JPH06278415A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To aim at a drastic weight lightening of a tire bead and improve low fuel consumption by using a complex cord, which is a combination of a fiber made from a heterocycle contained aromatic polymer containing a specific fiber strength and a polyamide resin through a specific mode, as a bead wire. CONSTITUTION:A complex cord of a fiber made from a hetrocycle contained aromatic polymer of a fiber strength of 18g/D or more and a polyamide resin is used as a bead wire for a radial tire. This complex cord is formed by completely coating a PBO fiber, which is the core material, with a polyamide resin and the volumetric ratio of the fiber in one bead wire is set within the range of 30% to 70%. The above mentioned resin coated wire is further formed so that it can be held by leaving a space between them with an insulation rubber which rubber hardness is 82 to the like are used as a fiber made from a heterocycle contained aromatic polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire equipped with a bead wire which satisfies the requirements of improved fuel economy, improved maneuverability, and easy disposal of the tire by reducing the weight of the tire.

[0002]

2. Description of the Related Art A general bead wire is a bead having a rectangular cross section in which a plurality of hard steel (steel wire) single wires are arranged in parallel, rubber insulation is applied, and a plurality of layers are wound and laminated. There is an overlapping part as shown in.

In recent years, the problem of fuel consumption has been closed up from the viewpoint of energy saving, and not only the weight reduction of a vehicle but also the weight reduction of a tire as a component of the vehicle has become a serious problem. As a bead wire for tires, steel wire is sufficient in strength, but because of its large specific gravity,
Various researches have been conducted on weight reduction of bead wires.

In Japanese Patent Laid-Open No. 56-43010, a high modulus non-metal fiber such as aramid fiber, polyester fiber, carbon fiber, glass fiber and various whiskers having a small specific gravity and a high elastic modulus is used as an alternative to the steel wire. There has been proposed a pneumatic tire using a cord, which is impregnated with a thermosetting resin such as polyurethane, an epoxy resin, or an unsaturated polyester resin as a matrix and cured by heat treatment, in a current strand bead structure of PSR. It is characterized by using a high modulus fiber having an elastic modulus of 10 ⁵ kg / cm ² or more. This bead structure is one in which a bead is directly formed by impregnating a matrix and does not include an insulation rubber. As the matrix, thermoplastic resins such as nylon and polyester, natural rubber, S
Although rubber such as BR may be used, polyurethane and rubber are only exemplified in the embodiment as the most preferable embodiment.

In Japanese Patent Publication No. 35101/1993, a reinforcing wire containing an aromatic polyamide is covered with a resin material containing a thermoplastic resin (first sleeve), and the outside of the resin material having a lower melting temperature than the resin ( 2nd sleeve) and treat at a temperature higher than the resin melting temperature of the 2nd sleeve.
Disclosed is a method for manufacturing a reinforcing wire for a tire, in which the first sleeves of adjacent reinforcing wires of a book are brought into contact with each other to be solidified. In this case, the reinforcing wire material is not in direct contact with each other, but the resin materials of the first sleeve are in contact with (adhered to) each other, so that the bead wires generate a binding force to each other. Then, when external force is applied to the beads, the movement of each bead wire is suppressed and the flexibility of the entire bead is inferior as compared with the case where the beads are not in contact with each other. Therefore, when using a bead wire, a sufficient bead expansion force cannot be obtained.

In Japanese Utility Model Laid-Open No. 64-16901, carbon fibers are used as a thermosetting resin matrix in the longitudinal direction of the resin.
There is disclosed a bead-reinforcing body in which a composite linear body having a strength of 0 kg / mm ² or more is formed into an annular shape. However, carbon fiber is not preferable because it is brittle against the concentration of bending stress when the rim is assembled and the strength is reduced.

In the composite cord in which the organic fiber is impregnated with the thermosetting resin, shear stress concentration occurs when the rim is assembled and unraveled, the bead fiber is damaged, and sufficient bead strength is obtained in the tire hydraulic fracture test. There was a problem of not having.

Further, even if a thermoplastic resin is used, it is difficult to obtain sufficient durability for assembling the rim if the composite cord is impregnated with the resin directly, and the bead expanding force for tightening the rim inward is insufficient. There were also problems such as rim slippage and rim slippage.

Further, polyparaphenylene benzobisoxazole fiber (hereinafter referred to as PBO fiber) or polyparaphenylene benzobisthiazole fiber (hereinafter referred to as PBT) which is a fiber composed of a heterocyclic ring-containing aromatic polymer.
(Composite cords, which are called fibers), are partially exposed on the surface of the cord, but the damage to the fiber is large, that is, the strength is greatly reduced due to the rubbing of the cord and the processor roller during the dip treatment process of adhesive processing. Therefore, there was a problem in processing.

Further, since there is a bead overlap portion, shear stress concentration occurs here, and in a tire hydraulic breakdown test, bead wire breakage first occurs at the unwinding overlap portion, so that high hydrostatic bead strength can be obtained. There was also the problem of not having it.

[0011]

SUMMARY OF THE INVENTION The first object of the present invention is to:
It is a lightweight bead that contributes to low fuel consumption, and the tire bead is soft and easy to twist even if abnormal external force is applied when the rim is assembled or unraveled, and the bead does not break (permanently deform). Moreover, it is to provide a pneumatic radial tire that has sufficient bead expansion force to tighten the rim inward, slips on the rim, does not come off the rim, and has easy disposal.

Secondly, it is to provide a pneumatic radial tire that does not cause the fibers to be damaged by the rubbing of the cord and the processor roller in the dip treatment step of the adhesive processing of the composite cord and the strength of the tire is not deteriorated. Thirdly, it is to provide a pneumatic radial tire having a high hydrostatic bead strength such that a bead wire breakage due to a shear stress concentration does not occur in a tire hydraulic breakdown test.

[0013]

As a result of intensive studies to solve the above problems, the present inventors found that the fiber strength was 1
This can be solved by completely covering PBO fibers of 8 g / D or more, preferably 30 g / D or more with a polyamide resin, and providing a lightweight bead in which the covered wires are held at intervals with an insulation rubber in a pneumatic radial tire. We have found this and completed the present invention.

That is, the present invention is as follows: (1) A bead wire is a composite cord of a fiber and a polyamide resin composed of a heterocycle-containing aromatic polymer having a fiber strength T of 18 g / D or more, and the thermoplastic polyamide resin is a core. The fiber composed of the heterocycle-containing aromatic polymer as the material is completely covered, and the fiber volume ratio in one bead wire is 30 to 70%, and the resin-coated wire is spaced by the insulation rubber. It is a pneumatic radial tire using lightweight beads held open,

(2) The pneumatic material according to (1) above, wherein the resin layer covering the fiber layer composed of the heterocyclic ring-containing aromatic polymer, which is the core material of the composite cord, has a thickness d of 0.02 mm or more. It is a radial tire,

(3) The bead strands of the composite cord are formed by winding a composite cord made of a polyamide resin coated with fibers composed of one heterocyclic ring-containing aromatic polymer. The pneumatic radial tire according to the preceding item (1), in which neither end is in the bead innermost layer strand,

(4) The pneumatic radial tire according to any one of the above items (1) to (3), wherein the fiber composed of the heterocyclic ring-containing aromatic polymer is a PBO fiber or a PBT fiber.

The details of the present invention will be described below. Examples of the fiber composed of a heterocycle-containing aromatic polymer used in the present invention include PBO fiber and PBT.
Fibers. These fibers are fibers that combine the elastic modulus of carbon fibers with the strength and easiness of handling of aramid fibers, and have higher strength and higher modulus than the conventional organic fibers such as carbon fibers and aramid fibers described above. is there. In the present invention, it is preferable to use PBO fiber, and further, the following general formula (I) is used.

[Chemical 1] It is preferable to use a PBO fiber having a cis structure represented by

In the present invention, the total denier number D of the PBO fiber is preferably 3000 <D <25,000, and 30
When it is less than 00, the diameter of one strand is too thin and the bead strand structure becomes bulky, which is not preferable, and when it is more than 25,000, each strand is too thick and the surface strain when bent is too high.
The PBO fiber in the resin is used without twisting or with a slight twist (single twist or twin twist). It is preferable to have a slight twist rather than untwist in terms of alignment.

When the coefficient N _T is expressed by the following equation, N _T = n × (0.139 × 1 / m × D / ρ) ^1/2 × 10
^-3 (where D is the total denier of the cord, ρ is the specific gravity of the cord, n is the number of twists of the cord (times / 10 cm), and m is the number of twists of the lower twisted bundle) 0 ≤ N _T ≤ 0.15 Preferably 0.04 ≦ N _T ≦ 0.1. If N _T exceeds 0.15, the strength is lowered due to twisting loss, which is not preferable.

As the bead fiber of the present invention, carbon fiber,
Glass fibers and the like are not preferable because they are brittle and the strength is reduced with respect to the concentration of bending stress when the rim is assembled. In addition, fibers such as polyethylene terephthalate (PET) are not sufficient in terms of modulus strength and cannot be used as a lightweight bead wire.

As the coating resin which can be used in the present invention, a thermoplastic resin is preferable, and a polyamide resin is most preferable because of its physical properties and adhesiveness with rubber. As the polyamide resin, 66-nylon, 6-nylon, 4,
Examples thereof include 6-nylon, 6,10-nylon, and an aliphatic polyamide of a copolymer or a mixture thereof, and an aliphatic polyamide in which 6,6-nylon accounts for 80% by weight or more is particularly preferable, and its heat resistance is Most preferred is 6,6-nylon or 4,6-nylon because of its high properties.

The PBO fiber strength T of the cord is T
≧ 18 g / D is required, and preferably T ≧ 30 g / D is required. If it is less than 18 g / D, sufficient bead breaking strength cannot be obtained. The fiber volume ratio in the cord is 30 to 70%
If it is less than 30%, the amount of resin increases and the weight becomes high, and sufficient weight reduction cannot be achieved. If it exceeds 70%, there will be insufficient resin to cover the PBO fiber, the requirement of completely covering the fiber of the present invention will not be satisfied, and the bending rigidity sufficient to maintain sufficient roundness during tire molding will be insufficient. No
In addition, the aramid fiber is greatly damaged (reduced strength) during the adhesive dip processing. As described above, the PBO fiber, which is the core material, needs to be completely covered with resin on the fiber circumference, but if it is not completely covered, stress concentration damage during rim assembly and rim unraveling will also occur. In addition, the PBO fiber is greatly damaged during the adhesive dip treatment.

The thickness d of the resin coating layer is 0.02 mm.
The above is necessary. It is preferably 0.05 mm or more, and most preferably 0.08 mm or more. The hardness of the insulation rubber of the bead wire is 80 to
90 is required. If it is less than 80, a sufficient bead expanding force cannot be obtained, and if it exceeds 90, the rubber is too hard and the insulation work becomes difficult.

Further, in order to obtain a sufficiently high hydrostatic fracture bead strength as the bead structure of the present invention, the bead strand is formed by winding one cord, and both ends of the winding start and winding end are wound. It is preferable that the bead innermost layer is not present.

In FIG. 1, it is preferable that the core material PBO fiber (1) is completely covered with the thermoplastic polyamide resin (2) and has a substantially circular cross section, but it is not necessarily circular. (1) and (2) are adhered, and at this time r ₂ /
The r ₁ ratio is preferably 5.5 / 10 to 8.5 / 10.

A bead structure having a structure as shown in FIGS. 2-a and 2-b, in which a plurality of the cords are arranged in parallel and subjected to rubber insulation to form a bead having a rectangular cross section in which a plurality of layers are wound and laminated. However, in this case, as shown in FIG. 2-b, the overlapping portion comes to the innermost layer of the bead. It is preferable that the overlapping portion does not exist in the innermost layer in order to obtain sufficiently high hydrostatic fracture resistance as described above. .

As a more preferable strand structure for this purpose, rubber insulation is applied with one cord of FIG. 1, and when this cord is considered as a strand bead structure of 4 rows × 4 rows as shown in FIG. 4, (1 ) To (16) in order to form a bead with a rectangular cross section. There is one (1) and one (16) overlapping part of the cord, and there is no overlapping part in the (4), (5), (12) and (13) parts that are closest to the bead base part. Can be Even when (1) shown in FIG. 3 reaches the innermost layer, good results are obtained as the bead wire of the present invention, but in the case of the bead structure of FIG. 4, the weight imbalance is further alleviated and the bead wire is reduced. Shear stress concentration at the edges is reduced and the hydraulic fracture level is further improved. FIG. 5 is a cross-sectional view corresponding to Comparative Example 3 in which the width of the bead is adjusted to the embodiment by increasing the cord diameter of the bead wire and a 6 × 3 structure is formed in order to secure equal or higher total bead strength. FIG. 6A is a cross-sectional view of a bead wire having a resin-coated fiber cord having a bead structure of 3 rows × 4 rows, and FIG. It is explanatory drawing of the overlap part at the time of shape | molding to.

[0029]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Table 1 shows the lightweight bead wire type (fiber is PBO fiber and resin is changed), bead structure (strand bead step number × row number), fiber volume ratio in the wire, PBO fiber strength, and insulation rubber hardness. The results of measuring the tire hydraulic pressure breaking pressure (kg / cm ² ) and the bead expanding force for the changed Examples and Comparative Examples are shown below.

The hardness of the insulation rubber is J
It was measured by IS K6301. The tire hydraulic breaking pressure test is a test in which a tire is assembled on a rim, water is injected from a valve port, and the internal pressure of the tire when the tire is broken is taken as the hydraulic breaking pressure. The bead expansion force was obtained by expanding the rim divided into eight parts and measuring the force to tighten the rim applied to one piece at the time of the regular rim diameter (13 inches). Except for Examples 2 and 3, all four bead wires are arranged in parallel,
It is a square bead having a rubber coating and four-layer winding lamination. For the beads of Examples 2 and 3, 1 bead wire was used.
This is a single-strand structure with a rectangular cross section in which a rubber coating is applied with a book and the layers are wound and laminated in order from (1) to (16) in FIGS.

[0031]

[Table 1]

[0032]

[Table 2]

Comparing Examples 1 and 4 with Examples 2 and 3, hydraulic breaking pressure is improved in Example 2 having a single-strand bead structure having a small overlapping portion, and Example 3 (see FIG. 4). ) Improves. In Comparative Example 3, the cord diameter of the bead wire is increased, and in the case of the 4 × 4 structure, the tire bead portion is deformed, so that the rim assembly property, the rim fit property, and the like are deteriorated. When the width of the bead is adjusted to the embodiment and a structure of 6 × 3 is provided in order to ensure the bead strength equal to or higher than that of the bead, both the bead expanding force and the tire hydraulic breaking pressure decrease. The tires using the thermosetting resin bead wires of Comparative Examples 4 and 5 have a very low hydraulic breaking pressure because the material of the bead wires was damaged due to partial bending and large torsion in the tire rim assembly. It was easy and the strength was greatly reduced.

[0034]

EFFECTS OF THE INVENTION It is possible to significantly reduce the weight of a tire bead portion, and it is possible to improve fuel economy by reducing the weight of a tire. Even if the tire rim is assembled or unraveled abnormally, the tire bead is soft and twists easily so that the bead does not break (permanently deforms) and the bead expansion force that tightens the rim inward is sufficient. There is no slippage and no rim slippage. Since no hard steel wire is used for the bead wire, it can be cut with a cutter, and only ash remains when burned. In the indoor maneuverability test of the tire of the present invention, the cornering power (kgf / deg) is improved as compared with the tire using the current steel wire beads, and the maneuverability in an actual vehicle can be expected to be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of one fiber cord coated with a resin.

FIG. 2 a. It is sectional drawing of the bead wire which made the resin-coated fiber cord the bead structure of 4 steps x 4 rows. b. It is explanatory drawing of the overlap part at the time of arranging resin-coated fiber cords and making what was made into a band shape with insulation rubber into a ring shape.

FIG. 3 is a cross-sectional view of a bead wire having a rectangular cross section in which one bead wire is covered with rubber and is wound and laminated in an annular shape from (1) to (16) in order. Only (1) is the innermost layer overlap.

FIG. 4 is a sectional view of a bead wire obtained by forming a rubber-coated bead wire into an annular shape so that (1) and (16) in FIG. 3 do not become the innermost layer.

FIG. 5 is a comparative example 3 in which the bead width is increased to 6 × 3 according to the embodiment by increasing the cord diameter of the bead wire.
A cross-sectional view of a bead wire corresponding to.

FIG. 6 a. It is sectional drawing of the bead wire which made the resin-coated fiber cord the bead structure of 3 steps x 4 rows. b. It is explanatory drawing of the overlap part at the time of arranging resin-coated fiber cords and making what was made into a band shape with insulation rubber into a ring shape.

Claims (4)

[Claims] 1. The bead wire has a fiber strength T of 18 g /
A composite cord of a fiber composed of a heterocyclic ring-containing aromatic polymer of D or more and a polyamide resin, in which the thermoplastic polyamide resin completely covers a fiber composed of a heterocyclic ring-containing aromatic polymer as a core material. And a pneumatic radial tire using a lightweight bead having a fiber volume ratio in one bead wire of 30 to 70% and holding the resin-coated wire at intervals with an insulation rubber. 2. The pneumatic radial tire according to claim 1, wherein the thickness d of the resin layer covering the fiber layer composed of the heterocyclic ring-containing aromatic polymer which is the core material of the composite cord is 0.02 mm or more. . 3. A bead strand of a composite cord is formed by winding a composite cord made of a polyamide resin coated with a fiber composed of one heterocyclic ring-containing aromatic polymer, and at both ends of the winding start and the winding end. The pneumatic radial tire according to claim 1, wherein neither of them is in the innermost strand of the bead. 4. The pneumatic radial according to claim 1, wherein the fiber composed of a heterocycle-containing aromatic polymer is polyparaphenylenebenzobisoxazole fiber or polyparaphenylenebenzobisthiazole fiber. tire.