JPH11321239A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the removal life of a tire by delaying the progress of cupping partial wear generated by the local wear of a rib developed from step wear and river wear in a pneumatic radial tire with a rib pattern. SOLUTION: Closed sipes 22 extended inclining in the cross direction and circumferential direction of a tire are arranged at a shoulder rib 18 being spaced in the circumferential direction of the tire. When an erroded tip part of local wear developed from step wear and river wear reaches the sipe 22, wear energy is concentrated on a sipe edge 24 high in ground pressure and hard to slip so as to temporarily reduce wear in vicinity and to delay the progress of cupping partial wear.

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 having a rib pattern.
The present invention relates to a heavy-duty pneumatic radial tire used for long-distance running trucks and buses mainly for high-speed continuous running.

[0002]

2. Description of the Related Art Tires used for long-distance running trucks and buses mainly driven by high-speed continuous running extend the life of the tire due to a decrease in the wear rate of the tire itself, while increasing the tread surface. Uneven wear is a factor in early removal. In particular, such uneven wear is serious in a tire having a rib pattern used for a steering wheel. For this reason, conventionally, as shown in FIG. 8, a narrow groove 102 extending in the circumferential direction is provided at the outer end of the shoulder rib 101, thereby preventing step wear, which is uneven wear in which the shoulder rib is eroded from the outer end. That has been done.

[0003] The step wear is a result of the outer end of the shoulder rib being roundly worn by the side force received when entering the road surface, and the worn rib end being constantly worn by the slip force at the time of exiting the road surface. There is uneven wear in which a level difference is generated almost uniformly over the entire circumference of the tire.

[0004] The step wear is composed of the narrow groove 102.
Although it cannot be completely prevented depending on the situation, it still occurs, but its progress can be greatly reduced.
However, as the erosion speed of the step wear decreases, the cupping phenomenon in which uneven wear locally develops due to non-uniformity on the circumference of the tire becomes remarkable, causing a problem that the step wear progresses to cupping uneven wear.

[0005] That is, the stepware is shown in FIG.
Is characterized in that the ribs 101 are substantially uniformly eroded from the outer ends of the shoulder ribs 101 in the tire circumferential direction (in the figure, a hatched area M indicates a worn portion. The same applies hereinafter). ), Since there is no problem in running until the entire surface of the shoulder rib 101 is eroded and the shoulder is worn down, if it is only that, the tire is not necessarily removed early. However, since the tires are not uniform on the circumference, wear is locally promoted due to variations in contact pressure and the like, and as shown in FIG. 8B, the local wear becomes convex from the wear surface of the step wear. As shown in FIG. 8C, such local wear becomes cupping uneven wear that reaches the main groove 103. When the shoulder ribs 101 are locally eroded by cupping in this way, the steering wheel vibrates during high-speed running, which leads to early removal of the tire.

[0006] In addition, as shown in FIG. 9 (a), depending on the type of tire, river wear that erodes from the inside of the shoulder rib 101 occurs in the step wear that erodes from the outside of the shoulder rib as described above. Also,
This riverware is also similar to the stepware in FIG.
As shown in (b) and (c), there is a problem that the cupping develops uneven wear and leads to early removal of the tire.

Accordingly, an object of the present invention is to delay the progress of uneven cupping wear caused by local wear of a rib from step wear or river wear, and to prolong the tire removal life.

[0008]

As described above, in a tire having a rib pattern, step wear or river wear generated on the rib develops into localized wear due to unevenness on the tire circumference. However, the wear energy consumed in such local wear is limited, and if this energy can be locally consumed, uneven wear in the vicinity is reduced.

Therefore, the pneumatic radial tire of the present invention provides a pneumatic radial tire in which a tread portion is divided into a plurality of ribs by a plurality of main grooves extending in the tire circumferential direction in order to effectively consume such wear energy.
At least one rib is provided with a sipe at an interval in the tire circumferential direction, and the sipe extends obliquely in the tire width direction and the circumferential direction, and both ends thereof are terminated in the rib. It is characterized by the following.

In this tire, step wear and river wear develop into local wear, and when the eroded tip reaches the sipe row in the rib, the contact energy is high and the wear energy is concentrated on the sipe end which is difficult to slip. The wear in the vicinity is temporarily reduced. As a result, the progress of cupping uneven wear can be delayed, and the removal life of the tire can be extended. In particular, since the sipe is inclined with respect to the tire width direction, that is, the traveling direction of the cupping uneven wear, the sipe is longer than in the case where the sipe is provided in parallel with the tire width direction, and the delay effect is obtained over a long period of time. With
Wear energy can be more effectively consumed by the edge effect at the sipe end.

In the above, as described in claim 2,
It is preferable that the sipe is formed in a curved shape that extends while being curved and inclined in the tire width direction and the circumferential direction.

By bending the sipe in this way, it is possible to prevent the sipe from opening due to growth at the time of filling the internal pressure of the tire and to generate a step, and the sipe length is reduced by the curvature, as compared with the case where the sipe is straight. The delay effect can be obtained over a longer period of time.

According to a third aspect of the present invention, at least one of the outer end and the inner end of the sipe is located at the other end as the lower end in the sipe depth direction is located at the other end. Preferably, the sides are inclined with respect to the tire radial direction.

In this case, when local wear progresses from one end to the other end of the sipe, the one end moves to the other end as the wear progresses. That is, since the sipe end can follow the progress of the local wear, the effect of delaying the progress of the cupping uneven wear can be continuously exerted.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a partial plan view of a tread portion 10 of a heavy duty pneumatic radial tire according to an embodiment of the present invention, and FIG. FIG. 2 is a partial perspective view of the tread portion 10.
In the drawings, CL indicates a center line of the tread portion 10.

The tread portion 10 of the tire is divided into five ribs (a center rib 14, an intermediate rib 16, and a shoulder rib 18) by four wide main grooves 12 extending continuously in the tire circumferential direction. . The outermost two shoulder ribs 18 of these ribs are provided with a narrow groove 20 extending in parallel with the grounding end 11 near the outer end thereof, that is, near the grounding end 11 of the tread portion 10. ing. The narrow groove 20 is formed at substantially the same depth as the main groove 12.

The shoulder ribs 18 are formed with a single row of sipe rows in which a large number of thin sipe 22 are arranged at predetermined intervals m in the circumferential direction over the entire circumference of the tire. The sipe 22 is a closed sipe extending inclining in the tire width direction and the circumferential direction. That is, the sipe 22 is formed so as to be inclined in the tire circumferential direction by a predetermined angle θ with respect to the tire width direction, and both ends thereof, that is, the outer end 24 and the inner end 26 terminate in the shoulder rib 18. ing.

Here, the inclination angle θ is an angle between a line connecting both ends 24 and 26 of the sipe 22 and the tire width direction, and is preferably 5 ° to 45 °.

The distance between the ends 24 and 26 of the sipe 22 in the tire width direction, that is, the sipe formation width Ws is preferably 50 to 75% of the width Wr of the shoulder rib 18. In the case where the narrow groove 20 is provided in the ground plane of the shoulder rib 18 as in the present embodiment, Wr is a rib width excluding the narrow groove 20, and the narrow groove 20 is provided in the ground plane as described later. If not, the full width of the contact surface of the rib shall be used.

Also, the shoulder rib 1 from the end of the sipe 22
The distance We to the eight ends is preferably 10 to 40% of the width Wr of the shoulder rib 18, both the distance We1 from the outer end 24 and the distance We2 from the inner end 26. We1 and We2 may have the same value or different values. Note that We1 is the shoulder rib 18 as in the present embodiment.
When the narrow groove 20 is provided in the ground plane, the distance from the outer end 24 to the narrow groove 20 is set. As described later, when the narrow groove 20 is not provided in the ground plane, the distance from the outer end 24 to the tread ground end is set. The distance to 11 is assumed.

Further, the interval m of each sipe 22 in the tire circumferential direction is 0.6 to less than the circumferential length of the shoulder rib 18.
Preferably it is 1.5%. The depth of cut of the sipe 22 is set to 63 to 89% of the depth of the main groove 12. In addition, the cut width of the sipe 22 is usually 0.3-1.
0 mm.

The sipe 22 may be straight, but in this embodiment, the sipe 22 is gradually curved in the circumferential direction of the tire in order to prevent the sipe 22 from opening and causing a step due to the growth of the tire at the time of filling the internal pressure. It is formed in a curved shape.

As shown in FIG. 1B, this sipe 22
Has a substantially inverted trapezoidal cross-sectional shape (a cut surface shape in the sipe depth direction). And the inner cut side 29 rises from the deepest part of the sipe substantially parallel to the tire radial direction. As a result, the outer end 24 of the sipe 22 is located closer to the inner side in the tire width direction as the sipe depth direction is lower.

In the tire according to the present embodiment, the step wear generated at the outer end of the shoulder rib 18 develops into local wear at an uneven portion on the tire circumference, and FIG.
As shown in FIG. 5, when the erosion front end reaches the row of sipes 22 in the shoulder rib 18, the contact energy is concentrated on the outer end 24 of the sipe 22 where the contact pressure is high and the slip is difficult.
The wear in the vicinity is temporarily reduced. In particular, Sipe 2
2 is provided at an angle, so that wear energy is effectively consumed by the edge effect at the outer end 24 of the sipe 22. As such, the erosion tip must advance between the sipe 22 avoiding the outer end 24 of the sipe 22, thereby delaying the progress of local wear.

Thereafter, as shown in FIG. 3 (b), the erosion front end of the local wear advances inward beyond the outer end 24 of the sipe 22, but the outer cut side 28 in the cross-sectional shape of the sipe 22 is formed. As described above, the outer end 24 of the sipe 22 moves inward with the progress of wear because the outer end 24 is inclined with respect to the tire radial direction. That is, as shown in FIG. 5, when the sipe 22 is worn down to the dotted line N,
To the position in the width direction of the tire. in this way,
Since the outer end 24 of the sipe 22 follows the progress of the local wear, the above-described delay effect can be maintained, and therefore, FIG.
As shown in (c), the local wear is substantially the same as the progress of the step wear, and the tire removal life is extended.

As shown in FIG. 4, since the sipe 22 is not parallel to the tire width direction but is inclined, the length L of the sipe 22 can be longer than the sipe formation width Ws.
Therefore, the above-mentioned delay effect can be obtained over a long period. Further, in the present embodiment, since the sipe 22 is formed not in a straight line but in a curved shape, the above-described delay effect can be obtained for a longer period.

Further, since the sipe 22 is a closed sipe, not only such step wear but also river wear eroding from the inner end of the shoulder rib 18 can prevent the uneven wear of the cupping due to the local erosion. It can be delayed by the edge effect of the inner end 26 of 22. In addition, the rigidity of the shoulder rib 18 is not significantly reduced unlike the open sipe.

In the present embodiment, as the cross-sectional shape of the sipe 22, the inner cut side 29 is substantially parallel to the tire radial direction and the outer cut side 28 is inclined, but the inner cut side 29 is also inclined. The sipe 22 may have a substantially V-shaped cross section. In this case, both the outer end 24 and the inner end 26 of the sipe 22 can be moved following the wear, and the effect of delaying the progress of the local wear for both the step wear and the river wear can be maintained for a long time. it can.

As shown in FIG. 6, both the outer cut side 28 and the inner cut side 29 may be raised substantially parallel to the tire radial direction, and the cross-sectional shape of the sipe 22 may be substantially U-shaped. . In this case, as shown in FIG. 7 (a), when the erosion front end of the local wear developed from the step wear reaches the sipe 22 in the shoulder rib 18, the outer end of the sipe 22 similarly to the above-described embodiment. 24, the wear energy is concentrated and the wear in the vicinity is temporarily reduced,
As a result, the progress of local wear is delayed. However, since the cross-sectional shape of the sipe 22 is substantially U-shaped, as shown in FIG. 5, the outer end 24 of the sipe 22 does not move inward in the tire width direction following the progress of wear, and is shown at 24b. Stay in position. Therefore, as shown in FIG. 7 (b), cupping uneven wear progresses, and if a step is formed due to wear, the above-described delay effect is eliminated, and as shown in FIG. 7 (c), the progress is temporarily made at the sipe outer end 24. The delayed cupping uneven wear proceeds in the tire width direction.

In the above embodiment, the narrow groove 20 is provided on the contact surface of the shoulder rib 18 in order to reduce the wear speed of the step wear. The same effect can be obtained even if it is not necessarily in the ground plane, but is provided outside the ground plane, that is, on the side wall of the tread portion 10. In the present invention, a configuration in which the narrow groove 20 is not provided may be adopted.

The sipe 22 is provided with the shoulder rib 18.
However, the present invention is not limited to this, and it may be provided on other ribs such as the intermediate rib 16 and the center rib 14 that cause uneven wear of the cupping from the riverware.

[0033]

[Examples] Tire size: 285 / 75R24.5 14P for both Examples 1 and 2 and Comparative Example 1
R, rim size: 24.5 × 8.25 ″, tire pressure:
At 760 kPa, the abrasion state after running 30,000 km on the drum was examined with a 1.7 m diameter drum tester. The test conditions were as follows: Load: TIRE & RIM ASSO
CIATION (TRA) 100%, slip angle: +
0.1 °, camber angle: -0.05 °, speed 80km
/ H.

The structure of the tread portion is as shown in Table 1. In the first embodiment, the shoulder rib 18 shown in FIG.
In the second embodiment, a closed sipe 22 inclined in the shoulder rib 18 shown in FIG. 6 is used. A U-shaped one was used. In Comparative Example 1, a sipe was not provided in the shoulder rib shown in FIG.

The results are shown in Table 1. In Table 1, the "maximum width" in the column of "wear state" refers to the maximum width of wear, that is, the distance from the tip of the erosion tip located closest to the inside in the tire width direction to the tread contact edge 11. .

[0036]

[Table 1] As shown in Table 1, in Example 1, cupping uneven wear did not occur, and in Example 2, only the initial state of cupping uneven wear was recognized. In contrast, Comparative Example 1
In this case, uneven cupping wear was greatly advanced.

[0037]

According to the pneumatic radial tire of the present invention, if step wear or river wear develops into local wear, and the eroded tip reaches the sipe in the rib,
Since the wear energy concentrates on the sipe end where the contact pressure is high and the slip is difficult, the wear near the sipe end is temporarily reduced. As a result, the progress of cupping uneven wear can be delayed, and the removal life of the tire can be extended. In particular, the sipe,
Since the sipe is inclined with respect to the direction of cupping uneven wear, the sipe is longer than in the case where it is provided in parallel, so that the delay effect can be obtained over a long period, and the consumption of wear energy due to the edge effect at the sipe end. It can be used more effectively.

[Brief description of the drawings]

FIG. 1 shows a tread portion of a pneumatic radial tire according to an embodiment of the present invention, (a) is a partial plan view thereof,
(B) shows a partial cross-sectional view.

FIG. 2 is an enlarged perspective view of a main part of the tread portion.

FIGS. 3A to 3C are partial plan views showing the progress of wear of the tread portion.

FIG. 4 is an enlarged plan view of a main portion of the tread portion for showing an effect of delaying progress of local wear of the tread portion.

FIG. 5 is a diagram showing a cross-sectional shape of a sipe.

FIG. 6 is a partial cross-sectional view of a tread portion showing a modified example of a cross-sectional shape of a sipe.

FIGS. 7A to 7C are partial plan views showing the progress of wear of the tread portion in the modified example.

8 (a) to 8 (c) are partial plan views of a tread portion showing a state of progress of local wear from step wear in a conventional tire, and FIG. 8 (d) is a partial cross-sectional view of the tread portion. .

FIGS. 9 (a) to 9 (c) are partial plan views of a tread portion showing a progress state of local wear from river wear in a conventional tire.

[Explanation of symbols]

 Reference Signs List 10 tread portion 12 main groove 18 shoulder rib 22 sipe 24 outer end of sipe 26 inner end of sipe 28 outer cut side in sipe cross-sectional shape 29 sipe cross-sectional shape Inner cut side M at ... wear part

Claims (3)

[Claims] 1. A pneumatic radial tire in which a tread portion is divided into a plurality of ribs by a plurality of main grooves extending in a tire circumferential direction, wherein at least one rib has sipes disposed at intervals in the tire circumferential direction. The pneumatic radial tire, wherein the sipe extends obliquely in the tire width direction and the circumferential direction, and both ends of the sipe end in the rib. 2. The pneumatic radial tire according to claim 1, wherein the sipe is formed in a curved shape that extends while being curved and inclined in a tire width direction and a circumferential direction. 3. The sipe cross-sectional shape has a cut edge on one side with respect to the tire radial direction such that at least one of the outer end and the inner end of the sipe is located on the other end as the sipe depth direction is lower. The pneumatic radial tire according to claim 1, wherein the tire is inclined.