JPH0351119A - Manufacture of radial tire and radial tire per se - Google Patents

Abstract

PURPOSE:To prevent generation of separation at a time of high-speed travel by overlapping a plurality of sheets of belt plies to annularly form a belt and spirally winding a coated cord wherein rubber cement is stuck to a single cord on the surface of the belt and laminating tread rubber lined with a rubber sheet thereon. CONSTITUTION:A belt 3 is annularly formed by overlapping a plurality of sheets of belt plies 2. A tread-belt assembly is formed by spirally winding a coated cord 4 described hereunder on the surface of the belt 3 and laminating tread rubber lined with a sheet formed of rubber composition low in Mooney viscosity thereon. The coated cord 4 is obtained by previously sticking rubber cement to a single cord or this single cord treated by resorcin-formalin latex and drying it. Then a cylindrical casing assembled in the separated stage is inserted into this assembly. Thereafter the diameter of this casing is toroidally expanded while narrowing the interval of beads and closely stuck to the inner surface of the tread-belt assembly. Thereby a green tire is formed, vulcanized and molded. Therefore a radial tire can be manufactured easily, rapidly and economically. Further for example, even when high-speed travel is performed, generation of separation can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a radial tire for passenger cars that has excellent high-speed durability and good tire uniformity, and to a radial tire.

[Prior Art] When a car is driven at high speed, the tires rotate at high speed, so centrifugal force acts, and the belt side end, which is a cut edge, moves relatively easily inside the tire and floats up from the carcass. It is known that as a result, separation tends to occur between the carcass and the belt side end.

Conventionally, in order to prevent this, there was a method of bending the side edges of the belt to restrain the cut edge of the belt (for example, Japanese Patent Publication No. 44
-19561), and a method of tightening the belt by wrapping several heat-shrinkable cords in parallel and rubberized tape in a spiral shape on the belt, thereby preventing the belt side edges from floating ( For example, JP-A-62-225406, JP-A-62-290524, JP-A-62-25103,
Japanese Unexamined Patent Publication No. 62-203803) has been proposed.

[Problems to be Solved by the Invention] However, the conventional method of folding the side edges of a belt requires further improvement in terms of the effect of preventing separation.

The method of spirally wrapping rubberized tape around multiple heat-shrinkable cords in parallel is an improvement over the above method of bending the side edges of the belt, but it leaves the side edges of the belt unconstrained. Since there is a cutting tip of the tape that is shaped like this, when stress is applied in the length direction, this cutting tip moves as if sliding over the belt, so the effect of tightening the belt is weak, and in reality Approximately 1/8th of the circumference of the tire did not work effectively. Moreover, the tip of the tape itself was a cause of separation.

Also, focusing on methods of making tape, there are two methods: coating rubber using an extruder that has a mouthpiece with a groove through which a cord passes perpendicular to the axial direction of the rubber extruder, or coating both sides of a blind weave with rubber. A method has been adopted in which multiple cords are pulled and then torn between the cords, but the former method of coating multiple cords with rubber is expensive and requires a special extruder; Furthermore, before extruding the rubber, a so-called complicated pre-process is required, such as heating it with a rubber roll to create a rubber strip, cooling and storing it, and then feeding it to an extruder. The latter method of tearing the rubberized blind weave between the cords also has the problem of requiring a large number of man-hours to rubberize the blind weave, and the weft of the blind weave must be cut. This method requires cutting only the weft threads without cutting the warp threads, which is technically difficult and has the disadvantage of high costs.

An object of the present invention is to provide a radial tire with excellent high-speed durability that can reliably restrain the belt side end and prevent separation even when running at high speed. Another object of the present invention is to easily, reliably, and quickly restrain the belt side end without requiring a special extruder or many pre-processes as in the past, and without any technical difficulty. An object of the present invention is to provide a method for manufacturing a radial tire with excellent economic efficiency.

[Problems to be Solved by the Invention] As a result of intensive studies to achieve the above object, it was found that a single cord or resorcinol, formalin, etc.
A tread belt is created by wrapping a latex-treated single cord with rubber glue and drying the covered cord in a spiral shape, and then layering a tread rubber lined with a sheet of Mooney low viscosity rubber composition on top of it. An assembly is formed, and a cylindrical casing assembled in a separate process is inserted into this assembly, and then the bead interval is narrowed and the diameter expands into a toroidal shape to tightly fit against the inner surface of the tread/belt assembly. We have invented a method for manufacturing radial tires by forming and vulcanizing green tires.

Furthermore, the radial tire according to the present invention has at least two layers of belt plies each having steel cords arranged at an angle of 10 to 30' with respect to the tire circumferential direction in a portion corresponding to the crown of the carcass having a radial structure. A radial tire with a belt tracker laminated so as to
Rubber glue is applied to the entire outer surface of the belt in advance.
[Function] According to the present invention, one or more rubber-covered cords made of a single cord of machine fiber are wound in a spiral shape with deviations in the width direction. Since it is simply immersed in a bath of glue, adhered, and dried, there is no need to weave it into a blind weave as in the past. A large-scale device that can be manufactured easily and quickly, and that is conventionally used to rubberize blind weave in order to provide a belt reinforcing layer, and a device that cuts multiple pieces of rubberized blind weave into groups into tape shapes. It does not require any additional steps or processes.In addition to being highly productive, it requires little capital investment and is highly economical.

In addition, this spirally wound covered cord has a coating layer of a rubber composition around it, so it has good adhesion to the belt, and since only one cord is wound around the belt surface, it is easy to wrap it. The pitch end can be easily changed as desired, and the weight of the tire can be reduced by wrapping the belt tightly in areas that need to be strongly reinforced, and sparsely wrapping the belt in areas that do not need to be strongly reinforced.

In addition, the back of the tread is lined with a sheet of a rubber composition with low Mooney viscosity, so during the vulcanization process, the rubber sheet softens and flows into the gaps between the cords, filling them. , the tread belt assembly is integrated.

As described above, the radial tire of the present invention has a belt reinforcing layer formed by spirally winding a single rubber-coated cord.
The only cut end of the cord is the open tip of the coated cord;
Since there is only one cord per location, the decrease in belt tightening force near the cut end can be almost ignored, and the entire belt is tightened uniformly. As a result, local tightening of the belt reinforcing layer at the belt side edge does not cause belt separation due to a decrease in force, and the belt reinforcing layer does not have a localized decrease in rigidity in the tire circumferential direction. Tire uniformity does not deteriorate either.

On the other hand, when the green tire deforms because it follows the inside of the mold during vulcanization, the change in belt cord spacing is restricted by the belt reinforcing layer, so this occurs in a similar manner, and the belt cord spacing cannot be changed using the conventional method. Tire uniformity is better than tires that change unevenly.

A single cord is wound from one end of the belt to the opposite end, preferably the belt is sectioned into sections and the single cord is wound beginning at the same end of each section; Wrapping can be done at multiple points at the same time during one rotation of the tire, reducing the time it takes to wrap the tire.Furthermore, by changing the thickness and elastic modulus of the single cord wrapped around each section, you can create a single cord that is suitable for each section. Since the cord and pitch can be selected, the effect can be increased by tightening a small amount of cord.

[Example] The present invention will be described in detail below with reference to the accompanying drawings.

Figure 1 is a partial perspective view showing how the coated cords are wrapped around the belt surface. Belt 3 is a rubber-coated No. 1 belt ply with steel cords arranged at an angle of 10 to 30 degrees with respect to the circumferential direction. 1 in the opposite direction
It is constructed by overlapping a No. 2 belt braai 2 coated with rubber and having steel cords arranged at an angle of 0 to 30 degrees. The belt 3 is connected to WA and W by a dividing point 5 as shown in the figure.
The two coated cords 4 and 4 are divided into two parts B, and the two covered cords 4 and 4 are shifted in the width direction toward the other belt side end 3b, with the belt side end 3a and the division point 5 as the starting points 6 and 7 for winding, respectively. The reinforcing layer A is formed by winding the reinforcing layer A in a spiral manner, covering the entire surface of the belt 3.

The coated cord 4.4 is manufactured in advance by immersing two single cords in a bath of rubber paste made by dissolving a rubber composition in an organic solvent to adhere the rubber paste and drying. If necessary, single cords may be treated with resorcinol formalin latex before being dipped in rubber glue. Covered cord 4,
Regarding the amount of the rubber composition adhered in step 4, the concentration and viscosity of the rubber glue are adjusted so that a layer having a thickness of 0.01 to 1 mm is formed around the cord. The appropriate concentration is 10-50% and the viscosity is 2000-20000 cp. The appropriate pitch for the spiral winding is 0.5~5mm, and 0.5u+
If it is smaller, the number of windings will increase and the number of man-hours will increase.
If it is larger than II11, the belt tightening effect will be reduced, which is not preferable. Preferably, the side end regions of the belt are wound tightly and the central region is wound sparsely to increase the rigidity of the belt side end portions.

Organic synthetic fibers such as nylon, polyester, and aramid can be used as the single cord, and nylon is particularly suitable.

Next, as described above, the entire surface of the belt 3 is coated with a coated cord 4.
After wrapping 4, overlay the tread rubber (not shown) lined with a rubber sheet to complete the tread.
Form a belt assembly.

Next, carcass ply, sidewalls,
The casing, which has been molded into a cylindrical shape with a bead core etc. incorporated therein, is inserted into the tread/belt assembly in the usual manner.
A green tire is formed by expanding the diameter in a toroidal shape while narrowing the bead spacing until it adheres to the inner surface of the assembly, and then the green tire is placed in a mold and vulcanized to produce a radial tire.

FIG. 2 is a partially cutaway perspective view showing a radial tire according to an embodiment of the present invention manufactured in this way, in which 8 is a carcass, and other symbols are shown with the same symbols as in FIG. 1.

Note that 9 is the tip of the covered cord 4, and as shown in the figure, it exists only slightly with respect to the belt width, and is a belt reinforcement structure in which the decrease in belt tightening force near the cut end can be almost ignored. I can understand that.

Next, we actually produced a prototype tire with a tire size of 225150R16, divided the belt into three sections, one in which the belt reinforcement layer was entirely covered with one single cord (Example 1), and three single cords in each section. The tire was wrapped one by one to cover the entire surface (Example 2) and was tested for high-speed durability and tire uniformity. For comparison, a conventional tire was also tested in which eight cords were wrapped in two rows of rubber-covered tape, and the tape was wound spirally on the belt surface in the circumferential direction from one end of the belt to the other. did.

Table 1 shows the results.

The high-speed durability test was conducted under the test conditions of speed symbol V specified by the European Economic Organization Regulation ECE30, and since all the test subjects passed the specified conditions, the speed was further increased to 10 km/h every 10 minutes.
The drum was run on the drum in increments of r until it failed, and the running time was expressed as an index with the comparative example set as 100. The larger the value, the better.

Tire uniformity was measured by running on a drum with a load applied to it, measuring the variation in force in the driven direction (RF V) acting on the rotating shaft, and dividing the comparison tire by 100 and displaying it as an index. The smaller the value, the better.

Table 1 From Table 1, the tire of the present invention has better high-speed durability and tire uniformity than conventional tires, and the belt is divided into three sections 7 with different pitch intervals in the center area and side edge areas. It is recognized that the tire (Example 2) in which the area is loosely wrapped and the side edge area is tightly wrapped has better uniformity than the tire (Example 1) in which the entire area is wrapped with one single cord.

[Effects of the Invention] As described above, the present invention constructs a belt reinforcing structure by wrapping a rubber-coated cord consisting of a single cord around the belt surface. It does not require any pre-processing, nor does it require particularly large-scale special equipment, and can be manufactured simply, quickly, and economically, so it is extremely productive and economical.

Moreover, since it is wrapped and tightened with a single cord, the effect of reduction in force when tightening at the end of the reinforcing layer cord can be ignored, and it has the remarkable effect of reliably restraining the belt side end.
It can prevent separation even when running at high speeds, has excellent high-speed durability, and has good tire uniformity.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing how a coated cord is wrapped around a belt surface, and FIG. 2 is a partially cutaway perspective view showing a radial tire according to an embodiment of the present invention.

Claims (4)

[Claims] (1) On the surface of a belt formed by polymerizing multiple belt plies into an annular shape, a coated cord made by applying rubber glue to a single cord and drying it is wound spirally, and then a Mooney Tread rubber backed with a sheet of a low viscosity rubber composition is laminated to form a tread/belt assembly into which a cylindrical casing assembled in a separate process is inserted and the bead spacing is then adjusted. A method for producing a radial tire, which is characterized by expanding the diameter into a toroidal shape while narrowing the tire, forming a green tire by closely contacting the inner surface of a tread/belt assembly, and then vulcanizing and molding the tire. (2) The method for manufacturing a radial tire according to claim 1, wherein the covered cord is wound spirally around the belt surface from one side end to the other side end of the belt. (3) Divide one side edge of the belt and the belt surface at multiple points in the width direction, and using each section point as the winding start end, wrap the coated cord in a spiral manner on the belt surface while shifting in the same width direction. The method for manufacturing a radial tire according to claim 1 or 2, wherein the radial tire is wrapped. (4) In a radial tire equipped with a belt in which at least two layers of belt plies each having steel cords arranged at an angle of 10 to 30 degrees with respect to the circumferential direction of the tire are laminated on a portion corresponding to the crown of a carcass having a radial structure, A radial tire characterized in that a rubber-coated cord consisting of a single cord of organic fiber coated in advance with a rubber layer is wound spirally around the entire outer surface of the tire with deviations in the width direction.