JPH05201206A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To provide a pneumatic radial tire for heavy load which can restrain wavy abrasion, polygonal abrasion, etc., evolving from shoulder-reduced abrasion by restraining partial abrasion at a shoulder part at initial abrasion. CONSTITUTION:At an edge on the center side of a shoulder rib 6, a narrow groove 3 of the groove width of 0.5 to 4mm continuing in the tire circumferential direction is provided, and a narrow rib 7 of the same height as a main rib 6a of the shoulder rib 6 is formed by this.

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 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 suspensions has progressed in order to improve the riding comfort of trucks, buses, and the like, and along with this, uneven wear is likely to occur, in which uneven wear progresses in the shoulder portion of the front wheel radial tire. Uneven wear of a tire is a phenomenon in which a place that is worn more than others is further worn. Therefore, it is important to wear the tread surface uniformly during initial wear. This uneven wear is likely to occur at the shoulder portion of the tread surface, but shoulder drop wear is particularly likely to occur, and further, corrugated wear, polygonal wear, etc. often occur.

Conventionally, as a measure against uneven wear, there has been proposed, for example, Japanese Patent Laid-Open No. 63-134313, in which a fine groove is provided outside the shoulder portion.

[0004]

However, in the above technique, it is not sufficient to suppress uneven wear in the shoulder portion at the time of initial wear, and therefore, for example, when the vehicle alignment is not sufficient, shoulder drop wear occurs. Not only does it occur, but it often progresses to corrugated wear and polygonal wear, and there is a problem that the effect of suppressing uneven wear is insufficient.

An object of the present invention is to provide a heavy-duty pneumatic radial tire which is capable of suppressing wavy wear, polygonal wear and the like that develop from shoulder drop wear by suppressing uneven wear at the shoulder during initial wear. To provide.

[0006]

A pneumatic radial tire for heavy load according to the present invention is a rib in which a plurality of main grooves extending in the tire circumferential direction are provided on a tread surface and shoulder ribs are formed on at least both left and right shoulder portions. In a heavy-duty pneumatic radial tire having a basic pattern, a groove width of 0.5 is formed at the center side edge of the shoulder rib.
It is characterized in that a thin groove having a width of up to 4 mm is provided continuously in the tire circumferential direction, and a thin rib having the same height as the shoulder rib main body divided into the thin groove is formed.

Hereinafter, the configuration of the present invention will be specifically described with reference to the accompanying drawings. 1 and 2, the tread surface 1 is provided with a plurality of main grooves 2 extending in the tire circumferential direction, whereby the ribs 4, 5 and shoulder ribs 6 are divided from each other. The rib 5 is provided with a kerf 8. The shoulder ribs 6 are provided at the center side edge portion and the shoulder side edge portion so that the thin grooves 3 and 3a are continuous in the tire circumferential direction, and the thin ribs 7 and 7a are divided into these thin grooves 3 and 3a. And a main rib 6a. Each of the thin ribs 7 and 7a is provided so as to be continuous in the tire circumferential direction, and the height thereof is substantially the same as that of the main rib 6a.

As described above, in particular, by providing the thin rib 7 on the center side edge of the shoulder rib 6, the wear force (wearing force) in the initial wear state is concentrated on the thin rib 7, and the thin rib 7 is formed. Can be selectively worn. Since the total amount of the forces that promote wear on the tread surface is constant, the main rib 6a of the shoulder rib 6 is attached to the above-mentioned portion.
By providing the thin ribs 7 having the same height as the above, it is possible to reduce the wear force applied to other portions, particularly the main body of the shoulder ribs 6 (main ribs 6a) in the initial worn state. Therefore, it is possible to suppress uneven wear in the shoulder portion during initial wear.

On the other hand, at the time of medium-term wear after the initial wear, a difference in the radius of gyration occurs between the main ribs 6a of the shoulder ribs 6 and the thin ribs 7, so that there is a difference in the diameter of the thin ribs 7. A dragging phenomenon occurs. Therefore, the wear force can be concentrated on the thin ribs 7 even during the medium-term wear, so that it is possible to suppress the shoulder wear and the corrugated wear and polygonal wear that develop from the shoulder wear.

In the present invention, the groove width B of the fine groove 3 is set to 0.5 to 4 mm. Lower limit of groove width B 0.5 mm
Is a limit due to the strength of the fine groove forming bone of the tire forming die, and it is difficult to manufacture a tire if the bone is thinner than this.
On the contrary, when the groove width B exceeds 4 mm, the main rib 6a and the thin rib 7 are formed.
Is too wide, the protective action (interaction) of the main rib 6a cannot be obtained, and the above-mentioned effect of suppressing uneven wear cannot be obtained. Further, it is desirable that the width A of the main rib 6a and the width C of the thin rib 7 have a relationship of 0.12 ≦ C / A ≦ 0.32. When C / A <0.12, the rigidity of the thin rib 7 is too small, and the effect of preferentially wearing the thin rib 7 is reduced. On the other hand, when C / A> 0.32, the difference in rigidity between the main rib 6a and the thin rib 7 becomes small, and it becomes difficult to concentrate the wear force on the thin rib 7.

Further, it is desirable that at least one of the wall surfaces of the thin rib 7 is inclined in a taper shape, and the tapered shape can prevent the thin rib 7 from being cut off during traveling. In the example of the figure, an inclined portion (taper) is provided from the bottom surface of the main groove 1 to the upper surface of the thin rib 7. In this case, the relationship between the width A of the main rib 6a including the width D of the inclined portion and the width C of the thin rib 7 is 0.15 ≦ (C +
It is preferable that D) /A≦0.35.

[0012]

EXAMPLES Tire size 11R22.5, tread pattern shown in FIG. 1, fine grooves 3, 3a, fine ribs 7, 7
a, the width B, E, C, A of the main rib 6a is 2 mm,
A heavy-duty pneumatic radial tire according to the present invention having a size of 2 mm, 5 mm, and 35 mm, and a narrow groove 3 in the tire.
A comparative tire in which only the fine rib 7 was not provided was prepared and mounted on the front wheel of a vehicle having a weight of 10 tons, and a running test was conducted.

As a result, in the tire of the present invention, the wear force is concentrated on the thin ribs 7 during the initial wear up to 20,000 km running, and only the thin ribs 7 are rapidly worn. Therefore, as shown in FIG. The step between the rib 6a and the thin rib 7 was d ₁ . Along with this, uneven wear at the shoulder portion during initial wear could be suppressed. Further, during the medium-term wear up to 40,000 km, the step between the main rib 6a and the thin rib 7 was d ₂ as shown in FIG. At this time, it is confirmed that the relationship of d ₂ ≈d ₁ is maintained because the difference in drag phenomenon occurs in the thin ribs 7 and the wear force is concentrated. As a result, uneven wear such as wavy wear and polygonal wear is confirmed. No wear occurred. Furthermore, uneven wear did not occur even after traveling 60,000 km.

On the other hand, in the comparative tire, slight shoulder drop wear was generated on the shoulder ribs 6 after running 20,000 km, and after running 40,000 km, the uneven wear was further advanced and developed into wavy wear.

[0015]

As described above, according to the present invention, a narrow groove having a groove width of 0.5 to 4 mm which is continuous in the tire circumferential direction is provided at the center side edge portion of the shoulder rib, and the shoulder rib is divided into the narrow grooves. Since the thin rib having the same height as that of the shoulder rib body is formed, it is possible to concentrate the wear force on the thin rib at the time of initial wear and maintain this characteristic thereafter. For this reason, it is possible to suppress a slight uneven wear of the shoulder portion particularly at the time of initial wear, and to suppress the development of wavy wear, polygonal wear, and the like.

[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 cross-sectional view of FIG.

FIG. 3 is a cross-sectional view showing the pneumatic radial tire for heavy load of the present invention after traveling 20,000 km.

FIG. 4 is a sectional view showing the pneumatic radial tire for heavy load of the present invention after traveling 40,000 km.

[Explanation of sign]

 1 tread surface 2 main groove 3,3a thin groove 4 center rib 5 block row 6 shoulder rib 7,7a thin rib 8 calf

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, and shoulder ribs are formed on at least left and right shoulder portions, respectively. A thin radial groove having a groove width of 0.5 to 4 mm that is continuous in the tire circumferential direction is formed, and a thin rib having the same height as the shoulder rib main body divided into the narrow groove is formed. tire.