JPH05319028A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To suppress an irregular unbalanced abrasion by making the groove width of a small groove continued in the tire circumferential direction provided at the shoulder side edge of a rib neighboring the inner side of the outermost main groove, in a specific size, and making the largest size of the small rib partitioned to the left side and the right side by the small groove to the whole width of the rib at the inner side of the outermost main groove, in a specific size. CONSTITUTION:To the shoulder side edge of a rib 4 neighboring the inner side of the outermost main groove 2b, a small groove 4a continued in the tire circumferential direction is provided, and while the width W of the small groove 4a is made within 0.5 to 1mm, the depth direction of the groove is inclined to the tire to the normal line of a tread surface. And a rib main body 4c and a small rib 4b of the same height partitioned by a small groove 4b are formed, the main groove 2b side of the small groove 4b is made in a zigzag form, and the largest width W2 of the small groove 4b to the whole width W1 of the rib 4 is set as the size W2/W1<=0.3. Consequently, an unbalanced abrasion such as a shoulder part abrasion can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic radial tire based on a rib pattern used for trucks, buses and the like, and more particularly to a heavy-duty pneumatic radial tire suitable for front wheels with suppressed uneven wear.

[0002]

2. Description of the Related Art A rib pattern is inferior in drivability to a block pattern but is superior in wear resistance, so that it is often used as a tread pattern for radial tires for front wheels (steering wheels) of heavy-duty vehicles such as trucks and buses. It is used. In recent years, softening of the suspension has progressed to improve the riding comfort of trucks and buses, and along with this, uneven wear such as shoulder drop wear, rib punch, corrugated wear, and polygonal wear occurs on the tread surface of the front wheel radial tire. It's easier to do.

Conventionally, as a measure against uneven wear, Japanese Patent Laid-Open No. 63-1
As disclosed in Japanese Patent No. 34313, a shoulder rib is provided with a fine groove on an outer edge thereof, and JP-A-61-23
A shoulder rib having a notch as described in JP-A-5205, or JP-A-62-9130.
As described in Japanese Patent Publication No. 3, a tread radius is proposed to be changed.

[0004]

However, since the above technique is insufficient in the effect of suppressing uneven wear, various uneven wear is likely to occur on the tread surface when the alignment of the vehicle is not good. It was often impossible to run until the final life of the tire. Therefore, the present inventors have conducted various analyzes on tires having uneven wear, and have found that the structure of the radial tire has a great influence on the occurrence of uneven wear. That is,
In pneumatic radial tires for heavy loads, the belt layer has
Since four steel belts are arranged and the rigidity of the belt layer is very high, when the tire with the tread pattern ribbed as described above is filled with air and inflated, it is especially the outermost. The main groove part becomes an inflection point and the shoulder part falls off. When the shoulder part falls off in this way, the difference in diameter between the center part and the shoulder part of the tread becomes large, and drag frictional force due to the difference in diameter acts strongly on the shoulder part, so that only the shoulder rib wears quickly and irregularly. Uneven wear is likely to occur. An object of the present invention is to provide a heavy-duty pneumatic radial tire that can effectively suppress irregular uneven wear in which only the shoulder ribs wear quickly.

[0005]

A pneumatic radial tire for heavy loads according to the present invention has a steel belt layer disposed inside a tread and a plurality of main grooves extending in the tire circumferential direction on the tread surface. In a heavy-duty pneumatic radial tire having a rib-based pattern that forms ribs, along with a zigzag shape in the tire circumferential direction at least the tire inner groove wall of the left and right outermost main grooves of each of the main grooves, A narrow groove continuous in the tire circumferential direction is provided on the shoulder side edge of the rib adjacent to the inside of the main groove, and the groove width W _{4 of the} narrow groove is set in the range of 0.5 to 1 mm, and the groove depth is The slant direction to the inside of the tire with respect to the normal line of the tread surface, to form a rib main body and a thin rib of the same height divided into left and right by the narrow groove, and the outermost main groove It is characterized in that it has a maximum width W ₂ of the narrow rib for the entire width W ₁ of the side ribs on the magnitude of W ₂ / W ₁ ≦ 0.3.

As described above, by providing the groove on the shoulder side of the rib adjacent to the inside of the outermost main groove in the tire circumferential direction, the inflection point is not formed in the outermost main groove. As described above, the rigidity change in the width direction of the tread is moderated. As a result, the diameter difference between the center portion and the shoulder portion at the time of inflation can be reduced, the drag frictional force to the shoulder portion due to the diameter difference can be reduced, and the rib main body having the same height divided by the narrow groove can be reduced. And thin ribs are formed, and the width of the thin ribs is changed in a zigzag manner in the tire circumferential direction to maintain an appropriate rigidity, so that the force that promotes wear is concentrated on the thin ribs and shoulder drop wear occurs. It is possible to effectively suppress uneven wear such as. Further, since the groove depth direction of the narrow groove is inclined to the inner side of the tire, the thin rib has a wall thickness on the base end side,
It is hard to drop out.

Hereinafter, the configuration of the present invention will be specifically described with reference to the accompanying drawings. In the following, the case of an optimum example in which five ribs are provided on the tread surface will be described, but the number of ribs is not particularly limited in the present invention. 1 and 2, 10 is a carcass layer, and 11 is four belt layers made of steel cords inserted between the carcass layer and the tread portion. The tread surface 1 is provided with two inner-side straight main grooves 2a and two outer-side zigzag-shaped main grooves 2b extending in the tire circumferential direction, whereby the left and right shoulder portions respectively have shoulder ribs 3, A middle rib 4 is formed inside one of the shoulder ribs 3, and a center rib 5 is formed at the center of the tread. The cross-sectional shape of the main grooves 2a, 2b may be either U-shaped or V-shaped.

The ribs 3, 4 and 5 are appropriately provided with kerfs extending in the tire width direction. The shoulder rib 3 is provided with a narrow groove 3a on the shoulder side edge portion so as to be straight and continuous in the tire circumferential direction.
It is composed of a thin rib 3b and a rib body 3c which are divided by a. On the other hand, the middle rib 4 is provided with a straight narrow groove 4a on the shoulder side edge portion so as to be continuous in the tire circumferential direction, and is composed of a thin rib 4b and a rib body 4c divided by the narrow groove 4a. ..

As shown in FIG. 3, the narrow groove 4a has a groove width W ₄ of 0.5 to 1 mm, and the groove depth direction is inclined toward the inner side of the tire with respect to the normal line of the tread surface 1. There is. The thin ribs 4b are provided so as to be continuous in the tire circumferential direction, and the height thereof is substantially the same as that of the rib body 4c. Since the thin rib 4b is adjacent to the zigzag-shaped main groove 2b,
Maximum width W ₂ and the minimum width the width of the tire circumferential direction (W ₂ -W
₃ ) changes in a range corresponding to the zigzag swing width W ₃ , and the maximum width W ₂ is W ₂ / W ₁ ≦ 0.3 with respect to the total width W _{1 of the} rib 4. Is set to be.

In such a heavy-duty pneumatic radial tire, the rigidity of the steel cord belt layer 11 inserted between the tread portion and the carcass layer is very high.
When inflated, the outermost main groove 2b becomes an inflection point, and the shoulder portion falls off. However, as described above, by providing the narrow groove 4a continuous in the tire circumferential direction at the shoulder side edge portion of the rib 4 adjacent to the inside of the main groove 2b, the rigidity change in the width direction of the tread becomes gentle,
Since the inflection point does not occur in the main groove 2b portion, the difference in diameter between the center portion and the shoulder portion during inflation is small. Therefore, since the drag frictional force of the shoulder portion due to the diameter difference can be reduced, the uneven wear of the shoulder rib 3 can be relatively suppressed.

Further, by providing the thin rib 4b on the shoulder side edge of the rib 4 adjacent to the inner side of the outermost main groove 2b, the force for promoting wear in the initial worn state is concentrated on the thin rib 4b. The thin rib 4b can be selectively worn. Since the total amount of the forces that promote wear on the tread surface is constant, the rib body 4 of the rib 4 is provided on the above-mentioned portion.
By providing the thin rib 4b having the same height as c, it is possible to reduce the wear force applied to other portions, especially the rib body 4c of the rib 4 in the initial wear state, so that the uneven wear of the rib 4 at the time of the initial wear can be reduced. Can be suppressed.

On the other hand, at the time of medium-term wear after the initial wear, the difference in the amount of wear causes a difference in the radius of gyration between the rib body 4c of the rib 4 and the thin rib 4b. Drag frictional force is generated. For this reason, the force for promoting wear can be concentrated on the thin ribs 4b even during medium-term wear, so that uneven wear such as shoulder drop wear can be effectively suppressed.

In the present invention, the groove width W ₄ of the fine groove 4a provided in the rib 4 adjacent to the inner side of the outermost main groove 2b is 0.5.
Set to ~ 1 mm. The lower limit of the groove width W ₄ of 0.5 mm is a limit due to the strength of the fine groove forming bone of the tire forming mold, and it is difficult to manufacture the tire if the groove width W ₄ is smaller than this. vice versa,
When the groove width W ₄ of the narrow groove 4a exceeds 1 mm, the rib body 4c
Since the gap between the ribs 4b and the thin ribs 4b is too wide, the protective action (interaction) of the rib body 4c cannot be obtained, and the above-mentioned effect of suppressing uneven wear cannot be obtained. The depth d ₂ of the narrow groove 4a is not particularly limited, but it is preferable to make it equal to or shallower than the depth d ₁ of the main groove 2b (d ₂ ≦ d ₁ ).

The maximum width W ₂ of the thin rib 4b is set so that W ₂ / W ₁ ≤0.3 with respect to the total width W _{1 of the} rib 4. When W ₂ / W ₁ > 0.3, the difference in rigidity between the rib body 4c and the thin rib 4b becomes small, and it becomes difficult to concentrate the force that promotes wear on the thin rib 4b. However, since the thin ribs 4b as described above are easily chipped during manufacturing or running,
The groove depth direction of the thin groove 4a is inclined toward the tire inner side with respect to the normal line of the tread surface 1 so that the base end portion of the thin rib 4b is thicker than the tip end portion. The angle θ ₂ formed by the narrow groove 4a with respect to the normal line of the tread surface 1 is more than 0 ° and 10 ° or less (0 ° <θ
₂ ≦ 10 °) is preferable.

The narrow rib 4b is a side wall facing the main groove 2b.
The (groove wall) has a zigzag shape in the tire circumferential direction.
As a result, the rib width is the maximum width W₂And the minimum width (W₂-W₃)
It is designed to change periodically between and. W₂/ W
₁When ≦ 0.3, the rigidity of the thin rib 4b becomes small.
If it is too large, the effect of preferentially wearing the thin rib 4b is reduced.
As described above, the main groove side of the thin rib 4b is
The zigzag shape ensures the rigidity of the thin ribs 4b
can do. In this case, the maximum width portion of the thin rib 4b
The side wall facing the main groove 2b is the normal line of the tread surface 1
Angle α to₁In the minimum width part of the thin rib 4a.
The side wall facing the main groove 2b with respect to the normal to the tread surface 1
Angle α₂It is preferably smaller than the above. this
So α ₂> Α₁By setting the zigzag of the main groove 2b
Straighten the tangential shape where the groove-shaped groove wall meets the groove bottom
Therefore, drainage performance is improved.

The angle α ₁ of the thin rib 4b is preferably larger than the angle θ ₁ formed by the side wall of the shoulder rib 3 on the main groove 2b side with respect to the normal line of the tread surface 1. By setting α ₁ > θ _{1 in} this way, the inclination angles of both side walls of the main groove 2b are different, so that even if a stone bite occurs in the main groove 2b, the stone can be easily removed.

[0017]

EXAMPLES Six types of heavy-duty pneumatic radial tires having the same tire size and tire structure as described below, and the rib pattern shown in FIGS. I made it. Tire size 11R22.5 14PR Tire structure Carcass layer: A one-layer structure composed of steel cords arranged at 90 ° to the tire circumferential direction.

Belt layer: A laminated structure of four belts made of steel cords, the cord angle of the first layer in contact with the carcass with respect to the tire circumferential direction is + 57 °, the cord angle of the second layer is + 18 °, and the cord angle of the third layer is −. The angle was 18 ° and the code angle of the fourth layer was −18 °. The groove width of the tire main groove 2b of the present invention is 13 mm (zigzag shape) The groove width of the narrow groove 4a is W ₄ 1 mm The angle of the narrow groove 4a is θ ₂ 10 ° The total width W ₁ 30 mm of the rib 4 is the maximum width W ₂ 9 mm (W ₂ / W ₁ = 0.
3) Comparative tire 1 Same as the tire of the present invention except that the main groove 2b has a straight shape. Comparative tire 2 Same as the tire of the present invention, except that the groove width W ₄ of the narrow groove 4a was set to 1.5 mm. Comparative tire 3 Same as the tire of the present invention, except that the angle θ _{2 of the} narrow groove 4a was 0 °. Comparative tire 4 W ₂ / W ₁ the same as the present invention tire except that the 0.4. Except that no provided with conventional tire rib 4 a narrow groove 4a and the narrow rib 4b the same as the present invention tire.

The uneven wear resistance of each of these six types of tires was evaluated by the following test methods. Uneven wear resistance test Before and after running on a general pavement for 50,000 km in an actual vehicle, the depths of the main grooves 2a and 2b of the test tire were measured, respectively.
Measured by reading to one decimal place in mm unit, the difference between the measured values before and after the test running for each groove is taken as the wear amount, and the difference between the wear amount of the main groove 2a and the wear amount of the main groove 2b is calculated. Then, the amount of uneven wear was determined. Then, the running distance (50,000 km) was divided by this uneven wear amount to calculate the running distance per 1 mm of uneven wear amount, which was taken as the uneven wear resistance. The evaluation results are shown in Table 1 by an index with the conventional tire being 100. The larger this index value, the better the uneven wear resistance.

[0020] As is clear from Table 1, the tire of the present invention was superior in uneven wear resistance to the conventional tire. On the other hand, Comparative tires 1 to 4 which are out of the specified range of the present invention are inferior in uneven wear resistance to the tire of the present invention, and in particular, in Comparative tire 3 in which the angle θ ₂ of the fine groove 4a is 0 °, 4b was missing.

[0021]

As described above, according to the present invention, in a heavy duty pneumatic radial tire having a steel belt layer in a tread portion and having a rib-based pattern,
A narrow groove that is continuous in the tire circumferential direction is provided on the shoulder side edges of the ribs that are adjacent to the inside of the main grooves that are located on the outermost left and right sides, and the groove width W ₄ of this narrow groove is in the range of 0.5 to 1 mm. In addition, the groove depth direction is inclined toward the tire inner side with respect to the normal line of the tread surface to form a rib main body and a thin rib having the same height, which are divided by the narrow groove, and Since the main groove side has a zigzag shape and the maximum width W ₂ of the thin ribs with respect to the total width W ₁ of the ribs is W ₂ / W ₁ ≦ 0.3, uneven wear such as shoulder drop wear is effective. Can be suppressed to.

[Brief description of drawings]

FIG. 1 is a development view showing a tread surface of a heavy duty pneumatic radial tire according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a partially enlarged sectional view of FIG.

[Explanation of sign]

 1 Tread surface 2a, 2b Main groove 3,4,5 Ribs 3a, 4a Fine groove 3b, 4b Fine rib 3c, 4c Rib body 10 Carcass layer 11 Belt layer

Claims (1)

[Claims] 1. A heavy-duty pneumatic radial tire having a rib-based pattern in which a plurality of main grooves extending in the tire circumferential direction are provided on a tread surface while a steel belt layer is arranged inside the tread, and a rib-based pattern is formed. Of the main grooves, at least the groove walls on the tire inner side of the left and right outermost main grooves are formed in a zigzag shape in the tire circumferential direction, and on the shoulder side edges of the ribs adjacent to the inside of the main groove, A narrow groove that is continuous in the tire circumferential direction is provided,
The width W _{4 of the} narrow groove is set in the range of 0.5 to 1 mm, and the depth direction of the groove is tilted inward of the tire with respect to the normal line of the tread surface. A rib main body having a height and a thin rib are formed, and the maximum width W ₂ of the thin rib with respect to the total width W ₁ of the rib inside the outermost main groove is set to W ₂ / W ₁ ≦ 0.3. Pneumatic radial tire for heavy loads.