JPS63158235A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To eliminate product defect due to the inclusion of release agent and at improve the productivity by a method wherein a plurality of rubber sheets are arranged on the inner surface of a tire in the circumferential direction of the tire so as to form splice parts, each of which substantially runs radially by joining both the edge parts of each of these rubber sheets to one another. CONSTITUTION:In a tubular inner surface rubber sheet, splice parts 2 are formed by joining the edge parts 1e and 1e at both ends in the circumferential direction of a tire of each of a plurality of green rubber sheets 1 to one another. Due to the constitution as mentioned above, in each rubber sheet 1, no splice part along the circumferential direction of the tire is formed, but only splice parts in radial direction (or in the width direction of the tire) are formed. In addition, preferably at the splice part 2, an inclined plane, which makes an acute angle (alpha) to a splice plane, is formed at least at that edge part 1e of the rubber sheet 1, which locates on the side facing the inner surface of the tire. In order to ensure the peeling-up effect of release agent by the edge part 1e, the acute angle (alpha) of the inclined plane is preferably set within the range of 30-50 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pneumatic tire, and particularly to a pneumatic tire suitable for large vehicles.

[Prior art]

In the case of a tubeless tire, a non-breathable liner rubber sheet is molded on the inner surface of the tire, and in the case of a tire with a tube, a rubber sheet for protecting the tube is molded as well.

Conventionally, to form the rubber sheet for the inner surface of a tire, an unvulcanized rubber sheet wound into a roll is used.
They were arranged so that the direction of pulling out from the roll (one direction of the calender) coincided with the circumferential direction of the tire, and both ends were joined by a splice section that was perpendicular or oblique to the circumferential direction of the tire. In this case, in the case of a large-sized tire, the width of the rubber sheet is insufficient relative to the tire width, so two rubber sheets 11, 11 are used side by side, as shown in FIG. 4, for example. For this reason,
Splice 1 along the circumferential direction of the tire in a part of the tire center
2 was formed, and as described above, a splice portion (not shown) perpendicular or oblique to the tire circumferential direction was formed at one location on the circumference.

By the way, the unvulcanized rubber sheet used as a raw material is sticky, so when vulcanizing and molding an unvulcanized tire, the unvulcanized tire is molded to improve the slippage between the Prada and the inner rubber sheet. After completion, a mold release agent is applied to its inner surface. On the other hand, when an unvulcanized tire is vulcanized and molded, the unvulcanized rubber sheets arranged on the inner surface of the tire are molded while applying inflation pressure from the inside of the tire. Sulfur rubber sheets elongate in the tire circumferential direction, and especially in bias tires, shrink as shown by arrow B in the tire width direction.

For this reason, especially in bias tires, the splice portion 12 in the state shown in FIG.
Due to the shrinkage in the direction B of the splice part 1 and the expansion pressure from the Prada, the mold release agent 13 on the surface is moved between the tips of the splice part 12 as the edge part 11e deforms, as shown in FIG. 5B. Becomes involved. Such entrainment of the mold release agent 13 becomes cranks and the like after vulcanization molding, resulting in product defects.

In order to prevent such defects, before applying the mold release agent 13 to the rubber sheet 11, splice tape (vinyl tape, etc.) is pasted on the edge portion of the rubber sheet 11 in advance.
It is common practice to peel it off when assembling it. However, such pasting and peeling of the splice tape increases the number of extra steps in the tire manufacturing process, causing a significant decrease in productivity.

[Purpose of the invention]

An object of the present invention is to provide a pneumatic tire that eliminates the above-mentioned conventional drawbacks, eliminates product defects due to mold release agent entrainment without using splice tape, and significantly improves productivity. It's about doing.

[Structure of the invention]

The present invention achieves the above object by arranging a plurality of rubber sheets continuous in the tire width direction in the tire circumferential direction on the inner surface of the tire, and joining both edge portions of these rubber sheets to each other to substantially form a radial direction. A splice portion is formed therein, and if necessary, an inclined surface forming an acute angle with respect to the splice surface is formed at least on the side of the edge portion located on the inner surface of the tire. .

FIG. 3 shows a large-sized pneumatic tire according to an embodiment of the present invention, and a rubber sheet 1 is provided seamlessly in the width direction on the inner surface of this tire T.

FIG. 1 shows an example of an inner rubber sheet made of unvulcanized rubber that is assembled into a cylindrical shape before the tire T is vulcanized.

This cylindrical inner rubber sheet consists of a plurality of (four in the illustrated example) unvulcanized rubber sheets 1. -., 1 form a resplice portion 2 by joining the edge portions 1e and le at both ends in the tire circumferential direction to each other. This unvulcanized rubber sheet 1 is arranged in such a way that the direction in which it is pulled out from a rolled state (calendar direction) is aligned in the tire width direction, so that it is continuous without a seam in the tire width direction. Become familiar.

With this configuration, the rubber sheet 1 does not form a splice portion along the tire circumferential direction, but only a splice portion 2 in the radial direction (tire width direction). In addition, a plurality of splice portions 2 are formed at equal intervals on the circumference of the tire. Preferably, in the splice portion 2, as shown in FIG. 2, at least the edge portion 1e of the rubber sheet 1 located on the inner surface of the tire is formed with an inclined surface forming an acute angle α with respect to the splice surface. .

Such a cylindrical inner rubber sheet made of unvulcanized rubber is molded with a carcass etc. bonded to its upper part, and then vulcanized and molded while applying inflation pressure from the inside with a bladder. At this time, the cylindrical inner rubber sheet elongates as indicated by arrow A in the tire circumferential direction.

In the tire of the present invention, since the inner rubber sheets are joined together only at the splice portion 2 in the radial direction, tension is applied to the edge portions 1e+1e of the splice portion 2 in a direction that separates them from each other, as shown in FIG. Therefore, the problem that the release agent on the surface of the rubber sheet 1 gets caught between the splice parts 2 does not occur.

Furthermore, in the tire of the preferred embodiment of the present invention, since the edge portion 1e is formed with an inclined surface forming an acute angle α with respect to the splice surface, the mold release agent can be peeled off onto the inclined surface, and the splice There is no need to get caught up in part 2.

The effects of the present invention as described above can of course be obtained without the need for troublesome work such as pasting a splice tape on the edge portion 1e in advance and applying a release agent.

In addition, in order to obtain the effects of the present invention as described above,
It is necessary that the direction of the splice portion 2 is substantially radial; if it is slanted, the effect cannot be improved.

In addition, in order to ensure the peeling effect of the edge portion 1e described above, the acute angle α of the inclined surface must be set to 30' to 50''.
It is preferable to keep it within the range of .

〔Effect of the invention〕

As described above, in the pneumatic tire of the present invention, the inner rubber sheet is constructed by arranging seamless continuous rubber sheets in the tire width direction in the tire circumferential direction, and consists only of radial direction splice parts, and the necessary Since the edge portion of the rubber sheet is formed with an inclined surface at an acute angle with respect to the splice surface, the mold release agent will not be drawn into the splice portion during vulcanization molding. Therefore, it is possible to obtain a tire without product defects such as cranks on the inner rubber sheet.

Moreover, the above-mentioned effects of the present invention can be obtained without using the splice tape that was conventionally used when applying a mold release agent, so the work of applying and peeling the splice tape can be omitted. This can significantly improve productivity.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the inner rubber sheet assembled before vulcanization molding of the pneumatic tire of the present invention, Fig. 2 is an enlarged sectional view showing the splice portion of the same inner rubber sheet, and Fig. 3 is the pneumatic tire of the present invention. FIG. 4 is a sectional view of a conventional pneumatic tire, and FIGS. 5A and 5B are enlarged sectional views showing a splice portion of an inner rubber sheet in a conventional pneumatic tire. 1... Rubber sheet, 1e... Edge portion, 2
...Splice part.

Claims (2)

[Claims] (1) At the unvulcanized stage, a plurality of rubber sheets that are seamlessly continuous in the tire width direction are lined up in the tire circumferential direction on the inner surface of the tire, and both edges of these rubber sheets are joined together to form a substantially radial splice. A pneumatic tire characterized by forming a part. (2) The pneumatic tire according to claim 1, wherein an inclined surface forming an acute angle with respect to the splice surface is formed at least on the side of the edge portion located on the inner surface of the tire.