JP2016112838A - Molding method of green tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method of a green tire for improving bead durability by restraining a cord wave in molding time.SOLUTION: A green tire molding method includes a step (ST1) of fixing a bead part 1 of a green tire in a state of not winding up an end part of a carcass ply 4 and an end part of respective chafers 1c and 1d by a bead lock mechanism D1, a step (ST2) of setting an interval W1 of mutual bead lock mechanisms D1 so that an angle α of a horizontal line L2 to a straight line L1 connecting an end P1 of a belt 4b that is the outermost side in the tire width direction and a bead lock point P2 becomes 50°-70° when setting an intersection between a perpendicular L3 from an end of a bead core 1a that is the innermost side in the tire width direction and a gripping surface of the bead lock mechanism D1 as the bead lock point P2 and a step (ST3) of pushing and winding up the carcass ply 4 and the chafers 1c and 1d by a roller D2 moving upward from below in a state of adding pressure to the inside of the green tire.SELECTED DRAWING: Figure 3

Description

  The present disclosure relates to a method of forming a green tire before vulcanizing a pneumatic tire.

  In heavy-duty pneumatic tires used for trucks, buses, and the like, there are cases where one layer of steel chacher and two or more layers of nylon chacher are provided outside the carcass ply at the bead portion.

  The green tire before vulcanizing the pneumatic tire is molded using the molding apparatus described in Patent Document 1. Specifically, in a state where the bead portion of the raw tire is fixed with a bead lock, the carcass ply, the chaha, and the sidewall rubber are pushed up by the roller by moving the roller from below to above.

JP-A-9-309159

  As shown in the upper part of FIG. 5, the nylon cord C of the nylon chafer 1d is preferably inclined at a constant angle with respect to the radial direction. However, as shown in the lower part of FIG. 5, a cord wave in which the nylon cord C of the nylon chafer 1d bends at the end portion due to the pushing up by the roller is generated, the gap between the nylon cords C is opened, and the end of the nylon chafer is It was found that the durability was lowered, leading to a failure of the bead portion. Therefore, it is required to suppress the code wave when manufacturing the raw tire.

  The present disclosure has been made paying attention to such a problem, and its purpose is to provide a green tire molding method for suppressing the code wave at the time of molding and improving the bead durability. is there.

  In order to achieve the above object, the present disclosure takes the following measures.

That is, the green tire molding method of the present disclosure includes:
A carcass ply extending from the tread portion through the sidewall portion to a pair of bead portions; a belt provided outside the carcass ply in the tread portion; a bead core disposed inside the carcass ply in the bead portion; A method of forming a green tire having a one-layer steel checker and two or more nylon checkers arranged outside the carcass ply in the bead portion,
Fixing the bead portion of the raw tire in a state where the end portion of the carcass ply and the end portion of each of the chehas are not wound up with a bead lock mechanism;
The belt end and the bead lock point that are the outermost in the tire width direction when the intersection of the perpendicular from the end of the bead core that is the innermost in the tire width direction and the grip surface of the bead lock mechanism is a bead lock point Setting an interval between the bead lock mechanisms so that an angle of a horizontal line with respect to a straight line connecting the bead is 50 ° or more and 70 ° or less;
Pressing the carcass ply and each chacher with a roller that moves upward from below in a state where pressure is applied to the inside of the raw tire;
including.

  Thus, if the angle is set, the code wave of the nylon chafer can be suppressed, and the failure of the bead portion can be reduced and the durability can be improved.

  In order to further improve the durability of the bead portion, the pressure applied to the inside of the green tire is preferably 0.03 MPa or more and 0.1 MPa or less.

  In order to suppress poor air entry, a bead filler is provided on the outer side in the tire radial direction of the bead core, and in a state where the bead portion is fixed by the bead lock mechanism, the tip of the bead filler, the carcass ply, Are preferably spaced apart.

Sectional drawing which shows the raw tire which rolled up the carcass ply, the steel chafer, and the nylon chafer. The expanded sectional view which shows the bead part of the pneumatic tire after vulcanization. The figure which shows typically the raw tire of the state which has not wound up the carcass ply, the steel checker, and the nylon checker. The flowchart which shows the shaping | molding method of the raw tire of this indication. Explanatory drawing about the code wave of nylon chae.

  Hereinafter, a green tire molding method according to an embodiment of the present disclosure will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a green tire in which a carcass ply, a steel checker and a nylon checker are wound up. FIG. 2 is an enlarged cross-sectional view showing a bead portion of the pneumatic tire after vulcanization. FIG. 3 is a view schematically showing a raw tire in a state where the carcass ply, the steel chafer, and the nylon chacher are not wound up.

  As shown in FIGS. 1 to 3, the raw tire includes a pair of bead portions 1, sidewall portions 2 extending from the respective bead portions 1 to the tire radial direction outer side RD 1, and tire radial direction outer side RD 1 of both sidewall portions 2. And a tread portion 3 connected to the end of the. The bead portion 1 is provided with an annular bead core 1a formed by covering a converging body such as a steel wire with rubber and a bead filler 1b made of hard rubber.

  The green tire includes a toroidal carcass ply 4 that extends from the tread portion 3 through the sidewall portion 2 to the bead portion 1. The carcass ply 4 has at least one layer and is locked in a state in which an end thereof is wound up via the bead core 1a. The carcass ply 4 is formed by covering a cord extending substantially perpendicular to the tire equator CL with a topping rubber. Inside the carcass ply 4 is disposed an inner liner rubber 4a for maintaining air pressure.

  Further, the raw tire includes a tread rubber 5 provided outside the carcass ply 4 in the tread portion 3, a sidewall rubber 6 provided outside the carcass ply 4 in the sidewall portion 2, and a carcass ply in the bead portion 1. 4 and a rim strip rubber 7 provided on the outside. A belt 4 b is provided inside the tread rubber 5 to reinforce the carcass ply 4. On the outside of the carcass ply 4, there is provided a one-layer steel chacher 1 c having a steel cord that is inclined with respect to the radial direction, and on the outer side thereof, there is a two-layer having a nylon cord that is inclined with respect to the radial direction. A nylon chafer 1d is provided. The inclination angle of the nylon cord C with respect to the radial direction can be appropriately changed as long as it is 30 ° or more and 50 ° or less. Further, in this embodiment, the nylon chafer 1d has two layers, but can have three or more layers. When viewed along the tire axis, the nylon chafers 1d and 1d may be arranged so as to be inclined in the same direction, and one nylon chafer 1d intersects the other nylon chafer 1d. You may arrange so that.

  As shown in FIG. 3, the inner liner rubber 4a, the carcass ply 4, the steel chacher 1c, the nylon chacher 1d, and the side wall rubber 6 are wound in a cylindrical shape using a molding apparatus D having a bead lock mechanism D1 and a roller D2. The bead core 1a and the bead filler 1b are placed on the case C, fixed by the bead lock mechanism D1, and the end of the case C is wound up by the roller D2 to form a raw tire.

  Specifically, as shown in FIG. 3, in step ST1 (see FIG. 4), the end portion of the carcass ply 4 and the bead portion 1 of the raw tire in a state where the end portions of the respective chahas 1c and 1d are not rolled up are displayed. Fix with the bead lock mechanism D1.

  In the next step ST2 (see FIG. 4), the angle α of the horizontal line L2 with respect to the straight line L1 connecting the end P1 of the belt 4b that is the outermost in the tire width direction and the bead lock point P2 is 50 ° or more and 70 ° or less. In addition, an interval W1 between the bead lock mechanisms D1 is set. The bead lock point P2 is an intersection of the perpendicular L3 from the end of the bead core 1a that is the innermost in the tire width direction and the grip surface of the bead lock mechanism D1. The angle α is determined by the interval W1 of the bead lock mechanism D1.

  In the next step ST3 (see FIG. 4), the carcass ply 4 and the respective chachers 1c and 1d are pushed up by the roller D2 moving upward from below in a state where pressure is applied to the inside of the raw tire with air. The angle α is maintained at least from the winding start point to the winding end point.

  The pressure applied to the inside of the green tire is preferably 0.03 MPa or more and 0.1 MPa or less. If the internal pressure is low, the effect of suppressing the code wave of the nylon chae 1d is enhanced, but conversely, the code wave of the carcass ply 4 is invited. If the internal pressure is high, the code wave of the nylon chafer 1d is likely to occur. The internal pressure value can be used regardless of the tire size.

  As shown in the figure, a bead filler 1b is provided outside the bead core 1a in the tire radial direction. In a state where the bead portion 1 is fixed by the bead lock mechanism D1, it is preferable that the tip of the bead filler 1b and the carcass ply 4 are separated from each other. If the tip of the bead filler 1b and the carcass ply 4 are in a separated state, the air is suppressed by being sequentially pushed from the lower side to the upper side by the roller D2. However, if the tip of the bead filler 1b is in contact with the carcass ply 4 (case C) before winding up, air may be trapped at that time, leading to failure of the bead unit 1. Cause. Preferably, the bead filler 1b is standing upright as shown in the drawing (the straight line L4 connecting the tip of the bead filler 1b and the center of the bead core 1a is 90 ° with respect to the horizontal line). This is because it is possible to prevent the bead filler 1b from unexpectedly falling and embracing air if it is made upright in this way.

As described above, the green tire molding method of the present embodiment is provided on the outer side of the carcass ply 4 at the tread portion 3 and the carcass ply 4 that extends from the tread portion 3 through the sidewall portion 2 to the pair of bead portions 1. The belt 4b, the bead core 1a disposed inside the carcass ply 4 in the bead portion 1, the one-layer steel chaser 1c disposed outside the carcass ply 4 in the bead portion 1, and the two or more layers of nylon chafer 1d. A method of forming a raw tire having
A step (ST1) of fixing the bead portion 1 of the raw tire in a state where the end portion of the carcass ply 4 and the end portions of the respective chahas 1c and 1d are not wound up by the bead lock mechanism D1;
When the intersection of the perpendicular L3 from the end of the bead core 1a that is the innermost in the tire width direction and the gripping surface of the bead lock mechanism D1 is a bead lock point P2, the end P1 of the belt 4b that is the outermost in the tire width direction and the bead A step (ST2) of setting an interval W1 between the bead lock mechanisms D1 so that the angle α of the horizontal line L2 with respect to the straight line L1 connecting the lock point P2 is not less than 50 ° and not more than 70 ° (ST2);
A step (ST3) of pushing the carcass ply 4 and each of the chahas 1c and 1d with a roller D2 moving upward from below in a state where pressure is applied to the inside of the raw tire (ST3);
including.

  Thus, if the angle α is set, the code wave of the nylon chafer 1d can be suppressed, the failure of the bead portion 1 can be reduced, and the durability can be improved. If it is considered that a code wave is likely to be generated when it is pushed up only by the roller D2, if the angle α is reduced, the height of the nylon chae 1d end after winding will be lowered, and the bead part 1 will sleep. It is considered that the nylon chafer 1d is positively bonded by its own weight, the force locally received from the roller D2 can be reduced, and the code wave of the nylon chafer 1d can be suppressed. The amount of change of nylon chafer 1d could be suppressed within 15 °.

  In the present embodiment, the pressure applied to the inside of the raw tire is 0.03 MPa or more and 0.1 MPa or less. This is because, if the internal pressure is smaller than 0.03 MPa, the code wave suppression effect of the nylon chafer 1d is enhanced, while conversely, the code wave of the carcass ply 4 is invited. This is because if the internal pressure is greater than 0.1 MPa, the cord wave of nylon chae 1d will be invited.

  In the present embodiment, a bead filler 1b is provided on the outer side in the tire radial direction of the bead core 1a. In a state where the bead portion 1 is fixed by the bead lock mechanism D1, the tip of the bead filler 1b and the carcass ply 4 are separated from each other. Yes. If the winding is started in a state where the two are separated from each other in this way, it is possible to suppress the entry of air by sequentially abutting the two at the time of winding.

  In order to specifically show the configuration and effects of the present disclosure, the following evaluations were performed on the following examples.

(1) Angle change of nylon chafer A sample was picked up from the green tire after molding, and the angle change amount (code wave amount) of the nylon chafer was measured. Comparative example 1 was set to 100 and expressed as an index. It is considered that the smaller the numerical value, the less the code wave, contributing to the improvement of the durability of the bead portion 1.

(2) Angle change of carcass ply A sample was picked up from the green tire after molding, and the angle change amount (code wave amount) of the carcass ply was measured. When a code wave of a predetermined amount or more is generated, “X” is indicated, and when within the allowable range, “◯” is indicated.

(3) Endurance test mileage Tire size 11R22.5 is mounted on a 7.50 × 22.5 rim, and the internal pressure is 700 kPa, the load is 5450 kgf (increased by 10% every 168 hours), and the speed is 50 km / h. The tire was run on the drum until the bead part 1 failed. The travel distance was expressed as an index with Comparative Example 1 being 100. The larger the value, the longer the mileage, and the better the bead durability performance.

Comparative Example 1
As shown in the table, a pneumatic tire manufactured by vulcanizing a raw tire formed with an angle α of 75 ° and an internal pressure at the time of green tire molding of 0.08 MPa was used.

Example 1
A pneumatic tire manufactured by vulcanizing a raw tire formed with an angle α of 50 ° and an internal pressure of 0.08 MPa when forming the raw tire was used.

Example 2
A pneumatic tire produced by vulcanizing a raw tire formed with an angle α of 60 ° and an internal pressure at the time of green tire molding of 0.08 MPa was used.

Example 3
A pneumatic tire manufactured by vulcanizing a raw tire formed with an angle α of 70 ° and an internal pressure of 0.08 MPa when forming the raw tire was used.

Example 4
A pneumatic tire manufactured by vulcanizing a raw tire formed with an angle α of 60 ° and an internal pressure at the time of green tire molding of 0.02 MPa was used.

Example 5
A pneumatic tire produced by vulcanizing a raw tire molded with an angle α of 60 ° and an internal pressure at the time of green tire molding of 0.03 MPa was used.

Example 6
A pneumatic tire manufactured by vulcanizing a raw tire formed with an angle α of 60 ° and an internal pressure at the time of forming the raw tire of 0.05 MPa was used.

Example 7
A pneumatic tire manufactured by vulcanizing a raw tire formed with an angle α of 60 ° and an internal pressure at the time of forming the raw tire of 0.1 MPa was used.

  According to Comparative Example 1 and Examples 1 to 3, it can be seen that the code wave of the nylon chae 1d can be suppressed if the angle α is small. However, if the angle α is less than 50 °, it is necessary to change the diameter of the belt drum. Although the belt drum diameter at the present time is set to an optimum diameter, if the belt drum diameter is reduced, high-speed durability and deterioration of uneven wear are caused. Therefore, it can be seen that the preferable range of the angle α is 50 ° or more and 70 ° or less.

  According to Examples 4 and 5, it was found that if the internal pressure is smaller than 0.03 MPa, a code wave is generated in the carcass ply 4. According to Examples 2 and 4 to 7, it is understood that the internal pressure is preferably 0.03 or more and 0.1 MPa or less.

  The structure employed in each of the above embodiments can be employed in any other embodiment. The specific configuration of each unit is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present disclosure.

DESCRIPTION OF SYMBOLS 1 ... Bead part 1a ... Bead core 1b ... Bead filler 1c ... Steel checker 1d ... Nylon checker 2 ... Side wall part 3 ... Tread part 4 ... Carcass ply 4b ... Belt D1 ... Bead lock mechanism D2 ... Roller

Claims (3)

A carcass ply extending from the tread portion through the sidewall portion to a pair of bead portions; a belt provided outside the carcass ply in the tread portion; a bead core disposed inside the carcass ply in the bead portion; A method of forming a green tire having a one-layer steel checker and two or more nylon checkers arranged outside the carcass ply in the bead portion,
Fixing the bead portion of the raw tire in a state where the end portion of the carcass ply and the end portion of each of the chehas are not wound up with a bead lock mechanism;
The belt end and the bead lock point that are the outermost in the tire width direction when the intersection of the perpendicular from the end of the bead core that is the innermost in the tire width direction and the grip surface of the bead lock mechanism is a bead lock point Setting an interval between the bead lock mechanisms so that an angle of a horizontal line with respect to a straight line connecting the bead is 50 ° or more and 70 ° or less;
Pressing the carcass ply and each chacher with a roller that moves upward from below in a state where pressure is applied to the inside of the raw tire;
A method for forming a raw tire including   The method for forming a green tire according to claim 1, wherein the pressure applied to the inside of the green tire is 0.03 MPa or more and 0.1 MPa or less. A bead filler is provided on the outer side in the tire radial direction of the bead core,
The raw tire molding method according to claim 1 or 2, wherein a tip of the bead filler and the carcass ply are separated in a state where the bead portion is fixed by the bead lock mechanism.

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