JP2995210B2 - Radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pair of bead cores,
The present invention relates to a radial tire having a carcass layer made of cords that are locked to a bead core and arranged in the tire radial direction, and a belt layer arranged outside the carcass layer in the tire radial direction.

[0002]

2. Description of the Related Art In recent years, radial tires are known for their low fuel consumption performance, long life performance (durability performance), and steering stability performance.
Pneumatic tires have become the mainstream because they have significantly better performance than bias tires.

A radial tire has a carcass layer including a pair of annular bead cores, a carcass layer having both ends locked to the bead cores, arranged in the tire radial direction, and extending through both sidewall portions and a tread portion. It has a highly rigid belt layer arranged radially outward of the layer.

[0004] A belt of a conventional radial tire for a passenger car is formed by arranging a plurality of steel cords having a structure of 1 × 4, 1 × 5, 2 + 2, etc., which are formed by twisting a plurality of steel filaments, that is, a plurality of belt cords are arranged in parallel. Since these steel cords have high rigidity and high durability, the performance of the radial tire can be sufficiently brought out by using the steel cord.

However, the steel filaments constituting these steel cords are in close contact with each other,
Inflow of rubber between the steel filaments was hindered, which sometimes caused poor adhesion between the rubber and the belt cord.

In order to solve this problem, when the steel filaments are twisted, they are formed so as to form a space between the steel filaments, so that the rubber flows smoothly between the steel filaments. Belt cords, so-called open cords, have been proposed. However, such open cords have a problem that it is technically difficult to secure a space between steel filaments in terms of manufacturing. In addition, there is a demand for low fuel consumption and light weight, and it is necessary to reduce the weight of the belt layer.

On the other hand, by reducing the number of steel filaments and simplifying the structure of the belt cord, both the above-mentioned problem of rubber inflow between the steel filaments and the problem of production are solved, and the weight is reduced. A method of achieving this has been proposed. For example, Japanese Patent Application Laid-Open No. Sho 62-234921 discloses a radial tire using a belt cord of 1 × 2 structure formed by twisting two steel filaments for a belt.

[0008]

SUMMARY OF THE INVENTION However, the above 1)
In a radial tire in which a belt cord having a × 2 structure is applied to a belt, a phenomenon in which part or all of the steel filaments constituting the belt cord is cut due to friction between the steel filaments under severe use conditions such as repeated turning. (Hereinafter, referred to as BBU) tends to occur, particularly in tires having an aspect ratio of 70% or more, and this BBU reduces the tagging effect of the belt layer and causes tire burst. There was a problem.

An object of the present invention is to use a belt cord composed of a small number of steel filaments for a belt to solve both the problem of rubber inflow between the steel filaments and the problem of production, and to reduce the weight of tires. It is an object of the present invention to provide a radial tire capable of accelerating, improving fuel economy, and preventing the occurrence of BBU.

[0010]

A radial tire according to the present invention comprises a pair of annular bead cores and cords having both ends locked to the bead cores, penetrating both sidewall portions and tread portions, and being arranged in the tire radial direction. In a radial tire having a belt layer made of a ply in which a plurality of belt cords in which a plurality of belt cords each of which is provided with a carcass layer and a carcass layer are arranged in parallel in the tire radial direction of the carcass layer and twisted with steel filaments have a diameter of 0.25 mm, To 0.32
formed by twisting two or three steel filaments each having a length of 8 to 15 mm.
The number of fibers to be driven is set to 39/5 cm to 60/5 cm, the belt cords are crossed at least between two plies, and the value of the ratio SA / W between the belt camber area SA and the effective belt width W is set to 0 to 0.1. It solves both the problem of rubber inflow between steel filaments and the problem of production, achieves a reduction in the weight of radial tires, improves fuel economy, and prevents the occurrence of BBU. be able to.

[0011]

FIG. 1 is a cross-sectional view in the width direction of a radial tire to which the present invention is applied. A radial tire 1 has a pair of annular bead cores 2, both ends of which are folded around the bead core 2 and are locked. A bead core made of a one-ply (or a plurality of plies) carcass layer 3 made of cords arranged in the tire radial direction penetrating the wall part and the tread part, and a hard rubber having a tapered JISA hardness of 70 to 90; 2 ply (3 ply) in which a plurality of bead apex 4 disposed radially outward of the tire 2 and a plurality of belt cords disposed on the outer periphery of the carcass layer 3 in the tire radial direction and twisted with steel filaments are arranged in parallel. Belt layer 5 made of the above.

FIG. 2 is a cross-sectional view of the belt layer in the width direction. The belt layer 5 includes an inner ply 5I and an outer ply 5O, and a plurality of belt cords (steel cords) 6 are provided on each of the plies 5I and 5O. The belt profile BL is inclined at a relatively small angle of 10 to 30 degrees with respect to the circumferential direction, is arranged in parallel with each other, and has a center line between curves connecting the belt cords 6 in both plies 5I and 50. It is desirable that the inner ply 5I has a width capable of covering the tire contact width.

The belt cord of the inner ply 5I and the belt cord of the outer ply 5O are arranged so as to intersect each other.
The number of driving is measured in a direction perpendicular to the belt cord 6 to be 39 / 5cm to 60 / 5cm. If the number of driving is less than 39 / 5cm, the rigidity of the belt layer 5 is insufficient.
Tire performance is reduced, and if it exceeds 60/5 cm, the rigidity of the belt layer 5 becomes too high, which leads to deterioration of ride comfort and increase in tire weight.

Here, the area where both the plies 5I and 50 are present is an effective belt area EA, the axial width of the effective belt area EA is an effective belt width W, and the outermost end of the effective belt area EA in the tire axial direction. Is defined as the belt profile BL (see FIG. 1). The belt profile BL is represented as a curve equidistant from a line connecting the centers of the belt cords 60 of the respective belt plies (see FIG. 2).

FIG. 3 is a perspective view showing the structure of the belt cord. The belt cord 6 is formed by twisting two steel filaments 7, 7, and the diameter of the steel filament 7 is set to 0.25 mm to 0.32 mm. If the diameter of the steel filament 7 is less than 0.25 mm, the rigidity of the belt layer 5 is insufficient, and the required tire performance cannot be obtained.
If it exceeds 0.32 mm, the rigidity of the belt layer 5 becomes too high,
This will result in poor ride comfort and an increase in tire weight.

FIG. 4 is an explanatory diagram of a method of calculating the belt camber area SA. The tire is mounted on a standard rim, and the belt camber area SA is measured using a CT scanner or the like in a state where a normal internal pressure is charged. An intersection A between the belt profile BL and the tire equatorial plane CL and a point B on the belt profile BL which is 30% (0.3 W) of the effective belt width W in the tire axial direction from the point A are determined. Is a circular arc having a radius R whose center is located on the tire equatorial plane CL, and a plane EL parallel to the tire equatorial plane CL including a point C at the outermost end in the tire axial direction of the belt profile BL. And the virtual belt profile bL, which is an arc having a radius R extending outward from the point B in the tire axial direction at a radius R, is defined as D, and the belt profile BL
Let P be the point at which the virtual belt profile bL begins to separate from the virtual belt profile bL, and let the area of the triangle PCD be the belt camber area SA.

FIG. 5 is a cross-sectional view showing deformation when the tire is in contact with the ground. When the tire is in contact with the ground, the belt is deformed by a load to change the belt profile BL to BL-1. growing.

FIG. 6 is an explanatory view of a deformed state, in which the change amount v when the belt profile BL changes to BL-1 is calculated from the belt profile BL to the virtual belt profile bL.
Begin to increase sharply from the point P at which separation begins, and the occurrence of BBU is concentrated at the point P. This is because the change amount v on the inner side in the tire axial direction with respect to the point P is It is considered that this is because the friction of the steel filament at the point P is larger than that of the other parts due to the remarkably different amount of change v, and the occurrence of BBU is closely related to the belt camber area SA.

The results of the experiment are shown in Tables 1 and 2 below. The structure of the belt cord was 1 × 2, the diameter of the steel filament was 0.30 mm, and the number of belt cords to be driven was 49/5 cm. The BBU measurement conditions were as follows: each tire was mounted on a standard rim, filled with normal internal pressure, and then mounted on a domestic car with a displacement of 1600cc to 3000cc. On a test course, a circle with a radius of 7m and a speed of 25km / h was used. 8 circumscribed
The tire was disassembled after turning the course of the character 300 times (so-called 8-character turning test), and the BBU generation of the belt cord was measured by the total sum of the entire circumference of the tire.

Table 1 Example 1 Example 2 Example 3 Example 4 Tire size 185SR14 185 / 70R14 185 / 70R14 195 / 65R15 W [mm] 117 120 124 132 SA [mm ² ] 10.7 7.2 4. 90 SA / W [× 10 ^-2 mm] 9.1 6.0 4.0 0 BBU [cm] 33 24 00

Table 2 Example 5 Example 6 Comparative Example Tire Size 175 / 70R13 155SR12 195 / 70R14 W [mm] 116 95 135 SA [mm ² ] 8.9 7.1 19.0 SA / W [× 10 ^{− 2} mm] 7.7 7.5 14.1 BBU [cm] 140 0 117 In Tables 1 and 2, W: effective belt width, S
A: Belt camber area.

FIG. 7 is a graph showing the results of the above experiment.
If BBU exceeds 50 cm, BBU will be generated by actual use of the tire. If SA / W exceeds 10 × 10 ^-2 mm = 0.1 mm, it will fall into the BBU generation region, and the correlation curve will be BBU.
The occurrence of BBU can be suppressed by suppressing the SA / W outside the generation region of to a range of 0 to 0.1 mm.

[0023]

Since the present invention is configured as described above, the following effects can be obtained. 0.25 diameter belt cord
The steel cord is formed by twisting two or three steel filaments each having a diameter of 0.3 mm to 0.32 mm. The twist pitch of the belt cord is 8 mm to 15 mm. Crossing between plies facilitates the flow of rubber between the steel filaments, improves the adhesion between the rubber and the belt cord, improves durability, and fully demonstrates the performance of radial tires In addition, the weight of the radial tire can be reduced, and the fuel economy performance can be improved.
Further, by setting the value of the ratio SA / W between the belt camber area SA and the effective belt width W to 0 or more and less than 0.1, B
The occurrence of BU can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view in the width direction of a radial tire to which the present invention is applied.

FIG. 2 is a cross-sectional view in the width direction of the belt layer.

FIG. 3 is a perspective view illustrating a configuration of a belt cord.

FIG. 4 is an explanatory diagram of a method for calculating a belt camber area SA.

FIG. 5 is a cross-sectional view showing deformation when the tire is in contact with the ground.

FIG. 6 is an explanatory diagram of a tire deformed state.

FIG. 7 is a graph showing experimental results.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radial tire 2 Bead core 3 Carcass layer 4 Bead apex 5 Belt layer 6 Belt cord 7 Steel filament

Claims (1)

(57) [Claims] 1. A pair of bead cores, a carcass layer composed of cords whose both ends are locked to the bead core and arranged in the tire radial direction, and a plurality of steel filaments arranged on the outer periphery of the carcass layer in the tire radial direction and twisted together. In a radial tire having a belt layer composed of plies in which a plurality of belt cords are arranged in parallel, the belt cords are formed by twisting two or three steel filaments having a diameter of 0.25 mm to 0.32 mm, and the twist pitch of the belt cords 8mm to 15mm, number of shots 39 / 5cm to 60 /
A radial tire having a width of 5 cm, a belt cord intersecting at least between two plies, and a value of a ratio SA / W between a belt camber area SA and an effective belt width W of 0 to less than 0.1.