JPH04212836A - Reclaiming method of pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the durability of a belt in a reclaimed tire. CONSTITUTION:The side outer than two layers of cord array layers 12, 14 positioned inside a tire in three layers or more of cord array layers constituting a belt is removed, and two layers of novel cord array layers 16, 18 and a tread rubber are stuck. Cord array angles alpha,beta are approximately equalized respectively in the cord array layers 16, 18 at that time, and the layers 16, 18 are cut at an angle equal to or smaller than the cord array angle theta of the cord array layer 14, and stuck in the opposite direction to an equatorial surface in the cord array direction of the cord array layer 14.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a pneumatic radial tire, and more particularly to a tire retreading method that improves belt durability.

0002

[Prior Art] A pneumatic radial tire is equipped with a carcass made of a so-called radially arranged cord layer and a belt made of a cord arrangement layer arranged around the crown portion at a relatively shallow angle with respect to the tire's equatorial plane. Due to the hoop effect of the belt, there is less movement of the tread rubber that forms the tread surface of the tire compared to bias tires, resulting in excellent durability and wear resistance, and low rolling resistance. Because of these advantages, with the expansion and development of expressway networks in recent years, they tend to be used favorably in heavy-duty vehicles such as trucks and buses. In particular, for pneumatic 4-radial tires applied to trucks, buses, etc., belts with four or more cord arrangement layers are used to reliably protect the carcass and provide a certain degree of rigidity in the tire circumferential direction. Tires with built-in tires are becoming popular.

By the way, even if the tread of a tire is in a state of advanced wear, the carcass usually still has sufficient strength, so in that case, the remaining tread rubber from the worn tire is removed. The method used is to remove the unvulcanized tread rubber and adhere it to the surface of the base tire to form a green tire, apply internal pressure to this green tire, and vulcanize it in a mold to retread the tire. . Retreading tires is also important from the standpoint of effective use of resources and economy.

[0004] Furthermore, when tires used for running are examined in detail, some tires even have damage to the cord arrangement layer that forms the belt, and in such cases, the damaged cord arrangement layer must also be removed. There is a need. However, it is difficult to judge the extent of damage inside the belt.
In general, in the case of a belt having four cord arrangement layers, the two cord arrangement layers located on the outside of the tire are often damaged, so the two layers of cord arrangement located on the outside of the tire are damaged. The process involves removing layers to determine whether or not rehabilitation is possible. In the case of a tire in which three or more cord arrangement layers are damaged, the tire is discarded in consideration of safety.

On the other hand, if the damage to the cord alignment layer does not extend to the third layer, there will be virtually no problem even with a retreaded tire, so the cord alignment of the remaining belt of the base tire will not cause any problems. On top of the layer, two new cord arrangement layers and unvulcanized tread rubber with a predetermined cross-sectional shape are newly pasted to form a green tire, which is then vulcanized in a mold under internal pressure. They are being rehabilitated and rehabilitated. At that time, the two newly applied cord array layers are cut at an angle that is approximately the same as that of the cord array layer used when molding new tires, usually approximately 22 degrees. Ta. Note that the cutting angle herein refers to the angle between the cut cords of the cord arrangement layer and the tire equatorial plane.

[0006]

[Problem to be Solved by the Invention] However, in tires that have been retreaded by removing the two belt cord arrangement layers located on the outside of the tire including the tread rubber, the belt durability performance is lower than that of a new tire. Problems often arose in which the performance decreased.

[0007] In a new tire, this occurs due to the pantograph movement of the cords in the cord arrangement layer of the belt as the green tire vulcanizes and molds under internal pressure and bulges outward in the radial direction. In other words, the cutting angle (22°)
Since it shifts in the direction of becoming smaller, the tension acting on the belt increases, and as a result of the increased tension acting on the belt, the relative movement of the belt is suppressed.
In the case of retreaded tires, the amount of radial outward expansion of the green tire due to vulcanization molding is extremely small compared to that when vulcanizing new tires. It is difficult to expect that the intersection angle between the cord and the tire equatorial plane will decrease due to the bulge.

Furthermore, during vulcanization molding, unvulcanized tread rubber that is pressed against the inner surface of the mold may flow from the center of the tire toward the outside in the width direction. The cutting angle (22°
) will shift in the direction of becoming larger. Furthermore, the cord array layer 16 on the inner side of the tire adjacent to the outermost cord array layer also has its cords extending in the same direction as the outermost cord array layer 1.
Although the amount of deviation is smaller than that of the outermost cord arrangement layer, it is shifted in the direction in which the angle of intersection with the tire equatorial plane increases.

Therefore, in a retreaded tire, the angle of intersection of the cords of the cord arrangement layer constituting the belt with the tire equatorial plane is larger than the angle at the time of cutting (22°). As a result, the tension acting on the belt is smaller than that of a new tire belt, making it difficult to suppress the relative movement of the belt.
This will reduce the durability of the belt. The present invention was made in view of such problems, and an object of the present invention is to provide a method for retreading a pneumatic tire without reducing belt durability.

0010

[Means for Solving the Problems] Therefore, in the present invention, in a carcass made of a toroidal radial array cord ply spanning between a pair of bead parts, a sidewall part connected to the bead part and a When retreading a pneumatic radial tire in which the tread part that forms the tire tread is reinforced and a belt consisting of three or more cord arrangement layers is arranged along the outer circumference of the crown part of the carcass, two The outer cord array layer and tread rubber are removed leaving the cord array layer of the layer, and the outer cord array layer and tread rubber are removed to form a base tire, and then two new cord array layers are formed, and these cords are attached to the outer side of the remaining tire. The cords of the cord array layer are cut in opposite directions with respect to the tire equatorial plane, and the angles they make with the tire equatorial plane are less than or equal to the intersection angle between the remaining cord array layer cords on the outside of the tire and the tire equatorial plane. The green tire is formed by attaching the material to a base tire, further attaching tread rubber, and applying internal pressure to the green tire to vulcanize it in a mold.

FIG. 1 is a developed view of a green tire belt according to the present invention, and the belt 10 includes four cord arrangement layers 12, 14, 16, and 18. The first cord arrangement layer 12 located at the innermost side of the belt has its cords formed at a relatively deep angle with respect to the tire equatorial plane S, for example, 45
It extends almost uniformly upward to the right at an angle within the range of 52 degrees, and has a hollow structure in which the central portion in the width direction is removed. The cords of the second cord array layer 14, which are disposed adjacent to and outside the cord array layer 12, are arranged in the tire equatorial plane S.
a relatively shallow angle (θ), e.g. 18° to 20
It also extends upward to the right, almost uniformly at angles within a range of .

On the other hand, the third cord array layer 16 located on the outside of the tire with respect to the cord array layer 14 has its cords aligned with the cords of the adjacent second cord array layer 14 on the inside of the tire in the tire equatorial plane S. The cords extend in opposite directions, that is, upward to the left, and the angle (α) that the cords make with the tire equatorial plane is equal to the angle (θ) that the cords forming the second cord arrangement layer 14 make with the tire equatorial plane S. ), that is, 18°~
The value shall be within the range of 20° or less. The angle (β) that the cords of the fourth cord array layer 18 located on the outermost side of the belt 10 make with the tire equatorial plane S is the angle (α) that the adjacent third cord array layer 16 makes with the tire equatorial plane S. )
approximately equal to. In addition, the code|symbol 20 shows the unvulcanized tread rubber which forms a tire tread part. Of course, the extending direction of each cord arrangement layer forming the belt 10 may be reversed.

[0013] In order to obtain such a green tire, the tread rubber of the tire to be retreaded is first removed, and the first and second tread rubber located inside the tire are removed along the line L shown by the dashed line in FIG. Third and fourth cord array layers 18 and 16 located on the outside of the tire, leaving the cord array layers 14 and 12
is removed using a suitable cutter, and the degree of damage to the belt 10 is examined. Then, tires whose belts 10 are not damaged at all, or whose damage extends to the third or fourth cord arrangement layer are selected as base tires. Of course, when retreading a tire whose belt is composed of three cord array layers or five or more cord array layers to obtain a retreaded tire having a belt consisting of four cord array layers, two layers located inside the tire may be used. The cord arrangement layer of the layers can be left to form a base tire.

Next, after shaping the surface shape and dimensions of the base tire on the side where the first and second cord arrangement layers remain using a wire brush or the like, an adhesive is applied to the shaped surface. Then, in order to reliably adhere the third cord array layer 16 to be newly attached to the remaining second cord array layer 14, an unvulcanized cushion sheet (not shown) with a thickness of 0.5 mm to 1.0 mm is attached. is pasted on the surface of the base tire along its circumferential direction. The width of this cushion sheet is determined by the width of the third cord arrangement layer 16.
preferably approximately equal to the width of the base tire. This can improve the adhesion between the unvulcanized tread rubber and the base tire shaping surface, which will be described later. In order to prevent separation at the ends of the belt, a thickness of 0 is applied to each position on this cushion sheet corresponding to the ends in the width direction of the third cord arrangement layer 16.
．． Another unvulcanized narrow cushion sheet (not shown) of 5 mm to 0.8 mm is pasted along the circumferential direction.

The third cord array layer 16 is attached to a predetermined position on the wide cushion sheet.
, the angle between the cord and the tire equatorial plane S (α
) is equal to or smaller than the angle (θ = 18° to 20°) between the cords of the second cord array layer 14 and the tire equatorial plane S, and the cords are cut so that the extending direction is opposite to the angle (θ = 18° to 20°). use something That is, in the tire shown in FIG. 1, the third cord arrangement layer 16 is attached so that the cords thereof extend upward to the left. As described above, the widthwise end portion of the cord array layer 16 is positioned on another narrow cushion sheet. These narrow cushion sheets function as cushioning materials for the widthwise ends of the cord array layer 16, and provide separation from the widthwise ends of the cord array layer 16, which is wider than the other cord array layers. effectively prevent it.

A new fourth code arrangement layer 18 is pasted over the third code arrangement layer, but the code arrangement layer 18
Also, the intersection angle (β) between the cord and the tire equatorial plane S is the third
The cords of the cord array layer 16 are cut to be approximately equal to the intersection angle (α) between the cords of the cord array layer 16 and the tire equatorial plane S, and the extending direction thereof is upward to the left. Next, unvulcanized tread rubber 20 is pasted across the stacked cord array layers 16 and 18, and a stitcher is used to ensure that the cord array layers and tread rubber adhere to the base tire to form a green tire. . A retreaded tire is obtained by applying internal pressure to this green tire and vulcanizing it in a mold. In addition, in order to reduce the flow of unvulcanized tread rubber within the mold during vulcanization molding, it is preferable to select a tread rubber with a cross-sectional shape that causes less rubber flow.

[0017]

[Operation] In the green tire formed by such a method, the intersection angles (α, β) between the respective cords of the third and fourth cord arrangement layers 16 and 18 and the tire equatorial plane are the second
Since the cords of the cord array layer 14 are approximately equal to or smaller than the angle (θ) that they make with the tire equatorial plane, when vulcanization molding is performed by applying internal pressure in the mold, the tire does not move outward in the radial direction. To maintain an intersection angle substantially equal to the intersection angle of cord arrangement layers constituting a belt of a new tire even in a stand tire with little bulge.

Furthermore, even if the unvulcanized tread rubber flows outward in the tire width direction, the intersection angle between the cords constituting the third and fourth cord arrangement layers and the tire equatorial plane is the same as that of the third and fourth cords in a new tire. It is slightly larger than the intersection angle of the cords of the fourth cord arrangement layer. Therefore, even in the case of a retreaded tire, the tension acting on the belt can be made approximately the same as that of a new tire, and the relative movement thereof can be suppressed. In addition, in the tire shown in FIG. 1, the first cord arrangement layer has a hollow structure in which the center portion in the width direction is cut out, but the cord arrangement layer does not have a hollow structure. There is no difference in what has been described above.

[0019]

EXAMPLE A comparative test was conducted using the tire shown in FIG. 2 that was retreaded according to this method and the tire that was retreaded according to the conventional method. The size of the tires used in the comparison test was RTR900R20 M789, and each tire had a carcass comprising one layer of radial array cords made of steel cords, reinforced with a belt consisting of four layers of cord arrays. be.

[0020]

Inventive Tire 1 The first cord arrangement layer 12 is made of steel cords extending upward to the right, the angle of the cords with the tire equatorial plane is approximately 50°, and the tire tread width T (= 190 mm) is 75°. % to 85%, and
The second cord arrangement layer 14 has a removed portion of 20% to 27% of the tire tread width T in the center thereof, and is made of steel cords extending upward to the right, and the angle formed by the cords with the tire equatorial plane. is approximately 20°, and the tire tread width T
The third cord arrangement layer 16 has a width of 75% to 85% of
consists of a steel cord extending upward to the left, the angle of the cord with the tire equatorial plane is approximately 20°, and the width is 75% to 85% of the tire tread width T, and
The fourth cord arrangement layer 18 is made of steel cords extending upward to the left, and the angle between the cords and the tire equatorial plane is approximately 20 degrees, and is 36% to 45% of the tire tread width T.
A retreaded tire made by vulcanizing and molding a green tire with a width of 50%.

[0021]

Inventive Tire 2: The third cord arrangement layer 16 is made of steel cords extending upward to the left, and the angle between the cords and the tire equatorial plane is approximately 18°, which accounts for 75% to 85% of the tire tread width T. The fourth cord arrangement layer 18 is made of steel cords extending upward to the left, and the angle between the cords and the tire equatorial plane is approximately 18.
A retreaded tire obtained by vulcanizing and molding a green tire having the same structure as Invention Tire 1, except that the tire tread width T is 36% to 45% of the tire tread width T.

[0022]

[Comparative Tire] A green tire having the same structure as Invention Tire 1 or 2 was processed in a mold, except that the angle between each of the third and fourth cord arrangement layers with the tire equatorial plane was approximately 22°. Retreaded tires molded with sulfur.

[0023]

[Test method] Each test tire was mounted on a regular drum, the regular internal pressure was applied, and the tire was run while being pressed against the drum with 190% of the regular load, and the distance traveled until failure occurred was determined.

[0024]

[Test results] The results are shown in Figure 3. In FIG. 3, the horizontal axis represents the traveling distance, and the vertical axis represents the angle that the third and fourth cord arrangement layers make with the tire equatorial plane. In addition,
▲ in the figure indicates a new tire. As is clear from this figure, it can be seen that the tire to which the method of the present invention is applied has improved belt durability compared to the retreaded tire to which the conventional method is applied.

[0025]

According to the method of the present invention, it is possible to obtain a retreaded tire with improved belt durability compared to conventional methods.

[Brief explanation of the drawing]

FIG. 1 is a developed view of a retreaded tire belt to which the method of the present invention is applied.

FIG. 2 is a radial cross-sectional view of a retreaded tire to which the method of the present invention is applied.

FIG. 3 is a diagram showing the results of a comparative test of a retreaded tire to which the method of the present invention is applied and a retreaded tire to which the conventional method is applied.

[Explanation of symbols]

10 Belt 12 First code arrangement layer 14 Second code arrangement layer 16 Third code arrangement layer 18 Fourth code arrangement layer 20 Unvulcanized tread rubber

Claims (1)

[Scope of Claims] [Claim l] A carcass consisting of a toroid-shaped radially arranged cord ply spanning between a pair of bead parts to reinforce the sidewall part connected to the bead part and the tread part forming the tire tread. However, when retreading a pneumatic radial tire in which a belt consisting of three or more cord array layers is arranged along the outer circumference of the crown of the carcass, two layers of cord array layers located on the inside of the tire are left behind. The outer cord array layer and tread rubber are removed to form a base tire, and then two new cord array layers are formed, the cords of which are connected to the cords of the remaining tire outer cord array layer and the tire equatorial plane. The cords are cut so that they extend in opposite directions to each other, and the angles formed with the tire equatorial plane are less than or equal to the intersection angle between the remaining cord arrangement layer cords on the outside of the tire and the tire equatorial plane, and are pasted on the base tire. A method for retreading a pneumatic radial tire, which further comprises applying tread rubber to form a green tire, applying internal pressure to the green tire, and vulcanizing it in a mold.