JP2001030371A - Ring for retaining bead core and manufacture of pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To retain a bead core in a polygonal shape by providing bead core supporting parts and broken parts. SOLUTION: This ring for retaining a bead core comprises bead core supporting parts 4 having fitting faces 3 which fit to the inner peripheral face b2 of the bead core (b), projecting in the axial direction, on the inner peripheral edge part 2a of a disclike base part 2 which receives the side face b1 of the bead core (b). The bead core supporting parts 4 have broken parts 5 disconnected in the circumferential direction and therefore, can retain the bead core (b) in a polygonal shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring for retaining a bead core which is useful for improving the uniformity of a pneumatic tire and a method for manufacturing a pneumatic tire.

[0002]

2. Description of the Related Art FIG. 11 illustrates a conventional bead core holding ring a used in a tire manufacturing process. The bead core holding ring a is continuous in a circumferential direction in which a disk-shaped base portion c for receiving the side surface b1 of the bead core b and an inner peripheral surface b2 of the bead core b are fitted to an inner peripheral edge of the base portion c. A bead core supporting portion e having a fitting surface d is provided so as to protrude in the axial direction. Further, a bead apex f having a substantially triangular cross section may be attached to the outer peripheral surface of the bead core b in advance. This bead core holding ring a is, for example, a first forming drum D1 as shown in FIG.
Used in The first molding drum D1 includes a drum main body g that forms a central portion in the axial direction, and turn-up bladders h that are located on both sides thereof and have a smaller diameter than the drum main body g. The turn-up bladder part h
It has a bladder i which can be expanded by being filled with gas or the like.

FIGS. 13 to 15 are enlarged sectional views of a portion X in FIG. In FIG. 13, a sheet-like raw carcass ply p is cylindrically wound around the first forming drum D1 in a state where the bladder i is contracted. Both ends of the raw carcass ply p protrude and are wound around the turn-up bladder part h. A bead core b in which the bead apex f is bonded to the outer peripheral surface in advance is mounted on the bead core holding ring a, and the bead core a is moved in the arrow y direction from both outer sides in the axial direction (only one is shown in FIG. 13). The moving tool (not shown) can approach the raw carcass ply p having a cylindrical shape. Then, for example, as shown in FIG. 14, the side face b1 of the bead core b is
, And the bead core b is attached to the raw carcass ply p using the adhesive force of the raw carcass ply p. Thereafter, the bead core holding ring a moves in the arrow z direction, and only the bead core b remains on the raw carcass ply p side.

Next, as shown in FIG. 15, the bladder i of the turn-up bladder part h is expanded, and the bladder i is expanded by using a pressing tool j or the like, so that the bladder i is axially outside the bead core b. Both ends of the carcass ply p can be wound up around the bead core b. Thus, the first tire raw cover having a cylindrical shape is formed. This first tire raw cover has bead cores b, b
By expanding the space between the bead cores of the first raw tire cover while approaching the gap in the axial direction, and attaching tread rubber, side rubber or the like, the second raw tire cover having a toroidal shape is formed. And the tire
By vulcanizing and molding the raw tire cover with a mold.

[0005]

The pneumatic tire is desirably formed in a perfect circular shape. However, since the pneumatic tire is manufactured through the above-described manufacturing process, the thickness of the tread rubber is large. However, it is unavoidable that the diameters differ in the circumferential direction and that the dimensions and the shape are distorted. For this reason, for example, on a drum testing machine, when a constant load is applied to the tire and the tire is rotated while keeping the distance between the drum axis and the tire axis constant, the non-uniformity of the tire appears as a fluctuation of the reaction force. The radial component of this variation is called a radial force variation (hereinafter sometimes referred to as RFV), and the longitudinal component is called a tactical force variation (hereinafter sometimes simply referred to as “TFV”). These are the main causes of vehicle body vibration and vehicle interior noise.

Further, for example, when a raw waveform of RFV is subjected to Fourier analysis, a primary vibration component that draws one cycle per tire rotation, a secondary vibration component that draws two cycles, and
It can be decomposed into fifth-order vibration components. If a specific order component of the RFV is large, the vibration may resonate with the natural frequency of the vehicle body in a specific speed range, and the vibration of the vehicle body such as a steering wheel vibration or an unpleasant muffled sound may occur. May generate noise inside the vehicle. Such a problem is a serious problem particularly in a tire for a passenger car that requires a high level of quietness and comfort.

Conventionally, in order to improve the uniformity of a tire, for example, a method of buffing a vulcanized and molded tread surface to make it closer to a perfect circle, or forming a carcass, belt, and tread when forming a raw tire cover. There has been proposed a method of distributing the seams of rubber or the like at substantially equal intervals in the circumferential direction, and relatively low order vibration orders such as primary and secondary are being reduced at a considerable level. However, there is still room for improvement with respect to third-order and higher-order vibration components.

The present invention has been devised in view of such circumstances, and is based on the improvement of the bead core holding ring.
In particular, it is an object of the present invention to provide a method for manufacturing a bead core holding ring and a pneumatic tire that are useful for reducing high-order vibration components.

[0009]

According to a first aspect of the present invention, there is provided a fitting surface which fits on an inner peripheral edge of a disk-shaped base portion for receiving a side surface of a bead core, the inner peripheral surface of the bead core. A bead core holding ring having a bead core holding portion having a substantially polygonal shape by projecting a bead core supporting portion having an axial direction, and the bead core supporting portion having an interrupted portion interrupted in a circumferential direction. It is.

[0010] The bead core supporting portion is formed of a plurality of pieces having the same circumferential length, and the discontinuous portion is formed of a plurality of pieces having the same circumferential length. It is desirable to keep it in a substantially regular polygonal shape. It is desirable that the number of the bead core supporting portions is 3 or more and 7 or less.

According to a fourth aspect of the present invention, a pair of substantially polygonal bead cores are externally fitted from the axial outside of a cylindrical raw carcass ply wound around a first forming drum, and Turning both end portions of the first tire raw cover around the bead core to form a first tire raw cover; and The raw carcass ply is brought into close contact with the inner peripheral surface of the bead core by deforming it into a substantially circular shape by expanding the diameter of the second forming drum, and the space between the pair of bead cores is expanded to form a toroidal second shape.
And a step of vulcanizing the second tire green cover to form a pneumatic tire. And
In this manufacturing method, each of the bead core holding rings described above can be suitably used.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 illustrates a perspective view of a bead core holding ring (hereinafter, may be simply referred to as a “ring”) 1 of the present embodiment, and FIG. FIG. 2B is an enlarged sectional view taken along line AA of FIG. In the figure, the ring 1 has an inner peripheral edge 2a of a disk-shaped base portion 2 which receives a side surface b1 of a bead core b.
Further, a bead core supporting portion 4 having a fitting surface 3 that fits into the inner peripheral surface b2 of the bead core b is provided so as to protrude in the axial direction.

The base portion 2 is made of, for example, a metal material. In this embodiment, the base portion 2 is formed of an annular plate whose outer peripheral surface and inner peripheral surface are both circular. The base portion 2 has an opening O surrounded by an inner peripheral surface thereof, and the opening O is extrapolated to the raw carcass ply p wound cylindrically around the above-described first forming drum D1 or the like. At this time, it is configured so as not to collide with the turn-up pladder portion h.

In this embodiment, the bead core support 4
Are arranged at intervals in the circumferential direction by having a break 5 interrupted in the circumferential direction. More specifically, the bead core support 4 is, as shown in FIG.
A plurality of pieces having the same circumferential length La, in this example 5
The discontinuous portion 5 has a plurality of circumferentially identical lengths Lb, in this example, five. That is, the bead core support portion 4 of this example has the same circumferential length L.
The example in which a plurality of pieces having a are arranged at equal intervals in the circumferential direction is illustrated. In the present embodiment, the fitting surface 3 of the bead core support 4 is formed by an arc surface slightly larger in diameter than the inner peripheral surface b2 of the bead core b.
As shown in FIG. 2 (B), the width Wa of the bead core supporting portion 4 projecting from the surface of the base portion 2 in the axial direction is, for example, smaller than the width Wb of the bead core b. This prevents the bead core support 4 from contacting the raw carcass ply.

As shown in FIG. 3A, the bead core b is generally formed in a circular shape in plan view by spirally winding a metal element wire in multiple stages and multiple rows in the circumferential direction. .
When such a circular bead core b is fitted and held on the ring 1 of the present embodiment, as shown in FIG. 3B, the bead core b is flattened at the discontinuity portion 5 and is brought into contact with the bead core support portion 4. It can be slightly deformed and held in a substantially polygonal shape having the contact position as the vertex S, in this example, a substantially regular pentagonal shape. In FIG. 3B, the bead core b
Is exaggerated for easy understanding, and in reality, the amount of deformation is much smaller than that in the figure.

Next, a method of manufacturing a pneumatic radial tire using such a substantially polygonal bead core b will be described. First, the raw carcass ply p is wound using the first forming drum D1 shown in FIG. Further, the bead core b is mounted on the ring 1, the bead core that has been minutely deformed is attached to the raw carcass ply p, and both ends of the raw carcass ply p are rolled up to manufacture a first cylindrical raw tire cover. In this example, the bead core holding rings 1 on both sides are arranged in phase so that the bead core support portions 7 face each other at the same position. FIG. 4A is a plan view (partially sectional view) of the first tire raw cover thus formed,
FIG. 4B is an exaggerated cross-sectional view taken along the line BB. As is clear from FIG. 4, the polygonal minute deformation remains in the bead core as strain.

Next, as shown in an exaggerated manner in FIG. 5, the first tire raw cover p1 is extrapolated to a second molding drum D2 whose diameter can be enlarged and reduced, and the outer peripheral surface of the second molding drum D2 is gradually increased. The diameter is expanded. The second forming drum D2 includes a first segment SG1 that is freely movable in a radial direction and a second segment SG2 whose circumferential length is smaller than the first segment SG1, and the first and second segments SG1 and SG2. Are alternately connected in the circumferential direction to form the maximum diameter, and only the first segment SG1 is connected in the circumferential direction to form the minimum diameter state.

The second forming drum D2 has a substantially perfect outer peripheral surface. Therefore, when the diameter of the second forming drum D2 increases, the bead core b in which the distortion remains is pressed from the inside in the tire radial direction and finally deformed into a perfect circle as shown in FIG. It can adhere to the raw carcass ply p all around. At this time, as shown in FIG.
In the vicinity of the apex S, a radial pressing force due to the expansion of the diameter of the second molding drum D2 acts with a delay compared to other portions. Thereby, near the apex S of the bead core b, the inner peripheral surface b2 of the bead core b and the raw carcass ply p
There is a time lag in the close contact. Such a partial adhesion delay between the raw carcass ply p and the bead core b, coupled with the expansion of the diameter of the second molding drum D2, causes the cord path, which is the axial length between the bead cores b and b of the carcass, to pass through the tire circumference. The direction is not uniform.

Next, as shown in FIG. 7, the pair of bead cores b are expanded in a toroidal shape while reducing the axial distance between the pair of bead cores b.
A toroidal second raw tire cover p
2 can be molded. Also, the second tire raw cover p2
Is cured to form a pneumatic tire, whereby a pneumatic radial tire is manufactured.

In the pneumatic radial tire manufactured as described above, the code path of the carcass is not uniform in the tire circumferential direction, and the code path of the portion near the apex S of the bead core b is particularly large as compared with the others. Formed. In this portion, when the tire is filled with the internal pressure, the tension of the carcass cord becomes low. In this way, five places where the rigidity of the carcass is relatively low are formed at equal intervals in the circumferential direction.
Such a tire generally tends to slightly increase the fifth-order vibration order of the RFV. For example, when applied to the manufacture of a tire having a large fourth-order vibration order of the RFV, the RFV
And the fourth-order vibration order can be relatively reduced. In other words, for a tire having a problem with the fourth-order vibration component of the RFV, it plays a role in improving uniformity.

As described above, when a pneumatic radial tire having a relatively large nth-order vibration component of RFV is present, the bead core is substantially N-gonal (where N is a natural number larger than n, especially a prime number). Or n + 1 or n
By forming the first tire raw cover by minute deformation to +2), it is possible to reduce the vibration component of the deteriorated order.

Here, it is desirable that the number of the bead core supporting portions 4 capable of forming the bead core b in the polygonal shape as described above is, for example, three or more and seven or less. Or 7) is desirable in that overlapping of the order components can be prevented. Further, the length La in the circumferential direction per one bead core supporting portion 7 and the like can be appropriately determined. For example, the minimum circumferential length La is as follows.
Assuming that the inner peripheral length of the bead core b is “A”, it can be defined as “A ÷ (number of discontinuous portions 5 × 2)”. However, if the circumferential length La of the bead core support 4 is too large, the effect of the break 5 tends not to be sufficiently obtained. From such a viewpoint, it is desirable that the circumferential length per one of the discontinuous portions 5 be 20 mm or more.

FIG. 8 is a plan view of a ring 1 showing another embodiment of the present invention. In this example, a bead core supporting portion 4 is provided with a joint portion 6 for joining between the four.
FIG. 1 shows a structure in which the discontinuous portion 5 is formed by forming a concave surface. In this case, it is preferable that the bead core support portion 4 is suitably reinforced by the joint portion 6 and durability can be improved.

In the embodiment described above, the circular bead core b is minutely deformed into a substantially polygonal shape by holding the bead core b with the bead core holding ring 1. However, for example, the bead core is formed in a substantially polygonal shape in advance. The bead core holding ring 1 according to the present embodiment
It is also possible to adopt a configuration in which the sheet is held and conveyed by using, and is attached to the raw carcass ply p. In addition, in the above-described embodiment, the bead core supporting portions 4 are arranged at regular intervals, but may be arranged at random. Further, the fitting surface 3 of the bead core support 4 is
Although the one configured by the arc surface is shown, various surface shapes can be adopted without being limited to this.

[0025]

First, five radial tires for passenger cars (comparative example) having a tire size of 215 / 65R15 were manufactured by a conventional general manufacturing method, RFV and TFV were measured, and data of each of the five tires was measured. Were averaged and the vibration components of the first to ninth orders were examined. The measurement conditions such as RFV were such that each tire was assembled on a rim of 15 × 6.5 J
The test was performed at a speed of 120 km / H and a load of 5210 N using a drum tester while filling 0 kPa. The results of the test are shown by dotted lines in FIGS. In particular, this tire has a problem with respect to the fifth order vibration component of RFV.

Next, five radial tires (embodiments) of the same size were manufactured by using a bead core holding ring in which seven bead core supporting portions shown in FIG. , And TFV were measured.
The result shown by the solid line at 0 was obtained. As is clear from the figure, it was confirmed that the problematic fifth-order component of RFV was significantly reduced, and that the TFV was also significantly reduced in the second, third, and fifth-order components. 7
The increase in the next component was very small.

[0027]

As described above, in the bead core holding ring according to the first to third aspects, the bead core can be held in a substantially polygonal shape by including the bead core support portion and the discontinuous portion. It is possible to form the first raw tire cover and the like while leaving such deformation strain. By manufacturing a tire using such a first raw tire cover, the code path of the carcass can be made different in the tire circumferential direction, and for example, a specific-order vibration component such as RFV can be reduced.

According to the fourth aspect of the present invention, it is possible to obtain a pneumatic tire in which the code path of the carcass is not uniform in the tire circumferential direction. Therefore, the tension of the carcass cord at the time of filling the internal pressure has a relative variation in the tire circumferential direction. Such non-uniformity of rigidity in the tire circumferential direction can be relatively reduced by dispersing a specific vibration order of the RFV, and thus can increase uniformity.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a bead core holding ring according to an embodiment.

FIG. 2A is a plan view thereof, and FIG. 2B is an enlarged sectional view taken along line AA.

FIG. 3A is a plan view of a bead core, and FIG. 3B is a plan view showing a state where the bead core is fitted to a bead core holding ring.

FIG. 4A is a plan view (partially sectional view) showing a first tire raw cover, and FIG. 4B is an enlarged sectional view taken along line BB of FIG.

FIG. 5 is a partial cross-sectional view illustrating an extrapolated state of a first tire raw cover and a second molding drum.

FIG. 6 is a partial cross-sectional view illustrating an extrapolated state of a first tire raw cover and an enlarged second forming drum.

FIG. 7 is a cross-sectional view illustrating a second tire raw cover.

FIG. 8 is a plan view illustrating another embodiment of a bead core holding ring.

FIG. 9 is a graph showing a waveform diagram of RFV.

FIG. 10 is a graph showing a waveform diagram of TFV.

FIG. 11 is a perspective view illustrating a conventional bead core holding ring.

FIG. 12 is a front view illustrating a first forming drum.

FIG. 13 is an enlarged sectional view of a portion X in FIG.

14 is an enlarged sectional view of a portion X in FIG.

FIG. 15 is an enlarged sectional view of a portion X in FIG. 12;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core holding ring 2 Base part 3 Fitting surface 4 Bead core support part D1 First forming drum D2 Second forming drum

Claims (5)

[Claims] 1. A bead core supporting portion having an engagement surface fitted to the inner peripheral surface of the bead core is axially protruded from an inner peripheral edge of a disk-shaped base portion receiving a side surface of the bead core. A bead core retaining ring, wherein the support portion has a discontinuous portion interrupted in a circumferential direction to hold the bead core in a substantially polygonal shape. 2. The bead core supporting portion is composed of a plurality of circumferentially identical lengths, and
The bead core holding ring according to claim 1, wherein the bead core is held in a substantially regular polygonal shape by being formed of a plurality of pieces having the same circumferential length. 3. The method according to claim 2, wherein said bead core supporting portion has three or more
The bead core holding ring according to claim 1 or 2, wherein the number is equal to or less than the number. 4. A pair of bead cores each having a substantially polygonal shape from the outside in the axial direction of a cylindrical raw carcass ply wound around a first forming drum, and both ends of the raw carcass ply are connected to the bead cores. Turning the bead core of the first tire raw cover externally inserted into a second molding drum capable of expanding and contracting, and turning the bead core of the first tire raw cover outside the second molding drum. By deforming the carcass ply in a substantially perfect circle by the diameter, the raw carcass ply is brought into close contact with the inner peripheral surface of the bead core,
And a step of inflating the pair of bead cores to form a toroidal second green tire cover, and a step of vulcanizing the second green tire cover to form a pneumatic tire. Method for manufacturing tires containing steel. 5. The pneumatic pneumatic pump according to claim 4, wherein the bead core is held by the bead core holding ring according to any one of claims 1 to 3, and is externally fitted to the raw carcass ply. Tire manufacturing method.