JP3165549B2 - Steel Belted Radial Tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel belted radial tire capable of improving the buckling resistance of a belt layer.

[0002]

2. Description of the Related Art A steel belted radial tire having a radially arranged carcass and a belt layer using a steel cord disposed radially outside the carcass includes:
During running, a phenomenon in which the belt layer at the ground contact portion undulates in the tire circumferential direction, so-called buckling, often occurs.

[0003] The buckling may cause separation between the steel cord forming the belt layer and the topping rubber covering the steel cord, and is considered to be one of the causes of lowering the durability of the belt layer. ing.

Accordingly, the following proposals have conventionally been made as means for suppressing buckling in order to improve the durability of the belt layer.

The width of the belt between the outer edges of the belt layer in the tire axial direction is reduced. The thickness of the tread rubber is reduced, and the radial compressive force acting on the belt layer at the ground contact portion is increased. The diameter of the steel cord, which is a belt cord, is increased to increase the bending stiffness of the belt layer.

[0006]

However, when the belt width is reduced, the cornering power is particularly reduced, which may cause a decrease in steering stability.

When the thickness of the tread rubber is reduced, the vibration absorption of the tread portion is impaired, and the riding comfort is reduced.

Further, a steel cord having a large wire diameter can secure steering stability, but lacks the ability to wrap the projections because the belt layer having high bending rigidity is provided around the steel cord, thereby reducing ride comfort. There is a problem.

On the other hand, it is known that the buckling frequently occurs at the center of the crown centered on the tire equator and hardly occurs at both shoulders in the tire meridian section of the belt layer.

It is considered that the buckling is caused by the fact that the peripheral length of the central portion of the crown of the belt layer is larger than the peripheral length of both shoulder portions.

Therefore, it can be seen that the buckling resistance can be improved by reducing the difference in circumference between the central portion of the crown of the belt layer and both shoulder portions.

According to the present invention, the tread central thickness A of the tread portion is set to be larger than a belt outer edge thickness H, a tread 1/3 thickness BA, and a tread 2/3 thickness BB within a predetermined range. Basically, it is an object of the present invention to provide a steel belted radial tire capable of improving buckling resistance and solving the above-mentioned problems.

[0013]

SUMMARY OF THE INVENTION The present invention is directed to a carcass ply using a radially arranged organic fiber cord that is folded from a tread portion to a bead portion of a bead portion through a sidewall portion from the inside to the outside in the tire axial direction. And a steel belted radial tire comprising a belt layer using a steel cord disposed inside the tread portion and radially outside the carcass,
The belt layer is composed of two belt plies having a narrow width belt ply on the outside in such a manner that the belt ply overlaps inside and outside in the radial direction, and the outer belt ply width WB1 between the outer edges of the outer belt ply in the tire axial direction is the tread. 75-8 of width WT
5%, inner belt ply width WB2 of inner belt ply
Is 85 to 90% of the tread width WT, and the tread center thickness A, which is the shortest distance between the outer surface of the outer belt ply on the tire equator and the tread surface, is from the tire inner surface on the tire equator to the outer side. 1. Equatorial point carcass belt total thickness CT, which is the shortest distance to the outer surface of the belt ply.
A belt outer edge thickness that is 95 times or more and 2.20 times or less, and is a shortest distance between an intersection point E at which a radial line passing through the outer edge of the outer belt ply intersects a tread surface and the outer surface of the outer belt ply; H, an intersection B at which the radius of the tire in the axial direction from the tire equator to the radial line is divided into three equal parts and the radial line separated outward in the tire axial direction from the tire equator intersects the tread surface and the outer belt The tread 1/3 thickness BA, which is the shortest distance between the outer surface of the ply, and twice the length of the tread, the intersection D where the radial line separated from the tire equator outward in the tire axial direction intersects the tread surface and the outer side. The tread 2/3 thickness B, which is the shortest distance between the belt ply and the outer surface.
B, and the tread center thickness A is A-1.0 mm ≦
BA = BB ≦ A−0.5 mm, A−2.0 mm ≦ H ≦ A−
The relationship is 1.0 mm.

[0014]

The steel-belted radial tire has a radially arranged carcass, a belt layer disposed radially outside and two belt plies using a steel cord overlapped and adhered to each other, and has a tread central thickness. A
Is set to 1.95 times or more and 2.20 times or less of the total thickness CT of the equatorial point carcass belt, and the belt outer edge thickness H,
Tread 1/3 thickness BA and tread 2/3 thickness B
B is defined as A-1.0 mm <BA = BB ≦ A-0.5 mm, A-
2.0 mm ≦ H ≦ A−1.0 mm.

As described above, the tread rubber of the tread portion is
It is set thicker at the tire equator and is regulated to be smaller than the tread center thickness A at the outer edge of the belt, so that the curvature radius of the belt layer can be increased by not changing the radius of curvature of the tread surface and the tire size from the conventional one. The circumferential difference between the central portion of the crown and both shoulder portions can be reduced.

Therefore, the buckling resistance can be improved without increasing the wire diameter of the steel cord of the belt layer or reducing the belt width, and the durability of the belt layer can be improved without impairing steering stability and riding comfort. Can enhance the character.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings by taking a steel belted radial tire having a tire size of 235 / 95R15 and an aspect ratio of about 95% as an example.

In the present invention, the steel-belted radial tire 1 is turned around a bead core 5 from a tread portion 2 to a bead portion 4 through a sidewall portion 3 to a bead portion 4 from the inside to the outside in the tire axial direction. Pair of folded portions 6b, 6 formed by
b) and a belt layer 7 disposed inside the tread portion 2 and radially outside of the carcass 6.

The tread surface 2A of the tread portion 2
Is formed by a tread rubber 9 disposed radially outward of the belt layer 7, the outer wall surface of the sidewall portion 3 is disposed outward of the carcass 6 in the tire axial direction, and the outer end is formed of an adhesive layer 10. It is formed by a sidewall rubber 11 which is joined to the tread rubber 9 through the rubber. The profile of the tread surface 2A in the tire meridian section substantially coincides with a single arc having a center at the tire equator C and a radius of curvature R of 1.0 to 1.2 times the tire maximum width W. I do.

The adhesive layer 10 is made of a rubber material having a hardness intermediate between the hardness of the tread rubber 9 and the hardness of the sidewall rubber 11, and the outer edge of the belt layer 7 in the tire axial direction inside the tire axial direction. Is covered.

At the radially inner end of the sidewall rubber 11, the upper end of a bead rubber 12 which is arranged outside the carcass 6 in the tire axial direction and forms the outer wall surface of the bead portion 4 is fixed, and the bottom portion of the bead portion 4 is fixed. A reinforcing layer 13 using an organic fiber cord for preventing damage to the bead portion 4 due to fitting with the rim is provided from the tire to the inner surface in the tire axial direction.

A bead apex 14 having a substantially triangular cross section rising from the bead core 5 is disposed between the main body 6a and the folded portion 6b of the carcass 6, and a bead apex 14 is formed between the bead core 5 and the carcass 6. The filler 1 using an organic fiber cord for preventing lateral displacement of the carcass 6
5 intervenes.

The carcass 6 has at least one carcass cord covered with a case topping rubber, which is a radial or semi-radial carcass cord inclined at an angle of 75 to 90 ° with respect to the tire equator C. The carcass plies 6A and 6B are overlapped and adhered to each other, and an organic fiber cord such as nylon, rayon, polyester, or aromatic polyamide can be used as the carcass cord.

The folded portion 6b of the carcass ply 6A
1 is the maximum width point 1 that forms the tire maximum width W.
6, the folded portion 6b2 of the carcass ply 6B overlaps and adheres to the inside of the folded portion 6b1 in the tire axial direction, and its radially outer end is the maximum It is located slightly inside, for example, about 5 mm inside the width point 16.

The belt layer 7 is composed of two belt plies 7a and 7b each of which is covered with a topping rubber on a steel cord arranged at an angle of 15 to 85 ° with respect to the tire equator C.
The outer belt ply 7b is formed to be narrower than the inner belt ply 7a,
In addition, the outer belt ply width WB1 between the outer edges of the outer belt ply 7b in the tire axial direction is set to be 75 to 8 of the tread width WT.
5%, and the inner belt ply width WB2 of the inner belt ply 7a is set to 85 to 90% of the tread width WT.

Here, the tread width WT is defined by an imaginary line r1 that smoothly extends the tread surface 2A from the outer edge of the tread surface 2A in the tire axial direction and the buttress surface 2B from the radial outer end of the buttress surface 2B of the tire. It is defined as the distance in the tire axial direction between the intersections F, F with the smoothly extended virtual line r2.

The inner belt ply 7a is in close contact with the outer surface of the carcass 6, and is gradually separated from the carcass 6 at the outer edge in the tire axial direction.

In the present invention, the thickness of the tread portion 2 is regulated. That is, the tread center thickness A, which is the shortest distance between the outer surface of the outer belt ply 7b on the tire equator C and the tread surface 2A, is determined from the tire inner surface on the tire equator C to the outer surface of the outer belt ply 7b. 1.95 times or more and 2.20 times or less the total thickness CT of the equatorial point carcass belt which is the shortest distance. The actual side value of the tread center thickness A in this example is 12.0 mm or more and 1
3.5 mm or less, and the total thickness CT of the equatorial point carcass belt is 6.2 mm.

When the tread center thickness A is less than 0.95 times the total thickness CT of the equatorial point carcass belt, the ride comfort is reduced, while when it is more than 2.20 times, separation is induced in the belt layer 7. It is easy to reduce durability.

Further, an intersection E at which a radial line L1 passing through the outer edge of the outer belt ply 7b intersects the tread surface 2A.
The belt outer edge thickness H, which is the shortest distance between the outer surface of the outer belt ply 7b, and the length m obtained by dividing the distance in the tire axial direction from the tire equator C to the radius line L1 by three, is the tire equator C The tread 1/3 thickness BA, which is the shortest distance between the intersection B where the radial line L2 separated from the outer side in the tire axial direction intersects the tread surface 2A and the outer surface of the outer belt ply 7b, A radial line L3 that separates the double length 2m from the tire equator C outward in the tire axial direction is a tread surface 2.
The tread 2/3 thickness BB, which is the shortest distance between the intersection D intersecting A and the outer surface of the outer belt ply 7b, and the tread center thickness A satisfy the following formula.

A-1.0 mm≤BA = BB≤A-0.5 mm A-2.0 mm≤H≤A-1.0 mm

In this example, the tread 1/3 thickness BA and the tread 2/3 thickness BB are 10.5 mm or more and 13.0 mm or less, and the belt outer edge thickness H is 1
It is 0.0 mm or more and 12.5 mm or less.

By regulating the thicknesses A, H, BA, and BB in this manner, the belt layer 7 of the steel belted radial tire 1 having the tread surface 2A approximated by an arc having the curvature radius R is formed. The circumferential length difference between the central portion of the crown on both sides of the tire equator C and the shoulder portion outward in the tire axial direction can be reduced, the buckling resistance can be improved, and the durability of the belt layer 7 can be increased.

Further, since the ply width of the inner and outer belt plies in the tire axial direction, the wire diameter of the steel cord, and the like are not changed from those of the conventional belt ply, steering stability and ride comfort can be prevented from deteriorating.

If the tread 1/3 thickness BA and the tread 2/3 thickness BB are smaller than the value obtained by subtracting 1 mm from the tread center thickness A, the ride comfort is reduced, while the tread center thickness A is 0.5 mm from the tread center thickness A. If the value is larger than the reduced value, the buckling resistance cannot be improved.

When the belt outer peripheral thickness H is smaller than the value obtained by subtracting 2.0 mm from the tread center thickness A, the riding comfort is lowered. On the other hand, when the belt outer peripheral thickness H is made larger than the value obtained by reducing the tread center thickness A by 1.0 mm. The buckling resistance cannot be improved.

[0037]

[Specific Examples] Tires (Examples 1 to 4) having a tire size of 235 / 95R15 and having the structure shown in FIG. 1 were prototyped according to the specifications shown in Table 1, and their performance was tested. In addition, a tire other than the configuration of the present application (Comparative Example 1)
Tests were also performed for the items 6 to 6) to compare the performance.

[0038]

[Table 1]

The test method is as follows. 1) Durability (buckling resistance) Apply the internal pressure specified in JIS to the test tire, and apply 1.5 times the internal pressure specified in JIS and the maximum load to the test tire using an indoor durability tester. And 65km / h
And the determination was made with the total running distance until the separation occurred in the belt layer.
It was indicated by an index of 00. The higher the numerical value, the better, and 100 or more is a pass level.

2) Driving Stability Judgment was made based on the driver's feeling during actual vehicle running, and the results were indicated by an index with Comparative Example 2 being 100. The higher the numerical value, the better, and 100 or more is a pass level.

3) Ride comfort The test tire was mounted on a fixed shaft of a commercially available bump-over vibration tester, and the load was 1.510 kg, the internal pressure was 7 kg / cm ² , and the speed was 6
The axial load fluctuation at the time of the overhang of the protrusion was measured under the condition of 0 to 100 km / H, and indicated by an index with Comparative Example 4 being 100. The higher the numerical value, the better, and 100 or more is a pass level. Table 1 shows the test results.

As a result of the test, it was confirmed that the belt of the embodiment improved the durability of the belt layer without impairing the steering stability and riding comfort.

[0043]

As described above, in the steel belted radial tire of the present invention, the tread center thickness A is set to 1 /
By making the thickness larger than the thickness BA, the tread 2/3 thickness BB, and the belt outer edge thickness H, the circumferential length difference of the belt layer in the tire axial direction is reduced, so that the buckling resistance can be improved and the durability can be improved. Can be increased.

[Brief description of the drawings]

FIG. 1 is a tire meridian sectional view showing one embodiment of the present invention.

[Explanation of symbols]

 2 Tread portion 2A Tread surface 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 7a Inner belt ply 7b Outer belt ply A Tread center thickness B, D, E Intersection BA Tread 1/3 thickness BB Tread 2/3 thickness C tire equator CT equatorial point carcass belt total thickness H belt outer edge thickness L1, L2, L3 radius line m length WB1 outer belt ply width WB2 inner belt ply width WT tread width

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11/00 B60C 9/20

Claims (1)

(57) [Claims] 1. A carcass comprising a carcass ply using an organic fiber cord in a radial arrangement, wherein the carcass is formed by turning a bead core of a bead portion from an inner side to an outer side in a tire axial direction from a tread portion through a sidewall portion and a radially arranged organic fiber cord. A steel belted radial tire having a belt layer using a steel cord disposed inside and radially outside of the carcass, wherein the belt layer overlaps inward and outward in the radial direction and closely adheres to the narrow belt ply outside. 2
The outer belt ply width WB1 between the outer edge of the outer belt ply in the tire axial direction is 75 to 85% of the tread width WT, and the inner belt ply width WB2 of the inner belt ply is the tread width WT. 85-90
%, And the tread center thickness A, which is the shortest distance between the outer surface of the outer belt ply on the tire equator and the tread surface, is the shortest distance from the tire inner surface on the tire equator to the outer surface of the outer belt ply. Equatorial point carcass
Between 1.95 times and 2.20 times the total belt thickness CT and between an intersection E where a radius line passing through the outer edge of the outer belt ply intersects the tread surface and the outer surface of the outer belt ply. The belt outer edge thickness H, which is the shortest distance of the tire, the length in the tire axial direction from the tire equator to the radius line divided into three equal parts, and the radial line separated from the tire equator outward in the tire axial direction is the tread surface. The tread 1 which is the shortest distance between the intersection point B where it intersects and the outer surface of the outer belt ply.
厚 thickness BA, twice as long as the length, the intersection D where the radial line separating the tire equator outward in the tire axial direction intersects the tread surface
The tread 2/3 thickness BB, which is the shortest distance between the outer tread and the outer surface of the outer belt ply, and the tread center thickness A are: A-1.0 mm ≦ BA = BB ≦ A-0.5 mm, A −2.0
A steel belted radial tire, wherein mm ≦ H ≦ A−1.0 mm.