JPH0431105A - Pneumatic radial tire for heavy loading - Google Patents

Abstract

PURPOSE:To improve both unbalanced wear resistance at the shoulder section and wandering performance simultaneously by specifying a ratio of the tire cross sectional height to the maximum width of a tire, the tilt angle of a buttress at the outer surface of the tire and the height from a base point at the end of a tread to the inside end of the aforesaid tilted surface in the radial direction. CONSTITUTION:In the cross sectional outer wheel profile of a tire A, a ratio H/S of the tire cross sectional height H to the maximum width S of the tire when the tire A is assembled with a rim with inner pressure built up, shall be set at one equal to or more than 0.9. And the outer surface of a buttress 3 is formed in a linear slant surface tilted to a straight line (1) representing the extension of the outer surface of a tread 1, and the tilt angle alpha of the surface shall be set at a range of 45 deg. to 60 deg.. In addition, the height (h) from the intersection of the straight line (1) which is in the extension of the outer surface of the tread 1, with a straight line (m) which is in the extension of the outer surface of the buttress 3, that is, the height from a base point P at the end of the tread, to the inside end Q of the linear tilted surface of the buttress 3 shall be set at 5 to 10% of the height H of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a heavy-load pneumatic radial tire that effectively prevents shoulder wear of the tire and improves wandering performance.

(Prior art) Heavy-duty radial tires withstand the loads of the vehicle body and cargo,
In particular, various improvements have been made to the outer contour shape of the shoulder in order to reduce wear due to friction with the road surface and improve wandering performance.

FIGS. 2 to 4 show the outer contour shape of a part of the shoulder of a conventionally known heavy-duty vehicle/altire.

The outer contour of the tire A includes a tread part 101 which is a ground contact part, a shoulder part 102 which bends following both ends of the tread part, a buttress 103 which extends approximately radially inward from both ends of the tread part 101, and a sidewall part 104 which follows this. Fig. 2 shows a so-called round shoulder type, in which the shoulder part 102 has a rounded shape, and Fig. 3 shows a so-called square shoulder type, in which the shoulder part 102 has a rounded shape.
02 has an angular shape.

Also, although Figure 4 has square shoulders,
A large number of sipes 105 are carved in the tire radial direction from the shoulder portion 102 to the buttress 103.

(Problems to be Solved by the Invention) The problems with radial tires for heavy loads include preventing the occurrence of uneven wear, including drop wear on a part of the shoulder of the tire, and preventing the vehicle from shaking when driving on a rutted road surface. ,
Two points are to be raised: prevention of the so-called wandering phenomenon, and a major challenge is to simultaneously improve partial shoulder wear and wandering performance.

However, among the conventional technologies, although the round shoulder shape tire shown in Figure 2 has excellent wandering performance, it has the disadvantage that uneven wear tends to occur in the shoulder part, and the tire with the round shoulder shape shown in Figure 3 Tires having a square shoulder shape have a problem of poor wandering performance, although uneven wear on the shoulders is less likely to occur.

On the other hand, the tire with the sipes shown in Figure 4 was designed to improve both uneven shoulder wear and wandering performance, but neither performance reached a practically satisfactory level, resulting in problems. was left behind.

An object of the present invention is to provide a pneumatic radial tire for heavy loads in which partial shoulder wear and wandering performance are simultaneously improved.

[Structure of the invention]

(Means for Solving the Problems) The heavy-duty pneumatic radial tire of the present invention includes a toroidal carcass consisting of at least one layer in which reinforcing cords are arranged substantially in the radial direction, A non-stretchable belt layer, an outer surface formed by a radius of curvature with the center of the radius of curvature on the rotating shaft side on the cross section, and a tread having a rounded shape at both ends are sequentially provided. In a tire including a buttress extending inward, when the tire is assembled on a working rim and filled with working internal pressure, the ratio of the tire cross-sectional height H to the tire maximum width S is 0.9 or more, and the outer surface of the buttress is a tread. A straight line e that is an extension of the outer surface contour of
It forms a linear inclined surface inclined at an inclination angle a of 45° to 60° relative to It is characterized by being within a range of 5 to 10%.

(Function) Since the tire of the present invention has a tread rounded at both ends and has a shape similar to a conventional round shoulder, the occurrence of wandering is prevented.

In addition, because the buttress has a linear slope and the vertical height of the buttress is set within a certain range with respect to the tire height, there is less wear on the shoulder part, and it is also advantageous in preventing wandering. to prevent.

Furthermore, regulating the angle of inclination of the buttress within a specific range also contributes to uneven shoulder wear and improvement in wandering performance.

(Example) FIG. 1 shows an example of the present invention, and shows the outer contour shape of a tire in cross section.

The crown portion of the tire A includes a toroidal carcass consisting of at least one layer in which reinforcing cords (not shown) are arranged substantially in the radial direction, and a non-stretchable heald layer (7) outside the crown portion of the carcass in the radial direction (not shown). have.

The tread portion] is curved with a radius of curvature R1 on the rotating shaft side, shoulder portions 2 at both ends thereof are curved in the same direction with a radius of curvature R2, and the buttress 3 following this is curved in a linear slope. The cross-sectional outer contour shape of the tire A is formed by forming a surface and further curving the sidewall 4 continuously from this surface.

Here, when the present tire A is mounted on a rim (not shown) and filled with internal pressure, the ratio H/S of the tire cross-sectional height H to the tire maximum width S must be 0.9 or more. If this H/S is smaller than 0.9, the cross section of the tire will become flat, and the inclination angle α will be more likely to be set to 60° or less.
It is mild against the occurrence of wandering.

In addition, the outer surface of the buttress 3 forms a linear inclined surface that is inclined at an inclination angle α with respect to the straight line g that is an extension of the outer surface of the tread 1, and the inclination angle α must be in the range of 45° to 60°. It is. In this type of tire, this inclination angle α is 4
If it is less than 5", the weight of the tire will increase, making it impossible to reduce the weight and increasing manufacturing costs. Also, if the inclination angle α is 60°
If it exceeds this, uneven wear on a part of the shoulder is likely to occur.

On the other hand, from the intersection point of the straight line 2 extending the outer surface of the tread 1 and the straight line m extending the outer surface of the buttress 3, that is, from the base point P of the tread end to the radially inner end Q of the linear inclined surface of the buttress 3. The height h is set to 5 to 10% of the tire height H. If this value is less than 5%, the effect of preventing uneven shoulder wear will be small, and if it exceeds 10%, it will be difficult to reduce the angle of inclination α to 60° or less. In this case, the shoulder volume increases and the weight increases, making it impossible to reduce weight and increasing manufacturing costs.

(Experimental Example) A heavy-duty radial tire having the cross-sectional outer contour shape shown in FIG. 1 was manufactured and tested on an actual vehicle running 10,000 km to evaluate partial shoulder wear and wandering performance.

The tire specifications were selected as follows.

Tire size near, 00R1610PR230G Tire cross-section aspect ratio H/S-0.95 Tread width TW-
138. Table 1 shows the results obtained by varying the radius of curvature R+, -300, R2-height h, and angle of inclination α.

Table 1 O4 Occurrence △ - Slight occurrence, but at an acceptable level has advantages.

(1) The outer surface of the buntress forms a linear inclined surface inclined at an angle of 45° to 60° with respect to the straight line g that is an extension of the outer surface contour of the tread, and the base point P of the tread edge
Since the height h from to the radially inner end of the straight sloped surface is within the range of 5 to 10% of the tire cross-sectional height H,
The occurrence of uneven wear on a portion of the shoulder can be suppressed, and the occurrence of wandering can be prevented.

(2) It has excellent wandering performance because it is partially covered.

(3) Since the ratio of the tire cross-sectional height H to the tire maximum width S is 09 or more, is wonder link likely to occur?
This holeless shape suppresses this.

[Brief explanation of the drawing]

Examples of cross-sectional outer contour shapes are shown; FIG. 2 is a diagram with a round shoulder, FIG. 3 is a diagram with a square shoulder, and FIG. 4 is a diagram with a sipe. 1... Tread portion 2... Shoulder part 3... Buttress 4... Sidewall A... Tire S... Tire maximum width H... Tire section height α... Inclination angle P...・Tread end base point

Claims (1)

[Scope of Claims] A toroidal carcass consisting of at least one layer in which reinforcing cords are arranged in a substantially radial direction, a non-stretchable belt layer on the radially outer side of the crown portion of the carcass, and a non-stretchable belt layer on the side of the rotating shaft in the cross section. In a tire that sequentially has an outer surface formed by a radius of curvature with a center of the radius of curvature and a tread having a rounded shape at both ends, the tire includes buttresses extending generally radially inward from both ends of the tread. The ratio of the tire cross-sectional height H to the tire maximum width S when assembled and filled with the internal pressure for use is 0.9 or more, and the outer surface of the buttress is 45° to 60° with respect to a straight line extending the outer surface contour of the tread. It forms a linear inclined surface inclined at an inclination angle α of °, and the height h from the base point P of the tread end to the radially inner end of the linear inclined surface is 5 to 10% of the tire cross-sectional height H.
A heavy-duty pneumatic radial tire characterized by being within the range of .