JP2002019429A - Bead core, manufacturing method therefor and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and high-quality bead core, a manufacturing method therefor and a pneumatic tire. SOLUTION: This board core 10 is formed so that wires of a winding start row N1 of the bead core 10 and wires of a row N2 of a second stage are wound in advance by dislocating 1/2 pitch, and the number (the winding number) of wires of the winding start row N1 is set less than the number of wires of rows N2 to N5 above the second stage, and a position P0 of the winding start end 11 becomes a position dislocated to the tire axial directional outside by 3/2 pitches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monostrand-type beat core formed by winding a single-wire metal wire coated with rubber a plurality of times in an annular shape, and a method for manufacturing the same.
The present invention relates to a pneumatic tire having the above-mentioned beat core in a pair of right beat portions.

[0002]

2. Description of the Related Art A beat core is a reinforcing member used for a beat portion for fixing a tire to a rim (wheel). In a pneumatic tire, a strand beat 50 as shown in FIG. Is used. The strand beat 50 is formed by winding a ribbon 51 formed by arranging a plurality of metal wires 50w in parallel and covering with a rubber 50g. As shown in FIG. Coated single wire metal wire 60
Monostrand beats 60 that are formed by being wound in an annular shape while w is moved a plurality of times in the row direction and the step direction are also often used. The mono strand beat 60 is usually
In the cross section, a line connecting the centers of the wires 60w is formed to be linear.

[0003]

By the way, in the vulcanization step after the tire is molded, heat and pressure are applied to the green tire.
A tensile stress is generated in the cord of the carcass ply, and the beat core is pulled outward in the tire radial direction, so that tension is generated in the beat core. In the monostrand beat 60, when the position of the winding start end 61 of the wire 60w is inside the tire, the winding start end 61 is pulled in the radial direction of the tire, and the cross-sectional shape of the beat core 60 changes. This change in cross-sectional shape is particularly large in a bias tire, and there has been a problem that, when used repeatedly, a crack occurs at the wire interface and bursts occur. As a means for avoiding this, as shown in FIG. 4, a method has been proposed in which the position P0 of the winding start end 61 is at least one wire inside, but since the line connecting the wire centers is a straight line. After the wire 60w is easy to move and the winding start end 61 in the first row moves inside the tire,
Further, the tire moves in the outer diameter direction of the tire, which easily leads to an early failure. In the vulcanization step, when the winding start end 61 is pulled inward in the axial direction and outward in the radial direction by a carcass ply (not shown), it is expected to move to a position P1 shifted inward in the tire axial direction by only ピ ッ チ pitch. Is done. This is because the wire 60w moves at the start end 6
1 is about 30 cm from the position P0, and for this length, assuming that a uniform force is simultaneously applied to any of the partial wires, the wire 60w is shifted at the position P1 shifted by the half pitch.
The change in the cross-sectional shape of the beat core is small,
Good results should be obtained. However, the molded green tire has a uniform width of about 30 cm from the position P0 of the winding start end 61 due to various variations such as the circumference, the ply angle, the toledo gauge, the folded height of the ply, and the width of the overlap joint of the ply. Since a force is less applied, even if a part of the above 30 cm is subjected to a stress in the direction of the wire 71 located on the innermost side in the tire axial direction of the second stage wire, the winding start end 61 remains at the position P1. Easily and radially outside position P2 inside the tire axial direction
And the change in the cross-sectional shape of the beat core 60 could not be suppressed.

[0004] As an improvement, it is conceivable to increase the total number of wires to reduce distortion between each wire and an adjacent cord, thereby making it difficult for the winding start end 61 to move. However, in this case, although effective in terms of performance, there is a problem that not only the weight of the beat core 60 increases but also the cost increases.

[0005] The present invention has been made in view of the conventional problems, and has as its object to provide an inexpensive and high-quality beat core, a method for manufacturing the same, and a pneumatic tire.

[0006]

In the beat core according to the first aspect of the present invention, when a single wire is annularly wound while moving in a row direction and a step direction a plurality of times, a winding start row is formed. And the wires in the second row are shifted from each other in the tire axial direction.

In the beat core according to the present invention, the positions of the first row of wires and the second row of wires are shifted by a half pitch in the tire axial direction.

According to a third aspect of the present invention, in the beat core, the number of turns of the wire in the first winding row is smaller than the number of turns of the second row of wires.

According to a fourth aspect of the present invention, the beat core is formed such that the winding start end is located at the center of the second row.

According to a fifth aspect of the present invention, in the case of a tire having a rim diameter of not more than 20 inches, the diameter of the wire is set to 1.1 mm to 1.6 mm.

In the beat core according to the present invention, when the single wire is formed in a circular shape while being moved a plurality of times in the row direction and the step direction, the wire in the winding start row is in the second row. It is formed so as to be located in the gap between the wires.

A pneumatic tire according to a seventh aspect is provided with the beat core according to any one of the first to sixth aspects.

In the method for manufacturing a beat core according to the present invention, when the single core wire is annularly wound while being moved plural times in the row direction and the step direction to form the beat core,
It is characterized in that the wires in the winding start row and the wires in the second row are shifted in the tire axial direction and wound.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a monostrand-type beat core 10 according to the present embodiment. The beat core 10 is formed by winding a single-wire metal wire 10w covered with rubber 10g into five steps. . In the present embodiment, the number of wires (the number of turns) of the row N1 at the start of winding of the beat core 10 is changed to the second row or higher (N2
To N5), which is four less than six, which is the number of wires, and formed by winding the wire of the row N1 at the beginning of winding and the wire of the second row N2 with a shift of 1/2 pitch in advance. The position P0 of the winding start end 11 is shifted to the outside in the tire axial direction by 3/2 pitch with respect to the wires 21 to 51 located on the innermost side in the tire axial direction in the second and higher rows. ing. As a result, in a situation where the tire is tightened hard, as in the case where the number of wires in the tire axial direction is increased, the movement between the wires is suppressed, and the change in the cross-sectional shape of the beat core is reduced. Can be significantly improved. Further, the wires 11 to 14 of the winding start row N1 are changed to the wires 22 of the second row N2.
Since it has entered the gap of ~ 26, the row N1 at the beginning of winding
Wire and spacing H ₁ along the tire radial direction of a column N2 of the second stage is narrower than the spacing H _k between the second-stage or more columns. For this reason, since the density of the wires also increases in the tire radial direction, the movement between adjacent wires is reduced, and the durability of the tire is further improved.

As described above, according to the present embodiment, the wire of the row N1 at the beginning of winding of the beat core 10 and the row N
And the number of turns (number of turns) of the wire in the row N1 at the start of winding, while shifting the second wire in advance by 1/2 pitch.
Is smaller than the number of wires in the second and higher rows (N2 to N5) so that the position P0 of the winding start end 11 is shifted to the outside in the tire axial direction by 3/2 pitch. In the vulcanization process, the position P0 of the winding start end 11 hardly moves even when stress is applied in the direction of the second-stage wire 21 located on the innermost side in the tire axial direction, so that the change in the beat cross-sectional shape is suppressed. Be able to
Since the wire density increases both in the tire axial direction and in the tire radial direction, distortion between adjacent wires can be reduced, so that tire performance can be significantly improved.

The shift amount of the position P0 of the winding start end 11 is not limited to 3/2 pitch, but is (2n-
1) / 2 pitch (n: natural number) may be sufficient, but in various cases such as variation on the circumference of the actual raw tire and a water pressure test, it is disadvantageous that the winding start end is on the rande side of the rim. As shown in FIG. 2, the position P0 of the winding start end 11
Is most preferably the center of the number of rows in the second row (here, the position of 5/2 pitch).

In general, the larger the diameter of the wire used for the beat core 10 is, the higher the productivity and the lower the price, but the rigidity is considerably increased.
Adaptation to tires less than 0 inches is difficult. Therefore,
When the rim diameter is 20 inches or less, the diameter of the metal wire is desirably 1.1 mm to 1.6 mm, and more desirably 1.2 mm to 1.4 mm.

[0018]

[Example] LTS 7.00-15 10PR in size
(Carcass; 4 nylon cords used + 2BR), made of metal wire with a wire diameter of 12 mm, four types of wires formed by shifting the wire in the first row and the wire in the second row in advance by 1/2 pitch Beat core (present inventions 1-4)
Table 1 shows the results of a durability test conducted using a test tire having the following. In addition, the conventional tire having the beat core in which the winding start end position was inside by one pitch and three pitches was used as a comparative example (conventional examples 1 and 2). The durability is
The test tires were run under a constant load (220%), and the running times until failure were compared. Of the comparative examples, the running time of Conventional Example 2 having higher durability was evaluated as 100.

[Table 1] As shown in Table 1, the tire having the beat core according to the second aspect of the present invention in which the number of rows in the second and subsequent rows in the row direction is six and the winding start end of the first tier is shifted by 5/2 pitch is also the same as the second tier. The number of windings in the subsequent row direction is six, which has 1.5 times the durability of Conventional Example 2 in which the winding start end of the first row is shifted by two pitches. The present invention 3, wherein the number is 5,
The tire having the beat core of No. 4 also has higher durability than the conventional example 2. As described above, the tire provided with the beat core of the present invention in which the wire in the first row and the wire in the second row are shifted by ピ ッ チ pitch, It has been confirmed that the durability is further improved when the winding start end of the first stage is located at the center of the number of windings in the column direction in the second stage.

[0019]

As described above, according to the present invention,
When winding a single wire a plurality of times in a row while moving in the row direction and the step direction to form a beat core, the wire in the winding start row and the wire in the second row are shifted in the tire axial direction. As it was formed, in the vulcanization process,
Even when tension is applied to the winding start end from the carcass ply in the axial direction and radially outward, the position of the winding start end hardly moves, so that the change in the beat cross-sectional shape can be suppressed. Further, since the wire density is increased in both the tire axial direction and the tire radial direction, distortion between adjacent wires can be reduced, and tire performance can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross section of a beat core of a pneumatic tire according to the present embodiment.

FIG. 2 is a schematic diagram showing another cross section of the beat core of the present invention.

FIG. 3 is a schematic view showing a cross section of a conventional beat core.

FIG. 4 is a schematic diagram for explaining a shape change of a conventional beat core.

[Explanation of symbols]

10 beat core, 10 g rubber, 10 w metal wire, 11 to 14 winding start row wire (11 winding start end), 21 to 51 second row or higher row wire.

Claims (8)

[Claims] In a beat core formed by winding a single wire in a ring while moving in a row direction and a step direction a plurality of times, a wire in a winding start row and a wire in a second row are connected to a tire shaft. Beat core characterized by being formed shifted in the direction. 2. The beat core according to claim 1, wherein the positions of the wire in the first row and the wire in the second row are shifted by a half pitch in the tire axial direction. 3. The beat core according to claim 2, wherein the number of windings of the winding start row is smaller than the number of windings of the second row. 4. The beat core according to claim 3, wherein the winding start end is formed at the center of the second row. 5. The beat core according to claim 1, wherein when the rim diameter is 20 inches or less, the diameter of the wire is set to 1.1 mm to 1.6 mm. 6. A beat core formed by annularly winding a single wire while moving in a row direction and a step direction a plurality of times, wherein a wire in a winding start row is located in a gap between wires in a second row. Beat core characterized by being formed as follows. 7. A pneumatic tire comprising the beat core according to any one of claims 1 to 6. 8. When forming a beat core by winding a single wire a plurality of times in a row while moving in a row direction and a step direction to form a beat core, a wire in a winding start row and a wire in a second row are connected to a tire shaft. A method for manufacturing a beat core, wherein the core is wound in a shifted direction.