JPS582647Y2 - radial tires - Google Patents

Description

[Detailed explanation of the idea] This invention relates to radial tires.

More particularly, the present invention relates to a radial tire having an improved breaker made of steel cord.

Conventionally, radial tire breakers for passenger cars have been made by overlapping two plies reinforced with steel cord and folding both ends of one ply to wrap around the ends of the other ply, or by overlapping three or more plies. There are known structures in which the number of plies varies non-uniformly between the breaker and the gold mine.

However, the radius of curvature of the folded portion of such a breaker is considerably large because it is limited by the thickness of the ply interposed therebetween.

Therefore, when the breaker undergoes bending deformation in the circumferential direction during use of the tire, stress concentration occurs in the rubber and steel cords at the folded portions, resulting in a disadvantage that they are prone to breakage due to fatigue.

Furthermore, the conventional radial tires provided with the above-mentioned breakers generally have the disadvantage of being hard and providing poor riding comfort.

The purpose of this invention is to eliminate the above-mentioned drawbacks of the conventional tires, and to provide a radial tire for passenger cars that has a soft and good ride quality, without causing substantial damage to the breaker even after driving for 40,000 miles. It is to do so.

The radial tire of this invention, which achieves the above object, is made of steel cords, and consists of two plies in which the steel cords are arranged to intersect in opposite directions within a range of 10' to 30' with respect to the tire's equatorial plane. a breaker is disposed between the trend and the carcass, at least one of the plies is folded back at the end without intervening other plies, and the breaker is arranged substantially over the gold mine in radial cross section. 2 layers, and the folding width (W) of the ply is in the range of at least 10'IIg1 or more and 10 or less of the breaker width (Ll), and the diameter of the strands constituting the steel cord and one It is characterized in that the relationship between the number of wires N in the code is ND'<0.011 (m').

The details will be explained below with reference to embodiments of the invention shown in the drawings.

1 to 3 show an embodiment of this invention, in which 1 is a pair of beads spaced apart in the axial direction, 2 is a pair of sidewalls, 3 is a tread portion, and 4 is a carcass. The carcass is formed of twisted strands of rayon, nylon, polyester, wire or glass extending in the radial direction and interconnecting the beads 1, and having substantially equal and regularly spaced circumferentially arranged strands of rayon, nylon, polyester, wire or glass. reinforced with non-stretchable cord.

Reference numeral 5 denotes a breaker consisting of a pair of plies 6.7, which has a width L1 approximately equal to the width of the tread 3, and is provided between the tread 3 and the carcass 4.

A pair of plies 6, 7 are parallelly arranged steel cords extending diagonally across the tire equatorial plane for each ply, and the cords are arranged in the adjacent 6, 7 by 10° to 10° with respect to the tire equatorial plane. They are arranged at equal but opposite angles within 30''.

The width L1 of the ply 7 placed on the ply 6 having the width L2 is L2+2W, but the portions of the width W from both ends are folded back and overlapped on themselves with the radius of curvature extremely small. As a result of the mating, the plies 7 lie with an extent of Ll in the axial direction.

Ll, L2. Since there is the relationship L1-2W=L2 between W, this breaker 5 has substantially two layers in any cross section in the width direction.

Therefore, the rigidity in the width direction becomes uniform.

In addition, they have substantially the same gauge thickness, providing good riding comfort.

Further, when the folding width W of the ply 7 is set to less than 10 layers M, even if it is folded, it rebounds and returns to its original state, and even if it is not folded beyond iom, it does not rebound and the folded state can be maintained.

Experiments have revealed that if the bending angle is less than iom, the bent state tends to return to its original state during driving.

Furthermore, it has been found that if the folded width W of the ply exceeds the width of the breaker, stress concentration occurs during high-speed running, impairing high-speed durability.

Further, the width L2 of the ply 6 is equal to L1-2W as described above, but it must not be smaller than this in order to prevent a portion where the ply does not overlap.

Furthermore, the fatigue resistance of the folded portion against bending deformation is related to the bending rigidity of the steel cord.

It is known that bending rigidity is proportional to the product of Young's modulus E and the second moment of area ■, which is determined only by the cross-sectional shape and size. Especially when the cord wire has a circular cross-sectional shape, its diameter is defined as D. Then, the second moment of area I
= −g D'.

Therefore, the bending rigidity of a steel cord is approximately proportional to ND' when multiplied by the number of strands N. As a result of selecting various values of ND4 and conducting various experiments, we found that ND'<0.0.
11 (ya') reduces the bending rigidity without reducing the strength and Young's modulus of the cord, thereby preventing breakage at the folded part of the ply even when running on 40,000 axes, as shown in the experimental example below. Since the breaker as a whole is easier to bend and blends better with the rubber, it is also possible to obtain a soft and comfortable ride.

In other words, the numerical value (ND'< 0.011 CM') is
As shown in the table on page 9 showing the test results for Tire Arashi A-F, which are normally adopted as radial tires for passenger cars, the running test results show that tires AA and B
Since good results were obtained after driving 40,000 miles,
This numerical limitation was obtained by determining their ND' values.

Note that the radius of curvature in the cross section of the breaker 5 should be as large as possible in order to reduce the bending deformation of the folded end of the breaker.

On the other hand, since the radius of curvature in the cross section of the carcass 4 is smaller than the radius of curvature of the breaker 5, the distance between the breaker 5 and the carcass 4 tends to gradually become smaller.

This gap is filled with a rubber filler 8 made of relatively soft rubber.

Figures 2 and 3 show other embodiments of the breaker according to the present invention.
The breakers 10, 20 are both folded back into two sheets and are constructed by overlapping plies 11, 12 or 21, 22 which are overlapped on themselves, Ll, L2.
The relationship between W is L1 to 2W as in the embodiment shown in FIG.
``This is a relationship of FL2, and it is actually 2 during the breaker eclipse.
It's layered.

The action and effect of the breaker according to this embodiment are the same as those of the breaker according to the previous embodiment.

Experimental example (1) Single-layer breaker structure: Tires AA and B
,C.

The structures D and E are shown in FIG. 1, and the tire storm F has a three-layer structure with other plies sandwiched between both ends of the bent portion, and a two-layer structure in the center.

(2) Carcass layer: Rayon 90' (3) Tire type: 165-13 (air pressure 19 to 2/
cTL) (4) Tire speed: average 50A772/hour The results of the running test using each of the above tires are as shown in the following table.

As is clear from the table above, tires A and B suffered virtually no damage to their breakers even after 44 hours of running.

Therefore, it can be seen that under the above experimental conditions, the radial tire according to this invention is capable of running for more than 40,000 miles.

As a result, the value of ND' of the steel cord of the ply 7 forming the folded part is smaller than 0.011 (71g14), preferably smaller than O,oo5(m':], so that the folded part 7 It was confirmed that the fatigue resistance of ′ was further reduced.

As mentioned above, the radial tire according to this invention has two plies made of steel cord as a breaker, and at least one of the plies is folded back at the end without any other ply intervening. Stress concentration occurs at the bent end, and furthermore, since the breaker has substantially two layers over the entire thickness of the radial cross section, the stress concentration is dispersed and alleviated.

In addition, since the terminal of the breaker folding part is located at a distance of more than iom from the end, interference due to discontinuous boundaries coming close to each other is less likely to occur, and the terminal of the folding part is separated from the side edge of the folding part. Since the width of the breaker is within 10 of the breaker width L1, stress concentration at the turn-back terminal during high-speed running is also less likely to occur.

In addition to these conditions, the code structure is further changed to ND'<
By setting it to 0.011, the bending stiffness of the cord is reduced without reducing the strength of the cord, and stress concentration at the folded portion is reduced.

Each of the above requirements is organically polymerized, and the stress concentration on the breaker folded part and the breaker folded terminal is comprehensively alleviated, and as a result, extremely high durability and high-speed durability are achieved. That will happen.

Conversely, if even one of the above requirements is lacking, sufficient durability cannot be obtained due to stress concentration.

In addition, in this design, the relationship between the diameter of the strands of the steel cord and the number of strands N is set to ND'<01011 [71g14] to keep the bending rigidity low. Since the breaker is essentially two-layered, it is extremely flexible while maintaining sufficient strength and Young's modulus, and blends well with rubber, making it extremely soft and comfortable for passenger cars. We will be offering radial tires.

[Brief explanation of drawings]

The drawings show one embodiment of this invention, and FIG. 1 is a diagram schematically showing a radial cross section of a radial tire having a breaker according to the invention, and FIG. 2 is a diagram showing a radial tire having a breaker according to the second embodiment.
FIG. 3 is a diagram schematically showing a cross section of a breaker according to the third embodiment. 1...Bead, 3...Tread section, 4...Carcass, 5...Breaker-8

Claims (1)

[Scope of utility model registration request] The steel cord consists of two plies arranged in opposite directions within a range of 10° to 30° with respect to the tire equatorial plane, and at least one of the plies is attached to the end without intervening other plies. In a radial tire in which a breaker which is folded back is placed between the trend and the carcass, the breaker is arranged so that the breaker is folded over the radial cross-section substantially in two directions, without using any other breaker in conjunction with the breaker.
layer, and the folded width (W) of the ply is at least 10w1 and less than the breaker width (Ll), and the diameter of the strands constituting the steel cord and the diameter of the wire in one cord are The relationship between the number of strands N is ND'<0.011
A radial tire for a passenger car, characterized in that it is configured as (m).