JP2000016024A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the tire takeoff lifetime of a pneumatic radial tire having rib patterns by suppressing the cupping eccentric wear generated with rib wears locally from a step wear or ribber wear. SOLUTION: A shoulder rib 18 is equipped with a siping row 24 in which sipes 22 extending in the tire circumferential direction are provided linearly at a certain spacing in the tire circumferential direction, wherein when the erroding forefront of a local wear propagating from a step wear or ribber wear has attained the nearest part of the siping row 24, further propagation of the local wear across the width is hindered by the sipings 22 extending in the tire circumferential direction.

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 In tires used for long-distance running trucks and buses mainly composed of high-speed continuous running, tire life is extended due to a decrease in wear speed of the tire itself, while uneven wear of a tread surface is a factor of early removal. It has become. 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.
A thin groove 102 extending continuously 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.

[0004]

In this step wear, the outer end of the shoulder rib is worn round by a side force received when the outer end of the shoulder rib enters the road surface, and the end of the worn rib continuously receives the slip force at the time of exiting the road surface. It is caused by abrasion, and is uneven wear in which a level difference is generated almost uniformly over the entire circumference of the tire.

[0005] 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 reduced. However, as the erosion rate 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.

[0006] 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 tire is uneven on the circumference, the wear is locally promoted due to the variation of the contact pressure and the like, and as shown in FIG. Further, as shown in FIG. 8C, such local wear becomes cupping uneven wear reaching 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.

[0007] In contrast to the step wear eroded from the outside of the shoulder rib as described above, depending on the tire, as shown in FIG. As in the case of the stepware, this riverware also has a problem that it develops into uneven cupping wear as shown in FIGS. 9B and 9C, leading to early removal of the tire.

By the way, in order to prevent such uneven wear of the shoulder rib, it has been proposed to dispose a large number of sipes extending in the tire width direction on the shoulder rib at intervals in the tire circumferential direction. 61-23520
No. 5).

[0009] However, such a sipe in the width direction is effective for preventing step wear and river wear, but cannot provide a sufficient effect for uneven cupping wear.

[0010] This is because the stress acting on the tread portion is different between step wear and river wear and cupping. That is, step wear and river wear are generated due to stress acting in the tire circumferential direction, whereas cupping is caused due to stress acting in the tire width direction. In order for the sipe provided on the rib to exert an effect on uneven wear, the sipe must be formed perpendicular to the stress acting on the tread portion. In the conventional sipe extending in the width direction, since the sipe forming direction and the stress acting direction are perpendicular to the step wear and the river wear, the uneven wear suppression effect by the sipe is exhibited, but the However, the sipe forming direction and the acting direction of the stress are parallel, so that the sipe effect cannot be sufficiently exhibited.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to suppress uneven cupping wear caused by local wear of a rib by step wear or river wear, and to prolong the tire removal life.

[0012]

According to the pneumatic radial tire of the present invention, in 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, at least one rib has: At least one sipe row formed by arranging sipes extending in the tire circumferential direction in series at intervals in the tire circumferential direction is formed.

In this tire, when step wear or river wear develops into local wear, and the erosion front end approaches the sipe row, the sipe extending in the tire circumferential direction causes the local wear to further progress in the width direction. Is prevented, so that cupping uneven wear can be suppressed.

More specifically, the sipe extending in the circumferential direction is arranged perpendicularly to the stress acting in the tire width direction which causes cupping uneven wear, that is, the sipe forming direction and the stress acting direction. Are perpendicular to each other, so that the effect of suppressing uneven cupping wear due to sipes can be sufficiently exhibited.

[0015] The sipe row is, as described in claim 2,
It is preferable that the ribs are arranged in a region of 12 to 88% of the rib width.

[0016] This prevents the sipe from being eroded by step wear and river wear at an early stage of wear, and allows the sipe to effectively work to suppress uneven cupping wear.

Here, the rib width is defined as the width from the rib end to the narrow groove when a narrow groove extending continuously in the circumferential direction is provided at the end of the rib in order to delay the progress of the step wear or the river wear. Means the width of the rib excluding the distance of the rib, and when such a narrow groove is not provided, it refers to the entire width of the contact surface of the rib.

In the above, as described in claim 3,
It is preferable that the sipe row is formed in a concave portion depressed with respect to a rib contact surface.

By providing the sipe row in the recess and exposing the opening surface of the sipe on the grounding surface, it is possible to prevent stones from entering the sipe and cause rubber cut, that is, to prevent so-called stone biting. it can. In addition, since the sipes are hardly seen from the surface, the appearance is excellent.

[0020]

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

FIG. 1 is a partial perspective view of a tread portion 10 of a heavy-duty pneumatic radial tire according to one embodiment of the present invention. FIG. 2A is a partial plan view of the tread portion 10, and FIG. (B) is a partial vertical cross-sectional view of the tread portion 10, and FIG.
3 is an enlarged plan view of the sipe 22. FIG. 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 have narrow grooves 20 continuously extending in parallel with the grounding end 11 near their outer ends, that is, near the grounding end 11 of the tread portion 10. Is provided. The narrow groove 20 is formed at substantially the same depth as the main groove 12.

The shoulder ribs 18 form a sipe row 24 in which a number of sipe 22 which are thin notches extending in the circumferential direction of the tire are arranged in series at predetermined intervals m in the circumferential direction over the entire circumference of the tire. Have been.

In the present embodiment, the sipe row 24 is provided substantially at the center of the shoulder rib 18 in the width direction, that is, in the shoulder rib 1.
The distance Ws from the widthwise inner end of the shoulder rib 18 is the shoulder rib 18.
Are provided in one row in a region where the rib width Wr is 40 to 60%.

When the narrow groove 20 is provided in the ground plane of the shoulder rib 18 as in this embodiment, the rib width Wr is set to the width of the rib inside the narrow groove 20, and as described later, the rib width Wr is set in the ground plane. When the narrow groove 20 is not provided, the entire width of the contact surface of the rib 18 is set.

Here, the sipe row 24 is disposed in a region of 12 to 88% of the rib width Wr of the shoulder rib 18, that is, the distance Ws from the widthwise inner end of the shoulder rib 18 is: The width Wr of the shoulder rib 18 is 12 to
It is preferable to dispose it in the area where 88% is obtained. This is to prevent the sipe 22 from being eroded by step wear or river wear at an early stage of wear, and to effectively use the sipe 22 to suppress cupping uneven wear. From such a viewpoint, it is more preferable that the sipe row 24 is provided in a region of 25 to 75% of the rib width Wr of the shoulder rib 18.

However, depending on the market where the tire is used, as shown in FIG. 7, from the viewpoint of preventing the sipe 22 from biting stones, rather than disposing the sipe row 24 near the center of the shoulder rib 18, as shown in FIG. It may be desirable to provide sipe rows 24a, 24b near the inner end and the outer end, respectively. That is, in the example shown in FIG. 7, the sipe rows 24 a and 2 are arranged not in the center of the shoulder rib 18 in the width direction but in the rows near the inner end and the outer end.
4b is provided. In this case, the sipe row 2 near the inner edge
4a prevents the progress from the riverware to the cupping, and the sipe row 24b near the outer end acts to prevent the progress from the stepware to the cupping. In this case, the sipe row 24a near the inner end is the shoulder rib 1
The distance Wsa from the inner end in the width direction of No. 8 is 12 times the rib width Wr.
The sipe row 24b near the outer end is within the area of about 30%.
Is the distance Ws from the widthwise inner end of the shoulder rib 18.
It is preferable to provide each in a region where b is 70 to 88% of the rib width Wr.

The length L of the sipe 22 is preferably 0.06 to 0.6% of the circumference of the shoulder rib 18. This is because if the cutting depth D of the sipe 22 is taken into consideration when the cutting depth D is less than 0.06%, the current tire molding technology requires the use of a special material such as titanium in the tire molding mold. On the other hand, if it is larger than 0.6%, there is a tendency that the sipe 22 is used as a trigger to cause damage and that a decrease in rigidity tends to cause uneven wear around the sipe 22.

The distance m between each sipe 22 in the tire circumferential direction is 0.06 to 0.06 of the circumferential length of the shoulder rib 18.
It is preferably 0.6%, more preferably 0.1%.
06-0.3%. This is because, when the interval m between the sipe 22 arranged in the circumferential direction extremely exceeds the length L of the sipe 22, the eroded surface passes between the sipe 22, and the effect of preventing cupping cannot be sufficiently exhibited. Sipe interval m
Is preferably at most equal to the sipe length L. The reason for setting the content to be 0.06% or more is that sipe 22
Is the same as the case of the length L.

The cut depth D of the sipe 22 is set to 30 to 89% of the depth of the main groove 12. this is,
Since the river wear and the step wear are generated relatively early in the life of the tire, it is not necessary to provide the main groove 12 as deep as the depth of the main groove 12. It is because it cannot be demonstrated. In the case of a regular pavement rib tire, the main groove 1
This is because the TWI (Tread Wear Indicator) is exposed at 89% of the depth of the sipe 22, and it is not necessary to provide the sipe 22 deeper than this. In addition, the cut width Wc of the sipe 22 is usually 0.3 to 1.0 mm.

As shown in FIG. 3, both ends 22a of the sipe 22 are rounded, thereby suppressing the occurrence of rubber breakage.

The cross-sectional shape of the sipe 22 (the cut shape in the sipe depth direction) may be a rectangular shape in which the sipe length L is constant in the depth direction as shown in FIG.
As shown in FIG. 6, the sipe length L may be substantially triangular so that the sipe length L becomes shorter toward the bottom. This is because the uneven wear occurs and progresses at the initial wear stage up to 30% of the depth of the main groove 12, and the necessity of the sipe 22 decreases as the wear of the tread portion 10 progresses with running. By doing. Also, it is possible to prevent stone biting.

The sipe row 24 is formed in a concave portion 26 which is depressed with respect to the ground surface of the shoulder rib 18. The recess 26 is slightly wider than the width Wc of the sipe 22 and is formed in a groove shape with a shallow bottom, and extends continuously in the circumferential direction over the entire circumference of the tire. By providing the sipe rows 24 in the recesses 26 and exposing the opening surface of the sipe 22 to the ground surface, it is possible to prevent stones from entering the sipe 22 and causing rubber breakage. Further, since the sipe 22 is hardly seen from the surface, the appearance is excellent.

FIG. 5A shows the tire of the present embodiment.
As shown in FIG. 5, step wear M occurs at the outer end of the shoulder rib 18, and this step wear M is
As shown in FIG. 5 (b), when the erosion front end reaches the sipe row 24 at the uneven portion on the tire periphery and develops into local wear, as shown in FIG. The sipe 22 extending in the direction prevents the local wear from progressing to the cupping uneven wear.

As shown in FIG. 6A, a river wear M occurs at the inner end of the shoulder rib 18, and the river wear M has developed into a local wear in an uneven portion on the tire circumference. Even in this case, as shown in FIG. 6 (b), when the erosion tip reaches the sipe row 24, the sipe 22 extending in the circumferential direction as shown in FIG. The local wear is prevented from progressing to uneven cupping wear.

Here, the sipe 22 extending in the circumferential direction is used.
The effect of preventing progression to uneven cupping wear will be described.

In uneven wear such as step wear, river wear, and cupping, the eroded surface of uneven wear is formed in a direction (90 °) perpendicular to the stress acting on the tread portion. However, in order to exert an effect on such uneven wear, it is necessary to dispose it parallel to the eroded surface, that is, perpendicular to the stress.

Here, since the cupping uneven wear occurs due to the stress acting in the tire width direction, the eroded surface is formed in the tire circumferential direction. Therefore, parallel to this erosion surface,
That is, the sipe 22 extending in the tire circumferential direction perpendicular to the stress can exert a sufficient effect on cupping uneven wear in which the eroded surface advances in the tire width direction.

The stepware and riverware are as follows:
The erosion surface is generated due to the stress acting in the tire circumferential direction, and its eroded surface is formed in the tire width direction. Therefore, in order to exert an effect on the uneven wear, a sipe extending in the tire width direction is required. There is.

In the tire according to the present embodiment, the sipe row 24 is disposed substantially at the center of the shoulder rib 18 in the width direction, so that the sipe 22 is eroded by step wear or river wear at an early stage of wear. Therefore, when these uneven wears develop into cupping uneven wear, the sipe 22 can effectively work to suppress the cupping uneven wear.

By providing the sipe row 24 substantially at the center of the shoulder rib 18 in the width direction as described above, it is possible to prevent the uneven wear of the step wear and the river wear from progressing to the cupping uneven wear. .

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 rate of the step wear.
The same effect can be obtained as long as it is provided near the tread grounding end 11, not necessarily within the grounding surface, but outside the tread portion 10, 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.

[0044]

EXAMPLES In Example 1 and Comparative Examples 1 and 2, tire size: 285 / 75R24.5 14P
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 of each tire is as follows. In addition, the shoulder rib width Wr was set to 40 mm in all tread portions, and the configuration other than the sipe row was the same. Note that the distance from the narrow groove 20 to the tread ground end 11 was 3.0 mm.

Embodiment 1: Shoulder rib 18 shown in FIG.
And one sipe row 24 composed of sipe 22 extending in the tire circumferential direction. The distance Ws of the sipe row 24 from the widthwise inner end of the shoulder rib 18 is Ws = 30 mm, the length L of the sipe 22 is 5.0 mm, and the interval m of the sipe 22 is m = 5.
0 mm, sipe 22 width Wc = 0.5 mm, sipe 22
The depth of cut D was 8.0 mm.

Comparative Example 1: One in which no sipe was provided in the shoulder rib shown in FIG.

Comparative Example 2: Sipes extending in the width direction of the tire were placed in the shoulder ribs at intervals (5.0 m) in the circumferential direction of the tire.
m). Distance from inner edge of shoulder rib to sipe center = 32 mm, sipe length = 5.
0 mm, sipe width = 0.5 mm, and sipe cutting depth = 8.0 mm.

As a result of the test, in Example 1, the local wear developed from the step wear was stopped at the sipe row 24, and did not reach the cupping uneven wear. That is, step wear from the outer end 11 of the shoulder rib 18 to the maximum width of 13 mm has been generated.

On the other hand, in Comparative Example 1, cupping uneven wear occurred up to a maximum width of 25 mm from the outer end of the shoulder lip.

In Comparative Example 2, the sipe extending in the tire width direction was eroded, and the maximum width from the outer end of the shoulder rib was 2 mm.
Cupping uneven wear of up to 1 mm occurred.

[0052]

According to the pneumatic radial tire of the present invention, when step wear and river wear develop into local wear, and when the erosion front end approaches the sipe row, the local wear is caused by the sipe extending in the tire circumferential direction. Since further progress of wear in the width direction is hindered, uneven cupping wear can be suppressed.

[Brief description of the drawings]

FIG. 1 is an enlarged perspective view of a main part of a tread portion of a pneumatic radial tire according to one embodiment of the present invention.

FIG. 2A is a partial plan view of the tread portion, and FIG. 2B is a partial cross-sectional view of the tread portion.

FIG. 3 is an enlarged plan view of a sipe in the tread portion.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

5 (a) to 5 (c) are plan views showing a progress state of step wear of the tread portion.

FIGS. 6 (a) to 6 (c) are plan views showing the state of progress of the riverware of the tread portion.

FIG. 7 is a partial plan view of a tread portion showing another arrangement example of a sipe row provided on a shoulder rib.

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]

 10 tread part 12 main groove 18 shoulder rib 22 sipe 24 sipe row 26 recess

Claims (3)

[Claims] In 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, at least one rib has a sipe extending in the tire circumferential direction with an interval in the tire circumferential direction. A pneumatic radial tire, wherein at least one sipe row arranged in series is formed. 2. The pneumatic radial tire according to claim 1, wherein said sipe row is disposed within a region of 12 to 88% of a rib width of said rib. 3. The sipe array according to claim 1, wherein said sipe row is formed in a concave portion depressed with respect to a rib contact surface.
The described pneumatic radial tire.