JPH0976706A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stable controllability and durability by expressing the coefficient of primary twist and the coefficient of final twist in formulas, and arranging a carcass ply cord so as to be at a fixed angle against the equatorial direction of a tire. SOLUTION: The coefficient of primary twist N1 and the coefficient of final twist N2 satisfy N1 =n1 ×(0.139×D1 /f)<1/2> ×10<-3> , N2 =n2 ×(0.139×D2 /f)<1/2> ×10<-3> , and 1.45<=N2 /N1 <=4.25. In the formulas, n1 expresses the primary-twist-number/10 cm, n2 expresses the final-twist-number/10cm, D1 expresses the nominal denier of primary twist yarn, D2 expresses the total nominal denier of cord, and f expresses the specific gravity of fiber g/cm<3> . A carcass ply cord 16 is arranged so as to be at angle 75 deg.-90 deg. against the equatorial direction of a tire 10. When the ratio N2 /N1 of the coefficient of final twist N2 and the coefficient of primary twist N1 exceeds 4.25, tensile rigidity of the cord is improved but fatigue resistance is lowered, and when it is under 1.45, the cord tensile rigidity is not improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire preferably used for passenger cars, and more particularly to a pneumatic tire excellent in steering stability and fatigue resistance.

[0002]

2. Description of the Related Art A pneumatic tire usually has a tread portion made of a rubber composition which comes into contact with a road surface, a carcass which is a reinforcing member for keeping an internal pressure of the tire, and an end portion of the carcass wound around and fixed to the tire. It consists of a bead core that defines the inner dimensions. Conventionally, as a carcass of a pneumatic tire, a tire cord as a reinforcing material coated with rubber has been generally used. In the case of a carcass using tire cords, filament yarns, which are fiber materials used for the cord material, are twisted together to form a lower twisted yarn, and a plurality of lower twisted yarns are further twisted to form a cord. At this time, a balanced twist in which the number of lower twists and the number of upper twists are equal is common.

In order to improve the steering stability of the tire,
It is necessary to increase the rigidity of the cord, but in general-purpose balanced twisting, if the number of twists is reduced, the rigidity of the cord increases, but the fatigue resistance of the cord deteriorates, resulting in a decrease in tire durability. There was a problem of doing.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to use a ply cord having a high rigidity and an excellent fatigue resistance, so that a pneumatic tire having a good steering stability and an excellent durability can be obtained. To provide.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventor has found that the above problems can be solved by using a twin-twisted yarn satisfying a specific twist condition as a carcass ply cord. completed.

That is, in the pneumatic tire of the present invention, as a carcass ply cord, a base twist is applied to a fiber raw yarn to obtain a lower twisted yarn, and a plurality of the twisted yarns are aligned and the upper twist in the opposite direction to the lower twisted yarn is applied. A pneumatic tire using a double twisted yarn, comprising a lower twist coefficient N ₁ and an upper twist coefficient N ₂ defined below.
And satisfy the following (Equation 2),

[0007]

[Equation 2]

(In the formula, n ₁ is the number of lower twists (times / 10 cm)
, N ₂ represents the number of twists (times / 10 cm), and D ₁
Represents the denier of the twisted yarn, D ₂ represents the total denier of the cord, and ρ represents the specific gravity of the fiber (g / c).
m ³ ). ) Further, the carcass ply cord is arranged so as to form an angle of 75 ° to 90 ° with respect to the equatorial direction of the tire.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

As shown in FIG. 1, a pneumatic tire 10 includes a tread portion 12 which comes into contact with a road surface, a carcass 14 which is a reinforcing member for maintaining an internal pressure of the tire, and a carcass top portion 1.
4A and a tread 12, which is a reinforcing member, is composed of a ply cord 16 and a bead core 18 for winding and fixing an end of a carcass and for defining an inner size of a tire.

As described above, as a carcass for a pneumatic tire, a tire cord covered with a rubber material layer is generally used. The tire cord is composed of a twin-twisted yarn obtained by twisting a plurality of lower twisted yarns in which fiber materials are twisted together, and the obtained tire cord is, for the purpose of improving the adhesiveness with a rubber material, if desired, an adhesive activator and Treated with adhesive.

The fiber raw yarn used in the carcass ply cord of the pneumatic tire of the present invention is not particularly limited, but polyester fiber such as polyethylene terephthalate used in the carcass ply cord, nylon 6
6, polyamide fiber such as nylon 46 and Kevlar fiber,
Rayon fiber or the like can be used. Among them, polyester fiber, especially polyethylene terephthalate is preferable from the viewpoint of tire performance balance and cost.

The thickness of the fiber used for the raw yarn is not particularly limited, and the thickness of the undertwisted yarn (D
_{Also 1} ) is not particularly limited as long as it satisfies the above conditions, but from the viewpoint of strength and durability, a ply-twisted yarn having a thickness of about 500 to 2000 denier is preferably used.

The number of twists (n ₁ ) of the lower twisted yarn is 10 to 10.
50 times / 10 cm is preferable, 10-40 times / 10
cm is more preferable.

A plurality of ply-twisted yarns thus obtained are twisted together to form a cord. The number of ply-twisted yarns is two.
The number of twists (n ₂ ) is about 20 to 60 times /
It is preferably about 10 cm, more preferably about 20 to 50 times / 10 cm.

The cord thickness of the cord formed of such twin yarn, that is, the total display denier (D ₂ ) is 1.
It is preferably about 500 to 4000 denier.

Here, the specific gravity of the fibers used is ρ,
Lower twisting factor N defined as follows ₁And the twisting factor N
₂And must be represented by the following (Equation 3).

[0018]

(Equation 3)

When N ₂ / N ₁ exceeds 4.25, the tensile strength of the cord is improved, but the fatigue resistance may be reduced. On the other hand, when N ₂ / N ₁ is less than 1.45, the cord tensile rigidity is not improved. The specific gravity ρ of the fiber used is a constant, and the thickness D _{1 of the} ply-twisted yarn increases as the ply-twist number n ₁ increases. Further, the total cord thickness D ₂ fluctuates due to both the number of upper twists n ₂ and the number of lower twists n ₁ , and basically, the number of upper twists n ₂ and the number of lower twists n ₁ are large. Then, the total cord thickness D ₂ increases. Therefore, in order to adjust N ₂ / N ₁ within the above range, it is necessary to adjust the relationship between the number of lower twists n ₁ and the number of upper twists n ₂ into a suitable range in consideration of strength. Such adjustment is easy for those skilled in the art.

The code thus obtained is 1000
Approximately about 1500 pieces are aligned and coated with a rubber material to form a sheet, and two or three sheets are laminated to form a carcass ply. At this time, the cord is subjected to a dipping process such as that applied to a conventional tire cord, for example,
Resorcinol-formaldehyde-latex adhesive (hereinafter referred to as RFL adhesive) treatment or the like can be applied. Further, the RFL adhesive treatment may be performed after the adhesive activity pretreatment with an epoxy compound such as a water-soluble aliphatic polyglycidyl ether or an isocyanate. RF
For the L adhesive treatment, the adjusted RFL was used in the same manner as the known method.
A method of immersing the film in an aqueous solution, removing excess aqueous solution with reduced pressure or a beater bar, and then heating and drying, and a method of applying the adjusted RFL aqueous solution with a spray, a roller or the like can be adopted. The latex component of the RFL adhesive depends on the type of rubber material used.
A suitable one can be selected. In addition, as a method of improving the adhesiveness between the film-shaped material and the rubber material,
Other than this, any material can be used as long as it can be generally used for bonding an unvulcanized rubber and a synthetic resin film, and the processing method is a material to be used, for example, a material forming the film, a rubber material, or an adhesive. It can be selected to be optimal for the agent, the adhesion aid and the like.

Next, a method of manufacturing a carcass for a radial tire will be described as an example. The cord obtained as described above is subjected to the dipping process as described above, if desired, and then a rubber material sheet having an arbitrary thickness is pressure-coated on both surfaces. A rubber material sheet sandwiching this cord is used as a carcass material. The width of the rubber material sheet is preferably manufactured so as to be the same as the width of the desired carcass.

The obtained carcass was formed into a cylindrical shape on a molding machine to form a carcass ply layer, and both ends were 1-2 m.
m overlay. A bead core is brought into contact with both openings of the cylindrical carcass ply layer, and then the bead core is expanded to have a toroidal shape while narrowing the interval between the bead cores.

At this time, when the carcass ply cord constructed under the above conditions is applied to the tire, the carcass ply may be arranged so that the cord forms an angle of 75 ° to 90 ° with respect to the equatorial direction of the tire. preferable.

When the carcass ply cord is applied to a tire, if the carcass ply cord is arranged at a certain angle with respect to the equatorial direction of the tire, the circumferential rigidity of the tire is improved. In particular, the cord of the present invention which meets the above conditions. With the use of, since the cord tensile rigidity is high, this effect is remarkably improved. If this angle is less than 75 °, the durability of the tire is significantly reduced, which is not preferable.

Before or after forming the cylindrical carcass ply layer into a toroidal shape, a steel belt, a tread rubber and a side rubber are laminated on the carcass ply layer to form a green tire (green tire), which is vulcanized and molded in a mold. To create a tire. The vulcanized tire can also be subjected to post-inflation treatment in which compressed air is enclosed to cool the tire while preventing it from shrinking.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples.

Pneumatic tires were produced as described below, and the obtained tires were evaluated according to the following methods. (Evaluation of Fatigue Resistance) The tire fatigue resistance was evaluated by the cord strength retention rate index after running on the drum.

The test tire was adjusted to an internal pressure of 3.0 kg / cm ² in a room at 25 ° C. ± 2 ° C., left for 24 hours to readjust the air pressure, and a load twice the JIS load was applied to the tire. It was run on a drum having a diameter of 3 m at a speed of 60 km / hr for 20,000 km. Thereafter, the cord was taken out from the tire, the fiber cord strength was measured according to JIS L1017, and the retention rate was expressed as% with the strength of the cord before the initial running as 100%, and the comparative example 10 which is a control.
An index of 0 was given from the cord strength retention rate of each tire.

The larger the value, the better the fatigue resistance. (Evaluation of steering stability) A test tire adjusted to an internal pressure of 2.0 kg / cm ² was installed on a drum having an outer diameter of 3000 mm,
After applying a constant load defined in JIS D 4202 from the internal pressure of the tire size, preliminary running is performed for 30 minutes at a speed of 30 km / hr. After that, the internal pressure was readjusted to 2.0 kg / cm ² in the non-added state, the load for preliminary running was applied again, and the slip angle was continuously applied up to 14 ° on the drum at the same speed. The cornering force (CF) at each positive and negative angle was measured, and the cornering power (CP value) was calculated by the following formula (Equation 4).

[0030]

(Equation 4)

The CP value of each test tire was determined, and the result of the control tire of Comparative Example 1 was set as 100, and the index value was displayed.

The larger the value, the better the steering stability. Example 1 Polyethylene terephthalate fiber was twisted 30 times / 10 cm to form a 1500 denier polyester lower twist bundle, and these two strands were twisted together to form a cord. The number of times of twisting was 40 times / 10 cm.
The cord obtained was 1500 denier. The specific gravity of the polyethylene terephthalate fiber used is 1.38.
Since it was (g / cm ³ ), N ₂ / N ₁ was calculated to be 1.89. This cord was dipped in an RFL adhesive and heat treated with hot air at 240 ° C. for 2 minutes to obtain a treated cord. 1000 cords were unwound onto a creel stand, and the rubber sheets were covered with a rubber sheet from both sides of the cord after the hammering was uniformly aligned with a toe having a prescribed groove for hammering. The number of cords driven was 50 lines / 5 cm. Then, the tire was cut into a length required for the size of the tire, and a topping sheet having a constant length was produced. Two sheets of this sheet were laminated in a tubular shape to produce a ply cord. At this time, the carcass ply cord is
The tire was arranged so as to form an angle of 86 ° with the equatorial direction.

Using this cylindrical topping cord, side rubber, beads, tread rubber and other necessary members were bonded and molded and then vulcanized according to a usual processing method to prepare an evaluation tire (test tire). .

Table 1 shows the results of evaluation of the test tires obtained according to the above method. (Example 2) The number of twists of polyester fiber is 20 times / 1
A tire was prepared in the same manner as in Example 1 except that the tire was set to 0 cm. The N ₂ / N ₁ of the code was calculated to be 2.83. This tire was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 A tire was prepared in the same manner as in Example 1 except that the number of twists of the polyester fiber was 40 times / 10 cm. Code was 1.41 was calculated for N ₂ / N ₁ of the. This tire was evaluated as in Example 1 and used as a control.

(Comparative Example 2) A tire was prepared in the same manner as in Example 1 except that the number of twists of polyester fiber was 10 times / 10 cm. The N ₂ / N ₁ of the code was calculated to be 5.66. This tire was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 3) The carcass ply cord is
Arranged to make an angle of 90 ° with the equator direction of the ear
A tire was prepared in the same manner as in Example 1 except for the above. Profit
N of the assigned code ₂/ N₁Is 1.89 as in the first embodiment.
there were. This tire was evaluated in the same manner as in Example 1. result
Are shown in Table 1.

Comparative Example 3 The carcass ply cord is
Arranged to make an angle of 70 ° with the equatorial direction of the ear
A tire was prepared in the same manner as in Example 1 except for the above. Profit
N of the assigned code ₂/ N₁Is 1.89 as in the first embodiment.
there were. This tire was evaluated in the same manner as in Example 1. result
Are shown in Table 1.

(Example 4) The number of lower twists of polyester fiber was 15 times / 10 cm, and the number of upper twists was 30 times / 10 cm so that the carcass ply cord formed an angle of 87 ° with the equatorial direction of the tire. A tire was prepared in the same manner as in Example 1 except that the tires were arranged. N ₂ / N ₁ code was 2.83. This tire was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0040]

[Table 1]

As is clear from Table 1, all of the pneumatic tires of the present invention show an improvement in steering stability while maintaining fatigue resistance, but in all Comparative Examples, the cord strength after running on the drum is high. It was found that the holding property was lowered, and the fatigue resistance and durability were poor.

[0042]

INDUSTRIAL APPLICABILITY The pneumatic tire of the present invention exhibits excellent steering stability and durability by using a ply cord having high rigidity and fatigue resistance.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view taken along the axis of a pneumatic tire of Example 1.

[Explanation of symbols]

 10 Pneumatic tire 14 Carcass 16 Ply cord

Claims (1)

[Claims] 1. A pneumatic tire using, as a carcass ply cord, a twisted yarn obtained by subjecting a raw fiber yarn to a twisted yarn to obtain a twisted yarn. The lower twist coefficient N ₁ and the upper twist coefficient N ₂ defined below are represented by the following (Equation 1), and (In the formula, n ₁ represents the number of lower twists (times / 10 cm), and n ₂
Represents the number of upper twists (times / 10 cm), D ₁ represents the indicated denier of the lower twisted yarn, D ₂ represents the total indicated denier of the cord, and ρ represents the specific gravity of the fiber (g / cm ³ ). ) Further, the carcass ply cord is arranged so as to form an angle of 75 ° to 90 ° with respect to the equatorial direction of the tire.