JPH0272910A - Manufacture of pneumatic tire - Google Patents

Abstract

PURPOSE:To improve economy by enabling use of a two-piece mold, by a method wherein a tread pattern is formed beforehand on a tread rubber sheet and vulcanization is performed. CONSTITUTION:After formation of an assembled tire T, the same is vulcanized within a vulcanizing mold by sticking a tread rubber sheet 3 vulcanized beforehand to a toroidal green cover base tire 2 through cushion rubber 4 for unification. Since a tread pattern is formed beforehand in the assembled tire T, a tread face of a mold is flat Therefore, the tire T is arranged within a two piece plain mold which is dividable into only two laterally or vertically, the tread rubber sheet 3 is joined to the base tire 2 through vulcanization of the cushion rubber 4 and a tire 1 is formed. In addition, in the case where semi- vulcanised rubber, which is joinable to the base tire 2 through the vulcanization, is used as the tread rubber sheet 3, the sheet 3 can be attached directly to the base tire 2 without making use of the cushion rubber 4.

Description

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

(Prior art) Generally, radial tires are made by combining other components such as a bead, a sidewall, and a carcass on a forming drum, and then attaching a belt and tread rubber to a toroid-shaped body made by expanding these components. In addition, the raw cover tire is manufactured by vulcanizing the raw cover tire in a vulcanization mold, or by forming a predetermined pattern on the tread by using unevenness formed in the vulcanization mold in advance. Forms tread grooves.

[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 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 raw 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 a tread pattern is formed on the tread surface as shown in FIG. As shown in Fig. 2, the belt B is partially pushed up as the unvulcanized rubber flows into the groove G of the mold, and as a result, the belt B tends to have wavy undulations. Undulation impairs tire uniformity and induces tread tear.

The object of the present invention is to provide a method for manufacturing a pneumatic tire that enables vulcanization in a two-piece mold that is inexpensive and easy to operate, thereby increasing productivity and also reducing waving of the breaker.

[Means for solving problems]

The present invention is an unvulcanized toroid 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 arranged radially outside the carcass. A tread rubber sheet with a recessed tread pattern and a vulcanized or semi-vulcanized tread rubber sheet is attached directly or via cushion rubber to a raw cover base tire of the shape of the tire, and then vulcanized in a vulcanization mold. This is a method of manufacturing a pneumatic tire.

[Effect]

In this way, since the tread rubber sheet has a tread pattern formed in advance and the sheet is vulcanized, a plain mold without a pattern can be used as the mold, and moreover, it does not require the conventional expensive method of dividing the sheet according to the tread groove shape. It is possible to use a two-piece mold, which is the cheapest and easiest to operate, instead of a two-piece mold, improving economic efficiency. Furthermore, heavy vehicle tires have thick tread sections, thus greatly reducing the long vulcanization times normally required to vulcanize these sections, thereby increasing productivity. In addition, it is possible to reduce belt waving and undulation caused by raw rubber flowing into the tread-forming grooves of the mold, to make the tread rubber thickness uniform, and to improve wear resistance.

〔Example〕

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

1 to 3, the manufacturing method of the present invention forms an assembled tire T by pasting and integrating a pre-vulcanized tread rubber sheet 3 onto a toroidal raw cover base tire 2 via a cushion rubber 4. After that, the raw cover base tire 2 is vulcanized in a vulcanization mold. Necessary tire constituent members such as a carcass 8, which includes a wall portion 7 and is secured by folding both ends around the bead core 5, are laminated on a forming drum and swelled into a toroidal shape, and are non-stretchable. A belt 9 made of a plurality of braais using cords is arranged, and the rubber of each part forming the raw cover base tire 2 is all unvulcanized rubber, so that the base tire 2 is substantially Formed in an unvulcanized state.

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. Sa0.
5 to 3 females, preferably formed into a sheet shape of about 1.5 m.

Further, the tread rubber sheet 3 is a long sheet-like body having a desired tread pattern recessed on its outer surface by being vulcanized in advance in a press mold, and here, vulcanization refers to
In addition to 100% vulcanization, an incomplete semi-vulcanized state of, for example, 80% or more, is hard enough to maintain the shape of the tread pattern even when subjected to pressure during subsequent vulcanization. The sheets used for manufacturing conventional retreaded tires can be reused.

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

Further, as shown in FIG. 1, in order to prevent the tread rubber sheet 3 from peeling off at the side, a shoulder rubber 10 is preferably disposed astride between the tread rubber sheet 3 and the sidewall portion 7. At this time, the side surface 3b of the tread rubber sheet 3 is also given a puff finish along with the upper part of the sidewall portion 7.The shoulder rubber lO has a rubber hardness equal to or higher than that of the rubber of the sidewall portion 7 after vulcanization. Moreover, a rubber sheet having a hardness lower than the vulcanization hardness of the tread rubber sheet 3 is used.

The assembled tire T in which the tread rubber sheet 3 is bonded to such a raw cover base tire 2 via the cushion rubber 4 has a tread pattern formed in advance, so the tread surface of the mold is flat, and therefore 2 left and right or up and down
The tire 1 is formed by placing the tread rubber sheet 3 on the base tire 2 by vulcanizing the cushion rubber 4 by vulcanizing the cushion rubber 4 by placing it in a two-piece plain mold that can only be divided into two parts, and performing a predetermined vulcanization. In addition, tread rubber sheet 3
When using semi-vulcanized rubber that can be joined to the base tire 2 by vulcanization, the sheet 3 can be directly attached to the tire 2 without using the cushion rubber 4.

〔Example〕

The tire size is 10.0OR2014PR and the 1st.
Table 1 shows the results of trial manufacturing of truck and bus tires shown in FIG. 2 and having the tread pattern 12 of FIG. 3 by the method of the present invention, in comparison with the conventional method.

As shown in Table 1, the method of the present invention has a low mold production cost.

It also improves uniformity, eliminates belt undulations, and improves wear resistance.

The wear resistance is measured by attaching the tire to the rear wheel of an 11-ton road truck and measuring the remaining groove after driving 80,000 miles, and expressing it as an index with the conventional example being 100. The larger the number, the better the wear resistance.

〔Effect of the invention〕

In this way, the tread rubber sheet has a tread pattern formed in advance and is vulcanized, so it is possible to use a plain mold without a pattern as the mold, and even the same two-piece mold regardless of the difference in the shape of the tread pattern. Improve economy.

In addition, the time required for vulcanization of thick tread parts is greatly reduced, increasing productivity, and eliminating belt undulations and undulations caused by raw rubber flowing into mold grooves. It evens out the tread and provides wear resistance equivalent to that of the so-called precure tread of retreaded tires.

[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, and FIG. 3 is a plan view illustrating a tread pattern.
FIG. 4 is a cross-sectional view illustrating a conventional tire. 2- Raw cover base tire, 3- Tread rubber sheet, 4- Cushion rubber, 5- Bead core, 6...Bead part, 7--Side wall part, 8--Carcass, 9 -Belt layer, 10-...Shoulder rubber. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Seifuezu Naemura

Claims (1)

[Claims] 1 An unvulcanized toroidal raw material comprising a pair of left and right ped cores, a carcass that is secured by folding both ends around the cores, and a belt made of a non-stretchable cord arranged radially outside of the carcass. A tread rubber sheet with a recessed tread pattern and a vulcanized or semi-vulcanized tread rubber sheet is attached to a cover base tire directly or via cushion rubber, and then vulcanized in a vulcanization mold. A method of manufacturing tires.