JP2020083143A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire capable of improving high speed durability while reducing tire weight.SOLUTION: A pneumatic tire includes: a carcass; a belt layer in which cords are arranged so as to be tilted with respect to a tire circumferential direction on an outer periphery of a crown part of the carcass; and a belt reinforcing layer in which organic fiber cords are arranged along the tire circumferential direction on the outer periphery of the belt layer. The organic fiber cords are made of an aromatic polyamide fiber, and each has a single twist structure with a fineness of 500 to 3000 dtex and a single twist coefficient of 800 to 2000.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pneumatic tire.

For a pneumatic tire, it has been considered to improve the rigidity in the tire circumferential direction for the purpose of improving durability at high speed running (hereinafter referred to as high speed durability).

An organic fiber cord may be used for the belt reinforcing layer in order to reduce the weight of the tire. In this case, in order to improve the rigidity in the tire circumferential direction, it is necessary to increase the fineness of the organic fiber cord or to increase the number of driven organic fiber cords, but both of them lead to an increase in tire weight. There was a problem.

JP, 2016-68822, A JP, 2014-201136, A JP, 2013-43612, A

In view of the above points, an object of the present invention is to provide a pneumatic tire capable of improving high-speed durability while reducing tire weight.

Regarding the pneumatic tire provided with a belt reinforcing layer made of an organic fiber cord, Patent Document 1 describes a pneumatic tire intended to have both flat spot resistance and abrasion resistance. , High speed durability is not a challenge. Further, since the organic fiber cord is made of an aliphatic polyamide, the effect of improving high-speed durability is insufficient.

Further, Patent Document 2 describes a pneumatic tire for the purpose of suppressing air accumulation and improving high-speed durability, but does not describe the twist coefficient of the organic fiber cord.

Further, Patent Document 3 describes a pneumatic tire provided with a belt cover layer having a reinforcing core having a predetermined structure in order to improve rolling resistance while improving high-speed durability. The reinforcing core has a warp composed of a single twisted cord in which organic fiber multifilament yarns are twisted in one direction, and aramid fiber is described as one example of the material, but regarding the twist coefficient of the organic fiber cord, Is not stated.

The pneumatic tire according to the present invention is a carcass, a belt layer in which cords are arranged in an inclined arrangement with respect to the tire circumferential direction on the outer circumference of the crown portion of the carcass, and an organic fiber cord is provided on the outer circumference of the belt layer along the tire circumferential direction. In a pneumatic tire having an arranged belt reinforcing layer, the organic fiber cord is made of aromatic polyamide fiber having a fineness of 500 to 3000 dtex and has a single twist structure having a twist coefficient of 800 to 2000.

According to the pneumatic tire of the present invention, excellent high-speed durability can be obtained while reducing the tire weight.

1 is a half sectional view of a pneumatic tire according to an embodiment of the present invention.

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

The pneumatic tire according to the embodiment shown in FIG. 1 is a pneumatic radial tire for passenger cars, 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 joined together. The carcass 4 is provided with a tread portion 3 provided between both sidewall portions so as to be connected to each other, and a carcass 4 extending across a 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 to the sidewall portion 2. The carcass ply is formed by arranging carcass cords made of organic fiber cords or 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 of the carcass 4 in the tread portion 3 (that is, on the outer side in the tire radial direction). The belt 6 is provided so as to overlap with the outer periphery of the crown portion of the carcass 4, and can be configured by one or a plurality of belt plies, usually at least two belt plies. The first belt ply 6A and the second belt ply 6B on the tread rubber portion side are composed of two belt plies. The belt plies 6A and 6B are formed by inclining steel cords at a predetermined angle (for example, 15 to 35 degrees) with respect to the tire circumferential direction, and arranging the steel cords at predetermined intervals in the tire width direction. Each belt ply has a steel cord covered with a coating rubber. The steel cords are arranged so as to intersect with 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, on the outer side in the tire radial direction). The belt reinforcing layer 8 is a cap ply that covers the belt 6 with the belt reinforcing ply over its entire width, and is made of organic fiber cords arranged substantially parallel to the tire circumferential direction. That is, the belt reinforcing layer 8 is formed by arranging organic fiber cords along the tire circumferential direction, and the organic fiber cords are formed 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 spirally winding.

The organic fiber cords forming the belt reinforcing layer 8 according to this embodiment are made of aromatic polyamide fibers. The aromatic polyamide fiber is a polyamide having an aromatic skeleton in the main chain, and may be a para aramid or a meta aramid. For example, a known aramid fiber used in the present technical field can be appropriately used.

As the organic fiber cord, a cord having a single twist structure made of the aromatic polyamide fiber is used. That is, an organic fiber cord having a single twist structure is used in which a yarn formed by bundling a large number of aromatic polyamide filaments is twisted in one direction. With the single twist structure, the cord volume can be reduced and the thickness of the belt reinforcing layer 8 can be reduced as compared with the case of using the organic fiber cord with the double twist structure, so that the tire weight can be easily reduced.

The fineness of the organic fiber cord is not particularly limited as long as it is 500 to 3000 dtex, but is preferably 700 to 2800 dtex, and more preferably 800 to 2800 dtex. When it is 500 dtex or more, it is easy to reduce the number of driven organic fiber cords required to obtain a desired tire performance, and as a result, adhesive failure between the organic fiber cord and rubber occurs at the cut end portion of the belt reinforcing ply. Difficult and easy to obtain excellent high speed durability. Further, when it is 3000 dtex or less, the tire weight is easily reduced. Here, the fineness is also called a nominal fineness or a display fineness.

The twist coefficient (K) of the organic fiber cord is not particularly limited as long as it is 800 to 2000, but 900 to 1900 is more preferable. When the twist coefficient is 800 or more, the fatigue resistance of the organic fiber cord can be maintained, and excellent high-speed durability can be easily obtained. When the twist coefficient is 2000 or less, the strength of the belt reinforcing ply is maintained. It is possible to reduce the number of driven organic fiber cords required to obtain a desired tire performance. As a result, the separation between the belt 6A and the belt 6B at the widthwise end portion of the belt 6 and the belt 6 and the belt 6 are performed. Separation between the reinforcing layer 8 and the belt 6 and the carcass 4 is unlikely to occur, and excellent high-speed durability is easily obtained.

Here, the twist coefficient (K) is represented by the following formula (I), T is the number of twists per 10 cm (times/10 cm), D is the nominal fineness (dtex), and P is the aromatic polyamide. The fiber density (g/cm ³ ) is shown.
K=T(D/P) ^1/2 ...(I)
The number of twists (turns/10 cm) per 10 cm of the organic fiber cord is not particularly limited, but may be 25 to 70 turns/10 cm or 25 to 60 turns/10 cm.

The number of organic fiber cords to be driven (lines/25 mm) is not particularly limited, but may be 8 to 24 lines/25 mm or 8 to 21 lines/25 mm.

The type of pneumatic tire according to the present embodiment is not particularly limited, and various tires such as tires for passenger cars and tires for heavy loads used for trucks, buses and the like can be mentioned.

In the above embodiment, the belt reinforcement layer 8 has been described as a cap ply that covers the belt 6 with its entire width, but the present invention is not limited to this, and covers the end of the belt 6 on the outer side in the tire width direction and the periphery thereof. The edge ply may be composed of a portion in which both ends of the cap ply in the tire width direction are folded back.

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

An organic fiber cord having the structure and the number of twists shown in Table 1 below was produced. The produced organic fiber cords were arranged in the number of driven fibers shown in Table 1, and a belt reinforcing ply was produced by using a calendering device as a topping cloth.

The measuring methods for the organic fiber cord and the belt reinforcing ply are as follows.

・Cord diameter: One organic fiber cord is bent to prevent the twist from returning to four, and the cords are arranged in parallel so that they do not sag. 0.5±0.03 mm, load 1666±29.4 mN), and the leg was dropped from a height of about 6.5 mm for measurement.

Cord strength (tensile strength): The tensile strength was measured by conducting a tensile test according to JIS L1017 in a standard condition test room at a temperature of 20±2° C. and a relative humidity (65±4)% specified in JIS L0105.

-Thickness of belt reinforcing ply: Using a belt reinforcing layer member before vulcanization, the member is placed so as not to sag, and a predetermined dial gauge (leg diameter 9.5 ± 0.03 mm, load 1666 ± 29. 4 mN), the leg was dropped from a height of about 6.5 mm, and the member thickness was measured.

-Total ply strength: Tensile strength per 25 mm width of the belt reinforcing layer, which is calculated by multiplying the cord strength by the number of driven belt reinforcing layers and the number of plies.

Further, a radial tire having a tire size of 205/65R15 was vulcanized and molded according to a conventional method using the obtained belt reinforcing ply. All tires had the same structure except the belt reinforcing layer. The cord angle in the belt ply was +21°/-21° with respect to the tire circumferential direction. The belt reinforcing ply has organic fiber cords arranged on the outer periphery of the belt layer such that the major axis direction thereof is parallel to the belt surface.

As the carcass ply, one ply of an organic fiber cord made of polyester having a cord structure of 1670 dtex/2 was formed with 24 fibers/25 mm.

Each of the obtained pneumatic tires was evaluated for tire weight and high speed durability. The evaluation method of each evaluation item is as follows.

Tire weight: Total weight per tire, expressed as an index with the total weight of the tire of the conventional example being 100. The smaller the number, the lighter it is.

High-speed durability: Measured according to FMVSS109 (UTQG). Specifically, a drum tester having a surface of smooth steel and a diameter of 1700 mm was used. The tire internal pressure was 220 kPa and the load was 88% of the maximum load specified by JATMA. After running for 60 minutes at 80 km/h, the system was allowed to cool, the air pressure was adjusted again, and then the actual running was performed. The main running was started from 120 km/h, the speed was gradually increased by 8 km/h every 30 minutes, and the running was continued until a failure occurred. The mileage until the occurrence of a failure was expressed as an index, with the tire evaluation result of Comparative Example 1 being 100. The higher the number, the better the high speed durability.

The results are shown in Table 1, and compared with a conventional example using an organic fiber cord made of nylon 6,6 and having a double twist structure of 940 dtex/2, Examples 1 to 4 all have tire weights. It was found that it can be reduced and excellent high speed durability can be obtained.

Comparative Example 1 is an organic fiber cord having a single twist structure in which the fineness and the twist coefficient are within a predetermined range, but the cord material is made of nylon 6,6, and has a higher high-speed durability than the conventional example. No improvement effect was seen.

Comparative Example 2 is an example in which the fineness of the organic fiber cord is less than the lower limit value, and the high speed durability was inferior as compared with the conventional example.

Comparative Example 3 is an example in which the fineness of the organic fiber cord exceeds the upper limit value, and the tire weight increased as compared with the conventional example.

Comparative Example 4 is an example in which the twisting coefficient of the organic fiber cord is less than the lower limit value, and the high speed durability was inferior to the conventional example.

Comparative Example 5 is an example in which the twisting coefficient of the organic fiber cord exceeds the upper limit value, and the high speed durability was inferior to the conventional example.

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

1...bead part 2...sidewall part 3...tread part 4...carcass 5...bead core 6...belt 6A...first belt ply 6B...second belt ply 7...tread rubber part 8...belt Reinforcement layer

Claims (1)

Air having a carcass, a belt layer in which cords are arranged obliquely with respect to the tire circumferential direction on the outer periphery of the crown portion of the carcass, and a belt reinforcing layer in which organic fiber cords are arranged on the outer periphery of the belt layer along the tire circumferential direction. In the tire containing
The pneumatic tire, wherein the organic fiber cord is made of an aromatic polyamide fiber having a fineness of 500 to 3000 dtex, and has a single twist structure having a twist coefficient of 800 to 2000.

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