JPS6183025A - Manufacture of radial tire - Google Patents

Abstract

PURPOSE:To obtain a tire, in which the rigidity of carcass chord is uniform, by a method wherein upper and lower chords of lap joint section of carcass ply are cut at opposing positions with respect to a center line to joint them by lap joint and compressed air is loaded into the cavity after forming by vulcanizing to cool the tire. CONSTITUTION:In first forming process, a plural pieces of the chords 11, 11' at each of the cut pieces 10, 10 of carcass band are cut to provide cut sections 12, 13, the cut pieces 10, 10 are jointed by lap joint under lapping them by a length equal to the cut sections 12, 13 to form the cylindrical carcass ply 18 and both rims thereof are rolled into bead cores 17 to fix them. In the second process, a clean tire, to which a belt 14, a tread 15 and side walls 16 are bonded, is formed by vulcanizing thereafter, compressed air is loaded into the cavity of the tire to cool it under providing the carcass chord with a tension. According to this method, the rigidity of the carcass chord may be uniformed and the manufacture of the radial tire, excellent in uniformity, may be effected.

Description

[Detailed Description of the Invention] Ca) Industrial Field of Application Regarding the method for manufacturing a pneumatic radial tire of the present invention, more specifically, the method of manufacturing a pneumatic radial tire of the present invention is concerned with the deterioration of uniformity caused by the joints of the carcass layers and the side wall part. This invention relates to a method for manufacturing a radial tire that improves appearance defects caused by unevenness.

(b) Prior Art A radial tire is usually manufactured by the following process. The carcass cord is used as the warp to make a blind weave, and while it is wound in the warp direction, it is rubberized to create a long sheet-like carcass material, and this carcass material is oriented perpendicular to the cord or at an angle close to this. Cut the paper at specified intervals in the width direction at a slight angle. The sides parallel to the cords of the obtained T-cut pieces are overlapped and brought into contact with each other to form a long band in which the cords are arranged in parallel in the width direction. Next, in the first molding step, the band is wound around a molding drum, and the band is cut along the circumference length or slightly longer than the cord.
Both ends are overlapped to form a cylindrical shape, and bead core assemblies are fixed to the edges of both ends of the cylinder to form a first case.

Next, the first case is transferred to a second molding machine, expanded into a toroidal shape, and a belt, tread rubber, and sidewall rubber are attached to form a green time.

Further, in the vulcanization process, this green tire is placed in a mold with a trend pattern and vulcanized to form a vulcanized tire.

Therefore, the carcass layer 1ζ of the radial tire is
There is always an overlapped part of the cut pieces formed in the molding process,
Furthermore, the carcass band is formed by the above-mentioned carcass band manufacturing process.
There is an overlapping joint of cut pieces.

During the tire molding process, when the cylindrical first case is expanded into a toroidal shape, in order to prevent the overlapped portions of the carcass layers from peeling off, the overlapped portions of the carcass layers are coated with carcass cords 2 to 2. Five kneaded pieces are overlapped and joined together. For this reason, the density of cords is high at overlap joints, so
Other parts of the carcass layer (relatively stiffer)
As a result, the lap joint becomes deformed, deteriorating the uniformity of the tire, and when the tire is filled with internal pressure, a recess is created on the surface of the tire's sinide wall.
This can cause damage to the appearance of the tire.

As a means to solve this point, Special Edict 57-1124
No. 0 discloses a method of reducing the rigidity of the overlapping joint of cut pieces produced in the carcass band manufacturing process by using a cord with a higher number of twists and lower rigidity in the selvedges and other parts of the blind weave. Japanese Patent No. 59-59502 discloses a method of cutting only the cord at one end of two cut pieces or shredded pieces that are to be overlapped and spliced.

(c) Problems to be Solved by the Invention However, among the above conventional solutions, the former is effective for the overlap joints that occur in the carcass band manufacturing process, but it is effective for the overlap joints where the overlap joints are not determined in advance. It cannot be used for overlapping joints of cut pieces in one molding process. In addition, in the latter method, the overlapped part overlaps the uncut cord and the cut gamma cord, so it is impossible to make it the same rigidity as the other part consisting only of the uncut cord. Although there has been some improvement in tire uniformity and appearance, there is still no complete solution.
There can be no definitive solution.

Therefore, the present invention provides a radial tire with excellent uniformity and appearance that has a rigidity of the carcass ply overlapping joint part produced in the carcass band manufacturing process or the first molding process of the radial tire, which is different from the rigidity of other parts. The second objective is to provide a method for manufacturing.

ω) Measures to solve the problem The woven carcass cord is pre-soaked in a mixture of resorcinol-formalin resin and latex before being rubberized, and then dried and subsequently stretched in order to increase the stiffness of the cord. While doing so, heat setting is performed. When a cord that has been heat-set with a high elongation rate is exposed to high temperatures, it tends to contract due to the stress exerted on it to return to its original length.

The ratio of the amount of shrinkage at this high temperature is called the dry heat shrinkage rate.

Taking a polyester cord as an example, FIG. 3 shows the relationship between Young's modulus and dry heat shrinkage rate under different heat setting conditions. From this, it can be seen that the higher the dry heat shrinkage rate, the higher the Young's modulus, and when a cord with a large dry heat shrinkage rate is heat-treated and heat-shrinked,
It can be seen that the dry heat shrinkage rate decreases and the Young's modulus decreases. Based on this principle, if the cords of the carcass ply body are not heat-shrinked, and only the cords at the lap joints can be heat-shrinked, the Young's modulus, or rigidity, of only the cords at the lap joints will be reduced, and the whole carcass ply will be reduced in stiffness. As a result, uniform rigidity can be achieved. The present invention utilizes this to cut and overlap both the upper and lower cords of the overlap joint part of the carcass ply at at least one position opposite to the tire center line, and to add After sulfur molding, the inner cavity of the tire is filled with compressed air and the carcass cord is cooled while applying tension, thereby generating a heat medium only in the carcass cord at the overlap joint, reducing the rigidity of the carcass cord. It is possible to manufacture radial tires with uniform rigidity and excellent uniformity.

Next, the content of the present invention will be explained in more detail with reference to the drawings. d Figure 1 is a perspective view showing the main part of the state in which the cut pieces of the carcass hand are overlapped and joined in the first molding step of the radial tire manufacturing method of the present invention. FIG. 2 shows the carcass ply overlap Riζ and ζ of the radial tire manufactured by the method of the present invention.
FIG.

A long rubberized carcass material made from a carcass cord as a warp thread is cut in the width direction at right angles to the cord or at an angle close to this to create a number of cut pieces (1). 1) are overlapped and joined in the width direction parallel to the cord, but at this time, make at least one cut in the tip (2) of one of the cut pieces (1) that will be on the lower side at the overlapped part. Form the tip cutting part (3) and attach the cord (4) at the tip of the cut piece.
) into 1 to 10 pieces.

When cutting at one location, the cutting portion (3) is preferably provided at a position that is inside (5) of one of the bead portions when the tire is molded, and more preferably, the cutting portion (3) is provided inside the bead portion and at the bead base ( 6) to the height of the rim flange (7).

Next, a rear end cut portion (9) is also provided at the rear end (3) of the next shredded piece (1) that overlaps the upper side of this shredded piece (2),
Cut 1 to 10 cords (4) at the rear end (8). The number of cords to be cut is the tip (2) and rear end (2) that will be overlapped.
It is desirable to have approximately the same number in 3). Rear end cutting 5 (9)
is formed into a tire and is provided at a position where the bead part (5) is on the opposite side to the distal end cut part (3) which is overlapped and spliced to the center line 11 of the tire.

As mentioned above, cuts mc3>, (9) are provided on the leading edge (2) and trailing edge (8) of each cut piece (1), (1), respectively, and the cutting pieces mc3> and (9) are sequentially cut on the tip (2) of the cut piece (1). Adjacent shredded pieces (
1) and the rear end (3) are overlapped and connected to form a long carcass band, which is then rolled up. It is preferable that the overlap distance be approximately the same as the length of the cut portions (3) and (9).

Next, in the first molding step, this carcass band is wound around a drum and cut along the cord in the width direction of the band so that the length is equal to or slightly longer than the length of the drum to obtain a cut head. As shown in FIG. 1, 1 to 10 cords (11) at one end of the head of this cut piece are cut to provide a tip cut part (121).
1 is cut in approximately the same number to provide a rear end cut part (1 plow).This tip cut part (1 kake) and the rear end cut part (1 plow) will become the bead part (5) on the opposite side when molded into a tire. More preferably, it is located inside the bead part and between the height of the bead base (6) and the rim flange (7).When molded into a tire, the cut @ ( 1z).

When the cord is located on the outer side of the tire in the radial direction than the bead portion (5), the repeated deformation of the carcass ply during use of the tire increases, and separation is likely to occur from the cord end at the cut portion.

The cord cutting operation at both ends of the cut piece αQ may be performed before or after winding the carcass band around the drum. The work order is selected in consideration of workability.

Band cut piece α1. Cut both ends of α1 @t+z+,
The length of 1131 is overlapped and joined to form a cylindrical carcass ply (18), the bead core assembly is fitted on both edges of the cylinder, and both edges are folded outward so as to wrap around the bead core, and the bead core is fixed. to form the first case.

It is desirable that the lengths of the cut parts H:, , 13+ at both ends of the cut piece GCI be the same length, and the overlap margin of the overlapped part to be equal to the length of the cut part, but if the length of the cut parts at both ends is If they are different, set the overlap margin equal to the length of the longer cut section. If the cut part comes out from the overlapped part, the carcass strength will decrease because the cord in that part is cut. If the upper and lower cut parts at the lap joint are separated by l distance from the bead on the opposite side of the tire, the cut parts are mutually (reinforced by) the cord at the other end of the overlap, so the carcass Strength is not substantially reduced.

The number of cords to be cut at the cutting part is 1 to 10, preferably 3 to 6. If the number exceeds 10, the overlap will become large and the uniformity will deteriorate.

Next, the first case molded in the first molding process is transferred to a second molding machine, and expanded into a toroidal shape.
Belt f141. A green tire is obtained by pasting l-red (151, sidewall 116). The green tire is vulcanized and molded in a mold by heating to 150 to 200°C under pressure. The inner cavity of the hot tire taken out from the mold is filled with compressed air to cool it while applying tension to the carcass cord.

Since the cord is heated to a temperature of 150 to 200'C during vulcanization molding, heat shrinkage stress acts on the cord. Cords whose ends are folded back and fixed around the bead core (I7) have little heat shrinkage during vulcanization and retain their initial high Young's modulus, but cords cut at the cut point at the overlap joint have one end Since it is a free end, it is easily contracted. As shown in Figure 3, the cord that has been heat-sent to the right end of the curve to increase its modulus will undergo residual heat shrinkage (
shrinkage rate) decreases, changes to the leftmost state, and Young's modulus decreases.

The tire taken out of the mold is still kept at a high temperature, so when the carcass cord is no longer under tension after being taken out of the mold, the heat set of the carcass cord is relaxed and the tire cools down to a certain temperature. Meanwhile, the cord with both ends fixed also undergoes heat shrinkage, resulting in a decrease in Young's modulus and a decrease in the tire's maneuverability.

After taking out the tire from the vulcanization mold, the inner cavity of the hot tire is filled with internal pressure air, and while a constant tension is applied to the carcass cord, it is cooled to a temperature at which the cord does not shrink.The Young's modulus of the fixed cord is It is possible to prevent a decrease in

When the inner cavity of the tire is filled with internal pressure air, the tension T (P/d) that acts on the carcass cord is expressed by the following equation.

2Rn e D Here, P゛Internal air pressure (kq/crt?) R, Carcass radius (cm) r, Radius at maximum tire width W (cm) n Number of carcass plies (pcs/cm) e Carcass radius Number of crown center cords (pieces/
am) D code denier number. The pressure of the internal air that is filled into the tire during cooling is adjusted so that the carcass cord tension determined by the above equation (1) is 1 to 6% of the cord strength. When using polyester cord or nylon cord as a carcass cord, make sure that the tension of the cord due to internal pressure is 0.05 to 1 g/d, and heat it at 120°C.
Thereafter, it is preferably cooled to 90°C or less.

When the carcass cord is filled with internally pressurized air and cooled, the Young's modulus of the carcass cord fixed at both ends to the bead core during vulcanization and cooling does not decrease, but the cord cut at the cut section of the lap joint does not decrease. , the Young's modulus decreases due to shrinkage during vulcanization and cooling, and the carcass plies overlap at the lap joint, so even if the number of cords increases, the rigidity of the lap joint is almost the same as other parts. The stiffness of the entire carcass becomes uniform.

(e) Examples Example 1 and Comparative Examples 2 to 4 One ply of nominally 3000 denier polyester cord was used as the carcass ply, and the tire size was 165R13.
Manufactures radial tires. The cord cutting conditions at the overlapped part in the carcass band manufacturing process, the cord cutting conditions in the first molding process, and the tire cooling conditions after vulcanization (abbreviated as PCI) were selected as shown in Table 1, and the tire of the present invention was Tires of Examples and Comparative Examples of the manufacturing method were manufactured, and the height and uniformity (RFV) of the unevenness of the overlapped carcass portion were measured, and the average values of 100 tires are shown in Table 1.

Uniformity is indicated by the RFV PP value measured based on the method of JASOC-607. The unevenness of the overlapping joint portion is indicated by the maximum value of the amount of unevenness of the sidewall measured 24 hours after filling the tire with JIS standard air pressure.

Also, disassemble the tire and check the number of cords and code 1-w.
Table 1 also shows the Young's modulus determined from the measurement of the intermediate elongation when a load of 2.3 y/d was applied. Comparative Example 1 is a tire manufactured by a conventional method.

(Details below) Table 1 Compared to the conventional tire of Comparative Example 1, the tire of the present invention in Example I has greater uniformity and better uniformity due to the cutting portions provided on both end cords of the lap joint. The amount of sidewall unevenness is reduced.

Since the tire of Comparative Example 2 was not cooled by filling with internal pressure air after the completion of vulcanization, the main body cord thermally contracted during cooling, and the difference in Young's modulus with the cord at the lap joint was small, and the sidewall The amount of unevenness is large.

Examples 2 to 4 and Comparative Example 4 Tire size 185 using carcass cord shown in Table 2
/70R14 tires were manufactured. The tire manufacturing conditions were selected as shown in Table 2, the tires were manufactured in the same manner as in Example 1, and the tire uniformity, sidewall irregularities, etc. were measured in the same manner, and the results are shown in Table 2. .

(The following is a blank space) Table 2 (f) Effects of the Invention According to the radial tire manufacturing method of the present invention, the overlapping joints of the carcass ply of the radial tire and the cracking of other parts are almost equal, and the entire carcass ply is Since the rigidity is almost uniform, the uniformity of the tire is improved, and the sidewall has fewer irregularities, making it possible to manufacture a tire with an excellent appearance.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a state in which carcass bands are overlapped and joined in the first molding step of the radial tire manufacturing method of the present invention, and FIG. 2 is a sectional view of the radial tire manufactured by the manufacturing method of the present invention. FIG. 3 is a graph showing the relationship between the dry heat shrinkage rate and Young's modulus of the cord. Explanation of symbols (1), (1)...Cut piece, (2)...Tip, (3) Tip cut part, (4), (45...
Cord, (5)...Bead part, (6)...
・Bead base, (7)...Rim flange, (3)
... Rear end, (9) ... Rear end cut section, αO ...
Cut piece (IQ, 11... code, (I2)
...Tip cut part, (13)...Rear end cut part, α
4)...belt, (15)...tread, (country...
Sidewall, I7)...Bead core, j
181...Carcass ply.

Claims (3)

[Claims] (1) A long carcass material made by using a carcass cord as a warp to form a blind weave and rubberized is cut in the width direction at right angles to the cord or at an angle close to this, and each of the resulting cut pieces is cut into adjacent pieces. A carcass band manufacturing process of forming a long band in which the cords are arranged in the width direction by overlapping and joining the sides parallel to the cords so that 1 to 10 of the pieces and end cords overlap each other; Cut the band to a predetermined length along the cord, and cut both ends of the resulting cut piece from 1 to 1 of the end cord.
1. A first molding step in which 10 pieces are overlapped and joined to form a cylindrical shape, and bead core assemblies are attached to both ends of the cylinder to form a first case. In a tire manufacturing process consisting of a second molding process for inflating and pasting a belt, tread rubber and sidewall rubber, and a vulcanization molding process, the shredded pieces or / And 1 to 10 cords at both ends of the cut piece are cut at one place to make them discontinuous, and the discontinuous cords are overlapped and spliced, and internal pressure air is injected into the inner cavity of the tire after vulcanization. A method for manufacturing radial tires characterized by filling and cooling. (2) Cut the cut piece or cut piece so that the cut point of the end cord of the cut piece or cut piece is located inside the bead part and between the bead base and the height of the rim flange when molded into a tire. A method for manufacturing a radial tire according to claim 1, wherein the cutting position of the end cord is determined. (3) Cut the end cords at both ends of the shredded pieces or cut pieces at one place, and make sure that the cord cutting position at the end of the cut pieces or cut pieces that are overlapped and spliced is on the opposite side to the tire center line. 2. A method for manufacturing a radial tire according to claim 1 or 2, wherein