JPH06262911A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce rolling resistance to improve fuel consumption by determining the expansion elastic modulus of a bead core in a given range. CONSTITUTION:A strip S, a rubber-coated wire W, made by bundling the given number of parallel steel or organic fiber filaments and then coating them with resin, is winded given times and is laminated to form a bead core B. The expansion tensil elastic modulus Es of the bead core B is determined within a range of 3.5X10<4>(Kgf/100%)<=Es<=10.0X10<4> (Kgf/100%). Consequently, distortion due to the bending deformation of a bead filler and the increase of rolling resistance by the generation of heat due to hysteresis loss are reduced, and fitness to a rim is improved to improve ride feeling performance and maneuvering stability.

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 having low rolling resistance and improved fuel consumption.

[0002]

2. Description of the Related Art Conventionally, as a bead core forming a bead portion in a pneumatic tire, there is known a bead core formed of a non-twisted strand in which a steel wire is wound in a ring shape.

[0003]

The bead core forming the bead portion in a pneumatic tire has extremely high tensile rigidity and extremely high elongation in order to secure fitting with the rim and maintain internal air pressure. Non-twisted strands made by winding a small amount of steel wire in a ring shape are used.

However, the expansion tensile modulus E _B of the conventional bead core is, for example, E _B ≧ 15.0 × 10 ⁴ (kg
f / 100%), it is said that when the bead part is deformed by external pressure during running, strain is concentrated on the easily deformable bead filler, etc., heat is generated due to hysteresis loss in this part, and rolling resistance increases. There's a problem.

Further, since the tensile strength of the bead core is extremely high and hard, for example, when the air pressure of the tire is low or the applied load is increased, the bead portion is less deformed, so that the shoulder to the side of the tire. There is a problem that stress concentrates on the wall portion, a buckling phenomenon appears in this portion, and durability performance such as a carcass is deteriorated.

Furthermore, since the bead portion is hard and is not easily deformed, a considerable amount of force is required to attach the tire to the rim, which causes problems such as damage to the bead toe or the like, or time required to attach the tire.

An object of the present invention is to provide a pneumatic tire which can solve the problems of the conventional pneumatic tire as described above.

[0008]

According to the present invention, in order to achieve the above object, the expanded tensile elastic modulus E _B of the bead core is 3.5 × 10 ⁴ (kgf / 100%) ≦ E _B ≦ 10.0 × The range is 10 ⁴ (kgf / 100%).

The present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 shows a half of a radial cross section of a pneumatic tire, where 1 is a pneumatic tire (hereinafter, also simply referred to as “tire”), and the pneumatic tire 1 includes a bead portion 2 and a carcass 3. , Tread 4 and belt 5
6 is a side wall. Further, b is a bead filler made of hard rubber having a substantially triangular shape, and B is a bead core forming the bead portion 2.

FIG. 2 shows a predetermined number of wires w arranged in parallel.
FIG. 6 is an enlarged perspective view of a strip S in which is covered with a rubber g,
The wire w is made of a wire formed by bundling a predetermined number of steel or organic fiber filaments and coating with a suitable resin, or a steel wire. Not only the wire w, but also a cord formed by appropriately twisting a predetermined number of steel or organic fiber filaments may be juxtaposed and covered with the rubber g to form the strip S.

As shown in FIG. 3, which is an enlarged perspective view of the bead core B, the bead core B is formed by winding and laminating the strip S, which is obtained by coating the wire w with the rubber g, a predetermined number of times. The number of wires w or the number of windings of the strip S covered with the rubber g shown in FIGS. 2 and 3 is used for convenience of clearly explaining the present invention. It does not limit the present invention in any way. Alternatively, the bead core B can be formed by winding the wire w in a ring shape a predetermined number of times without forming the strip S by arranging the wires w in parallel and coating them with the rubber g.

In the pneumatic tire of the present invention, the expanded tensile elastic modulus E _B of the bead core B formed by winding the wire w or the cord a predetermined number of times is 3.5 × 10 ⁴ (kgf / 100%) ≦ E _B ≦ 10.0 × 10 ⁴ (kgf / 100%), the expanded tensile elastic modulus of the bead core B E _B
From the range described above, extended tensile modulus E _B of the bead core B is in the case of ^{_{E B> 10.0 × 10 4 (}} kgf / 100%) , the rotation of the bead portion is suppressed at the time of loading, Strain is concentrated on the bead filler b, which causes high heat generation or deterioration of fuel consumption, and the expanded tensile elastic modulus E _B is E _B <3.5 × 10.
^This is because in the case of ⁴ (kgf / 100%), the shear deformation between the back surface of the bead and the rim becomes large, resulting in high heat generation or deterioration of fuel efficiency. The expanded tensile modulus E of the bead core B
It is more preferable that _B is 5.0 × 10 ⁴ (kgf / 100%) ≦ E _B ≦ 6.0 × 10 ⁴ (kgf / 100%).

[0013] Thus, by limiting the extension tensile modulus E _B of the bead core B in the above range, it becomes possible to bead core B can move actively, thus, the deformable bead filler b etc. Strain is concentrated, heat generated by hysteresis loss is generated in this portion, and rolling resistance is greatly reduced.

Further, by providing the bead core B with an appropriate degree of elongation, it becomes easy to mount the tire on the rim and the fit between the tire and the rim becomes good. by this,
The rim slip property and rim dismounting property are greatly improved, and the steering stability performance during driving is also greatly improved.

FIG. 4 is a schematic plan view of a measuring device for the expanded tensile rigidity E, and 7 is a cylindrical body which is equally divided into eight expanded bodies 8, and each expanded body 8 is directed outward by an appropriate means. Is configured to extend to.

A bead core B is attached to the cylindrical body 7, a force F is evenly applied to each expansion body 8, and the tension T (kgf) and the elongation e (%) in the circumferential direction of the cylindrical body 7 are measured. A graph of tension T and elongation e (%) as shown in FIG. 5 is obtained. Then, the elongation e (200)% when the tension T = 200 kgf and the elongation e (400)% when the tension T = 400 kgf are obtained, and the expanded tensile rigidity E of the bead core B is calculated by the following formula.
(Kgf / 100%) is calculated. E = [400-200] / [e (400) -e (200)] × 100 Further, the rolling resistance index (RR index) used for evaluation of Examples or Comparative Examples is calculated as follows.

Internal pressure of 2.70 mm on a drum having an outer diameter of 1708 mm.
A test tire adjusted to 0 kg / cm ² was installed, and from the tire size (the tire size used in the examples and comparative examples of the present invention was 175 / 70R13) and the internal pressure, JIS was determined.
80 after applying the load specified in the standard D4202
After preliminarily running at 30 km / hr for 30 minutes, readjusting the air pressure and increasing the drum rotation speed to a speed of 200 km / hr, coast the drum to 185 km / hr to 2 km.
The tire rolling resistance RR was calculated from the moment of inertia until the drum rotation speed decreased to 0 km / hr.

RR = ds / dt (Id / Rd ² + It / Rt ² ) −resistance of drum alone, where Id is the moment of inertia of the drum, It is the moment of inertia of the tire, Rd is the drum radius, and Rt is the tire radius. is there.

The rolling resistance value at 50 km / hr obtained by the above equation was obtained as a representative value. The environment is 24 ± 2 °
It measured in the room controlled by C. The indexing was represented by rolling resistance index = (representative value of test tire / representative value of control tire) × 100, rounded to the nearest whole number. As a result, the smaller the rolling resistance index, the better the fuel consumption.

[0020]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded. The aramid wire described in the column of the constituent elements in Table 1 was made by wrapping 4,000 1.5d (denier) aramid fiber filaments without twisting and coating the periphery with a nylon resin to form a wire w having a diameter of 1.1 mm. And this aramid wire is shown in Table 1.
The bead core B is formed by arranging it in a predetermined structure as described in the column of the structure of the bead core. Also,
The aramid cords described in the columns of the constituent elements of Comparative Example 6 and Comparative Example 7 in Table 1 are obtained by bundling 2000 aramid fiber filaments f of 1.5d (denier).
A twisted cord is formed by twisting 20 times per cm to form a lower twisted cord.
A cord having a total length of 6000 d is twisted 20 times per cm, and the bead core B is formed by arranging the cord in a predetermined structure.

In Comparative Examples 1 to 4 and Example 1, a steel wire having a diameter of 0.94 mm is arranged in a predetermined structure to form a bead core B.

[0022]

[Table 1]

From Table 1, it can be seen that the RR index of the example of the present invention is smaller than that of the comparative example. The expanded tensile modulus E _{B of the} bead core B is the upper limit of the present invention 1
The RR indexes of the pneumatic tires of Comparative Examples 1 to 4 exceeding 0.0 × 10 ⁴ (kgf / 100%) are all over 100, and the lower limit of the present invention is 3.5 × 10 ^4. (Kgf / 10
The RR indexes of the pneumatic tires of Comparative Examples 5 to 7, which are less than 0%), also all exceed 100, which shows that rolling resistance is large and fuel consumption is poor as compared with the examples of the present invention. Further, the expanded tensile elastic modulus E _{B of} the bead core B is in a preferable range, that is, 5.0 × 10 ⁴ (kgf / 100%) ≦ E _B ≦ 6.0.
The RR index of the pneumatic tires of Examples 2 to 4 included in the range of × 10 ⁴ (kgf / 100%) is extremely smaller than the RR index of the pneumatic tires of Comparative Examples 1 to 7.

[0024]

[Table 2]

In Table 2, as a fiber filament, polyparaphenylene benzbisoxazole (POLY-P-PHENYLE) is used.
NBEZOBISOXAZOLE) (hereinafter referred to as "PBO") fibers are used. The PBO wire described in the component column of Table 2 is PBO of 1.5d (denier).
4000 filament filaments were bundled untwisted and covered with nylon resin to form a wire having a diameter of 1.2 mm, and this PBO wire was as described in the column of bead core structure in Table 2. The bead core B is formed by arranging it in a predetermined structure.

The PBO cords described in the column of constituent elements in Table 2 are obtained by bundling 2000 pieces of 1.5d PBO fiber filaments and twisting 20 times per 10 cm to form a lower twist cord. A bundle of two twisted twisted cords is twisted 20 times per 10 cm in the opposite direction to the twisted twist to form a cord having a total length of 6000 d. The bead core B is formed by arranging this cord in a predetermined structure. .

From Table 2, PBO as a fiber filament
It can be seen that the RR index is also smaller in the case of using the above.

[0028]

Since the present invention is constructed as described above, it has the following effects. The positive movement of the bead core reduces the strain due to the bending deformation of the bead filler, and the heat generated by the hysteresis loss is generated at this portion, which significantly reduces the increase in rolling resistance.

Further, by imparting an appropriate elongation to the bead core, the durability against rim sliding is improved, the tire is easily attached to the rim, and damage such as chipping of the bead toe is reduced. .

Further, since the fitting property of the tire to the rim is improved, the uniformity of the tire is improved, and the riding comfort performance and the steering stability performance are improved.

[Brief description of drawings]

FIG. 1 is a radial cross-sectional view of a pneumatic tire.

FIG. 2 is an enlarged perspective view of a strip of wire covered with rubber.

FIG. 3 is an enlarged perspective view of a bead core.

FIG. 4 is a plan view of a cylindrical body used in the expanded tensile stiffness measuring method.

FIG. 5 is a relationship graph of tension and elongation of a bead core.

[Explanation of symbols]

 1-Pneumatic tire 2-Bead B-Bead core S-Strip b-Bead filler w-Wire

Claims (1)

[Claims] 1. The expanded tensile elastic modulus E _B of the bead core is set in a range of 3.5 × 10 ⁴ (kgf / 100%) ≤ E _B ≤ 10.0 × 10 ⁴ (kgf / 100%). Pneumatic tires.