JPH0839697A - Molding method of radial tire for heavy load - Google Patents

Abstract

PURPOSE:To prevent bend of cords of ply cord end part and cord end part of a reinforcing part of a bead by folding-back, by a method wherein a carcass main body side part of a bead part is folded back at a tilting angle at most half of the tilting angle at the time of unvulcanization. CONSTITUTION:Side rubber 3 is wound around and stuck to the top of a pair of right and left cylindrical side bladders 2, around the top of which a nylon chafer 4 is wound wherein a plurality of nylon fiber cords are arranged by taking their extending direction at an angle of 60 degrees clockwise with respect to an axial direction of a cylinder, and laid under coating rubber. Then air is filled within a carcass band 11 inserted into a molding machine and the carcass band 11 is expanded while narrowing a right and left bead lock rings 12 inward of an axial direction. At this time, a part 14 of a carcass main body side of a bead part 13 is positioned to a posture wherein a ply cord of this part forms a tilting angle of almost 30 degrees to the axis of the cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method for improving the durability of a bead portion of a heavy duty radial tire used for trucks, buses and the like.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a heavy duty radial tire, a method of assembling the constituent members of the tire in a molding step to form a so-called unvulcanized tire is first described with reference to FIG.
As shown in FIG. 2, on a cylindrical band forming machine 100, an organic fiber chafer and a wire are provided at both ends of the forming machine.
A reinforcing member 101 of a bead portion such as a chafer is wound and adhered, and an inner liner rubber 102 and a ply layer 103 are sequentially wound on the upper surface thereof to form a carcass band 104. In the reinforcing member 101 of the bead portion, a plurality of organic fiber cords or metal cords are arranged in parallel with each other at an angle of about 60 degrees with respect to the axial direction of the cylinder, and are covered with covering rubber from above and below. It was done.

Next, as shown in FIG. 5, the band 104 is inserted into and mounted on the first molding machine 105 in the first molding step, and the diameter of the drum 106 of the molding machine is expanded so that the carcass at the central portion of the band is expanded. The main body 107 expands in the direction perpendicular to the tire rotation axis, and a pair of left and right step portions 109 are formed between the main body 107 and both end portions 108 of the band 104. The stiffener rubber 112 having a triangular cross section is attached to the carcass body 110 of the bead portion on the step portion 109 from the left and right of the molding machine on the outer periphery of the bead core 111 to be integrated. The attached bead core 113 is pressed. Next, the side bladders 114 provided at both ends of the molding machine 105 are filled with internal pressure and expand, whereby the both end portions 108 of the band in an unexpanded state are the bead cores with stiffeners 113.
It is folded back around and is expanded and attached to the side surface of the stiffener rubber 112. Next, so-called first molded tire 115 is manufactured by adhering side rubber, gum rubber, and the like.

Thereafter, the first molded tire 115 is
It is sent to a molding step (not shown), and the center portion 107 of the band is expanded and deformed from a cylindrical shape to an annular body by a conventional method, and a belt layer and a tread rubber are not additionally attached to the crown. A vulcanized tire is manufactured.

Thus, in the first molding step, the step portion 1 between the carcass body 107 at the central portion of the expanded band and both end portions 108 of the unexpanded band.
Numeral 09 is formed substantially at right angles to the axial direction of the tire, and the carcass body 110 of the bead portion and the stiffener-attached bead core 113 attached to the carcass body 110 are formed by the step portion 109. It is formed into a shape close to the shape of the bead portion of the unvulcanized tire, and in this state, both end portions 108 of the unexpanded band are folded back. The reason for this is
The object is to reduce the change in shape of the bead portion during the forming process from the forming to the second forming, to reduce unnecessary local deformation such as distortion and wrinkles of each member in this portion and to reduce manufacturing defects.

[0006]

However, since both end portions of the band are folded at once from the position parallel to the axial direction of the cylindrical shape and expanded to the position of the shape formed by the step portion, the band Outer end portions in the tire meridian direction of the wire chafer and the organic fiber chafer of the bead reinforcing member attached to both ends are extended in the tire circumferential direction, and the outer end portions of the respective reinforcing members are extended. The code is No. 6
As shown in the figure, the tire deforms and bends in the tire circumferential direction. Following the bending of these reinforcing members, bending is caused in the ply cord of the carcass at the folded portion arranged in the lower layer of the reinforcing member, and the ply cord terminal is locally caused by internal pressure and load when the tire is used. There is a greater concern that the strain will increase and the durability of the tire will decrease. Also,
The bending deformation of the end portions of the reinforcing member and the ply cord is larger toward the end portion of the member. Therefore, the rigidity of this portion decreases, and the rubber of the end portion of the member is deformed due to deformation or heat in the molding process or the vulcanization process. It has been pointed out that the deformation and movement are likely to occur, and that the tire surface characters engraved on this portion are easily distorted and fine cracks are likely to occur on the product tire surface.

In particular, when an organic fiber cord such as polyester fiber or aromatic aramid fiber or an extremely flexible steel cord is used as the material of the ply cord, or the ply turn-up height is set in the tire meridian direction in terms of tire performance. It is expected that the above problem becomes more important when the height is set to the outer side, because the bending deformation is promoted.

Therefore, it is an object of the present invention to use a ply cord by a folding operation, particularly when using a ply cord made of a flexible material or when adopting a structure having a high folding height.
Provided is a method for molding a radial tire for heavy load, which prevents the bending of the cord at the cord end portion and the cord end portion of the bead reinforcing member to improve the durability of the tire and prevent manufacturing defects. That is.

[0009]

In order to achieve the above object, in the method for molding a radial tire for heavy load of the present invention, as described in claim 1, the tire is rolled into a cylindrical shape on a tire molding machine. A bead core member is fitted on the outer surfaces of both end portions of a carcass body whose main constituent elements are the ply layer and the inner liner rubber layer, and the both end portions are surrounded by a bead portion around the bead core member. The carcass body side portion of the bead portion is further folded so that a portion of the bead portion on the carcass body side is inclined from a position parallel to the tire axial direction at the beginning of the head to an angle substantially perpendicular to the tire axial direction. A molding method in which a toroidal unvulcanized tire is formed by standing up until
It is characterized in that the folding back is performed in a state in which the portion on the dregs body side has an inclination angle of approximately half or less of the inclination angle of the portion of the unvulcanized tire.

[0010]

According to the molding method of the present invention, unlike the conventional molding method, the cylindrical carcass is not expanded and deformed into the shape of the unvulcanized tire immediately before vulcanization at once, but especially the bead portion. The carcass body side part of the head is rotated from the position parallel to the cylindrical axis at the beginning of the head to the intermediate position around the bead core from the inside of the cylindrical axis to the outside, and the state is raised. At this position, both ends of the carcass are turned around the bead core from the outside of the cylindrical shaft toward the inside and folded back, and the both ends are attached to the side surfaces of the stiffener rubber on the bead core. After that, expansion and deformation were performed again so as to obtain the shape of the unvulcanized tire immediately before vulcanization, and the portion of the bead portion on the side of the carcass body was raised up to an inclination angle substantially perpendicular to the tire axial direction. Can be raised. Here, the intermediate position of the portion of the bead portion on the side of the carcass body means an angle of inclination perpendicular to the axial direction formed by the portion of the bead portion of the unvulcanized tire on the side of the carcass body. On the other hand, the position is such that it has a small inclination angle approximately in the middle.

As described above, since both ends of the carcass folded back at an intermediate position with a small inclination angle have a small diameter expansion amount, the ply cord or the cord of the bead reinforcing member is not bent and deformed. It is small, and in this state, it is pressure-bonded to the side surface of the stiffener rubber so that the above-mentioned curving deformation is fixed. Therefore, when the carcass is expanded again until both ends of the carcass are expanded until the shape of the unvulcanized tire just before vulcanization is obtained, the rubber between the cords only expands and the both ends are expanded. The bending deformation of the ply cord of the portion and the cord of the bead reinforcing member is suppressed. As a result, it is possible to prevent the rigidity of the cord end portion from being lowered, prevent abnormal flow of rubber in the vulcanization process, prevent distortion of characters and minute cracks on the tire surface, and prevent the bead portion of the product tire from being damaged. The durability is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. 1 to 3 show an example of the tire molding method of the present invention. Referring to FIG. 1, a pair of left and right cylindrical side bladders-2 installed on the left and right sides of the molding machine 1 is wound and pasted with a side rubber 3 in which a narrow rubber chafer 3'is set in advance in the axial direction. Be worn. Then, a plurality of nylon fiber cords are arranged in parallel on the upper surface thereof with the extending direction thereof being clockwise at an angle of 60 degrees with respect to the cylindrical axis direction, and two layers of nylon chafer-4 embedded in the coated rubber are provided. It is wound with the code angles crossing each other. Further, a plurality of steel cords are juxtaposed on the upper surface of the nylon chafer-4 so that the extending direction thereof is clockwise at an angle of 60 degrees with respect to the cylindrical axis direction, as described above. One layer of wire chafer 5 embedded therein is attached. In this way, the inner surface of the tire member prepared on the side bladder-2 was formed into a cylindrical shape in the previous step in advance.
On the upper surface of the liner rubber 6, two ply layers 7 in which a plurality of aromatic aramid cords are arranged in the axial direction and covered with rubber are wound, and a pair of left and right cushions are provided on the left and right of the central portion of the ply layer 7. A carcass band 11 manufactured by sticking the rubber 10 is inserted. Then, the bead cores 9 having the stiffener rubbers 8 placed on the outer peripheral surfaces thereof are fitted on both ends of the ply layer 7, respectively, and installed inside the molding machine 1 and below the bead cores 9. The diameter of the bead lock ring 12 is expanded, and the tire member on the side bladder-2 together with the ply layer 7 is pressed against the inner peripheral surface of the bead core 9.

Next, as shown in FIG. 2, while the left and right bead lock rings 12 are narrowed inward in the axial direction, air having a predetermined pressure is introduced into the carcass band 11 inserted into the molding machine. Is filled in a specified amount to expand the carcass band 11. At this time, the portion 14 of the bead portion 13 on the carcass body side
Indicates that the ply cord of this part is approximately 30 with respect to the cylindrical axis.
It is positioned so that it has a tilt angle of 4 degrees. In this posture, the side bladder-2 is expanded and both end portions 15 of the carcass and the tire member prepared on the side bladder-2 are folded back to the side surface of the stiffener rubber 8 at one time and pressed. Further, the side bladder-2 is contracted and returned to its original position, and the upper portion of the folding member is firmly re-compressed to the side surface of the stiffener by a pressing device such as a stitcher (not shown).

At this time, both ends 15 of the carcass and the ends of the cords embedded in the nylon chafer-4, the wire chafer-5, etc. are located on the carcass body side of the bead portion. The ply cord of the part 14 is expanded from the initial cylindrical position to a position where it has an inclination angle of about 30 degrees with respect to the cylindrical axis, but the expansion amount is small and therefore the bending deformation of the cord terminal is Is not big enough to be a problem.

Next, as shown in FIG. 3, while again narrowing the left and right bead lock rings 12 inward in the axial direction (arrows in the figure), the inside of the carcass band 11 is additionally filled with air of a predetermined pressure. Then, the carcass band 11 is expanded into a torus.
Then, the tread rubber formed in a separate step and the ring-shaped laminate 16 of four belts are fitted to the top of the carcass layer to form an unvulcanized tire 17.

At this time, the ends of the cords embedded in the both ends 15 of the carcass, the nylon chafer-4, the wire chafer-5 and the like are the carcass body side of the bead part. The ply cord of the portion 14 is greatly expanded from the position with the inclination angle of 30 degrees to the position where the inclination angle is substantially perpendicular to the cylindrical axis. At the stage shown in FIG.
Since the end of the cord is firmly pressed against the side surface of the stiffener rubber, free bending of the cord is suppressed and the unnecessary bending deformation is prevented.

A drum endurance test was conducted on the tire of the example according to the molding method of the present invention described above and the tire of the comparative example according to the above-described conventional method, with the tire size being 1000R20 and the tire materials and structures being the same. As a result of the execution, the tire of the example is 13 compared with the tire of the comparative example.
A high durability of 0% was obtained. The test conditions are: tire internal pressure 6.75 kg / cm ² , tire load JIS standard 200.
%, The running speed is 60 km / hour, and the tire is pressed against the inner peripheral surface of a steel drum having a diameter of 3 m to run.

In the above embodiment, when the ply layer and other tire members are folded back, the molding machine and the carcass are transformed into an annular body and the tread rubber and the belt layer are attached. Although the same molding machine as that of
From the main point of the molding method of the present invention, the
A method of performing molding and second molding can be used.

The softer the ply cord is, the easier it is to obtain the effect of the present invention. In addition to the aromatic aramid cord used in the examples, polyester cord, nylon cord, etc. Organic fiber cords and small bending stiffness steel
The present invention exerts a great effect when a rucord or the like is used as a plycode.

[0020]

According to the molding method of the present invention, the bending deformation of the ply cord of the bead folding portion and the cord end of the bead reinforcing member is suppressed to a very small level, and the folding end portion of the ply layer is not damaged. In addition to the suppression of the durability performance, the distortion of the engraved characters on the bead portion is reduced, and the production defects such as the occurrence of microcracks on the surface rubber can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a first stage of a molding method of an example according to the present invention.

FIG. 2 is a diagram showing a folding step of a molding method of an example according to the present invention.

FIG. 3 is a diagram showing a final stage of a molding method of an example according to the present invention.

FIG. 4 is a diagram showing band molding in a conventional molding method.

FIG. 5 is a diagram showing first molding in a conventional molding method.

FIG. 6 is a view showing a curved deformation of a bead reinforcing member and a ply code.

[Explanation of symbols]

 1 Molding Machine 2 Side Bladder 3 Side Rubber 3'Rubber Chafer 4 Nylon Chafer 5 Wire Chafer 6 Inner Liner Rubber 7 Ply Layer 8 Stiffener Rubber 9 Bead Core 10 Cushion Rubber 11 Car Cas band 12 Bead lock ring 13 Bead portion 14 Carcass body side 15 Ends of carcass 16 Ring-shaped laminate 17 Unvulcanized tire 100 Band forming machine 101 Chafer member 102 Inner liner -Rubber 103 Ply layer 104 Band 105 First molding machine 106 Drum 107 Carcass body 108 at the center of the band 108 Both ends 109 Step 110 Carcass body at the bead portion 111 Bead core 112 Stiffener rubber 113 Stiffener rubber Attached bead core 114 Side bladder 115 1st generation Tire

Claims (1)

[Claims] 1. On a tire molding machine, a bead core member is fitted on the outer surfaces of both ends of a carcass body mainly composed of a cylindrically wound ply layer and an inner liner rubber layer. The both end portions are folded back around the bead core member toward the carcass body side of the bead portion, and further, the portion of the bead portion on the carcass body side is the head axial direction of the head. Is a molding method in which an unvulcanized tire having a torus shape is formed by standing up from a position parallel to the tire to an inclination angle substantially perpendicular to the tire axial direction, wherein the carcass body of the bead portion is formed. A method for molding a heavy-duty radial tire, characterized in that the folding is performed in a state where the side portion has an inclination angle that is substantially half or less of the inclination angle of the unvulcanized tire.