JP2001246909A - Radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve external flaw resistance, breaking resistance and economic efficiency. SOLUTION: This radial tire includes a belt cord formed by stranding one formed filament FA with 0.03 to 0.45 mm of line diameter d and two non-formed filaments FB with 10 to 40 mm of a twist pitch Pc. The line diameter d, a wave pitch Pw and wave height h of the formed filament satisfy the following expressions (1), (2). 5.0d<=Pw<=30.0d (1) 0.2d<=h<=3.0d (2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a filament having a large diameter and a reduced number of filaments, so that the filament is hard to be cut and has excellent economical efficiency. The present invention relates to a heavy duty radial tire excellent in trauma resistance and rupture resistance using a cord formed in a belt layer.

[0002]

2. Description of the Related Art Various rubber materials, for example, a belt layer of a pneumatic radial tire often use a metal cord in which a plurality of metal filaments are twisted. Although such metal cords are plated on the surface, the effect of moisture causes the rust to occur or spread in the cords, which lowers the adhesive strength between the cords and rubber and reduces the strength of the cords. There have been problems such as lowering and further breakage of the cord.

In recent years, in order to solve such problems, so-called open cords twisted so as to generate gaps between metal filaments, and one or more metal filaments constituting the cords are three-dimensionally formed. It has been proposed to form a gap between metal filaments by twisting after forming in a spiral shape as described above to increase the permeability of rubber inside the cord.

However, the above-described cord has a disadvantage that the cord diameter naturally increases in order to ensure a sufficient rubber permeability.

The present invention has been devised in view of such a situation, and a cord is formed by twisting a two-dimensionally shaped shaping filament having a specific shape with two non-shaping filaments. It is an object of the present invention to provide a heavy duty radial tire using a metal cord for a belt layer that can secure rubber infiltration between filaments.

Further, in the present invention, before twisting, the wave height, wave pitch, etc., of the shaping applied to the filament are limited to a specific range with respect to the filament diameter, so that the finally twisted cord is twisted. The purpose is to achieve both a reduction in strength and rubber penetration.

[0007]

According to a first aspect of the present invention, there is provided a carcass extending from a tread portion to a bead core of a bead portion from a sidewall portion to a bead portion, and a carcass is provided inside a tread portion and outside the carcass. A heavy duty radial tire having a belt layer composed of a plurality of belt plies arranged, wherein the belt layer is twisted with a cord in a belt cord of at least two belt plies including a radially outermost belt ply. A wire diameter d composed of one shaped filament and two non-shaped filaments formed in a two-dimensional wave shape that repeats peaks and valleys of waves in a state before being combined is 0.30 to 0. A metal cord obtained by twisting three metal filaments each having a diameter of .45 mm at a twist pitch Pc of 10 to 40 mm is used. The attached wave pitch Pw and wave height h are:
It is a radial tire for heavy load characterized by satisfying the relationship of the following formula. 5.0d≤Pw≤30.0d ... 0.2d≤h≤3.0d ...

According to a second aspect of the present invention, there is provided the radial tire for heavy load according to the first aspect, wherein the molding filament satisfies the following relationship. 0.014 ≦ d × h / Pw ≦ 0.028 ...

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section in the case where the present invention is a radial tire for heavy loads such as for trucks and buses.

In FIG. 1, a radial tire for heavy load (hereinafter referred to as tire 1) has a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and an inner portion of each sidewall portion 3. A toroidal carcass 6 spans the bead portions 4, 4 and the tread portion 2.
A tough belt layer 7 is wound inside and outside of the carcass 6.

The carcass 6 is provided on both sides of a main body 6a extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3, and is provided with a folded portion which is turned around the bead core 5 from inside to outside in the tire axial direction. 6b are provided integrally, and between the main body 6a and the folded portion 6b,
A bead apex rubber 8 extending in a tapered shape from the bead core 5 outward in the tire radial direction is disposed.

The carcass 6 is formed from one or more carcass plies in which carcass cords are radially arranged at an angle of 70 to 90 ° with respect to the tire circumferential direction. In this example, the case where the carcass 6 is composed of one carcass ply 6A in which carcass cords are arranged at an angle of 90 ° is illustrated.

Next, the belt layer 7 has a plurality of layers,
It is formed from up to four belt plies. In this example,
The case where the belt layer 7 is formed of first to fourth belt plies 7 </ b> A to 7 </ b> D sequentially arranged from the carcass 6 side toward the radial outside is illustrated.

The first belt ply 7A disposed on the innermost side in the radial direction has a belt cord arranged at an angle of, for example, about 50 ± 20 ° with respect to the tire circumferential direction, and second, third, and fourth belt plies. Belt plies 7B to 7D are 15 to 35
The belt cords are arranged at an angle of about ゜. The inclination direction of the cord with respect to the tire equator C is different between the second and third belt plies 7B and 7C, thereby forming a strong truss structure and reinforcing the tread portion 2 with a tag effect. .

In the present application, the belt plies 7A-
7D, at least two belt plies including the fourth belt ply 7D that is the outermost in the radial direction, in this example,
As shown in FIGS. 2 and 3, the belt cords of the fourth and first belt plies 7D and 7A have a wire diameter d of one molding filament FA and two non-molding filaments FB having a diameter of 0.30. 1 × in which three metal filaments F of ~ 0.45 mm are twisted at a twist pitch Pc of 10 to 40 mm
The metal cord 10 having three configurations is used.

Conventionally, a metal cord used for a belt layer of a heavy-duty radial tire used for a truck, a bus or the like has a 3 + 6 configuration (including a total of nine filaments and two types of filament diameters). , 2
A +7 configuration (9 total filaments, one type of filament diameter), a 3 + 9 + 15 configuration (27 total filaments, one type of filament diameter), and the like have been frequently used.

In general, increasing the diameter of the filament and reducing the number of filaments are advantageous in terms of cost and productivity in producing a cord, and are also excellent in breaking resistance. In addition, there is an advantage that the smaller the number of filaments, the more easily the rubber penetrates into the cord.

Therefore, in the present invention, the 3 + 6, 2+
Three metal filaments F having a wire diameter d of 0.30 to 0.45 mm were used in place of a metal cord having a +7 configuration (a total of 9 filaments), so that the number of filaments could be reduced, and particularly preferable. The metal cord 10 is used.

When the wire diameter d of the metal filament F is less than 0.30 mm, it becomes difficult to obtain the required rigidity as a reinforcing cord material for a belt layer of a heavy-duty radial tire with three filaments. Even if the filament is corrugated as described above, the molding applied before twisting the cord tends to return to the original shape at the time of twisting, and the rubber permeability tends to be insufficient. On the other hand, when the wire diameter d exceeds 0.45 mm, the distortion at the time of applying the corrugated mold becomes too large, the strength of the filament is greatly reduced, and the flexibility of the cord required at the time of tire production cannot be obtained. .

Preferably, the metal filament is usually plated with a metal in order to enable vulcanization bonding with the rubber composition. In the present embodiment, all the filaments constituting the cord are the same wire. An example having a diameter is illustrated.

As shown in FIGS. 2 to 4, the metal filament F has a wave pitch Pw, before being twisted.
One two-dimensional corrugated filament FA having a wave height h and alternately repeating peaks U and valleys D of the wave, and the remaining (two) non-corrugated filaments FB
(Shown in FIGS. 2, 3 and the like). In this example, the straight portion 1 is located between the peak U and the valley D as a mold.
Although a zigzag shape with 3 interposed is illustrated, a sine curve shape or the like consisting of only a curve may be used. The wave pitch Pw and wave height h are measured as shown in FIG.

Further, in the present invention, by limiting the molding of the molding filament FA to a two-dimensional wave shape,
For example, the cord diameter can be made more compact than that formed in a spiral shape, and particularly in the case of a zigzag type having a straight portion 13 as in this example, the wave height h
Even if the size is relatively small, it is easy to secure a gap between the filaments when twisted, and it is preferable because the permeability of the rubber into the cord is further improved.

As described above, the molding filament FA plays an important role in ensuring the permeability of the rubber into the cord, but the metal filament F having a relatively large wire diameter d as in the present invention is used. In the case of forming a cord by applying a corrugated pattern, the strength of the metal filament F tends to decrease.

Therefore, in the present invention, in order to minimize such inconvenience, the number of molding filaments FA used for the metal cord 10 is limited to one.

Further, the metal cord 10 of the present embodiment is characterized in that it is formed by twisting at a final twist pitch Pc of 10 to 40 mm.

By combining one molding filament FA and two non-molding filaments FB, and by limiting the shape of the corrugated molding, it is possible to efficiently secure the permeability of rubber. It is not necessary to use a short twist pitch in order to ensure rubber penetration at the time of the final twist, and it is possible to adopt a long twist pitch as compared with the filament wire diameter d of 10 mm to 40 mm, and consequently to increase cord productivity. Can also be improved.

As a result of various experiments conducted by the present inventors, when a cord having a limited wire diameter d and including a specific number of shaped filaments FA is manufactured, the wire diameter d, It has been found that it is important that the wave pitch Pw and the wave height h of the shaping satisfy the relationship of the following equation. 5.0d≤Pw≤30.0d ... 0.2d≤h≤3.0d ...

This is because if the wave pitch Pw is less than 5.0 times the wire diameter d, the wave pitch Pw becomes too small, and the forming filament FA
The reason for this is that the damage caused to the filament is large and causes a decrease in the strength of the filament. Conversely, if it exceeds 30 times, the wave pitch Pw becomes too large, and the permeability of the rubber decreases. Therefore, it is preferably in the range of 10.0 to 25.0 times.

If the wave height h is less than 0.2 times the wire diameter d, it becomes difficult to ensure rubber permeability,
On the other hand, if it exceeds 3.0 times, the molding filament FA is greatly damaged by the molding process, which causes a decrease in the strength of the filament. Therefore, it is preferably in the range of 0.5 to 2.0 times.

On the other hand, the present inventors have found that d × h / Pw comprising the wire diameter d, the shaping wave pitch Pw, and the wave height h.
The value of d × h / Pw was determined to be 0.014 to 0.028 when the strength reduction rate (%) and the rubber permeability (%) of the cord were examined by variously changing this value. It has been found that a more remarkable effect is exhibited by limiting the range.

FIG. 5 shows the relationship between the cord strength reduction rate (%), the rubber penetration rate (%), and the parameter d × h / Pw. As is clear from this figure, d × h / P
It can be seen that as w increases, the strength reduction rate of the cord increases and the performance deteriorates, but the rubber permeability increases. Therefore, in order to keep the strength reduction rate of the cord within an allowable range and at the same time to increase the permeability of the rubber, the d × h / Pw value is
0.014 to 0.028, further 0.020 to 0.0
It is preferably 25. The strength reduction rate (%) and the rubber permeability (%) here are in accordance with the definitions in Examples (described later).

For the metal filament F, for example, a hard steel wire having a carbon content of 0.65 to 0.95 wt% is preferably used. When the carbon content of the metal filament F is less than 0.65%, the strength of the filament tends to decrease. Conversely, when the carbon content exceeds 0.95% by weight, the hardness of the filament is too high, and the strength decreases greatly during molding. Tend to be.

The metal cords 10 are arranged in parallel at equal intervals and covered with a topping rubber, so that the fourth belt ply 7D, which is the outermost in the radial direction among the belt plies 7A to 7D, as described above. Are formed, in this example, fourth and first belt plies 7D and 7A.

By using the metal cord 10 for the outermost belt ply 7D, the characteristics of the metal cord 10 can be more effectively exhibited, and the tire can be used in a manner such as to prevent the tire from being damaged.
This is because the rupture resistance is improved and the economic efficiency is improved. By using the innermost belt ply 7A, the economy can be further improved.

In the present embodiment, the second and third belt plies 7B and 7C are formed by using a conventional belt cord such as a 2 + 7 structure using non-shaped filaments. , Third belt plies 7B, 7C
Can be further formed using the metal cord 10.

The number of metal cords 10 included in a unit length of the ply in a direction perpendicular to the longitudinal direction of the cords, that is, the number of so-called cords, is set variously in accordance with the required tire specifications. If the number of cords is too small, the cord arrangement is likely to be disturbed, such as uneven cord spacing during vulcanization molding, etc. Conversely, if the cord spacing is too small, it will be between adjacent cords when running tires. The strain of the sandwiched rubber increases, and the durability of the tire tends to decrease due to the occurrence of cracks and the like in the rubber layer.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but may be implemented in various forms.

[0038]

EXAMPLES In order to confirm the effects of the present invention, various metal cords were trial-produced according to the specifications shown in Tables 1 and 2, and the comparative evaluation was made on the characteristics of the trial cords and the tire performance when the trial cords were used as belt cords. went. The specifications of the tire are shown in Table 3, and all the specifications other than the table are the same. The definitions of the terms in the table are as follows.

<Strength reduction rate> A cord having a compact structure (hereinafter referred to as "comparative cord") which is made of a material having the same composition (having the same composition such as carbon content) and the same number of metal filaments and twisted at the same twist pitch. ), Which is measured in a state before the tire is used. The smaller the numerical value is, the less the strength decreases and the better.

<Elongation under load> Elongation of a cord when a load of 50 N is applied to one cord.

<Bending rigidity>"V-
The bending stiffness of the cord was measured using a “5 stiffness tester”.

<Rubber Permeability> A tire having a belt layer using a sample metal cord is manufactured, and the metal cord is removed from the tire with the topping rubber attached. After removing rubber as much as possible from the surface of the rubber cord, a knife is inserted from the cross section to remove two adjacent filaments out of 5 to 6 filaments, and the removed two filaments and the remaining two filaments are removed. The length of the portion where rubber is completely filled in the gap formed between the bundle of filaments is measured over about 10 cm, and the ratio of the length of the portion filled with rubber to the total length is expressed as a ratio of the length of the rubber. Permeability. The above measurement is performed for ten codes, and the average value is used as the measured value of the code.

<Rust generation after running>
After running, the tires were disassembled and the occurrence of rust on the metal cords was observed. The smaller the numerical value, the better the less rust is generated.

<Strength Retention after Running> After the tire has been run for about 200,000 km, the tire is disassembled and the metal cord is taken out. The higher the value, the better. Tables 1 and 2 show the test results.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

As described above, the radial tire for heavy load according to the present invention increases the wire diameter of the filament in the metal cord used for the belt layer, secures the advantages in cost and production, and reduces the cord diameter. The rubber permeability into the inside of the cord can be increased while reducing the size of the cord. Therefore, it is possible to suppress the occurrence of rust inside the tire of the metal cord, to effectively prevent the strength reduction or breakage of the cord,
The durability of the tire can be improved. In addition, the cord can exhibit excellent properties comparable to those of the compact cord in terms of the strength of the cord, the strength reduction rate, the elongation under load (at 50 N), and the bending rigidity of the cord. Further, since the tire is used for at least two belt plies including the outermost belt ply, it is possible to effectively improve the scratch resistance, rupture resistance, and economy of the tire.

[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 a perspective view of an example of a metal cord suitable as a belt cord.

FIG. 3 is a sectional view thereof.

FIG. 4 is a plan view showing an example of a molding filament.

FIG. 5 shows the rate of decrease in cord strength, rubber penetration, and d × h /
It is a graph which shows the relationship of Pw.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 7A to 7D belt ply 10 Metal cord F Metal filament FA Molding filament FB Non-molding filament U Peak part D Valley part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazumi Yamazaki 3-6-9, Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture Within Sumitomo Rubber Industries, Ltd. (72) Inventor Attack Atsushi Toda 3 6-9, Sumitomo Rubber Industries Co., Ltd. (72) Inventor Yasuo Sakai 1-1-1, Kunyokita, Itami-shi, Hyogo F-term in Sumitomo Electric Industries, Ltd. Itami Works 3B153 AA06 BB01 BB13 CC51 FF16 GG01 GG05 GG07 GG40

Claims (2)

[Claims] 1. A heavy-duty vehicle comprising: a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion; and a belt layer including a plurality of belt plies disposed inside the tread portion and outside the carcass. A radial tire, wherein the belt layer has a peak portion and a valley portion of a wave before being twisted with the cord, to a belt cord of at least two belt plies including a radially outermost belt ply. A three-dimensional metal filament having a wire diameter d of 0.30 to 0.45 mm composed of one shaped filament and two non-shaped filaments which are repeatedly formed in a two-dimensional wavy shape has a twist pitch Pc of 10 to 40 mm. The wire diameter d of the molding filament, the wave pitch Pw of the molding, and the wave height h are represented by the following formulas. A radial tire for heavy loads characterized by satisfying. 5.0d≤Pw≤30.0d ... 0.2d≤h≤3.0d ... 2. The heavy duty radial tire according to claim 1, wherein the molding filament satisfies the following relationship. 0.014 ≦ d × h / Pw ≦ 0.028 ...