JP2001233025A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of concurrently improving steering stability and low rolling resistance performance. SOLUTION: A reinforcing cord layer arranged in a side face area from a toe of bead to a sidewall part has inner and outer cord layers divided into two layers in a tire radial direction along a one side face of bead filler rubber. The inner and outer cord layers each comprise layers of more than one rubber covered continuous cord of mutually different types helically wound around a tire axis. Cords of each layer of the inner and outer cord layers have mutually different elastic moduli.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic radial tire for use in relatively small vehicles such as passenger cars and similar vans and pickups, and more particularly to steering stability and rolling performance. The present invention relates to a pneumatic tire having both particularly improved resistance performance.

[0002]

2. Description of the Related Art In recent years, along with the emergence of environmental problems and global warming problems on a global scale and the advancement of automobile performance, pneumatic tires for automobiles, especially tires used in relatively small vehicles mentioned at the beginning, have become increasingly popular. While further improvements in fuel economy performance (low rolling resistance performance) and the like are required, there is also a need to improve steering stability performance, and there is a tendency that demands for simultaneously improving both of these performances are increasing. .

With respect to this demand, means for individually improving each performance have been established as described below. That is,
(1) Means for improving steering stability performance: securing cornering power, improving tire rigidity, increasing the hysteresis loss of tread rubber, and (2) Improving rolling resistance performance: reducing tire rigidity, reducing hysteresis loss of the tread rubber. .

[0004]

As described above, it is possible to improve individual performance. However, one of the means for improving the steering stability performance and the low rolling resistance performance is to improve the tire rigidity. On the other hand, the improvement direction is opposite because the other is a reduction in tire rigidity. In other words, at present, both performances are in conflict with each other.

For example, as shown in a perspective side view of FIG. 4, a rubber-coated steel cord layer called a bead-section insert ply or a rubber layer is provided on a side area from a bead section to a sidewall section to improve steering stability. Specific means for increasing the tire rigidity by disposing the coated organic fiber cord layer as the reinforcing cord layer 20 is applied.

Since these reinforcing cord layers 20 are arranged layers of a large number of cords 20C inclined in the tire circumferential direction, the tires are arranged in a radial direction (load application direction), a lateral direction (tire axis direction), and a front-rear direction (tire direction). As a result, the steering stability is improved, but the flexibility of the sidewall portion is impaired, so that the rolling resistance performance is reduced. In particular,
In order to greatly improve the steering stability, it is necessary to increase the width of the reinforcing cord layer in the tire radial direction, and the degree of reduction in the rolling resistance performance is increased.

[0007] Accordingly, the inventions according to claims 1 to 9 of the present invention solve the above-described two-handed inversion problem from the basics, and can simultaneously improve steering stability and reduce rolling resistance. The purpose is to provide.

[0008]

According to a first aspect of the present invention, there is provided a tread portion having a pair of sidewall portions and a pair of bead portions connected to both sides of the tread portion. A radial carcass of at least one ply that reinforces each part between bead cores embedded in a bead part, and a belt made of two or more rubber-coated cord layers that reinforces a tread portion at the outer periphery of the radial carcass. In a pneumatic tire having a bead filler rubber extending in a tapered shape from the bead portion to the end of the tread portion, and a reinforcing cord layer disposed in a side surface region from the bead portion to the sidewall portion, the reinforcing cord layer is
An inner and outer cord layer divided into two layers in the tire radial direction along one side surface of the bead filler rubber, and each of the inner and outer cord layers is helically wound around one or more rubber-coated continuous cords of different types. The pneumatic tire is composed of a plurality of layers, and each of the cords of the inner and outer cord layers has a different elastic modulus from each other.

According to the invention described in claim 1, claim 2 is provided.
According to the invention described in, at 25 ° C., 0.5 to the value of the ratio E _B / E _A code modulus E _B in one layer code elastic modulus E _A against the other layer of the inner and outer cord layer It is in the range of 0.7.

Further, according to the inventions described in the first and second aspects, as in the invention described in the third aspect, the cord elastic modulus E
Cord layer with _A is a inner code layer having a radially inner end a bead core outer periphery, the cord layer having a cord modulus of elasticity E _B is connected to the radially outer end of the inner cord layer The outer code layer.

Further, according to the invention described in claims 1 to 3, the cord taken out from the inner cord layer of the vulcanized new pneumatic tire as in the invention described in claim 4 is:
Having the above elastic modulus E _A 4 GPa at 25 ° C..

Further, according to the invention described in claims 1 to 4,
Then, as in the invention described in claim 5, the tire equatorial plane and
Height H of outer cord layer measured in parallel_B Of the inner code layer
Height H _A The ratio H to_B / H_A Is between 0.2 and 0.6
In range.

Further, relates the invention described in claims 1 to 5, according to the invention described in claim 6, the sum of the height H _B of the inner cord layer height H _A and the outer cord layer ( H _A + H
_B ) is in the range of 10 to 40% of the tire section height. Here, the tire section height is JATMA YEAR BOOK
In accordance with the definitions of the terms given in the general information in "Ghapter G" of (1999), the maximum air pressure corresponding to the maximum load capacity of a given tire is applied to the specified air pressure for the outer diameter of the tire during the description.

Further, according to the invention described in claims 1 to 6, as in the invention described in claim 7, the reinforcing cord layer is located between the radial carcass main body and the bead filler rubber.

Further, according to the invention described in claims 1 to 7, as in the invention described in claim 8, the cords of the inner code layer and the outer code layer are organic fiber cords. Like the invention described in claim 9,
Suitably, the cord of the inner cord layer is a polyethylene naphthalate fiber cord and the cord of the outer cord layer is a polyethylene terephthalate fiber cord.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of the pneumatic tire of the present invention, FIG. 2 is a see-through development view of a reinforcing cord layer viewed from the direction of arrow P shown in FIG. 1, and FIG.
FIG. 2 is an enlarged sectional view of a main part of the tire shown in FIG. 1.

The tire 1 shown in FIG. 1 is a pneumatic radial tire for use in a relatively small vehicle described at the beginning. The tire 1 has a tread portion 2 and a pair of sidewalls connected to both sides thereof. Part 3 and a pair of bead parts 4
And Each of these parts 2 to 4 has at least one ply extending between the bead cores 5 embedded in the bead part 4,
The illustrated example is reinforced by a one-ply radial carcass 6. Further, the tread portion 2 is reinforced by a belt 7 arranged on the outer periphery of the radial carcass 6.

The radial carcass 6 has at least one
The ply has a folded portion 6t that folds around each bead core 5 from the inside of the tire 1 to the outside. As the ply cord of the radial carcass 6, an organic fiber cord such as a nylon cord, a polyester cord, a rayon cord, a Kevlar cord, or an inorganic fiber cord or a steel cord such as a carbon fiber cord is applied.

The belt 7 has two or more layers, and the illustrated example has three layers.
The cord layers 7-1 and 7-2 on the inner side of the belt 7 form a cross cord layer in which the rubber coat cords of the respective layers intersect with the tire equatorial plane E interposed therebetween. The outermost cord layer 7-3 is formed of a spirally wound rubber-coated cord layer. The cords of the cross cord layers 7-1 and 7-2 are steel cords, and the cord of the spirally wound cord layer 7-3 is selected from organic fiber cords used for the radial carcass 6.

The bead portion 4 includes a bead filler rubber 8 tapering from the outer periphery of the bead core 5 toward the end of the tread portion 2, and the bead filler rubber 8 has a triangular cross section. The tire 1 has an inner liner rubber 9 on the inner surface. When the tire 1 is a tubeless tire such as a radial tire for a passenger car, a rubber having excellent air impermeability is applied to the inner liner rubber 9.

As shown in FIGS. 1 to 3, the tire 1 is provided with a reinforcing cord layer 10 in each of a pair of side surface regions from the bead portion 4 to the sidewall portion 3. Here, the reinforcing cord layer 10 extends along one side surface of the bead filler rubber 8, in the illustrated example, along the inner side surface of the tire 1, and is divided into two layers in the radial direction of the tire 1 (hereinafter referred to as a radial direction). It is assumed that layers 10A and 10B are provided.

Each of the inner and outer code layers 10A and 10B has
In the example shown in FIG. 2, one or more of the rubber-coated continuous cords 10AC and 10BC are formed of a spirally wound layer around the axis X of the tire 1. The types of the codes 10AC and 10BC are different from each other.

In FIG. 2, for convenience of explanation, the continuous code 10
AC winding start 10ACs to winding end 10ACe
, Adjacent rubber-coated cords 10AC are shown separated from each other, and similarly, the adjacent rubber-coated cords 10BC are shown separated from each other from the winding start end 10BCs to the winding end 10BCe of the continuous cord 10BC. Cords 10AC and 10BC adjacent to each other
Are bonded to each other via the covering rubber, and the spirally wound cord layer 10
A and 10B show perfect lamellarity.

The inner and outer code layers 10A and 10B are
The cords 10AC and 10BC of each layer are different from each other.
Shall have a power factor. For example, the inner code layer 10A
Modulus E of cord 10AC_A But the outer code layer 10B
Modulus E of cord 10BC _B Larger value than
And the elastic modulus E of the cord 10BC_B Is code 10A
Modulus E of C_A With a value greater than
Is allowed.

First, the steering stability performance is not determined by the degree of the overall rigidity of the tire, which is largely determined.
Quality is determined by the rigidity of the tread portion 2 and the rigidity of the side surface region from the bead portion 4 to the sidewall portion 3 and the degree of rigidity. Above all, the stiffness of the side surface area has a high contribution rate to the steering stability performance, and the stiffness in the traveling direction of the tire 1, that is, the stiffness in the front-rear direction affects the steering stability performance. Performance improves.

Next, the rolling resistance is caused by the hysteresis loss of the viscoelastic body, mainly rubber, and thus the organic fiber cord due to the repeated ground deformation of the tire 1 rolling under a load, and this loss is caused by heat. Is converted. The outer rubber of the side wall portion 3 has physical properties of low hysteresis loss, and the inorganic fiber cord including the organic fiber cord or the steel cord has much more physical properties of low hysteresis loss. Therefore, the lower the radial rigidity of the side wall portion 3, the lower the rolling resistance.

Here, the inner and outer cord layers 10A, 10B of the reinforcing cord layer 10 are all continuous cords 10AC, 10C.
As a spiral wound layer of BC, the tire 1 has higher rigidity as a basic characteristic in comparison with the conventional tire having the reinforcing cord layer 20 with respect to the longitudinal rigidity, and as a result, the steering stability performance is improved.

On the other hand, regarding the rigidity in the radial direction, the reinforcing cord layer 10 composed of the inner and outer cord layers 10A and 10B depends on the number of cords 10AC and 10BC to be driven (the number of cords included per unit length). Since it has the basic property of hardly bending in the radial direction, that is, high radial rigidity,
Disadvantageous for low rolling resistance.

[0029] Therefore, for example, a code elastic modulus E _A code 10AC, to increase than the elastic modulus E _B code 10BC, conversely, the other code modulus E _B lower than one code elastic modulus E _A By doing so, the disadvantage to the low rolling resistance can be advantageously switched. Or, it is possible to similar transformation by lower than the elastic modulus E _B the elastic modulus E _A. Therefore, it is possible to obtain the tire 1 exhibiting a much lower rolling resistance performance than the conventional tire.

In practice, at 25 ° C., the inner and outer cord layers 10
A, cord elastic modulus E of one layer of 10B_A The other
Cord modulus E of layer_B Ratio E_B / E_A 0.5 to
Within the range of 0.7. By setting it within this range,
Advantageously low rolling resistance while improving stability performance
Tire 1 capable of realizing the performance
You. Where the ratio E_B / E_A If the value of
Stiffness in the front-rear direction is too small, and desirable steering stability
No improvement in performance can be obtained and the ratio E_B / E _A of
If the value exceeds 0.7, the radial rigidity becomes too high.
Both are incompatible because of the increased rolling resistance.

The cord layer having a cord modulus of elasticity E _A described above, and an inner code layer 10A having a radially inner end a bead core 5 near the outer periphery, the cord layer having a cord modulus of elasticity E _B is the inner cord layer The outer cord layer 10B connected to the radially outer end of 10A is suitably adapted. This is because, the inner cord layer 10 having a higher code modulus E _A
A contributes to the steering stability, while the sidewall 3
This is because the resistance to the deflection of the roller is small, and the contribution to the increase in the rolling resistance is small.

Further, the vulcanized new elastic modulus E _A code 10AC which was taken out from the inside cord layer 10A of the pneumatic tire 1 is adapted have a value of more than 4GPa at 25 ° C.. This is because the elastic modulus E _A becomes insufficient longitudinal direction rigidity is less than 4 GPa, because not obtained improvement in preferred steering stability.

Further, with reference to FIG. 3, the ratio H to the height H _A of the inner cord layer 10A of the height H _B of the outer cord layer 10B, as measured parallel to the tire equatorial plane E (mm) (mm) _B /
Suitably, the value of _HA is in the range of 0.2 to 0.6. Here, the value is less than 0.2 of the ratio H _B / H _A can not be exhibited low rolling resistance performance to expect the ratio H _B
When the value of / _HA exceeds 0.6, the improvement in steering stability performance becomes insufficient.

Further, the value of the sum H _A + H _B between the height H _B of the inner cord layer 10A height H _A and the outer cord layer is a tire section height SH of the (mm, according to the definition above) 10-40
It is within the range of%. Here, if it is less than 10%, the effect of improving the steering stability cannot be obtained, and
If it exceeds, the rolling resistance increases, and all are incompatible. In addition, the tire cross-section height SH shown in FIG. 1 is indicated by a height from a straight line RL parallel to the tire axis X passing through the applicable rim diameter position, that is, a so-called rim diameter line RL.

Based on the above description, as a whole, as shown in FIGS. 1 to 3, the reinforcing cord layer 10
Body 6b of radial carcass 6 and bead filler rubber 8
Positioning between these points is advantageous for improving both the steering stability performance and the low rolling resistance performance. However, this does not exclude that the radial carcass 6 is disposed along the inside or outside of the folded portion 6t.

It is effective that the cords 10AC and 10BC of the inner cord layer 10A and the outer cord layer 10B are organic fiber cords. More specifically, as a typical example, the inner cord layer 10A Is a polyethylene naphthalate fiber cord, and the cord 10BC of the outer cord layer 10B is a polyethylene terephthalate fiber cord.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A radial ply tire for a passenger car, having a size of 195 / 65R15, has a structure similar to that shown in FIGS. Radial carcass 6 is 1000D / 2
The belt 7 is a 2-ply polyester cord.
It has two steel cord cross layers 7-1 and 7-2 and one nylon cord spiral wound layer 7-3. Reinforcing cord layer 1
A polyethylene naphthalate fiber cord is applied to the cord 10AC of the inner cord layer 10A of the outer cord layer 10A.
The tires of Examples 1 to 6 in which a polyethylene terephthalate fiber cord was applied to the cord 10BC of 0B were manufactured.

In order to evaluate the example tires, the tires of the prior art example 1 without the reinforcing cord layer 20 and the tires of the prior art example 2 with the insert ply 20 of one rubber-coated steel cord layer deviated from the conformity values. The tires of Comparative Examples 1 to 7 including the reinforcing cord layers of the inner and outer cord layers having cords were prepared. All of these tires were the same as the example tire except for the reinforcing cord layer.

The code 1 for the elastic modulus E _A (GPa) of the code 10AC of each example tire and each comparative example tire.
The value of the ratio E _B / E _A of 0BC elastic modulus E _B (GPa), modulus of code 10AC taken out from a new tire E _A
(GPa) values, the ratio of the inner cord layer 10A of the height H _B of the outer cord layer (mm) to the height H _A (mm) H _B /
Ratio tire section height SH (mm) value and the height H _A of the H _A, the sum of _{H B H A + H B (} mm) (H A + H B)
Table 1 shows the values of / SH. The elastic modulus E _A, is E _B is the value measured at 25 ° C..

[0040]

[Table 1]

Each of the above tires is applied to a rim 51/2 J × 15
, And charged with an internal pressure of 200 kPa, and the following two tests were performed. (1) Steering stability performance test: Each tire is mounted on four wheels of a two-passenger passenger car, the vehicle runs on a test course, and a score is given based on feeling. The standard of the rating was ± 0 for the tire of Conventional Example 1, and a method of adding points (plus +) to this was adopted. The larger the value of the additional point (+), the better. (2) Rolling resistance test: The rolling resistance at a speed of 80 km / h under a load of 5.3 kN was measured, and the measurement result was represented by an index with the tire of Conventional Example 1 being 100. The larger the value, the higher the rolling resistance. The value was high. The results are shown in Table 1. In Table 1, the rolling resistance is abbreviated as RR.

From the results shown in Table 1, it can be seen that the tires of Examples 1 to 7 had the same level of rolling resistance and the same level of rolling resistance as that of Conventional Example 1, and the steering stability was greatly improved. On the other hand, in the tire of Conventional Example 2, while the steering stability performance in comparison with the tire of Conventional Example 1 is greatly improved, the rolling resistance value is also significantly increased. Further, the tires of Comparative Examples 1 to 7 show the same tendency as the tire of Conventional Example 2, or do not show improvement in the steering stability performance.

[0043]

According to the first to ninth aspects of the present invention, the reinforcing cord layer is divided into two inner and outer spirally wound cord layers, and a cord having a higher elastic modulus is applied to the inner cord layer. Thus, it is possible to provide a pneumatic tire capable of simultaneously improving the steering stability performance and the rolling resistance performance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a pneumatic tire according to the present invention.

FIG. 2 is a perspective development view of a reinforcing cord layer of the present invention.

FIG. 3 is an enlarged sectional view of a main part of the tire shown in FIG.

FIG. 4 is a perspective plan view of a reinforcing cord layer of a conventional tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Radial carcass 6b Radial carcass body 6t Folding part 7 Belt 8 Bead filler rubber 9 Inner liner 10 Reinforcement cord layer 10A Inner cord layer 10B Outer cord layer 10AC Inner code layer cord 10BC Outer code layer cord 10ACs, 10BCs Cord winding start end 10ACe, 10BCe cord winding end E Tire equatorial plane X Tire axis

Claims (9)

[Claims] A radial carcass having at least one ply having a tread portion, a pair of sidewall portions and a pair of bead portions connected to both sides thereof, and reinforcing each of these portions between bead cores embedded in the bead portion; A belt comprising two or more rubber-coated cord layers for reinforcing the tread portion at the outer periphery of the radial carcass, a bead filler rubber tapering from the outer periphery of the bead core toward the end of the tread portion, and a portion extending from the bead portion to the sidewall portion. In a pneumatic tire having a reinforcing cord layer arranged in a side surface region, the reinforcing cord layer has an inner and outer cord layer divided into two layers in the tire radial direction along one side surface of the bead filler rubber, A spiral wound layer around the tire axis of one or more rubber-coated continuous cords of different types. , Each layer of the code of the inner and outer cord layer is a pneumatic tire characterized by having a different elastic modulus from each other. At 2. A 25 ° C., the value of the code elastic modulus of one layer of the inner and outer cord layer (E _A) against the code modulus of the other layer the ratio of _{(E B) (E B /} E A) is 0 The tire according to claim 1, which is in the range of 0.5 to 0.7. 3. The cord layer having a cord elastic modulus (E _A ) is an inner cord layer having a radially inner end near the outer periphery of a bead core, and the cord layer having a cord elastic modulus (E _B ) is: 3. The tire according to claim 1, wherein the tire is an outer code layer that is continuous with an outer end of the inner code layer in the tire radial direction. 4. 4. A code taken out from the inside cord layer of vulcanized new pneumatic tire, in any one of claims 1 to 3 having a 4GPa or more elastic modulus (E _A) at 25 ° C. The tire described. Value of 5. A tire equatorial plane and the height of the parallel measured outer side cord layer (H _B) the ratio of the height of the inner cord layer _{(H A) (H B /} H A) is 0. The tire according to any one of claims 1 to 4, which is in a range of 2 to 0.6. The value of the height of 6. inner cord layer (H _A) and the outer cord layer height sum of _{(H B) (H A +} H B) is 10 to 40% of the tire section height Claims 1 to 5 in the range of
A tire according to any one of the preceding claims. 7. The reinforcing cord layer is located between the radial carcass body and the bead filler rubber.
6. The tire according to any one of items 6 to 6. 8. The tire according to claim 1, wherein each cord of the inner cord layer and the outer cord layer is an organic fiber cord. 9. The cord of the inner cord layer is a polyethylene naphthalate fiber cord, and the cord of the outer cord layer is a polyethylene terephthalate fiber cord.
Tire described in.