JPH02225111A - Tire - Google Patents

Abstract

PURPOSE:To disperse weak points of strength in bead cords for improving rupture resistant strength of beads by making respective end edge positions of plural bead cords facing start end parts of bead cores differ from each other in circular direction by a fixed distance. CONSTITUTION:A bead core 2 arranged in the bead part of a tire is formed of a ring compound 14 for positioning start end part 13 of a lengthy band like body 12 inside the radial direction, continuously wound in plural turns in circular direction in turn, and having a multilayer structure of rectangular shape in its section. The band like body 12 is formed by connecting together plural bead cords 15 arranged in parallel to each other along the length direction thereof into one body. Moreover, respective end edges 15a facing start end parts 13 of respective bead cords 15 are respectively made to end with a fixed different distance in circular direction. Still more, the fixed distance is set more than twice the diameter of the bead cord 15. Weak points due to concentration of shearing stresses at respective end edges 15a of respective bead cords 15 are dispersed in circular direction thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tire with improved bead breaking strength without adding bead cords.

[Conventional technology]

Generally, the bead of a tire is equipped with an annular bead core made of steel cord wrapped in multiple stages to secure the end of the carcass ply and maintain fit with the rim.
Further, the bead core is formed by continuously winding a long belt-like body in which a plurality of cords are arranged side by side many times.

On the other hand, when assembling such a tire into a one-piece rim, as shown in Figure 5, it is necessary to expand the diameter of the bead portion B to pass through the rim flange A. The cord is likely to break due to the tensile stress and shear stress exerted by the cord, which is a so-called "punch break".

Therefore, conventionally, the number of windings of the band-shaped body is increased, or the number of cords is increased to increase the safety factor against the stress, thereby suppressing the single-band breakage.

[Problem to be solved by the invention]

However, with such means, there are problems in that the bead rigidity becomes excessive, which reduces the efficiency of rim assembly, and also increases the weight of the tire and increases production costs.

The present inventors researched the fracture mechanism in order to suppress the bead fracture without adding additional cords. As a result, the bead fracture P is as shown in FIG. ,
It is generated in the first NdI facing outward in the radial direction at the position of the starting end C1 of the band-like body C, and the second and third layers d2 and d3 on the outer side are formed sequentially.
It was found that the code progresses from the inside of the tire to the outside of the tire in the case of -Jid.

This is because each cord edge in the starting end C1 terminates at the same position, so that a weak spot where shear stress concentrates is concentrated at one location at the edge position, and as a result, It is thought that breakage occurs at the position of the starting end CI in order from the cords with a high elongation rate during diameter expansion, that is, the cords on the inner layer, or the cords on the inner side of the tire in the same layer. As shown in Figure 5, the bead part B has an inward slope on its lower surface for the purpose of increasing the fitting force with the rim.
Therefore, the amount of diameter expansion in the inner part of the tire is large, and the elongation rate of the inner cord in the same layer is high.

In particular, when the tire is vulcanized and molded, the tension of the carcass tends to cause the bead core E to undergo a displacement strain in the direction of the arrow F, as shown in FIG. 7, and the breakage becomes more pronounced.

That is, the present invention has been made by focusing on the formation of such weak points in the bead core, and its purpose is to provide a tire that can increase the breaking strength of the bead core without adding cords by dispersing the weak points. It is provided by.

[Means to solve the problem]

In order to achieve the above object, the tire of the present invention includes a long belt-like body in which a plurality of bead cords are arranged parallel to each other, and a starting end of the belt-like body is positioned radially inside and circumferentially. An annular body is formed by sequentially winding the cord a plurality of times, and the edges of adjacent bead cords facing the starting end differ in the circumferential direction by a distance of at least twice the diameter of the bead cord. It has a bead core.

[Effect]

In a bead core constructed in this way, the positions of each end edge of the bead cord facing the starting end are set at different distances in the circumferential direction, making it possible to alleviate the concentration of shear stress and disperse weak points. This makes it possible to improve the overall breaking strength.

Also, since this item does not require additional bead cords,
Rim assembly workability, tire weight, production cost, etc. can be maintained.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, a tire 1 has a toroidal shape having a bead portion 3 having an annular bead core 2, a sidewall portion 4 extending radially outward from the bead portion 3, and a tread portion 5 connecting the upper ends of the sidewall portion 4. A carcass 6 passing through a sidewall section 4 and a tread section 5 is disposed between the bead sections 3, and the tire 1 is constructed by seating the bead sections 3 on a rim base 7. It is attached to the rim 9.

The carcass 6 is secured to the bead core 2 by wrapping both ends around the bead core 2 from the inside to the outside of the tire, and the carcass 6 is made of organic and inorganic fiber cords with a 20-degree angle to the tire equator. A cross-ply structure in which each ply is arranged at an inclination angle of ~70 degrees and the cords between the plies intersect with each other, or a radial structure using plies with a cord angle of about 70 to 90 degrees is adopted. can.

FIG. 1 shows an example of a radial structure having two plies, and a strong belt layer 10 arranged on the outside of the carcass 6 at an angle of inclination of 30 inches or less with respect to the tire equator is attached to the tread 5. By overlapping the tires over almost the entire width of the tires, the tread rigidity is increased and high-speed running performance is improved.

In addition, the bead core 2 is a long strip 12 as shown in FIG.
In this example, it has a multilayer structure with a substantially rectangular cross section, which is formed by sequentially and continuously winding the starting end 13, which is one end of the band 12, in the radial direction in the circumferential direction. It forms an annular body 14.

The strip 12 has a plurality of bead cords 15 made of steel wires made of high carbon steel, etc., which are arranged parallel to each other along the length of the strip 12, and are connected to each other by, for example, topping rubber. The edges 15a, 15a of the adjacent bead cords 15, 5 facing the starting end 13 are formed by integrally connecting them, and end at different distances NL in the diurnal direction, as shown in FIG. are doing.

By making the positions of the adjacent edges 15a% 15a different in the circumferential direction, weak spots that are formed due to concentration of shear stress at the positions of the edge 15a can be dispersed in the circumferential direction. This makes it possible to measure overall strength improvement.

In order to further improve the dispersion of the weak points, the positions of the edges 15a of all the bead cords 15- disposed on the strip 12, not only between adjacent bead cords 15, are made different from each other. More preferably, the positions of the strips 12 are sequentially changed in the same direction from one side edge to the other side edge of the strip body 12.

In order to disperse the weak points, the distance needs to be at least twice the diameter of the bead cord 15, more preferably at least 15 times, and if it is less than twice, the dispersion will not be achieved. This is insufficient, and the effect of improving the breaking strength is inferior.

The tire 1 of this embodiment is provided with a bead apex 16 made of hard rubber that extends from the bead core 2 along the sidewall 4 in a tapered cross-sectional shape to increase the lateral rigidity of the tire. It is attached and passes through the bottom surface of the bead part 3, and the other end is attached to the bead part 3.
Rim 9 is formed by chafer 17 rising along the inner wall.
This prevents wear and tear.

〔Concrete example〕

A tire having the tire structure shown in FIG. 1 and having a bead core based on the specifications in Table 1 and having a tire size of 165SR13 was prototyped, and the bead fracture strength was compared with a conventional product 1.2 by a hydraulic fracture test. In this test, the tire was filled with water, water pressure was applied to the tire to cause it to break, and the water pressure at that time was measured.

As is clear from Table 1, the tire of Example 1 of the present invention showed an improvement in bead breaking strength of about 20% compared to the tire of Conventional Product 1, in which the number of turns of the strip was equal to 1. It is possible to achieve a safety factor comparable to or higher than that of the conventional product 2 tire, which has a high number of cycles.

Table 1 [Effects of the Invention] As described above, in the tire of the present invention, the positions of the edges of the bead cord facing the starting end of the bead core are varied by a predetermined distance in the circumferential direction, so that the strength of the bead cord can be improved. Weak points can be dispersed, and the breakage resistance of the bead can be greatly improved. This also eliminates the need to add bead cords, making it possible to maintain rim assembly workability, tire weight, and production costs.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, Fig. 2 is a cross-sectional view showing an enlarged part of the same, Fig. 3 is a perspective view showing the bead core, and Fig. 4 is a plan view showing the starting end. , Fig. 5 is a line diagram explaining the rim assembly work, Fig. 6 (a) to 6) is a perspective view and side view of a bead core to explain the prior art, and Fig. 7 is a cross section of a tire to further explain the prior art. It is a diagram. *The number in parentheses is an index of burst pressure with conventional product 1 set as 100, and the larger the number, the better. 2...Bead core, 12-...Strip body, 1
3 - Starting end, Work 4 - Annular body, 15 - Bead cord. Adjustment diagram 112 Figure 4 Banquet Figure 5 Figure 6 (b) Figure 7

Claims (1)

[Claims] 1. An annular shape formed by sequentially winding a long belt-like body in which a plurality of bead cords are arranged parallel to each other multiple times in the circumferential direction with the starting end of the belt-like body positioned radially inward. What is claimed is: 1. A tire comprising a bead core having a solid body, and in which the end edges of adjacent bead cords facing the starting end are different in the circumferential direction by a distance of at least twice the diameter of the bead cords.