JPH02297427A - Air bladder for forming tire - Google Patents

Abstract

PURPOSE:To surely deform an air bladder in a state that the bladder is expanded widthwise while its central region remains flat by a structure wherein a cord layer is imbedded in the interior of a gummous layer at the central region of the bladder in addition to a radial cord layer, which extends over the whole width of the gummous layer, so as to form a multi-layered layer at the control region of the bladder. CONSTITUTION:In the interior of the gummous layer 10 of an air bladder, at least one radial cord layer 5, which extends over the whole width of the gummous layer, is imbedded and, at the same time, one or a plurality of cord layers 6 are imbedded at the central region 3, which almost corresponds to the tread part of a tire as the molding object. Accordingly, when the air bladder is expandingly deformed, the central region possesses the elastic force larger than that both the side regions possess, since multiple layers are formed at the central region, which almost corresponds to the tread part of the tire, resulting in suppressing the natural shaping deformation at the central region. Consequently, both the side regions are expandingly deformed initiatively, resulting in allowing to generate a wide swollen-out shape, in which both the bead parts 2 are properly narrowed and the upper part of the central region is flat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention mainly relates to an air bladder used for second molding of a radial tire.

[Prior art and problems to be solved] In radial tires, a breaker layer (belt) with a small elongation rate is provided in the center area of the tire and does not elongate in the circumferential direction. A step molding method is used.

In the first stage, a green case was made by attaching bead members and side treads to the carcass ply.
In the second step, the green case is toroidally deformed until it comes into contact with the play curling by the internal pressure filling of the air bladder and the approaching movement of the former ring, and the breaker layer and top tread layer are bonded to the outer periphery of the central area, and the product is manufactured. It is molded into a shape that roughly corresponds to the tire.

In recent years, for the purpose of further improving the cornering response, maneuverability, and stability of this type of radial tire, there has been a trend toward flattening the tire and widening the tire width (for example, an aspect ratio of 70 to 45%).

In order to manufacture such a flat tire, it is necessary to mold it into a shape corresponding to the green tire at the green tire molding stage.

However, when a conventional air bladder made of a rubber sheet is expanded and deformed by filling with internal pressure, it expands in the radial direction into a large elliptical shape as shown in FIG. Therefore, the green tire (T) formed by this air bladder (1') has a bead part (T1).
When this is placed in a vulcanization mold and vulcanized, a large deformation is applied from the side part (T2) to the bead part (T1), resulting in a large overhanging shape at the bead part (T1).
More tension than necessary is applied to the carcass ply (e) wrapped around the bead wire (b), and as shown in Fig. 10, the rubbery layer (10°) melted during vulcanization migrates to the outside, causing the above-mentioned They will be gathered around the carcass ply (C) or bead wire (b), and the bead part (T
The shape and strength of I) become unstable.

As a countermeasure, an air bladder made of a rubber layer without a cord layer is made thicker in the center region corresponding to the crown width of the tire to be molded, and thinner in the remaining regions corresponding to both side parts (especially Publication No. 52-32786).

However, in this case, since the rubber layer does not have a cord layer, the bladder grows due to repeated expansion and deformation, and there is a problem that a stable toroidal shape cannot be obtained.

In addition, the inner surface of the area corresponding to both ends of the tire's tread crown is formed within the thickness so as to be convex inward from other areas, and the tire width is An air bladder has also been proposed (Japanese Patent Publication No. 56-44818) in which a non-extensible cord layer is embedded at a uniform depth below the inner surface over the entire width in the direction.

However, in this air bladder, it is necessary to form a convex part on the inner surface and to make it partially thick, and the cord layer must be buried at a uniform depth along the shape of the convex part. First, it is not easy to manufacture and has poor practicality.

51 The present invention has been made in view of the above, and its purpose is not to suppress expansion deformation in the central region only by changing the wall thickness of the air bladder, but also to suppress expansion deformation in the central region by changing the thickness of the air bladder. In particular, in addition to the radial cord layer spanning the entire width in the width direction, several additional cord layers are embedded in the center area corresponding to the tire tread to suppress expansion and deformation in the center area, which eliminates the above problem. An object of the present invention is to provide an air bladder that can be inflated and deformed into a shape suitable for molding green tires for manufacturing flat tires without causing any damage.

Another object of the present invention is to create an air bladder which has a large effect of suppressing expansion deformation in the central region by embedding a bias cord as a cord layer in the central region, and which makes it possible to form a flatter green tire. - in providing the following.

Furthermore, in the case of a cord layer or bias cord buried in the central region, when molding is performed by expanding and deforming the former by approaching the former and filling the internal pressure, the effect of suppressing the expansion and deformation in the central region is large, but it is relatively A high internal filling pressure is required, and the force required to bring the former ring close together is also large, so the machine must be constructed to be more robust.

Another object of the present invention is to provide an air bladder that does not cause the above-mentioned problems, and as a result of various studies and studies, it has been found that the cord layer buried in the central area is not the same as the radial cord layer. Even if the cord direction is approximately the same as the cord direction of
In other words, it was found that the natural shaving deformation can be suppressed, and the filling internal pressure and the force for bringing the forming ring closer together can be weak, and this was done based on this knowledge.

In addition, in addition to the radial cord layer covering the entire width as described above, if a cord layer is further embedded in the center area corresponding to the tire tread part to suppress expansion deformation in the center area, when the center area is expanded and deformed, If a separation phenomenon occurs at both ends of the cord layer, the effect of suppressing expansion and deformation in this part decreases, and the parts corresponding to both ends of the tire breaker expand and deform excessively, or the degree of expansion and deformation increases. This may result in unevenness and twisting or distortion, which may have an adverse effect on the green tire being molded. Therefore, the present invention also solves this problem.

[Means for Solving the Problems] In order to solve the above problems, in the air bladder for tire molding of the present invention, at least one radial cord layer covering the entire width is provided inside the rubber layer of the air bladder. It is characterized in that one or more cord layers are buried in a central region that substantially corresponds to the tread portion of the tire to be molded.

As the code layer in the central area, it is possible to bury a plurality of bias code layers forming a required code intersection angle, but it is particularly preferable to bury a code layer having a code direction substantially the same as the radial code layer. suitable. In the case of a code layer having a code direction substantially in the same direction as the radial code layer, it is preferable that the code direction of the code layer is substantially the same direction at an angle of 0 to 5 degrees with respect to the code direction of the radial code layer.

Further, in any of the above cases, it is desirable that the cord layer in the central region is buried inside the radial cord layer with approximately the same width or a slightly wider width than the tire breaker layer. Further, it is preferable that narrow code layers having substantially the same code direction as the radial code layer are buried in both sides of the code layer in the central area.

[Function] According to the air bladder of the present invention having the above-mentioned configuration, by approaching the former rings that hold both ends and filling the internal pressure,
When the air bladder is inflated and deformed, in the central region that roughly corresponds to the tire tread, there are one or more cord layers buried in addition to the radial cord layer, resulting in a multilayer structure. The specific elastic force is greater than that in both side areas where only the cord layer is buried.
The expansion element, that is, the natural shaving deformation is suppressed.

As a result, both side regions expand and deform first, and the bead portion of the green tire can be securely held between the air bladder and the former ring, allowing both bead portions to be narrowed appropriately, and the upper part of the center region. The green tire has a flattened, wide, bulging shape, which allows the green tire to be molded into a shape close to that of a production tire.

In particular, when a plurality of bias cord layers forming a required cord intersection angle are buried as the cord layer in the central region, although the pantograph action allows expansion and deformation to some extent, it is difficult to suppress the expansion and deformation. The effect is large, and it becomes possible to easily form a wide green tire with a larger aspect ratio.

In addition, if a code layer in the central region is embedded with a code layer whose code direction is substantially the same as that of the radial code layer, it will be more resistant to expansion and deformation than in the case of the bias code described above. The resistance is small, and therefore the filling internal pressure for molding and the force required for approaching the former ring are small.

Moreover, the radial cord layer embedded within the rubber layer of the air bladder and the cord layer in the central area prevent the rubber layer from growing due to repeated expansion and deformation.

In addition, if narrow cord layers are stacked and buried at both ends of the cord layer in the central area, separation phenomenon at both ends of the cord layer in the central area can be prevented, and the expansion and deformation of this area can be suppressed. It is possible to prevent excessive expansion and deformation due to a decrease in the temperature and uneven expansion and deformation, and no twisting or distortion occurs.

[Example] Next, embodiments of the present invention will be described based on the drawings.

Figures 1 and 2 are cross-sectional views showing the structure of the air bladder (]) of the present invention, with Figure 1 in its normal uninflated state and Figure 2 in its expanded and deformed state (when molded). It shows.

The air bladder (1) is made of a rubber endless tube, and has bead portions (2) (2>) at both ends.
) (2) It is held by the support part of the former ring (P). (3) is a central region that roughly corresponds to the tread of the tire to be molded, (4) (4) is both side regions continuing from the central region (3), and the bead portion (2
) and (2) is slightly longer than the green case (g).

(5) is at least one radial cord layer buried inside the rubber layer (10) of the air bladder (1), and extends in the radial direction, that is, the width direction (meridian direction) over the entire width of the bladder. It is buried in

(6) is a one- or multiple-ply cord layer embedded in the rubber layer (10) of the central region (3) that substantially corresponds to the tire tread portion inside the radial cord layer (5), As a result, the central region (3) is formed into multiple layers.

As shown in FIG. 4, the code layer (6) in the central area can be embedded with multiple layers of bias code layers forming a required code intersection angle. (5) 30 for the code h° direction
~60°.

Also, as the code layer (6) in the central area, as shown in Figure 5,
The code layer may have a code direction substantially in the same direction as the radial code layer (5). In this case, the cord direction of the cord layer (6) may have a slight angle (10 degrees or less) with respect to the cord direction of the radial cord layer (5), but is preferably in the range of θ to 5 degrees. That is, if the angle in the cord direction of the cord layer (6) exceeds 100, a large filling internal pressure will be required during molding.

The width dimensions of these cord layers (6) are set to be approximately the same width or slightly wider than the tire breaker layer, depending on the shape and dimensions of the tire to be molded. For example, in the case of 2-ply, as shown in the figure, one layer (6a) is approximately the same width as the tire breaker layer, and the other layer (8b) is slightly longer than this, for example, about 5 to 15 mm longer at both ends. be done. If this cord layer (6) is bias cord, etc., and is at an angle with respect to the cord direction of the radial cord layer (5), use an even number of plies to make the inclination of the cord direction symmetrical and uniform on the left and right sides. It is desirable to allow expansion and deformation.

The number of plies of this cord layer (6) may be set depending on the rubber quality, cord strength, tire shape, etc.

FIG. 3 shows another embodiment of the air bladder (1) of the present invention, in which the cord layer (3) in the central region (3) is shown.
Another narrow cord layer (6c) (t
ie) are buried on top of each other. This code layer (6c
) (6c), regardless of the code direction of the code layer (6), a bias code can be used as illustrated in FIG. 4, or as illustrated in FIG. 0 to 5° to the cord direction of layer (5)
It is also possible to use those which are in substantially the same direction, such as, and the latter is particularly preferable. This code layer (Be) (6c)
may be inserted between the code layers (6a) and (6b).

By doing this, it is possible to prevent the occurrence of separation phenomenon at the time of expansion and deformation at both end portions of the cord layer (6), and the expansion suppressing effect is reduced, causing excessive expansion and deformation in these portions, or expansion and deformation. Non-uniformity can be prevented, and it can be molded into a predetermined shape without twisting or distortion.

Further, as the code layer (6) in the central area (3>), although not particularly shown, a code layer and a bias code layer having substantially the same code direction as the radial code tank may be buried in combination. .

The cord material for the radial cord layer (5) and the cord layer (6) in the central region (3) may be either fiber or metal, but the former fiber is preferable in terms of its adhesion to rubber. As the fibers, nylon, polyester, rayon, vinylon, and other synthetic fibers with excellent tensile strength are preferably used. In particular, from the viewpoint of adhesion to rubber, cords whose fibers are coated with rubber or adhesive are suitable. Moreover, adhesive rubber can also be used as the rubbery layer.

FIG. 6 shows a state in which a green tire (T) is molded by the air bladder (1) of the embodiment shown in FIG.

Air bladder (1) is filled with internal pressure and formed (
When expanded and deformed due to the approach of F), the rubber layer (10)
In addition to the radial cord layer (5) inside the radial cord layer (5), in the central region (3) corresponding to the tread portion of the tire to be molded, there is one or more cords arranged in substantially the same direction as the radial cord layer (5). Since the code layer (6) of the layer is buried, the central area (3) has multiple layers compared to both site areas (4) (4). Therefore, the elastic force in the central region (3) is stronger than that in both side regions (4) where the radial cord layer (5) is only buried. Compared to this, the expansion deformation, that is, the natural shaving deformation, is suppressed.

As a result, both side areas (4) (4) expand and deform first, and the bead portion (TI) of the green case (g) supported by the air bladder (1) and the former ring (P
), and both bead parts (TI) (TI
) can be suitably narrowed, and the mid-bladder region (
3) has a wide bulge shape with a flattened upper part, which allows the green tire (T) to be molded into a shape close to that of a product tire.

In particular, when multiple layers of bias cords forming a required cord intersection angle are buried as the cord layer (6) in the central region (3), although the pantograph action allows expansion and deformation to some extent, the radial Compared to the cord layer, its circumferential length is difficult to expand, and the effect of suppressing expansion and deformation is greater, making it possible to reliably form a wide green tire with a higher aspect ratio.

In addition, the cord layer (6) in the center area, which is buried separately from the radial cord layer (5) spanning the entire width, has a cord direction that is approximately the same as that of the radial cord layer (5). Although there is an effect of suppressing expansion and deformation of the area, the filling internal pressure during molding and the force required for the former ring (P) to approach are smaller than in the case where the bias cord layer is buried as described above, making it more convenient.

For example, if two layers of bias cords are buried as the cord layer in the central region, a filling internal pressure of about 1.5 to 3.0 kg/eJ is required, but the present invention in which two layers of cord layers (6) are buried In the case of 0.7 to 1. It can be molded with a filling internal pressure of about Okg/crK.

And a green tire (T) molded as described above.
When placed in the vulcanization mold and vulcanized, the bead part (T1
), the carcass ply (e) wrapped around the bead wire (1) can be vulcanized without applying more tension than necessary, and as shown in Figure 7, the carcass ply (C) It does not gather around the bead wire (b) and is stable in shape and strength.

To manufacture the above air bladder (+), as shown in FIG. 8, a cover rubber (11) is wrapped around a drum (20) whose width is adjustable by a spacer (21),
At least one layer of radial cord (5) is wound, rubber (12) corresponding to the bead portion (2) (2) is fitted into the circumferential grooves (22) on both sides, and one or more plies are placed in the central area. The cords (6a) and (6b) were wound in such a way that the cord direction was approximately the same as that of the radial cord layer (5), and if necessary, narrow cords were overlapped at both end portions. After that, put the inner liner rubber (1
3) is wrapped and vulcanized while being tightened with a bandage made of nylon fabric. After vulcanization, the bandage is removed, the surface rubber layer is cut to a predetermined thickness, and then the bandage is turned over from one side and pulled out from the drum (20) to change the front and back sides, thereby forming the radial cord layer (5) and the cord layer. (6)
An air bladder (1) of the present invention is obtained in which the rubber layer (10) has a flat surface and is embedded in the rubber layer (10).

[Effects of the Invention] As described above, according to the present invention, a cord layer is embedded in the central region inside the rubber layer, separate from the radial cord layer covering the entire width, and the central region is made into a multilayer. Since natural shaving deformation can be suppressed and the green tire can be reliably deformed into a state in which it is flattened in the central region and expanded in the width direction, the green tire thus molded has a shape close to that of a manufactured tire. In other words, since the shape is close to the green tire shape or the vulcanization mold, the lift during vulcanization can be made uniform and the movement deformation can be minimized, and vulcanization can be performed without forcing the tire bead to undergo extreme deformation. This makes it possible to improve the uniformity of the dimensions and shape of the product tire, thereby making it possible to obtain a flat and wide radial tire with good dimensional stability even in the bead portion.

In particular, if the code direction of the code layer buried in the central area is approximately the same as the code direction of the radial code layer,
The internal filling pressure during molding and the force required to bring the formers closer together are smaller than when using a bias cord, so the burden on the mechanical equipment is lighter and there is no need to make it structurally very strong. .

In addition, if narrow cord layers are stacked and buried at both ends of the cord layer in the central area, separation phenomenon at both ends of the cord layer in the central area can be prevented, and expansion and deformation of this area can be prevented. You can prevent it from becoming excessive or uneven,
Since no twisting or distortion occurs, a green tire with a predetermined shape without twisting etc. can be molded.

Furthermore, the above-mentioned air bladder is excellent in maintaining the accuracy of the rubber layer due to the reinforcing effect of the radial cord layer and the cord layer in the central region, preventing the bladder from growing due to repeated internal pressure filling, and has excellent durability. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention in an uninflated state, FIG. 2 is a sectional view in the same inflated state, FIG. 3 is a sectional view showing another embodiment, and FIGS. Fig. 5 is a schematic diagram showing the overlapping state of the cord layers same as above, Fig. 6 is a sectional view showing the state of molding by the air bladder of the present invention, and Fig. 7 is a schematic diagram showing the state of molding by the air bladder of the present invention. An enlarged sectional view of a sulfurized tire bead, FIG. 8 is an explanatory diagram of the air bladder manufacturing state, FIG. 9 is a sectional view showing a conventional air bladder in an inflated state, and FIG. FIG. 2 is an enlarged cross-sectional view showing a defective state of a tire bead portion vulcanized from a green tire. (1)...Air bladder 1 (3)...Central area, (
4)...Side area, (5)...Radial cord layer, (
6)...Code layer in the central region, ([ic) ([ic)
...Narrow cord layer. (10)...Rubber layer. Patent applicant: Toyo Rubber Industries, Ltd. Figure 10

Claims (1)

[Claims] 1. An air bladder consisting of an endless sheet held at both ends by a pair of former rings, which causes toroidal deformation of a green tire due to expansion and deformation of the air bladder due to internal pressure filling and the approaching movement of the former rings. In an air bladder that molds a green tire by guiding and supporting the air bladder, at least one radial cord layer covering the entire width is embedded inside the rubber layer of the air bladder, and the tread of the tire to be molded is embedded. 1. An air bladder for tire molding, characterized in that one or more cord layers are embedded in a central region that substantially corresponds to the center region. 2. The air bladder for tire molding according to claim 1, wherein a plurality of bias cord layers forming a required cord intersection angle are embedded as the cord layer in the central region. 3. The air bladder for tire molding according to claim 1, characterized in that a cord layer having a cord direction substantially the same as that of the radial cord layer is embedded as the cord layer in the central region. 4. The air bladder for tire molding according to claim 3, wherein the cord direction of the cord layer in the central region is substantially the same as the cord direction of the radial cord layer at an angle of 0 to 5 degrees. 5. According to any one of claims 1 to 4, narrow code layers having substantially the same code direction as the radial code layer are superimposed and buried in both end portions of the code layer in the central region. air bladder for tire molding.