JPH0671771B2 - Pneumatic tire manufacturing method - Google Patents

Description

TECHNICAL 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, in a radial tire, a belt and a tread rubber are attached to a toroidal body obtained by combining other components such as a bead side wall and a carcass on a molding drum and swelling the components. After forming a green cover tire by, the green cover tire is manufactured by vulcanizing in a vulcanizing mold, or by the unevenness preformed in the vulcanizing mold, the tread of a predetermined pattern on the tread portion. Forming a groove.

[Problems to be Solved by the Invention]

However, since the tread pattern of the tread portion is not a simple shape, the vulcanization mold is formed as a split mold in which the mold is divided into a plurality of pieces in order to facilitate removal after vulcanization. . As a result, the mold cost is high,
Further, the mechanism of the vulcanizer becomes complicated and the price becomes high, and the unloading operation requires a lot of trouble and attention.

Further, in the conventional manufacturing method, when the tread surface of the raw cover tire is pressed against the inner surface of the mold by the compressive force acting from the inside of the tire during the vulcanization step to form a tread pattern on the tread surface, FIG. As shown in (4), the belt B is partially pushed up as the unvulcanized rubber mold flows into the groove G, and as a result, the belt B is likely to have a wavy undulation. Also, this undulation impairs the uniformity of the tire and induces tread breakage.

In order to solve some of these problems, the applicant has filed Japanese Patent Application No. 63
-In No. 227064, a belt-shaped tread rubber sheet having a tread pattern recessed and vulcanized is wound around the peripheral surface of a raw cover stand tire including a carcass and a belt, and then the whole is vulcanized. Therefore, a method of manufacturing a tire was proposed.

However, in the above proposal, waviness occurs in the tire circumferential direction when the tread rubber sheet is attached, and the quality becomes unstable such that the rubber thickness becomes uneven at the joint,
Reduces handling and riding comfort.

INDUSTRIAL APPLICABILITY The present invention enables vulcanization in a two-piece mold which is inexpensive and easy to operate, and enhances productivity, and also reduces waviness of the breaker and forms a tread portion having a uniform thickness, thereby improving steering stability and riding comfort. The object of the present invention is to provide a method for manufacturing a pneumatic tire that can improve comfort and improve tire performance.

[Means for solving problems]

The present invention includes a pair of left and right bead cores, a carcass around which both ends are folded and locked, and a belt made of a non-stretchable cord arranged radially outside the carcass and which is in an unvulcanized state. On the raw cover stand tire,
It is characterized in that the tire base is formed in advance in an annular shape, and the tire base body on which the vulcanized or semi-vulcanized tread rubber ring in which the tread pattern is recessed on the peripheral surface thereof is inserted is vulcanized in a vulcanization mold The method for producing a pneumatic tire is as follows.

[Action]

As described above, since the tread pattern is formed in advance on the tread rubber ring and the ring is vulcanized, the mold for vulcanizing the tire base can use a plain mold without a pattern, and the conventional tread groove shape can be used. It is possible to use the cheapest and easiest-to-use 2-piece two-piece mold instead of the expensive split mold that is divided according to
Improve economic efficiency. Further, even when the tread portion is thick as in a heavy vehicle tire, the long vulcanization time normally required for vulcanizing the tread portion is greatly reduced, and the productivity is improved.
Also, the waviness and undulation of the belt due to the inflow of raw rubber into the groove for forming the tread pattern of the vulcanization mold is reduced, and the tread ring is preliminarily formed into an annular shape, so the rubber thickness of the tread layer can be made uniform. In addition, wear resistance and durability can be further improved, and riding comfort and steering stability can be improved.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 to 4, in the manufacturing method of the present invention, a tread rubber ring 3 which has been vulcanized in advance is externally attached to and integrated with a toroidal raw cover tire 2 to form a tire base T, and then a vulcanized gold is used. The vulcanization is performed in a mold, and the green cover base tire 2 includes a bead portion 6 having a pair of left and right bead cores 5, and a side wall portion 7 extending outward from the bead portion 6 in a radial direction, and Necessary tire constituent members such as a carcass 8 which is folded around both ends around the bead core 5 and locked are laminated on a molding drum and swelled in a toroidal shape, and a plurality of plies using non-stretchable cords. Belts, etc. made of
Since the unvulcanized rubber is used for all the rubber of each part forming the base tire 2, the base tire 2 is substantially formed in an unvulcanized state.

In the present embodiment, the tread rubber ring 3 is attached to the raw cover base tire 2 via the 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 or the like, which is unvulcanized and has a thickness similar to that used for manufacturing a conventional retreaded tire. 0.5-3m
It is formed in a sheet shape of m, preferably about 1.5 mm.

The tread rubber ring 3 is formed by injection molding a rubber material using an injection mold A as shown in FIG. For example, the tread pattern 12 shown in the development view in FIG. 3 is engraved, and the tread pattern 12 is placed on the outer periphery of the press die B, which is schematically shown in FIG. 4 (b), and is vulcanized and pressed. It is possible to form a tread ring 3 which is patterned and has a seamless annular shape. Here, vulcanization means not only 100% vulcanization, but also hardness such that the tread pattern can retain its shape even when pressure is applied during subsequent vulcanization, for example, about 80% or more. Including a fully semi-vulcanized state.

As shown in FIG. 5, the tread rubber ring 3 has a tread pattern 12 formed on the outer peripheral surface at the time of injection molding by forming a tread groove for forming a tread pattern in an injection mold A1 used for the molding. It is also possible to manufacture the unvulcanized tread rubber ring 3A, and to manufacture the vulcanized tread rubber ring 3 by vulcanizing the unvulcanized tread rubber ring 3A as it is.

Further, the inner surface 3a of the tread rubber ring 3 has a cushion rubber 4
Buff or glue before sticking.

Further, in this embodiment, as shown in FIG. 1, in order to prevent peeling at the side portion of the tread rubber ring 3, a shoulder rubber 10 is disposed between the tread rubber sheet 3 and the side wall portion 7 so as to straddle it. At this time, the side surface 3b of the tread rubber sheet 3 is also buffed together with the upper portion of the side wall portion 7. This shoulder rubber
As for 10, a rubber having a rubber hardness after vulcanization that is equal to or higher than that of the rubber of the sidewall portion 7 and lower than the vulcanization hardness of the tread rubber ring 3 is used.

The tread rubber ring 3 is externally inserted through the cushion rubber 4 on such a raw cover base tire 2, and since the tread pattern is formed in advance on the tread rubber ring 3, the tread surface of the mold is flat. And therefore 1
The tread rubber ring 3 is bonded to the green cover base tire 2 by arranging it in a piece mold or a two-piece plain mold that can be divided into two parts in the left-right direction or the up-down direction, and performing predetermined vulcanization to vulcanize the cushion rubber 4. By doing so, the tire base T is formed. When the tread rubber ring 3 is a semi-vulcanized rubber that can be joined to the raw cover base tire 2, the tread rubber ring 3 can be directly attached to the raw cover base tire 2 without using the cushion rubber 4. Therefore, since the tire base body T has the uniform thickness and the seamless tread 2 is externally inserted, it is possible to improve the riding comfort and the steering stability, as well as the wear resistance and the durability.

〔Example〕

A truck and bus tire having a tire size of 10.00R20 14PR and having the tread pattern 12 shown in FIGS. 1 and 2 and having the tread pattern 12 shown in FIG. 3 was experimentally produced by the method of the present invention. Is shown in Table 1 in comparison with the method of forming a sheet by winding (comparative example).

From Table 1, the method of the present invention is low in die manufacturing cost, improves uniformity, eliminates undulation of the belt, and has high wear resistance and durability. I am

The wear resistance was measured by measuring the residual groove after it was mounted on the rear wheel of an 11 ton load truck and running 80,000 km, and the durability was 150,000 km with the 11 ton load truck whose wear resistance was measured.
The presence or absence of groove cracks at the bottom of the tread groove after running was checked. Wear resistance and durability are
It is displayed as an index with 100, and the larger the number, the better the abrasion resistance. Further, the riding comfort and the steering stability are judged by the feeling of the triber, and it is shown that the larger the numerical value indicated by the index with the conventional example being 100, the better.

〔The invention's effect〕

In this way, the tread rubber ring has an annular shape in which a tread pattern is formed in advance and is vulcanized, so that the mold is a plain mold with no pattern, and the same one-piece mold regardless of the shape difference of the tread pattern. Alternatively, it is possible to use a two-piece mold, which improves the economical efficiency. Furthermore, the time for vulcanization of the thick tread portion is greatly reduced to improve the productivity, and the waviness and undulation of the belt due to the inflow of raw rubber into the die groove are reduced, and the tread rubber thickness is reduced. In addition to being uniform and capable of preventing meandering, the tread portion has no seam, so that steering stability and riding comfort can be improved, and wear resistance and durability can be enhanced.

[Brief description of drawings]

1 is a cross-sectional view illustrating a tire manufactured according to the present invention, FIG. 2 is an exploded perspective view of the tire showing a manufacturing method of the present invention, FIG. 3 is a plan view showing an example of a tread pattern, and FIG. FIG. 4A is a sectional view schematically showing an injection mold, and FIG.
Is a cross-sectional view schematically showing a press mold, FIG. 5 is a cross-sectional view showing another example of an injection mold, and FIG. 6 is a cross-sectional view illustrating a conventional tire. 2 ... Raw cover base tire, 3 ... Tread rubber ring, 5 ... Bead core, 6 ... Bead portion, 7 ... Sidewall portion, 8 ... Carcass, 12 ... Tread pattern, T ... Tire base.

Claims (1)

[Claims] 1. A pair of left and right bead cores, a carcass having both ends folded back and locked around the bead cores, and a belt made of a non-stretchable cord arranged outside of the carcass in a radial direction and in an unvulcanized state. In a vulcanization mold, a tire base having a vulcanized or semi-vulcanized tread rubber ring formed in advance in an annular shape and having a tread pattern recessed on the outer peripheral surface is externally attached to a toroidal raw cover tire. A method for manufacturing a pneumatic tire, which comprises vulcanizing.