JPH02179731A - Manufacture of pneumatic tire - Google Patents

Abstract

PURPOSE:To contrive improvements in operational stability and comfortable riding by forming a tread part reducing surging of a breaker and having a uniform thickness, by a method wherein a tread pattern is formed beforehand on a tread rubber ring and the ring is vulcanized. CONSTITUTION:Since a tread rubber ring 3 vulcanized beforehand is outserted over a colloidal raw cover base tire 2 for unification, after formation of a tire substrate T, the same is vulcanized within a vulcanizing mold. The raw cover base tire 2 possesses a bead part 6 having a pair of a right and left bead cores 5 and a side wall part 7 extending outward of a radial direction from a bead part 6. A belt 9 comprised of a necessary tire constituent member such as a carcass 8 which is connected by folding back both ends and a plurality of plies for which a nonstretchable cord is used is arranged around the bead core 5. Since the tread rubber ring 3 is outserted over the raw cover base tire 2 like this through a cushion rubber 4 and moreover a tread pattern is formed beforehand on the tread rubber ring 3, a plain mold free from a pattern can be used for a vulcanizing mold of the tire substrate and a rubber thickness of a tread layer can be made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a pneumatic tire, which can be suitably employed in manufacturing a pneumatic tire, particularly a radial tire for heavy vehicles.

[Conventional technology]

Radial tires are manufactured by combining other components such as the bead, sidewall, and carcass on a forming drum, and attaching a belt and tread rubber to a toroid-shaped body that bulges out these parts. After forming a cover tire, the raw cover tire is manufactured by vulcanizing it in a vulcanization mold, or by forming a predetermined pattern of tread grooves on the tread part by using unevenness formed in the vulcanization mold in advance. is forming.

[Problem to be solved by the invention]

However, due to the fact that the tread pattern of the tread part is not a simple shape, the vulcanization mold is formed as a split mold in which the cough mold is divided into multiple pieces in order to facilitate removal after vulcanization. .

As a result, the cost of the mold is high, the mechanism of the vulcanizer is complicated, resulting in a high price, and the removal operation requires a great deal of effort and care.

Furthermore, in the conventional manufacturing method, the tread surface of the green cover tire is pressed against the inner surface of the mold by compressive force acting from the inside of the tire during the vulcanization process, and when a tread pattern is formed on the tread surface, as shown in FIG. As shown in the figure, as the unvulcanized rubber flows into the groove G of the mold, the belt B is partially pushed up, and as a result, the belt B tends to have wavy undulations. Unsulge contamination impairs tire uniformity and induces tread tearing.

In order to solve some of these problems, the applicant filed a patent application in 1983.
In No. 3-227064, a vulcanized band-shaped tread rubber sheet with a recessed tread pattern is wrapped around the circumferential surface of a raw cover base tire including a carcass and a belt. A method of manufacturing tires by whole vulcanization was proposed.

However, with the above-mentioned proposal, when the trend rubber sheet is attached, waving occurs in the circumferential direction of the tire, and the rubber thickness becomes uneven at the joint, resulting in unstable quality.
Decreases handling and ride comfort.

The present invention enables vulcanization in a two-piece mold that is inexpensive and easy to operate, thereby increasing productivity. It also eliminates waving of the breaker and forms a tread portion with an even thickness, thereby improving handling stability. The aim is to develop a method for manufacturing pneumatic tires that can improve ride comfort and tire performance.

[Means for Solving the Problems] The present invention provides a belt consisting of a pair of left and right bead cores, a carcass that is secured by folding both ends around the bead cores, and a non-stretchable cord arranged on the outside of the carcass in the radial direction. vulcanizing a tire base in which a tread pattern is recessed and a vulcanized or semi-vulcanized tread rubber ring previously formed in an annular shape is inserted into an unvulcanized toroid-shaped raw cover base tire comprising This is a method for manufacturing a pneumatic tire characterized by vulcanization in a sulfur mold.

[Effect]

In this way, since the tread rubber ring has a tread pattern formed in advance and the ring is vulcanized, a blank mold without a pattern can be used as the mold for vulcanizing the tire base, and it is possible to use conventional tread grooves. Instead of an expensive split mold that is divided according to the shape, it is possible to use a two-piece mold that is the cheapest and easiest to operate, improving economic efficiency. Furthermore, even when the tread portion is thick, such as in tires for heavy vehicles, the long vulcanization time normally required to vulcanize the portion can be greatly reduced, thereby increasing productivity. In addition, belt waving and undulation caused by raw rubber flowing into the grooves for forming the tread pattern in the vulcanization mold are reduced, and the tread ring is pre-molded into an annular shape, making the rubber thickness of the trend layer uniform. Furthermore, wear resistance and durability can be improved, and ride comfort and handling stability can also be improved.

〔Example] An embodiment of the present invention will be described below based on the drawings.

1 to 4, in the manufacturing method of the present invention, a tire base T is formed by extrapolating and integrating a pre-vulcanized tread rubber ring 3 onto a toroidal green cover base tire 2, and then a vulcanized rubber ring 3 is formed. The raw cover base tire 2, which is vulcanized in a mold, includes a bead portion 6 having a pair of left and right bead cores 5, and a sidewall portion 7 extending radially outward from the bead portion 6. Necessary tire components such as the carcass 8, which is secured by folding both ends around the bead core 5, are stacked on a forming drum and bulged in a toroidal shape, and then a plurality of tire components using non-stretchable cords are formed. A belt 9 made of braai is arranged, and a raw cover base tire 2 is arranged.
By using unvulcanized rubber for all the rubber parts forming the base tire 2, the base tire 2 is substantially formed in an unvulcanized state.

In this embodiment, the tread rubber ring 3 is attached to the raw cover base tire 2 via a cushion rubber 4.

The cushion rubber 4 is made of an unvulcanized rubber composition such as natural rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, etc. alone or in a mixture, similar to those used in the production of conventional retreaded tires, and has a thickness of 0. .5~
It is formed into a sheet shape of 3 trm, preferably about 1.5 m.

The tread rubber ring 3 is made by injection molding a rubber material using an injection mold A to form a continuous tread material 15 in an endless ring shape, as shown in FIG. 4(a). The tread pattern 12 as shown in the developed view in FIG. 3 is inserted into a press mold B shown schematically in FIG. The tread rubber ring 3 can be formed into a seamless annular shape having a pattern. Here, vulcanization refers to not only 100% vulcanization, but also hardness that can maintain the shape of the tread pattern even when pressurized during subsequent vulcanization.
For example, it includes an incomplete semi-vulcanized state of about 80% or more.

As shown in FIG. 5, the tread rubber ring 3 is made by forming tread grooves for forming a tread pattern on the injection mold A1 used for molding during injection molding, so that the tread pattern 12 can be formed on the outer peripheral surface. In addition to manufacturing an unvulcanized tread rubber ring 3A, a vulcanized tread rubber ring 3 can also be manufactured by vulcanizing this as it is in the transfer mold Al.

In addition, the inner surface 3a of the tread rubber ring 3 is coated with a puff or glue before the cushion rubber 4 is attached.

Furthermore, in this embodiment, in order to prevent the tread rubber ring 3 from peeling off at the side, a shoulder rubber 10 is disposed astride between the tread rubber sheet 3 and the sidewall portion 7, as shown in FIG. It is preferable to do so, and at this time, the side wall portion 7 is also formed on the side surface 3b of the tread rubber sheet 3
Apply a puff finish along with the upper part. The shoulder rubber 10 used has a rubber hardness after vulcanization equal to or higher than that of the rubber of the sidewall portion 7, and which is lower than the vulcanization hardness of the tread rubber ring 3.

The tread rubber ring 3 is inserted into the raw cover base tire 2 via the cushion rubber 4, and since the tread rubber ring 3 has a tread pattern formed in advance, the tread surface of the mold is flat. Yes, therefore 1
The tread rubber ring 3 is bonded to the green cover base tire 2 by vulcanizing the cushion rubber 4 by placing it in a piece mold or a two-piece brain mold that can be divided into two in the left and right or up and down directions, and performing a prescribed vulcanization. As a result, the tire base T is formed.

Note that when the tread rubber ring 3 is made of semi-vulcanized rubber that can be joined to the raw cover base tire 2, the tread rubber ring 3 can be attached directly to the raw cover base tire 2 without using the cushion rubber 4.

Therefore, since the tire base T has a seamless tread 2 having a uniform thickness, it is possible to improve ride comfort and steering stability, as well as improve abrasion resistance and durability.

[Example] The tire size is 10.0OR2014PR and the first tire size is 10.0OR2014PR.
The results of trial manufacturing of truck and bus tires shown in FIG. 2 and having the tread pattern 12 shown in FIG. Table 1 shows a comparison with Example).

From Table 1, the method of the present invention has low mold manufacturing costs, improves uniformity, eliminates belt undulations, and has excellent wear resistance and durability. Note 1) Vulcanization by conventional method The tread pattern shown in FIG. 3 was formed in the mold.

I'm looking forward to it.

Wear resistance was measured by attaching the tire to the rear wheel of an 11-ton line truck and measuring the remaining groove after 80,000 miles.
The occurrence of group cracks at the bottom of the tread groove after 10,000 miles of running was checked. Abrasion resistance and durability are expressed as an index with the conventional example set as 100, and a larger number indicates better abrasion resistance. Also, ride comfort and handling stability are
Judging by the driver's feeling, the conventional example was ranked 10
The larger the number expressed as 0, the better the index.

〔Effect of the invention〕

In this way, the tread rubber ring has an annular shape with a trend pattern formed in advance and is vulcanized, so the mold is a brain mold without a pattern and the same one-piece mold regardless of the shape difference of the tread pattern. Alternatively, it becomes possible to use a two-piece mold, increasing economic efficiency. In addition, it greatly reduces the time required for vulcanization of thick tread parts, increasing productivity, and reducing belt undulations and undulations caused by raw rubber flowing into mold grooves, reducing tread rubber thickness. Since the tread is seamless and there is no seam in the tread, handling stability and riding comfort can be improved, and wear resistance and durability can be increased.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating a tire manufactured according to the present invention, FIG. 2 is an exploded perspective view of the tire illustrating the manufacturing method of the present invention, FIG. 3 is a plan view showing an example of a tread pattern, and FIG. 4 (a) is a cross-sectional view schematically showing the injection mold, FIG. 4(b)
5 is a sectional view schematically showing a press mold, FIG. 5 is a sectional view showing another example of an injection mold, and FIG. 6 is a sectional view illustrating a conventional tire. 2... raw cover base tire, 3... tread rubber ring, 5...- bead core, 6...- and do section, 7... side wall section, 8-... carcass, 12... - tread pattern; T- tire base; Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura 1 Figure s3 Figure A1 Figure 5 4 (1))

Claims (1)

[Claims] 1 An unvulcanized toroid-shaped raw material that includes a pair of left and right bead cores, a carcass that is secured by folding both ends around the bead cores, and a belt made of a non-stretchable cord that is placed radially outside the carcass. An air system characterized by vulcanizing a tire base in which a tread pattern is recessed and a vulcanized or semi-vulcanized tread rubber ring previously formed in an annular shape is inserted into a cover base tire in a vulcanization mold. A method of manufacturing tires.