JPS61271105A - Heavy duty type pneumatic tire - Google Patents

Abstract

PURPOSE:To aim at enhancing the durability of an ultra large size tire without deteriorating the lightweight measure of the tire, by making the strength of plies wound around a bead core occupying the innermost side of the bead section of the tire, greater than that of plies wound around the remaining bead cores. CONSTITUTION:A carcass 2 is composed of plies 2a wound around a first bead core 1a from the inner side to outer side of a tire, plies 2b wound around a second bead core 1b, plies 2c wound around a third bead core 1c and cut plies 2c' wrapping the all bead cores 1a-1c from the outside of the tire and reaching a position near to a bead toe 1d. In this arrangement, the number of plies is so selected that the plies 2a wound around the first bead core 1a occupying the innermost side of the bead section 1 have in particular a strength greater than that of the plies 2b, 2c wound around the remaining bead cores 1a, 1b. Further, the strength of each bead core 1a-1c is made to compete with the strength of each ply 2a-2c.

Description

[Detailed Description of the Invention] (Industrial Application Field) Among the large tires used for large trucks, other construction vehicles, industrial vehicles, etc., it is suitable for heavy-duty pneumatic tires mainly reinforced with a bias structure carcass. Relatedly, this specification describes the weight reduction of this type of tire as an improvement in performance.
The results of the development research to realize this combination are described below.

(Prior art) Heavy-duty tires used for the above-mentioned nine uses have a carcass with a large number of actual plies, in order to give the tire the necessary strength that meets the usage conditions, and the bead portion of the carcass is made of a material that connects to the rim. Under tight seating, at least two bundles, usually two to
Using four bundles of bead cores, each ply group of at least two layers is placed around each of the above-mentioned bead cores, which are impacted at intervals of Ik in the direction of the rotational axis at the bead of the tire. In many cases, the main reinforcement is a bias structure carcass that is rolled up independently. In this case, each bead core has the same structure and the ply group that winds each bead core from the inside to the outside of the tire is also the same. In this example, a cut ply is added from the outside of the tire, passing through the bottom of all the bead cores and reaching the bead toe.

(Problems to be Solved by the Invention) In the above-mentioned conventional ultra-large tires, especially those equipped with 3 to 4 bundles of bead cores, during load transfer during running, the innermost bead core (hereinafter referred to as the first pool) of the bead portion 7) The tension borne by the wound ply group is
・Since the tension of the ply group to the core is larger than that of the ply group, the first core is often made of a bead core structure that allows for a safety factor commensurate with the number of plies in the first core, and a bead core of the same structure is Second,
Third...It was also applied to the core, but such tires are suitable for driving under heavy loads off-road, for example.
The first core of the bead section is pulled outward in the radial direction of the tire due to the impactful bending deformation of the tire, especially when the tire runs over a rocky surface, and as a result, the bead base section immediately below the first core is pulled. However, it rubs against the pace part of the rim, causing wear or heat generation, and then a bead burst occurs in which air fills the pace part at the bottom of the first core and blows through.

-7, users' demands for weight reduction of this type of ultra-large tire are increasing year by year, and if this is followed, it has been feared that the above-mentioned difficulties will become even more severe.

Therefore, an object of the present invention is to propose a heavy-duty tire that can satisfy the bead durability of an ultra-large tire in accordance with the demand for lighter tires.

(Means for Solving the Problems) The present invention comprises a plurality of plies made of organic fiber cords, each ply group having at least two layers, and at least two The pneumatic tire is mainly reinforced with a bias structure carcass that is wound around the bead core of the bundle from the inside to the outside of the tire, and the strength of the group of plies that wind up the bead core that occupies the innermost part of the bead part is used to protect the remaining bead cores. This is a pneumatic tire for heavy loads, which is larger than that of the ply group to be rolled up, and is characterized in that the strong gold of each bead core corresponds to the strength of the ply group to be wound up.

The strength of the ply group is the strength of the ply cord itself,
The strength of a bead core is given by the number of cords driven and the number of braids, and the strength of a ten-thousand bead core is given by the product of the strength of the wire bead itself forming the core gold and the total number of wires used.

Now, Fig. 1 shows the size OR821,00- according to the present invention.
The prototype tire of 3586PR is shown with a calf line cross section,
In the figure, 1 is a bead part, 1a to IC are bead cores, abbreviated as 1st to 8th cores in that order, 1d is a bead toe, 2 is a bias structure carcass, and 3 is a tread.
The scratches are on the sidewall, and 5 indicates the breaker.0 The carcass 2 is wound around the first core la from the inside of the tire to the outside. A ply group 2b of four sheets, and a four-ply group 2Cs wound around the third core 10.Four sheets are also cut from the outside of the tire to wrap around all beads 3a, 1b and IQ and reach near the beat toe ld. For the ply group 20'5, the number of blies is particularly large in the ply group gafc that winds up the first core la occupying the innermost side of the bead portion 1, and the remaining bead cores lb, 10.
This is an example of a distribution where the strength is the highest compared to ply groups 2b and 2(i), which are rolled up seven times.

Here, the first core 1a has 18 stages and 10 rows, and the second core 1b has 1
An example is given in which the third core IC has 10 rows and 10 rows of steel wire wound and laminated, and the strength f of each core corresponds to the strength distribution in the ply group.

The tire shown has a carcass ply 2 code of 18
When using 90/2 't'', the strength of ply group 2b is 7 in the index display with the strength of ply group 2a being 100.
8. Ply group 2C is 59, whereas when each bead core has a wire diameter of 0.9411, the strength is almost proportional to the strength distribution of ply groups 2a to 2C. It became.

In contrast, FIG. 2 shows a comparative example using conventional reinforcement measures (a similar cross section is shown here, but the actual numbers of plies in each ply group 2a to 2o and 20' of the carcass 2 are as shown in FIG. 1). In addition to the same example, not only the first core 1a but also the second core 1b and the eighth core 101c are all arranged in a bead wire arrangement of 18 stages and 10 rows.

In such a bead structure in which 8 to 4 bundles of bead cores are arranged adjacent to each other in parallel to the rotational axis direction, the thickness across the bead part and therefore the width of the bead space in contact with the rim is wide; As described above, the real number of plies of the ply group 2a for winding the first core 1a are replaced with the remaining ply group 2b,
20, and using the safety factor of the first core 1a as a reference, the 21st and 8th cores 11) and No. also have the same bead structure, then these second and eighth cores Ik), 10 are the first core 1a. Not only does this arrangement have a considerable margin of safety compared to the previous model, but it is also clear that such a structure can cause bead bursts, as shown below.

In other words, super large tires roll under heavy loads ξ
Bending deformation is repeated in the rounded bead portion, but the neutral axis of this bending deformation is located between the second to eighth cores lb and 10 in the illustrated three-bundle bead core arrangement, and this rounded bead portion 1, between the first core la and the rim base 1
This is because the bead portion 1 collapses, creating a gap, and the fit there gradually loosens, which leads to further wear and heat generation, further accelerating the wear, which is a vicious cycle. be.

(Function) Based on the above knowledge, in the configuration of the present invention, it is possible to bring the neutral axis of bending deformation of the bead portion l closer to the first core la, and as a result, the fit between the bead base and It is possible to prevent the chance of loosening of the core, and the strength of the second and third cores is relatively lower than that of the first core, and the number of steel cords used can be reduced. There is also the benefit of realizing weight reduction.

(Example) The following example shown in FIG. 1 and the conventional example shown in FIG. The build part surface pressure and the amount of movement of the bead part directly under each of the first to eighth cores were compared, and the results shown in the following table were obtained.

Table 1 (Effects of the Invention) According to the present invention, by taking appropriately proportioned strengthening measures at the bead portion of an ultra-large heavy-duty tire that requires bead reinforcement using a plurality of bead cores, the bead portion can be uniformly and tightly reinforced to the rim pace portion. Since the fit can be maintained for a long time, factors such as wear and heat generation can be effectively suppressed, helping to improve the durability of the bead part of this type of tire, and can also contribute to reducing the weight of the tire by reducing the amount of bead wire used. .

[Brief explanation of drawings]

FIG. 1 is a sectional view of the embodiment, and FIG. 2 is a sectional view of the conventional example. 1... Bead part xa, 11), No... Bead core 2... Carcass 2a, 2b, 20
...Priy group patent applicant Bridgestone Corporation Figure 1 Figure 2

Claims (1)

[Claims] 1.Multiple plies of organic fiber cords are placed in each ply group of at least two layers from the inside to the outside of the tire around at least two bead cores that are impacted at intervals in the rotational axis direction at the bead of the tire. A pneumatic tire whose main reinforcement is a rolled-up bias structure carcass is made, and the strength of the ply group that winds up the bead core that occupies the innermost part of the bead portion is made greater than that of the ply group that winds up the remaining bead cores, and A heavy-duty pneumatic tire characterized by matching the strength of each bead core with the strength of the ply group that winds each bead core.