless tire including an insulation rubber interposed between the carcass and the inner liner in a bead portion, and a reference line X passing through a radially inner end of the bead core in a tire axial direction, A radially inner end of the inner liner and the insulation rubber is located radially inward of the reference line X, and a radially outer end of the chafer is radially outward of the reference line X. On the reference line X, a chafer and an inner liner are disposed on the tire axially outer side from the tire lumen surface to the bead core. Insulation rubber, and while arranging the order of the carcass, the chafer 70 ° C, complex elastic modulus at 2% strain E
*: 11 to 13 Mpa, Durometer A hardness: 77 to 8
A tubeless tire characterized in that the elongation at break is 300 to 380% three times. 2. The tubeless tire according to claim 1, wherein a cord filler turned back by the bead core is interposed between the insulation rubber and the carcass.