JP4044279B2 - Heavy duty radial tire - Google Patents

Description

【００４９】
【表２】

【００５０】
【発明の効果】
叙上の如く本発明は、カーカスのコード径をコンパクト化しつつも、このコード内での錆の発生に起因するコードとゴムの接着カの低下やコードの強度低下、さらにはコードの破断等の損傷を効果的に防止でき、しかも耐疲労性を高め強度保持率を高く維持しうるなど優れた耐久性を発揮できる。
【図面の簡単な説明】
【図１】本発明の一実施例のタイヤの断面図である。
【図２】カーカスコードとして好適な金属コードの一例の断面図である。
【図３】型付けフィラメントの一例を示す側面図である。
【図４】コアの形成過程を説明する線図である。
【図５】（Ａ）、（Ｂ）は、コアの他の例を示す断面図である。
【図６】（Ａ）、（Ｂ）は捻りによる２次元の波の３次元化を説明する線図である。
【図７】（Ａ）〜（Ｃ）は、従来技術を説明する金属コードの断面図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
７ ベルト層
１０ コア
１１ シース
１２ 金属コード
１３、１３Ａ、１３Ｂ フィラメント束
２０ 型付けフィラメント
２１ 非型付けフィラメント
Ｆａ、Ｆｂ フィラメント
Ｙ１ 山部
Ｙ２ 谷部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy-duty radial tire using a metal cord for a carcass that can improve rubber penetration into the cord while reducing the cord diameter.
[0002]
[Background Art and Problems to be Solved by the Invention]
A metal cord obtained by twisting a plurality of metal filaments is often used for a carcass of a heavy duty radial tire. Although such a metal cord is plated on the surface, for example, as shown in FIG. 7A, in the case of a compact cord a having no gap between the filaments f and f, rubber between the filaments is used. As a space is formed that cannot penetrate, the rust is generated or spreads in the cord due to the influence of moisture, resulting in a decrease in the cord-to-rubber bond strength, a decrease in cord strength, and a cord breakage. There was a problem such as.
[0003]
Therefore, in recent years, in order to improve such a problem, as shown in FIG. 7B, a so-called open cord b, which is twisted so that a gap is generated between the filaments, or FIG. As shown in the figure, a metal cord c or the like has been proposed in which a gap between the filaments is formed by twisting a spiral-shaped three-dimensionally shaped filament f1 and a non-typed filament f2 to increase rubber permeability. Yes.
[0004]
However, the above-mentioned cords b and c have a problem that the cord diameter is naturally increased in order to ensure sufficient rubber permeability.
[0005]
Therefore, the present invention has been devised in view of such a situation, and is composed of three filaments in which a two-dimensional typed filament and a nontyped filament are mixed as a core while adopting a layer twist structure. Based on the use of a metal cord twisted while twisting a bundle, the twisting of the mold filament can be made three-dimensional within the core, ensuring sufficient rubber permeability while reducing the cord diameter. An object of the present invention is to provide a heavy-duty pneumatic radial tire using a rusty metal cord for a carcass.
[0006]
Further, in the present invention, before twisting, by limiting the wave height and wave pitch of the molding applied to the filament to a specific range with respect to the filament wire diameter, it is possible to achieve both a reduction in cord strength and rubber permeability. In addition, it is an object to stabilize the tire shape by suppressing the elongation of the cord when the load is low.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application includes a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a belt layer disposed inside the tread portion and outside the carcass. A heavy-duty radial tire with
The carcass cord of the carcass is composed of a metal cord having a twisted layer structure having a core composed of 6 to 12 filaments and a sheath composed of 8 to 15 filaments wound around the core,
The core is formed by twisting two to four filament bundles made of three filaments while twisting each filament bundle, and the filament bundle is in a state before being twisted. It is characterized by including a two-dimensional corrugated filament that repeats peaks and troughs, and a non-molded filament.
[0008]
In the invention of claim 2, the filament of the core has a wire diameter d of 0.15 to 0.30 mm and is substantially the same diameter as the filament of the sheath.
[0009]
According to a third aspect of the present invention, the mold filament satisfies the following formulas (1) to (2) when the wave pitch of the mold is Pw and the wave height is h.
5.0d ≦ Pw ≦ 30.0d (1)
0.2d ≦ h ≦ 3.0d (2)
[0010]
In the invention of claim 4, the twist pitch Pc of the core is 5 to 30 mm, and the twist pitch Pf of each filament bundle is not less than 2 times and not more than 20 times the twist pitch Pc. Yes.
[0011]
The invention according to claim 5 is characterized in that a twist pitch Ps of the sheath is 5 to 30 mm.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a meridional section showing a heavy duty radial tire of the present invention.
[0013]
In FIG. 1, a heavy-duty radial tire 1 (hereinafter referred to as a tire 1) includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and an inner end of each sidewall portion 3. The bead portions 4 and 4 are provided with a toroidal carcass 6 laid over the bead portions 4 and 4, and a tough belt layer 7 is wound inside the tread portion 2 and outside the carcass 6. Has been.
[0014]
The belt layer 7 is usually formed of 3 to 4 belt plies. In this example, the belt layer 7 includes an innermost belt ply 7A in which belt cords using metal cords are arranged at an angle of, for example, about 60 ± 15 ° with respect to the tire circumferential direction, and 15 to The case of a four-sheet structure with belt plies 7B, 7C, 7D arranged at a small angle of 35 ° is illustrated, and one or more places where belt cords cross each other are provided and overlapped.
[0015]
Next, the carcass 6 is folded around the bead core 5 from the inner side to the outer side around the bead core 5 on both sides of the body portion 6a from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. A bead apex rubber 8 is provided between the body portion 6a and the folded portion 6b. The bead apex rubber 8 extends from the bead core 5 to the outside in the tire radial direction.
[0016]
The carcass 6 is formed of 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.
[0017]
Here, as carcass cords used for heavy duty tires such as trucks and buses, conventionally, since high strength is required, for example, a 3 + 9 configuration or a 3 + 9 + 15 configuration, a layer twist structure with a large number of filaments Has been used extensively. This is because when the filament is thickened, the tensile strength per cross-sectional area tends to decrease. Therefore, in order to increase the strength with the same amount of steel, it is necessary to increase the number of thin filaments. is there.
[0018]
Therefore, in the present invention, in particular, it can be used preferably in place of the metal cords such as the 3 + 9, 3 + 9 + 15 configuration and the like, which are frequently used in the carcass of the heavy-duty radial tire, and with sufficient fatigue resistance. As shown in FIG. 4, a layered twisted metal cord having a core 10 composed of 6 to 12 filaments Fa and a sheath 11 composed of 8 to 15 filaments Fb wound around the core 10 as a carcass cord 12 is used.
[0019]
The metal cord 12 has a great feature in that the core 10 is formed as follows in order to sufficiently secure rubber permeability while reducing the cord diameter.
[0020]
That is, the core 10 is composed of two to four filament bundles 13 formed by aligning three filaments Fa. Accordingly, the total number of filaments Fa forming the core 10 is a multiple of 3, that is, 6, 9, or 12, and in this example, the case of 12 is illustrated.
[0021]
Further, as shown in FIG. 4, each filament bundle 13 is twisted around its axis or simultaneously with the twisting, and the filament bundles 13 are twisted together to form one core 10. .
[0022]
At this time, the three filaments Fa forming the filament bundle 13 are composed of a mold-molding filament 20 and a non-mold-molding filament 21. In this example, a filament bundle 13A made up of two typed filaments 20 and one non-typed filament 21 and a filament bundle 13B made up of one typed filament 20 and two non-typed filaments 21 coexist. Although the case is illustrated, the core 10 can be formed only by the filament bundle 13A... Or only by the filament bundle 13B.
[0023]
The non-molded filament 21 is a conventional filament that is substantially linear before being twisted together.
[0024]
On the other hand, as shown in FIG. 3, the mold filament 20 is molded in a two-dimensional wave shape that repeats wave peaks Y1 and valleys Y2 before being twisted together. In this example, The case where the zigzag shape which made the linear part Y3 intervene between the said peak part Y1 and the trough part Y2 is made is illustrated. It is also possible to form a sine curve or the like consisting only of a curve.
[0025]
The two-dimensional embossing filament 20 twists the filament bundle 13 to make the two-dimensional wave three-dimensional.
[0026]
Here, the three-dimensionalization of the two-dimensional wave is described as follows. That is, as conceptually shown in FIG. 6A, when a twist K1 is added to the filament bundle A, the twist K1 is reflected on each filament B as a similar twist K2. At this time, in the case where the filament bundle A includes the mold filament B1, each mold filament B1 is twisted around the center by the twist K2 as shown in FIG. It becomes three-dimensional.
[0027]
By making the two-dimensional wave three-dimensional by twisting in this way, a sufficient gap can be stably secured between the filaments Fa and the filaments Fb, and the rubber permeability is greatly increased while suppressing the elongation at low loads. It can be improved. Further, by ensuring the gap, fretting (a phenomenon in which a relatively small amount of relative slip occurs between the filaments and wears) is suppressed, so that fatigue resistance is further improved.
[0028]
Further, this three-dimensionalization has an advantage that the code can be made compact as compared with, for example, a three-dimensional spiral type from the beginning. In particular, as in this example, when the corrugated shape having the straight portion Y3 is used, it is preferable because it is easy to ensure a gap between the filaments when twisted even if the wave height h of the molding is relatively small. . In addition, the two-dimensional molding is easier to process than the three-dimensional molding such as a spiral shape, and has high dimensional accuracy, excellent shape stability, and easy handling. Is also advantageous.
[0029]
Here, the total number of filaments Fa of the core 10 and the total number of filaments Fb of the sheath 11 are set from the above ranges according to the required strength when used for a carcass cord. 9 or 12 are preferable for the filament Fa.
[0030]
Further, the wire diameter d of the filament Fa and the wire diameter d of the filament Fb are also set in relation to the strength required for the carcass cord, but in the range of 0.15 to 0.30 mm for heavy duty tires, If it is less than 0.15 mm, it is too thin and disadvantageous in terms of cord strength. Conversely, if it exceeds 0.30 mm, it is disadvantageous in terms of bending fatigue.
[0031]
Further, it is desirable to use filaments Fa and filaments Fb having the same diameter, whereby the wire drawing process can be made common and the cord can be manufactured economically.
[0032]
For the filaments Fa and Fb, it is preferable to use a hard steel wire having a carbon content of 0.78 to 0.86%. If the content is less than 0.78%, the strength tends to decrease and exceeds 0.86%. The hardness is too high and there is a tendency for the strength to decrease greatly during molding.
[0033]
Next, in the mold filament 20, as shown in FIG. 3, when the wave pitch of the mold before being twisted is Pw and the wave height is h, the relationship of the following formulas (1) to (2) is satisfied. It is preferable to do. The wave pitch Pw is the distance in the longitudinal direction between the peaks Y1 and Y1, and the wave height h is the distance in the amplitude direction between the peaks Y1 and the valley Y2.
5.0d ≦ Pw ≦ 30.0d (1)
0.2d ≦ h ≦ 3.0d (2)
[0034]
This is because if the wave height h is less than 0.2 times the wire diameter d, it is difficult to ensure rubber permeability. This is because the damage received is large and causes a decrease in the strength of the filament.
[0035]
On the other hand, if the wave pitch Pw is less than 5.0 times the wire diameter d, the wave pitch Pw becomes too small, and the damage caused by the shaping process is large, which causes a decrease in the strength of the filament. If it exceeds 1, the wave pitch Pw will become too large, and rubber permeability will fall.
[0036]
The twist pitch Pc (shown in FIG. 4) when the filament bundle 13 is twisted to form one core 10 is preferably 5.0 to 30.0 mm, and the twist of the twist applied to each filament bundle 13 is also preferred. The pitch Pf (shown in FIG. 4) is preferably a relatively long pitch of 2 to 20 times the twist pitch Pc.
[0037]
If the twist pitch Pc is smaller than 5.0 mm, the initial elongation of the cord is increased, the shape change when applied to the tire is increased, and the cord strength is reduced. When the pitch Pc exceeds 30.0 mm, the filaments are easily broken and there is a disadvantage that the shape retaining property of the cord is deteriorated.
[0038]
Also, if the twist pitch Pf is less than 2.0 times the twist pitch Pc, the gap between the filaments is reduced and the rubber permeability is lowered. Conversely, if the twist pitch Pf exceeds 20 times, the effect of three-dimensionality is reduced, and Between the filament bundles 13, 13, there is a problem that the molds are easily overlapped with each other. Therefore, the twist pitch Pf is more preferably in the range of 3 to 10 times the twist pitch Pc.
[0039]
Further, the twist pitch Ps of the filament Fb forming the sheath 11 is preferably in the range of 5.0 to 30.0 mm. If it is less than 5.0 mm, the elongation of the cord at a low load becomes large, and conversely 30.0 mm If it exceeds 1, filaments will be easily broken, and the cord shape retention will be poor. The twist pitch Ps is preferably set larger than the twist pitch Pc from the viewpoint of cord shape stability.
[0040]
In this example, the twist direction of the sheath 11 is different from the twist direction of the core 2. However, it may be matched, and the twist direction of the filament bundle 13 is also the core 2 in this example. Although the case where it is made to correspond with the twist direction of is illustrated, you may make it differ.
[0041]
FIGS. 5A and 5B show another embodiment of the core 10. FIG. 5A illustrates the case where the core 10 is composed of three filaments 13A. In FIG. 5B, the core 10 is composed of two filaments 13A and one filament 13B. The case where it comprises is illustrated.
[0042]
As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.
[0043]
【Example】
In order to confirm the effect of the present invention, a metal cord was prototyped according to the specifications shown in Table 1, and the characteristics of the sample cord and the tire performance when the sample cord was used as a carcass cord were compared and evaluated. The tire specifications are shown in Table 2 and are the same except for the carcass cord.
The definitions of terms in the table are as follows.
[0044]
(1) Rubber permeability:
A tire having a carcass using a sample metal cord is manufactured, and the metal cord is taken out from the tire with a topping rubber attached thereto. After removing rubber from the surface of the cord with rubber as much as possible, put a knife from the cross section and remove two adjacent filaments out of 8-12 filaments, and remove the two removed filaments and the remaining filaments. The length of the portion where the rubber is completely filled in the gap formed between the filament bundle is measured over about 10 cm, and the ratio of the length of the portion filled with rubber to the total length of the rubber penetrates. Rate. The above measurement is performed on ten cords, and the average value is taken as the cord measurement value.
[0045]
(2) Cord bending stiffness:
The bending stiffness of the metal cord was measured using a “V-5 stiffness tester” manufactured by Taba (USA).
[0046]
(3) Rust generation after running:
After running the tire for about 200,000 km, the tire is disassembled and the state of occurrence of rust on the metal cord is observed, and the comparison target cord is set to 100. The smaller the value, the less rust is generated and the better.
[0047]
(4) Strength retention after running:
After running the tire for about 200,000 km, the tire is disassembled and the metal cord is taken out, and the strength of the cord before running is indicated by an index of 100. The larger the value, the better.
The test results are shown in Table 1.
[0048]
[Table 1]

[0049]
[Table 2]

[0050]
【The invention's effect】
As described above, the present invention reduces the cord diameter of the carcass while reducing the adhesive strength between the cord and the rubber due to the occurrence of rust in the cord, the strength of the cord, and the breaking of the cord. It is possible to effectively prevent damage and to exhibit excellent durability such as high fatigue resistance and high strength retention.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an example of a metal cord suitable as a carcass cord.
FIG. 3 is a side view showing an example of a shaping filament.
FIG. 4 is a diagram illustrating a core formation process.
FIGS. 5A and 5B are cross-sectional views showing other examples of the core. FIGS.
6A and 6B are diagrams illustrating three-dimensionalization of a two-dimensional wave by twisting.
FIGS. 7A to 7C are cross-sectional views of metal cords for explaining the prior art.
[Explanation of symbols]
2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 10 Core 11 Sheath 12 Metal cord 13, 13A, 13B Filament bundle 20 Typing filament 21 Non-typed filament Fa, Fb Filament Y1 Mountain portion Y2 Valley portion

Claims (5)

A heavy duty radial tire comprising a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion and a belt layer disposed inside the tread portion and outside the carcass,
The carcass cord of the carcass is composed of a metal cord having a twisted layer structure having a core composed of 6 to 12 filaments and a sheath composed of 8 to 15 filaments wound around the core,
The core is formed by twisting two to four filament bundles made of three filaments while twisting each filament bundle, and the filament bundle is in a state before being twisted. A heavy-duty radial tire comprising a two-dimensional wave-shaped mold filament that repeats a peak and a valley and a non-mold filament. The radial tire for heavy loads according to claim 1, wherein the filament of the core has a wire diameter d of 0.15 to 0.30 mm and substantially the same diameter as the filament of the sheath. The radial for heavy loads according to claim 1 or 2, wherein the mold filament satisfies the relationship of the following formulas (1) to (2) when the wave pitch of the mold is Pw and the wave height is h. tire.
5.0d ≦ Pw ≦ 30.0d (1)
0.2d ≦ h ≦ 3.0d (2) The twist pitch Pc of the core is 5 to 30 mm, and the twist pitch Pf of each filament bundle is not less than 2 times and not more than 20 times the twist pitch Pc. Radial tire for heavy loads as described in Crab. The radial tire for heavy loads according to any one of claims 1 to 4, wherein a twist pitch Ps of the sheath is 5 to 30 mm.

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