JPH05178018A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To provide a heavy load pneumatic radial tire which does not lower abrasion resistance of the tire provided with a rib pattern but improves the resistance. CONSTITUTION:On a pneumatic radial tire for heavy load provided with a tread pattern of a rib pattern keynote consisting of a plural number of ribs 3 on a tread surface 1, at least the rib 3 positioned on the car outside at the time of installing it is divided into a plural number of blocks 5 by way of providing a plural number of kerfs 4 crossing this rib 3, and this is a pneumatic radial tire for heavy load where groove width of these kerfs is 1.5mm or less.

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, and more particularly to a heavy-duty pneumatic radial tire with improved uneven wear resistance of the tire mounted on the front wheels of a heavy-duty vehicle.

[0002]

2. Description of the Related Art Generally, a radial tire for steering mounted on the front wheels of a heavy-duty vehicle such as a truck or a bus does not require a driving force, and therefore has a smaller groove area than a block pattern and is excellent in wear resistance. Rib patterns are mainly used. However, a large load is concentrated on the shoulder portion on the outer side of the vehicle due to the centrifugal force at the time of cornering of the front wheels of the vehicle, and this is particularly noticeable in a heavy-duty vehicle, so that shoulder wear as shown in FIG. It has been pointed out that uneven wear such as shoulder drop wear easily occurs.

To prevent uneven wear of a heavy-duty pneumatic radial tire for a front wheel having such a rib pattern, Japanese Patent Laid-Open No. 62-103205 discloses a vehicle mounted on a vehicle as shown in FIG. It has been proposed to prevent the shoulder wear from occurring by reducing the groove area ratio of the outer portion. However, although such a tire is effective for shoulder wear, since the rigidity of the outer edge portion of the outermost shoulder rib is high, the above-mentioned shoulder drop wear cannot be eliminated, so sufficient uneven wear prevention is possible. It was not a countermeasure.

Further, in Japanese Patent Laid-Open No. 63-106113, a fine groove 6 continuous in the tire circumferential direction is arranged near the edge of the outermost rib when mounted on a vehicle as shown in FIG.
It has been proposed to dispose intermittent narrow grooves 6 in the tire circumferential direction near the edge of the innermost rib, or to dispose continuous narrow grooves 6 on both shoulders as shown in FIG. However, these tires have a problem that the wear resistance of the entire tread is lowered because the outer edge portion of the narrow groove has a very low contribution rate to the wear resistance.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heavy duty pneumatic radial tire having improved uneven wear resistance without lowering the wear resistance of the tire provided with the rib pattern. ..

[0006]

The present invention for achieving the above object provides a pneumatic radial tire for heavy load in which a tread pattern having a rib pattern based on a plurality of ribs is provided on a tread surface. Out of the ribs
At least when the vehicle is mounted on the vehicle, the ribs located outside the vehicle are provided with a plurality of kerfs that cross the ribs to divide them into a plurality of blocks, and the groove width of the kerfs is 1.5 mm or less.

As described above, among the plurality of ribs, at least the rib located outside the vehicle when the vehicle is mounted is provided with the plurality of kerfs having a groove width that traverses the rib. The load concentrated on the outer ribs is released to prevent uneven wear such as shoulder wear and shoulder drop wear. Moreover, since only the kerf having a groove width of 1.5 mm or less is provided and the ground contact area of the tread is not substantially reduced, wear resistance is not reduced.

The tire of the present invention will be described in detail below with reference to the drawings. 1 and 2 show an embodiment of the tread portion of the tire of the present invention. Four main grooves 2 extending in the tire circumferential direction are provided on the surface of the tread 1, and five ribs 3 divided into these main grooves 2 are formed.
Of these ribs 3, the outermost rib when the vehicle is mounted and the second and third ribs 3 are respectively provided with kerfs 4 across the tire circumferential direction at intervals to form a large number of blocks 5. There is. By unevenly distributing the kerf 4 to the outside of the vehicle in this manner, the load concentrated on the outside is relaxed and uneven wear is prevented. The kerf 4 has a sub-kerf 4a, which is Z-shaped in plan view, connected to an intermediate portion of the kerf 4, and the groove depth thereof is deeper than the groove depth of the kerf body.

In the above structure, the kerf 4 has a groove width of 1.
It is 5 mm or less. Since the kerf 4 has such a small groove width, even if the block 5 is formed on the rib 3, each rib 3 maintains the original characteristics of the rib such as good wear resistance. The function of the kerf 4 is to impart the uneven wear resistance by blocking the ribs 3 as described above, so that the lower limit of the groove width may be substantially zero. However, when the kerf 4 is molded with the molding bone of the mold, 0.4 mm is the lower limit of the groove width because the bending problem occurs when the molding bone becomes thinner than 0.4 mm.

The groove depth d of the kerf 4 is preferably the main groove 2
20-70% of is recommended. Here, the groove depth d means the depth of the main body portion of the kerf 4, and the depth of the sub kerf 4a is not taken into consideration. With such a groove depth, the above-mentioned effect of preventing uneven wear is further ensured. Also, the groove depth d of this calf 4
As shown in FIG. 2, it is desirable that the kerf 4 provided on the outermost rib 3 when mounted on the vehicle is deeper, and then the kerfs 4 of the ribs 3 which are sequentially adjacent to the inner side are shallower. By disposing such groove depths, the uneven wear resistance can be further improved. Further, the arrangement interval of the kerfs 4 in the tire circumferential direction is the smallest in the ribs 3 on the outermost side of the vehicle, and the widths of the ribs 3 which are adjacent to the inner side in the order of width increase.
The same effect can be obtained.

In the present invention, the rib provided with the kerf may be provided on at least the outermost rib when the vehicle is mounted,
The ribs on the inner side of the ribs are not always necessary. Also,
The shape of the kerf is not limited to the bent shape as shown in FIG. 1, but may be a linear shape as shown in FIGS. 3 and 4. Further, the angle of the calf with respect to the tire circumferential direction may be a right angle as shown in FIG. 3 or may be inclined as shown in FIG. When kerfs are provided on a plurality of rows of ribs, it is desirable that the inner ribs have a smaller inclination angle as shown in FIGS. The pitch length of the calf 4 in the tire circumferential direction is preferably 10 to 40% of the tread development width.

[0012]

[Example] With a tire size of 11R22.5 14PR,
A heavy-duty pneumatic radial tire of the present invention having the tread pattern shown in FIG. 1 and having the dimensions of respective specifications as follows was manufactured. Tire specifications Tread deployment width: 220mm Main groove depth: 15mm Calf groove depth: Outermost rib 8mm Second rib 6mm Third rib 4mm Calf groove width: 0.7mm Average pitch length of calf: Outermost rib 40 mm Second rib 40 mm Third rib 40 mm For comparison, the above-mentioned tire of the present invention, tire size,
The tread development width and the main groove depth are all the same, and FIG.
Conventional tire 1 having the tread pattern shown in FIG. 6, conventional tire 2 having the tread pattern shown in FIG. 7, and FIG.
Conventional tires 3 each having a tread pattern and a left and right continuous and intermittent fine grooves each having a groove width of 2.5 mm were manufactured.

Each of these four types of tires has a rim 2
When mounted on 2.5 × 8.25 and tested for uneven wear resistance (shoulder wear, shoulder drop wear) and wear resistance by the evaluation method under the following conditions, the results shown in Table 1 were obtained. Uneven wear resistance evaluation method: a) Shoulder wear: Air pressure 7 kg / cm on the test tire.
² is filled and mounted on the front wheels of a truck (2-D-4 car), and after running 60,000 km on a general road, the groove depth of each groove is measured and the wear amount of the outermost main groove (mm ) And the wear amount (mm) of the innermost main groove.

B) Shoulder drop wear: After running under the same conditions as the above shoulder wear evaluation method, the shoulder step difference t (m
m) (see FIG. 11) was measured. Evaluation of wear resistance: After running under the same conditions as the above shoulder wear, the groove depth of each groove was measured, the difference between each groove and the groove depth when new was calculated, and the average value thereof was calculated. It was defined as the amount of wear. The evaluation value was shown by indexing the reciprocal of the wear amount with the conventional tire as 100 (reference).

[0015] As can be seen from the results in Table 1, the tire of the present invention has improved uneven wear resistance as compared with the conventional tires 1 and 2, but the wear resistance is almost at the same level as the conventional tire. The conventional tire 3 exhibits the same uneven wear resistance as the tire of the present invention, but is inferior in wear resistance.

[0016]

As described above, according to the present invention, among a plurality of ribs, at least a rib located outside the vehicle when the vehicle is mounted is provided with a plurality of kerfs having a groove width of 1.5 mm or less that traverses the ribs. By dividing the rib into the blocks, the rigidity of the vehicle outer rib can be reduced and the uneven wear resistance can be improved. Moreover, since only the kerf having a groove width of 1.5 mm or less is provided and the ground contact area of the tread is not substantially reduced, wear resistance is not reduced.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a tread portion of a tire of the present invention.

FIG. 2 is a meridional section view of the tire of FIG.

FIG. 3 is a plan view showing another embodiment of the tread pattern of the tire of the present invention.

FIG. 4 is a plan view showing still another embodiment of the tread pattern of the tire of the present invention.

FIG. 5 is a plan view showing still another embodiment of the tread pattern of the tire of the present invention.

FIG. 6 is a plan view showing a tread pattern of a conventional tire.

FIG. 7 is a plan view showing a tread pattern of another conventional tire.

FIG. 8 is a plan view showing a tread pattern of another conventional tire.

FIG. 9 is a plan view showing a tread pattern of another conventional tire.

FIG. 10 is an explanatory view showing shoulder wear of a tire.

FIG. 11 is an explanatory diagram showing shoulder drop wear of a tire.

[Explanation of symbols]

 1 tread 2 main groove 3 rib 4 calf 5 block

Claims (1)

[Claims] 1. A heavy-duty pneumatic radial tire having a tread pattern having a rib pattern based on a plurality of ribs on the tread surface, wherein at least one of the plurality of ribs is located outside the vehicle when the vehicle is mounted. A heavy-duty pneumatic radial tire, which is divided into a plurality of blocks by providing a plurality of kerfs crossing the ribs and has a groove width of 1.5 mm or less.