JPH05178016A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To provide a heavy load pneumatic radial tire which does not lower deviated 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, at least the rib 3 positioned at the car extreme outside at the time of installing on a car and its adjoining rib 3 out of a plural number of the ribs 3 are divided into a plural number of blocks by way of providing a plural number of kerfs 4 so that they cross these ribs respectively. Additionally, this is a pneumatic radial tire for heavy load provided with the kerfs whose groove width is 1.5mm or less and whose depth is shallower on the rib 3 positioned inside than the rib 3 on the car extreme outside gradually or arrangement intervals in the tire circumferential direction are to be gradually wider on the ribs 3 inside of the car outside rib 3.

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 having improved uneven wear resistance of a steering tire.

[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, since 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 wheel of the vehicle, which is particularly noticeable in a heavy-duty vehicle, 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 the ribs located on the outermost side of the vehicle when mounted on the vehicle and the ribs adjacent to the ribs are provided with a plurality of kerfs so as to cross them, and divided into a plurality of blocks, and the groove width of the kerfs is set to 1.5 mm or less. , The depth of this kerf is set to be gradually shallower for the ribs located on the inner side of the outermost rib of the vehicle, or the arranging intervals of this kerf in the tire circumferential direction are gradually increased for the ribs located on the inner side of the vehicle outer ribs. It is characterized in that it is provided as follows.

As described above, since at least the ribs located on the outermost side of the vehicle and the ribs adjacent thereto are provided with a kerf having a groove width of 1.5 mm or less so as to cross the ribs at least when the vehicle is mounted, the ribs on the outer side of the vehicle The rigidity can be reduced, and the load concentrated on the outer ribs is released during cornering to prevent uneven wear such as shoulder wear and shoulder drop wear. Moreover, since the depth of the kerf is set to be gradually shallower for the ribs on the inner side than the ribs on the outermost side of the vehicle, or the arrangement interval of the kerfs in the tire circumferential direction is set to be gradually wider for the inner ribs, the tread width direction The gradual change in the rigidity of is to prevent the uneven wear more effectively. Further, 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, the 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 are plan views showing an embodiment of the tread pattern of the tire of the present invention. Tread 1
Is provided with four main grooves 2 extending in the tire circumferential direction, and five ribs 3 divided into these main grooves 2 are formed. Of these ribs 3, the outermost one and the other two when the vehicle is mounted.
The third and third ribs 3 are each provided with a kerf 4 so as to cross the tire circumferential direction at intervals, forming a large number of blocks 5. The kerf 4 has a Z-shaped sub kerf 4a in plan view connected to the middle portion thereof, and the 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 groove width of this calf 4 is 1.
If it is larger than 5 mm, the rigidity of the shoulder rib will be reduced more than necessary, and it will be difficult to maintain steering stability by maintaining the rigidity when the blocks are in mutual contact.

The function of the kerf 4 is to impart 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. As shown in FIG. 2, the kerf 4 provided on the outermost rib 3 when mounted on the vehicle.
Is provided such that the depth d thereof is the deepest in the outermost rib 3 of the vehicle and becomes shallower in the ribs 3 which are successively adjacent to the inner side. The depth d of the kerf 4 to which such a change is applied is preferably within the range of 20 to 70% of the main groove 2. 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. Further, the arrangement intervals of the kerfs 4 in the tire circumferential direction are set so that the outermost ribs 3 of the vehicle are the narrowest and the ribs 3 that are sequentially adjacent to the inner side are wider.

In the present invention, the rib for providing the kerf 4 may be provided at least on the outermost rib and the rib adjacent to the outermost rib when the vehicle is mounted, and is not necessarily required on the inner rib. Further, the shape of the kerf is not limited to the curved shape as shown in FIG. 1, but may be a linear shape as shown in FIGS. 3 and 4. The angle of the calf with respect to the tire circumferential direction is
It may be a right angle as shown in FIG. 3 or may be inclined as shown in FIGS. 4 and 5. 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. 4 and 5.

[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 width: 220mm Main groove depth: 15mm Calf groove depth: Outermost rib 8mm Second rib 6mm Third rib 4mm Calf groove width: 0.7mm Average calf pitch length: 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 evaluation method, 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. The amount of wear was calculated. As for the evaluation value, the reciprocal of the wear amount is 100 for the conventional tire.
It was shown by indexing as (standard).

[0015] As can be seen from the results in Table 1, the tires of the present invention have improved uneven wear resistance against shoulder wear and shoulder drop wear, as compared with the conventional tires 1 to 3, and the wear resistance is hardly reduced. The wear resistance is improved for the conventional tire 3 having the same uneven wear resistance.

[0016]

As described above, according to the present invention, at least ribs located on the outermost side of the vehicle at the time of mounting on the vehicle and ribs adjacent to the ribs are provided with kerfs having a groove width of 1.5 mm or less so as to cross these ribs to form a block. Therefore, the rigidity of the vehicle outer rib can be reduced, and the load concentrated on the outer rib during cornering is released to prevent uneven wear. Moreover, since the depth of the kerf is set to be gradually shallower for the ribs on the inner side than the ribs on the outermost side of the vehicle, or the arrangement interval of the kerfs in the tire circumferential direction is set to be gradually wider for the inner ribs, the tread width direction Change the rigidity of
Try to prevent uneven wear more effectively. Further, 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, the wear resistance is not reduced.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a tread pattern 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 a conventional tire.

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

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

FIG. 10 is a cross-sectional view of the tire in the meridian direction and is an explanatory view showing shoulder wear of the tire.

FIG. 11 is a cross-sectional view of the tire in the meridian direction and is an explanatory view showing shoulder drop wear of the 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 based on a rib pattern composed of a plurality of ribs on a tread surface, wherein at least one of the plurality of ribs is located on the outermost side of the vehicle when mounted on the vehicle. A plurality of kerfs are provided so as to cross the ribs adjacent to each other and divided into a plurality of blocks, and the groove width of the kerf is set to 1.5 mm or less, and the depth of the kerf is set to the outermost position of the vehicle. A heavy-duty pneumatic radial tire provided such that the ribs located inside the ribs become gradually shallower, or the arrangement intervals of the kerfs in the tire circumferential direction become wider sequentially toward the ribs located inside the vehicle outer ribs. ..