JPH06106921A - Pneumatic tire - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the appearance of the sidewall from being reduced due to the occurrence of joint dents. An outer surface S of a sidewall portion 4 is divided into fan-shaped regions Y by an imaginary line N extending in a radial direction from a tire axis. The length W of the fan-shaped region Y at the outer peripheral edge e in the radial direction is 10 cm.
Hereinafter, the difference in surface roughness between the adjacent fan-shaped regions Y is 50 μm.
That is all.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of easily suppressing deterioration of the appearance of a sidewall portion due to the occurrence of joint dents or the like.

[0002]

2. Description of the Related Art Radial tires are widely known as tires having excellent high-speed running performance. This product has a highly rigid annular belt on the outside of the crown portion of the carcass, so the tread rigidity is high, and as a result, rolling performance can be improved and the load on the carcass can be reduced, Allows reduction in the number of plies.

However, in such a radial tire, due to the reduction of the number of carcass plies and the angle of the carcass cord, etc., for example, as shown in FIG.
Tend to occur on the outer surface of the sidewall portion, impairing the appearance and reducing the commercial value of the tire.

The joint dent is caused by the superposition (joint) when the carcass ply a is wound in the tire circumferential direction, as shown in FIG. The expansion of the ply a is nonuniformly increased by locally increasing it, and when filled with internal pressure, unevenness marks extending in the radial direction are generated on the outer surface of the sidewall portion having a small rubber outer skin thickness. In particular, the smaller the number of carcass plies, the greater the rate of increase in thickness at the joint A, so the joint dent becomes noticeable, and although it is not a problem for tire performance, it reduces the appearance and reduces the product value, thus reducing the weight of the tire. Particularly harmful to.

[0005]

Therefore, conventionally, in order to suppress the occurrence of such a joint dent, it is necessary to reduce the width of the joint dent portion A or change the cord diameter of the carcass, the number of driving, etc. Is being done,
The results have not been sufficiently satisfactory, and conversely, these internal structural measures lead to the adverse effect of reducing the degree of freedom in design.

An object of the present invention is to provide a pneumatic tire capable of effectively suppressing deterioration of the appearance due to a joint dent or the like without reducing the degree of freedom in design.

[0007]

In order to achieve the above-mentioned object, the pneumatic tire of the present invention is provided with a plurality of circumferentially adjacent surfaces of the sidewall portion by an imaginary line extending in the radial direction from the tire axis. The fan-shaped region is divided into the fan-shaped regions, the circumferential length W of the outer peripheral edge of the sidewall portion is 10 cm or less, and the surface roughness according to JISB0601 at the reference length of 2.5 mm of the fan-shaped regions is determined. And the difference between the surface roughness of the fan-shaped region adjacent to this fan-shaped region and 50 μm or more.

[0008]

In the fan-shaped region in which the outer surface of the sidewall portion is defined, the difference in surface roughness between the adjacent fan-shaped regions is 50 μm.
It is higher than above. Therefore, the boundary line between the fan-shaped regions, that is, the virtual line N extending in the radial direction can be visualized in a distinguishable manner. By making a plurality of virtual lines N appear in this way, the existence of joint dents can be unclear,
The deterioration of the appearance can be effectively suppressed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the figure, a pneumatic tire 1 is located at a tread portion 2 and sidewall portions 4 extending inward in the tire radial direction from both ends of the tread portion 2 and shoulder portions 3, and at each tire radial inner end of each sidewall portion 4. With a bead section 5,
In this example, it is formed as a radial tire for passenger cars.
Further, the pneumatic tire 1 has a ring-shaped bead core 6 in each of the bead portions 5, a carcass 7 is bridged between the bead cores 6, 6, and a tough belt is provided radially outside the carcass 7. The layer 9 is wound with a hoop effect.

In the carcass 7, the carcass cords made of organic fiber cords such as polyester cords are arranged at an angle of 75 to 90 degrees with respect to the tire equator C.
The carcass ply is formed of one sheet, in the present example, both ends thereof are folded back from the inside to the outside around the bead core 6.

Further, the belt layer 9 is formed by arranging belt cords made of, for example, steel at an angle of 10 to 30 degrees with respect to the tire equator C. In this example, it is composed of two belt plies, and each cord of the belt plies is The plies are arranged in opposite directions so that they cross each other.

In the present invention, the outer surface S of the side wall portion 4 is divided into a plurality of fan-shaped regions Y having different surface roughness.

The radial lower edge of the shoulder portion 3 and the radial upper edge of the bead portion 5 have, for example, a V-shaped cross section,
A side line 10 and a rim line 11 each of which is composed of a rib or groove having a U shape and extends continuously in the tire circumferential direction are formed with a small height or a small depth. The sidewall portion 4 is formed between the rim line 11 and the rim line 11. Further, the lower edge of the side line 10 forms a radial outer peripheral edge e of the outer surface S of the sidewall portion.

Here, the fan-shaped area Y is, as shown in FIG.
The outer surface S of the sidewall portion 4 is a plurality of substantially fan-shaped regions defined by an imaginary line N extending in the radial direction from the tire axis and is arranged adjacent to each other in the circumferential direction.

The outer surface of each fan-shaped region Y has substantially the same height, and the circumferential length W of the sidewall portion 4 at the radially outer peripheral edge e is 10 cm or less.

The fan-shaped region Yi has a surface roughness R on the outer surface thereof.
i and the surface roughness Rj, Rk of the left and right fan-shaped regions Yj, Yk adjacent to the fan-shaped region Yi | Ri-Rj |
And | Ri−Rk | are set to 50 μm or more, respectively.

The surface roughness R as used herein is 2.5.
It means a surface roughness based on JIS B0601 at a reference length L of mm.

That is, as shown in FIG. 3, when the outer surface state of the fan-shaped region Y is scanned with the standard length L (= 2.5 mm), the highest peak and the lowest peak among the irregularities within the reference length L are obtained. The difference in height from the valley is defined as Dmax, and the surface roughness R is defined as the average value of each Dmax obtained by 10 arbitrary scans.

The height of the intermediate line M between the highest peak and the lowest valley is called the surface height, and the above-mentioned "each fan-shaped region Y has its outer surface substantially at the same height". This means that the middle lines M of the regions Yi are substantially equal.

Thus, the fan-shaped regions Y adjacent to each other
Difference in surface roughness of i, Yj, and Yk | Ri-Ri |, | Ri
Since −Rk | is set to 50 μm or more, each region can be clearly and visually distinguished. In addition, the boundary lines between the regions Yi and Yj and between Yi and Yk,
That is, the virtual line N can be visualized in a distinguishable manner, and the appearance of the plurality of virtual lines N camouflages uneven marks such as joint dents and suppresses deterioration of appearance.
When the length W is larger than 10 cm, the number of visualized virtual lines N becomes too small, and the uneven marks become conspicuous.
Further, when the difference in surface roughness is less than 50 μm, the visualized virtual line N is blurred such that each region Y is unclear, and the uneven marks are conspicuous.

Such a difference in surface roughness can be easily generated by changing the surface roughness of the vulcanization mold surface without lowering the productivity. Further, since the outer surfaces of the respective fan-shaped regions Y have substantially the same height, it is possible to eliminate the influence on the tire performance such as maintaining the uniformity of sidewall rigidity. Further, as shown in FIG. 2, for example, a display content T capable of representing characters, figures, etc. may be formed on the outer surface S of the sidewall portion 4 by being raised from the outer surface S, for example. May be formed of rubber having a color different from that of the outer surface S, for example, white rubber.

[0022]

As described above, the pneumatic tire of the present invention is
The outer surface of the sidewall portion is divided into a plurality of fan-shaped regions by imaginary lines in the radial direction, and the difference in surface roughness between adjacent regions is set to 50 μm or more, so that the uneven marks generated in the radial direction are effectively camouflaged. It is possible to prevent deterioration of appearance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a side view thereof.

FIG. 3 is a diagram illustrating surface roughness.

FIG. 4 is a side view of the tire for explaining uneven marks.

FIG. 5 is a partial perspective view of a carcass explaining a cause of occurrence of a joint dent.

[Explanation of symbols]

 4 Sidewall part N Virtual line S Outer surface Y, Yi, Yj, Yk Fan-shaped region

Claims (1)

[Claims] 1. An imaginary line extending in a radial direction from a tire axis divides an outer surface of a sidewall portion into a plurality of fan-shaped regions adjacent to each other in a circumferential direction, and the fan-shaped regions are radially outside the sidewall portion. The length W in the circumferential direction at the peripheral edge is 10 cm or less, and the difference between the surface roughness according to JIS B0601 at the reference length of 2.5 mm of the fan-shaped region and the surface roughness of the fan-shaped region adjacent to this fan-shaped region is 50 μm or more. A pneumatic tire characterized by