JPH0930210A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lighten weight and raise operational stability and high speed durability by keeping the steel angle of a belt layer within a specific range, making a fiber cord of a belt reinforcement layer of a specific composition, having the fiber cord made by all-denier double twist within a specific range, and having the twist coefficient and a ratio of the number of a primary twist versus a final twist within a specific range. SOLUTION: A steel angle of a belt layer is 40 to 70 deg. from the tire 10 circumferential direction and a fiber cord of a belt reinforcement layer 22 is made of a polyethylene terephthalate fiber cord or a polyethylene-2,6-naphthalate fiber cord. The fiber cord is an all-denier 1000 to 6000 double twist, while a twist coefficient represented by NT=T×(0.139×D×1/ρ)<1/2> ×10<-3> is 0.1 to 0.5 and the ratio TR of the number of a primary twist versus a final twist represented by TR=PT/CT is 1.5 to 2.5. T represents the number of twists (the number of twist/10cm), D represents all-denier, ρ represents the specific gravity, PT represents the number of primary twists and CT represents the number of final twists. Thus cord modulus is raised by low twist.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention improves lightness and
The present invention relates to a pneumatic radial tire that enhances steering stability and has excellent high-speed durability.

[0002]

2. Description of the Related Art As vehicles become higher in quality and higher in quality, there is an increasing demand for improvements in tire lightweight, steering stability, high speed durability and the like.

At present, two or more angled steel belts are mainly used for the belt layer of the radial tire, while a twin-twisted organic fiber cord such as nylon is mainly used for the belt reinforcing layer, and its twist coefficient is Attempts have been made to increase the cord modulus with a low twist to improve the steering stability and high-speed durability of tires.

However, with such a belt layer structure, in order to improve high-speed durability, for example, two belt layers and one belt reinforcing layer constitute a total of three layers, and an increase in weight is inevitable. . In addition, when a nylon fiber cord is used for the belt reinforcing layer and the modulus is increased, the adhesion between the cord and the coating rubber is reduced, so that the improvement in high-speed durability, which is equivalent to the improvement in tire rigidity, cannot be seen. For weight reduction, if one angled steel belt is used, conventional nylon fiber cord is used for the belt reinforcing layer, and even if the modulus is increased by ignoring the adhesion, the rigidity is insufficient in the first place. Stability is compromised.

[0005]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a pneumatic radial tire having improved lightness, improved steering stability and excellent high-speed durability.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have made diligent studies by paying attention to the belt layer structure, the material, the shape, the physical properties of the fiber cord used in the belt reinforcing layer, the twisting method of the fibers, and the like. As a result, they have found that the above-mentioned required characteristics can be satisfied at the same time by the following means, and have completed the present invention. (1) The pneumatic radial tire of the present invention includes a pair of beat portions, a toroidal carcass extending over both beat portions, a tret portion located at the crown portion of the carcass, and a sidewall portion of the carcass. And a belt reinforcing layer made of at least one sheet on the outer peripheral side of the one angled steel cord belt layer arranged inside the tread portion, the belt reinforcing layer being provided on at least the entire tread portion. Is a pneumatic radial tire formed by winding a narrow rubberized strip containing a plurality of fiber cords in a spiral shape so that the cords are substantially parallel to the tire circumferential direction, The steel cord angle of the belt layer is 40 to 70 degrees, and the fiber cord of the belt reinforcing layer is polyethylene terephthalate fiber. Code or polyethylene-2,6
A naphthalate fiber cord, which is a double twist of total denier of 1000 to 6000, has a twist coefficient NT represented by the following general formula (1) of 0.1 to 0.5, and the following general formula ( The ratio TR of the number of lower twists to the number of upper twists represented by 2) is 1.5 to 2.5.

[0007]

(Equation 3)

[In the formula, NT is a twist coefficient, T is the number of twists (times / 1
0 cm), D represents total denier, and ρ represents specific gravity. ]

[0009]

(Equation 4)

[Where TR is the ratio of the number of lower twists to the number of upper twists, PT
Is the number of lower twists (times / 10 cm), CT is the number of upper twists (times / 10 c)
m) respectively. (2) The pneumatic radial tire of the present invention is characterized in that, in the item (1), the steel cord angle is 50 to 60 degrees. (3) In the pneumatic radial tire of the present invention, in the above (1), the fiber cord has a total denier of 2000 to 45.
It is a double twist of 00. (4) The pneumatic radial tire of the present invention is characterized in that, in the item (1), the twist coefficient NT is 0.15 to 0.35. (5) In the pneumatic radial tire of the present invention, the ratio TR of the number of lower twists to the number of upper twists is 1.7 to 2.
It is characterized by being 2.

The fiber cord used in the present invention has a relatively high modulus, is easy to satisfy the above-mentioned various characteristics, and is excellent in the required performance of the tire. Further, from the economical point of view, a polyethylene terephthalate fiber cord, It is necessary to use polyethylene-2,6-naphthalate fiber cord. In particular, polyethylene terephthalate fiber cord is preferable.

In the pneumatic radial tire of the present invention, a belt reinforcing layer is provided on at least the entire tread portion on the outer peripheral side of a single 40 to 60 degree angled steel cord belt layer, and the belt reinforcing layer comprises a plurality of fiber cords. The rubber-containing narrow strip of rubber is endlessly wound in a spiral shape so that the cord is substantially parallel to the tire circumferential direction, and the belt reinforcing layer is made of polyethylene terephthalate or polyethylene-2,6-naphthalate fiber cord. This fiber cord is made up of total denier 1000-6
000 double twists, the twist coefficient is 0.1 to 0.5, and the ratio of the number of lower twists to the number of upper twists is 1.5 to 2.5. In this way, by using one steel belt layer, it is possible to reduce the weight, and the belt reinforcing layer is spirally wound around the entire tread portion, and as the cord used for this reinforcing layer, a high modulus polyester fiber cord is used. By setting the twist coefficient of the upper twist so that the cord modulus is the largest and arranging a barrier-like reinforcing layer with high tension in the tire circumferential direction, the steering stability and high-speed durability of the tire are at a high level. By maintaining and further improving the adhesion between the cord and the rubber by optimizing the twist number, the high speed durability of the tire can be further improved.

If the belt reinforcing layer does not have a spiral winding structure as described above, a joint can be formed in the tire circumferential direction, so that the tension in the circumferential direction is improved rather than the tension in the circumferential direction. There is a gap between the lower layers, and even if the above code characteristics are limited, no effect can be seen.

In the present invention, the steel cord angle of the belt layer is 40 to 70 degrees, preferably 50 to 60 degrees. This gives a high level of steering stability. If the angle is less than 40 degrees or more than 70 degrees, it is not preferable in terms of steering stability.

In the present invention, the fiber cord of the belt reinforcing layer has a total denier of 1000 to 6000, preferably 2000 to denier.
It has a 4500 double twist structure. If it is less than 1000 denier, it is not preferable in terms of handling stability, and if it exceeds 6000 denier, it is not preferable in terms of weight increase.

In the present invention, the fiber cord of the belt reinforcing layer has a twist coefficient of 0.1 to 0.5, preferably 0.15 to 0.3.
5 is assumed. In this way, the low twist and the high modulus of the cord can maintain the steering stability and high-speed durability of the tire at a high level. If the twisting coefficient exceeds 0.5, the modulus of the cord decreases, which is not preferable. On the other hand, if it is less than 0.1, the tire manufacturing workability is deteriorated, which is not suitable for mass production.

In the present invention, the fiber cord of the belt reinforcing layer has a ratio of the number of lower twists to the number of upper twists of 1.5 to 2.5, preferably 1.7 to 2.2. As a result, even with a low-twisted fiber cord, the adhesion between the cord and rubber can be made to a sufficient level, and the high speed durability of the tire is further improved. If this ratio is less than 1.5, the adhesiveness will be poor, such being undesirable. Further, if this ratio exceeds 2.5, the number of twists increases, resulting in an increase in cost, a significant decrease in cord modulus, and poor steering stability of the tire.

As described above, the steel cord angle of one belt layer is set to the optimum angle, the polyester fiber cord is used for the belt reinforcing layer, and the cord is set to the optimum denier, the optimum twist coefficient, and the optimum number of lower twists. By setting the ratio of the number of twists, it is possible to satisfy lightness, steering stability, and high-speed durability at a high level at the same time.

[0019]

1 to 5 are sectional views of a pneumatic radial tire of an embodiment of the present invention, and FIG. 6 is a sectional view of a pneumatic radial tire of a comparative example.

1 to 6, a pneumatic radial tire 10 includes a carcass 14 which is folded around the bead core 12 from the inside of the tire to the outside and is locked, and the carcass 14
Tread portion 16 located in the crown portion of the carcass 1
4 side wall portions 18, one belt layer 20 (two layers only in FIG. 6) arranged inside the tread portion 16, and at least one sheet on at least the entire tread portion on the outer peripheral side of the belt layer 20. And a belt reinforcing layer 22. The belt reinforcing layer 22 is a narrow rubberized strip containing a plurality of fiber cords, the cords being substantially parallel to the tire circumferential direction (0 ° to 5 °). ) Is endlessly wound in a spiral shape (spiral shape). Although the belt reinforcing layer 22 protrudes outward in the axial direction of the belt layer 20, it does not have to protrude. The carcass 14 has fiber cords arranged in a direction substantially perpendicular to the circumferential direction, and is composed of at least one layer. In the belt layer 20, steel cords are arranged at an inclination angle of 40 ° to 70 ° with respect to the circumferential direction (or the equatorial plane of the tire). In FIG. 6, two cords are stacked so that the cords intersect in different directions. ing.

1 to 6 show examples of the arrangement of the belt reinforcing layer 22. FIG. 1 is a cross-sectional view of a tire in which the belt reinforcing layer 22 is evenly wound around the entire tread portion 16 from the cereal side to the anti-cerial side on the outer peripheral side of the belt layer 20. FIG. 2 is a cross-sectional view of a tire in which one belt reinforcing layer 22 is wound around the entire tread portion 16 and one belt reinforcing layer 22 is further wound around both ends on the outer peripheral side thereof. FIG. 3 is a cross-sectional view of a tire in which one belt reinforcing layer 22 is wound around the entire tread portion 16 and one belt reinforcing layer 22 is further wound around the center of the tread portion 16 on the outer peripheral side thereof. FIG. 4 shows the belt reinforcing layer 2 on the entire tread portion 16.
2 is a cross-sectional view of a tire in which one layer of 2 is wound and two belt reinforcing layers 22 are further wound around both ends on the outer peripheral side.
FIG. 5 is a cross-sectional view of a tire in which two belt reinforcing layers 22 are wound around the entire tread portion 16 and one layer is wound around both ends. Comparative Example FIG. 6 is a cross-sectional view of a tire in which the belt reinforcing layer 22 is wound around the entire tread portion 16 on the outer peripheral side of the two-layer belt layer 20.

(1) Examples 1-4 and Comparative Examples 1-to be described later
The tires used in No. 6 are as follows. The tire size used is a tubeless structure of 205 / 65R15, and the tire is manufactured under vulcanization conditions of 170 ° C for 13 minutes and post cure inflation conditions of an internal pressure of 2.5 kg / cm.
^{It took 2} to 26 minutes.

The carcass has a number of twists of 1500 D / 2 (twist of 1500 denier) (bottom twist × top twist) 40 × 40
(One time / 10 cm) Polyethylene terephthalate cord is used for one sheet, the number of implants is 55.0 lines / 5 cm
I used one.

As the belt layer, one steel cord belt having a structure of 1 × 5 × 0.23 (two sheets in Comparative Example 4) is arranged, and the driving angle is a predetermined angle with respect to the circumferential direction (in Comparative Example 4, The right and left sides were 68 °, and the number of driving was 40.0 lines / 5 cm.

The belt reinforcing layer is 0 to 5 ° with respect to the circumferential direction.
It was spirally wound around the outside of the belt layer. The belt reinforcing layer was arranged as shown in FIG. 1 (Comparative Example 4 is FIG. 6). On this occasion,
The belt reinforcing layer was wound around the entire tread portion by 5 mm wide at both axially outer ends of the belt layer. Further, the reinforcing layer was formed on the belt layer by the above method using a strip having a narrow width of about 5 to 20 mm.

The polyethylene terephthalate fiber cord used in the belt reinforcing layer is obtained as follows.

The polyethylene terephthalate polymer was obtained as follows. Charge 2 moles of terephthalic acid, 3 moles of ethylene glycol, and antimony trioxide (2 × 10 ⁻⁴ moles with respect to terephthalic acid) as a catalyst into a reaction vessel equipped with a stirrer and replace with nitrogen gas sufficiently. The pressure was increased to 1.8 kg / cm ² with nitrogen gas and the reaction was carried out at 240 ° C. After removing almost theoretical amount of water and by-products to the outside of the system, 15 mmHg at 40 mmHg and 255 ° C. for 60 minutes
The polycondensation reaction was carried out at 270 ° C. for 60 minutes at 1 mmHg / 275 ° C. until a predetermined molecular weight was reached, and immediately after the reaction was finished, it was cooled in ice water. After completion of the polycondensation reaction, the sample rapidly cooled in ice water was cut into 2 mm to 3 mm pellets and
g into a 100 ml round bottom flask and decompressed (0.1
mmHg) Put the round bottom flask in the oil bath and
Crystallization and preliminary drying were carried out for 2 hours at a stirring speed of 30 rpm in ° C. Then, solid phase polymerization was carried out at a temperature (melting point-18 ° C) of each sample at a stirring speed of 30 rpm for a predetermined time. The solid phase polymerization time is, when the polymer intrinsic viscosity at the start of polymerization = 0.60 (weight average molecular weight = 5.5 × 10 ⁴ ) is used, the intrinsic viscosity at 237 ° C. is 0.98 (weight average molecular weight). (= 7.5 × 10 ⁴ level), it took about 7 hours.

The solid-phase-polymerized polyethylene terephthalate (intrinsic viscosity 0.98) obtained was 10 to 60 ° under a spinneret.
Quenching in a gas atmosphere of C (for example, 25 ° C), spinning speed 1500-6000 m / min (for example, 4200 m / min)
Spinning and winding, then draw ratio 1.2-2.30
(For example, 1.31) was drawn to prepare a polyethylene terephthalate raw yarn.

This raw yarn was adjusted to have a predetermined total denier, twist coefficient, and ratio of the number of lower twists to the number of upper twists to obtain a twisted yarn cord. The twisted cord was applied with an adhesive and heat-treated under the following conditions.

For the adhesive, resorcin-polysulfide and resorcin-rich resorcin-formaldehyde condensate were mixed at a solid content ratio of 20: 100, and 18 parts of the solid content were taken out from the mixture, to which 9 parts of 28% ammonia water was added. Further, water was added so that the whole amount became 50 parts and completely dissolved, and then 50 parts of resorcin-formaldehyde condensate / latex (RFL) was added.
Here, RFL is prepared by adjusting the following composition and aging for 48 hours or more. -Water 518.8 (parts by weight) -Resorcin 11.0-Formalin (37%) 16.2-Ammonium hydroxide (28%) 10.0-Vinylpyridine-styrene-butadiene 244.0 copolymer latex ( 41%) First, the twisted yarn cord is dipped in this adhesive, the treatment temperature in the drying zone is 170 ° C., the treatment time is 60 to 160 seconds, and the treatment temperature in the heat setting zone and the normalizing zone is 250 to 265 ° C. Processing time from 60
For 170 seconds, the heat setting zone cord tension is set to 0.4 to 1.1 g / d and the normalizing zone cord tension is set to 0.03 to 0.50 g / d. After that, the treatment temperature is set in the annealing zone. 150-180
C, treatment time 30-170 seconds, cord tension 0.01
By setting in the range of 0.70 g / d, a predetermined adhesion treatment code can be obtained.

(2) Examples 1 to 4 and Comparative Examples 1 to 1 described below
The various test methods used in 6 are as follows. - steering stability test 205 / 65R15, pressure 2.0 kgf / cm ^2, 4-wheel the test tires having a rim size of 6J-15 to 2000cc displacement volume sedan type automobile mounted, and traveling in steering stability evaluation test course.

Each test tire was mounted on a passenger car,
Conducting an actual vehicle feeling test at a speed of 00 km / hour, and assigning a score of 1 to 10 for items such as (i) straight running stability, (ii) turning stability, (iii) feeling of rigidity, and (iv) handling , Each item was averaged and used as a rating of steering stability. The evaluation was performed by two professional drivers, and the average of the scores of the two drivers was calculated, and the control tire of Comparative Example 1 was shown as an index with a point of 0. 10 points is good, 1 is bad, and a difference of 3 points or more is a clear difference.・ High-speed durability test The high-speed durability of tires is evaluated by the US standard FMVSS No.
According to the test method of No. 109, the step speed method was performed, that is, the speed was increased every 30 minutes until a failure occurred, and the speed at the time of failure was shown as an index with the control tire of Comparative Example 1 being 100. The higher the index, the better the high speed durability.・ Lightness of tire It is expressed by the weight of the tire. [Example 1] The steel cord used for the belt layer is 1
The number of sheets is 60, and the angle is 60 degrees.

Polyethylene terephthalate fiber cord (PET) used as the belt reinforcing layer fiber cord is 2
Twisted 4 times / 10 cm, twisted two yarns in the opposite direction and twisted 12 times / 10 cm in the opposite direction to give a total denier of 30
00, the ratio of the number of lower twists to the number of upper twists is 2.0, and the twist coefficient is 0.2.

A pneumatic radial tire having such a belt layer structure and a fiber cord of the belt reinforcing layer,
Table 1 shows the results of evaluating various characteristics of the tire such as lightness, steering stability, and high-speed durability. [Examples 2 to 4] As compared with Example 1, as shown in Table 1, the components of the belt layer structure and polyethylene terephthalate fiber cord (total denier, ratio of number of lower twists to number of upper twists, twist coefficient) The numerical values are changed within the scope of claims, and Examples 2 to 4 are used.
And Regarding the tire obtained in the same manner as in Example 1,
The results of evaluation of various properties are shown in Table 1. [Comparative Examples 1 to 6] As shown in Table 1 with respect to Examples,
At least one of the elements of the belt layer structure and the polyethylene terephthalate fiber cord was out of the scope of the claims, and the numerical values were changed to make Comparative Examples 1 to 3 and 5 to 6. Moreover, it was set as Comparative Example 4 using a nylon fiber cord. Table 1 shows the results of evaluation of various characteristics of the tire obtained in the same manner as in Example 1.

[0035]

[Table 1]

As shown in Table 1, it can be seen that the pneumatic radial tire of the present invention has a well-balanced balance of tire lightweight, steering stability, and high-speed durability.

As shown in the comparative example, at least one of the number of steel cords in the belt layer, the angle thereof, the total denier of the belt reinforcing layer fiber cords, the twist coefficient, and the ratio of the number of lower twists to the number of upper twists.
It can be seen that in the radial tire which is outside the scope of the claims, any one of the tire 3 characteristics is insufficient as compared with the examples.

[0038]

Since the pneumatic radial tire of the present invention has the above-mentioned structure, it has the excellent effects of improving the lightweight of the tire, enhancing the steering stability, and improving the high-speed durability.

[Brief description of drawings]

FIG. 1 is a sectional view showing one embodiment of a pneumatic radial tire of the present invention.

FIG. 2 is a sectional view showing another embodiment of the pneumatic radial tire of the present invention.

FIG. 3 is a sectional view showing another embodiment of the pneumatic radial tire of the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of the pneumatic radial tire of the present invention.

FIG. 5 is a cross-sectional view showing another embodiment of the pneumatic radial tire of the present invention.

FIG. 6 is a cross-sectional view showing a comparative example of a pneumatic radial tire.

[Explanation of symbols]

 10 Pneumatic radial tire 12 Bead core 14 Carcass 16 Tread portion 18 Side wall portion 20 Belt layer 22 Belt reinforcement layer

Claims (5)

[Claims] 1. A pair of beat parts, a toroidal carcass extending over both beat parts, a tret part located at a crown part of the carcass, and a side wall part of the carcass, and A belt reinforcing layer consisting of at least one sheet is provided on at least the entire tread portion on the outer peripheral side of the angled steel cord belt layer arranged inside the tread portion, and the belt reinforcing layer includes a plurality of fiber cords. A pneumatic radial tire formed by winding a rubberized narrow strip in a spiral shape so that the cord is substantially parallel to the tire circumferential direction, wherein the steel cord angle of the belt layer is The angle is 40 to 70 degrees from the tire circumferential direction, and the fiber cord of the belt reinforcing layer is polyethylene terephthalate fiber cord or Consists of polyethylene-2,6-naphthalate fiber cord, the fiber cord is a plied total denier 1000 to 6000, the twist coefficient NT represented by the following general formula (1) from 0.1 to 0.
5 and a ratio TR of the number of lower twists to the number of upper twists represented by the following general formula (2) is 1.5 to 2.5. [Equation 1] [In the formula, NT is a twist coefficient, T is the number of twists (turns / 10 cm), D
Represents total denier and ρ represents specific gravity. ] [Equation 2] [In the formula, TR represents the ratio of the number of lower twists to the number of upper twists, PT represents the number of lower twists (times / 10 cm), and CT represents the number of upper twists (times / 10 cm). ] 2. The pneumatic radial tire according to claim 1, wherein the steel cord angle is 50 to 60 degrees. 3. The fiber cord has a total denier of 2000-
The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire has a twist of 4,500. 4. The pneumatic radial tire according to claim 1, wherein the twist coefficient NT is 0.15 to 0.35. 5. The ratio TR of the number of lower twists to the number of upper twists is 1.7 to
The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is 2.2.