JPH05178015A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To provide a heavy load pneumatic radial tire which effectively prevents both shoulder abrasion and shoulder drop abrasion of the tire provided with a rib pattern. CONSTITUTION:On a heavy load pneumatic radial tire provided with a plural number of main grooves 2 extending in the tire circumferential direction on a tread surface and provided with a tread pattern of a rib pattern keynote consisting of a plural number of ribs 3 divided by these main grooves 2, the surface is divided into a plural number of blocks 5 by providing a plural number of kerfs 4 at least on the ribs positioned on the car extreme outside at the time of installing it on a car and on their adjoining ribs 3 out of a plural number of the ribs 3. Additionally, this is a pneumatic radial tire where groove width of the kerfs 4 is 1.5mm or less, depth of the is in a range of 20-70% of the main groove 2 depth and an angle of the kerfs 4 in the tire circumferential direction is within a range of 40-80 degrees.

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, the front wheel of the vehicle has a large load concentrated on the shoulder portion outside the vehicle due to the centrifugal force during cornering, and this is particularly noticeable in a heavy-duty vehicle, so that it goes toward the shoulder end portion outside the vehicle as shown in FIG. Shoulder wear, which increases the amount of wear,
As shown in FIG. 14, it has been pointed out that uneven wear such as shoulder drop wear in which only the shoulder ends are largely worn locally is likely to occur.

Therefore, as a measure for preventing 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, it is not possible to eliminate the above-mentioned shoulder drop wear, so complete uneven wear prevention It was not a countermeasure.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heavy duty pneumatic radial tire which effectively prevents both shoulder wear and shoulder drop wear of a tire provided with a rib pattern.

[0005]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a rib comprising a plurality of main grooves extending in the tire circumferential direction on a tread surface and a plurality of ribs divided by the main grooves. In a heavy-duty pneumatic radial tire provided with a tread pattern of a pattern basis, among the plurality of ribs, at least a rib positioned on the outermost side of the vehicle at the time of mounting on the vehicle and a plurality of ribs adjacent to the rib located at the outermost side of the vehicle The kerf is divided into a plurality of blocks, the groove width of the kerf is 1.5 mm or less, the depth of the kerf is in the range of 20 to 70% of the main groove depth, and the angle of the kerf with respect to the tire circumferential direction. Is in the range of 40 to 80 °.

As described above, at least the ribs located on the outermost side of the vehicle and the ribs adjacent thereto are provided with a plurality of kerfs so as to cross the ribs at least when the vehicle is mounted, and the ribs are divided into a plurality of blocks so that the rigidity of the ribs on the outside of the vehicle is improved. Because it lowers
Unbalanced wear such as shoulder wear and shoulder drop wear is prevented by releasing the load concentrated on the outer ribs during cornering. Moreover, although the rib rigidity is reduced, the depth of the kerf is set within the range of 20 to 70% of the depth of the main groove, so that the rigidity of the block is maintained and the groove of the kerf is maintained. Since the blocks are brought into contact with each other and restrained against each other by setting the width to 1.5 mm or less, it is possible to maintain an appropriate rigidity as a rib and not lower the required steering stability.

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 one, the second one, and the third one when the vehicle is installed.
A kerf 4 is provided on each of the second ribs 3 so as to be spaced apart in the tire circumferential direction, and forms a large number of blocks 5. The calf 4 has a Z-shaped plan view in the middle thereof.
The character-shaped sub kerfs 4a are connected to each other, and the groove depth thereof is deeper than the groove depth of the kerf body. Further, narrow grooves 9 are provided at both shoulder ends of the tread 1 so as to extend in the tire circumferential direction.

3 and 4 show other embodiments, respectively. The basic structure is the same as that of FIGS. 1 and 2 described above, but is different in that the kerf 4 is not provided with the sub-kerf 4a of the deep groove. Further, in the case of FIG. 4, the narrow groove 9 is provided at the shoulder end portion, but in FIG. 3, this is not provided. In the configuration of each of the above-described embodiments, the groove width of the kerf 4 is 1.5 mm or less, and the groove depth d is in the range of 20 to 70% of the depth 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. Since the kerf 4 has such a groove width and groove depth, even if the block 5 is formed on the ribs 3, each rib 3 maintains its original characteristics such as good wear resistance. There is. If the groove depth of the calf 4 is shallower than 20% of the main groove depth, the rigidity of the shoulder rib cannot be reduced,
No improvement in uneven wear resistance can be expected. If the groove width is larger than 1.5 mm or the groove depth is larger than 70% of the main groove depth, the rigidity of the shoulder ribs will be reduced more than necessary, and the steering stability will be maintained by maintaining the rigidity in mutual contact. It becomes difficult to maintain sex.

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. If the groove depth of the kerf 4 is increased to more than 70% of the main groove depth, heel-and-toe wear is likely to occur due to the movement associated with the decrease in rib rigidity. The groove depth of the kerf 4 is determined by the kerf 4 provided on the outermost rib 3 when the vehicle is mounted.
It is desirable that the kerfs 4 of the ribs 3 that are adjacent to the inner side of the ribs 3 are deeper than the deepest. By disposing such groove depths, the uneven wear resistance can be further improved.

The kerf 4 has an angle of 40 to 80 ° with respect to the tire circumferential direction. If it is less than 40 °, the rigidity of the rib is lowered and the movement becomes large, and if it is more than 80 °, the edge of the kerf 4 hits the road surface properly at the time of contact with the ground, so that heel and toe wear is likely to occur. When the kerf 4 has a bent shape as shown in FIG. 1, the kerf 4 is arranged at an angle formed by a straight line connecting the intersections where the kerf 4 intersects both side edges of the rib 3 with respect to the tire circumferential direction. Shall be represented.

In the present invention, the inclination direction of the belt layer of the kerf 4 with respect to the cord is not particularly limited, but preferably the belt layer disposed inside the tread 1 as shown in FIGS. 5 and 6. It is preferable that the belt width of the belt width 6 is 75% or more of the tread development width TDW, but the cord direction of the outermost belt layer 8c and the tire circumferential direction cross each other.

Generally, the belt layer 6 of a heavy-duty radial tire is constructed by using a steel cord as a reinforcing cord. As shown in FIGS. 5 and 6, the belt layer 6 is located on the innermost side adjacent to the carcass layer 9 and has a tire circumferential direction. To the outer circumferential surface of the reinforcing layer 7 having a cord angle of about 40 to 75 ° and a cord angle to the tire circumferential direction of about 15 ° to 3 °.
It is composed of a plurality of tension layers 8a, 8b, 8c having an angle of 0 °. In this tension layer, a belt layer 8 having a narrow belt width not exceeding 75% of the tread development width TDW is provided.
In some cases, the c may be arranged auxiliary to the outermost side, but in the present invention, it is not the auxiliary narrow belt layer 8c that is made to intersect with the kerf 4 but the tread spread width T.
Among the belt layers having a belt width of 75% or more of DW, the outermost belt layer 8b is in the cord direction. Therefore, for the narrow belt layer 8c, the cord direction may be the same direction as the inclination direction of the kerf 4, as shown in FIG.

As described above, the inclination direction of the kerf 4 intersects the cord direction of the outermost belt layer 8b with the belt width of 75% or more of the tread development width TDW and the tire circumferential direction so as to sandwich the tire circumferential direction. The kerf 4 is prevented from opening due to external force when cornering or braking,
The occurrence of stone trapping and uneven wear of the block 5 are prevented.

The pitch length of the calf 4 in the tire circumferential direction is preferably 10 to 40% of the tread development width. 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 bent shape as shown in FIGS. 1, 3 and 4, and may be a linear shape as shown in FIGS. 5 and 6.

[0015]

【Example】

Example 1: ( Two types of uneven wear (shoulder
It means that neither
The tire size is 11R22.5 14PR, the tread development width TDW is 220 mm, and the depth of the main groove is 15 mm.
1, the tire 2 of the present invention as shown in FIG. 12, the conventional tire 1, and the conventional tire 2 were manufactured. Invention Tire 2
The kerf has an angle of 60 ° with respect to the tire circumferential direction and a depth of 6 mm. Further, the groove width of the outermost main groove of the conventional tire 2 is set to 1/3 of that of the innermost main groove of the vehicle.

When the uneven wear resistance (shoulder wear, shoulder drop wear) of these tires was tested by the following evaluation method, the results shown in Table 1 were obtained. Uneven wear resistance evaluation method a) Shoulder wear A tire (test tire) filled with a pneumatic pressure of 7 kg / cm ² (2-
(D. 4th car) mounted on the front wheels and run 60,000km on a general road, then measure the groove depth of each groove to determine the wear amount (mm) of the outermost main groove and the innermost main groove. Evaluation was made based on the difference from the wear amount (mm). b) Shoulder drop wear After running under the same conditions as in the shoulder wear evaluation method, the shoulder step difference t (mm) (see FIG. 11) was measured.

[0017] Example 2: Tire size 11R22.
5 14PR, tread development width TDW 220mm, main groove depth 15mm, except that the tread patterns are shown in FIG. 7, FIG. 8, FIG. 9, FIG. 10, and FIG. Seven kinds of tires of the present invention tires 1 and 2, the comparative tires 1 to 5 and the conventional tire 3 as shown in Table 2 were manufactured.

In addition to the same shoulder wear test as in Example 1, these eight types of tires were tested for heel and toe wear and steering stability by the evaluation method described below, and the results shown in Table 2 were obtained. .. Heel and toe wear evaluation method: In the above shoulder wear evaluation test, the amount of step difference (mm) before and after the kerf-provided portion in the forward and backward directions was evaluated.

Steering stability evaluation method: Tires were mounted on all wheels of the above vehicle, and five panelists (test drivers) were used on a test course to test lane change in each speed range, steady turning test, and acceleration response test. Feeling was evaluated for the steering stability when the vehicle was operated. Evaluation result is 10
It was scored by the point method and evaluated by the average value of 5 panelists.

[0020] (Note) Numerical values of the tires 1 and 2 of the present invention in the section of rib mean the number of ribs counted from the outermost side when mounted on a vehicle. In addition, in the term of the depth of the kerf, a plurality of numbers are described (the tire 1 of the present invention) indicates the depth in the order from the outermost rib to the inner rib when the vehicle is mounted.

As can be seen from the results in Table 1, the tires 1 and 2 of the present invention have improved uneven wear resistance (shoulder wear) as compared with the conventional tire 1, but the steering stability remains at the same level. ing. Further, the tire 1 of the present invention in which the groove depth of the kerf is shallower in order from the outermost side to the inner side of the vehicle is superior in shoulder wear resistance as compared with the tire 2 of the present invention having the same depth. Also, the comparative tires 2, 3, and 5 in which the kerf angle is out of the range of 40 ° to 80 ° and the groove depth of the kerf is large have heel and toe wear. Further, the comparative tire 4 having a shallow kerf groove depth does not have sufficient shoulder wear resistance.

[0022]

As described above, according to the present invention, at least the ribs located on the outermost side of the vehicle at the time of mounting the vehicle and the ribs adjacent to the ribs are provided with a plurality of kerfs so as to traverse them, and are divided into a plurality of blocks. Since the rigidity of the outer ribs of the vehicle is reduced, uneven load such as shoulder wear is prevented by releasing the load concentrated on the outer ribs during cornering. Moreover, even though the rib rigidity is reduced, the depth of the kerf is set within the range of 20 to 70% of the depth of the main groove, and the angle of the kerf is set within the range of 40 to 70 relative to the tire circumferential direction.
Since the block is in the range of 80 °, it maintains a proper rigidity as a block, and since the groove width of the kerf is 1.5 mm or less, the blocks come into contact with each other to suppress the load, so a suitable rigidity as a rib Maintaining the value does not reduce the driving stability.

[Brief description of drawings]

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

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

FIG. 3 is a plan view of a tread portion according to another embodiment of the present invention.

FIG. 4 is a plan view of a tread portion according to still another embodiment of the present invention.

FIG. 5 is a plan view showing a tread portion of a tire according to another embodiment of the present invention partially broken away.

FIG. 6 is a plan view showing a tread portion of a tire according to still another embodiment of the present invention with a part thereof cut away.

FIG. 7 is a plan view of a tread pattern according to another embodiment of the present invention.

FIG. 8 is a plan view of a tread pattern according to another embodiment of the present invention.

FIG. 9 is a plan view of a tread pattern according to another embodiment of the present invention.

FIG. 10 is a plan view of a tread pattern according to another embodiment of the present invention.

FIG. 11 is a plan view of a tread pattern of a conventional tire.

FIG. 12 is a plan view of a tread pattern of another conventional tire.

FIG. 13 is an explanatory view showing shoulder wear of a tire.

FIG. 14 is an explanatory diagram showing shoulder wear of a tire.

[Explanation of symbols]

 1 Tread 2 Main groove 3 Rib 4 Calf 5 Block 6 Belt layer 7 Reinforcing layer 8a, 8b, 8c Tension layer 9 Fine groove

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B60C 11/12 B 8408-3D D 8408-3D

Claims (1)

[Claims] 1. A heavy-duty pneumatic radial tire in which a plurality of main grooves extending in the tire circumferential direction are provided on a tread surface, and a tread pattern based on a rib pattern composed of a plurality of ribs divided by the main grooves is provided. Among the plurality of ribs, at least the ribs located on the outermost side of the vehicle when the vehicle is mounted and the ribs adjacent to the ribs are provided with a plurality of kerfs so as to cross these, and are divided into a plurality of blocks, and the groove of the kerf is formed. A heavy-duty pneumatic radial tire having a width of 1.5 mm or less, a depth of the kerf in the range of 20 to 70% of the main groove depth, and an angle of the kerf with respect to the tire circumferential direction in the range of 40 to 80 °. ..