JPS63207705A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To make a ride comfortable by forming each deformation volume of both end portions and the central portion of a belt to satisfy a particular relation with both small and specified inner pressure of a tire, in the case of a tire in which both end portions of belt layers arranged at a tire crown portion are reinforced. CONSTITUTION:In a radial tire having a structure in which the lower belt layer, out of two belt layers arranged on a tire crown portion, is folded inward at its both ends so that said both ends can be more reinforced than its central portion, carcass line of a tire section is indicated with 1 in case that the tire with its inner pressure 0.05 kg/cm<2> is only fitted on a rim. And the carcass line is lidicated with 2 in case that the tire is filled up with air to obtain inner pressure 2.0 kg/cm<2>. The subsequent forming process is carried out in such a manner that deformation volume F at each of both ends of the belt layer within 25% of the total width A of the belt and deformation volume G at the central portion of the belt respectively caused by filled inner pressure can satisfy such selation as 1.0G<F<2.0G, when the profiles of these carcass lines are compared with each other.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to a tire having a structure in which both ends of the belt layer disposed in the tire crown are reinforced more than the central part, particularly with an aspect ratio of 70% or less. The present invention relates to a pneumatic radial tire suitable for use in passenger cars.

[Conventional technology]

BACKGROUND ART Conventionally, demands for higher speeds and higher performance of cars have been increasing, and in response to these demands, there is a strong demand for tires to have further improved high-speed durability.

A radial tire with such required characteristics has belt layers that intersect with each other in the tire circumferential direction at the crown portion, but both outer portions of both ends of this belt layer have the characteristics of a laminated plate with separated ends. It is known that the belt tension decreases rapidly near the center.

As a measure to prevent this belt tension from decreasing, a belt structure in which the ends of the belt layer are bent, a so-called folded belt structure, or an organic fiber cord in which both ends of the belt layer are formed at an angle of substantially Oa with respect to the equatorial plane of the ear. Reinforced tires are known. However, although the above-mentioned fallen belt structure and those in which the ends of the belt layer are additionally reinforced with reinforcing materials are effective in improving durability during high-speed running,
It has been pointed out that the increase in out-of-plane bending rigidity at both ends of the belt layer deteriorates ride comfort performance. This decrease in ride comfort was particularly noticeable with flat tires that have a wide contact area.

In other words, generally the carcass line in the cross-sectional direction of the tire is
It is normal to adopt a profile based on the equilibrium profile theory, but if a profile based on the equilibrium profile theory is used for a folded structure or a belt structure in which the belt ends are additionally reinforced with a reinforcing material, it is possible to The belt tension becomes excessive, and the tension of the carcass adjacent to it decreases.Therefore, the belt tension on both outer sides of the belt tread becomes too high, causing deterioration in ride comfort performance due to an increase in the longitudinal spring constant, and lateral There was a problem that led to deterioration of steering stability due to a decrease in the directional spring constant.

In addition, in the sidewall portion of a radial tire (between the tire tread and the bead wire), there is a so-called flex zone where the deformation is greatest in the area on the tread side of the tire cross-section's maximum width position. In radial tires, this flex zone tends to be narrow and the ability to absorb external forces decreases.

Such a decrease in the ability to absorb disturbances not only deteriorates the ride comfort performance of the tire, but also reduces the ground contact area when the tire receives a load, causing a decrease in steering stability. Therefore, it is important to reduce the tension in the carcass located in the flex zone and increase its ability to absorb disturbances.

On the other hand, between the maximum cross section of the tire and the bead wire, a hard rubber layer called a bead filler is usually provided, or steel fibers are added to the carcass in order to compensate for the weakness of the lateral spring constant of radial tires. Alternatively, a reinforcing layer made of organic fibers may be placed at an angle to the circumferential direction, but as the carcass tension at this location decreases due to these installations, the increase in rigidity is small compared to the addition of the reinforcing material. .

Therefore, in order to further increase the rigidity, it is necessary to add reinforcing materials, but adding such reinforcing materials unnecessarily increases the weight of the tire, which is not desirable.

[Purpose of the invention]

An object of the present invention is to improve the ride comfort performance of a tire that occurs when a structure is adopted in which both ends of a belt layer placed in the tire crown are reinforced from the center, with the intention of improving the high-speed durability of the tire. To provide a radial tire that prevents deterioration and deterioration of steering stability. In other words, there is a trade-off between high-speed durability, handling stability, and ride comfort performance in radial tires that have a wide contact area with an aspect ratio of 70% or less, in which both ends of the belt layer are reinforced more than the center of the belt layer. It is an object of the present invention to provide a radial tire for a passenger car that eliminates the ambivalence and simultaneously satisfies these required characteristics.

[Structure of the invention]

The object of the present invention is to provide a radial tire having a structure in which both ends of the belt layer arranged in the tire crown are reinforced from the center, and the tire is simply assembled into an applicable rim with an internal pressure of 0.05 Kg7cm. Carcass line in cross section and internal pressure 2.0 K
When compared with the carcass line when the carcass line is filled with 25% of the total width of the belt due to the internal pressure filling, Deformation amount (G) is 1.0
Achieved by a pneumatic radial tire that satisfies the relationship G-<F<2.0G and in which the amount of radial inward movement of the maximum width position of the tire cross section is at least 5% or more as a ratio to the tire cross-sectional height. can do.

Hereinafter, the present invention will be specifically explained based on the drawings.

FIG. 1 is a sectional view showing an example of a carcass line frame of a radial tire according to the present invention, and is a diagram showing changes in the profile of the carcass line before and after the tire is mounted on a tire rim and filled with internal pressure. Also, for comparison, the second
The figure shows the carcass line framework of a conventional radial tire with profiles before and after filling with internal pressure.

In the figure, the dotted line (1) indicates that the internal pressure is 0.05 Kg/c.
This is the profile of the carcass line when the tire is attached to the tire rim at 2.0 Kg/
This is the profile of the carcass line when filled with an internal pressure of cm2. 3 is a belt layer arranged at the tire crown portion.

In this embodiment, two belt layers are provided, both ends of the lower belt layer are bent inward, and both ends are reinforced from the center. In the radial tire of the present invention, when comparing the two profiles of carcass lines (1) and (2) shown in FIG. It is necessary that the maximum value (F) and the deformation ffi (G) of the portion corresponding to the central portion of the belt layer satisfy the following relationship.

1.0 G < F < 2.0 G Here, F is the value at the point where the protrusion deformation is the largest in area B corresponding to 25% of the total width A of the belt layer at both ends of the belt layer. .

Further, G means the amount of protruding deformation at the center of the belt layer.

In the present invention, if this F value is smaller than 1.0G,
No decrease in belt tension was observed as the carcass tension at both ends of the belt layer increased, and no improvement in ride comfort could be expected. is undesirable because it becomes too excessive and the belt tension in the vicinity thereof decreases too much, which reduces the original high-speed durability.

In addition, in the case of a conventional tire, as shown in FIG. 2, the position of maximum weight in the cross section of the tire hardly changed before and after the internal pressure was filled, and was at COD. However, in the radial tire of the present invention, the maximum weight position of the tire cross section is moved radially inward as the internal pressure is filled, from the maximum weight position (D) of the carcass line (2) before the internal pressure is filled. Maximum weight position of carcass line (1) after internal pressure filling (C
) is required to be at least 5% in proportion to the tire cross-sectional height H), preferably 5%.
It is preferably within the range of ~15%. If the ratio is smaller than 5%, the carcass tension between the maximum width position of the tire cross section and the bead wire cannot be sufficiently increased, and the steering stability and ride comfort cannot be improved. If it is too large, the shear strain at the bead portion will become too high, which is unfavorable in terms of durability, so the upper limit is preferably about 15%.

FIG. 3 shows a tire that satisfies the requirements stipulated in the present invention and a tire designed using the equilibrium profile theory (
Calculate the state of carcass tension and belt tension at the time of filling the comparative tire with an internal pressure of 2.0 Kg/cm by using the finite element method. The belt 7 corresponds to the part from the center of the layer to the bead wire part.
FIG. 1 is a diagram showing the total tension and the total carcass tension, respectively.

In the figure, the solid line 4 is the tension distribution of the comparative tire, and the dotted line 5 is the tension distribution of the tire of the present invention.

J is a region of the belt layer, K is an outer region in the tire radial direction of the sidewall portion, L is an inner region in the tire radial direction of the sidewall portion, and M is a region where a part of the bead filler is inserted. As can be seen from FIG. 3, in the tire according to the present invention, the belt tension is lower at both ends of the belt layer than in the comparative tire, but the carcass tension is significantly increased. It is also seen that the carcass tension in the bead filler region at the bead wire tire cross-sectional maximum width position is high, and the tension between the belt layer side end and the tire cross-sectional maximum width position (flex zone) is low.

As described above, by reducing the carcass tension at both ends of the belt layer and in the flex zone, an increase in the longitudinal spring constant can be suppressed and ride comfort can be improved. In addition, the carcass tension is increased in the bead filler area, making it possible to increase rigidity without adding extra reinforcement, i.e. without unnecessarily increasing weight, improving handling stability. can be done.

Next, as a method for manufacturing the tire of the present invention, basically known radial tire manufacturing methods and conditions are applied, but the amount of deformation of both ends of the belt layer before and after filling the internal pressure specified in the present invention ( The manufacturing conditions for a tire that satisfies F) and the amount of movement in the tire radial direction are to make the radius (in the cross section) of the belt small at both ends, and to set the maximum width position of the side part to the equilibrium carcass line. This can be done by determining the shape of the tire during vulcanization so as to set it higher than the actual value, but it is necessary to estimate the amount of deformation in advance for each tire size using a finite element method or the like.

[Examples and comparative examples]

A tire of the present invention and a comparative tire based on the equilibrium profile theory, each having the specifications shown in Table 1, were created using green tires having the same structure and a tire size of 205/60 R15.

In manufacturing the tire of the present invention, a mold was used which was created by estimating the amount of deformation using the finite element method using the method described above.

For these two types of tires, indoor single spring constant measurements,
Indoor cornering tests, EM over bumps, and handling stability and ride comfort tests were conducted by a panel of five people. The results are shown in Tables 2-4. In addition, Fig. 4 shows the relationship between cornering force (Kgf) and slip angle (deg) measured using a flat belt cornering tester under the conditions of a load of 400 kg, an air pressure of 2.0 kg/cs+'', and a rim of 6JJX 15. 4, the dotted line indicates the tire of the present invention, and the solid line indicates the comparative tire.

Table 2 shows that the tires of the present invention have smaller impact forces in both the vertical and longitudinal directions, and have excellent ability to ride over protrusions, compared to the comparative tires.

From Table 3 and FIG. 4, it can be seen that the tire of the present invention has a lower longitudinal spring constant but a higher lateral spring constant and higher cornering force than the comparative tire.

Further, from the actual running test results shown in Table 4, it can be seen that the tire of the present invention exhibits excellent handling stability and ride comfort, and satisfies both performances at the same time.

(Hereafter, margin) Table 1 Table 2 Drum diameter (diameter): 2500m+n.

Load: 400 Kg, Air pressure: 2. OKg/cm”
, Speed: 20-100 m/hr, , Rim: 6JJX
Note: The total impact force from 20 to 100 Km/hr is expressed as an index with the value of the comparative example as 100.

Table 3 Load: 400 kg, Air pressure: 2. OKg, rim:
6JJ

Table 4 Maneuvering stability test: JARI Comprehensive Test Road Test Conducted on knee route.

Test vehicle: Domestic 2000cc passenger car, weight 1:14
00 Kg, air pressure: 2. OKg/cm”, rim:
6JJ

〔Effect of the invention〕

According to the present invention, by optimizing the carcass profile of a radial tire, especially a flat radial tire, in which both ends of the belt layer placed in the tire crown are reinforced, the efficiency of carcass tension is increased and the original high-speed stability is achieved. In addition to performance, it is possible to satisfy improvements in handling stability and ride comfort performance.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing examples of carcass line frames of a radial tire according to the present invention and a conventional radial tire, respectively, and FIG. 3 is a cross-sectional view showing an example of a carcass line frame of a radial tire according to the present invention and a conventional radial tire, and FIG. Figure 4 shows the carcass tension distribution and belt tension distribution of a conventional tire corresponding to the area from the center of the belt layer to the bead wire, and Figure 4 shows the slip angle measured using a flat belt cornering tester. FIG. 3 is a diagram showing the relationship between cornering force and cornering force. 1... Carcass line before filling with internal pressure, 2... Carcass line after filling with internal pressure, 3... Belt layer, 4... Tension distribution of conventional tire, 5... Tension of tire of the present invention Distribution, E: Amount of movement of the maximum weight position of the tire cross section, F: Maximum protruding deformation amount of the carcass line at both ends of the belt layer, G: Amount of deformation of the carcass line at the center of the belt layer.

Claims (2)

[Claims] (1) In a radial tire with a structure in which both ends of the belt layer placed in the tire crown are reinforced from the center, the carcass in the cross section of the tire is simply assembled into an applicable rim with an internal pressure of 0.05 Kg/cm^2. Line and internal pressure2.
When compared with the carcass line when filled with 0 kg/cm^2, the amount of deformation (F) within 25% of the belt total width at each end of the belt layer due to the internal pressure filling
and the amount of deformation (G) at the center of the belt satisfy the relationship 1.0G<F<2.0G, and the amount of movement inward in the radial direction of the maximum width position of the tire cross section is the ratio to the cross-sectional height of the tire. A pneumatic radial tire characterized in that the pneumatic radial tire is at least 5% or more. (2) The pneumatic radial tire according to claim 1, which has an aspect ratio of 70% or less.