JP7029286B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

When an organic fiber cord such as nylon 66 is used for the belt reinforcing layer of a pneumatic tire, as a method of improving impact resistance, for example, increasing the number of cords driven in or increasing the cord diameter can be mentioned. Be done. However, taking such measures has a problem that it leads to a decrease in high-speed durability and an increase in tire mass due to an increase in member mass. In addition, it was difficult to improve steering stability without increasing the mass of the tire.

In response to such a problem, Patent Document 1 aims to provide a pneumatic radial tire capable of achieving both high-speed durability and load durability on the outer peripheral side of the carcass layer 4 in the tread portion 1. In a pneumatic radial tire in which at least one belt layer 6 is arranged on the tire and a belt reinforcing layer 7 formed by winding a reinforcing cord on the outer peripheral side of the belt layer 6 in the tire circumferential direction is arranged, the reinforcing cord of the belt reinforcing layer 7 is arranged. As a hybrid cord obtained by twisting a rayon lower twist yarn and a lyocell lower twist yarn, the twist coefficient α of the upper twist is 1400 ≦ α ≦ 3800, the breaking elongation is 10% or more, and the toughness coefficient β is 1260 or more. It is disclosed to use the code that is.

However, Patent Document 1 does not describe steering stability, and there is room for further improvement in high-speed durability, impact resistance, and steering stability.

Japanese Unexamined Patent Publication No. 2008-265688 Japanese Unexamined Patent Publication No. 2017-19461

In view of the above points, it is an object of the present invention to provide a pneumatic tire capable of improving high-speed durability, impact resistance, and steering stability without increasing the mass of the belt reinforcing layer. do.

In Patent Document 2, a belt layer 7 in which cords are inclined with respect to the tire circumferential direction on the outer peripheral side of the carcass layer 4 in the tread portion 3 and an organic fiber cord on the outer peripheral side of the belt layer are arranged in the tire circumferential direction. In a pneumatic tire provided with a belt reinforcing layer 9 arranged along the line, the cord is made of an aliphatic polyamide fiber as an organic fiber cord of the belt reinforcing layer, and has a 2% stretch load (cN / dtex) and temperature. Although it is disclosed to use a cord having a product of 0.035 to 0.044 with a loss tangent tan δ at 100 ° C., a pneumatic tire capable of reducing rolling resistance while improving flat spot resistance. There is no description about high-speed durability, impact resistance, and steering stability.

The pneumatic tire according to the present invention is a pneumatic tire having a carcass, a belt arranged on the outer periphery of the crown portion of the carcus, and a belt reinforcing layer arranged on the outer periphery of the belt, and the belt reinforcing layer is A cord with a double-twisted structure in which two under-twisted yarns made of filament bundles of aliphatic polyamide fibers are twisted together. The nominal fineness is 4000 dtex or less, and the tensile toughness (J) per cord is 5 J or more. It has an organic fiber cord, and is equipped with a belt reinforcing ply arranged so that its major axis direction is parallel to the outer peripheral surface of the belt. It is assumed that the product of and is 130 or more, and the product of the 2% stretching load (N) per organic fiber cord and the number of fibers (25 mm) is 470 or more.

The aliphatic polyamide fiber can be made of nylon 66.

The cord occupancy rate per unit width in the belt reinforcing ply may be 85% or less.

According to the pneumatic tire of the present invention, excellent high-speed durability, impact resistance, and steering stability can be obtained without increasing the mass of the belt reinforcing layer.

A half cross-sectional view of a pneumatic tire according to an embodiment of the present invention.

Hereinafter, matters related to the practice of the present invention will be described in detail.

The pneumatic tire T of the embodiment shown in FIG. 1 is a pneumatic radial tire, and connects a pair of left and right bead portions 1 and sidewall portions 2 with radial outer ends of the left and right sidewall portions 2. A tread portion 3 provided between the sidewall portions is provided so as to be provided, and a carcass 4 extending across the pair of bead portions is provided.

The carcass 4 is composed of at least one carcass ply whose both ends are locked by an annular bead core 5 embedded in the bead portion 1 from the tread portion 3 through the sidewall portion 2. The carcass ply is formed by arranging carcass cords made of organic fiber cords and the like substantially at right angles to the tire circumferential direction.

A belt 6 is arranged between the carcass 4 and the tread rubber portion 7 on the outer peripheral side (that is, the outer side in the tire radial direction) of the carcass 4 in the tread portion 3. The belt 6 is provided so as to overlap the outer periphery of the crown portion of the carcass 4, and may be composed of one or a plurality of belt plies, usually at least two belt plies. In the present embodiment, the belt ply is on the carcass side. It is composed of two belt plies, a first belt ply 6A and a second belt ply 6B on the tread rubber portion side. The belt plies 6A and 6B are formed by inclining the steel cords at a predetermined angle (for example, 15 to 35 degrees) with respect to the tire circumferential direction and arranging them at predetermined intervals in the tire width direction. Each belt ply has a steel cord coated with coated rubber. The steel cords are arranged so as to intersect each other between the two belt plies 6A and 6B.

A belt reinforcing layer 8 is provided between the belt 6 and the tread rubber portion 7 on the outer peripheral side of the belt 6 (that is, the outer side in the radial direction of the tire). The belt reinforcing layer 8 is a cap ply that covers the belt 6 with its full width by a belt reinforcing ply, and is composed of organic fiber cords whose major axis direction is substantially parallel to the tire outer peripheral direction. That is, the belt reinforcing layer 8 is formed by arranging the organic fiber cords along the tire circumferential direction, and the organic fiber cords are placed at an angle of 0 to 5 degrees with respect to the tire circumferential direction so as to cover the entire width direction of the belt 6. It can be formed by winding it in a spiral shape.

The belt reinforcing layer 8 of the present embodiment is a cord having a double-twisted structure in which two under-twisted yarns made of filament bundles of aliphatic polyamide fibers are twisted together, and has a nominal fineness of 4000 dtex or less, per cord. It has an organic fiber cord having a tensile toughness (J) of 5J or more. Here, "tensile toughness (J)" is obtained by performing a tensile test using a tensile tester after leaving it for 24 hours under a constant temperature condition of 20 ° C. and 65% RH in accordance with JIS L 1017. It is the amount of work (fracture energy) performed from the stress-strain curve (hereinafter, also referred to as the SS curve) to the fracture of the fiber due to stretching. The tensile toughness can be adjusted by the nominal fineness of the organic fiber cord or the like.

The resin used as the aliphatic polyamide fiber is not particularly limited, and is, for example, nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6/66 copolymer, nylon 6/66. Examples thereof include aliphatic polyamide-based resins such as / 610 copolymer, nylon MXD6, nylon 6T, and nylon 6 / 6T copolymer, of which nylon 66 is preferable.

The organic fiber cord is obtained by subjecting a filament bundle of an aliphatic polyamide fiber to a lower twist and twisting two yarns obtained thereby. For example, it can be produced by aligning two lower twisted yarns obtained by twisting filament bundles of aliphatic polyamide fibers in the Z direction and twisting them in the S direction opposite to the twisting direction of the lower twists. The number of twists of the upper twist and the lower twist is not particularly limited, but is preferably 20 to 40 times / 10 cm, and the number of upper twists and the number of lower twists are preferably set to the same value. ..

The cord twisted in this way is usually subjected to a dip treatment using a known adhesive treatment liquid, whereby an organic fiber cord as a dip-treated cord can be obtained.

The nominal fineness of the organic fiber cord is not particularly limited as long as it is 4000 dtex or less, but is preferably 2000 to 3500 dtex, and more preferably 2000 to 3000 dtex. Since the nominal fineness is 4000 dtex or less, it is easy to suppress an increase in tire mass. The nominal fineness of the organic fiber cord is a value obtained by adding the fineness of the two yarns to be twisted together.

The tensile toughness (J) per organic fiber cord is not particularly limited as long as it is 5J or more, but is preferably 5 to 10J. When the tensile toughness (J) is 5J or more, excellent impact resistance can be easily obtained.

The method of forming the belt reinforcing layer 8 on the belt 6 using the organic fiber cord is not particularly limited. For example, a plurality of organic fiber cords aligned and covered with rubber may be spirally wound around a belt 6 of a raw tire, or a wide rubberized sheet in which organic fiber cords are aligned may be wrapped around the belt 6. You may wind it around on top. In this way, a raw tire (green tire) is manufactured in a state where the belt reinforcing layer 8 is wound around the outer peripheral side of the belt 6, and the obtained raw tire is vulcanized and molded to obtain a pneumatic tire.

The product of the tensile toughness (J) per organic fiber cord and the number of threads (25 mm) is 130 or more, preferably 130 to 180, and more preferably 140 to 170. When the product of the tensile toughness (J) and the number of driving pieces (pieces / 25 mm) is 130 or more, excellent impact resistance can be easily obtained.

The product of the 2% stretching load (N) per organic fiber cord and the number of driven fibers (lines / 25 mm) is 470 or more, preferably 470 to 550. When the product of the 2% extension load (N) and the number of driving lines (pieces / 25 mm) is 470 or more, excellent steering stability can be easily obtained. Here, the "2% stretching load (N)" per organic fiber cord is in accordance with JIS L 1017, and is left at a constant temperature of 20 ° C. and 65% RH for 24 hours, and then a tensile tester is used. It is the tensile load (N) when the tensile test is performed and the elongation is 2%.

The 2% stretching load (N) per organic fiber cord is not particularly limited, but is preferably 10 to 20N, more preferably 13 to 18N. The 2% extension load (N) can be adjusted by the number of twists and the like.

The cord occupancy rate per unit width in the belt reinforcing ply is not particularly limited, but is preferably 85% or less, and more preferably 55 to 85%. When the cord occupancy rate is 85% or less, excellent high-speed durability is easily maintained.

The type of the pneumatic tire according to the present embodiment is not particularly limited, and examples thereof include various tires such as passenger car tires and heavy-duty tires used for trucks and buses.

In the above embodiment, the belt reinforcing layer 8 is a cap ply that covers the belt 6 with its full width, but the present invention is not limited to this, and covers the outer end portion of the belt 6 in the tire width direction and its periphery. , The edge ply may be an edge ply, or the edge ply may be a portion in which both ends of the cap ply in the tire width direction are folded back.

Hereinafter, examples of the present invention will be shown, but the present invention is not limited to these examples.

An organic fiber cord having the structure shown in Table 1 below was prepared. The measurement method for the organic fiber cord is as follows.

-Cord diameter (mm): Four obtained organic fiber cords were arranged in parallel so as not to sag, and measured with a dial gauge (leg diameter 9.5 mm).

-Tensile toughness (J): In accordance with JIS L 1017, after leaving for 24 hours under constant temperature conditions of 20 ° C and 65% RH, a tensile test was conducted using a tensile tester, and elongation was performed from the obtained SS curve. The amount of work (destructive energy) to be done until the fiber is destroyed is calculated.

2% extension load (N): According to JIS L 1017, after leaving for 24 hours under constant temperature conditions of 20 ° C and 65% RH, a tensile test was performed using a tensile tester, and when 2% extension was performed. The tensile load (N) was measured.

Further, using the obtained organic fiber cord as a cord for the belt reinforcing layer, a radial tire having a tire size of 225/60 R17 was vulcanized and molded according to a conventional method. For each tire, all the configurations other than the belt reinforcement layer were the same. The steel cord in the belt ply has a structure of 2 + 1 × 0.27, and the number of driving is 19 / inch. The angle of the steel cord in the belt ply (6A) / (6B) was + 25 ° / -25 ° with respect to the tire circumferential direction. The belt reinforcing ply was manufactured by arranging the cords in the number of driving lines shown in Table 1 so that the major axis direction was parallel to the belt surface, and then using a calendar device to make a topping antiverse.

The carcass ply was set to 2 plies with a polyethylene terephthalate code of 1100 dtex / 2 and a number of driving lines of 22/25 mm.

For the obtained toppings, the thickness of the belt reinforcing ply and the cord occupancy were determined. The measurement method is as follows.

-Thickness of belt reinforcing ply: It is the thickness as a belt reinforcing ply formed by covering an organic fiber cord with a coated rubber, and was measured with a dial gauge (leg diameter 9.5 mm).

-Cord occupancy rate (%) = (cord diameter (mm) x number of threads (25 mm)) x 100/25 (mm)

For each of the obtained pneumatic tires, the mass, impact resistance, steering stability, and high-speed durability of the belt reinforcing layer were evaluated. The evaluation method of each evaluation item is shown below. In Comparative Examples 2 and 3, the mass of the belt reinforcing ply increased, and in Comparative Example 3, the impact resistance was inferior to that of the conventional example. Therefore, the steering stability and the high-speed durability were not evaluated.

-Mass of belt reinforcing layer: The total mass of the belt reinforcing plies used per tire, and the total mass of the belt reinforcing plies of the conventional example is expressed as an index as 100. The smaller the number, the lighter it is.

-Impact resistance: The topping fabric topping the organic fiber cord with rubber was vulcanized, and the obtained rubber composite was used as a sample. Using a tensile tester (Autograph manufactured by Shimadzu Corporation), use a metal rod (tip shape: hemispherical, diameter: 1 cm) at a speed of 5 mm / min to break the organic fiber cord or sample. I pushed it until it penetrated. When the above condition was reached, the test was terminated and the total amount of energy up to the maximum point was measured. The conventional example is expressed in exponential notation as 100. The larger the index, the better the impact resistance.

-Maneuvering stability: Each tire incorporated with an internal pressure of 250 kPa was mounted on a test vehicle with a displacement of 2000 cc, and three trained test drivers ran the test course to evaluate the feeling. The scoring was performed on a 10-point scale, the feeling was evaluated by relative comparison with the conventional example as 6, and the conventional example was displayed as an exponential notation with 100. The larger the index, the better the steering stability.

High-speed durability: Measured as follows by a drum tester having a rotating drum having a diameter of 1700 mm made of steel having a smooth surface and having a smooth surface in accordance with FMVSS109 (UTQG). The test tire was assembled to the JIS standard rim at an internal pressure of 220 kPa (2.2 kgf / cm ² ), and the load was 88% of the maximum load specified by JATTA. After running-in at a speed of 80 km / h, the vehicle was allowed to cool once, the air pressure was adjusted again, and then the main operation was performed. The main running was started from 120 km / h, and thereafter, the speed was increased by 8 km / h every 30 minutes, and the car was run until a failure occurred. The total mileage of the main run up to the occurrence of a failure is expressed as an index with the conventional example as 100. The larger the index, the better the high-speed durability.

The results are as shown in Table 1, and Examples 1 and 2 are excellent in impact resistance, steering stability, and high-speed durability while maintaining the light weight of the belt reinforcing ply as compared with the conventional example. rice field.

In Comparative Example 1, the tensile toughness (J) per organic fiber cord was out of the predetermined range, and the high-speed durability was inferior to that of the conventional example.

In Comparative Example 2, the nominal fineness of the organic fiber cord and the product of the 2% stretching load (N) per organic fiber cord and the number of driven fibers (2 / 25 mm) are out of the predetermined range, and are compared with the conventional example. However, the mass of the belt reinforcement ply increased.

In Comparative Example 3, the product of the tensile toughness (J) per organic fiber cord and the number of driven fibers (25 mm) is out of the predetermined range, and the mass of the belt reinforcing ply is increased as compared with the conventional example. However, the impact resistance was inferior.

In Comparative Example 4, the tensile toughness (J) per organic fiber cord and the product of the 2% extension load (N) per organic fiber cord and the number of driven fibers (25 mm) are out of the predetermined range. Yes, the high-speed durability was inferior to that of the conventional example.

The pneumatic tire of the present invention can be used in various vehicles such as passenger cars, light trucks, and buses.

T ... Tire 1 ... Bead part 2 ... Sidewall part 3 ... Tread part 4 ... Carcass 5 ... Bead core 6 ... Belt 6A ... 1st belt ply 6B ... 2nd belt ply 7 ... Tread rubber part 8 …… Belt reinforcement layer

Claims (3)

A pneumatic tire having a carcass, a belt arranged on the outer periphery of the crown portion of the carcass, and a belt reinforcing layer arranged on the outer periphery of the belt.
The belt reinforcing layer is a cord having a double-twisted structure in which two under-twisted yarns made of filament bundles of aliphatic polyamide fibers are twisted together, and has a nominal fineness of 4000 dtex or less and tensile toughness per cord (tension toughness per cord). It has an organic fiber cord in which J) is 5J or more, and has a belt reinforcing ply arranged so that the major axis direction of the organic fiber cord is parallel to the outer peripheral surface of the belt.
The product of the tensile toughness (J) per organic fiber cord and the number of driving (25 mm) is 130 or more, and the 2% extension load (N) and the number of driving (2) per organic fiber cord. / 25 mm) is a pneumatic tire characterized by having a product of 470 or more. The pneumatic tire according to claim 1, wherein the aliphatic polyamide fiber is made of nylon 66. The pneumatic tire according to claim 1 or 2, wherein the cord occupancy rate per unit width in the belt reinforcing ply is 85% or less.

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