JP2000016012A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for passenger car whose motion performance is enhanced by forming a carcass from steel cords and in which the anti-fatigue characteristic of the carcass is improved. SOLUTION: At least one carcass ply 2 is formed from steel cords embedded, and each steel cord is composed of one core filament and 3-6 sheath filaments arranged around the core filament, and the core filament is shaped by a die in spiral or undulate form, wherein the relations 0.20<=Rc<=4.8 and 2.0 dc/0.20<=Pc<=15.0dc/0.15 should be met, where Rc=(Lc/dc) is the ratio of the amplitude Lc of die shaping in spiral or undulate form to the element wire diameter dc of core filament and Pc is the pitch of the spiral or undulate form of the core filament.

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 for a passenger car having improved exercise performance and improved carcass fatigue resistance.

[0002]

2. Description of the Related Art Generally, in a radial tire for trucks and buses, a steel cord is used as a reinforcing material for a belt and a carcass. In a radial tire for a passenger car,
The belt is made of steel cord, and the carcass is made of textile cord, such as polyester, nylon or rayon, which has excellent fatigue resistance.

[0003] However, radial tires for passenger cars using a textile cord for the carcass have insufficient resistance to trauma, which is likely to occur when the tire side portion comes into contact with a curb, and poor adhesion between the cord and rubber tends to occur. This may lead to cord breakage or separation. Further, the textile cord generally has a low bending rigidity, and it is difficult to increase the rigidity of the side portion of the tire, so that there is a disadvantage that the interlocking performance is limited.

On the other hand, it has been proposed to apply a steel cord to a carcass of a radial tire for a passenger car in place of a textile cord.
No. 03 proposes to use, as a carcass, a steel cord having a 1 + n structure including one core filament and n sheath filaments disposed around the core filament. As a result, the above disadvantages are solved, but the following new problems arise. That is, the steel cord used for the carcass is subjected to repeated bending and compression deformation over a long period of time along with the rolling of the tire, and particularly, the steel cord in the carcass portion adjacent to the belt is subjected to a lateral force when steering the vehicle. Compression deformation
By repeating this, the material fatigue of the cord progresses, and the cord is broken. Therefore, in order to apply a steel cord to a carcass of a radial tire for a passenger car, it is important to improve the fatigue resistance of the steel cord.

On the other hand, in recent years, application to a pneumatic tire (hereinafter referred to as a "pneumatic safety tire") capable of performing high performance of a radial tire and running at an inner pressure of 0 kg / cm ² , that is, so-called run flat running, is known. However, there is a problem that the compressive deformation applied to the steel cord is increased, and particularly, a straight core filament is apt to be broken prematurely.

[0006] In addition, a radial tire in which a 1 + n steel cord formed by spirally or corrugating a core filament is also known (JP-A-5-418969, JP-A-6-191219 and JP-A-6-191219). JP-A-8-232179), all of which are studied as belt materials, and specifically studied for application to a carcass that is particularly compressed due to buckling because it extends in the radial direction. is not.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire for a passenger car in which a steel cord is used for a carcass to enhance athletic performance and improve carcass fatigue resistance.

[0008]

Means for Solving the Problems The present inventor has conducted intensive studies on a steel cord applicable to a carcass ply of a pneumatic tire in order to solve the above-mentioned problems. It has been found that the above object can be achieved by the following means, and the present invention has been completed.

That is, the pneumatic tire of the present invention has a pair of left and right ring-shaped bead cores and both ends of a carcass ply composed of a layer in which a plurality of parallel cords are embedded in a covering rubber. A carcass portion that is folded back and formed in an annular shape, a belt portion including a plurality of layers of belt plies disposed outside the carcass portion in the tire radial direction, and disposed outside the belt portion in the tire radial direction. In a pneumatic tire including an annular tread portion and a pair of sidewall portions disposed on the left and right sides of the tread portion, at least one embedded cord of the carcass ply is formed of a steel cord, and the steel cord is A core filament and three, four, five or six sheath filaments disposed around the core filament; The core filaments are typed spiral or waveform, amplitude Lc of typed spiral or waveform
And the pitch Pc of the helical or corrugated shape of the core filament are expressed by the following equation: 0.20 ≦ Rc ≦ 4, respectively. .8 2.0 dc / 0.20 ≦ Pc ≦ 15.0 dc / 0.15.

In another pneumatic tire according to the present invention, both ends of a carcass ply composed of a pair of left and right ring-shaped bead cores and a layer in which a plurality of cords arranged in parallel are embedded in a covering rubber are provided. A carcass portion which is folded back and formed in an annular shape, a belt portion composed of a plurality of layers of belt plies arranged outside the carcass portion in the tire radial direction, and arranged outside the belt portion in the tire radial direction. In the pneumatic tire comprising the annular tread portion and a pair of sidewall portions disposed on the left and right sides of the tread portion, at least one embedded cord of the carcass ply has one core filament, A steel cord consisting of three, four, five or six sheath filaments disposed around the core filament; Instrument, characterized in that the carbon content is comprised of hypo folding steel of less than 0.7%.

[0011]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a steel cord having the above-mentioned spiral or corrugated core filament or a core filament made of sub-co-folded steel having a carbon content of less than 0.7% is provided. By using the steel cord for the carcass ply, the premature breakage of the straight core filament in the conventional 1 + n structure steel cord is prevented, and the fatigue resistance of the steel cord for reinforcing the carcass ply is improved. Specifically, in a steel cord having a core filament shaped into a spiral or corrugation, the main aim is to improve compression fatigue resistance by a spring effect by shaping, and as a secondary effect, Improvement in rubber permeability into the interior is also obtained. On the other hand, the use of a steel cord having a core filament made of sub-co-folded steel having a carbon content of less than 0.7% is intended to improve fatigue resistance in terms of its material.

The steel cord having a helically or corrugated core filament comprises one core filament and three, four, five or six sheath filaments disposed around the core filament. . Helical or corrugated shaping amplitude Lc of the core filament and element diameter dc of the core filament
(FIG. 3) and the type ratio Rc (= Lc / d)
c) satisfies the relationship represented by the following expression: 0.20 ≦ Rc ≦ 4.8, preferably, the following expression: 1.0 ≦ Rc ≦ 2.4. The value of this Rc is 0.20
If it is smaller, the molding effect is hardly exhibited, and the arrangement of the filaments constituting the cord is dispersed, the spacing between the sheaths is properly secured, and the effect of penetrating the rubber into the cord is insufficient. As a result, the fatigue resistance to the cord is reduced. The improvement effect becomes insufficient. On the other hand, if the value of Rc exceeds 4.8, the code properties deteriorate, which is not preferable.

The spiral or corrugated pitch Pc (FIG. 3) of the core filament is given by the following equation: 2.0 dc / 0.20 ≦ Pc ≦ 15.0 dc / 0.1
5, preferably satisfies the relationship represented by the following equation: 4.0 dc / 0.20 ≦ Pc ≦ 8.0 dc / 0.15 The value of this Pc is 15.0
If it is larger than dc / 0.15, the effect of dispersing the arrangement of the sheath filaments, properly securing the sheath interval, and permeating the rubber into the cord is insufficient, while Pc is 2.0 dc.
If it is less than /0.20, the core filament will have a lower strength due to the load on the core filament during molding, and the core filament and the sheath filament will not receive a uniform load during the tensile load on the cord. descend. The mold ratio Rc and the spiral or corrugated pitch Pc in the present invention are determined by measuring a steel cord taken out of the tire without applying plastic deformation.

In the case of a spirally shaped core filament, the twist direction is preferably opposite to the twist direction of the sheath filament. This is because rubber permeability into the cord is further increased.

In the present invention, at least the core filament of the steel cord described above, obtained by subjecting a filament drawn by die drawing to a bluing treatment at 380 to 430 ° C., has a breaking elongation of at least 3.5%, preferably at least 3.5%. Can be a filament of 4.0% or more. Specifically, a cord obtained by twisting one or more stranded filaments may be used, or a cord obtained by twisting one or more drawn cords may be subjected to a blueing treatment. It is preferable to increase the adhesiveness by performing an acid treatment after the treatment.

The above-described cord has significantly improved compression fatigue resistance as compared with the conventional steel cord, and can absorb the compression input by deformation of the steel cord itself. This significant improvement in compressive fatigue overcomes the disadvantages of steel cords, while other features such as the high flexural rigidity of steel cords make it possible to use so-called safety tires with excellent run-flat durability. Can also be applied.

Next, another steel cord according to the present invention comprises a single core filament made of sub-co-folded steel having a carbon content of less than 0.7%, and 3,3 disposed around the core filament. Consists of 4, 5 and 6 sheath filaments. Examples of the sub-co-folded steel having a carbon content of less than 0.7% include, but are not limited to, mild steel, low carbon bainite steel, low carbon ferrite / pearlite steel, low carbon low alloy high strength steel, and the like. Not something.

The filament diameter of the filament of the steel cord used in the present invention is preferably 0.125 to 0.27.
5 mm, more preferably 0.15 to 0.20 mm, and if the diameter is less than 0.125 mm, the wire is hardly drawn and the tensile strength is hardly produced at the time of production, so that the cord strength is reduced, and as a result, the case of the tire is reduced. The strength of the member decreases, while
If it exceeds 0.275 mm, the fatigue resistance deteriorates, which is not preferable.

In the present invention, the rubber component used for the carcass ply is not particularly limited, and examples thereof include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), and isoprene rubber (IR). Among them, natural rubber and butadiene rubber are preferable. In addition, compounding agents usually used in the rubber industry, for example, a reinforcing agent such as carbon black, a vulcanizing agent, a vulcanizing aid, a vulcanization accelerator, an antioxidant, a softening agent, and the like can be appropriately provided. Of course it is. By adjusting the type and amount of carbon black, the amount of sulfur, the amount of oil, and the like with respect to the rubber, the tensile stress at 50% elongation is preferably 0.5 to 3.0 MPa, more preferably 0.5 to 3.0 MPa. ~
A coated rubber having a pressure of 2.0 MPa is obtained. If the tensile stress of the rubber layer is lower than 0.5 MPa, the durability near the end of the belt and the end of the carcass ply is usually inferior in internal pressure running, and a failure such as separation between the belt and the carcass is caused. On the other hand, if it is higher than 3.0 MPa, it is not possible to improve the riding comfort during normal internal pressure running.

The pneumatic tire of the present invention has a carcass ply reinforced with a steel cord, and can be manufactured by a conventional method. By applying this carcass ply, a green tire is subjected to vulcanization molding to obtain a desired pneumatic tire.

FIG. 1 shows a cross section of a pneumatic tire 1 for a passenger car according to an embodiment of the present invention. In the example shown,
The carcass 2 is arranged in a direction substantially orthogonal to the equatorial plane.
Each ply is wound up around a bead ring 5 to form a winding end, and a bead filler 6 made of hard rubber is provided between the carcass 2 on the bead ring 5 and the ply winding end. Is buried tapered. Reference numeral 3 is a tread. Belt 4
Is formed by superposing two sheets (first belt layer 4a and second belt layer 4b) in which the cords are arranged obliquely with respect to the equatorial plane so that the cords cross each other.

In the present invention, by providing a rubber reinforcing layer having a crescent-shaped cross section on the inner surface and / or outer surface of the carcass layer using a steel cord, especially by arranging the rubber reinforcing layer on the inner surface, the run flat durability is further improved. An improved and more durable pneumatic safety tire can be obtained.

FIG. 2 shows a cross section of a pneumatic tire 1 for a passenger car according to an embodiment of the present invention. In the example shown,
The carcass 2 is arranged in a direction substantially perpendicular to the equatorial plane.
Each ply is wound up around a bead ring 5 to form a winding end, and a bead filler 6 made of hard rubber is provided between the carcass 2 on the bead ring 5 and the ply winding end. Is buried tapered. On the inner peripheral surface of the side portion of the carcass 2, a rubber reinforcing layer 7 having a crescent cross section is arranged over the entire side portion from a position overlapping with the bead filler 6 via the carcass 2. Reference numeral 3 is a tread. The belt 4 is formed by superposing two sheets (first belt layer 4a and second belt layer 4b) in which cords are arranged obliquely with respect to the equatorial plane so that the cords cross each other.

In the pneumatic tire of the present invention, at least one down carcass layer may be further provided between the sidewall portion and the outer surface of the carcass layer made of steel cord.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structures of pneumatic tires of an embodiment and a comparative example will be described below with reference to the drawings. Size 185/70 SR14 of the type shown in FIG. 1, rim size 5 1/2
Various prototypes of pneumatic tires for passenger cars were manufactured using J × 14 tires and employing the conditions shown in Tables 1 and 2 below as a carcass structure. The belt has a twisted structure of 1 × 3 × 0.30
(1 mm belt cords 30 cm / 5 cm), two (mm) steel cords arranged obliquely at an angle of 22 ° with respect to the equatorial plane. As shown.

The test tires were evaluated for steering stability and cord breakage in the carcass ply as follows.

Driving stability The test tire was placed on a drum having an outer diameter of 3000 mm, and after a load of 395 kg was applied to the tire, it was 30 km / h.
At a speed of 30 minutes, the load was removed, the internal pressure was readjusted to 1.7 kgf / cm ² , and the slip angle was again adjusted to ± 4 on the drum under the same speed and the same load. ° was continuously added in the positive and negative directions. Next, the cornering force (C
F) is measured, and the following equation is obtained: CP (kg / degree) = ｛CF (1 °) (kg) + CF (2
°) (kg) / 2 + CF (3 °) (kg) / 3 + CF
The cornering power (CP) was determined at (4 °) (kg) / 4 ° / 4. The evaluation results were expressed by an index when the CP of each test tire was set to 100 for the CP of the control tire (Comparative Example 1). The larger the index, the better the steering stability.

(Cord breakability in carcass ply)
The test tire was mounted on a passenger car and the tire pressure was 1.7 kgf.
/ Cm ^{2 on a} general road for 40,000 km, then reduce the internal pressure to 1.4 kgf / cm ² ,
I ran 10,000 km. Thereafter, the tire was dissected, and the presence or absence of a broken cord in the carcass ply at the position below the belt was examined. The results obtained are shown in Tables 1 and 2 below.

[0029]

[Table 1]

[0030]

[Table 2]

As can be seen from the above Tables 1 and 2, the pneumatic tire of the embodiment using the steel cord satisfying the conditions specified in the present invention for the carcass ply has a higher value than the pneumatic tire of the comparative example. Also has excellent handling stability and ply cord breakability.

[0032]

As described above, in the pneumatic tire of the present invention, by using a carcass ply using a specific steel cord, the exercise performance can be improved, and at the same time, the fatigue resistance of the carcass can be improved. Can be improved.

[Brief description of the drawings]

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

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

FIG. 3 is an explanatory diagram showing a strand diameter dc, an amplitude Lc, and a pitch Pc of a molded core filament.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Carcass 3 Tread 4 Belt 4a 1st belt layer 4b 2nd belt layer 5 Bead ring 6 Bead filler 7 Rubber reinforcement layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D07B 1/06 D07B 1/06 A

Claims (6)

[Claims] 1. A pair of left and right ring-shaped bead cores, and both ends of a carcass ply composed of a layer in which a plurality of cords arranged in parallel are embedded in a covering rubber, are folded back around the bead core to form an annular shape. A formed carcass portion, a belt portion including a plurality of layers of belt plies disposed radially outward of the carcass portion in the tire radial direction, an annular tread portion disposed radially outward of the belt portion in the tire radial direction, and the tread A buried cord of at least one carcass ply is made of a steel cord, and the steel cord is composed of one core filament; and Consisting of three, four, five or six sheath filaments arranged around a core filament, the core filament being helical or Typed in the waveform, typing ratio Rc represented by the ratio of the wire diameter dc amplitude Lc and the core filament typed spiral or waveform
(= Lc / dc) and the pitch Pc of the helical shape or waveform of the core filament are expressed by the following formulas: 0.20 ≦ Rc ≦ 4.8 2.0dc / 0.20 ≦ Pc ≦ 15.0dc / 0. A pneumatic tire satisfying the relationship represented by (15). 2. A pair of left and right ring-shaped bead cores, and both ends of a carcass ply composed of a layer in which a plurality of cords arranged in parallel are buried in a covering rubber, are folded back around the bead cores to form an annular shape. A formed carcass portion, a belt portion including a plurality of layers of belt plies disposed radially outward of the carcass portion in the tire radial direction, an annular tread portion disposed radially outward of the belt portion in the tire radial direction, and the tread A pneumatic tire comprising a pair of sidewall portions disposed on the left and right of the portion, wherein at least one embedment cord of the carcass ply has one core filament and 3 cores disposed around the core filament. A steel cord comprising 4, 5, or 6 sheath filaments, wherein at least the core filament has a carbon content of less than 0.7% A pneumatic tire characterized by comprising a hypo-fold steel. 3. The pneumatic tire according to claim 1, wherein the core filament is spirally formed, and a twist direction of the core filament is opposite to a twist direction of the sheath filament. 4. The pneumatic tire according to claim 1, wherein at least the core filament of the steel cord has a breaking elongation of 3.5% or more. 5. 50% of the coating rubber of the carcass ply
The pneumatic tire according to any one of claims 1 to 4, wherein a tensile stress during elongation is 0.5 to 3.0 MPa. 6. The pneumatic tire according to claim 1, wherein a rubber reinforcing layer having a crescent cross section is provided on one or both of an inner surface and an outer surface of the carcass portion.