JP2018130974A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which makes it possible to reduce environmental load by use of recycled polyethylene terephthalate fibers while maintaining load durability and stability well.SOLUTION: In the pneumatic tire which includes a carcass layer 4 installed in a predetermined manner between a pair of toes of bead 3, 3, a bead core 5 buried in each of the toes of bead 3 and a bead filler 6 disposed on an outer periphery of the bead core 5, the carcass layer 4 is constituted of a recycled polyethylene terephthalate fiber yarn and a high strength fiber yarn as a carcass cord and contains a plurality of composite cords of which the twist coefficient K ranges between 1600 and 2400 and height BH of the bead filler 6 ranges between 30 mm and 70 mm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire using recycled polyethylene terephthalate fibers as a material for carcass cords. More specifically, while maintaining good load durability and steering stability, the use of recycled polyethylene terephthalate fibers reduces environmental impact. The present invention relates to a pneumatic tire.

  The pneumatic tire typically includes a carcass layer mounted between a pair of bead portions, a bead core embedded in each of these bead portions, and a bead filler disposed on the outer periphery of the bead core, The carcass layer has a structure wound around the bead core from the inside of the tire to the outside.

  In such a pneumatic tire (particularly, a high performance tire), it has been proposed to use a composite cord in which a polyester fiber yarn and an aromatic polyamide fiber yarn are twisted together as a carcass cord constituting a carcass layer (for example, Patent Documents 1 and 2). In such a composite cord, the aromatic polyamide fiber yarn contributes to the improvement of handling stability, and it becomes possible to ensure good durability by combining the polyester fiber yarn with the aromatic polyamide fiber yarn. Has been.

  On the other hand, in recent years, reduction of environmental load is regarded as a technical issue of tires, and from such a viewpoint, it is considered to use recycled polyethylene terephthalate fibers recycled from PET bottles as a material for carcass cords. However, since the elastic modulus of recycled polyethylene terephthalate fiber is lower than that of general-purpose polyethylene terephthalate fiber, when a composite cord is formed by twisting recycled polyethylene terephthalate fiber yarn and aromatic polyamide fiber yarn together, Since the rigidity becomes insufficient, there is a problem that the steering stability during high-speed traveling cannot be sufficiently ensured.

International Publication No. 2009/63913 JP 2012-30737 A

  An object of the present invention is to provide a pneumatic tire that can reduce environmental load by using recycled polyethylene terephthalate fiber while maintaining good load durability and steering stability.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. A bead core disposed between the pair of bead portions, a bead core embedded in each of the bead portions, and an outer periphery of the bead core. In a pneumatic tire having a bead filler arranged in
The carcass layer is composed of a recycled polyethylene terephthalate fiber yarn and a high-strength fiber yarn as a carcass cord, and includes a plurality of composite cords having a twist coefficient K expressed by the following formula (1) in the range of 1600 to 2400,
The bead filler has a height in the range of 30 mm to 70 mm.
K = T√D (1)
However, T: Number of twists of the cord (times / 10cm)
D: Total fineness of cord (dtex)

  In the present invention, as the carcass cord of the carcass layer, a composite cord comprising a recycled polyethylene terephthalate fiber yarn and a high-strength fiber yarn and having a twist coefficient K in the range of 1600 to 2400, more preferably in the range of 2100 to 2400 is used. Thus, while the high-strength fiber yarn contributes to the improvement of handling stability, it is possible to exhibit good load durability based on the low elastic properties of the recycled polyethylene terephthalate fiber yarn. In addition, by setting the height of the bead filler in the range of 30 mm to 70 mm, more preferably in the range of 50 mm to 65 mm, it becomes possible to compensate for insufficient rigidity of the composite cord and to exhibit good steering stability. . As a result, the environmental load can be reduced by using the recycled polyethylene terephthalate fiber while maintaining good load durability and steering stability of the pneumatic tire.

  In the present invention, the high-strength fiber yarn means a yarn having a tensile strength of 8 cN / dtex or more. The tensile strength here refers to the tensile strength (cN / dtex) measured in accordance with JIS-L1017 “Test method for chemical fiber tire cord” under the conditions of a grip interval of 250 mm and a tensile speed of 300 ± 20 mm / min. is there. As such a high-strength fiber yarn, it is preferable to employ an aromatic polyamide fiber yarn.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is sectional drawing which shows the composite cord used for the carcass layer of the pneumatic tire of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIG. 2 shows a composite cord used for the carcass layer.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, And a pair of bead portions 3 disposed inside the wall portion 2 in the tire radial direction.

  A carcass layer 4 including a plurality of carcass cords extending in the tire radial direction is mounted between the pair of bead portions 3 and 3. An annular bead core 5 is embedded in each bead portion 3, and a bead filler 6 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 5. The carcass layer 4 is wound around the bead core 5 from the inside to the outside of the tire.

  On the other hand, on the outer peripheral side of the carcass layer 4 in the tread portion 1, a plurality of belt layers 7 are embedded over the entire circumference of the tire. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. As the reinforcing cord of the belt layer 7, for example, a steel cord is preferably used.

  On the outer peripheral side of the belt layer 7, at least one belt reinforcing layer 8 in which reinforcing cords are arranged at an angle of 5 ° or less with respect to the tire circumferential direction is disposed for the purpose of improving high-speed durability. . It is desirable that the belt reinforcing layer 8 has a jointless structure in which a strip material formed by aligning at least one reinforcing cord and covering with rubber is continuously wound in the tire circumferential direction. As the reinforcing cord of the belt reinforcing layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In the pneumatic tire, a composite cord 20 as shown in FIG. 2 is used as a carcass cord constituting the carcass layer 4. The composite cord 20 has a structure in which at least one twisted yarn 21 made of recycled polyethylene terephthalate fiber yarn and at least one twisted yarn 22 made of high-strength fiber yarn are twisted together. Each of the lower twisted yarns 21 and 22 is given a unidirectional twist, and the composite cord 20 is given a twist in the opposite direction to the lower twisted yarns 21 and 22.

  The fineness of the recycled polyethylene terephthalate fiber yarn constituting the composite cord 20 is set in the range of 800 dtex to 2500 dtex, and the fineness of the high strength fiber yarn constituting the composite cord 20 is set in the range of 800 dtex to 2500 dtex. The fineness is preferably set in the range of 1600 dtex to 5000 dtex. In the composite cord 20, the fineness of the aromatic polyamide fiber yarn is preferably 0.8 to 1.2 times the fineness of the recycled polyethylene terephthalate fiber yarn. By selecting such a fineness, it becomes possible to exhibit good characteristics as a carcass cord of a tire, and both load durability and steering stability of the tire can be achieved.

  Examples of the high-strength fiber yarn include high-strength organic fiber yarn made of aromatic polyamide (aramid), polyparaphenylenebenzoxazole (PBO), polyolefin ketone (POK), etc., or high-strength inorganic fiber yarn represented by carbon fiber. Among them, it is preferable to employ an aromatic polyamide fiber yarn. That is, as the carcass cord constituting the carcass layer 4, it is preferable to use a composite cord 20 formed by twisting recycled polyethylene terephthalate fiber yarn and aromatic polyamide fiber yarn.

In the composite cord 20, the twist coefficient K represented by the following formula (1) is set in the range of 1600 to 2400.
K = T√D (1)
However, T: Number of twists of the cord (times / 10cm)
D: Total fineness of cord (dtex)

  By selecting such a twist coefficient K, fatigue resistance and steering stability can be sufficiently ensured. Here, if the twist coefficient K is less than 1600, the fatigue resistance is lowered and the load durability is deteriorated. Conversely, if it exceeds 2400, the rigidity is lowered and the steering stability becomes insufficient. In particular, the twist coefficient K is preferably in the range of 2100 to 2400. The number of twists of the composite cord 20 is preferably in the range of 53 times / 10 cm to 63 times / 10 cm, for example.

  Moreover, in the said pneumatic tire, as shown in FIG. 1, height BH of the bead filler 6 is set to the range of 30 mm-70 mm. The height BH of the bead filler 6 is a height measured along the tire radial direction. The composite cord 20 including the recycled polyethylene terephthalate fiber yarn tends to have low rigidity. However, by increasing the height BH of the bead filler 6 as described above, the lack of rigidity of the composite cord 20 can be compensated for good steering stability. It becomes possible to demonstrate sex. Here, if the height BH of the bead filler 6 is less than 30 mm, sufficient rigidity cannot be obtained, so that the steering stability during high speed running deteriorates. Conversely, if the height BH is greater than 70 mm, the rubber amount increases. Since the rolled-up portion of the carcass layer 4 is likely to generate heat, the load durability is deteriorated. In particular, the height BH of the bead filler 6 is preferably in the range of 50 mm to 65 mm.

  In the pneumatic tire described above, as the carcass cord of the carcass layer 4, a composite cord 20 made of recycled polyethylene terephthalate fiber yarn and high-strength fiber yarn and having a specific twist coefficient K is used. By increasing the length BH, even when the composite cord 20 includes a recycled polyethylene terephthalate fiber yarn, the load durability and the handling stability of the pneumatic tire can be favorably maintained. As a result, the recycled polyethylene terephthalate fiber can be used as a material for the carcass cord, and the environmental load can be reduced.

  In the above-described embodiment, the embodiment in which the single carcass layer 4 is mounted between the pair of bead portions 3 and 3 has been described. However, the present invention provides a pneumatic tire including at least one carcass layer. It can be applied to. Therefore, it is possible to mount a plurality of carcass layers between a pair of bead portions according to the required tire rigidity, and to apply a predetermined composite cord as the carcass cord of each carcass layer.

  In a pneumatic tire having a tire size of 235 / 60R18 and having one carcass layer mounted between a pair of bead portions, the cord material, cord structure, twist coefficient K, and bead filler height BH of the carcass layer are Conventional tires set as shown in Table 1, Comparative Examples 1 to 4 and Examples 1 to 5 were manufactured.

  In the conventional example, as the carcass cord, a composite cord (PET + aramid) obtained by twisting a single twisted yarn made of a general-purpose polyethylene terephthalate fiber yarn and a single twisted yarn made of an aromatic polyamide fiber yarn was used. In Comparative Examples 1 to 4 and Examples 1 to 5, as a carcass cord, a composite cord obtained by twisting together one under-twist yarn made of recycled polyethylene terephthalate fiber yarn and one under-twist yarn made of aromatic polyamide fiber yarn (Regenerated PET + aramid) was used.

  These test tires were evaluated for load durability and steering stability by the following evaluation methods, and the results are also shown in Table 1.

Load durability:
Each test tire is assembled on a wheel with a rim size of 18 × 8J, the air pressure is set to 220 kPa, and a drum tester equipped with a drum with a diameter of 1707 mm made of steel with a smooth surface conforming to the durability performance test of JIS-D4230 is used. , Control the ambient temperature to 38 ± 3 ° C, set the running speed to 81 km / h, and increase the load from 85% of the maximum load specified by JATMA to 15% of the maximum load every 4 hours until the tire breaks The travel distance was measured. However, the final load was 280% of the maximum load, and the vehicle continued running until the failure occurred with the load condition. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the load durability.

Steering stability:
Each test tire was assembled on a wheel with a rim size of 18 × 8 J and mounted on a test vehicle, the air pressure was set at 220 kPa, and the sensory evaluation by a test driver was performed on the test course for the driving stability at high speed. The evaluation results are shown as index values with the conventional example being 100. The larger the index value, the better the steering stability.

  As can be seen from Table 1, the tires of Examples 1 to 5 are both excellent in load durability and handling stability in comparison with the conventional example, although the recycled material ratio of the carcass cord is 50% by weight. It was.

  On the other hand, in the tire of Comparative Example 1, the general-purpose polyethylene terephthalate fiber yarn constituting the carcass cord in the conventional example is simply replaced with the regenerated polyethylene terephthalate fiber yarn. The sex was decreasing. In the tire of Comparative Example 2, the handling stability is improved by increasing the bead filler height BH compared to Comparative Example 1, but the load durability is reduced because the bead filler height BH is too large. It was. Further, in the setting as in Comparative Example 3, the load durability was lowered, and in the setting as in Comparative Example 4, the steering stability was lowered.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 20 Composite cord 21 Reinforced yarn of recycled polyethylene terephthalate fiber yarn 22 Aromatic polyamide fiber yarn (high strength fiber yarn) Lower twisted yarn

Claims (4)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. A pneumatic tire having a carcass layer mounted between the pair of bead parts, a bead core embedded in each of the bead parts, and a bead filler disposed on the outer periphery of the bead core,
The carcass layer is composed of a recycled polyethylene terephthalate fiber yarn and a high-strength fiber yarn as a carcass cord, and includes a plurality of composite cords having a twist coefficient K expressed by the following formula (1) in the range of 1600 to 2400,
The pneumatic tire according to claim 1, wherein a height of the bead filler is in a range of 30 mm to 70 mm.
K = T√D (1)
However, T: Number of twists of the cord (times / 10cm)
D: Total fineness of cord (dtex)   The pneumatic tire according to claim 1, wherein the twist coefficient K is in a range of 2100 to 2400.   The pneumatic tire according to claim 1 or 2, wherein a height of the bead filler is in a range of 50 mm to 65 mm.   The pneumatic tire according to claim 1, wherein the high-strength fiber yarn is an aromatic polyamide fiber yarn.

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