JPH0495511A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve the yield strength of bead cores to improve durability of beads by increasing modulus of longitudinal elasticity of each bead core in the range from 1.0 to 1.3 times the modulus of longitudinal elasticity of an bead core adjacent to it on the outside. CONSTITUTION:With a tire 1, in a pair of right and left bead cores, N pieces of bead cores A, that is, a first bead core A1, a second bead core A2,... the N-th bead core AN are arranged and lined up from the inside to the outside toward the tire-equator CO in the axial direction of the tire. In order to make the strength of beads, a ratio Pi/Pi+1 of modulus of longitudinal elasticity Pi of a bead core Ai, that is, the i-th bead core in the order counted from the inmost, first bead core Al to the outside to modulus of longitudinal elasticity Pi+1 of a bead core Ai+1 adjacent to the bead core (Ai) on the outside is set to be in the range from 1.0 to 1.3. A ratio P1/PN of modulus of longitudinal elasticity PN of a bead core AN on the outermost side to modulus of longitudinal elasticity P1 of the above first bead core A1 is set to be more than 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a pneumatic tire which can be suitably used particularly as a tire for heavy-load vehicles such as aircraft, and which can improve bead strength without increasing the tire weight. Regarding tires.

[Conventional technology]

Tires for heavy-duty vehicles, especially aircraft tires used under harsh conditions of high internal pressure, high loads, and ultra-high speeds, must first be made with sufficient strength to withstand the expansion of the tires due to high internal pressure. Carcass and bead core required. In particular, in a tire with a cross-ply structure, the breaking tension acting on the carcass due to the cord angle is greater than that in a tire with a radial structure, and it is inevitably necessary to increase the number of carcass plies.

Therefore, in aircraft tires with such a loss brining structure, for example, as shown in FIG. At the same time, both ends of the carcass placed across the bead portions are distributed and folded back around each bead core b-, thereby firmly securing an increasing number of carcass plies.

[Problem to be solved by the invention]

However, in a tire in which a plurality of bead cores are provided in each bead portion, a problem arises in that breakage damage progresses from the bead core on the inner side in the axial direction of the tire, reducing bead durability.

This is thought to be due to the fact that in the past, the bead strength was determined by the sum of the strengths of each bead core, and therefore bead cores having the same structure with the same number of bead cords in the cross section were used.

However, in the strain test conducted by the present inventor, that is, by attaching strain gauges g to the bottoms of exposed bead cores b,
As a result of measuring the strain in the circumferential direction of each bead core b in the internal pressure filled and loaded state, the bead part a deforms into a lever shape with the upper end of the rim flange as a fulcrum, and as shown in FIG. 6, the innermost first The amount of strain in the bead core b1 is approximately 30% larger than that of the second bead core b2 located outside it, and the amount of strain e in the second bead core b2 is approximately 30% greater than that of the third bead core located outside it. Furthermore, it has been determined that the amount is about 40% larger.

That is, the present invention basically aims to increase the longitudinal elastic modulus of the bead core on the inner side in the axial direction of the tire in the range of 1.0 to 1.3 times as compared to the longitudinal elastic modulus of the bead core adjacent to the outer side, depending on the amount of strain. The present invention aims to provide a pneumatic tire that can equalize the proof strength of each bead core against applied stress and improve bead durability.

[Means to solve the problem]

In order to achieve the above object, the pneumatic tire of the present invention has the following features:
N bead cores are juxtaposed from the inside to the outside of the tire shaft, and the longitudinal elastic modulus Pi of the i-th bead core from the innermost bead core to the outside, and the longitudinal elastic modulus pi + 1 of the bead core adjacent to the bead core on the outside of the tire shaft. The ratio of Pi/
Pi+1 is set to be 1.0 or more and 1°3 or less, and the ratio P1/PN of the longitudinal elastic modulus PN of the outermost bead core to the longitudinal elastic modulus P1 of the innermost bead core is set to be larger than 1.

The longitudinal elastic modulus can also be increased by increasing the number of filaments in the cross section of the bead core.

[Effect]

In a pneumatic tire configured in this way, among N bead cores arranged side by side from the inside to the outside in the tire axial direction, the longitudinal elastic modulus Pi of the i-th bead core counting from the innermost bead core is determined by the longitudinal elastic modulus Pi of the bead core adjacent to the outside. Longitudinal modulus P
It is set to be 1.0 times or more and 1°3 times or less of i. In other words, the modulus of longitudinal elasticity of the inner bead core is increased to counteract the applied stress that gradually increases toward the inside in the axial direction of the tire, which eliminates weak points in the bead portion and increases the resistance of each bead core to the applied stress. It can be made uniform and the bead durability can be improved.

Furthermore, such an increase or decrease in the longitudinal elastic modulus can be easily and accurately carried out by increasing or decreasing the number of filaments in the cross section of the bead core. Moreover, by reducing the number of filaments in the outer bead core, which would have excessive strength, and increasing the number of filaments in the bead core on the opposite side, bead durability can be improved without increasing the weight of the tire.

〔Example〕

The following is an example of the present invention in which the tire size is H45X1.
7. A case where the tire is formed as an O-20 aircraft bias tire will be explained based on the drawings.

In FIG. 1, a tire 1 includes a pair of left and right bead portions 3, a sidewall portion 4 connected to each bead portion 3 and extending outward in the tire radial direction, and a tread portion 5 connecting the outer ends of the sidewall portions 4. It has a toroidal shape, and inside each of the bead portions 3 are a first bead core A1, a second bead core A2, and a Nth bead core AN, which are arranged side by side from the inside to the outside in the tire axial direction facing the tire equator CO. N bead cores A are arranged. In this example, three bead cores A
This example shows a case where the two are juxtaposed.

Also, around each of the first, second, and third bead cores A1, A2, and A3, a first carcass B1, a second carcass B2, and a third carcass are arranged in order from the inside to the outside of the tire. Both ends of B3 (generally referred to as carcass B) are folded back, and each main part B1 of carcass B1, B2, and B3 is
a% B12. By connecting B11 through the sidewall portion 4 and tread portion 5, each carcass B is placed between bead cores A and A arranged at symmetrical positions across the tire equator CO, respectively. In this example, each carcass B is composed of a stack of a plurality of carcass plies in which carcass cords made of organic fiber cords are arranged at an angle of 25 to 50 degrees with respect to the tire equator, and each bead core A-.
Around the bead core A- due to repeated deformation of the tire.
A coating layer 9 is provided to prevent friction between the carcass ply and the carcass ply, which moves around the carcass ply in a spiral manner. As the Naori-cascord, in addition to nylon, rayon, polyester, wholly aromatic polyester fiber cords, etc. can be used.

In this example, the upper end of the folded part B2b of the second carcass B2 is near the maximum center position of the tire, and the folded part B1b of the first carcass B1, which is on the inside, is below and on the outside. The folded portion B3b of the third carcass B3 has its highest position terminated above the folded portion B2b among the plurality of carcass plies. In this example, the carcass B has a cross-bly structure in which the cords between adjacent carcass plies intersect with each other.

Further, the carcass B is made of a protective ply using a similar organic fiber cord, and is covered with a color layer 11 that surrounds the entire carcass B and passes through the bead portion 3, the sidewall portion 4, and the tread portion 5. The tread portion 5 has reddread rubber 12 on the outside of the tire radius of the color layer 11.
A plurality of layers of breakers IO are wrapped around the tire circumferentially through the breaker IO, reinforcing the tread contact area and improving running performance, while protecting the carcass B.

Also, between the green part Bla-83a of the carcass B and its folded parts Bib to B3b, a bead apex 13 is provided which extends from each bead core A in a tapered manner outward in the tire radial direction.・The tire is reinforced at the oar section 4.

The bead core A used in such a tire is
In this example, as shown in FIG. 2, each long strip 13 is formed by continuous winding in the circumferential direction with the starting end 15, which is one end, located inside in the radial direction. The terminal end portion 16 overlaps the starting end portion 15 inside and outside in the radial direction.

The belt-like body 13 is a cord array body in which a plurality of bead cords 19 made of twisted steel filaments are arranged in parallel in the longitudinal direction, and such a belt-like body 13 is continuously arranged in a ring shape. By winding the
The bee and core A have a plurality of filaments having the same specifications in their cross section. Here, the same specification means that each filament has the same material, the same cross-sectional shape, and the same cross-sectional area. Furthermore, in this example, the respective terminal portions of the bead cord 19 facing the terminal end portion 16 are firmly connected to each other by welding or the like, as shown in FIG. 3, for example, as shown in FIG.
By mutually restraining the movement of each bead cord 19 in the circumferential direction, occurrence of individual loose wires is suppressed and wild wires are prevented.

Furthermore, in order to prevent wild wires, the movement of each bead cord 19 may be restrained independently by forming, for example, a V-shaped concave groove or the like in the end portion of the bead cord 19 to engage with the bead rubber. As the bead cord 19, in addition to the metal fiber cord, high strength and low elongation organic or inorganic fiber cords such as wholly aromatic polyamide fiber cords and glass fibers can be used.

In addition, in the tire 1, in order to optimize the bead strength, the longitudinal elastic modulus Pi of the first bead core At counting from the innermost first bead core A1 and the adjacent bead core Ai+1 on the outer side are determined. The ratio Pi/Pi+1 of the longitudinal elastic modulus Pi+1 is set to be 1.0 or more and 1.3 or less, and the longitudinal elastic modulus PN of the outermost bead core AN and the first
The ratio PI/PN of the bead core A1 to the longitudinal elastic modulus P1 is 1
It is larger.

This means that the longitudinal elastic modulus P of each bead core A is 1.0 times or more and 1.0 times the longitudinal elastic modulus of the adjacent bead core on the outside.
This means that the strength of the inner bead core can be improved by increasing the strength of the inner bead core against the applied stress that gradually increases inward in the axial direction of the tire, increasing the durability of the entire bead portion 3. can increase

As shown in FIG. 6, the above-mentioned range was derived based on the above-mentioned strain test on the bead portion 3 conducted by the present inventor, and in order to make the yield strength of each bead core A uniform against the above-mentioned applied stress, It is preferable to set the ratio Pi/Pi+1 to 1.3. However, in such a case, the longitudinal elastic modulus P1 of the first bead core A1 becomes too large, which greatly impairs rim assemblability. Therefore, in the present invention, the ratio Pi/Pi+1 is set to a range of 1.0 or more and 1°3 or less.

In order to further enhance rim assemblability while maintaining the effect of improving bead durability, it is preferable that the longitudinal elastic modulus P of each bead core A satisfies PI>P2≧-.-≧PN within the above range.

That is, the longitudinal elastic modulus P of at least the first bead core A1
1 is larger than the longitudinal elastic modulus P2 of the second bead core A2, for example, even when the longitudinal elastic moduli of bead cores other than the first bead core A1 are equal to each other, the first bead core A1 becomes the starting point of bead damage. Since the breakage of the material can be suppressed, durability can be improved.

Further, such an increase or decrease in the longitudinal elastic modulus P of each bead core A can be easily and accurately carried out by increasing or decreasing the number of filaments arranged in the cross section of the bead core A, and such an increase or decrease in the number of filaments arranged This can be done by increasing or decreasing the number of windings of the strip 13, increasing or decreasing the number of bead cords 19 arranged in each strip 13, and increasing or decreasing the number of filaments constituting the bead cord 19, either alone or in combination.

Furthermore, it is preferable to increase or decrease the number of filaments disposed while keeping the total number of filaments within the bead portion 3 approximately equal to the total number of filaments of a conventional tire, and in such a case, it is possible to maintain the weight of the tire.

The bead core A may be formed by sequentially overlapping and winding the bead core A and the circular strip 13 on the outside as described above. For example, the bead cord 19 may be formed into a joint tress shape in which the bead cord 19 is continuously wound in a spiral shape and in multiple layers.

〔Concrete example〕

Tire size is H45X17.0-20 and 1300-
A tire of the present invention having a tire weight of 20 was manufactured as a prototype based on the specifications shown in Table 1, and the tire weight and road strength of the trial tire were compared with those of a conventional tire.

The bead strength is expressed as an index in which the internal pressure of a tire assembled on a standard rim is gradually increased to 15 ktrf/dx4, and the internal pressure that causes bead damage is set as 100 for the conventional tire. The larger the index value, the better the bead strength.

〔Effect of the invention〕

Like soft soil, the tire of the present invention has the longitudinal elastic modulus of each bead core increased in the range of 1.0 times or more and 1.3 times or less compared to the longitudinal elastic modulus of the bead core adjacent to the outside. The yield strength of the bead core can be improved according to the applied stress, and the bead durability can be improved.

The present invention can be formed as a tire with a radial structure in addition to a cross-bly structure, and can be used in heavy-duty vehicles such as industrial vehicles as well as aircraft.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, Fig. 2 is a perspective view showing a bead core, Fig. 3 is a perspective view showing an enlarged part of the bead core, and Fig. 4 is another embodiment of the bead core. FIG. 5 is a partial sectional view illustrating a conventional tire; FIG.
The figure is a diagram showing the amount of strain occurring in each bead core. A, AI, A2, A3, Ai, AN-bead core. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura 2 No. 1/3 ＼ ＼ Figure 4 5F

Claims (1)

[Claims] 1 N bead cores are juxtaposed from the inside to the outside of the tire shaft, and the longitudinal elastic modulus Pi of the i-th bead core from the innermost bead core to the outside is adjacent to the bead core on the outside of the tire shaft. Ratio P to the longitudinal elastic modulus Pi+1 of the bead core
A pneumatic tire in which i/Pi+1 is 1.0 or more and 1.3 or less, and the ratio P1/PN of the longitudinal elastic modulus PN of the outermost bead core to the longitudinal elastic modulus P1 of the innermost bead core is greater than 1. . 2. The pneumatic tire according to claim 1, wherein the bead core is composed of a plurality of filaments having the same specifications, and the longitudinal elastic modulus is increased by increasing the number of filaments.