JP7045174B2 - Pneumatic radial tires for passenger cars - Google Patents

Description

The present invention relates to a pneumatic radial tire for a passenger car.

Conventionally, in passenger car tires, an organic fiber cord made of polyester, rayon, nylon or the like has been adopted as a carcass reinforcing material forming the skeleton, that is, a carcass ply cord.

As a means for improving the steering stability of such tires, it is known to increase the rigidity of the carcass by increasing the number of carcass plies. However, there is a problem that the tire weight increases when the number of carcass plies is increased.

In order to improve this problem, Patent Documents 1 to 4 propose to apply a general-purpose steel cord to the carcass layer. However, simply applying the steel cord to the carcass layer may not have the effect of improving steering stability, and the weight of the carcass layer increases as compared with the case where the organic fiber cord is used for the carcass layer. There was a problem that it would end up.

Japanese Unexamined Patent Publication No. 2012-218627 Japanese Unexamined Patent Publication No. 2010-95061 Japanese Patent Application Laid-Open No. 2003-136910 Japanese Unexamined Patent Publication No. 2001-32184

In view of the above points, it is an object of the present invention to provide a pneumatic radial tire for a passenger car capable of improving steering stability without increasing the weight of the carcass layer.

The pneumatic radial tire for a passenger vehicle according to the present invention is a pneumatic tire having a carcass layer spanned between a pair of left and right bead portions, and the carcass layer includes a carcass ply on which a steel cord is arranged. The product (N / inch) of the 2% extension load (N) per steel cord, the number of steel cords driven in the carcass ply (lines / inch), and the number of carcass plies is 6000 or more and 7500 or less. Therefore, it is assumed that the 2% extension load (N) per one steel cord is 80 to 90 N, and the number of steel cords driven in the carcass ply is 70 to 85 / inch .

The carcass layer may consist of one carcass ply.

The diameter of the steel filament constituting the steel cord can be 0.07 to 0.15 mm.

According to the pneumatic radial tire for a passenger car of the present invention, excellent steering stability can be obtained without increasing the weight of the carcass layer.

A half cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing a steel cord having a 1 × n structure 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 of the embodiment shown in FIG. 1 is a pneumatic radial tire for a passenger car, in which a pair of left and right bead portions 1 and sidewall portions 2 and radial outer ends of the left and right sidewall portions 2 are connected to each other. It is configured to include a tread portion 3 provided between both sidewall portions so as to be connected, and a carcass 4 extending straddling between 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 coating a carcass cord made of a steel cord 20 (see FIG. 2) with a coated rubber, and the steel cords 20 are arranged 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, and is composed of organic fiber cords arranged substantially parallel to the tire circumferential 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 angled from 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 carcass 4 according to the present embodiment is the product of the 2% extension load (N) per steel cord, the number of steel cords 20 driven in the carcass ply (inch), and the number of carcass plies (N /). The inch) is preferably 6000 or more and 7500 or less, more preferably 6200 or more and 7300 or less, and further preferably 6400 or more and 7100 or less. When it is 6000 or more, the rigidity of the carcass 4 is high, and excellent steering stability can be easily obtained. Further, when it is 7500 or less, the carcass 4 can follow the expansion of the tire at the time of tire vulcanization molding, the code occupancy rate does not become too high, and the occurrence of separation is easy to be suppressed. Here, "2% extension load (N) per steel cord" is the load at 2% extension when a tensile test is performed in accordance with JIS G 3510.

The 2% extension load (N) per steel cord is not particularly limited, but is preferably 100 N or less, more preferably 70 to 100 N, and even more preferably 80 to 90 N. When it is 100 N or less, the carcass 4 easily follows the expansion of the tire at the time of tire vulcanization molding.

The 2% extension load (N) can be adjusted by the number of steel filaments 12 described later, the diameter d of the steel filament 12, the carbon content (mass%) of the steel filament 12, and the like.

As shown in FIG. 2, the twisted structure of the steel cord 20 used for the carcass 4 according to the present embodiment is preferably a steel cord having a 1 × n structure in which a plurality of steel filaments 12 are twisted together. Due to the 1 × n structure, surface strain due to bending / compressive deformation is unlikely to increase, and excellent durability can be easily obtained. The number (n) of the steel filaments 12 is not particularly limited, but is preferably 3 to 6, more preferably 3 to 5, and even more preferably 3 or 4. When there are three or more, local stress concentration is less likely to occur due to bending and compression, excellent durability is likely to be obtained, and the rigidity of the carcass 4 is increased, so that excellent steering stability is likely to be obtained. .. In addition, when the number of tires is 6 or less, it is easy to suppress an increase in tire weight, the twisted structure of the cord is less likely to collapse, and non-uniformity in the longitudinal direction of the cord is less likely to occur, so that stress concentration is less likely to occur and excellent durability is achieved. It is easy to obtain the sex.

The diameter d of the steel filament 12 is preferably 0.07 to 0.15 mm, more preferably 0.09 to 0.12 mm. When the diameter d of the steel filament 12 is 0.07 mm or more, the rigidity of the steel cord 20 is lowered and the riding comfort is easily improved while maintaining the steering stability when the tire is mounted. When the diameter d is 0.15 mm or less, the filament is less likely to undergo metal fatigue, the fatigue resistance of the carcass ply can be maintained, and the durability of the tire can be easily maintained.

The carbon content (mass%) of the steel filament 12 is not particularly limited, but is preferably 0.80% by mass or more, and more preferably 0.90% by mass or more.

The cord diameter of the steel cord 20 is not particularly limited, but is preferably 0.10 to 0.30 mm, more preferably 0.15 to 0.25 mm. When it is 0.10 mm or more, it is easy to increase the rigidity of the carcass 4, and when it is 0.30 mm or less, it is easy to suppress an increase in tire weight.

The twist pitch is not particularly limited, but is preferably 5.5 to 7.0 mm, more preferably 5.6 to 6.8 mm.

The number of steel cords 20 driven in the carcass ply (line / inch) is not particularly limited, but is preferably 65 to 90 lines / inch, and more preferably 70 to 85 lines / inch.

The number of carcass plies is not particularly limited, but is preferably one from the viewpoint of reducing the tire weight.

In the above embodiment, the twisted structure of the steel cord 20 has been described as having a 1 × n structure, but the present invention is not limited to this, and a plurality of main filaments are arranged in a row without twisting. It may be a steel cord having an n + 1 structure in which the main filament bundle is wrapped with one wrapping filament.

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

A steel cord having the structure shown in Table 1 below was produced. In the carcass layer of the conventional example, a PET cord of 1100 dtex / 2 was used as the organic fiber cord, and the number of carcass plies was two. The other steel cords are all steel cords having a 1 × n structure in which a plurality of steel filaments having the same diameter are twisted together. In Table 1, 4 of "1 x 4 x 0.09" indicates that the number of filaments is 4, and 0.09 indicates that the filament diameter is 0.09 mm.

Each cord having the structure shown in Table 1 was subjected to a tensile test in accordance with JIS G 3510, and a 2% extension load (N) was measured.

The diameter of each cord was measured with a predetermined thickness gauge in accordance with JIS G 3510.

Further, using the obtained cord as a cord for the carcass layer, a radial tire having a tire size of 205 / 55ZR16 94W was vulcanized and molded according to a conventional method. For each tire, all the configurations other than the carcass layer were the same. The steel cord in the belt ply has a 2 + 2 × 0.25 structure, and the number of hammers is 21.2 / inch. The angle of the steel cord in the belt ply (6A) / (6B) was + 27 ° / −27 ° with respect to the tire circumferential direction. The belt reinforcing layer has a 66 nylon cord of 1400 dtex / 2, the number of driven lines is 30/25 mm, and one cap ply and one edge ply are used.

For each of the obtained pneumatic tires, the weight of the carcass layer, tire expandability, and steering stability were evaluated. The evaluation method of each evaluation item is shown below.

-Weight of carcass layer: The total weight of the carcass ply used per tire, and the total weight of the carcass ply of the conventional example is expressed as an index as 100. The smaller the number, the lighter it is.

-Tire expandability: After vulcanization and molding of the pneumatic tire obtained above, those with no defects such as waviness in the carcass are marked with "○" as having excellent expandability, and those with defects are marked with "○" to make the carcass uniform during expansion. It was evaluated as "x" because it could not be expanded.

-Maneuvering stability: A test tire incorporated in a standard rim with an internal pressure of 200 kPa was mounted on a test vehicle with a displacement of 2500 cc, and three trained test drivers ran a test course and performed sensory evaluation. The scoring was a 10-point evaluation, and a relative comparison was made with the conventional tire as 6 points, and the average score of the three people was displayed as an index with the conventional tire as 100. The larger the number, the better the steering stability.

The results are as shown in Table 1. Compared with the conventional examples, in each of Examples 1 to 3, the weight of the carcass layer can be reduced, and excellent tire expandability and steering stability can be obtained. I understood.

In Comparative Example 1, the product (N / inch) of the 2% extension load (N) per steel cord, the number of steel cords driven in the carcass ply (lines / inch), and the number of carcass plies is 7500. The rigidity of the carcass was too high, and the carcass layer could not follow the expansion when the tire was vulcanized, and problems such as waviness were observed in the carcass. In addition, it was not possible to evaluate the steering stability because it was not a runnable tire.

Further, in Comparative Example 2, the product (N / inch) of the 2% extension load (N) per steel cord, the number of steel cords driven in the carcass ply (lines / inch), and the number of carcass plies. Was less than 6000, the rigidity of the carcass was low, and the steering stability was inferior.

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 12 ... Steel filament 20 ... Steel cord d ... Steel filament diameter

Claims (3)

A pneumatic tire with a carcass layer spanned between a pair of left and right bead parts.
The carcass layer comprises a carcass ply with a steel cord.
When the product (N / inch) of the 2% extension load (N) per steel cord, the number of steel cords driven in the carcass ply (line / inch), and the number of carcass plies (N / inch) is 6000 or more and 7500 or less. Yes,
The 2% extension load (N) per steel cord is 80 to 90N.
A pneumatic radial tire for a passenger car, characterized in that the number of steel cords driven in the carcass ply is 70 to 85 / inch . The pneumatic radial tire for a passenger car according to claim 1, wherein the carcass layer is composed of one carcass ply. The pneumatic radial tire for a passenger car according to claim 1 or 2, wherein the diameter of the steel filament constituting the steel cord is 0.07 to 0.15 mm.

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