JPS61295107A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To make improvements in durability of bead part, by dividing a bead core into plural bead wire groups in a radial direction of a tire, while constituting each sectional area of bead wires in the outside group to be smaller than that in the inside group, in case of a radial tire for heavy vehicles. CONSTITUTION:A bead core 1 is constituted of two bead wire groups 2a and 2b divided in a tire radial direction. And, each sectional area of bead wires 5 of the bead wire group 2a situated in an inner side of the tire radial direction is set to be larger than that f bead wires 6 of the bead wire group 2b. With these bead wires formed in a suchlike way, stress acting on these bead wires is almost uniformized so that powerful strength in each bead wire is available so effectively, thus durability in the bead part is improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bead core of a bead portion of a pneumatic tire, for example, a pneumatic radial tire for heavy vehicles.

(Prior Art) - II. In a pneumatic tire, for example, a pneumatic radial tire for heavy vehicles, the bead portion is not the third
There is something like the one shown in the figure. In FIG. 3, 32 is a bead part of a pneumatic radial tire 31 (only a part is shown in the figure), and the bead part 32 forms two annular bodies facing each other, with a large number of Bead wire 40
It has an annular bead core 33 (only a portion of which is shown in the figure). A carcass layer (only a part of which is shown in the figure) 35 made of wire cord is provided between the two bead cores 33, and an end portion 35a of the carcass layer 35 is provided.
The bead core 33 is wound up from the inside in the axial direction of the tire to the outside. 36 is a wire chafer, and although other components are not shown, it goes without saying that ordinary stiffeners and the like are provided.

As shown in FIGS. 3 and 4, the conventional bead core 33 includes a bead wire 40 of one type of wire diameter (for example, one
No. 5 wire, wire diameter 1.55 m, strength 310 kg/piece) is wound in layers from the innermost layer 40a to the outermost layer 40b in the approximate radial direction of the tire, tightly bundled and wound into an annular core (for example, the number of turns 65 pieces).

When the pneumatic radial tire 31 is filled with high-pressure air and used under a load, an extremely large tension acts on the bead core 33 due to the air pressure and the load.
Each bead wire 40 constituting the bead core 33 shares a portion of this tension, but each bead wire 40
The tension acting on the innermost layer 40a is greatest and decreases as it moves upward. Therefore, the bead wire 40 of the conventional bead core 33 has a wire diameter that is strong enough to withstand the tension of the innermost layer 40a, and the bead wire 40 (wire number 15 in this case) having this wire diameter is used.

(Problems to be Solved by the Invention) However, since the tension acting on each bead wire 40 decreases upward from the innermost layer 40a,
The stress acting on each bead wire 40 decreases upward from the innermost layer 40a. Therefore, bead wire 4
If the value is 0, the tightening is weak compared to the kneading that becomes the outer layer.In other words, it can be said that the strength of the bead wire 400 is not used effectively in terms of stress.

When the pneumatic tire 31 is used and transferred, the bead toe 43 moves in the radial direction using the bead heel 42 as a fulcrum as shown in FIG.
When using the bead core 33 configured as described above, as the mileage increases, internal deformation will eventually occur, deforming the shape of the bead core 33, and furthermore, the bead portion (
In particular, a problem arises in that failure occurs at the end portion 35a of the carcass layer 35, etc.).

Therefore, the present invention effectively utilizes the strength of the bead wire in response to the tension acting on each part of the bead core during use of the tire, and prevents the bead core from deforming or malfunctioning even if the tire travels a long distance. The purpose of the present invention is to provide a pneumatic tire with good durability in the bead part.

(□Means for Solving the Problem) A pneumatic tire according to the present invention is a pneumatic tire having an annular bead core. It is characterized in that the cross-sectional area of the bead wires constituting the bead wire group located on the outside is smaller than the cross-sectional area of the bead wires constituting the bead wire group located radially inside.

(Function) When the pneumatic tire is filled with air pressure, loaded, and transferred, large repeated tension acts on the bead core of the pneumatic tire. The bead core is constructed by grouping a large number of bead wires into a hexagonal cross section, and this tension acts in a distributed manner on each bead wire on the cross section. Looking at the tension distribution of each bead wire on the cross section, a large tension acts on the bead wires located radially inside the bead core, and a small tension acts on the bead wires located radially outside.

Since the bead core is the main skeleton that determines the lifespan of a pneumatic tire, the bead wire used is strong enough to withstand the repeated tension applied to the innermost bead wire of the bead core, that is, one with a relatively large cross-sectional area.

Conventional bead cores are made up of bead wires with a large cross-sectional area from the inside to the outside of the bead core, so while the stress generated in the bead wires is appropriate inside the bead core, it becomes too small on the outside, which is wasteful.
It also caused a malfunction.

The bead core of the present invention is divided into a plurality of bead wire groups in the radial direction, and the cross-sectional area of the bead wires forming the outer bead wire group is smaller than the cross-sectional area of the bead wires forming the inner bead wire group. Therefore, the stress generated in the bead wire is the same on the outside as on the inside,
And appropriate. Therefore, no deformation of the bead core occurs, and no failure occurs.

(Example) Hereinafter, an example of a pneumatic tire according to the present invention will be described based on the drawings.

FIG. 1 is a view showing a first embodiment of a pneumatic radial tire for heavy vehicles according to the present invention, and is an enlarged sectional view of a bead core thereof. Components other than the bead core are the same as the conventional pneumatic tire having a bead portion shown in FIG. 3, and detailed description thereof will be omitted.

In FIG. 1, 1 is a bead core, and bead core 1
As shown in FIG. 3, is provided in an annular shape at the center of two opposing bead portions of a conventional pneumatic radial tire for heavy vehicles. The annular bead core 1 has a hexagonal cross section, and its negative side is formed substantially parallel to the bead base 44. Further, the bead core 1 has a plurality of (two in this embodiment) bead wire groups 2a and 2b divided approximately in the radial direction of the tire. The bead wire group 2a is located inside the annular bead core 1 in the radial direction.
The bead wires (wire diameter: 1.55 m, strength: 310 kg/piece) are made of wires having a circular cross section with the same cross-sectional area, and are closely layered from the innermost layer 5a to the outermost layer 5b of the bead wire group 2a. ing. The bead wire group 2b is located outside the annular bead core 1 in the radial direction, and is provided in close contact with the outside of the bead wire group 2a. The bead wire group 2b includes bead wires 6 having a circular cross section with the same cross-sectional area.
(Here, wire number 16, wire diameter 1.30, strength 224
kg), the innermost layer 6a of the bead wire group 2b
From the outermost layer 6b to the outermost layer 6b, the layers are formed in close contact with each other.

In this case, the number of layers of bead wires 6 constituting the bead wire group 2b is three in this example, but it is preferable to laminate at least two or more layers. Here, bead wire group 2
The cross-sectional area of the bead wire 6 constituting b is smaller than the cross-sectional area of the bead wire 5 constituting the bead wire group 2a. The total number of turns of the bead wire 5.6 of the bead core 1 is 65.

FIG. 2 is a diagram showing a second embodiment of the pneumatic tire according to the present invention, and is an enlarged sectional view of the bead core 11 thereof.

In the second embodiment, the bead core 1 of the first embodiment is divided into two bead wire groups 2a and 2b in the substantially radial direction, whereas the bead core 11 is divided into three groups of bead wires in the substantially radial direction.
bead wire groups 12 (from inside to outside 12
The difference is that it is divided into 3 parts (a, 12b, 12c).

The other configurations are the same as in the first embodiment, and their explanation will be omitted. In the second embodiment, since it is composed of three bead wire groups 12, each bead wire group 12a, 22
b, 12c each bead wire 15.16.17
The stress corresponding to the tension acting on the bead core 11 is more appropriate, and the deformation of the bead core 11 is also less.

In addition, in the above-mentioned first and second embodiments, the case where the bead core is divided into two and three parts was explained, but in the present invention, the bead core is not limited to this embodiment, and the bead core is divided into four parts. It may be more than that.

Further, in the first and second embodiments described above, the bead wire has a circular cross section, but the present invention is not limited to this embodiment. may be a polygon or a combination thereof.

Furthermore, in the first and second embodiments described above, the case was explained in which one side of the bead core having a hexagonal cross section was arranged approximately parallel to the bead base and slightly inclined with respect to the axial direction of the tire. In the present invention, one side of the polygon of the bead core may be in the axial direction or may be inclined at about 1.

Furthermore, in the first and second embodiments described above, the pneumatic tires are pneumatic radial tires for heavy vehicles, but the present invention is not limited to these embodiments. Other types may also be used, such as smaller tires or bias tires.

Next, two types of test tires (a tire of the present invention and a conventional tire) were manufactured, and the effects of the present invention were confirmed and will be described.

The tire of the present invention uses the tire of the first embodiment described above,
The conventional tire described above was used.

These test tires were manufactured in the same manner except for the bead core.

The following table shows some of the bead core configurations and performance test results. Regarding bead failure, conventional tires are
00 and expressed as an index; the smaller the index, the better.

(Hereinafter, blank space) The performance test used a normal drum testing machine, and the test conditions were: air pressure 7.3 kg/c4, applied load 3.0 ton,
The vehicle traveled 50,000 km at a speed of 60 km/h. Bead failure after running (separation at the end of the carcass layer)
The occurrence of this was investigated, and the deformation of the bead core shape was also visually inspected. As shown in the table above, the test results show that, compared to conventional tires, the tire of the present invention exhibits minimal deformation of the bead core shape, fewer failures near the bead core, and significantly improved bead durability. I was able to improve.

(Effects of the Invention) As explained above, according to the present invention, the stress acting on the bead wires constituting the bead core during use of a pneumatic tire becomes almost constant, the strength of the bead wires is effectively used, and the shape of the bead cores The occurrence of deformation and failure of other bead parts is drastically reduced, and bead durability can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a view showing a first embodiment of a pneumatic tire according to the present invention, and is an enlarged sectional view of a bead core thereof. Second
The figure shows a second embodiment of the pneumatic tire according to the present invention, and is an enlarged sectional view of the bead core thereof. Figure 3,
FIG. 4 is a diagram showing a conventional pneumatic tire, FIG. 3 is a sectional view of its bead portion, and FIG. 4 is an enlarged sectional view of the bead core 33 of FIG. 3. 1.11...Bead core, 2a, 2b, 12a, 12b, 12cm----
- bead wire group, 5.6.15.16.17... bead wire,
31...Pneumatic tire.

Claims (1)

[Claims] In a pneumatic tire having an annular bead core, the bead core is composed of a plurality of bead wire groups divided approximately in the radial direction of the tire, and the cross-sectional area of the bead wires constituting the bead wire group located on the radially outer side is located on the radially inner side. A pneumatic tire characterized by having a cross-sectional area smaller than the bead wires constituting the bead wire group.