JPS61273937A - Preparation of pneumatic tire having deep-grooved lug - Google Patents

Abstract

PURPOSE:To avoid efficiently the surface cracking of a tread, by forming scooped parts in the rubber layer for the tread of a green tire, where the layer is confronting to the convex part of mold surface served for the formation of deep transverse grooves. CONSTITUTION:When the required tread pattern is obtained by the flow of rubber at the time of molding and curing of green tire 1, scooped parts 2 whose depth are equivalent to 20-100% of the depth of tranverse grooves of the tire after molding and curing are formed per each area of deep transverse grooves 3 dividing lugs of rubber layer mounted on the green tire 1. The mold ing and curing of the green tire is carried out after positioning the portion between adjacent scooped parts at the lug cavity of mold for curing. As the sideway press against the rubber layer is extremely decreased, it is possible to avoid efficiently the surface cracking of tread, which is caused by the intru sion accompanied with the rubber flow of mold-releasing agent applied previous ly on the surface of the rubber layer.

Description

[Detailed description of the invention] (Industrial application field) For use as a reduced vehicle for construction and civil engineering work.

Pneumatic tires provided exclusively with
In this specification, a tread pattern with deep groove lugs in which lugs intermittent on the periphery are divided by relatively deep lateral grooves is suitable; in this specification, this type of tread pattern is
The following describes the results of research and development on how to form a green tire neatly without molding defects by inducing a particularly advantageous and appropriate rubber flow during the vulcanization molding stage of a green tire. (Prior technology) Pneumatic tires with deep groove lugs, including flat tires with low aspect ratios, can be molded into green tires by applying the so-called full mold method using a two-piece vulcanization mold. For example, when vulcanization is performed, surface cracks in the tread may occur.
The appearance of vulcanized products tends to deteriorate frequently due to

゛ (Problem to be solved by the invention) In the above full mold method, during the inflation and expansion process of the green tire loaded in the vulcanization mold,
The two halves of the vulcanization mold are closed together, and at this time, the rubber layer that is to form the tread of the green tire is held together by the convex part of the mold surface of the vulcanization mold that forms the lateral grooves. As the rubber layer is locally pressed in the same direction, the release agent layer previously applied to the surface of the rubber layer thickens under the influence of the pressure, gets caught up in the rubber flow, and creates wrinkle-like bites, making it difficult to form the tire. After vulcanization, the tread surface tends to crack.

Of course, there is no possibility that such disadvantages can be prevented by the so-called shaving control, which delays the swelling and expansion process in the green tire vulcanization mold described above until the completion of closing of the vulcanization mold. However, at this time, the lower shaving pressure causes a difference in the inflation shape of the upper and lower molds due to the weight of the green tire, which may lead to quality deterioration such as unevenness of the upper and lower molds of the product after vulcanization, and the time required for vulcanization. This leads to another problem in which productivity deteriorates.

It is an object of the present invention to provide a method for manufacturing a pneumatic tire with deep groove lugs that includes an advantageous process for effectively avoiding such surface cracking.
This is the object of this invention.

(Means for Solving the Problems) This invention provides a cylindrical case obtained by pasting together case members, and around the cylindrical case, lugs that are interrupted at least at the shoulder portion of the tire are defined by relatively deep lateral grooves. Then, a green tire is made by pasting a rubber layer that is compatible with the molding of the green tire, and when a predetermined tread pattern is obtained by rubber flow during molding and vulcanization of this green tire, the rubber layer that is pasted on the green tire is For each of the formation areas of the deep lateral grooves that partition the lugs, 2 of the lateral groove depth in the tire after molding and vulcanization.
Deep grooved air with deep groove lugs is formed by forming gouges at a depth equivalent to 0 to 100%, positioning the adjacent gouges in the lug cavities of a vulcanization mold, and performing molding and vulcanization of the green tire. This is the manufacturing method for tires.

Here, it is more preferable in practice to make the gouge have a larger width and length than the lateral groove in the tire after molding and vulcanization. In this invention, the cylindrical case is oriented parallel to its axis. Wrap and laminate the required number of plies of rubberized parallel hood layers onto a substantially flat 7 ohmer.
Next, the process goes through the process of adapting the bead core, folding the ply inward around it, and pasting it.At this time, in the case of a so-called radial carcass structure in which the cord direction of the ply extends almost within the radial plane of the tire, In the case of a bias carcass structure in which toroidal deformation is preceded and multiple plies are laminated at cord angles that intersect with each other, prior to toroidal deformation, a belt or breaker surrounding the carcass - □ Reinforcements such as these are wrapped with a rubber layer consisting of a composite rubber band called orbillet, which is arranged to meet the required performance of the tread. There is no difference from the conventional method through the steps of making green tires by attaching and bonding them together.

Now, in FIG. 1, the green tire prepared as described above is indicated by the number 1, 2 is a tire to which a hollow according to the present invention is applied, and 8 is an imaginary lateral groove in the product tire.

The gouge 2 has a depth shown by H in the A-A and B-B cross sections, but the depth H needs to be equal to or less than the depth of the lateral groove 8d, and at least 20% or more.

The width and length of the hollow are both made larger than those of the horizontal groove 8. As expected, it is advantageous to increase the degree of curvature as the depth becomes shallower.

(Function) According to the present invention, by forming the hollow 2 in the part of the rubber layer for the tread of a green tire that faces the convex part of the mold surface used for forming deep lateral grooves, the vulcanization mold can be formed. Closing operation process: At the ゛□ step,
Since the lateral pressure on the rubber layer is significantly reduced, cracking of the surface of the tread due to biting of the release agent previously applied to the surface of the rubber layer accompanying the flow of the rubber is advantageously avoided. ... Here, regarding the behavior of the mold release agent,
2nd: Figure 8 shows the appearance of surface cracks that occurred on the tread of a pneumatic tire with deep groove lugs.

Ql ゛ Drawing 4 is the mold for vulcanization, 6 is the green tire, 6 is the mold surface, flag is the lug cavity, 8 is the mold surface convexity that governs the formation of the horizontal grooves, 9 is the mold release agent layer, IO is the 11 is a surface crack.

'□゛・ (Example): , □ , When manufacturing a pneumatic tire for construction work with a tire size of OR84576B-45, a gouge as shown in Figure 1 was made in the shoulder part of the green tire. 1. The relationship between the depth of gouge 2 and surface cracking in the tread of a manufactured tire was investigated when z was varied and its width and length were set to be slightly larger than that of the lateral groove. Table 1 shows the results. It was shown to.

,'1゛ Table 1 1・

[Brief explanation of drawings]

Figure 1 is a front view of a green tire with a gouge, B m i2'') -> fi4 'r (F
)% - 4-stage internal device, 3-stage local deformation behavior explanatory diagram.
1 and 8 are explanatory diagrams of tread forming defects.
'(・艷A-AM side E B-BWrt4J
Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. For forming a tread around a cylindrical case obtained by bonding case members together, in which lugs that are intermittent on the circumference at least at the shoulder portion of the tire are partitioned by relatively deep lateral grooves. A green tire is made by attaching a compatible rubber layer, and when a predetermined tread pattern is obtained by the rubber flow of the rubber layer during molding and vulcanization of the green tire, the above rubber layer is attached to the green tire. For each of the deep lateral groove formation regions that partition the lugs, the layer has a depth of 20 to 20% of the lateral groove depth in the tire after molding and vulcanization.
With deep groove lugs, the green tire is molded and vulcanized by forming a gouge with a depth equivalent to 100%, and positioning the adjacent spaces between the gouges in a lug cavity of a vulcanization mold. Manufacturing method for pneumatic tires. 2. The method according to 1, wherein the gouge is made to have a larger width and length than the lateral groove in the tire after molding and vulcanization.