JP2000185508A - Pneumatic radial tire for passenger car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve control stability and riding comfort without sacrificing durability in adopting PEN cord to a carcass of a passenger car tire. SOLUTION: This pneumatic radial tire has as its framework, a carcass made of an organic fiber cord ply extending in a radial direction in a toroidal shape between a pair of bead cores. On top of the carcass, at least two layers of belts made of steel cord disposed diagonally with respect to equatorial plane of the tire are provided. The aspect ratio of this pneumatic radial tire is 65% or less, and double twisted polyethylene-2,6-naphthalate of 1000 to 10000 dtex is used as the organic fiber cord of the carcass.

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 for a passenger vehicle, and more particularly to a pneumatic radial tire for a passenger vehicle having improved steering stability and riding comfort without sacrificing durability.

[0002]

2. Description of the Related Art Vehicles mainly traveling on paved roads, especially passenger cars, have been improved year by year, have been used under good maintenance, and the road network has been further expanded. Tires to be used in passenger cars are required to have further improved running performance, especially steering stability. In addition, as the road surface is improved and the riding comfort performance of passenger cars is improving, the riding comfort when going over bumps, such as the passage of asphalt seams on bridges and highways, is also strongly improved. It has been demanded.

[0003] Here, in a pneumatic radial tire for a passenger car, it is customary to use a polyethylene terephthalate (PET) fiber cord as a reinforcing material constituting a carcass constituting the skeleton.

[0004]

However, the carcass using the PET cord cannot sufficiently respond to the demands for the steering stability and the riding comfort accompanying the improvement of the performance of the passenger car described above.

[0005] Incidentally, in order to improve the steering stability and riding comfort of the tire, it is advantageous to make the carcass tough, that is, to increase the elastic modulus of the reinforcing cord constituting the carcass. Therefore, it is conceivable to use a reinforcing cord constituting the carcass having a higher elastic modulus than the current PET cord, for example, a polyethylene naphthalate (hereinafter, referred to as PEN) fiber cord having a high elastic modulus among the same polyester. However, since the PEN cord has a higher modulus of elasticity than conventional PET cords and is inferior in fatigue resistance, when this PEN cord is used for a carcass of a tire, the durability of the tire may not be guaranteed. is there.

Accordingly, the present invention provides a method for improving steering stability and riding comfort without sacrificing durability when applying a PEN cord to a carcass of a passenger car tire. It is.

[0007]

Means for Solving the Problems In using the PEN cord for a carcass of a tire for a passenger car, the present inventors have made intensive studies on the fatigue resistance of the cord and the durability of the tire. The cord is hardly fatigued by tensile strain, but is fatigued by compressive strain. (A) The part that receives compressive strain in the carcass is that part of the carcass that is folded back outside the tire with a bead core. The distortion of the folded portion of the carcass becomes smaller as the bead portion becomes less bent when a load is applied to the tire. (D) A tire having a small aspect ratio has a higher rigidity and the above-mentioned bend becomes smaller, so that the carcass cord has The strain acting on the folded portion is small, and therefore, it is advantageous for the fatigue resistance of the carcass cord,
(E) Furthermore, it has been found that when the rigidity of the bead portion of the tire is increased, the deformation of the tire side portion is moderated, so that the strain applied to the carcass cord is reduced, and the present invention has been completed.

That is, the gist of the present invention is as follows. (1) At least two layers made of a steel cascade composed of a ply of organic fiber cords extending radially in a toroidal shape between a pair of bead cores and having a steel cord inclined on the equatorial plane of the tire on the carcass In a pneumatic radial tire having an aspect ratio of 65% or less, the organic fiber cord of the carcass is 1000 to
A pneumatic radial tire for a passenger car, comprising a twisted polyethylene-2,6-naphthalate of 10,000 dtex.

(2) In the above (1), the bead core has the following properties: 1.
A pneumatic radial tire for a passenger car, wherein a steel wire of 2 to 1.8 mm is spirally wound 7 to 30 times.

(3) The pneumatic radial tire for a passenger car according to the above (1) or (2), wherein the carcass comprises one or two layers.

[0011]

FIG. 1 illustrates a specific example of a radial tire for a passenger car according to the present invention. This tire is 1
A carcass 2 composed of at least one PEN cord ply extending in a toroidal shape in the radial direction between a pair of bead cores 1, a belt 3 having at least two layers disposed outside a crown portion of the carcass 2 in a tire radial direction, and the belt 3 comprises a tread 4 disposed radially outside the tire. In the illustrated example, a belt reinforcing layer 5 formed by winding an organic fiber cord in the circumferential direction is arranged between the belt 3 and the tread 4 over the entire width of the belt 3.

The carcass 2 is made of PE extending in the radial direction.
One of the plies formed by driving N code at 30-70 / 50mm
One or two sheets are stretched between the bead cores 1 in a toroidal shape, and both ends are folded back to the outside of the tire by the bead cores 1. And, as the PEN code, the fineness is 10
It is important to use a twin-twisted cord having a size of 100 to 10,000 dtex. That is, the fineness of the PEN cord is 1000 dte
If it is less than x, the carcass must have three or more layers in order to maintain a predetermined strength in the tire, and as a result, the production cost of the tire increases. On the other hand, fineness is 10,000 d
Exceeding tex is undesirable because the cord becomes thicker and the carcass thickness increases, resulting in an increase in tire weight.

The reason why the PEN cord is twin-twisted is as follows.
This is because the workability during production is kept good, and a decrease in cord elastic modulus is suppressed. That is, in contrast to twin-twisting, single-twisting leaves a twist in the filament, so that a treating material in which a cord is covered with rubber is easily rounded, and workability is deteriorated. For the same reason, a decrease in cord elastic modulus cannot be avoided.

Here, in the present invention, PEN, which is a material of the cord, may contain at least 90 mol% of an ethylene-2,6-naphthalate unit, and may contain an appropriate third component in a proportion of less than 10 mol%. It may be a polymer containing. Generally, polyethylene 2,6-naphthalate is synthesized by subjecting naphthalene-2,6-dicarboxylic acid or an ester-forming derivative thereof to polycondensation with ethylene glycol under appropriate reaction conditions in the presence of a catalyst. At this time, if one or more appropriate third components are added before the completion of the polymerization of polyethylene 2,6-naphthalate, a copolymerized polyester is synthesized.

Suitable third components include (a) compounds having two ester-forming functional groups; for example, oxalic acid,
Aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and dimer acid; alicyclic dicarboxylic acids such as diclopropanedicarboxylic acid, cyclobutanedicarboxylic acid and hexahydroterephthalic acid; phthalic acid, isophthalic acid, naphthalene-2,7 Aromatic dicarboxylic acids such as dicarboxylic acid and diphenyl dicarboxylic acid; carboxylic acids such as diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, sodium 3,5-dicarboxybenzene sulfonate, glycolic acid, p-oxy Oxycarboxylic acids such as benzoic acid and p-oxyethoxybenzoic acid, propylene glycol, trimethylene glycol, diethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentylene glycol , P- xylylene glycol, 1,
4-cyclohexanedimethanol, bisphenol A,
p, p'-dihydroxydiphenyl sulfone, 1,4-
Bis (β-hydroxyethoxy) benzene, 2,2-bis (p-β-hydroxyethoxyphenyl) propane,
Oxy compounds such as polyalkylene glycols; functional derivatives thereof; the carboxylic acids, oxycarboxylic acids,
Highly polymerizable compounds derived from oxy compounds or their functional derivatives, and (b) compounds having one ester-forming functional group, such as benzoic acid, benzyloxybenzoic acid, and methoxypolyalkylene glycol. .

Further, (c) a compound having three or more ester-forming functional groups, for example, glycerin, pentaerythritol, trimethylolpropane and the like can be used in a range where the polymer is substantially linear. .

It goes without saying that the polyester may contain a matting agent such as titanium dioxide and a stabilizer such as phosphoric acid, phosphorous acid and esters thereof.

In applying the PEN cord to the carcass as described above, it is important that the aspect ratio of the tire be 65% or less. This is because tires with an aspect ratio of 65% or less have high rigidity and little deflection of the tire side when supporting the load of a passenger car, so that the compressive strain applied to the carcass cord is reduced, and as a result, the fatigue resistance of the cord is reduced. It is because it will increase. Tire aspect ratio is 65%
Exceeding the limit may cause a large deflection of the tire side portion when a load is applied, and the fatigue with the PEN cord may exceed an allowable value.

As described above, by limiting the aspect ratio of the target tire, it becomes possible for the first time to apply the PEN code to the carcass without impairing the tire durability. You can enjoy the effect. That is, when the PEN cord is applied to the carcass, since the PEN has high elasticity, the rigidity of the tire as a whole is improved, and the steering stability is improved. In addition, the rigidity of the tire as a whole is improved, so that the rubber of the tread pattern portion, the side portion and the tread portion is softened, or the entire tire is softened, so that there is room for improving the ride comfort. As a result, the steering stability and ride comfort of the tire can be improved in a well-balanced manner.

Next, the belt 3 has a laminated structure of the first belt layer 3a and the second belt layer 3b in order from the carcass 2 side in the illustrated example, and is preferably inclined with respect to the ply cord of the carcass 2, preferably. It has a structure in which a plurality of rubber coating layers made of a large number of steel cords arranged at an inclination angle of 22 to 30 ° are overlapped in an arrangement where the steel cords intersect each other between the layers.

Further, the bead core 1 is formed by winding one steel wire having a diameter of 1.2 mm or more continuously seven times or more in a spiral shape, and has a structure as shown in FIGS. This is advantageous for alleviating sudden deformation of the tire side portion. That is, if the diameter of the steel wire constituting the bead core 1 is less than 1.2 mm or the number of turns is 6 or less as shown in FIG. 6, sufficient bead portion rigidity cannot be obtained, and rapid deformation of the tire side portion occurs. Is difficult to mitigate. However, if the diameter exceeds 1.8 mm or the number of turns
If the number of times exceeds 30, the rigidity of the bead portion becomes too high, and it becomes difficult to attach or detach the tire to or from the rim. Therefore, a bead core was formed by winding a steel wire having a diameter of 1.2 to 1.8 mm 7 to 30 times.

[0022]

EXAMPLES A bead core 1 and a carcass 2 of a radial tire for a passenger car having the structure shown in FIG. 1 were manufactured under the specifications shown in Tables 1 and 2, and tires of various sizes were prototyped. The organic fiber cord applied to the carcass is 16
It is 70 dtex / 2 and consists of 50 cords / 50 mm. The belt 3 is composed of a first belt layer 3a in which 1 × 5 × 0.25 (mm) steel cords are arranged in a direction of being inclined at an angle of 20 ° to the left with respect to the equatorial plane of the tire at a number of 40/50 mm. And a second belt layer 3b on which the steel cord is arranged at the same number of shots in a direction inclined at a right angle of 20 ° with respect to the equatorial plane of the tire. In addition, there is a nylon 1400 dtex /
The belt reinforcing layer 5 in which the cords of No. 2 were arranged at 50 cords / 50 mm was provided.

Each of the tires thus obtained was incorporated into its standard rim, adjusted to an air pressure corresponding to the maximum load capacity, and then mounted on a 2000 cc class passenger car.
The test course was run at a speed of 200 km / h, and the feeling of driving stability and ride comfort was evaluated by two drivers.

The steering stability was evaluated by two drivers for items such as straight running stability, turning stability, rigidity, and handling, and the scores of all items and two drivers were averaged. Similarly, ride comfort was evaluated by two drivers for items such as vibration characteristics at joint roads and running on cobblestone roads, and the scores of all items and two drivers were averaged.

In this evaluation, based on the results of Comparative Example 1, the performance difference with respect to the tire of Comparative Example 1 was indicated as follows. That is, ± 0 indicates that the test driver cannot detect a performance difference in comparison with the tire of Comparative Example 1, +1 indicates that the test driver has a performance that can significantly detect a performance difference in comparison with the tire of Comparative Example 1, and +2 indicates When the test driver has a performance that can clearly detect the performance difference with the tire of Comparative Example 1, +3 indicates that the general driver has a performance that can significantly detect the performance difference with the tire of Comparative Example 1. , +4 indicates that a general driver can detect a performance difference clearly in comparison with the tire of Comparative Example 1, and +5 indicates that a general driver can detect a performance difference very clearly in comparison with the tire of Comparative Example 1. In the case of having the performance, On the other hand, -1 to-
An evaluation of 5 indicates a case where the performance is inferior at the same stage as the above-mentioned evaluation on the + side.

Further, the durability of the tire was measured by applying 150% of the specified load of JATMA at an internal pressure of 2.0 kgf / cm ² to the tire subjected to the above test, on a steel drum (diameter: 3 m) having a smooth surface. In the test, the vehicle was run at 50 km / h and the time until the occurrence of a failure was measured to evaluate. The measurement results were indicated by an index when the running time of Comparative Example 1 was set to 100. Tables 1 and 2 show the above evaluation results and measurement results.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

According to the present invention, even when the PEN cord is applied to the carcass, sufficient durability is ensured for the tire. Therefore, by applying the PEN cord, the durability is not sacrificed. In addition, improved steering stability and ride comfort can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a tire structure of the present invention.

FIG. 2 shows a bead core according to the present invention.

FIG. 3 is a view showing a bead core according to the present invention.

FIG. 4 is a diagram showing a bead core according to the present invention.

FIG. 5 shows a bead core according to the present invention.

FIG. 6 is a view showing another bead core;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Belt 3a 1st belt layer 3b 1st belt layer 4 Tread 5 Belt reinforcement layer

Claims (3)

[Claims] 1. A carcass comprising a ply of organic fiber cords extending radially in a toroidal manner between a pair of bead cores as a skeleton, on which at least a steel cord inclined with respect to the equatorial plane of a tire is provided. In a pneumatic radial tire having a two-layer belt and an aspect ratio of 65% or less, the organic fiber cord of the carcass has a twist of 1,000 to 10,000 dtex and a twist of polyethylene-2,2.
A pneumatic radial tire for a passenger car, comprising 6-naphthalate. 2. The method according to claim 1, wherein the bead core has a diameter of 1.2.
A pneumatic radial tire for a passenger car, which is formed by spirally winding a steel wire having a diameter of ~ 1.8 mm 7 to 30 times. 3. The pneumatic radial tire for a passenger car according to claim 1, wherein the carcass comprises one or two layers.