JP2005205946A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire using steel chords having 3+9+15 structures as reinforcing chords of a carcass ply capable of improving durability further. <P>SOLUTION: This pneumatic radial tire has some reinforcing chords of a carcass ply 4 formed of steel chords 9 with 3+9+15 structures. A fiber reinforcing member 8 covering, with rubber 8b, organic fiber chords 8a arranged at predetermined intervals at terminals 4a of both ends 4A of the carcass ply 4 is arranged to cover the terminals 4a. A product of the thickness (dtex) of the organic fiber chords 8a and arrangement density (pieces/50mm) is set to 1,000 to 50,000 (dtex pieces/50mm). Each of wrapping lengths L1, L2 of the fiber reinforcing member 8 from the terminal ends 4a1 of the terminals 4a to the inside and outside portions of the terminals 4a so as to enclose them is set to 5 to 40 mm and a crossing angle θ between the organic fiber chord 8a and the steel chord 9 is set at 30 to 60°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire that is improved in durability.

  Conventionally, a steel cord having a 3 + 9 + 15 + 1 structure is well known as a reinforcing cord for a carcass layer of a pneumatic radial tire used for heavy-duty vehicles such as trucks and buses. By winding nine filaments on the outer periphery of a core consisting of three filaments and winding one wrapping filament spirally on the outer periphery of a cord in which 15 filaments are twisted on the outer periphery The binding force is secured and the filaments are difficult to break.

  However, in the steel cord using the wrapping filament in this way, fretting wear is likely to occur particularly at the point contact portion between the wrapping filament and the 15 inner filaments, and this causes a decrease in fatigue resistance. It was.

  Therefore, in recent years, as a countermeasure, a pneumatic radial tire using a steel cord having a 3 + 9 + 15 structure from which a wrapping filament is removed as a reinforcing cord for a carcass layer has been proposed (for example, see Patent Document 1). By defining the molding rate of the nine filaments constituting the first sheath and the 15 filaments constituting the second sheath, the fretting wear is improved and the durability is improved while ensuring the binding force of the filament. I am doing so.

However, it has been found that the durability cannot be greatly improved by simply removing the wrapping filament. That is, the removal of the wrapping filament reduces the bending rigidity of the steel cord, which increases the movement of the carcass layer at the end, and as a result, the rubber near the end tends to deteriorate, and in addition, adhesion Since the cut end of the steel cord not subjected to the plating treatment for imparting the property is exposed to the terminal of the carcass layer, the separation is generated from the terminal.
JP-A-7-292585

  An object of the present invention is to provide a pneumatic radial tire that can further improve durability in a pneumatic radial tire using a steel cord having a 3 + 9 + 15 structure as a reinforcing cord of a carcass layer.

  The present invention that achieves the above object is to extend a carcass layer in which reinforcing cords extending in the tire radial direction are arranged at predetermined intervals along the tire circumferential direction between the left and right bead portions, and both end portions of the carcass layer Is folded around the bead core embedded in the bead portion from the inside of the tire to the outside, and the reinforcing cord of the carcass layer is formed of three filaments and a core that is molded and twisted on the outer peripheral side of the core. A pneumatic radial tire comprising a 3 + 9 + 15 structure steel cord comprising a first sheath made of a filament and a second sheath made of 15 filaments molded and twisted around the outer periphery of the first sheath. A fiber reinforcing material in which organic fiber cords arranged at predetermined intervals on the terminal portions at both ends of the layer are covered with rubber is provided so as to wrap the terminal portions, The product of the thickness (dtex) of organic fiber cords and arrangement density (lines / 50mm) is 1000 to 50000 (dtex · lines / 50mm), and the fiber reinforcing material wraps the inside and outside of the terminal part from the terminal part of the terminal part. The wrapping lengths L1 and L2 are 5 to 40 mm, respectively, and the crossing angle θ between the organic fiber cord and the steel cord is 30 to 60 °.

  By wrapping the end portion of the carcass layer with the fiber reinforcing material configured as described above, it becomes possible to effectively restrain the movement of the steel cord at the end portion of the carcass layer. It is possible to suppress the occurrence of separation at the terminal. Therefore, the durability can be further improved in the pneumatic radial tire using the steel cord of the 3 + 9 + 15 structure in which the durability of the carcass layer is improved by removing the wrapping filament and improving the durability due to fretting wear.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a pneumatic radial tire of the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion.

  Between the left and right bead portions 3, a carcass layer 4 in which reinforcing cords extending along the tire radial direction are arranged at predetermined intervals along the tire circumferential direction and embedded in the rubber layer is extended, and both end portions 4A thereof Is folded back from the inside to the outside of the tire so as to sandwich the bead filler 6 around the bead core 5 embedded in the bead portion 3. A plurality of belt layers 7 are arranged on the outer peripheral side of the carcass layer 4 of the tread portion 1. A fiber reinforcing material 8 is provided at the end portions 4a of both end portions 4A of the carcass layer 4 so as to enclose the end portions 4a.

  As shown in FIG. 2, the reinforcing cord of the carcass layer 4 includes a core C composed of three filaments fc, a first sheath S1 composed of nine filaments f1 disposed on the outer peripheral side of the core C, and the first sheath. It is composed of a steel cord 9 having a 3 + 9 + 15 structure including a second sheath S2 made of 15 filaments f2 arranged on the outer peripheral side of S1.

  The three filaments fc of the core C are twisted with the twist direction set in one direction, and the nine filaments f1 with the corrugated patterning of the first sheath S1 are set in the same direction as the core C with the twist direction set in one direction. Fifteen filaments f2 twisted on the outer peripheral side of C and wavyly shaped on the second sheath S2 are twisted on the outer peripheral side of the first sheath S1 with the twist direction reversed, and the core C and the first sheath The filaments fc and f1 constituting S1 are twisted with S, and the filament f2 constituting the second sheath S2 is twisted with Z.

  The average mold rate of the nine filaments f1 constituting the first sheath S1 is set in the range of 95 to 105%, and the average mold rate of the 15 filaments f2 constituting the second sheath S2 is set in the range of 70 to 95%. .

  Thereby, the restraining force of the filaments fc, f1, and f2 is ensured while removing the wrapping filament. In addition, by making the average shaping rate of the filament f1 of the first sheath S1 95% or more and the average shaping rate of the filament f2 of the second sheath S2 70% or more, the end of the steel cord 9 is hardly spread, By making the average molding rate of the filaments f1 in one sheath S1 105% or less, the filaments f1 can be arranged uniformly, and the average molding rate of the filaments f2 in the second sheath S2 is 95% or less. As a result, the filament f2 of the second sheath S2 having a molding rate of 100% or more is reduced, so that the shape of the steel cord is stabilized during production and good productivity can be obtained. Preferably, the average molding rate of the filament f1 of the first sheath S1 is 97 to 103%, and the average molding rate of the filament f2 of the second sheath S2 is 72 to 92%.

  As shown in FIG. 3, the fiber reinforcing material 8 is composed of a rubber-covered organic fiber reinforcing layer in which organic fiber cords 8a arranged at predetermined intervals are covered with rubber 8b, and the thickness (dtex) of the organic fiber cords 8a and The product of the array density (lines / 50 mm) is in the range of 1000 to 50000 (dtex · lines / 50 mm).

  Moreover, as shown in FIG. 4, the wrapping lengths L1 and L2 of the fiber reinforcing material 8 that wraps the inside and the outside of the terminal portion 4a from the terminal 4a1 of the terminal portion 4a of the carcass layer 4 are in the range of 5 to 40 mm, respectively. . Furthermore, as shown in FIG. 3, the crossing angle θ between the organic fiber cord 8a and the steel cord 9 is set to 30 to 60 °.

  Thus, in the present invention, the movement of the steel cord 9 at the terminal portion 4a of the carcass layer 4 can be effectively suppressed by wrapping the terminal portion 4a of the carcass layer 4 with the fiber reinforcing material 8 having the above configuration. As a result, the deterioration of the rubber near the terminal portion can be improved, and the occurrence of separation from the terminal a can also be suppressed. Therefore, the durability can be further improved in the pneumatic radial tire using the steel cord 9 having the 3 + 9 + 15 structure in which the wrapping filament is removed and the durability caused by fretting wear is improved as the reinforcing cord of the carcass layer 4. It becomes possible.

  If the product of the thickness (dtex) of the organic fiber cord 8a and the arrangement density (lines / 50mm) is less than 1000 (dtex / lines / 50mm), the reinforcing effect will be insufficient, and the durability will be effectively improved. I can't. On the other hand, even if it exceeds 50000 (dtex / line / 50 mm), the organic fiber cord 8a becomes too dense and the adhesiveness is lowered, so that it is difficult to effectively improve the durability.

  Even if the wrapping lengths L1 and L2 are less than 5 mm, the durability cannot be effectively improved because the reinforcing effect is insufficient. On the other hand, if it exceeds 40 mm, the cost and weight increase is meaningless, which is not preferable.

  Even if the crossing angle θ between the organic fiber cord 8a and the steel cord 9 is smaller than 30 ° or larger than 60 °, the binding force to the steel cord 9 is reduced, so that it is difficult to effectively improve the durability. .

  In the present invention, the wrapping lengths L1 and L2 are preferably set to have a difference of 10 mm or more, thereby reducing the rigidity step in the vicinity of the terminal portion 4a of the carcass layer 4 and reducing the stress concentration. Therefore, durability can be further improved.

  The organic fiber material used for the organic fiber cord 8a is not particularly limited as long as it has excellent adhesiveness to rubber, and examples thereof include nylon, vinylon (polyvinyl alcohol), and POK (polyolefin ketone). More preferably, a highly elastic POK may improve the durability.

  The steel cord 9 has a standard deviation of the molding rate of 5% or less in the nine filaments f1 constituting the first sheath S1, and a standard deviation of the molding rate of 15 in the 15 filaments f2 constituting the second sheath S2. It is sufficient to make the steel cord shape more stable during production.

  In the present invention, the average molding rate and the standard deviation of the molding rate of the steel cord 9 embedded in the carcass layer 4 of the pneumatic radial tire are determined as follows.

  The steel cord taken out from the carcass layer 4 is cut into a cord piece having a length of 10 cm, and the rubber outside the cord piece is removed with a cutter knife. The cord piece is immersed in acetone and heated sufficiently, and then the cord piece is taken out from the acetone and all the cord pieces are separated without plastic deformation of the filament. After the separation, the amplitude H (mm) of the filament piece fa (see FIG. 5) is measured using a projector.

  The molding rate of the filament f1 constituting the first sheath S1 is A1 (%), the amplitude of the filament piece fa of the filament f1 is H1 (mm), and the typing rate of the filament f2 constituting the second sheath S2 is A2 (%), When the amplitude of the filament piece fa of the filament f2 is H2 (mm), the molding rates A1 and A2 are obtained by the following equations.

A1 = (H1 / D1) × 100
A2 = (H2 / D2) × 100
D1 is the diameter (outer diameter) (mm) when nine filaments f1 are arranged in a perfect circle while in contact with each other, and D2 is arranged in a perfect circle while 15 filaments f2 are in contact with each other. It is the diameter (outer diameter) (mm) at the time, and is obtained by the following formula.

D1 = (2 × 3 ^1/2 / 3 + 1) × rc + 2 × r1
D2 = (2 × 3 ^1/2 / 3) × rc + 2 × r1 + 2 × r2
Here, rc is the diameter (mm) of the filament fc of the core C, r1 is the diameter (mm) of the filament f1 of the first sheath S1, and r2 is the diameter (mm) of the filament f2 of the second sheath S2.

  With respect to the nine filaments f1 of the first sheath S1, the molding rate A1 is obtained by the above method, and the average of the molding rates A1 of the nine filaments f1 is set as the average molding rate of the filaments f1 constituting the first sheath S1. . Similarly, each of the 15 filaments f2 of the second sheath S2 is determined by the above-described method to determine the molding rate A2, and the average of the 15 filaments f2 is averaged by the average molding of the filaments f2 constituting the second sheath S2. Rate.

  The standard deviation of the molding rate is the standard deviation of the molding rate of the 36 filaments f1 of the first sheath S1 obtained by cutting the steel cord into four 10 cm long cord pieces, and the second sheath S2. The standard deviation of the molding rate of the 60 filaments f2.

  In order to make the standard deviation of the molding rate in such a small range as described above, the steel cord 9 is preferably twisted by a harassment twisting method in which at least the filaments f1 and f2 are twisted. As shown in FIG. 6, the twisting and twisting method referred to here means that the filament fx is rotated by one rotation every time the filament fx is twisted by one rotation (revolution) from the position a through the positions b, c and d to the position a. How to twist. In addition, x in the figure has shown the one side part of the filament fx.

  Since this steel cord having a twisted and twisted structure adds twist to the filament, uniform molding is possible even at a large molding rate (about 70 to 300%), and the cord can be made difficult to break.

  The standard deviation of the molding rate can be reduced by appropriately adjusting the twisting wire speed, the filament tension, and the like in the steel cord twisting process instead of the rough twisting structure.

  As the filaments fc, f1, and f2, those having a diameter of 0.15 to 0.26 mm can be preferably used.

  The present invention can be preferably used for heavy-duty pneumatic radial tires used in heavy-duty vehicles such as trucks and buses, but is not limited thereto.

  The tire size is the same for 275 / 70R22.5, and a fiber reinforcing material is provided at the end of the carcass layer using a steel cord of 3 + 9 + 15 × 0.17 structure as the reinforcing cord, and the type and thickness of the organic fiber cord (dtex ) And the arrangement density (lines / 50mm) (dtex · lines / 50mm), the wrapping lengths L1, L2 (mm), and the crossing angle θ (°) as shown in FIG. Tires 1 to 4, comparative tires 1 to 5, and conventional tires not provided with fiber reinforcing materials were prepared.

When the durability evaluation test was conducted on each of the test tires by the measurement method shown below, the results shown in Table 1 were obtained.
Durability Each test tire is mounted on a rim with a rim size of 22.5 × 8.25, and the air pressure is set to 900 kPa and attached to a drum testing machine with a drum diameter of 1707 mm. Under conditions of a load of 45 kN and a speed of 45 km / h, the tire The distance traveled until failure occurred was measured, and the result was evaluated as an index value with the conventional tire as 100. The greater this value, the better the durability. In addition, 105 or more is considered to have a remarkable improvement effect.

表１から、本発明タイヤはいずれも１０５以上あり、耐久性を効果的に改善できることがわかる。また、本発明タイヤ４から、包み込み長さＬ１，Ｌ２に差をもたせることにより、耐久性を更に改善できることがわかる。

From Table 1, it can be seen that there are 105 or more tires of the present invention, and the durability can be effectively improved. Further, it can be seen from the tire 4 of the present invention that durability can be further improved by making a difference in the wrapping lengths L1 and L2.

1 is a half sectional view of a tire meridian showing an embodiment of a pneumatic radial tire of the present invention. It is an expanded sectional view of the steel cord used for the reinforcement cord of a carcass layer. It is explanatory drawing of a fiber reinforcement. It is a principal part expanded sectional view of a fiber reinforcement. FIG. 3 is an enlarged side view of a main part of a filament piece taken out from a cord piece of a steel cord. It is explanatory drawing of the harassment twist.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4A End part 4a Terminal part 4a1 Terminal 5 Bead core 6 Bead filler 7 Belt layer 8 Fiber reinforcement 8a Organic fiber cord 8b Rubber 9 Steel cord C Core S1 First sheath S2 First 2 sheath fc, f1, f2 filament

Claims (4)

A bead core having a carcass layer in which reinforcing cords extending in the tire radial direction between the left and right bead portions are arranged at predetermined intervals along the tire circumferential direction, and both ends of the carcass layer are embedded in the bead portion. Folding the tire from the inside to the outside, the carcass layer reinforcing cord is composed of a core composed of three filaments, a first sheath composed of nine filaments that are molded and twisted around the outer periphery of the core, In a pneumatic radial tire composed of a steel cord having a 3 + 9 + 15 structure composed of a second sheath composed of 15 filaments molded and twisted on the outer peripheral side of the first sheath,
A fiber reinforcing material in which organic fiber cords arranged at predetermined intervals on the end portions of the carcass layer are covered with rubber is provided so as to wrap the end portions, and the thickness (dtex) of the organic fiber cords and the arrangement density (main) / 50mm) is 1000 to 50000 (dtex / piece / 50mm), and the wrapping lengths L1 and L2 of the fiber reinforcement that wraps the inside and outside of the terminal part from the terminal part of the terminal part are 5 to 40 mm, respectively. A pneumatic radial tire in which the crossing angle θ between the organic fiber cord and the steel cord is 30 to 60 °.   The pneumatic radial tire according to claim 1, wherein the wrapping lengths L1 and L2 have a difference of 10 mm or more.   The pneumatic radial tire according to claim 1 or 2, wherein a material constituting the organic fiber cord is selected from nylon, polyvinyl alcohol, and polyolefin ketone. 4. The pneumatic radial according to claim 1, wherein the average shaping rate of the filaments constituting the first sheath is 95 to 105% and the average shaping rate of the filaments constituting the second sheath is 70 to 95%. tire.

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