JPH0459401A - Flat pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To enhance wear resistance against shoulder abrasion in a flat pneumatic tire for heavy load having a specified aspect ratio by composing its tread shape so that it is formed of single radius in the normal state, and forms double radius composed of tread radii between which specified relation is realized when filled with specified internal pressure. CONSTITUTION:In a pneumatic radial tire whose aspect ratio is less than 90%, the shape of a tread part 1 when it is mounted to a regular rim and filled with normal internal pressure is formed with single tread radius R. And, the tread shape when 10% filling out of normal internal pressure is performed is constructed so as to form double radius composed of a tread radius Rc with which relation of 0.50R<=Rc<=0.90R is realized from the tread center CL up to a point P that stands off 0.60+ or -0.15 times of tread half width TDW/2, and a tread radius Rs with which Rs>=1.2R is realized from the point P up to both shoulder parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flat pneumatic radial tire for heavy loads that has improved shoulder drop wear resistance without impairing handling stability.

[Prior Art] Generally, heavy-duty flat radial tires are molded to have a tread shape with a single tread radius R0, as shown by the dotted line in Figure 3. When installed on the regular rim and filled with the regular internal pressure (hereinafter referred to as regular internal pressure filling), as shown by the solid line in Figure 3, the distance from the tread center CL in the tread width direction is approximately 0.6 times the tread half width TDW/2. distant point P
The vicinity bulges radially outward.

This phenomenon is especially true for tires with a small aspect ratio ((tire section height/maximum tire section width)
0% or less), it is noticeable, and the smaller the oblateness is, the more noticeable it is. Therefore, the tread radius Rc of the tread center portion between the point P and the tread radius Rs of both shoulder portions form a tread shape defined by two tread radii of different sizes.Such a tread shape However, when running on a road surface, drag occurs between the tread center portion and the shoulder portion due to the difference in radius from the axle, which has the disadvantage of accelerating the wear of the shoulder portion and making shoulder drop wear more likely.

Here, the position of the above-mentioned point P is generally 0 of the tread soil TDK/2 in the tread width direction from the tread center CL.
．． This occurs at a position 60 times farther away, but this position is due to the difference in tire size and aspect ratio.
It fluctuates within a range of ±0.15 times 2.

In addition, in order to prevent the above-mentioned shoulder drop wear, various studies have been conducted to change the tread shape in the mold of a heavy-duty flat radial tire so that the tread shape after filling with the regular internal pressure becomes a single radius. It has been found that tire performance such as steering stability is impaired when this is carried out.

The present invention aims to provide a tire that does not impair tire performance such as steering stability by regulating the tread radius in the mold within a specific range in relation to the tire tread radius after filling the regular internal pressure with the above change. be.

[Problems to be Solved by the Invention] That is, an object of the present invention is to provide a flat radial tire for heavy loads that has improved shoulder drop wear resistance without impairing tire performance such as steering stability.

[Means to solve the problem]

An object of the present invention is to provide a pneumatic radial tire with an aspect ratio of 90% or less, in which the tread shape when mounted on a regular rim and filled with a regular internal pressure is formed by a single tread radius R, and which is 10% of the regular internal pressure. The tread shape at the time of filling is from the tread center to the tread soil (0.60±0.
15) It is formed from a double radius of the tread radius Rc of the tread center portion up to a point P which is twice as far apart from the tread radius, and the tread radius Rs of both shoulder portions from the point P to the shoulder ends, and 0.50R≦Rc≦0. 90
This can be achieved by setting R, Rs≧1.2R.

In the present invention, the tread shape when filled to 10% of the normal internal pressure means that there is no substantial inflation and the shape corresponds to the mold shape.

In this way, the tread shape when filled with the normal internal pressure of 10χ is a double radius, but by forming a single tread radius by filling with the normal internal pressure, the tire performance such as steering stability can be improved. Shoulder wear resistance can be improved.

In the present invention, the regular rim and regular internal pressure refer to the regular rim and regular internal pressure specified in the Japan Automobile Tire Association Standards (JATMA).

A detailed description will be given below with reference to the drawings.

FIG. 2 shows an example of the heavy-duty flat radial tire of the present invention, which has a pair of sidewall portions 2 on both left and right sides of a tread 1, and has a pair of sidewall portions 2 on the inside thereof at substantially 90° with respect to the tire circumferential direction. having a carcass layer 3 arranged at a cord angle;
A belt layer 4 extending in the circumferential direction of the tire is provided in a portion of the carcass layer 3 corresponding to the tread 1.

In such a structure, the tread shape is formed by a single tread radius R when normal internal pressure is filled, as shown in FIG. However, the tread shape when filled with a normal internal pressure of 10χ, which corresponds to the mold shape, is a tread between points P on the left and right sides specified by a point P that is (0,60±0.15) times apart from the tread center in the tread soil. The tread radius Rc of the center portion and the tread radius Rs of both shoulder portions from the point P to the shoulder end are formed from a double radius having different sizes. Moreover, the tread radius R of the tread center section
c satisfies the relationship 0.50R≦Rc≦0.9OR,
Tread radius Rs of both shoulder areas is Rs≧1.2
It is designed to satisfy the relationship R. Here, Rs is allowed to be infinite, that is, until the tread shape of the shoulder portion becomes a straight line. Two tread radii Rc specify the tread shape when filled with 10χ of normal internal pressure.

By satisfying such a relationship, when Rs is filled with normal internal pressure and inflated, the vicinity of point P will not bulge out, or conversely be depressed, as shown by the solid line in Figure 1. To provide a heavy-duty flat pneumatic tire that can prevent shoulder drop wear without impairing tire performance such as steering stability.

〔Example〕

Example, Conventional Example, Comparative Example Tires having the structure shown in Figure 2 with all specifications the same except for the tread radius shown in the table were manufactured, and tires were mounted on regular rims (22.5 x 8.25). Mounted and filled with the standard internal pressure (8,00 Kg/cm"), the following steering stability and shoulder drop wear resistance were evaluated. The table shows the evaluation results using an index with the value of the conventional tire as 100. Indicated.

In addition, the positions of the points P where the tread radius changes in the example tire and the comparative example tire are all at the trend center C.
From L to tread width direction, TDW/2 of 0.
The positions were 60 mm apart.

Moreover, these tire sizes were all the same, 11/70 R22.5.

Maneuvering stability: Load 2725Kg, slip angle 1 on indoor flat plate tester
The cornering force was evaluated when the vehicle was rotated.

The measurement results are expressed as an index, with the measurement value of the conventional example tire set as 100. The larger this index value is, the better the steering stability is.

Resistance to wear and tear: Evaluation was made by measuring the amount of wear on the shoulder portion of a tire after driving an actual vehicle for 10,000 km on a 100x paved road with a load of 2,725 kg per tire.

The measurement results are expressed as an index, with the measurement value of the conventional example tire set as 100. The larger this index value is, the better the shoulder drop wear resistance is.

(Below this page, margins) As can be seen from the table above, Example Tires I and II.

Comparing with Comparative Tires I and It, tires (2) and (2) are superior in handling stability and shoulder drop wear resistance.

〔Effect of the invention〕

As explained above, according to the present invention, the normal internal pressure is 10
The tread shape at the time of % filling is determined by the tread radius Rc of the tread center part from the tread center to a point P that is (0,60±0.15) times farther away from the tread hand, and the tread radius Rc of the tread center part from the point P to the shoulder end. It is formed with a double radius with the tread radius Rs, and the relationship with the tread radius R at the time of normal internal pressure filling is 0.50R.
Since ≦Rc≦0.90R and Rs≧1.2R are set, the tread shape at the time of normal internal pressure filling can be formed with a single tread radius R, which improves tire performance such as handling stability. Shoulder wear resistance can be improved without impairing the wear resistance.

[Brief explanation of the drawing]

Fig. 1 is a half-sectional view showing an example of the tread radius of the tire of the present invention, Fig. 2 is a partial sectional view showing an example of the tire of the present invention, and Fig. 3 is a half-sectional view showing the tread radius of a conventional tire. be. 1...Tread part, 2...Side wall part, 3...
...Carcass layer, R, Rc, Rs...Tread radius.

Claims (1)

[Claims] In pneumatic radial tires with an aspect ratio of 90% or less,
The tread shape when installed on a regular rim and filled with the regular internal pressure is formed by a single tread radius R, and the tread shape when filled to 10% of the regular internal pressure is half the tread width from the tread center (0.60±0. 15) It is formed from a double radius of the tread radius Rc of the tread center portion up to a point P which is twice as far apart from the tread radius, and the tread radius Rs of both shoulder portions from the point P to the shoulder ends, and 0.50R≦Rc≦0. 90R, Rs≧1.2R
A flat pneumatic radial tire for heavy loads.