JP2001212890A - Method for forming pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a pneumatic tire which makes the tensile force of a carcass uniform and thereby enables enhancement of durability, prevention of slippage of the carcass and reduction of a rate of occurrence of failures. SOLUTION: On the occasion when the carcass 2 is stretched and laid over a pair of right and left bead cores to form an unvulcanized tire, the end parts of the carcass 2 are turned up from the inside of the tire to the outside thereof and wound up around the bead cores 3, while the inner surface of the tire is pressed from the bead parts toward the side parts by a bladder 9, according to this forming method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a pneumatic tire which can prevent a partial imbalance in tension in a carcass and suppress the occurrence of a failure.

[0002]

2. Description of the Related Art Conventionally, unvulcanized tires (green tires)
As shown in FIG. 2A, a sheet-like carcass material is wound around a cylindrical tire building drum 1 to form a cylindrical carcass 2 as shown in FIG. 2 (a), and a ring-shaped bead core 3 is fitted to both ends of the drum. First step) Then, as shown in FIG. 2B, the carcass 2 is made into a donut shape, and the inner space thereof is pressurized with air to maintain the tire shape so that the end of the carcass 2 is turned around the bead core 3. The tire is folded back from the inside to the outside and wound up, and members such as the belt layer 4, the cap tread 5 and the side tread 6 are attached (second step). Then, as shown in FIG. These members were pressed against each other by pressing with a bladder from the outside (third step).

However, as shown in FIG. 3, in the second step, the end of the carcass 2 is turned around the bead core 3 from the inside of the tire to the outside while the inner space is pressurized with air, and the carcass 2 is turned back. Since the carcass tension is different between the non-existing part and the winding part 2 ',
The side stiffness (longitudinal stiffness, lateral stiffness) of the product tire decreases, which causes the load durability level to decrease.
Carcass misalignment during molding (so-called squatting) may also be a cause. Furthermore, peeling of the end splice portion between the carcass and the inner liner disposed inside the carcass occurs, or the carcass is opened,
The tire internal pressure cannot be increased, and the pressure bonding of each member becomes insufficient, resulting in a higher failure rate of remaining air.

Therefore, conventionally, as shown in FIG. 4, a bladder 7 is inserted into the inner space to press the inner surface of the unfolded portion of the carcass 2 as shown in FIG. Even in such a case, the carcass tension cannot be made uniform and the carcass misalignment cannot be sufficiently prevented (when the bladder pressure is increased, they increase conversely). Also,
As shown in FIG. 5, a metal stopper 8 is provided inside the bead portion.
Is provided to improve the crimpability of each member in the vicinity of the bead portion.In this case, however, it is effective only for measures against failure around the bead, and for solving non-uniform carcass tension and preventing carcass misalignment. Not in.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a pneumatic tire capable of increasing the durability by making the carcass tension uniform, preventing the carcass from shifting, and reducing the failure rate. .

[0006]

According to the method of molding a pneumatic tire of the present invention, when a carcass is mounted on a pair of right and left bead cores to form an unvulcanized tire, a bladder is formed by extending the tire inner surface from a bead portion to a side portion. The end portion of the carcass is folded back from the inside of the tire to the outside around the bead core while being pressed, and is rolled up.

Since the end of the carcass is rolled up (turned up) while the bladder presses the inner surface of the tire from the bead portion to the side portion with a bladder, no tension is applied to the carcass on the tire inner surface from the bead portion to the side portion. Thus, the carcass tension can be made uniform.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, after a first step is performed in the same manner as in FIG. 2 (a), as shown in FIG. The end of the carcass 2 is folded around the bead core 3 from the inside to the outside of the tire while being pressed by the bladder 9 over the portion, and wound up to form a winding portion 2 ′. Thereby, the carcass 2 is mounted on the pair of left and right bead cores 3.

The pressure in the tire inner space A when the bladder 9 is pressed may be in the range of atmospheric pressure to extremely low pressure, specifically, preferably in the range of atmospheric pressure to 40 kPa, and more preferably in the range of atmospheric pressure to 20 kPa. Good to be in the range. This is because the tire shape is maintained by the arrangement of the bladder 9, so that the tire inner space A does not need to be pressurized.

After forming the winding portion 2 'as described above, as shown in FIG. 1B, the winding portion 2' is formed.
May be pressed from the outside of the tire with another bladder. By this pressing, the unfolded portion of the carcass 2 and the rolled-up portion 2 'can be pressed and integrated further by pressing the inner bladder 9 and the other outer bladder from both sides.

Next, as shown in FIG. 1C, the inner space A of the tire is pressurized (60 kPa to 100 kPa),
After the members such as the belt layer 4, the cap tread 5, and the side tread 6 are attached, as shown in FIG. 1 (d), these members are pressed from the outside from the bead portion to the side portions by another bladder. Crimp. Even if the tire inner space A is in a pressurized state, a tension is applied to the unfolded portion of the carcass 2 and the winding portion 2 'in the same manner, so that the carcass tension does not become uneven. The pressurized state may be achieved by filling the tire inner space A with air.

After pressing with a bladder as shown in FIG. 1 (d), the stitching means 10 is pressed as shown in FIG. 1 (e).
It is preferable to press the outer surface of the side tread 6 to improve the crimpability of the member.

[0013]

EXAMPLES Pneumatic tires having a common tire size of 165 / 60R14 75H were produced (conventional examples 1 to 3 and examples 1 to 3), and the longitudinal spring constant, lateral spring constant, and durability of these tires were as follows. , The amount of carcass deviation and the failure occurrence rate were evaluated. Table 1 shows the results.

Here, Conventional Example 1 is a tire by the molding method shown in FIG. 3 (normal blow molding), and Conventional Example 2 is a molding method shown in FIG. 4 (inner bladder type).
Conventional example 3 is a tire according to the molding method (bead portion metal stopper auxiliary type) shown in FIG. Examples 1 to 3 are tires according to a molding method in which a bladder is disposed on the tire inner surface from a bead portion to a side portion.

Longitudinal spring constant : An internal pressure of 22
The spring constant in the tire longitudinal direction when a load of 3.4 kN was applied at 0 kPa was indicated by an index. The higher the index, the better.

Lateral spring constant : An internal pressure of 22 was measured using a characteristic tester.
The spring constant in the tire lateral direction when a load of 3.4 kN was applied at 0 kPa was indicated by an index. The higher the index, the better.

Durability : Implemented in accordance with the durability test method specified in JIS D4230 (1998). After the final test step required by JIS, the tire was run until a failure occurred, and the running distance was indexed (test (N = 5, average of n = 3 excluding maximum and minimum). The higher the index, the better.

Carcass shift amount : The difference (shift amount) from the carcass position at the start of molding (relative position to the bead core) to the carcass position at the end of molding is indicated by an index (total left and right). The smaller the value, the better.

Failure occurrence rate : Air remaining failure occurrence rate. The incidence of Conventional Example 1 is set to 100, and the incidence under each condition is indicated by an index. The smaller the value, the better.

[0020]

[Table 1] As is clear from Table 1, Examples 1 to 3 are Conventional Examples 1 to 3.
It can be seen that, in comparison with, the vertical spring constant, the horizontal spring constant, the durability, the carcass deviation amount, and the failure occurrence rate are excellent.

[0021]

As described above, according to the pneumatic tire molding method of the present invention, when a carcass is mounted on a pair of left and right bead cores to form an unvulcanized tire, the tire inner surface is moved from the bead portion to the side. The end of the carcass is folded back from the inside of the tire to the outside around the bead core while being pressed with a bladder, and the carcass tension can be equalized, increasing durability, preventing carcass misalignment and reducing the failure rate It is possible to do.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic process explanatory view showing a molding method of the present invention, in which (a) presses an inner surface of a tire from a bead portion to a side portion with a bladder, and moves an end of a carcass around a bead core from the tire inside to the outside. Folding and winding up, (b) pressing the rolled up portion from outside of the tire with a bladder, (c) pressing the inner space of the tire and applying the belt layer, cap tread and side tread The step (d) is a step of pressing with a bladder from the outside from the bead part to the side part, and the step (e) is a step of pressing the outer surface of the side tread by stitching means.

FIG. 2 is a schematic process explanatory view showing a conventional molding method;
(a) is a step of forming a cylindrical carcass, (b) is a step of applying a member such as a belt layer, cap tread and side tread by pressing the inner space of the tire,
(c) is a step of pressing with a bladder from the outside from the bead portion to the side portion.

FIG. 3 is an explanatory view showing a conventional process of winding an end portion of a carcass around a bead core from the inside of the tire to the outside while pressurizing the inner space with air.

FIG. 4 is an explanatory view showing a conventional process of inserting a bladder into an inner space portion and pressing an inner surface of an unfolded portion of the carcass.

FIG. 5 is an explanatory view showing a process in which a metal stopper is conventionally provided inside a bead portion to improve the pressure-bonding property of each part near the bead portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical tire forming drum 2 Carcass 2 'Carcass winding part 3 Bead core 4 Belt layer 5 Cap tread 6 Side tread 7 Bladder 8 Stopper 9 Bladder

Claims (3)

[Claims] When a carcass is mounted on a pair of left and right bead cores to form an unvulcanized tire, the inner end of the carcass is wound around the bead core while pressing the inner surface of the tire from a bead portion to a side portion with a bladder. A method of molding a pneumatic tire that is turned upside down and rolled up. 2. The pressure in the tire inner space when the bladder is pressed is in the range of atmospheric pressure to 40 kPa.
A method for molding the pneumatic tire according to the above. 3. The method for forming a pneumatic tire according to claim 1, wherein the winding portion is pressed from the outside of the tire with another bladder.