JP3509363B2 - Pneumatic radial tire for heavy loads - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire mounted on a heavy-duty vehicle such as a truck or a bus, and particularly to prevent uneven wear of the second rib or block row from the outermost side of the tread surface. The present invention relates to a heavy duty pneumatic radial tire.

[0002]

2. Description of the Related Art As a tread pattern of a heavy duty pneumatic radial tire, a rib-based pattern having excellent wear resistance is often used. However, in this rib-based pattern, the lateral force generated at the time of turning concentrates the friction energy particularly on the edge portion of the rib located second from the outermost side, and wear progresses faster than other portions, so that the rib punch and There is a drawback that uneven wear such as railway wear is likely to occur.

The applicant of the present invention has previously proposed, as a measure for suppressing uneven wear generated in the second rib in such a heavy-duty pneumatic radial tire, along the shoulder side edge portion of the second rib. We have proposed a technology to prevent wear from spreading to other ribs by providing thin ribs that extend in the tire circumferential direction through narrow grooves and by concentrating the friction energy during turning on these thin ribs (special features). Kaihei 5-24
6213).

However, the effect of preventing uneven wear by the above technique is that the end portions of the thin ribs are easily deformed when a lateral force is applied,
It can only be obtained by producing a smooth slip on the road surface. Therefore, it is effective when the lateral force generated during turning is large, such as when traveling at high speed or with a full load, but it runs at a relatively low speed or runs with a light load. In this case, there is a problem that a sufficient uneven wear suppressing effect cannot be obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heavy-duty pneumatic radial tire which can obtain an excellent uneven wear suppressing effect even when traveling at low speed or traveling with a light load. Especially.

[0006]

According to the present invention, a belt layer composed of a plurality of plies is arranged on the outer periphery of a carcass layer in a tread portion, and a plurality of main grooves extending in the tire circumferential direction are provided on the surface of the tread portion. In a heavy duty pneumatic radial tire having a plurality of ribs or block rows divided into these main grooves, in the shoulder side edge portion of the second rib or block row from the outermost side to the inner side of the tread portion,
A thin rib extending in the tire circumferential direction at the same height as the rib or block row is provided through the narrow groove, and
Chamfered edges of Yoruda side (tire outside), and a virtual width W ₂ of the previous chamfer Said sub ribs to the width W ₁ of the rib or block rows adjacent Said sub ribs, W ₂ = (0 .1 to 0.5) W ₁ is set.

As described above, the second rib from the outermost side or the shoulder side edge of the block row is provided with the thin ribs of the same height through the thin grooves, so that the friction energy is concentrated on the thin ribs. Of the ribs or block rows are prevented, uneven wear of the ribs or block rows is prevented, and the shoulder side (outside of the tire) of the thin ribs.
Since the rigidity of the tip is reduced by chamfering the edge of the, even if the lateral force at the time of turning is relatively small, the tip of the thin rib easily deforms and is smooth against the road surface. since a slip occurs to facilitate centralization of the friction energy into the narrow rib. Therefore, an excellent uneven wear suppressing effect is exhibited even when the lateral force at the time of low-speed traveling or light weight loading is small.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below based on the embodiments shown in the drawings. 1 and 2 show a tread portion of a heavy duty pneumatic radial tire according to the present invention. Four main grooves 2 are provided in the tire circumferential direction on the surface of the tread portion 1, and the center ribs 3 are formed by these main grooves 2.
The middle ribs 4 and 4 and the outermost shoulder ribs 5 and 5 are divided on both the left and right sides. The main groove 2 is formed to have a groove width of 10 to 20 mm, and the number thereof may be an even number or an odd number, and is not particularly limited.

In the illustrated example, a single carcass layer 10 is provided on the inside of the tire, and both ends of the carcass layer 10 extend to bead portions through sidewall portions (not shown). The carcass layer 10 may have two or more layers if necessary. On the outer periphery of the carcass layer 10, a belt layer 9 of a plurality of plies having a steel cord or the like as a reinforcing cord is provided.
The plurality of plies causes the reinforcing cords to intersect each other between the plies.

The middle rib 4 located second inward from the outermost shoulder rib 5 of the tread is provided with a thin rib 7 extending in the tire circumferential direction through a narrow groove 6 at the shoulder edge. There is. Below the thin rib 7, the outermost layer 9t of the belt layer 9 extends so as to overlap. As shown in the enlarged view of FIG. 3, the thin rib 7 has a chamfer 8 at the edge portion on the shoulder side (outside of the tire),
The width of the end portion is reduced to reduce the rigidity. On the other hand, on the root side of the thin rib 7, the rigidity is further increased by the outermost layer 9t of the belt layer 9 extending downward as described above.

FIGS. 4 and 5 show a tread portion of a heavy duty pneumatic radial tire according to another embodiment of the present invention. In this embodiment, the center rib 3 and the middle rib 4 in the embodiment of FIGS. 1 and 2 are separated into a large number of blocks 13a and 14a by a large number of lateral grooves 11 provided at a predetermined pitch in the tire circumferential direction. The difference is that rows 13 and 14 are provided, and the other parts have substantially the same configuration.

That is, in the block row 14 located second from the outermost shoulder rib 5, the thin rib 7 extending in the tire circumferential direction via the narrow groove 6 at the shoulder side edge portion.
Is formed, and the thin rib 7 is chamfered at the edge. The outermost layer 9t of the belt layer 9 extends below the thin rib 7 so as to overlap each other.

In the present invention, the shape of the chamfer 8 applied to the thin rib 7 may be an oblique linear cutout as shown in FIG. 3, but an arcuate shape having a radius R as shown in FIG. You may make it cut out. In the case of the chamfer 8 having an arc shape, the upper end thereof may be connected to the upper surface of the thin rib 7 in a tangential shape which does not form an edge as shown in FIG. 6, or intersect so as to form an edge. May be connected as follows.

It is important that the chamfer 8 is preferably provided on the shoulder side edge of the thin rib 7 .

Moreover, since the tip of the fine rib 7 has a small rigidity due to the chamfering 8, even when the lateral force at the time of turning is small, the fine rib 7 is easily deformed and slips, so that the friction energy is concentrated on the fine rib 7. To ensure. Therefore, an excellent effect of suppressing uneven wear is exhibited even when traveling at low speed or when being loaded with light weight. In the present invention, the upper surface width (virtual width) W ₂ of the thin rib 7 before chamfering 8 is 0.1 to 0.5 times the width W ₁ of the middle rib 4 or the block row 14 adjacent to the thin rib 7 [. That is, it is necessary to set W ₂ = (0.1 to 0.5) W ₁ ]. If the imaginary width W ₂ of the thin rib 7 is smaller than 0.1 W ₁ , the rigidity of the thin rib 7 itself is too small to obtain the effect of sacrificing wear, and conversely, it is smaller than 0.5 W ₁ . If it is too large, the rigidity of the thin rib 7 becomes too high, and it becomes difficult to deform against the lateral force, so that it becomes difficult to concentrate the friction energy on the thin rib 7.

The friction energy with respect to the thin rib 7 is expressed as a physical quantity proportional to the product of the ground contact pressure and the slip amount. Therefore, in the present invention, in order to further enhance the uneven wear preventing effect obtained by sacrificing the wear of the thin ribs 7, it is necessary to devise to increase the friction energy as much as possible. From this point of view, when the outermost layer 9t of the belt layer 9 is extended to the lower side of the thin rib 7 as described above, the rigidity of the root portion of the thin rib 7 is increased, thereby increasing the ground contact pressure of the thin rib 7. This is advantageous because it can be performed. In addition, the upper surface width W ₃ of the thin rib 7 after the chamfering 8 is 0 to the virtual width W ₂ before the chamfering.
It is also advantageous to multiply (1/3) times [that is, W ₃ = (0 to 1/3) W ₂ ].

When the upper surface width W _{3 is set} to 1/3 or less of the virtual width W ₂ , the flexural rigidity of the upper ends of the thin ribs 7 is reduced,
This is because the amount of slippage on the road surface will increase. If the flexural rigidity of the upper end of the thin rib 7 is reduced,
Even when the lateral force at the time of turning is small, it is easily deformed to cause slippage, so that it becomes possible to suppress uneven wear even when traveling at low speeds or when lightweight loading.

Further, the groove depth d of the fine groove 6 also changes the rigidity of the fine rib 7 and affects the magnitude of the ground contact pressure. Therefore, the groove depth d of the fine groove 6 is 1/3 to 1 times the groove depth D of the main groove 2 adjacent to the fine groove 6 [that is, d = (1/3 to 1) D].
], And more preferably d = (1/3 to
0.8) D should be set. When the groove depth d of the narrow groove 6 becomes larger than the main groove depth D, the rigidity of the thin rib 7 decreases significantly, and it is not possible to expect improvement of the ground contact pressure, but also the durability of the thin rib itself decreases. On the other hand, if the groove depth d is smaller than D / 3, the rigidity of the thin rib 7 becomes too high and slippage is less likely to occur, so that the effect of concentrating friction energy on the thin rib is reduced.

Further, in the tire of the present invention, the groove width W ₄ of the fine groove 6 is 0.5 to 1 times the virtual width W ₂ of the fine rib 7 before chamfering (that is, W ₄ = (0.5 ~ 1) W ₂ ]. If the groove width W ₄ is smaller than 0.5 W ₂ , cracks are likely to occur at the groove bottom of the thin groove 6, and if it is larger than the virtual width W ₂ of the thin rib 7, the durability of the thin rib is reduced. . The groove width W ₄ of the narrow groove 6 is more preferably set in the range of 0.5 to ₄ mm.

[0020]

【Example】

Example 1 The tire size is 11R22.5 14PR, the tread pattern is shown in FIG. 2, the heights of the thin ribs are the same as the heights of the other ribs, and the shoulder side end portion has an arcuate chamfer (radius as shown in FIG. 6). R = 2 mm), the ratio W ₃ / W ₂ of the upper surface width W ₃ after chamfering to the virtual width W ₂ before chamfering is 0, and the ratio W of the groove width W ₄ of the narrow groove to the virtual width W ₂ of the narrow rib _Four
/ W ₂ is 0.7, the ratio d / D of the groove depth d of the fine groove to the main groove depth D is 1.0, and the outermost layer of the belt layer is not extended to the lower side of the fine rib. Inventive tires 1 to 3 and comparative tires 1 and 2 which have a common configuration and have different ratios W ₂ / W ₁ of the virtual width W ₂ of the thin rib to the rib width W ₁ of the middle rib as shown in Table 1, respectively. Were made respectively.

As a reference for comparison, a conventional tire 1 having the same tire size, the same tread pattern, and a structure in which the thin ribs are not chamfered was manufactured. With respect to these six types of tires, the uneven wear resistance of the tread was measured by the following test method, and the results shown in Table 1 were obtained. (Uneven wear resistance) Vehicle with a loading capacity of 10 tons (2-2.D)
The test tires are mounted on the front two axles of the vehicle, and under the load of 50% of JATMA standard load (1350 kg / piece), 90% or more of the general pavement is run as a running pattern.
The uneven wear amount of the middle rib was measured after traveling about 50,000 km without changing the position.

The uneven wear amount was evaluated by visually observing the tread surface and ranking the railway wear generated on the middle rib and the size of the rib punch into three categories, large, medium and small, respectively.
It carried out according to each incidence. The evaluation result is expressed by an index with the conventional tire being 100, and the larger the index, the better the uneven wear resistance. From Table 1, it is understood that the tires 1 to 3 of the present invention all have improved uneven wear resistance as compared with the conventional tire.

Example 2 The tire size is 11R22.5 14PR, the tread pattern is as shown in FIG. 5, the height of the thin ribs is the same as the height of the other block rows, and the shoulder side end is tapered as shown in FIG. Chamfering is performed, and the ratio W ₂ / W ₁ to the virtual width W ₂ of the thin rib and the width W ₁ of the block row adjacent thereto is 0.
3. Ratio of narrow groove width W ₄ to narrow rib virtual width W ₂ W ₄
/ W ₂ to the common configuration points to 0.7, the ratio of the top width W ₃ after chamfering against narrow ribs virtual width W ₂ W ₃ / W _2,
A tire of the present invention in which the ratio d / D of the groove depth d of the fine grooves to the main groove depth D and the presence / absence of extension of the outermost layer of the belt layer to the lower side of the fine ribs are different as shown in Table 2. 4-9 were manufactured respectively.

As a reference for comparison, a conventional tire 2 having the same tire size and the same tread pattern, in which the thin ribs are not chamfered and the outermost layer of the belt layer is not extended below the thin ribs, is manufactured. . For these tires,
The uneven wear resistance of the tread was measured by the same test method as in Example 1, and the results shown in Table 2 were obtained.

[0025] From Table 2, it is understood that the tires 4 to 9 of the present invention all have improved uneven wear resistance as compared with the conventional tire. Further, in the tire of the present invention, compared with the case where the belt layer outermost layer does not extend below the thin ribs, the extended one is more excellent in uneven wear resistance, and the thin ribs after chamfering Width W
It can be seen that ₃ is less than 1/3 of the width W ₂ before chamfering, and the effect of uneven wear resistance is high.

[0026]

As described above, the heavy-duty pneumatic radial tire of the present invention can be operated from the outermost side even when traveling at a low speed or with a small loaded weight.
Uneven wear of the rib or block row located at the second position can be suppressed well.

[Brief description of drawings]

FIG. 1 is a meridional sectional view showing a tread portion of an example of a pneumatic radial tire according to the present invention.

FIG. 2 is a development view showing a part of a tread surface of the tire.

FIG. 3 is an enlarged cross-sectional view of an essential part showing the vicinity of the thin rib of the tread part shown in FIG.

FIG. 4 is a meridional cross-sectional view showing a main part of a tread portion of another example of a pneumatic radial tire according to the present invention.

5 is a development view showing a part of the tread surface of the tire of FIG.

FIG. 6 is an enlarged sectional view of an essential part showing the vicinity of a thin rib of a tread part according to another embodiment .

[Explanation of symbols]

1 tread section 2 main groove 4 middle ribs (second rib from the outermost) 5 shoulder ribs 6 narrow groove 7 Fine ribs 8 chamfers 9 Belt layer 9t (belt layer) outermost layer 14 block rows (second outermost block row)

Continuation of front page (56) Reference JP-A-5-246213 (JP, A) JP-A-7-117413 (JP, A) JP-A-3-136906 (JP, A) JP-A-6-239109 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60C 11 / 04,11 / 06 B60C 11 / 12,11 / 03

Claims (3)

(57) [Claims] 1. A belt layer composed of a plurality of plies is arranged on the outer periphery of a carcass layer in a tread portion, a plurality of main grooves extending in the tire circumferential direction are provided on the surface of the tread portion, and a plurality of main grooves are divided into these main grooves. In a heavy-duty pneumatic radial tire having ribs or block rows, which is the same as the ribs or block rows via a narrow groove at the shoulder side edge of the second rib or block row from the outermost side to the inner side of the tread portion. A thin rib extending in the tire circumferential direction of the height is provided, and the edge of the thin rib on the shoulder side (outside of the tire)
Part chamfered, and virtual width W before the chamfering of Said sub ribs
_{2. The} pneumatic radial tire for heavy load, wherein _{2 is set} to W ₂ = (0.1 to 0.5) W ₁ with respect to the width W ₁ of the rib or block row adjacent to the thin rib. 2. The outermost layer of the belt layer extends below the thin ribs, and the chamfered upper surface width W of the thin ribs.
₃ is set to W ₃ = (0 to 1/3) W ₂ with respect to the virtual width W ₂ before chamfering, and the groove depth d of the narrow groove is set to the groove depth D of the main groove adjacent to the narrow groove. On the other hand, the pneumatic radial tire for heavy loads according to claim 1, wherein d = (1/3 to 1) D. 3. The groove width W _{4 of the} narrow groove is W ₄ = with respect to the virtual width W ₂ of the thin rib before chamfering.
The pneumatic radial tire for heavy loads according to claim ₂ , wherein (0.5 to 1) W ₂ is used.