JPH08175105A - Pneumatic radial tire for automobile - Google Patents

Abstract

PURPOSE: To improve the stability and controllability of a tire where one layer of the ply is not coiled back at the bead core by specifying the relationship of the tensile elasticity per unit width of a first ply of a carcass to be coiled back at the bead core and a second ply along the outer side of a fold-back part. CONSTITUTION: A carcass 4 extends over the ply of the cord of the radial orientation across the bead cores 6 in the troydal shape, and a first ply 8 having a fold-back part 10 which folds back outwardly and extends from the inner side in the axial direction of the tire around the bead core 6 is provided. A second ply 9 is provided toward a bead heel 7 of the bead part 2 along the outer side in the axial direction of the tire of the fold-back part 10. The inequality of E2/E1 >=1.05 is satisfied where E1 and E2 are the tensile elasticity per unit width of the first and second plies 8, 9 respectively. The carcass structure whose stability and controllability of the tire is improved and the durability is satisfied is obtained.

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, and more particularly to a carcass structure for improving steering stability of a pneumatic radial tire for passenger cars.

[0002]

2. Description of the Related Art A radial tire for a passenger vehicle having a carcass composed of two or more layers of plies generally comprises a radial array ply of rubber-coated organic fiber cords straddling in a toroidal shape between a pair of bead cores. A structure I (see FIG. 1) is generally provided in which each of the plies has a folded portion of the plurality of plies that extends from the inside of the tire to the outside around each bead core.

[0003]

Even in the same tire having a carcass structure having a plurality of plies, at least one layer of the plurality of plies is not folded back around the bead core as compared with the tire having the structure I, and the ply is located outside in the tire axial direction. The carcass structure II (see FIG. 2, FIG. 3, or FIG. 4) arranged as a second ply extending toward the bead along the side uses less ply material, but on the other hand, folds around the bead core. The ply which is not applied has a low ply tension, and thus such a tire has a problem that steering stability is deteriorated. Therefore, the problem to be solved by the present invention is to provide a structure II in which at least one ply of a plurality of plies is not wound around the bead core.
To provide a carcass structure that improves the steering stability of the tire.

[0004]

When a plurality of plies are applied to a radial tire for a passenger car, it is common to use the same cord and rubber composite for each of the plurality of plies. Further, in the case of the tire having the structure II, at least one ply is not folded back around the bead core, so that the tensile load on that portion is reduced, which leads to a reduction in tire rigidity and a reduction in steering stability. As a result of diligent research to improve such a phenomenon, as compared with a ply folded around a bead core, by increasing the tensile elastic modulus E2 per unit width of the ply that is not folded, a passenger car such as a carcass structure II is obtained. The present invention has been accomplished by discovering that even a radial tire for a vehicle can improve the steerability of the tire.

In order to improve not only the steering stability of the tire but also the durability of the tire, E
We have also found that 2 / E1 needs to be in a certain range and have reached the present invention.

That is, the pneumatic radial tire for passenger cars according to the first aspect of the invention is a carcass comprising at least one layer of plies of a radial arrangement cord extending in a toroidal shape between a pair of bead portions, and a non-carcass arranged in the crown portion of the carcass. The carcass has a belt layer made of an extensible cord, and the carcass has at least one first layer having a folded portion of the ply which is wound around the bead core embedded in each bead portion and extends from the inner side toward the outer side in the axial direction of the tire. In a pneumatic radial tire for passenger cars consisting of a ply and at least one second ply extending toward the bead portion along the tire axial direction outer side of the folded portion, the tensile elastic modulus per unit width of the first ply is When E1 and the tensile elastic modulus per unit width of the second ply is E2, E2 / E1 ≧ It is characterized in that it is .05.

The pneumatic radial tire for passenger cars according to claim 2 is the pneumatic radial tire for passenger cars according to claim 1, wherein the relationship between E1 and E2 is 3.00 ≧ E.
The feature is that 2 / E1 ≥1.05.

A pneumatic radial tire for a passenger vehicle according to a third aspect is the pneumatic radial tire for a passenger vehicle according to the first or second aspect, wherein the number of cords per unit width of the first ply is N1 and the second radial When N2 is the number of cords to be driven per unit width of ply, N
The feature is that 2 / N1> 1.

A pneumatic radial tire for a passenger vehicle according to a fourth aspect is the pneumatic radial tire for a passenger vehicle according to the first or second aspect, wherein the twist coefficient of the cord of the first ply is R1 and that of the second ply. When the twist coefficient of the cord is R2, it is characterized that R1 / R2> 1.

A pneumatic radial tire for a passenger vehicle according to claim 5 is the pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein the total denier number of one cord of the first ply is D1, When the total number of denier of one 2-ply cord is D2, D
The feature is that 2 / D1> 1.

The pneumatic radial tire for passenger cars according to claim 6 is the pneumatic radial tire for passenger cars according to claim 1 or 2, wherein 0.5 g / denier (g) of one cord of the first ply is used. / D) When the elongation under load is L1 and the elongation under load of 0.5 g / denier (g / d) for one cord of the second ply is L2, L1 / L2> 1 It has a feature.

A pneumatic radial tire for a passenger vehicle according to claim 7 is the pneumatic radial tire for a passenger vehicle according to any one of claims 1, 2, 3, 4, 5 or 6, wherein both the first ply and the second ply are used. It is characterized by using a polyester cord. The pneumatic radial tire for a passenger vehicle according to claim 8 is the pneumatic radial tire according to claim 1, 2, 3, 4,
The pneumatic radial tire for a passenger vehicle described in 5, 6, or 7 is characterized in that the first ply is composed of one layer and the second ply is composed of one layer.

Here, the definitions of the first ply and the second ply are as follows. That is, the first ply extends in a toroidal shape across a pair of bead cores in a ply of rubber-covered radial-aligned organic fiber cords, and extends at least one layer around the bead cores by folding back from the inner side to the outer side in the axial direction of the tire. It is the ply of. The second ply is at least one ply in which the ply is not folded back around the pair of beads.

[0014]

In the tire structure II in which at least one ply is not folded back around the bead core, since the ply tension that the second ply bears is low, the steering stability of the tire is deteriorated. By increasing the tensile elastic modulus E2 per unit width of the second ply in comparison with the tensile elastic modulus E1 per unit width of the first ply, the load of the ply tension of the second ply is increased to control the tire. The stability can be improved.

When the ratio of the tensile elastic moduli, E2 / E1, is 1.05 or more, the effect of improving the steering stability of the tire is recognized, and even if it exceeds 3.00, the effect of improving the steering stability is recognized. However, when it exceeds 3.00, the difference in tensile elastic modulus between the first ply and the second ply becomes too large. As a result, when the carcass receives repeated input due to the actual running of the tires, the input load ratio difference between the first ply and the second ply becomes too large. Due to this, the fatigue property of the cord is biased, and as a result, any ply will be prematurely failed. Therefore, in order to achieve both steering stability and durability of the tire, E2 / E1 is 1.05
As described above, the optimum point is located at 3.00 or less.

In order to design E2 / E1 to be 1.05 or more, preferably 1.05 to 3.00, the number of cords per unit width, the cord twist coefficient, and the total denier of cords are set. Number, cord elongation at 0.5 g / d, cord material, number of plies, etc. are properly combined. In that case, regarding cord number, N2 / N1> 1, cord twist coefficient about,
R1 / R2> 1, the total number of denier of the cord is D2 / D1> 1, and the elongation of the cord at 0.5 g / d is not necessarily L1 / L2> 1.
This is preferable in designing the optimum E2 / E1.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a pneumatic radial tire for passenger cars as a conventional example for only the left half of the tire. From the description in the drawing, the crown portion 1, the bead portion 2, the crown center 3, the carcass 4, the belt 5, the bead core 6, the bead heel 7, the first ply 8, the folded portion 1
The names of tire components such as 0 are self-explanatory.

FIG. 2 shows an embodiment of a pneumatic radial tire for passenger cars according to the invention, again only on the left half of the tire. In the tire structure shown here, the carcass 4 has a ply of rubber-coated radial array organic fiber cords extending in a toroidal manner between a pair of bead cores 6 and extending around the bead wires 6 in the axial direction of the tire. The first ply 8 having the folded-back portion 10 of the ply that extends back from the inside to the outside, and the bead portion 2 along the tire axial direction outer side of the folded-back portion 10 while straddling in a toroidal shape similarly between the pair of bead cores 6. Second ply 9 extending toward the bead heel 7 of the second ply, and the tensile elastic modulus per unit width of the second ply (E2
) Is larger than that of the first ply (E1) and is E2 /
E1 is greater than 1.05.

Although FIG. 2 shows an example in which the first ply and the second ply each have one layer, they may have a plurality of layers, and when the carcass is an odd number of layers of three or more, the first ply is used. Is often one more than the second ply.

In the structure of the tire shown in FIG. 3, the first ply 8 forming the carcass 4 is the same as the tire A, but the second ply 9 extends in a toroidal shape between the pair of bead cores 6. Instead, it extends from the shoulder portion of the tire toward the bead portion 2 along the tire axial direction outer side of the folded portion 10. The tensile modulus (E2) per unit width of the second ply is the same as that of the first ply (E1).
And E2 / E1 is greater than 1.05.

In the structure of the tire shown in FIG. 4, the first ply forming the carcass 4 is the same as that of the tire shown in FIG. 1, but the second ply 9 straddles between the pair of bead cores 6 in a toroidal shape. Not, belt 5 and first ply 8
It extends along the tire axial direction outer side of the folding | returning part 10 from between. The tensile modulus (E2) per unit width of the second ply is larger than that (E1) of the first ply, and E2 / E1 is larger than 1.05.

The carcass ply cord (fiber adhesion treatment cord) of the present invention can be manufactured, for example, by the following method.

First, the polyester according to the present invention is
Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene 2,6 dicarboxylic acid, sodium 3,5 di (carboxy) benzene sulfonate, etc., aliphatic dicarboxylic acids such as adipic acid, sebacic acid, etc., or their esters , Ethylene glycol, diethylene glycol, 1,
2-propylene glycol, 1,4-butanediol,
A polyester synthesized from a diol compound such as 1,6-hexanediol, neopentyldiol, cyclohexane-1,4-dimethanol, and preferably 85.
Copolymerized polyethylene terephthalate such that mol% or more is polyethylene terephthalate, and more preferably substantially all polyethylene terephthalate.

In producing a raw yarn from such polyester as a raw material, a solid-phase polymer (relative viscosity of 1.5
1) is rapidly cooled under a spinneret in a gas atmosphere of 10 to 60 ° C., and at this time, optimum conditions within a spinning speed of 2000 to 6000 m / min and a draw ratio of 1.10 to 2.20 are selected. .

The original yarn thus produced is twisted into a ply, and the plied twisted cords are combined and ply-twisted.

The cord thus twisted is treated with an adhesive under the following conditions. First, it is immersed in a resorcinol-formaldehyde-latex adhesive and 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 260 ° C., respectively. The treatment time is 60 to 160 seconds, the cord tension in the heat setting zone is 0.03 to 1.20 gf / D, and the cord tension in the normalizing zone is 0.03 to 0.50 gf /.
Set to the range of D and dry the cord. This makes it possible to obtain a predetermined adhesion processing code.

The trial production of the tire according to the present invention and the test results of the tire will be shown below.

Radial tires for passenger cars having the structure shown in FIG. 3 were manufactured in Tables 1 and 2 with tire size 205 / 65R15.
Using the various carcasses shown in 3 and 3, prototypes were made at the factory.

When the plural plies are applied to either the first ply or the second ply, the basic structure is the same as that shown in FIG. As a result, the influence of the basic carcass structure is eliminated as much as possible, and various tensile elastic moduli applied to the carcass ply, material, driving number, twist coefficient, total denier number, steering stability such as the number of plies, and tire durability. A tire was prototyped so that the effect on the tire's performance could be clearly understood. The carcass angle is 90 ° with respect to the circumferential direction, and the same applies when a plurality of plies are applied.

The belt is made of steel cord, and the twisted structure of the steel cord is 1 × 5 × 0.23. Two steel cord layers are laminated to form a belt, and the number of cords to be driven into the belt is 38/50 mm, and the belt angle is 26 ° on both sides with respect to the circumferential direction.

The test method applied to the analysis of this tire is as follows.

[Steering Stability] Each trial tire was mounted on a passenger car, and an actual vehicle feeling test was conducted at a speed of 60 to 200 km / hour, and (1) straight running stability, (2) turning stability, (3) ) With respect to items such as rigidity and (4) handling, a rating of 1 to 10 was given, and each item was averaged to give a rating of steering stability.

The evaluation was carried out by two professional drivers, and the average value of the scores of the two drivers was calculated and shown as an index with the control tire being 100. The larger the value, the better. [Tire Durability] Using a drum tester having a drum surface of smooth steel and a diameter of 1.707 m, the ambient temperature was controlled at 30 ± 3 ° C., the rim size was 6J-15, and the test internal pressure was 1.0 kg / Under conditions of cm ² and load of 650 kg, the vehicle was run until a failure occurred or up to 10,000 km.

According to the past results, if 10,000 km is not completed, there may be a problem in the market. Only those that completed the 10,000 km failure were evaluated as OK. Others were NG.

[Tensile Elastic Modulus Per Unit Width] A carcass layer near the maximum width of the tire side portion of the tire to be tested is sampled along the ply cord around the maximum width, along the ply cord, to a sample of 100 mm in length. Cut out (see Figure 5),
A sample was prepared by removing excess rubber above and below with a slicer so as not to damage the ply cord.

This sample was subjected to a tensile tester such as Instron or Autograph at 50 g / mm.
The initial load corresponding to is applied and the pulling speed is 50 mm from there.
A constant-speed tensile test is performed for 1 minute, and a load-elongation curve as shown in FIG. 6 is drawn.

The load axis (vertical axis) in FIG.
(5 mm width) Rewrite the stress to obtain the maximum point A (tangent angle maximum point) of load change due to elongation change near the origin from Fig. 6, and obtain the elastic modulus E (Kg / mm ² ) from the following formula. It was

E = Pl / l'S where P: unit width (25 m) at the maximum point A of the tangent angle
m) Load (Kg) S: Sample cross-sectional area per unit width (mm ² ) l: Initial length of test piece (mm) l ′: TH length (mm) in FIG.

[Number of cords to be imprinted] The number of cords to be imprinted according to the present invention means, in a ply in which cords are arranged in parallel, the number of cords contained per unit width of 50 mm in a plane perpendicular to the cords.

The number of cords of a plurality of plies is the number of cords contained in a plurality of plies per unit width of 50 mm, as in the case of a single ply.

[Twist Coefficient] The twist coefficient R according to the present invention is a physical quantity determined by the following equation.

R = NX (0.139XD / ρ) 1/2 X10-3 Here, N: number of twists per 100 mm of cord, D: total denier of cord, ρ: specific gravity of fiber.

[Total Denier Number] The total denier number of one cord according to the present invention is the length of the cord 9
When 000 m is 1 g, it is a unit expressed as 1 denier.

[Elongation at 0.5 g / denier load] The elongation of one cord according to the present invention at 0.5 g / denier load is obtained from a load-elongation curve obtained by a tensile test of the cord according to JIS1017. Desired. The test results are shown in Table 1, Table 2, Table 3, and Table 4 together with the carcass structure and material of the tire.

[0045]

[Table 1]

Table 1 shows only comparative examples.

In Comparative Example 1, the first ply and the second ply have the same tensile elastic modulus as in the conventional case (E2 / E1 =).
1.00), and the steering stability index of the tire to which this carcass was applied was set to 100 and displayed as an index. this is,
The same applies to Table 2, Table 3, and Table 4.

In Comparative Example 2, the number of cords to be imprinted in the second ply is increased as compared with that in the first ply, and E2 / E1 = 1.03.
Although the carcass structure is as follows, the effect of improving the steering stability was hardly recognized.

In Comparative Example 3, contrary to Comparative Example 2, E1 is replaced by E
The carcass structure is larger than 2 (E2 / E1 = 0.80), but the steering stability of this tire deteriorates.

[0050]

[Table 2]

Table 2 shows Examples 1-5.

In Examples 1 to 3, the same polyester cord was applied to both the first ply and the second ply, but the carcass structure tire in which the number of cords of the second ply increased was larger than that of the first ply. Is. E2 / E1 is 1.
It has been proved that the steering stability is improved with increasing numbers of 05, 1.25 and 1.30.

In Examples 4 to 5, steering stability of tires in which E2 / E1 was 1.08 and 1.15, respectively, by changing the twisting coefficients of the cords of the first ply and the second ply to which the same polyester cord was applied, was changed. The sex index is shown as E2 / E
It proves that the steering stability is greatly improved as 1 is increased.

[0054]

[Table 3]

Table 3 shows Examples 6 to 10.

In Examples 6 to 7, the total number of denier of the second ply was increased as compared with that of the first ply so that E2 / E1 was 1.42 and 1.71, respectively.
And the results for the increased carcass tire, it has been proven that increasing E2 / E1 also improves steering stability.

In Examples 8 to 9, the second ply cord of 0.
By lowering the elongation at 5 g / d compared to that of the first ply, the steering stability of a tire having a carcass with a large E2 / E1 is shown, but again, the steering stability of the tire is improved. You can see that it is done.

In Example 10, the material of the second ply was changed to aramid cord, and the elongation at 0.5 g / d was also lower than that of the first ply, so that E2 / E1 = 1.64. Although the tire has a carcass structure, the steering stability of the tire is greatly improved in this case as well.

[0059]

[Table 4]

Table 4 shows Examples 11 to 13.

Example 11 applies aramid to the second ply. In Example 12, two plies of polyester are applied to the second ply. Example 13 is an example of a tire in which one ply of polyester is used for the first ply and one ply of aramid cord is used for the second ply.

The E2 / E1 of Example 11 was 2.46, the E2 / E1 of Example 12 was 1.74, and the steering stability indexes of the tires having the respective carcass structures were the same as those of the tire of Comparative Example 1. By comparison, it has been proved to be greatly improved.

In Example 13, 4000 denier aramid cord was applied to the second ply, and E2 / E1 was 3.28.
As for the tires that were greatly increased, the steering stability of this tire was greatly improved, but the tire durability was not at a satisfactory level.

Therefore, it is understood that E2 / E1 is preferably 3.00 or less in order to achieve both the steering stability and the durability of the tire.

[0065]

As described above, in a pneumatic radial tire for passenger cars having a tire structure in which at least one ply is not folded around the bead core, the tensile elastic modulus per unit width of the second ply is The steering stability of the tire can be greatly improved by increasing it by 1.05 times or more as compared with that of one ply, and particularly preferably by increasing it from 1.05 times to 3.00 times. It was possible to provide a carcass structure that can satisfy the tire durability while significantly improving the durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire having a conventional structure having a carcass structure including two plies.

FIG. 2 is a cross-sectional view of a tire that is an embodiment of the present invention having a carcass structure composed of two plies.

FIG. 3 is a cross-sectional view of a tire that is an embodiment of the present invention having a carcass structure composed of two plies.

FIG. 4 is a cross-sectional view of a tire that is an embodiment of the present invention having a carcass structure composed of two plies.

FIG. 5 is an external view of a sample for measuring tensile elastic modulus cut out from the vicinity of the maximum width position of a tire.

FIG. 6 is a load-elongation curve obtained when measuring the tensile elastic modulus.

[Explanation of symbols]

 1 crown part 2 bead part 3 crown center 4 carcass 5 belt 6 bead core 7 bead heel 8 first ply 9 second ply 10 folded part

Claims (8)

[Claims] 1. A carcass comprising a carcass consisting of at least one layer of plies of radial arrangement cord extending in a toroidal shape between a pair of bead portions, and a belt layer consisting of a non-extensible cord arranged in the crown portion of the carcass. Is
At least one first ply having a folded portion of the ply extending around the bead core embedded in each bead portion from the inner side to the outer side in the axial direction of the tire, and along the outer side of the folded portion in the axial direction of the tire. In a pneumatic radial tire for passenger cars comprising at least one second ply extending toward the bead portion, the tensile elastic modulus per unit width of the first ply is E1, and the tensile elastic modulus per unit width of the second ply is Let E2 be
A pneumatic radial tire for passenger cars, characterized in that E2 / E1 ≧ 1.05. 2. The relationship between E1 and E2 is 3.00 ≧ E
2. The pneumatic radial tire for passenger cars according to claim 1, wherein 2 / E1 ≧ 1.05. 3. When the number of cords per unit width of the first ply is N1 and the number of cords per unit width of the second ply is N2, N2 / N1
The pneumatic radial tire for passenger cars according to claim 1 or 2, wherein the pneumatic radial tire is> 1. 4. The twist coefficient of the cord of the first ply is R
3. The pneumatic radial tire for passenger cars according to claim 1 or 2, wherein R 1 / R 2> 1, where R 1 is 1 and the twist coefficient of the cord of the second ply is R 2. 5. When the total denier number of one cord of the first ply is D1 and the total denier number of one cord of the second ply is D2, D2 / D1> 1
The pneumatic radial tire for passenger cars according to claim 1 or 2, characterized in that. 6. The elongation of one cord of the first ply under a load of 0.5 g / denier (g / d) is L1, and the cord of the second ply has a elongation of 0.5 g / denier (g). / D) When the elongation under load is L2, L1 / L2
The pneumatic radial tire for passenger cars according to claim 1 or 2, wherein the pneumatic radial tire is> 1. 7. The polyester cord is used for both the first ply and the second ply.
The pneumatic radial tire for passenger cars according to 2, 3, 4, 5 or 6. 8. The passenger vehicle air according to claim 1, wherein the first ply is composed of one layer, and the second ply is composed of one layer. Radial tires with.