JP2006088719A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for guaranteeing excellent controllability and stability by complimenting belt rigidity without lowering load durability of a carcass layer. <P>SOLUTION: In this radial tire, at least one layer of a plurality of belt layers 7 is constituted of a steel belt layer, and the carcass layer 4 is constituted of at least two layers of organic fiber cord layers 4a and 4b. The organic fiber cord layers 4a and 4b are made of a doubled and twisted cord that first twisted yarn of aliphatic polyketone fibers of 500 to 2,500 dtex and first twisted yarn of nylon 66 fibers of 400 to 2,400 dtex are finally twisted. A fineness ratio Dp/Dn of fineness Dp of the first twisted yarn of the aliphatic polyketone fibers and a fineness Dn of the first twisted yarn of the nylon 66 fibers in the doubled and twisted cord is ≥1.02. A twist coefficient α of the final twisting is 1,700 to 3,200. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire, and more particularly, to a pneumatic radial tire in which belt rigidity can be complemented by a carcass layer.

  As a part of weight reduction of pneumatic tires, there is a method in which a steel belt layer is formed of a single wire or a part thereof is replaced with an organic fiber cord belt layer. However, when the weight of the belt layer is reduced in this way, there is a problem in that steering stability is lowered because belt rigidity is lowered. Conventionally, as a measure to supplement such a decrease in belt rigidity, the carcass layer is composed of a plurality of layers, the angle of the carcass cord with respect to the tire equator is smaller than 90 °, and the layers are crossed with each other. Many proposals have been made for a radial structure (Patent Document 1, etc.).

However, even if the semi-radial structure is used as described above, if the carcass cord is an organic fiber cord having a low elastic modulus such as a nylon 66 fiber cord, it cannot be said that the effect of supplementing the decrease in belt rigidity is sufficient. When a high elastic modulus cord such as an aromatic polyarimide fiber is used, although it is sufficient to compensate for a decrease in rigidity, there is a problem that it tends to fail early because of its poor compression fatigue resistance. However, the above-mentioned patent document 1 or the like does not propose measures for solving these problems.
JP-A-11-91311

  An object of the present invention is to provide a pneumatic radial tire that complements belt rigidity without deteriorating load durability of a carcass layer and ensures excellent steering stability.

  The pneumatic radial tire of the present invention that achieves the above object is a pneumatic radial tire in which at least one of a plurality of belt layers is constituted by a steel belt layer, and a carcass layer is constituted by at least two organic fiber cord layers. The organic fiber cord layer is composed of a twisted cord obtained by twisting a twisted yarn of an aliphatic polyketone fiber of 500 to 2500 dtex and a twisted yarn of a nylon 66 fiber of 400 to 2400 dtex, and the aliphatic polyketone fiber in the twisted cord The fineness ratio Dp / Dn of the fineness Dp of the lower twisted yarn and the fineness Dn of the lower twisted yarn of the nylon 66 fiber is 1.02 or more, and the twist coefficient α of the upper twist is 1700-3200.

  As described above, according to the pneumatic radial tire of the present invention, as a cord constituting the carcass layer, a low elastic modulus nylon 66 fiber excellent in compression fatigue resistance is used as a twisted yarn of a high elastic modulus aliphatic polyketone fiber. The belt rigidity is reduced by twisting the lower twisted yarn into a hybrid structure, specifying the fineness of both lower twisted yarns, and increasing the fineness ratio Dp / Dn to 1.02 or more and increasing the aliphatic polyketone fiber side. Even in such a case, since the reduction in the belt rigidity is complemented without reducing the load durability of the carcass layer, excellent steering stability can be ensured.

  In the present invention, the belt layer is composed of two or more layers, and at least one of them is a steel belt layer. Preferably, a lighter belt layer is used, and a belt composed of a single wire and composed of two steel belt layers, or one composed of one steel belt layer and one organic fiber cord belt layer is preferable. . The organic fiber cord belt layer preferably uses a high elastic fiber cord such as an aramid fiber or an aliphatic polyketone fiber.

  The carcass layer is composed of at least two organic fiber cord layers, preferably two organic fiber cord layers, in order to complement the belt stiffness when the belt stiffness is reduced due to the weight reduction of the belt layer. More preferably, at least two organic fiber cord layers have a semi-radial structure in which cords cross each other between the layers. Moreover, as a semi-radial structure, in order to make the belt rigidity complementing operation most efficient, it is preferable that the angle of the carcass cord with respect to the tire equator is in the range of 65 to 87 °.

The organic fiber cord layer constituting the carcass layer is composed of a high-elasticity aliphatic polyketone fiber represented by the following chemical formula (1) and a low-elasticity nylon 66 fiber as a lower twisted yarn, and these two lower twisted yarns. It is composed of a twisted cord that is twisted by giving an upper twist. The aliphatic polyketone fiber in the twisted cord mainly contributes to rigidity complementation, and the nylon 66 fiber mainly covers the low compression fatigue property of the aliphatic polyketone fiber.
_{- (CH 2 -CH 2 -CO)} n - (R-CO) m - ··· (1)
However, the relationship between n and m is 1.05 ≧ (n + m) /n≧1.00, and R is an alkylene group having 3 or more carbon atoms.

  As described above, the lower twist yarn of the aliphatic polyketone fiber in the twisted cord constituting the carcass layer has a fineness of 500 to 2500 dtex, and the lower twist yarn of nylon 66 fiber has a fineness of 400 to 2400 dtex. In addition, the total fineness of the twisted cord obtained by combining the two lower twisted yarns is preferably 900 to 4900 dtex.

  When the fineness of the aliphatic polyketone fiber constituting the twisted cord is smaller than 500 dtex, the belt rigidity supplement is insufficient, and when it is larger than 2500 dtex, the load durability of the carcass layer is lowered. On the other hand, when the fineness of the nylon 66 fiber is smaller than 400 dtex, the complementation of the compression fatigue resistance to the aliphatic polyketone fiber becomes insufficient, and the load durability of the carcass layer is lowered. On the other hand, if it is larger than 2400 dtex, the ratio of the nylon 66 fiber becomes large, so that the belt rigidity supplement becomes insufficient.

  In the above-mentioned twisted cord, it is necessary that the fineness ratio Dp / Dn between the fineness Dp of the aliphatic polyketone fiber and the fineness Dn of the nylon 66 fiber is 1.02 or more. By setting the fineness ratio in this way, the proportion of the aliphatic polyketone fiber component in the twisted cord is increased, and the effect of complementing the belt rigidity is made advantageous. In addition, steering stability can be improved.

  The upper limit of the fineness ratio Dp / Dn is not particularly limited, but the upper limit is preferably up to 4.70. When the fineness ratio Dp / Dn is larger than 4.70, there is a problem that the ratio of the nylon 66 fibers to the twisted cord becomes too small, and thus the compression fatigue resistance is not sufficiently supplemented.

In the present invention, more importantly, when an upper twist is applied to the lower twist yarn of the aliphatic polyketone fiber and the lower twist yarn of the low-modulus nylon 66 fiber to form a twisted cord, the following formula (2 ) Defined in the range of 1700 to 3200.
α = N × √ (D / 1.111) (2)
However, N is the number of twists (times / 10 cm), and D is the fineness (dtex).

  When the twist coefficient α of the upper twist is smaller than 1700, the compression fatigue resistance of the twisted cord becomes insufficient, and the load durability of the carcass layer is lowered. On the other hand, when it is larger than 3200, when the weave weave is formed to form a carcass layer, the weave weave is caused to rotate (curls), and the process passability is deteriorated, so that the productivity is lowered or the tire quality is reduced. Worsen.

  Hereinafter, embodiments of the present invention shown in the drawings will be described.

  In the pneumatic radial tire shown in FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is provided on the inner side of the tire, and inner and outer belt layers 7 and 7 are provided on the outer periphery thereof. The belt layers 7 and 7 are both steel belt layers made of a single wire, and are lightened.

  The carcass layer 4 is composed of inner and outer two layers of an inner carcass layer 4a and an outer carcass layer 4b, and the two inner and outer carcass layers 4a and 4b form a semi-radial structure in which the cords cross each other between the layers, and the center of the tread portion ( In the equator, the angle of the carcass cord to the tire equator is 65 to 87 °. Of the two layers, the inner carcass layer 4a is folded at both ends so as to wrap the bead fillers 6 and 6 around the bead cores 5 and 5 from the inside to the outside of the tire. The outer carcass layer 4b reaches the lower side of the bead cores 5 and 5 through the outer sides of the folded ends of the inner carcass layer 4a.

  The two inner carcass layers 4a and the outer carcass layer 4b are composed of organic fiber cords, and the organic fiber cords are composed of a twisted cord obtained by twisting an aliphatic polyketone fiber and a nylon 66 fiber. Has been. The fineness of the lower twist yarn of the aliphatic polyketone fiber in the twisted cord is in the range of 500 to 2500 dtex, the fineness of the lower twist yarn of the nylon 66 fiber is in the range of 400 to 2400 dtex, and the fineness Dp of the lower twist yarn of the aliphatic polyketone fiber and the nylon 66 fiber The fineness ratio Dp / Dn to the fineness Dn of the lower twist yarn is 1.02 or more, and the twist coefficient α of the upper twist is set to 1700-3200.

  The pneumatic radial tire is light in weight because the belt layer is a steel belt layer composed of a single wire. In addition, although the belt rigidity is reduced due to the weight reduction of the belt layer, the carcass layer is composed of a twisted cord of an aliphatic polyketone fiber specified by a specific fineness and a twist coefficient α and a nylon 66 fiber. Complementing the reduction in belt rigidity, it has excellent handling stability. The carcass layer is composed of an aliphatic polyketone fiber having a high elastic modulus, but has excellent load durability.

Example 1, Comparative Examples 1-5
The tire size is 195 / 65R15, the tire structure is shown in FIG. 1, the belt layer is a steel cord layer of a single-layer wire (diameter 0.15 mm), and the carcass layer is at an equator position of 86 ° with respect to the tire equator. A common condition is that a certain semi-radial structure is used, and the composition (fiber type and fineness) of the twisted yarn used in the carcass cord, the number of upper twists, and the twist coefficient α are varied as shown in Table 1. 6 Various types of pneumatic tires (Example 1, Comparative Examples 1 to 5) were manufactured.

  With respect to the above six types of tires, cornering power and load durability were measured as indicators of steering stability by the following test methods, and the results are shown in Table 1.

[Cornering power (CP)]
Using a drum testing machine having a drum diameter of 1707 mm, the cornering power when running at a load of 4.0 kN, a running speed of 10 km / h, and a slip angle of 1 ° was measured.

  Evaluation was shown by the index | index which makes the measured value of the tire of the comparative example 1 100. FIG. The larger the index value, the greater the cornering power and the better the steering stability.

[Load durability]
Using a drum testing machine having a drum diameter of 1707 mm, the running speed was 81 km / h, and the total running distance from the maximum load of 88% up to 13% every 2 hours until breaking was measured.

  Evaluation was shown by the index | index which makes the measured value of the tire of the comparative example 1 100. FIG. A larger index value means better load durability.

Example 2, Comparative Examples 6, 7
In Example 1, the angle of the carcass cord with respect to the tire equator is 90 ° in both layers, and the composition (fiber type, fineness) of the twisted yarn used for the carcass cord, the number of upper twists and the twist coefficient α are shown. 3 types of pneumatic tires (Example 2, Comparative Examples 6 and 7) having the same configuration as in Example 1 except that they were different as in Example 2 were produced.

  For the three types of tires, the cornering power and load durability were measured in the same manner as in the measurement method of the above example, and the results are shown in Table 2. The index value is expressed as an index with Comparative Example 6 as 100.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4a Inner carcass layer 4b Outer carcass layer 5 Bead core 6 Bead filler 7 Belt layer

Claims (5)

  In a pneumatic radial tire in which at least one of a plurality of belt layers is composed of a steel belt layer and a carcass layer is composed of at least two organic fiber cord layers, the organic fiber cord layer is an aliphatic polyketone fiber of 500 to 2500 dtex. A twisted cord obtained by twisting a nylon 66 fiber of 400 to 2400 dtex, and a fineness Dp of the lower twisted yarn of the aliphatic polyketone fiber in the twisted cord and a fineness of the twisted yarn of the nylon 66 fiber. A pneumatic radial tire having a fineness ratio Dp / Dn to Dn of 1.02 or more and an upper twist coefficient α of 1700 to 3200.   The pneumatic radial tire according to claim 1, wherein the carcass layer has a semi-radial structure in which cords cross each other between the layers, and an angle of the cords with respect to a tire equator is 65 to 87 °.   The pneumatic radial tire according to claim 1 or 2, wherein the belt layer includes two steel belt layers made of a single wire.   The pneumatic radial tire according to claim 1 or 2, wherein the belt layer includes one steel belt layer and one organic fiber cord belt layer. The pneumatic radial tire according to any one of claims 1 to 4, wherein a total fineness of the twisted cord is 900 to 4900 dtex.

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