JPH10193472A - Production of pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a pneumatic tire reduced in its production cost and constituted so as to obtain high uniformity and high speed durability. SOLUTION: A carcass layer 5 is provided between a pair of left and right bead parts 7 and a belt layer 10 is arranged on the outer periphery of the carcass layer 5 to preliminarily mold a vulcanized or unvulcanized base tire 1. A vulcanized or unvulcanized endless annular tread 2 having a tread pattern applied to the outer peripheral surface thereof is preliminarily molded and strip-like unvulcanized rubber 13 is wound around the outer peripheral surface of the base tire 1 a plurality of times to form an adhesive layer 3 and an endless annular tread 3 is fitted to the adhesive layer 3 to form a fitted object 15 and the unvulcanized part of the fitted object 15 is subsequently vulcanized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a pneumatic tire, and more particularly, to a method for manufacturing a pneumatic tire which is capable of reducing manufacturing costs and obtaining a high degree of uniformity and high-speed durability. About the method.

[0002]

2. Description of the Related Art In general, a pneumatic tire that is marketed as a new tire is formed by laminating unvulcanized tire components, forming a green tire, placing the green tire in a mold, and vulcanizing the tire. Being manufactured. At the time of vulcanization molding by this mold, a tread pattern composed of a complicated groove designed to have a required performance according to the application of the tire is formed on the tread surface. Examples of the tread pattern include a rib pattern suitable for traveling on a good road, a block pattern excellent in traction, a lug pattern suitable for traveling on a bad road, and a studless pattern suitable for traveling on ice and snowy roads.

As described above, conventionally, it is necessary to prepare a dedicated mold for each tire type in which a specific tread pattern corresponding to the required characteristics is carved. Therefore, as the number of types of tread patterns increases, the mold cost increases. Was growing. In addition, since the vulcanization time is substantially determined by the thickness of the thickest shoulder portion of the tire, the vulcanization of the shoulder portion is completed even though the other portions have already been vulcanized. It is necessary to continue vulcanization until the end of this, which has been a factor of reducing the productivity and physical properties of the tire.

[0004] Further, the conventional tire is formed by cutting an unvulcanized rubber strip, which is continuously extruded in a strip shape, into the length of the tread of the tire and joining the ends thereof. In some cases, the joints may be excessive or insufficient due to dimensional errors, which lowers the uniformity of the tire, and the lower uniformity lowers the high-speed durability.

As a countermeasure against such a decrease in uniformity, a tread cap and a belt layer are integrally vulcanized and formed in advance in an annular shape, and the annular tread is fitted into a pre-vulcanized and formed base tire. Has been proposed. However, in the above manufacturing method, a band-shaped bonding rubber sheet is used to bond the pre-vulcanized toroidal tread and the base tire to each other, or a band-shaped bonding rubber sheet is used to cover the end of the joint surface between the two. For the purpose of using the rubber sheet for coating, these rubber sheets cannot adhere to a base tire or an annular tread having a radius of curvature, and cause wrinkles or air pockets. There was a problem that the high-speed durability was not necessarily improved to a sufficiently satisfactory level.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a pneumatic tire capable of reducing production costs and obtaining high uniformity and high-speed durability. .

[0007]

According to a method of manufacturing a pneumatic tire of the present invention for achieving the above object, a carcass layer is mounted between a pair of left and right bead portions, and a belt layer is provided around the outer periphery of the carcass layer. While pre-molding the placed vulcanized or semi-vulcanized base tire, the vulcanized or semi-vulcanized endless annular tread having a tread pattern molded on the outer peripheral surface is pre-formed, and the outer peripheral surface of the base tire is formed. A plurality of strip-shaped unvulcanized rubbers are wound around to form an adhesive layer, and the endless annular tread is fitted thereon to form a fitted body, and then the unvulcanized portion of the fitted body is vulcanized. It is characterized by being sulfurized.

In another method of manufacturing a pneumatic tire according to the present invention, a carcass layer is mounted between a pair of right and left bead portions.
While pre-molding a vulcanized or semi-vulcanized base tire having a belt layer disposed on the outer periphery of the carcass layer, a vulcanized or semi-vulcanized endless annular tread having a tread pattern molded on the outer peripheral surface is preliminarily formed. Molded and fitted with the endless annular tread via an adhesive layer made of unvulcanized rubber on the outer periphery of the base tire to form a fitted body, and along the end of the joining surface between the base tire and the tread. Forming a coating layer by wrapping at least one round of unvulcanized rubber in the form of a strip, and then vulcanizing the unvulcanized portion of the fitting body with at least a mold in contact with the coating layer. It is assumed that.

In this manner, the vulcanized or semi-vulcanized base tire and the endless annular tread are formed in advance, and the unvulcanized rubber extruded in a strip shape in order to bond the two tires in the tire circumferential direction. Since the coating layer is formed by wrapping a plurality of turns, the coating layer covering the ends of the joining surfaces of both is also formed by stripping at least one unvulcanized rubber extruded in a strip shape.
Since the tire is formed by being wound around the tire, even if the tire member has a radius of curvature, it can be formed in a layered form without wrinkles or air pockets, and tire defects due to these can be reduced.

In addition, the molding die may be a local one in which a predetermined tread pattern is preliminarily molded for the tread, and the base tire side can be used in common for a plurality of types of treads. Accordingly, the overall cost of the mold can be greatly reduced. Further, since the base tire and the tread are separately vulcanized and formed, it is possible to set an optimum vulcanization time for each of them. That is, when performing vulcanization molding of the entire tire, the thickness of the shoulder portion substantially determines the length of vulcanization time. It was necessary to continue vulcanization until the vulcanization of the part was completed, which resulted in waste of energy and local deterioration of physical properties. By doing so, the vulcanization time can be effectively shortened, and the productivity can be improved. Therefore, the reduction of the mold cost and the improvement of the productivity can be combined with each other to greatly reduce the tire manufacturing cost.

Further, since the tread is formed in an endless annular shape, there is no joint in the tire circumferential direction,
The uniformity and high-speed durability of the tire can be improved, and the uniformity and high-speed durability can be further enhanced because there is no influence from wrinkles or air accumulation in the adhesive layer and the coating layer. In the present invention, the preformed tire and tread may be in a semi-vulcanized state. As this semi-vulcanized state, 80% of full vulcanization
It is preferable to proceed as described above. Thus, vulcanization is 80
% Or more, the shapes of the base tire and the tread are maintained, so that it is not necessary to mold the tread pattern at the time of vulcanizing the unvulcanized portion of the fitted body. In addition, the vulcanization time of the preformed tire and tread can be further reduced by stopping the vulcanization of the base tire and the tread in a semi-vulcanized state in consideration of the vulcanization time of the adhesive layer or the coating layer. It is possible.

Further, a coating layer covering the end of the joining surface between the base tire and the tread is not always necessary,
Since a step is likely to occur at the end of the joining surface between the base tire and the tread, the appearance can be improved by covering the step with a coating layer. Further, at the time of the final vulcanization, this coating layer can be made to correspond to the design such as white side, with rim protect bar, black letter and the like with high accuracy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 illustrates a pneumatic tire manufactured by the manufacturing method of the present invention. In FIG. 1, an endless annular tread 2 is adhered to an outer peripheral surface of a base tire 1 via an adhesive layer 3, and a joint between the base tire 1 and the tread 2 is formed by a coating layer 4.
Covered by

In the base tire 1, the carcass layer 5 is mounted between a pair of left and right bead portions 7 through a central tread portion 6, and both end portions of the carcass layer 5 are wound around a pair of left and right bead cores 8 respectively. It is folded back from the inside of the tire to the outside. The carcass layer 5 has a structure in which reinforcing cords made of organic fiber cords are oriented in the radial direction. A bead filler 9 made of hard rubber is arranged on the outer peripheral surface of the bead core 8, and the bead filler 9 is wound around both ends of the carcass layer 5 together with the bead core 8.

In the outer peripheral portion of the carcass layer 5 of the tread portion 6, a two-layer belt layer 10 in which reinforcing cords made of steel cords are arranged so as to be inclined with respect to the tire circumferential direction is embedded. The reinforcing cords of the two belt layers 10 are oriented so as to be inclined at an angle of 15 to 60 ° with respect to the tire circumferential direction, and are arranged so as to cross each other between the layers. A belt cover layer 11 for protecting the belt layer 10 is laminated on the outer peripheral side of the belt layer 10. On the other hand, a tread pattern including a plurality of main grooves 12 extending in the tire circumferential direction is formed on the tread surface of the tread 2.

Next, a method for manufacturing the above-described pneumatic tire will be described. First, the base tire 1 and the tread 2 are separately vulcanized and formed in advance. That is, after winding the tire material such as the carcass layer 5, the central portion in the width direction is expanded into a cylindrical shape to deform the cross section into a horseshoe shape, and the belt layer 1
Then, the unvulcanized base tire 1 is molded by inserting the unvulcanized base tire 1 into a mold and vulcanized. Since the base tire 1 may be a curved surface having no groove on the outer peripheral surface, a mold having a relatively simple structure can be used. Further, the vulcanization of the base tire 1 may be completely performed, or may be stopped in a semi-vulcanized state of maintaining the shape.

On the other hand, the tread 2 is obtained by filling an unvulcanized rubber into a ring-shaped precured tread mold and vulcanizing and molding the same to obtain an endless annular precured tread having no joint. During the vulcanization, a predetermined tread pattern is formed on the tread surface of the endless annular tread 2 by the groove forming bone formed on the tread forming surface of the mold.

FIG. 2 shows an example of a pre-cured tread mold. The tubular cores 21 and 22 are combined with each other to be integrated. A pair of outer dies 23 and 24 forming a split mold are combined on the outer peripheral side of the cores 21 and 22, and an endless annular cavity 25 is formed between the cores 21 and 22 and the outer dies 23 and 24. It is supposed to be. Each of the outer dies 23 and 24 has a grooved bone 26, and a predetermined tread pattern is formed by the grooved bone 26.

In the mold configured as described above, the unvulcanized tread rubber 27 is injected and filled into the cavity 25 with the mold closed, and the entire mold is heated to vulcanize the tread rubber 27. Thus, an endless annular tread 2 can be obtained. As shown in FIG. 3, while the cores 21 and 22 are rotated with the mold opened, the unvulcanized rubber 29 is extruded from the extruder 28 onto the outer peripheral surface thereof.
May be extruded in a strip shape and wound around a plurality of times to form the tread rubber 27, and then the outer dies 23 and 24 may be closed, and the tread rubber 27 may be vulcanized in the same manner as described above.

In any case, since the tread 2 is composed of only the tread rubber 27, it can be easily formed into an endless annular shape having no joint by injection molding or extrusion molding. In particular, when the unvulcanized rubber 29 is extruded from the extruder 28 in a strip shape to form the tread rubber 27, two or more extruders 28 are used, and the type of tread 2 in the thickness direction or width direction is used. By winding a different unvulcanized rubber 29, higher tire performance can be obtained. The tread 2 may be completely vulcanized or may be stopped in a semi-vulcanized state that maintains the shape.

The extruder 28 may be a continuous extruder in which rubber is continuously extruded by rotating a screw rod inserted in the cylinder, or a fixed amount of rubber is supplied by a piston sliding in the cylinder. It is an injection extruder that is extruded, or the cylinder has a double structure, the rubber rod is supplied between the cylinders of the double structure by rotating the screw rod in the inner cylinder, and this inner cylinder is slid against the outer cylinder. The rubber may be extruded by being moved.

The base tire 1 and tread 2 separately prepared as described above are then subjected to a joining process as illustrated in FIGS. 4A and 4B. First, as shown in FIG. 4 (A), the unvulcanized rubber 13 is extruded from an extruder 28 into a strip shape on the outer peripheral surface of the base tire 1 while rotating the base tire 1 around the tire rotation axis. Is wound a plurality of times in the tire circumferential direction to form the adhesive layer 3. Next, FIG.
As shown in (B), the endless annular tread 2 is fitted to the outer peripheral surface of the base tire 1 with the adhesive layer 3 interposed therebetween to form the fitted body 15.

Next, the fitting body 15 assembled as described above is subjected to a heating step. The vulcanization of the fitting body 15 is performed by inserting the fitting body 15 into an airtight envelope 16 and depressurizing the interior of the envelope 16 through a valve 17 as illustrated in FIG. Then, the base tire 1 and the tread 2 may be heated in a state where they are in close contact with each other. The adhesive layer 3 is vulcanized by this heating, and when the base tire 1 and the tread 2 are in a semi-vulcanized state, the vulcanization of these is also completed. As described above, the vulcanizing step of the fitting body 15 only requires the base tire 1 and the tread 2 to be in close contact with each other, so that there is no need to use a molding die. The envelope 16 is formed from a flexible sheet such as a heat-resistant resin film, a resin, or a rubberized cloth.

On the other hand, FIGS. 6A and 6B show a joining process of the base tire 1 and the tread 2 according to another embodiment of the present invention. In this step, for example, FIG.
As shown in (B), after fitting the endless annular tread 2 to the outer peripheral surface of the base tire 1 to assemble the fitting body 15, it is extruded over the end of the shoulder between the base tire 1 and the tread 2 at the joint surface. The unvulcanized rubber 14 is extruded in a strip shape from the machine 28, and the unvulcanized rubber 14 is wound at least once around the tire circumferential direction to form the coating layer 4.

The fitting body 15 obtained as described above is then subjected to a vulcanization step. In this case, the fitting body 15 is vulcanized while a mold for molding is applied to at least the surface of the coating layer 4. In the above-mentioned mold, characters and patterns can be stamped on the coating layer 4, and a pattern can be provided at the joint between the base tire 1 and the tread 2 to improve the appearance. The mold of the fitting body 15 may have a simple structure for forming the covering layer 4.

The coating layer 4 can also be used as a medium for applying a white side, a rim protect bar, a black letter and the like to the base tire 1 as necessary.
Such setting of the coating layer 4 can be easily performed by using the extruder 28, and automation is easy. According to the manufacturing method of the present invention described above, a vulcanized or semi-vulcanized base tire 1 and an endless annular tread 2 are prepared in advance, and an adhesive layer 3 for bonding the two is extruded in a strip shape. Since the vulcanized rubber 13 is formed so as to circulate, and the coating layer 4 covering the joint between the two is formed so as to circulate the unvulcanized rubber 14 extruded in a strip shape, so that the base tire 1 or tread is formed. Even if 2 has a radius of curvature, wrinkles and air pockets do not occur in the adhesive layer 3 and the coating layer 4. Therefore, the adhesive layer 3 and the covering layer 4
The tire failure resulting from the provision can be reduced.

In addition, since a die for a base tire can be used in common with a plurality of types of tread die having different tread patterns and the like, die costs can be greatly reduced. Further, since the base tire 1 and the tread 2 are separately vulcanized and formed, it is possible to set an optimum vulcanization time for each of them. That is, for the base tire 1, the vulcanization time is set based on the thickness of the thickest portion (for example, the bead portion 7), and the tread 2 is also set based on the thickness of the thickest portion. Vulcanization time can be set. Thereby, the vulcanization time of the base tire 1 and the tread 2 can be effectively shortened, and the productivity can be improved.

Furthermore, since the tread 2 is formed in an endless annular shape and has no joint in the tire circumferential direction, it is possible to improve the uniformity of the tire and to improve the high-speed durability with the improvement of the uniformity. it can.

[0029]

EXAMPLE A tire of the present invention having a tire size of 195 / 70R14 91H and having the tire structure of FIG. 1 and a conventional tire having the same tire size and differing only in FIG. It was manufactured by the following manufacturing method. Conventionally, an unvulcanized base tire is molded, a fixed length of unvulcanized belt-shaped rubber is wound around its outer peripheral surface, the ends are spliced together to form a tread, and a green tire is molded. And vulcanized. The tire vulcanized base tire of the present invention and the vulcanized endless annular tread formed by the process of FIG. 3 are respectively formed, and a plurality of unvulcanized rubbers extruded in a strip shape on the outer peripheral surface of the base tire. An adhesive layer was formed by wrapping around the circumference, and an endless annular tread was fitted into the fitted body by sandwiching the adhesive layer, and then the fitted body was vulcanized in the step of FIG.

With respect to these test tires, uniformity, high-speed durability, vulcanization time and mold cost were evaluated by the following test methods, and the results are shown in Table 1. Uniformity: Rim size 14x5 for each test tire
The tire was mounted on a Ｊ JJ rim, and a measurement test was performed in accordance with JASO C607. The larger the index value, the better the uniformity.

High-speed durability: Each test tire was rim size 1
Attached to 4 × 51 / 2JJ rim, drum diameter 1707m
m, a high-speed durability test is carried out in accordance with JIS D-4230 on a drum of 10 m / h.
The running time until the tire was broken was measured, and the result was calculated as the reciprocal of the measured value of the conventional tire by 10
The index was set to 0. The higher the index value, the better the high-speed durability.

Vulcanization time: The vulcanization time of each test tire was measured, and the result was shown as an index with the conventional tire being 100. The smaller the index value, the shorter the vulcanization time. The vulcanization time of the tire of the present invention is obtained by adding the longer of the vulcanization time of the base tire and the vulcanization time of the tread and the vulcanization time of the adhesive layer.

Die cost: The die cost required for manufacturing a tire with a daily quantity of 1000 tires was calculated, and the cost was shown as an index with the conventional tire being 100. The smaller the index value, the lower the mold cost. The cost of the tire of the present invention includes a mold cost for molding a pre-cured tread,
Extruder costs are not included.

[0034] As is clear from Table 1, the tire of the present invention has excellent uniformity and high-speed durability as compared with the conventional tire, and it is possible to reduce the mold cost and the vulcanization time. . Moreover, when the joint between the base tire and the tread of the tire of the present invention was inspected, no wrinkles or air pockets were generated in the adhesive layer, and no tire failure was caused by this.

[0035]

As described above, according to the present invention, a vulcanized or semi-vulcanized base tire and an endless annular tread are separately prepared, and an adhesive layer for bonding the two is stripped. Because the extruded unvulcanized rubber is formed by orbiting, the coating layer covering the joining surface ends of the both is similarly formed by orbiting the extruded unvulcanized rubber in a strip shape. Even if the constituent members of the tire have a radius of curvature, wrinkles and air pockets do not occur in the adhesive layer and the coating layer, and tire defects due to uniformity and high-speed durability due to these can be reduced. .

In addition, since the base tire vulcanization molding die can be used in common for a plurality of types of tread vulcanization molding dies, the die cost can be significantly reduced. In addition, since the base tire and the tread are separately vulcanized, the vulcanization time can be effectively shortened by setting the optimum vulcanization time for each of them, and the productivity can be improved. Therefore, the reduction of the mold cost and the improvement of the productivity can be combined with each other to greatly reduce the tire manufacturing cost.

Furthermore, the tread formed in an endless annular shape has no joint in the tire circumferential direction, so that the uniformity of the tire can be improved, and the high-speed durability can be improved with the improvement of the uniformity.

[Brief description of the drawings]

FIG. 1 is a tire meridian half sectional view showing an example of a pneumatic tire manufactured by a manufacturing method of the present invention.

FIG. 2 is a cross-sectional view illustrating a mold for molding an endless annular precured tread in the production method of the present invention.

FIG. 3 is a cross-sectional view showing a step of forming a pre-cured tread by combining the mold of FIG. 2 and an extruder.

FIGS. 4A and 4B are tire meridian half cross-sectional views illustrating a joining step of a base tire and a tread in a method of manufacturing a pneumatic tire according to the present invention.

FIG. 5 is a tire meridian sectional view illustrating the final vulcanization step of the method for manufacturing a pneumatic tire according to the present invention.

FIGS. 6A and 6B are tire meridian half cross-sectional views showing another example of the joining process of the base tire and the tread in the method of manufacturing a pneumatic tire according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 tire 2 endless annular tread 3 adhesive layer 4 coating layer 5 carcass layer 7 bead section 10 belt layer 13, 14 strip-shaped unvulcanized rubber

Claims (3)

[Claims] 1. A vulcanized or semi-vulcanized base tire in which a carcass layer is mounted between a pair of left and right bead portions and a belt layer is disposed around the outer periphery of the carcass layer, and a tread is formed on the outer peripheral surface. A vulcanized or semi-vulcanized endless annular tread having a pattern formed thereon is preformed, and a plurality of strip-shaped unvulcanized rubbers are wound around the outer peripheral surface of the base tire to form an adhesive layer. A method of manufacturing a pneumatic tire, wherein the endless annular tread is fitted into the fitting body to form a fitting body, and then the unvulcanized portion of the fitting body is vulcanized. 2. Before vulcanizing an unvulcanized portion of the fitted body, strip-shaped unvulcanized rubber is wrapped at least once around the end of the joint surface between the base tire and the tread of the fitted body. The method for manufacturing a pneumatic tire according to claim 1, wherein a coating layer is formed. 3. A vulcanized or semi-vulcanized base tire in which a carcass layer is mounted between a pair of left and right bead portions and a belt layer is disposed around the outer periphery of the carcass layer, and a tread is formed on the outer peripheral surface. A vulcanized or semi-vulcanized endless annular tread in which a pattern is formed is previously formed, and the endless annular tread is fitted around the outer periphery of the base tire via an adhesive layer made of unvulcanized rubber. At the same time as forming, a coating layer is formed by wrapping at least one round of unvulcanized rubber in a strip shape along the end of the joining surface between the base tire and the tread, and then a mold is brought into contact with at least the coating layer. A method for manufacturing a pneumatic tire in which an unvulcanized portion of the fitting body is vulcanized in the state where the fitting is performed.