JPH1120417A - Radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the road noise while ensuring the steering stability by optimizing the tire side form, and optimizing the physical property and arrangement of a side wall rubber. SOLUTION: When an internal pressure of 10% of the maximum internal pressure determined by JATMA specification is filled in this tire, the carcass line has a form shown by the solid line, wherein denoted at F is the intersection of the carcass line to the straight line passing the central point O of a rim flange circular part and extending at an inclination of 45 deg. to the rotating axis of the tire, and T is the intersection of the carcass line to the straight line extended from the intersection F vertically to the tire axial line. A side wall rubber 3 is formed of a rubber annular part 3-2 having a small storage elasticity and a rubber annular part 3-1 having a large storage elasticity, and the rubber annular part 3-1 having the large storage elasticity is arranged in an area as includes a tire maximum width position S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire in which road noise is reduced while ensuring fuel efficiency and steering stability.

Here, the term used in the present specification will be described. The "section height SH of the tire" indicates a half of the difference between the outer diameter OD of the tire and the rim diameter RD. The “storage modulus” is a physical property value of rubber described in JIS K 6394, and is a quotient obtained by dividing the amplitude of a component having the same phase as the strain of stress by the deflection amplitude. In the present invention, the measurement is performed under a tensile condition of 50 Hz and a dynamic strain of 1%.

[0003]

2. Description of the Related Art Due to the recent trend of luxury and quiet automobiles,
Tire performance is increasingly required to reduce road noise and improve ride comfort. Road noise is noise generated when traveling on rough asphalt paved roads, etc., and the frequency at which the tire picks up the roughness of the road surface and the tire vibrates correspondingly and is transmitted to the vehicle interior through the vehicle body is approximately equal to the frequency. Very harsh noise at 100-400 Hz.
Conventionally, such measures are generally taken by increasing the volume of rubber in the tread portion or changing the material of the tire to lower the spring constant of the tire. However, an increase in the volume of the tread deteriorates the fuel efficiency, and a reduction in the spring constant leads to a decrease in steering stability, and it has been difficult to achieve a reduction in road noise, fuel efficiency, and steering stability at the same time.

Accordingly, the inventor of the present invention has disclosed Japanese Patent Application No.
The radial tire having at least one radial carcass and a side rubber on the outside of the carcass in the axial direction is assembled on a standard applicable rim, and the internal pressure of 10% of the air pressure corresponding to the maximum load capacity specified in the JATMA standard is adjusted. At the time of filling, an intersection where a straight line passing through the center point O of the rim flange arc portion and extending at an inclination angle of 45 degrees with respect to the tire rotation axis intersects the carcass line is defined as F, and the intersection is set perpendicularly to the tire axis from the intersection F. The intersection point where the straight line intersects the carcass line is defined as T, and it is imagined that it circumscribes the tangent line GH of the carcass line drawn parallel to the line segment FT connecting the intersection points F and T outside in the tire axial direction. When an arc having the line segment FT as a chord is Rk, the carcass line from the maximum width portion S of the carcass to the intersection T passes outside the tire from the arc Rk. At least a part of the carcass line from the maximum width portion S of the carcass to the intersection F passes outside the tire from the arc Rk, and the carcass line from the maximum width portion S of the carcass to the intersection T is , The arc Rk
A radial tire having a maximum separation distance t from the arc Rk of 2 to 15 mm which passes through the outside of the tire. However, although the tire proposed in Japanese Patent Application No. 7-262728 improves road noise performance and ride comfort, there is a problem that steering stability is inferior to a conventional tire-shaped tire.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to reduce road noise while ensuring steering stability by optimizing the tire side shape and optimizing the physical properties and arrangement of the tire sidewall rubber in a radial tire. It is to provide a reduced radial tire.

[0006]

The present invention adopts the following constitution to achieve the above object. That is,
A radial tire having at least one radial carcass and a side rubber on the outside in the axial direction of the carcass,
When assembled to the standard applicable rim and filled with an internal pressure of 10% of the air pressure corresponding to the maximum load capacity, a straight line that passes through the center point O of the rim flange arc portion and extends at an inclination angle of 45 degrees with respect to the tire rotation axis is formed by the carcass Let F be the intersection that crosses the line, and let T be the intersection that intersects the carcass line with a straight line that is perpendicular to the tire axis from the intersection F, and is located outward in the tire axial direction with respect to a line FT connecting the intersections F and T. If a circular arc having the line segment FT imaginary so as to circumscribe the tangent GH of the carcass line drawn in parallel as a chord is Rk, the carcass line from the maximum width portion S of the carcass to the intersection T is Passes through the outside of the tire from the arc Rk, and at least a part of the carcass line from the maximum width portion S of the carcass to the intersection F passes outside the tire from the arc Rk, and The carcass line from the width portion S to intersection point T passes through the outer tire than arcuate Rk,
In a radial tire having a maximum separation distance t from the arc Rk of 2 to 15 mm, the sidewall rubber has a rubber annular portion having a small storage elastic modulus and 140% of a storage elastic modulus of the rubber annular portion having a small storage elastic modulus. The above-mentioned configuration is adopted which comprises a rubber annular portion having a large storage elastic modulus.

In particular, in claim 2, a rubber having a large storage elastic modulus is applied to a region having a tire cross-section height SH of 15% or more, preferably 1%, in the tire radial direction with the tire maximum width position substantially at the center.
By arranging in the range of 5 to 55%, steering stability can be improved without lowering road noise performance.
Here, the upper limit of 55% is preferably 55%.
This is because the effect of preventing the generation of road noise is reduced.

According to a third aspect of the present invention, as a method for securing the steering stability even if the road noise performance is reduced to some extent, a rubber having a large storage elastic modulus of 6.5 MPa or more is adopted for the entire sidewall. I have.

The reason for setting the ratio of the storage elastic modulus of the rubber having a large storage elastic modulus to that of the rubber rubber having a small storage elastic modulus to be 140% or more is that if it is 140% or less, the effect of improving the steering stability is small. , The upper limit is substantially 300%. The absolute value of the storage elastic modulus of the rubber having a large storage elastic modulus is preferably 5.5 MPa or more.

[0010] Road noise is noise generated when traveling on a rough asphalt pavement or the like.
The tread portion of the tire picks up the roughness of the road surface and vibrates, which is transmitted to the sidewall portion, further transmitted to the bead portion, the rim, and transmitted to the vehicle interior through the vehicle body, with a very harsh frequency of about 100 to 400 Hz. Noise. Therefore, it is particularly necessary to reduce the vertical spring constant as a technique for improving the tire. In order to achieve this in the form of a tire, the present invention has conducted various studies and has obtained the following findings. (1) Regardless of the mold shape, the tire carcass takes a shape that attempts to keep the cord tension of the carcass constant when air is filled up to the use internal pressure. In particular, it is remarkable in the central part of the side wall where the bending rigidity is small and can be regarded as a film body. Changes to When the mold is designed in such a manner that the cord tension of the carcass is made to be constant, it is called a tire design based on a natural shape theory. This generally takes a shape relatively close to the arc Rk in FIG.

(2) When the tire is deformed by the protrusion,
The deflection of the carcass is large at the center of the sidewall having low bending rigidity, small near the shoulder portion having high bending rigidity, and particularly small near the bead portion.

(3) Therefore, if the mold shapes near the shoulder portion and the bead portion are preliminarily set to a shape close to the state where the tire is bent (outside the tire from the arc Rk in FIG. 1), the spring constant can be reduced. You can do it.

That is, when air is filled up to the working internal pressure in such a mold shape, the carcass tries to keep the cord tension constant, and as shown in FIG. 3, the shoulder portion and the bead portion enter the inside of the tire. The central part of the sidewall goes outside the tire. However, since the vicinity of the shoulder portion and the vicinity of the bead portion are made of an elastic body, if the air pressure is set to about 10% or less of the air pressure corresponding to the maximum load capacity, the shape returns to a shape close to the mold shape. In other words, at the time of use air pressure filling, the force near the shoulder portion and the vicinity of the bead portion are constantly acting to return the tire to the bent state, and when the carcass of the tire is bent, the tire is easily bent, and eventually the spring is bent. That is, the constant is reduced. Such an effect cannot be expected with the conventional tires shown in FIGS.

Here, the reason why the separation distance t from the arc Rk in FIG. 1 is set to 2 to 15 mm is that the effect cannot be expected much when the distance is 2 mm or less, and the reason why the distance t is set to 15 mm or less depends on the tire size. Such a carcass line cannot be drawn realistically.

Further, at least a part of the carcass line from the maximum width portion S of the carcass to the intersection F passes outside the tire rather than the arc Rk, as shown in FIG. There is a big feature compared to the fact that the tire passes considerably inside the tire. Care must be taken to draw a smooth carcass line only at the point where the bead inflection point connects to the bead core.

However, when the above-described carcass line is adopted and rubber commonly used for radial tires for passenger cars, that is, rubber having a relatively low storage modulus is used as the sidewall rubber member, the steering stability is reduced. Was found to decrease. The inventor has been diligently developing the steering stability of the tire described above. (1) The change in the rubber properties of the sidewall portion has a small contribution to road noise. (2) On the other hand, the influence of the rubber physical properties of the sidewall portion on the steering stability is large, and if a rubber having a large storage elastic modulus is arranged, the steering stability is improved.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a tire according to an embodiment of the present invention and pneumatic radials according to a conventional example and a comparative example will be described. In each case, the tire size is 195 / 65R14. FIG. 1 shows a carcass shape when a tire according to the present invention and a tire of a comparative example are assembled on a standard applicable rim and an internal pressure of 10% of a maximum internal pressure is filled. FIG. 2 shows a carcass shape when a conventional tire is assembled on a standard applicable rim and filled with an internal pressure of 10% of the air pressure corresponding to the maximum load capacity. The tire according to the embodiment of the present invention is a radial tire having a radial carcass 1 made of a single layer of polyester cord and a sidewall rubber 3 on the outside of the carcass 1 in the axial direction, assembled on a standard applicable rim, and specified in JATMA standard. When an internal pressure of 10% of the maximum internal pressure is filled, an intersection where a straight line passing through the center point O of the rim flange arc portion and extending at an inclination angle of 45 degrees with respect to the tire rotation axis crosses the carcass line is defined as F. Let T be the point of intersection at which the straight line perpendicular to the axis crosses the carcass line,
When a circular arc having a chord of the line segment FT imagined to circumscribe a tangent line GH of the carcass line drawn parallel to the line segment FT connecting the T outside the tire axial direction is denoted by Rk. The carcass line from the large portion S to the intersection T passes outside the tire from the arc Rk, and the carcass 1
At least a portion of the carcass line from the maximum width portion S of the carcass to the intersection F passes outside the tire beyond the arc Rk, and the carcass line from the maximum width portion S of the carcass 1 to the intersection T is This is a radial tire that passes outside the tire than Rk and has a maximum separation distance t of 4 mm from the arc Rk. As shown in FIG. 5, the side wall rubber 3 includes a rubber ring portion 3-2 having a small storage modulus and a rubber ring portion 3-1 having a large storage modulus. The rubber annular portion 3-1 having a large storage elastic modulus is arranged in a region including the tire maximum width position S. The tire of Example 5 is the same as the tires of Examples 1 to 4, except that the entire sidewall rubber is made of rubber having a storage modulus of 6.5 MPa. Examples 6 to 11
Is an example of a tire made of rubber having a storage modulus of 5.5 MPa. Conventional tires are
The tire has the carcass line shown in FIG. 2 and the entire sidewall is made of rubber having a storage elastic modulus as small as 3.90 MPa. The tire of Comparative Example 1 has a carcass line shown in FIG. 1 and the entire sidewall has a storage elastic modulus of 3.
It is a tire made of rubber as small as 90 MPa. The tire of Comparative Example 2 is a tire in which the rubber annular portion 3-1 of the tire of Example 1 is replaced with rubber having a storage elastic modulus of 5.0 MPa. Table 1 shows the specifications of these tires.

Next, in order to confirm the effect of the tire of the present invention, a comparative test of road noise and a comparative test of riding comfort and steering stability by an actual vehicle were performed on the above-described tire. The test conditions were as follows: Tire size 195 / 65R14 was assembled on a 6JJ rim at an internal pressure of 200 kPa, and was manufactured in Japan.
The test was performed using a 0 cc passenger car. Road noise is measured at 50 km / h / h, and ride comfort and driving stability are measured by a sensory test conducted by a driver on a comprehensive test road. The value is 1 for a conventional tire.
The index is displayed as 00, and the larger the value, the better the performance.
The results are as shown in Table 1.

[0019]

[Table 1]

As apparent from the above, the pneumatic radial tire of the present invention has a frequency of 100 to 200 Hz, which is a frequency at which tire road noise becomes a problem, as compared with the conventional tire.
It can be seen that the sound pressure level at 300 to 400 Hz has been improved, the riding comfort has been improved, and the steering stability is substantially the same as that of the conventional tire.

[0021]

As is apparent from the above description, according to the present invention, a radial tire with reduced road noise and excellent ride comfort can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional profile of a carcass line at 10% of air pressure corresponding to the load capacity of a tire of the present invention;
It is shown in comparison with the reference arc Rk.

FIG. 2 is a cross-sectional profile of a carcass line at 10% of air pressure corresponding to the load capacity of a conventional tire;
It is shown in comparison with the reference arc Rk.

FIG. 3 is a comparison diagram of cross-sectional profiles at 10% and 100% of air pressure corresponding to the load capacity of the tire of the present invention.

FIG. 4 is a comparison diagram of cross-sectional profiles at 10% and 100% of air pressure corresponding to the load capacity of a conventional tire.

FIG. 5 is a half sectional view in the tire width direction showing an example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Carcass 2 Rim 3 Sidewall rubber 3-1 Rubber ring part with large storage elasticity 3-2 Rubber ring part with small storage elasticity 4 Ring part made of rubber with large storage elasticity O Center of rim flange arc part Point S Tire maximum width part SH Tire section height F Intersection point where a straight line passing through the center point O and extending at an inclination angle of 45 degrees with respect to the tire rotation axis crosses the carcass line 1 T A straight line drawn from the intersection F to the tire axis is the carcass line 1 Intersection B crossing the bead base part position

Claims (3)

[Claims] 1. A radial tire having at least one radial carcass and a sidewall rubber on the outside in the axial direction of the carcass is assembled on a standard applicable rim, and JAT is provided.
Air pressure of 10 corresponding to the maximum load capacity specified in the MA standard
% When the internal pressure is filled, a straight line passing through the center point O of the rim flange arc portion and extending at an inclination angle of 45 degrees with respect to the tire rotation axis crosses the carcass line as F,
The intersection point where a straight line perpendicular to the tire axis from the intersection point F intersects the carcass line is defined as T, and the carcass line drawn parallel to the line segment FT connecting the intersection points F and T outside in the tire axial direction. Assuming that an arc having a chord at the line segment FT imagined to circumscribe the line tangent GH is Rk, the carcass line from the maximum width S of the carcass to the intersection T is
At least a portion of the carcass line from the maximum width S of the carcass to the intersection F passes outside the tire from the arc Rk, and at least a part of the carcass line passes outside the tire from the arc Rk to the maximum width of the carcass. In the radial tire in which the carcass line from S to the intersection point T passes outside the tire from the arc Rk and has a maximum separation distance t from the arc Rk of 2 to 15 mm, the sidewall rubber has a storage modulus of elasticity. And a storage elastic modulus of the rubber annular portion having a small storage elastic modulus.
A radial tire comprising a rubber annular portion having a large storage elastic modulus of 40% or more. 2. The radial tire according to claim 1, wherein the rubber annular portion having a large storage elastic modulus is arranged in an area of 15% or more of a sectional height SH in a tire radial direction. 3. A radial tire having at least one radial carcass and a sidewall rubber on the outside in the axial direction of the carcass is assembled on a standard applicable rim, and JAT is provided.
Air pressure of 10 corresponding to the maximum load capacity specified in the MA standard
% When the internal pressure is filled, a straight line passing through the center point O of the rim flange arc portion and extending at an inclination angle of 45 degrees with respect to the tire rotation axis crosses the carcass line as F,
The intersection point where a straight line perpendicular to the tire axis from the intersection point F intersects the carcass line is defined as T, and the carcass line drawn parallel to the line segment FT connecting the intersection points F and T outside in the tire axial direction. Assuming that an arc having a chord at the line segment FT imagined to circumscribe the line tangent GH is Rk, the carcass line from the maximum width S of the carcass to the intersection T is
At least a portion of the carcass line from the maximum width S of the carcass to the intersection F passes outside the tire from the arc Rk, and at least a part of the carcass line passes outside the tire from the arc Rk to the maximum width of the carcass. In a radial tire in which the carcass line from S to the intersection T passes outside the tire from the arc Rk and has a maximum separation distance t from the arc Rk of 2 to 15 mm, the storage elastic modulus of the sidewall rubber Is 6.5 MPa or more.