JPH0571007B2 - - Google Patents

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 used for manufacturing a pneumatic tire, particularly a radial tire for heavy vehicles. [Prior Art] Generally, radial tires are made by combining a bead part, a sidewall part, a carcass, and other components on a forming drum, and attaching a belt and tread rubber to a toroid-shaped body made by bulging these parts. After forming a green cover tire, the green cover tire is manufactured by vulcanizing it in a vulcanization mold, or by forming a predetermined pattern on the tread part by using unevenness formed in the vulcanization mold in advance. It forms a tread groove. [Problems to be Solved by the Invention] However, the tread pattern of the tread portion of the vulcanization mold is not a simple shape;
In order to facilitate removal after vulcanization, the mold is divided into a plurality of split molds.
As a result, the cost of the mold is high, the mechanism of the vulcanizer is complicated, the price is high, and a great deal of effort and care is required for removal and operation. 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 a tread pattern is formed on the tread surface. As shown in Fig. 4, as the unvulcanized rubber flows into the groove G of the mold, belt B is partially pushed up, and as a result, belt B has a wavy undulation. Cheap. This undulation also impairs the uniformity of the tire 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 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 that is arranged on the outside of the carcass in the radial direction. After affixing a vulcanized or semi-vulcanized tread rubber sheet with a recessed tread pattern to an unvulcanized toroid-shaped raw cover base tire containing the above, directly or via cushion rubber, This is a method for manufacturing a pneumatic tire characterized by vulcanization in a vulcanization mold. [Function] In this way, since the tread pattern is formed on the tread rubber sheet in advance and the sheet is vulcanized, a plain mold without a pattern can be used for the mold, and it is possible to use the conventional tread groove shape. It is possible to use a two-piece mold that is the cheapest and easiest to operate, instead of an expensive split mold that is divided into pieces, thereby improving economic efficiency. Furthermore, in heavy vehicle tires, the tread area is thick, thus greatly reducing the long vulcanization times normally required for vulcanizing this area, thereby increasing productivity. In addition, it is possible to reduce belt waving and undulation caused by raw rubber flowing into the grooves for forming the tread of the mold, to make the tread rubber thickness uniform, and to improve wear resistance. [Example] An example 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 attaching and integrating a pre-vulcanized tread rubber sheet 3 to a toroidal raw cover base tire 2 via a cushion rubber 4. After that, it is vulcanized in a vulcanization mold, and the raw cover base tire 2 has a bead portion 6 having a pair of left and right bead cores 5, and a sidewall portion extending radially outward from the bead portion 6. 7, and the necessary tire constituent members such as the carcass 8, which is neglected by folding both ends around the bead core 5, are stacked on a forming drum and bulged in a toroidal shape, and then a non-stretchable cord is used. A belt 9 etc. consisting of a plurality of plies are arranged, and the rubber of each part forming the raw cover base tire 2 is all unvulcanized rubber, so the base tire 2 is substantially unvulcanized. formed into a state. The cushion rubber 4 is made of an unvulcanized rubber composition such as natural rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, alone or in a mixture, similar to those used in the production of conventional retreaded tires. 0.5-3mm, preferably
It is formed into a sheet shape of about 1.5mm. Further, the treaded 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 vulcanization here means 100% In addition to vulcanization, it has a hardness that can maintain the shape of the tread pattern even when subjected to pressure during subsequent vulcanization, including an incomplete semi-vulcanized state of, for example, about 80% or more. ,
Sheets used for the production of conventional retreaded tires can be reused. The inner surface 3a of the treaded rubber sheet 3 is buffed or coated with 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 disposed astride between the tread rubber sheet 3 and the sidewall portion 7. is preferable, and at this time, the side surface 3b of the treaded rubber sheet 3 is also buffed together with the upper part of the sidewall portion 7. The shoulder rubber 10 used has a rubber hardness after vulcanization that is equal to or higher than that of the rubber of the sidewall portion 7, and which is lower than the vulcanized hardness of the shoulder rubber sheet 3. The assembled tire T in which the tread rubber sheet 3 is bonded to such a green 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. Therefore, the tread rubber sheet 3 is bonded to the base tire 2 by vulcanizing the cushion rubber 4 by placing it in a two-piece plain mold that can only be divided into two parts left and right or top and bottom, and performing a predetermined vulcanization process. A tire 1 is formed. Note that when semi-vulcanized rubber that can be bonded to the base tire 2 by vulcanization is used as the tread rubber sheet 3, the sheet 3 can be attached directly to the base tire 2 without using the cushion rubber 4. [Example] Tire size 10.00R20 14PR and 1st and 2nd
The results of trial manufacturing of truck and bus tires having the tread pattern 12 shown in the figure and shown in FIG. 3 by the method of the present invention are shown in Table 1 in comparison with the conventional method. From Table 1, the method of the present invention has a low mold manufacturing cost.

[Table] A Tsudo pattern was formed.
It also improves uniformity, eliminates belt undulation, and improves wear resistance. Wear resistance was measured by attaching it to the rear axle of an 11-ton road truck and measuring the remaining grooves after traveling 80,000 km.
It is expressed as an index of 100. The larger the number, the better the wear resistance. [Effects of the Invention] As described above, since the tread pattern is formed and vulcanized in advance on the tread rubber sheet, the mold is a plain mold without a pattern, and the same tread pattern is formed regardless of the shape difference. It becomes possible to use a two-piece mold, increasing economic efficiency. In addition, the time required for vulcanization of the thick tread portion is greatly reduced, increasing productivity, and reducing belt undulations and undulations caused by raw rubber flowing into the mold grooves, reducing the tread rubber thickness. This makes it possible to make the wear resistance uniform, and to obtain wear resistance equivalent to that of the pre-cured tread of a so-called retreaded tire.

[Brief explanation of drawings]

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 illustrating a tread pattern, and FIG. 4 is a sectional view illustrating a conventional tire. 2... raw cover base tire, 3... treaded rubber sheet, 4... cushion rubber, 5... bead core, 6... bead part, 7... side wall part,
8...Carcass, 9...Belt layer, 10...Shoulder rubber.

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. A vulcanized or semi-vulcanized tread rubber sheet with a recessed tread pattern is placed on the cover base tire.
A method for manufacturing a pneumatic tire, which comprises applying the adhesive directly or through a cushion and then vulcanizing it in a vulcanization mold.