JPH09277402A - Production of radial tire for heavy load and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance molding workability, quality after vulcanization molding and the durability of a bead part by combining side wall rubber and a rubber chaffer to determine a dividing position on a desk and preliminarily setting rubber members according to this division to first and second composite strip like members. SOLUTION: In molding a tire, a rubber chaffer member is divided into an outside part in the radius direction of the tire and the residual inside part according to the division line at a time when the laminating surfaces of the rubber chaffer member and a side wall rubber member are formed and the cross-sectional shapes of the inside and outside rubber members 5-1, 5-2 corresponding to these parts are determined. Subsequently, side wall rubber is divided according to the division line in the same way and the cross-sectional shapes of the inside and outside rubber members 6-1, 6-2 corresponding to the divided parts are determined. Next, the rubber members 5-1, 6-1 are subjected to extrusion molding and combined to form a first composite strip like member. Succeedingly, the rubber members 5-2, 6-2 are combined in the same way to form a second composite strip like member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a pair of bead portions, a pair of sidewall portions, and a tread portion. These portions are reinforced between bead cores embedded in the bead portion and wound around the bead core. A heavy-load radial including a steel cord radial carcass of 1 ply or more having a folded portion, a rubber chafer arranged at a position outside the bead portion at least in contact with an applicable rim, and a sidewall rubber forming the outside of the sidewall portion. The present invention relates to a tire manufacturing method and a tire by this method, and more particularly to a method for manufacturing a heavy duty radial tire having excellent durability of a bead portion of a tire used for a large vehicle such as a truck-bus, an industrial vehicle and a construction vehicle, and the tire.

[0002]

2. Description of the Related Art Since a heavy duty radial tire is large in size and has a large load, it is apt to cause a bead failure, so a rubber-coated steel cord layer called a wire chafer for the purpose of further reinforcing the bead portion. It is customary to use a bead for the bead portion, and when reinforcement is still insufficient, an additional layer of organic fiber cord is used, and in many cases a nylon cord layer is laminated so that the cords cross each other. Also, the carcass ply is usually made of radial-arranged steel cords in order to keep the heat resistance of the carcass as thin as possible.

A conventional method of manufacturing a heavy duty radial tire including the wire chafer and a reinforcing organic fiber cord layer will be described below in part with reference to FIG. FIG. 4 shows a green case G in which a cylindrical molding drum 10 of a so-called first molding machine and an unvulcanized member (hereinafter simply referred to as a member) are attached to the drum.
It is a partial cross section with c '.

Molding drum 1 when the tire is small to medium size
The green case Gc ′ is directly molded at 0, but in the case of a large size, the inner liner rubber member 8 (a plurality of sheets) is formed in a separate process called band molding before applying the member to the molding drum 10. And a rubber-covered organic fiber cord layer member 29 on the outside thereof and a wire chafer member 30 further on the outside thereof at a predetermined position in advance, the radial carcass ply member 4 being a series of bands. Prepare as a member in advance.

In forming the band, a rubber chafer member is attached to the band member at a position corresponding to the outside of the bead portion that at least comes into contact with the applicable rim when the tire is a product tire. The rubber chafer member is attached to the outside in the radial direction of the tire. This is a rubber member 25-1 excluding the rubber member 25-2 of the rubber chafer portion located, and this rubber member 25-1 is arranged so as to be sandwiched between the inner liner rubber member 8 and the organic fiber cord layer member 29. Keep it.

After the band member is supplied to the forming drum 10, the bead core member 3 and the stiffener rubber members 7-1 and 7 are provided in a state where the folded-back portion 4u of the carcass ply member 4 is narrowed.
-2 and the combined member are pressed and applied to the band member from both sides of the molding drum 10 to be in close contact with each other, and then the band member is folded back around these members 3, 7-1 and 7-2.
Thereafter, if necessary, the members are brought into close contact with each other by stitching means.

Next, the side wall rubber member 26 and the rubber chafer part member 25 attached to the upper surfaces of both ends thereof.
2 or a so-called D / T (dual tuba) extruded rubber member in which the sidewall rubber member 26 and the rubber chafer part member 25-2 are integrally extruded and formed, and each assembled up to that point. Member 4 (4
u), 25-1, 7-1, 7-2 and the like. Also in this case, if necessary, the respective members are brought into close contact with each other by the stitching means to complete the green case Gc '. The laminating process up to this point is called the first molding, and then the green case Gc 'is supplied to the second molding process to expand the diameter, and the belt member and the tread rubber separately bonded to the expanded green case Gc'. Put the members together to make a green tire,
This is vulcanized and molded to obtain a product tire.

[0008]

However, when the wire chafer member 30 is used, this member has a high resilience and thus has a high rigidity, and as a result, the above-mentioned folding workability of the band member is significantly impaired. At times, a large amount of air is accumulated between the members, which may cause defective product tires. In addition to these problems, strain is concentrated at the outer end of the wire chafer in the radial direction of the tire during load rolling of the tire, causing separation failure at this end, or sometimes this separation causes the outside of the wire chafer There is also a disadvantage that the cord of the carcass ply turn-back portion is broken along the end portion. In addition, the use of wire chafers does not meet the ever-increasing demands for weight reduction and cost reduction.

Therefore, in order to avoid the application of the wire chafer and to impart sufficient rigidity to the bead portion, it has been attempted to make the rubber chafer having a high elastic modulus after vulcanization as thick as possible. This thick gauge rubber chafer is provided with a reference numeral 30 in FIG. 4 in order to secure a sufficient thickness and to keep the folding workability in the first molding as good as possible.
A member indicated by t, which is called a hat rubber, is a member having a high elastic modulus and a high hardness after vulcanization, which alleviates the rigidity difference at the end of the wire chafer and also serves to prevent air from entering during the laminating. It is necessary to form a rubber chafer member portion (not shown, corresponding to reference numeral 25-1 in FIG. 4) having a thickness equal to or greater than the sum of the thicknesses of the wire chafer related members 30 and 30t including the above.

As a result, in the first molding, unintentionally, the rubber chafer member corresponding to reference numeral 25-1 in FIG. 4 is too thick, and this rubber material is difficult to adhere to other rubber members when unvulcanized. Due to the nature, the rubber chafer member portion is easily peeled off from the carcass ply member 4,
By increasing the thickness of the sidewall rubber member to compensate for the gauge shortage, a large step portion is formed as a whole,
It was found that there is a problem that vulcanization failure occurs in this step portion.

Next, in the product tire, the height of the rubber chafer having higher elastic modulus and hardness than that of the sidewall rubber should be set as high as possible to sufficiently increase the rigidity of the bead portion. In order to maintain good workability in the first molding, the tire radial inner edge of the sidewall rubber is significantly separated from the bead core radially outward, and the edge portion is sandwiched by a rubber chafer. It becomes necessary to take Therefore, when the durability of the bead portion of the tire having the above-mentioned configuration was confirmed, it was likely that a separation failure would occur early between the rubber chafer and the folded portion along the inner folded portion,
It was found that the durability of this bead portion was not practical because it could not be adapted to the market.

Therefore, the inventions according to claims 1 to 3 of the present invention are based on the premise that the wire chafer is not applied, and advantageously solve all of the above-mentioned manufacturing problems, and the bead portion of the product tire. An object of the present invention is to provide a method for manufacturing a heavy duty radial tire capable of maintaining a high level of durability and the tire.

[0013]

In order to achieve the object of providing a manufacturing method among the above objects, the invention described in claim 1 of the present invention is the manufacturing method described at the beginning, wherein (1) sidewall rubber The unvulcanized rubber member is divided into an inner rubber member corresponding to the inner side portion of the tire in the radial direction and a remaining outer rubber member, and the unvulcanized rubber member of the rubber chafer is divided into an outer rubber member corresponding to the outer side portion in the tire radial direction. Member and the remaining inner rubber member, and at that time, the widthwise cross section of each rubber member is tapered toward the edge, and (2) the inner rubber member of the sidewall rubber member and the inner rubber member of the rubber chafer member are mutually The first composite strip-shaped member is joined together at the end faces, and the outer rubber member of the rubber chafer member is attached to the end face of the outer rubber member of the sidewall rubber member. Combined together under the form of overhangs in the tire radial direction inner side of the arm and the second composite strip,
(3) Under the distribution distribution from the unvulcanized carcass ply member position corresponding to the bead core winding position of the carcass to the inner side and the outer side, on the carcass ply member surface on the side opposite to the subsequent unvulcanized bead core member application side, One composite strip,
The sidewall rubber members are attached to the outside and these members are made into a series of band members. (4) After supplying the band members to the cylindrical molding drum, the unvulcanized bead core member and the stiffener rubber member are provided on both sides of the band member. And the band member is folded back around both the bead core and the stiffener rubber member, and (5) after folding the band member, the front and back surfaces of the sidewall rubber members of the first and second composite belt-shaped members are mutually Then, under the relationship that the front surface and the back surface of the rubber chafer member match each other, a second composite strip member is attached around the band member on the forming drum to form a green case, and (6) then the green case is formed. After expanding the diameter, the unvulcanized belt member and tread rubber member that were separately attached are attached to the expanded green case and And Ntaiya, and characterized by applying vulcanizing this green tire.

In order to achieve the object of providing a tire among the above objects, the invention described in claim 2 of the present invention is the tire described at the beginning, and the above-mentioned items (1) to (6) are included. In the entire region where the rubber chafer made of the first and second composite belt-shaped members and the sidewall rubber are in contact with each other after the vulcanization molding, all of the sidewall rubber is located inside the tire. Occupies a straight line in the tire radial direction, and the inner edge of the sidewall rubber in the tire radial direction is a straight line passing through the outer peripheral surface of the bead core and parallel to the tire rotation axis, and a distance corresponding to the maximum height of the bead core cross section. The rubber chafer and the sidewall rubber have a JIS hardness of 56 to 74 °, respectively. Characterized in that in 囲内.

Good workability is maintained in manufacturing, and in product tires, it contributes rationally to the improvement of bead rigidity required for exhibiting excellent bead durability, and also causes a failure such as a wire chafer. It is advantageous to provide a bead reinforced cord layer without ridges, for which purpose the bead portion is provided with a plurality of organic fiber cord reinforced layers, said reinforced cord layer being provided. Is a line segment located inside the tire inner side carcass ply and connecting the tire radial outer end edge of the reinforcing cord layer and the radius of curvature center of the flange of the applicable rim with respect to a straight line parallel to the tire rotation axis passing through the center. It is effective to set the inclination angle within the range of 65 to 75 °. It is preferable that the plurality of reinforcing cord layers are laminated such that cords intersect each other between adjacent layers, and the laminated reinforcing cord layer member is attached to the carcass ply member during band molding.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a left-hand side sectional view of a heavy duty radial tire according to an embodiment, and FIG. 2 is a right-hand side sectional view of a green case in a first molding step, which is similar to the partial sectional view shown in FIG. FIG. 3 is a cross-sectional view of an integrally extruded member of the inner rubber chafer member and the inner sidewall rubber member.

In FIG. 1, 11 is a pair of bead portions (only one side is shown), 12 is a pair of sidewall portions (only one side is shown), and a tread portion (not shown) is a pair of sidewall portions 12 mutually. It continues in a toroidal shape. 1 ply or more (1 ply in the illustrated example) across the bead cores 13 in which these respective parts are embedded in the bead part 11.
Reinforced with steel cord radial carcass 14 of
The carcass 14 has a folded portion 14 a that is wound around the bead core 13. Applicable rim 20 outside the bead portion 11
The rubber chafer 15 is arranged at an outer position at least in contact with (only a part of the outer contour is shown in the diagram), and the outer side of the sidewall portion 12 is formed by the sidewall rubber 16, and the tire radial direction (hereinafter referred to as the radial direction). ) The inner portion is located between the rubber chafer 15 and the folded portion 14a.

A two-dot chain line L shown in FIG. 1 is a dividing line (actually a dividing surface) when forming a bonding surface between a rubber chafer member and a sidewall rubber member in tire molding. In order to determine the specifications of each rubber member, the rubber chafer 15 is first divided into a radially outer portion 15-2 and a remaining inner portion 15-1 according to the dividing line L. Hereinafter, also referring to FIG. 2, the cross-sectional shape of the outer rubber member 5-2 corresponding to the outer portion 15-2 and the inner rubber member 5 corresponding to the remaining inner portion 15-1 will be described.
−1 cross-sectional shape is determined.

Next, similarly to the above, along the dividing line L, the sidewall rubber 16 is attached to the inner portion 16-1 in the tire radial direction.
And the remaining outer portion 16-2. Next, the sectional shape of the inner rubber member 6-1 corresponding to the inner portion 16-1 and the outer rubber member 6 corresponding to the remaining outer portion 16-2.
-2 cross-sectional shape is determined. Rubber members 5-1 and 5-2
When determining the cross-sectional shape of each of the rubber members 6-1 and 6-2, it is important to taper the cross-section in the width direction of each rubber member toward the edge.

After determining the cross-sectional shape of each rubber member, the rubber chafer inner rubber member 5-1 and the sidewall rubber inner rubber member 6-1 are extruded and molded by an extruder, and the inner rubber members are combined to form the first rubber member. It is a composite strip. At this time, the strip-shaped members are the rubber members 5-1 and 6 extruded separately.
-1 may be obtained by laminating each rubber member to each other at the time of subsequent band molding or before band molding,
It is advantageous in terms of productivity and quality to use a composite rubber member that is integrally extruded by D / T (dual tuba) in advance. FIG. 3 shows an example of the cross-sectional shape in the width direction of the first composite strip-shaped member by D / T extrusion. As is clear from FIG. 3, each of the members 5-1 and 6-1 has a tapered shape toward both ends in the width direction.

Then, similarly to the above, the sidewall rubber outer rubber member 6-2 and the rubber chafer outer rubber member 5-2 are combined to form a second composite strip member. Also at this time, the belt-shaped members are the rubber members 6-2 and 5-2 extruded separately.
It is also possible to obtain them by the subsequent first molding or by laminating them together before the first molding, but it is also advantageous from the viewpoint of productivity and quality to extrude integrally by D / T beforehand. Is. The second composite strip by D / T extrusion is also shown in FIG.
Like the members 5-1 and 6-1 shown in FIG.
2 has a tapered shape toward both ends in the width direction.

Next, in the first molding step showing the cross section of the right side portion in FIG. 2, when the members are attached to each other to obtain the green case Gc, the parts denoted by the same reference numerals as those in FIG. 4 are the same members,
In the embodiment of the present invention, when the band member is molded by a band molding machine (not shown), the first composite strip-shaped member 5 -1, 6-1 are sandwiched between both ends of the inner liner rubber member 8 and the organic fiber cord reinforcing layer member, for example, the nylon cord reinforcing layer member 9 and bonded. In this bonding, the sidewall rubber inner rubber member 6-1 is set to the outer side.

The positions at which the first composite strip members 5-1 and 6-1 are bonded together by band forming are inside and outside the position of the carcass ply member 4 corresponding to the winding position of the bead core 13 of the carcass 14 in the product tire. The carcass ply member on the side opposite to the pressing contact side of the bead core member, which corresponds to the vicinity of the position where the bead core member is pressed and closely contacted during the subsequent first molding. 4 surfaces.

The band member completed as described above is supplied to the molding drum 10, and the bead core member 3 and the stiffener rubber member 7-1, which are pressed and closely attached to the supplied band member,
After folding the band member around the united member with 7-2, the second composite strip members 5-2 and 6-2 are attached to the band member. At that time, as shown in FIG. 2, the front surface of the sidewall rubber inner rubber member 6-1 of the first composite belt-shaped member and the back surface of the sidewall rubber outer rubber member 6-2 of the second composite member are joined to each other at the joining line La. The rubber chafer inside rubber member 5 of the first composite belt-shaped member, which coincides with each other at the (bonding surface La),
It is necessary that the front surface of No. 1 and the back surface of the rubber chafer outer rubber member 5-2 of the second composite member coincide with each other at the joint line Lb (joint surface Lb).

In other words, when the second composite strip members 5-2 and 6-2 are attached to the band member, the rubber member 6 becomes the inner portion 16-1 of the sidewall rubber 16 in the tire.
-1, and the rubber member 6-2 that becomes the remaining outer portion 16-2
And the radially outer portion 1 of the rubber chafer 15
The rubber member 5-2 to be 5-2 and the remaining inner portion 15-
The second composite strip-shaped member is stretched around the band member in such a manner that the rubber member 5-1 which becomes No. 1 is matched with each other and the continuity of smoothly connecting as the sidewall rubber 16 and the rubber chafer 15 is provided. Together, the green case Gc is molded.

That is, the mutual joining surface between the rubber member 5-1 of the first composite belt member and the rubber member 5-2 of the second composite member, and the rubber member 6-1 of the first composite belt member.
That is, the mutual joint surfaces of the second composite member and the rubber member 6-2 are substantially on the same surface without being displaced. Then, if necessary, stitching is performed to finish the green case Gc. After the vulcanization molding, the line La,
Lb becomes one division line L shown in FIG.

Under such a molding method, even if the thickness of the rubber chafer member is set to be considerably large, this does not cause a step around the rubber chafer member that would cause a defective product during the first molding. , A relatively smooth surface can be formed. Further, in the folding operation of the first molding step, the rubber chafer member, which is disadvantageous in the adhesion to other rubber members, is used as the inner rubber member 5-1 and the inner chamfer member 5-1 is stopped in the lower portion where peeling between the members is unlikely to occur, while peeling easily occurs. Since the side wall rubber inner rubber member 6-1 having a high adhesiveness between the rubber members is arranged in the upper portion, there is no peeling between the rubber members which have been once adhered and joined, so that there is no air trapped portion. Can be

Further, without any trouble, the width of the rubber chafer outer rubber member 5-2 can be further widened by a desired thickness gauge, whereby the radial outside position of the rubber chafer 15 in the tire can be increased by the thickness gauge. It becomes possible to do. Further, as in the conventional case, the outer side in the radial direction of the rubber chafer in the tire is bifurcated, the rubber member portion corresponding to one of the branched rubber chafer portions is brought into contact with the folded portion 4u of the carcass member 4, and the bifurcated portion of the rubber chafer member is bifurcated. It is not necessary to form a complicated sandwich structure in which the inner end portion of the sidewall rubber member is sandwiched in the recessed portion, and the bead portion durability is not so improved in the complicated structure. According to one embodiment, by freely changing the position of the dividing line L shown in FIG. 1, it is possible to freely select the inner end of the sidewall rubber 16 in the tire at an optimal position for improving the durability of the bead portion 11. You can

The green case G completed in this way
According to the convention, c is expanded in the second molding step, and a belt member and a tread rubber member that are pre-bonded to the expanded green case Gc are applied to form a green tire, and the green tire is vulcanized and molded. Product tires. When the tire becomes a product tire, the sidewall rubber 16 extends in contact with the folded portion 14u of the carcass 4, and the tire radial inner edge S _E of the sidewall rubber 16 has an outer periphery of the bead core 13 as shown in FIG. Between a straight line B ₁ passing through the surface and parallel to the tire rotation axis (not shown), and a position (the straight line B ₂ ) radially separated from the straight line B ₁ by a distance H corresponding to the maximum height y of the bead core. Must exist Also, the rubber chafer 15 and the sidewall rubber 1
The JIS hardness of 6 is within the range of 56 to 74 °.

The relative position of the inner edge S _E of the sidewall rubber 16 with respect to the outer periphery of the bead core 13 is set as described above, and the rubber chafer 15 and the sidewall rubber 1 are arranged.
By setting the JIS hardness of 6 within the above range, the bead portion 1
The durability of No. 1 is further improved. The inner portion 15-1 and the outer portion 15-2 of the rubber chafer 15 have almost the same physical properties after vulcanization, in addition to the rubber having the same composition, and the above J
Different compounding compositions may be used as long as the rubber is within the IS hardness range. This is the inner part 1 of the sidewall rubber 16.
This is also the case for 6-1 and outer portion 16-2. Although not shown, the tire according to the present invention is provided with a belt having two or more steel cord intersecting layers and a tread rubber on the outer periphery thereof, as described above, and these and the carcass 14 are combined to form a tread portion. It is customary to construct.

In addition to the above-described structure, the tire is sandwiched between the carcass 14 constituting the main body of the carcass, that is, the main body of the carcass 14 which is continuous in a toroidal shape between the bead cores 13 on the inner side of the tire, and the folded-back portion 14a. 13 has a stiffener rubber 17 extending along the carcass 14 toward the outer side in the tire radial direction.
Is a hard stiffener rubber 17-1 extending from above the bead core 13 along the body of the carcass 14 and a soft stiffener rubber 17-2 extending along the folded portion 4a and the body of the carcass 14.
According to the conventional practice, is composed of a part of strengthening of the bead portion 11. The inner surface of the tire is covered with an air impermeable inner liner rubber 18.

The tire of the illustrated example has a two-layer rubber-coated organic fiber core disposed inside the carcass 14 inside the tire.
The bead portion 11 is provided with a cord reinforcing layer, for example, two layers of nylon cord reinforcing layer 19. The cords of the reinforcing layer 19 intersect each other between adjacent layers and are 30 to 40 ° with respect to the circumference of the bead portion 11.
It becomes an inclined array. The organic fiber cord reinforcing layer 19 is bonded to the inner liner rubber member 8 described above with reference to FIG. 2 by sandwiching the first composite belt-shaped members 5-1 and 6-1 between the end portions. It corresponds to an organic fiber cord reinforcing layer member, for example, a nylon cord reinforcing layer member 9.

Here, the outer edge P of the nylon cord reinforcing layer 19 in the radial direction and the outer rim 20 and the applicable rim 20 showing the outer contour line are shown.
Segment M connecting the center C of the radius of curvature R of the flange 20F of
The inclination angle θ with respect to the straight line N passing through the center C of the radius of curvature and parallel to the tire rotation axis (not shown) is 65 to 75 °.
Within the range, the bead portion is advantageously reinforced without causing a failure in the reinforcing layer 19 itself, and the durability of the bead portion 11 is greatly improved.

As a result of the bead portion 11 flexing toward the outside of the tire under the load, tension acts on the inside of the tire of the carcass 14 body, and hence the nylon cord reinforcing layer 19 composed of the cord crossing layer. It has been clarified that the tension acts to effectively utilize the cord rigidity that cannot be obtained under compression and helps to improve the rigidity of the bead portion, but on the other hand, if the proper arrangement is neglected, failures such as cord breakage and separation occur. Therefore, using FEM (Finite Element Method) that is effective in clarifying the actual state of failure, the cross-sectional shear strain of the radially outer end portion of the nylon cord reinforcing layer 19 (due to the bending of the bead portion to the side wall portion under load) As a result, the shear strain tends to decrease once the value of the inclination angle θ increases, and the inclination angle θ is 65 to 75 °.
In the range of, the minimum value or a value close to this value is shown, but it was found that when the tilt angle θ is increased beyond this upper limit angle, the shear strain starts to increase again.

That is, even if the inclination angle θ is less than 65 ° or exceeds 75 °, the shear strain becomes too high in any case, and the action of this high shear strain causes the nylon cord reinforcing layer 19 to end radially outward. It was found that there is a problem that a cord break failure occurs in the part. The relationship between the inclination angle θ and the shear strain is shown as a diagram in FIG. .

[0036]

EXAMPLE An off-the-road radial ply tire according to the above-described manufacturing method, having a size of 14.00R2.
5, the construction is in accordance with FIG. 1, the manufacturing method is in accordance with FIGS. 2 and 3, the carcass 14 is one ply of the radial array steel cord, the folded portion 14u is so-called high turn-up, and this end is near the tire maximum width. Extend to. The belt is composed of four steel cord layers, and four layers are cord intersecting layers.

Two layers of nylon cord reinforcing layers 19 were applied along the inner surface of the carcass 14 facing the inside of the bead portion 11 for reinforcing the bead portion. Radial outer end outer corner P of the reinforcing layer 19 and the radius of curvature center C of the flange 20F.
The inclination angle θ of the line segment M connecting between and with respect to the straight line N passing through the center C of the radius of curvature is 70 °. The inclination angle of the cord in each layer of the reinforcing layer 19 with respect to the circumferential line of the bead portion was about 35 ° on average.

The dividing line (dividing surface) L between the rubber chafer 15 and the sidewall rubber 16 is as shown in the figure, and the inner edge S _E of the sidewall rubber 16 is approximately the maximum height y = H = 18 mm of the bead core 13. 9.5 equivalent to 50%
mm, and this value was the average value of the entire circumference. The appearance of the molded member was smooth with no large irregularities in the vicinity of the bead, and the tire after vulcanization and molding had a good appearance and anatomical results as intended.

The JIS hardness of each rubber after vulcanization molding is as follows. Rubber chafer 15 (15-1, 15-2); 68 °, sidewall rubber 16 (16-1, 16-2); 61
Hard stiffener rubber 17-1; 80 °, soft stiffener rubber 17-2; 62 °.

In order to confirm the durability of the bead portion of the tire of the embodiment, the tire of Conventional Example 1 which is the same as the embodiment except that it has a nylon chafer member 29 and a wire chafer member 30 shown in FIG. 4, and a bead portion reinforcing chafer. A rubber chafer of the same JIS hardness having the same thickness and height as that of the embodiment is applied without using any of the above, except that the inner side edge portion of the sandwich portion is sandwiched by the rubber chafer at the tire radial inner end of the sidewall rubber. A tire of Conventional Example 2 in which was directly contacted with the folded portion was manufactured.

A BF (Bead Fatigue) endurance test using a drum was conducted using the example tires and the conventional example tires 1 and 2 as test tires. In this BF test, the bead portion is exclusively loaded by the high internal pressure filling and the high load of the tire to cause the bead portion to fail, and it is an effective method for reproducing the bead portion failure in the market. The evaluation of the test was based on the running time until a failure occurred in the bead portion, the failure level (degree of failure) and the failure content at the end of the test due to the failure occurrence.

Each of the running time and the failure level is represented by an index with the tire of Conventional Example 1 being 100, and the larger the value, the better. As a result, regarding the running time, the tire of Conventional Example 2 stayed at 105, whereas the tire of Example Example had 120, and the failure level of the tire of Conventional Example 2 was 110, while that of Example tire reached 130. ing. Regarding the details of the failure, the tire of Conventional Example 1 is a failure in which the separation generated from the end of the wire chafer spreads between the carcass and the sidewall rubber and eventually bursts. A significant separation occurred between the rubber chafer and the folded portion of the carcass, which spread over a wide area along the folded portion, whereas in the example tire, there was a slight separation between the rubber chafer and the folded portion of the carcass. However, it has been demonstrated that sufficient bead portion durability can be exhibited without using a wire chafer.

In addition to the actual bead portion durability test described above, the inclination angle θ of the line segment M with respect to the straight line N is used as a desktop evaluation.
And the cross-sectional shear strain acting on the vicinity of the radially outer end of the nylon cord reinforcing layer, and further by the FEM model, the radial ply tire, the size of the off-the-road tire of another embodiment (according to FIGS. 1 and 2). Conducted for 17.5R25. JATMA YEAR BOOK (19
When the air pressure corresponding to the maximum load capacity defined by the 1996 edition) is filled and the load corresponding to the maximum load capacity is assumed, the reciprocal of the shear strain level when the inclination angle θ is 60 ° is 100. Inclination angle θ
Was found to be 179 at 70 ° and 95 at an inclination angle θ of 80 °. Of course, the larger the value, the smaller the shear strain.

[0044]

According to the first to third aspects of the present invention, the wire chain that impairs workability during manufacturing, is disadvantageous in cost and tire weight, and tends to trigger a separation failure. When the fa was removed, the tire quality after vulcanization molding and the durability of the bead part were conventionally impaired, which was lacking in practicality, whereas the sidewall rubber and the rubber chafer were put together on the desk. By determining the dividing position and preliminarily forming the rubber member according to this division into the first and second composite belt-shaped members, the molding workability and the quality after vulcanization molding are highly improved, and at the same time, the durability of the bead portion is improved. It is possible to provide a method for manufacturing a radial tire for heavy load, which can be more significantly improved, and the tire.

[Brief description of drawings]

FIG. 1 is a sectional view of essential parts of a heavy duty radial tire according to the present invention.

FIG. 2 is a sectional view of a main part of a member on a first forming drum of a heavy duty radial tire according to the present invention.

FIG. 3 is a sectional view of a first composite strip member according to the present invention.

FIG. 4 is a sectional view of a main part of a member on a first molding drum of a conventional heavy duty radial tire.

FIG. 5 is a diagram showing a relationship between an inclination angle of a line segment M with respect to a straight line N and a sectional shear strain.

[Explanation of symbols]

3 Bead core member 4 Carcass ply member 4u Folding part 5-1 Rubber chafer inner rubber member 5-2 Rubber chafer outer rubber member 6-1 Sidewall rubber inner rubber member 6-2 Sidewall rubber outer rubber member 7-1, 7-2 Stiffener Rubber member 8 Inner liner rubber member 9 Organic fiber cord layer member 10 First forming drum 11 Bead portion 12 Side wall portion 13 Bead core 14 Carcass 14u Folding portion 15 Rubber chafer 15-1 Rubber chafer inner portion 15-2 Rubber chafer outer portion 16 Side Wall rubber 16-1 Side wall rubber inner part 16-2 Side wall rubber outer part 17, 17-1, 17-2 Stiffener rubber 18 Inner liner rubber 19 Organic fiber cord reinforcing layer 20 Rim 20F Flange Gc Green case L Dividing line (dividing surface) La, Lb Joining line (joining surface) S _E Side wall rubber inner edge y Bead core maximum height H Height equal to bead core maximum height C Flange radius center P Organic fiber core -Radial outer end of the reinforcement layer Outer corner θ Angle of inclination of the line segment M with respect to the straight line N

Claims (3)

[Claims] 1. A pair of bead portions, a pair of sidewall portions, and a tread portion, each of which is reinforced between bead cores embedded in the bead portion and has a folded portion wound around the bead core. A steel cord radial carcass of ply or more, a rubber chafer arranged at a position at least in contact with an applied rim on the outside of the bead portion, and a method for manufacturing a heavy load radial tire including a sidewall rubber forming the outside of the sidewall portion, (1) The unvulcanized rubber member of the sidewall rubber is divided into an inner rubber member corresponding to the radially inner part of the tire and the remaining outer rubber member, and the unvulcanized rubber member of the rubber chafer is separated from the tire radial outer side. The outer rubber member corresponding to the part and the remaining inner rubber member are divided into two parts. The widthwise cross-section of the member is tapered toward the edge, and (2) the inner rubber member of the sidewall rubber member and the inner rubber member of the rubber chafer member are joined together at their end faces to form a first composite strip member. And the outer rubber member of the rubber chafer member is joined to the end surface of the outer rubber member of the sidewall rubber member in the tire radial direction inner side of the sidewall rubber so as to form a second composite strip member, ) Under the distribution distribution from the unvulcanized carcass ply member position corresponding to the bead core winding position of the carcass to the inner side and the outer side, the first surface of the carcass ply member opposite to the subsequent unvulcanized bead core member application side A composite strip,
The side wall rubber member is attached to the outside and these members are made into a series of band members. (4) After supplying the band member to the cylindrical molding drum, the unvulcanized bead core member and the stiffener rubber member are provided on both sides of the band member. The band member is folded back around both the bead core and the stiffener rubber member. (5) After the band member is folded back, the front and back surfaces of the sidewall rubber members of the first and second composite belt-shaped members are mutually Then, under the relationship that the front and back surfaces of the rubber chafer member match each other, a second composite strip member is attached around the band member on the forming drum to form a green case, and (6) then the green case is attached. After inflating the diameter, attach the unvulcanized belt member and tread rubber member that were separately attached to the expanded green case. And lean tire manufacturing method of a heavy duty radial tire characterized by performing vulcanization molding to the green tire. 2. A pair of bead portions, a pair of sidewall portions, and a tread portion, each of which is reinforced between bead cores embedded in the bead portion, and has a folded portion wound around the bead core. A heavy-load radial tire comprising a steel cord radial carcass of ply or more, a rubber chafer arranged at a position outside the bead portion at least in contact with an applicable rim, and a sidewall rubber forming an outside portion of the sidewall portion. (1) to (6) described above, and after vulcanization molding, the rubber chafer made of the first and second composite belt-shaped members and the sidewall rubber are in contact with each other in all regions. All of the sidewall rubber occupies the inside position of the tire and is smoothly connected in the tire radial direction. The inner side edge of the sidewall rubber in the radial direction of the tire is separated from the straight line passing through the outer peripheral surface of the bead core and parallel to the tire rotation axis by a distance corresponding to the maximum height of the bead core cross section in the outer side in the radial direction from the straight line. Being present between the position and the rubber chafer and sidewall rubber JIS
A heavy-duty radial tire having a hardness within a range of 56 to 74 °. 3. The bead portion is provided with a plurality of organic fiber cord reinforcing layers, the reinforcing cord layers are located inside the carcass ply on the tire inner side, and the tire radial outer end edge of the reinforcing cord layers and the applicable rim. The tire according to claim 2, wherein the inclination angle of a line segment connecting the center of the radius of curvature of the flange with respect to a straight line parallel to the tire rotation axis passing through the center is within the range of 65 to 75 °.