JPH061121A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve road hazard resistance and traveling performance on the rough road by restricting the correlation between the thickness of side wall rubber and the hardness of the rubber at a position in the maximum width part of a tire, and determining the upper limit and lower limit of rubber hardness. CONSTITUTION:JIS A hardness Y of the outside part of a tire structure body of a side wall section 3 satisfies the relationship shown by the expression I to the thickness of rubber X (unit mm) at a position in the maximum width part of a tire, and is also made of side wall rubber 10 whose hardness is in a range from 50 deg. to 65 deg. in JIS A hardness, In addition, the ratio of the thickness X of the side wall rubber 10 at a position in the inside of the maximum width part of the tire in the radial direction of the tire to the thickness Xf of the rubber at a position in the outer end position in the radial direction of the rim flange 12 of the inside in the radial direction, i.e., Xf/X is restricted in a range from 1.3 to 1.8, and the ratio of the thickness X of the side wall at a position in the maximum width part of the tire to the thickness Xd of the inner end in the radial direction of the buttress part of the tire in the outer side in the radial direction, i.e., Xd/X is restricted in a range from 1.0 to 1.3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire for a passenger vehicle, which can reduce the damage of the sidewall portion during traveling on a bad road and enhance the safety of traveling without impairing the steering performance and riding comfort.

[0002]

2. Description of the Related Art In recent years, in order to save energy, the weight of vehicles has been reduced, and the demand for reducing the weight of tires has been increasing. In order to reduce the weight of tires, in addition to the tire frame structure such as the carcass and the belt layer, the thickness of the rubber forming the sidewall portion is also an important factor.

[0003]

However, in order to promote the weight reduction, when the rubber thickness of the sidewall portion is extremely thin, the sidewall portion is run by traveling on a bad road such as a gravel road. There is a problem that a so-called road hazard occurs in which foreign matter collides with the outer surface of the tire and scratches the tire.

A large bending stress acts on the sidewall portion at the maximum width position of the tire, and the rubber thickness at this maximum width position greatly affects the road hazard.

As a result of repeated research by the inventor in order to improve road hazard resistance while maintaining maneuverability and riding comfort, the road hazard resistance is determined by the rubber hardness in addition to the rubber hardness at the maximum width position. We found that it was appropriate to regulate in the context of.

Therefore, test tires having various rubber thicknesses and rubber hardnesses were produced as trials, and the road hazard resistance was tested under certain conditions. As a result, Y> (0.149X ² -3.7X + 72.0 ) Here, it has been found that the load hazard resistance is enhanced by satisfying the formulas of Y: rubber hardness (JISA hardness) X: rubber thickness at maximum width position (unit: mm).

The present invention has the gist of restricting the sidewall rubber in relation to the rubber hardness and the rubber thickness at the maximum width point, and enhances road hazard resistance while maintaining maneuverability and riding comfort, and It is intended to provide passenger car tires that can improve safety.

[0008]

According to the present invention, there is provided a carcass of a radial arrangement in which a tread portion extends from a tread portion to a sidewall portion and is folded back around a bead core of a bead portion, and a carcass disposed inside the tread portion and radially outside the carcass. A radial tire for a passenger vehicle comprising a tire structure using a cord including a belt layer, wherein the outer surface of the tire structure of the sidewall portion has a JISA hardness Y of a rubber in a tire maximum width position. The sidewall rubber satisfies the relationship shown in the following formula with respect to the thickness X (unit: mm), and has a JISA hardness of 50 degrees or more and 65 degrees or less and the sidewall rubber at the maximum tire width position. Ratio Xf / X is 1.3 to the thickness Xf of the rubber at the radially outer end position of the rim flange on the inner side in the radial direction of 1.3.
Above and below 1.8, the sidewall rubber thickness X at the tire maximum width position and the rubber thickness X at the tire radial inner end of the buttress portion of the tire radially outward thereof.
A radial tire for passenger cars, characterized in that the ratio Xd / X with d is 1.0 or more and 1.3 or less and the thickness gradually increases from the tire maximum width position to the radially inner side and the outer side. ^{Y> (0.149X 2 -3.7X + 72.0} )

[0009]

The outer side portion of the tire structure of the sidewall portion has a thickness X (mm) and a J value at the maximum tire width position.
As described above, the ISA hardness Y is regulated in the relation of Y> (0.149X ² -3.7X + 72.0).

The maximum width position of the tire is a position where the largest bending action force is applied when the tire is loaded, and the thickness X and the hardness Y at this position have the greatest influence on the steering performance, the riding comfort and the road hazard. .

The above expression is an expression obtained by an experiment for the relationship between the thickness X and the hardness Y, and shows that the thinner the thickness X, the higher the hardness Y needs to be. However, when a hard rubber having a JIS A hardness of more than 65 degrees is used as the sidewall rubber, the road hazard resistance is improved, but the riding comfort and the steering stability are deteriorated. If it is attempted to maintain riding comfort and steering stability while maintaining this hardness, the thickness X becomes 1 mm or less, and there is a risk of damage such as cracking of the sidewall portion due to insufficient strength.

[0012] Here, the road hazard means that when traveling on a bad road in which hard foreign matters such as gravel and crushed stone are scattered, the foreign matters scatter and collide with the outer wall surface of the sidewall portion, and the outer wall surface is damaged. Say that. If the outer wall surface of the sidewall portion is damaged, the vehicle cannot run, which is very dangerous.

On the other hand, if the hardness Y is not more than 50 degrees in JISA hardness, load hazard is likely to occur unless the thickness X of the rubber is increased, and the thickness X of the rubber increases.
Tire weight increases, leading to higher costs.

As described above, according to the present invention, in addition to the relationship between the hardness Y and the thickness X according to the above formula, the upper limit and the lower limit of the hardness Y are regulated to maintain the maneuverability and the riding comfort while maintaining the durability. Road hazard is enhanced. FIG. 2 shows the restricted range of the invention of the present application by the shaded portion.

Further, in the present application, the rubber thickness Xf at the radial outer end position of the rim flange and the rubber thickness Xd at the inner end of the buttress portion are the rubber thicknesses at the width positions, respectively. Xd is regulated by the ratio with the rubber thickness X at the maximum width position, and the thickness is gradually increased inward and outward in the radial direction from the tire maximum width position. While maintaining the above, the road hazard resistance is efficiently enhanced.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the drawing, a radial tire 1 for a passenger car comprises a tire structure 9 including a carcass 6 and a belt layer 7 arranged inside the tread portion 2 and outside in the radial direction of the carcass 6, and also the sidewall portion. The portion of No. 3 arranged on the outside of the tire structure 9 is composed of the sidewall rubber 10 regulated in the relationship between the hardness of the rubber and the thickness of the rubber.

Further, the radial tire 1 for passenger cars comprises a tread portion 2, sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2, and a bead located inside the sidewall portion 3 in the radial direction. And part 4.

The carcass 6 extends from the tread portion 2 to the bead portion 4 through the side wall portion 3 to the main body portion 6a.
The bead core 5 on which the bead portion 4 is arranged is folded back from the inner side in the axial direction of the tire toward the outer side, and the tip is formed of a folded back portion 6b extending near the tire maximum width position B. The carcass 6 is 70 to 90 with respect to the tire equator C.
The carcass ply 6A, 6A comprises at least one carcass ply 6A, 6A having a radial or semi-radial arrangement of carcass cords arranged at an angle of 0 °. It is arranged in the direction to intersect. As the carcass cord, organic fiber cords such as nylon, polyester, rayon, aromatic polyamide are used.

The belt layer 7 comprises a plurality of belt plies 7A, 7A in this embodiment, and each belt ply is inclined at an angle of 10 to 30 ° with respect to the tire equator C. Moreover, belt cords that intersect each other are arranged between the belt plies 7A and 7A. As the belt cord, similar to the carcass ply, an organic fiber cord such as nylon, polyester, rayon, aromatic polyamide fiber or the like and a steel cord are used.

In this embodiment, the carcass 6 and the belt layer 7 having the above-mentioned structure form a tire structure 9 which forms the skeleton of the tire.

In the present embodiment, the body portion 6a of the carcass 6 is
A bead apex 8 made of hard rubber and having a triangular cross section is erected between the bent portion 6b and the folded-back portion 6b and outside the bead core 5 in the radial direction. The rubber hardness of the bead apex 8 is preferably set in the range of 50 to 70 ° of JIS A hardness. Further, in the bead portion 4, an inner chafer 21 surrounding the bead apex 8 together with the bead core 5 and an outer chafer 22 arranged outside the carcass 6 along the folded portion 6b are arranged. Reinforce part 4.

Further, the radial tire 1 for passenger cars has a rim J
Fit in. The rim J includes a rim flange 12 that guides an outer surface of the tire that extends radially outward from the tire axial outer side of the bead seat portion 11 on which the bead bottom surface 4a of the bead portion 4 is seated.

In the sidewall portion 3, sidewall rubbers 10 extending inward and outward in the radial direction from the tire maximum position B are arranged on the axially outer side of the tire structure 9, and by the sidewall rubbers 10 of the tire. The outer wall surface 23 is formed. Sidewall rubber 1
The outer end of 0 is connected to the buttress rubber 24 forming the buttress portion 13, while the inner end thereof is fitted to the bead seat portion 11 and the rim flange 12 of the rim J.
Connect to 5.

The sidewall rubber 10 is made according to JIS
The hardness Y and the rubber thickness X at the tire maximum width position B are expressed in mm.
The value displayed in step 2 is set in the relation of the following formula. Y> (0.149X ² -3.7X + 72.0) The hardness Y of the rubber is set in the range of 50 degrees or more and 65 degrees or less in JIS hardness.

Further, the thickness X of the sidewall rubber at the tire maximum width position B and the separation point D at which the rim flange 12 on the inner side in the radial direction is separated from the outer wall surface 23 of the tire, that is, the outer side in the radial direction of the rim flange 12. Rubber thickness X at end position
The ratio Xf / X with f is set to 1.3 or more and 1.8 or less, and the sidewall rubber thickness X at the tire maximum width position and the inner end of the buttress portion of the tire on the radially outer side thereof. The ratio Xd / X to the goth thickness Xd is 1.0 or more and 1.3 or less, whereby the rubber thickness gradually increases from the tire maximum width position B toward the inner side and the outer side in the radial direction. There is.

If the thickness ratio Xf / X is less than 1.3, the rigidity of the bead portion 4 is inferior, and the bead portion is likely to be stiff. If the thickness ratio Xd / X is less than 1.0, the tread portion warps backward during running. Is easily deformed, rolling resistance is increased, and uneven wear is likely to occur. On the other hand, if the thickness ratio Xf / X exceeds 1.8 or if the thickness ratio Xd / X exceeds 1.3, the weight of the tire increases and the cost increases.

[0027]

[Specific example] Tire size is 215 / 80R16,
The performance of the tire having the configuration shown in FIG. 1 was tested along with the prototypes (Examples 1 to 6) according to the specifications shown in Table 1. In addition, the tires (Comparative Examples 1 and 2) not having the constitution of the present application were also tested to compare the performances.

The test method is as follows. 1) Ride comfort test A test tire was mounted on the fixed shaft of a commercially available bump ride vibration tester, and the load was 1.510 kg, the internal pressure was 7 kg / cm ² , and the speed was 6
The axial load fluctuations when the protrusion was passed over were measured under 0 to 100 km / H, and the results were displayed as an index with Example 4 being 100. The larger the value, the better and the pass level is 95 or more.

2) The test tire was mounted on a steering performance tester, the cornering power was measured under the same load and internal pressure as in 1), and the index was set as 100 in Example 4. The larger the value, the better and the pass level is 95 or more.

3) Road Hazard Property A controlled bad road is provided on the test course, and after running over the bad road 1500 km, the total damage (length × depth) on the tire side is set as 100 in Example 4. It is displayed as an index. The larger the value, the better and the pass level is 95 or more.

4) Tire Weight The weight per tire is shown as an index with Example 4 being 100. The smaller the value, the better, and a value of 110 or less is a passing level. The test results are shown in Table 1.

[0032]

[Table 1]

As a result of the test, it was confirmed that the examples had improved road hazard resistance while maintaining riding comfort and maneuverability.

[0034]

INDUSTRIAL APPLICABILITY As described above, the radial tire for passenger cars of the present invention regulates the correlation between the thickness of the sidewall rubber and the hardness of the rubber at the tire maximum width position, and the upper and lower limits of the hardness of the rubber. The summary is that
As a result, road buzz resistance can be improved and running performance on rough roads can be improved without impairing riding comfort and controllability.

[Brief description of drawings]

FIG. 1 is a right half sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the hardness of sidewall rubber and the thickness of rubber at the tire maximum width position.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 belt layer 9 tire structure 10 sidewall rubber 12 rim flange 13 buttress part B tire maximum width position X, Xd, Xf rubber thickness Y hardness

Claims (1)

[Claims] 1. A cord including a carcass of a radial arrangement in which a tread portion goes from a tread portion to a sidewall portion and is folded back around a bead core of a bead portion, and a belt layer arranged inside the tread portion and radially outside the carcass. A radial tire for a passenger car, comprising a tire structure using the tire structure, wherein a portion of the sidewall portion outside the tire structure is JI.
SA hardness Y is rubber thickness X at the maximum tire width position
(Unit: mm) Satisfies the relationship shown by the following formula, and is made of sidewall rubber having a JIS A hardness of 50 degrees or more and 65 degrees or less, and the side at the tire maximum width position radially inward thereof. The ratio Xf / X of the thickness X of the wall rubber to the thickness Xf of the rubber at the radially outer end position of the rim flange on the inside in the radial direction is 1.3 or more and 1.8 or less, and the tire maximum width position is The ratio Xd / X of the sidewall rubber thickness X at 1.0 to the rubber thickness Xd at the tire radial inner end of the buttress portion of the tire on the radially outer side is 1.0 or more and 1.3. A radial tire for a passenger vehicle, characterized in that the thickness gradually increases from the tire maximum width position to the inside and outside in the radial direction. ^{Y> (0.149X 2 -3.7X + 72.0} )