JP2015116837A - Pneumatic tire and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a large air reservoir from being produced when a carcass ply is stuck.SOLUTION: A pneumatic tire includes a carcass ply 7 that is stuck by being folded back to the outside from the inside at a toe of bead and the tip part of which has a coating layer 9. A tip edge of the coating layer 9 comprises a displacement part 12 in which a dent part 10 and a bulge part 11, formed by being increased/decreased in a radial direction of the tire, are repeated three times or more.

Description

  The present invention relates to a pneumatic tire and a method for manufacturing the same.

Conventionally, a pneumatic tire having the following configuration is known.
In Patent Document 1, before the end of the raw carcass is folded around the raw bead core, a stress relaxation rubber layer is arranged so as to overlap the inside and outside of the end so as to wrap the end. A pneumatic tire is disclosed.
Patent Document 2 discloses a tire bead assembly component in which a wire scarcass splice portion between a winding start portion and a winding end portion of a belt-like body and a bead filler skacus splice portion of a bead filler are located at the same position on the circumference. A pneumatic tire using a tire is disclosed.
Patent Document 3 discloses a pneumatic tire in which the cross-sectional area of the bead filler is repeatedly changed in the tire circumferential direction.
Patent Document 4 discloses a pneumatic tire in which the outer edge in the radial direction of the bead apex rubber forms a wavy line extending in the circumferential direction by repeating peaks and valleys in the radial direction.

  However, in any of the above pneumatic tires, when forming a green tire before molding, especially when a carcass ply is attached, it is prevented that a large air pocket is generated due to a step at the final tip edge. There is no disclosure or suggestion of a configuration for doing so.

JP 2008-254400 A JP 2002-36833 A JP 2007-320540 A JP 2009-51418 A

  This invention makes it a subject to suppress generation | occurrence | production of the big air pocket at the time of affixing a carcass ply.

As a means for solving the above problems, the present invention provides:
A pneumatic tire provided with a carcass ply that is folded and pasted from the inside to the outside at a bead portion and has a coating layer at a tip portion,
The front edge of the coating layer is constituted by a displacement portion that repeats three or more depressions and bulges formed by increasing or decreasing in the tire radial direction.

  With this configuration, it is possible to suppress the occurrence of a large air pocket when the coating layer is applied. That is, since the tip edge of the carcass ply is composed of a displacement portion that repeats the dent and the bulge, if the folded portion is pasted from the bead side while rotating the carcass ply, the pasting force is It acts alternately on the one-layer part where the dent part does not overlap and on the two-layer part where the bulge part overlaps. Therefore, unlike the conventional case, there is no occurrence of a large air pocket when the step is moved from the two-layer portion where the carcass ply overlaps to the one-layer portion where the carcass ply does not overlap. That is, air does not stay at one place and can be dispersed at a plurality of places.

  The tip edge constituted by the dent and bulge of the displacement part may be a sin waveform.

  It is preferable that the hollow portion is constituted by an auxiliary displacement portion that repeats an auxiliary hollow portion and an auxiliary bulge portion, which are formed by increasing or decreasing in the tire radial direction with a displacement amount smaller than that of the displacement portion.

  With this configuration, even if air is concentrated and mixed in the hollow portion, it can be dispersed by the auxiliary displacement portion. Even if air is mixed, the displacement amount of the auxiliary displacement portion is small, so that the mixed air can be dispersed.

  It is preferable that the dents and the bulges of the displacement part are arranged out of phase on both sides in the tire width direction.

  With this configuration, the mass balance in the tire circumferential direction does not become uneven on both sides, and so-called uniformity can be improved.

  In this case, it is preferable that the hollow portion and the bulging portion of the displacement portion are arranged so as to be in opposite phases on both sides in the tire width direction.

Further, the present invention provides a means for solving the above-described problems,
A pneumatic tire manufacturing method,
On the leading edge of the carcass ply, a displacement portion that increases or decreases in the distal direction and repeats the hollow portion and the bulging portion three or more times is formed,
Fold the carcass ply from inside to outside at the bead,
The folded portion of the carcass ply is formed by sticking from the bead portion side to form a coating layer.

  According to the present invention, since the displacement portion is formed at the front end edge of the carcass ply, the air pool does not concentrate at one place when pasting, and can be dispersed at a plurality of places. Therefore, it is possible to prevent the occurrence of a problem that a large air pocket is formed and the product is defective.

It is a fragmentary sectional view in the meridian surface of the tire concerning this embodiment. (A) is a fragmentary sectional view containing the coating layer of the front-end | tip part of the carcass ply of FIG. 1, (b) is a fragmentary sectional view which shows the state before sticking a coating layer. (A) is a schematic front view of the tire which concerns on the comparative example 2, (b) is a graph which shows the distribution state of the both-ends edge of the carcass ply. (A) is a schematic front view of the tire which concerns on Example 1, (b) is a graph which shows the distribution state of the both-ends edge of the carcass ply. 6 is a graph showing a distribution state of both end edges of a carcass ply of a tire according to Example 2; 7 is a graph showing a distribution state of both end edges of a carcass ply of a tire according to Example 3. 6 is a graph showing a distribution state of both end edges of a carcass ply of a tire according to Example 4; It is a schematic explanatory drawing which shows the detail of the front end edge of the bead filler which concerns on this embodiment.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In the following description, terms indicating specific directions and positions (for example, terms including “up”, “down”, “side”, “end”) are used as necessary. Is for facilitating understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of these terms. Further, the following description is merely illustrative in nature and is not intended to limit the present invention, its application, or its use.

  FIG. 1 is a partial cross-sectional view of the pneumatic tire according to this embodiment on the meridian surface. In this pneumatic tire, the external structure includes a tread portion 1, a shoulder portion 2, a side portion 3 and a bead portion 4. The internal structure includes a belt 5 provided from the tread portion 1 to the shoulder portion 2. A reinforcing carcass ply 6 is provided on the outer peripheral side of the belt 5. A carcass ply 7 is provided on the inner peripheral side of the belt 5. The carcass ply 7 is directed from the tread portion 1 to the bead portion 4 and is turned back by the bead core 8 incorporated therein to reach the outer surface side. In FIG. 1, the other members are omitted.

  As shown in FIG. 2, the carcass ply 7 is formed into a sheet shape by arranging a plurality of metal wires 7a in parallel and covering the whole with a rubber layer 7b made of a rubber material. Both end edges of the folded portion of the carcass ply 7 form a covering layer 9 composed only of a rubber layer 7b extending from the end of the wire 7a to the tip.

  One surface of the coating layer 9 gradually approaches the other surface as it goes toward the front edge. That is, it has a substantially triangular cross section in which the thickness of the covering layer 9 attached thereto is gradually reduced toward the outer surface 7 c of the carcass ply 7. For this reason, almost no step is formed between the leading edge of the covering layer 9 and the outer surface 7c of the carcass ply 7.

  The leading edge of the covering layer 9 increases or decreases toward the leading edge. Thereby, the displacement part 12 which repeats the hollow part 10 hollowed inward from the front end side and the swelling part 11 swollen to the front end side is formed in the front-end edge of the coating layer 9.

  Here, the displacement part 12 consists of a sin waveform of 3 cycles or more, and the amplitude is set in the range of 30 to 70%, preferably 30 to 50% with respect to the width of the coating layer 9 (dimension in the tire radial direction). Yes. However, since the sin waveform in this case is formed on the circumference, it is expressed by the following equation using polar coordinates.

a：半径、ｂ：振幅、n：周期

a: radius, b: amplitude, n: period

  Further, the shape of the tip edge of the displacement portion 12 is formed so that the phase is shifted at both edges. In other words, the other sin waveform is opposite in phase to the other sin waveform. However, this phase shift is preferably ± 20% or less with respect to the ½ cycle, preferably ± 10% or less, and most preferably ± 5% or less.

  In addition, as shown in FIG. 8, an auxiliary displacement portion 15 that repeats an auxiliary dent portion 13 that dents inward from the edge and an auxiliary bulge portion 14 that swells outward is formed in the dent portion 10. The amplitude of the auxiliary displacement portion 15 is set to a value smaller than the amplitude of the displacement portion 12.

  Next, the manufacturing method of the pneumatic tire which consists of the said structure is demonstrated. Here, only the method for forming the carcass ply 7 which is a characteristic part of the present invention will be described.

  First, the both ends of the carcass ply 7 are folded at the bead portions 4 provided on both sides, and the two ends of the carcass ply 7 are overlapped to form two layers. Then, the overlapping surfaces are adhered to each other by pressing a stitcher (not shown) against the folded portion from the side while rotating the parts being formed in the circumferential direction.

  In the pressing of the stitcher, since the displacement portion 12 is formed at the leading edge of the folded portion, the stitcher alternately passes through the first layer portion formed in the hollow portion 10 and the second layer portion formed in the bulging portion 11. To do. That is, if the leading edge is located on the same circumference as in the conventional carcass ply 7, the stitcher passes through only one location, and the air pocket is concentrated at that location and becomes large. However, if it is the said displacement part 12, a stitcher moves a level | step difference in multiple places from a 1st layer part to a 2nd layer part, or a 2nd layer part to a 1st layer part. Since the tip edge has a sin wave shape, air can escape to the bulging portion side when passing through the step. Moreover, the auxiliary displacement portion 15 is formed in the recess portion 10, and the air pockets can be further finely dispersed. Accordingly, it is difficult for air pockets to occur in the molded tire, and the generated air pockets can be removed by post-processing as small ones that do not cause product defects.

Here, a comparative experiment was performed on the performance of the tire having the above-described configuration.
That is, as shown in Comparative Examples 1 and 2 and Examples 1 to 5, the performances of tires obtained after molding by variously changing the shape of the front edge of the carcass ply 7 of the green tire were compared. The comparison results are shown in Table 1.

Here, the shape indicates the shape of both end edges of the carcass ply 7. Here, there are examples of those located on the same circumference and those having a sin waveform.
The period indicates a period in one rotation in the tire circumferential direction when both end edges of the carcass ply 7 have a sin waveform.
The amplitude means the amplitude of the sin waveform.
As for the initial phase shift, the phase shift amount corresponding to one wavelength of the phase when both ends of the carcass ply 7 have a sin waveform is opposite to the reference position where the shift amount is 0%. It is a value set so that the same phase is obtained when the amount is 100% (1/2 period is 100%).
RFV (OAL) is obtained by indexing the radial force variation (RFV) in the tire radial direction. Here, the tire was rotated on the drum, the axial force fluctuation in the vertical direction was detected, and this was evaluated over the entire contact surface (OAL: over all). In this case, Comparative Example 1 was set as a reference value (100%), and the value was obtained. The smaller the value, the worse the performance.
The failure rate of air entry is determined based on the ratio of the number of air-filled (reserved) tires to the number of production. Those judged as “◯” indicate that the air entry defect has been reduced.

In Comparative Example 1, the leading edge of the carcass ply 7 is positioned on the same circumference (see, for example, JP 2009-254400 A).
In Comparative Example 2, as shown in FIG. 3, the tip edge of the carcass ply 7 has a sin waveform of one cycle, and the phase shift is 5% (9 °).
In Example 1, as shown in FIG. 4, the tip edge of the coating layer 9 has a three-cycle sin waveform, and the phase shift is 50% (30 °).
In the second embodiment, as shown in FIG. 6, the tip edge of the csply has a three-cycle sin waveform, and the phase shift is 100% (60 °, that is, the same phase).
In Example 3, as shown in FIG. 7, the tip edge of the coating layer 9 has a three-cycle sin waveform, and the phase shift is 5% (3 °).
In Example 4, as shown in FIG. 8, the front end edge of the coating layer 9 has a sin waveform of 5 cycles, and the phase shift is 5% (1.8 °).
In Example 5, the tip edge of the coating layer 9 has a three-cycle sin waveform, and the phase shift is 20% (12 °).

  As is apparent from Table 1, in any of Examples 1 to 5, by setting the sine wave period to 3 cycles or more, there is no deterioration of the fluctuation force in the tire radial direction, and the incidence of defective air entry can be reduced. did it.

  In addition, this invention is not limited to the structure described in the said embodiment, A various change is possible.

  In the embodiment, the tip edge of the covering layer 9, that is, the shape of the displacement portion 12 is a sin waveform, but any shape may be adopted as long as the shape increases or decreases in the tip direction, such as a zigzag shape. Is possible. This shape is the same even in the auxiliary displacement portion 15.

  The present invention can be applied to pneumatic tires, particularly pneumatic tires for heavy loads such as trucks and buses.

DESCRIPTION OF SYMBOLS 1 ... Tread part 2 ... Shoulder part 3 ... Side part 4 ... Bead part 5 ... Belt 6 ... Reinforcement carcass ply 7 ... Carcass ply 8 ... Bead core 9 ... Covering layer 10 ... Depression part 11 ... Swelling part 12 ... Displacement part 13 ... Auxiliary Recess 14: Auxiliary bulge 15 ... Auxiliary displacement

Claims (6)

A pneumatic tire provided with a carcass ply that is folded and pasted from the inside to the outside at a bead portion and has a coating layer at a tip portion,
The pneumatic tire according to claim 1, wherein the front end edge of the covering layer is constituted by a displacement portion that repeats three or more depressions and bulges formed by increasing or decreasing in the tire radial direction.   2. The pneumatic tire according to claim 1, wherein a front end edge constituted by a hollow portion and a bulging portion of the displacement portion has a sin waveform.   The said hollow part was comprised by the auxiliary | assistant displacement part which repeats an auxiliary | assistant hollow part and an auxiliary bulge part formed by increasing / decreasing in a tire radial direction by the displacement amount smaller than the said displacement part. Or the pneumatic tire of 2.   The pneumatic tire according to any one of claims 1 to 3, wherein the hollow portion and the bulging portion of the displacement portion are arranged with phases shifted on both sides in the tire width direction.   The pneumatic tire according to claim 4, wherein the hollow portion and the bulging portion of the displacement portion are arranged so as to be in opposite phases on both sides in the tire width direction. On the leading edge of the carcass ply, a displacement portion that increases or decreases in the distal direction and repeats the hollow portion and the bulging portion three or more times is formed,
Fold the carcass ply from inside to outside at the bead,
A method for producing a pneumatic tire, comprising forming a coating layer by attaching the folded portion of the carcass ply from the bead portion side.

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