JPH0456605A - Pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To improve drainage and one-sided wear resistance characteristics without damaging a tire life by a method wherein narrow grooves extending in a state to be separated from each other in a specified ratio with a main groove therebetween are formed on the main groove side of a rib to form a narrow rib, and the amplitude of the narrow groove is set to a value higher than that of the main groove. CONSTITUTION:A tire 20 has a main groove 22 formed in a tread being a tread part and extending approximately in a zigzagging shape in the peripheral direction of a tire, and a plurality of wide ribs 24 partitioned in a manner to be separated away from each other in the direction of the width of the tire. In this case, narrow grooves 26 extending in a zigzagging shape in the peripheral direction of the tire and separated away from each other are formed in the side wall of the portion on the main groove side of the wide rib 24, and a narrow rib 28 extending in a zigzagging shape in the peripheral direction of the tire is formed in co-ordination with the main groove 22. Zigzagging pitches PM and PN in the peripheral direction of the tire of the narrow and main grooves 26 and 22 are made approximately equal to each other, and meanwhile amplitude SN of the narrow groove 26 is set to a value higher than amplitude SM of the main groove 22. Further, a distance between the main and narrow grooves 22 and 26 is 1% or more of a tread width at a part where the grooves are spaced most closely to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heavy-duty pneumatic tire that has improved drainage and uneven wear resistance without impairing tire life.

(Prior art) A carcass ply consisting of cords arranged substantially uniformly in the radial direction of the tire, with both ends of at least one ply wrapped around a beat wire from the inside to the outside of the tire, is attached to the tire equator. A radial construction tire with a belt consisting of plies of cords arranged at a shallow angle to the plane has a so-called "hoop" effect on the belt, which allows the tire to move within an angular range of 35° to 40° with respect to the tire's equatorial plane. Compared to bias structure tires that have carcass plies and breakers made of diagonal cord layers, there is less movement of the tread rubber that forms the tread surface of the tire, and it has excellent wear resistance and handling stability, and low rolling resistance. Due to its many advantages, with the development and maintenance of expressway networks in recent years, there is a tendency for it to be widely used in heavy-duty vehicles such as trucks and buses.

In addition, in such a tire, as shown schematically showing half of the tread portion in FIG. A tread pattern generally called a rib type, which has main grooves 11 extending in a zigzag pattern, is preferably used. Note that the symbol S indicates the equatorial plane of the tire.

However, in a tire having such a tread pattern, from the beginning to the middle of its use, the wide ribs 12 that are defined by the main groove 11 and extend in a zigzag shape in the tire circumferential direction, especially the wide ribs 12 that protrude in the tire width direction. Projection part 14
Uneven wear, which starts at the top of the tire and expands in the circumferential and width directions of the tire, occurs locally in the region indicated by symbol A. This uneven wear gradually increases as the tire mileage increases, and eventually develops into uneven wear along the edges of the zigzag ribs, so-called railway wear, which only makes the tire's appearance unsightly. First, it had the disadvantage of reducing traction and braking performance, and significantly shortening the life of the tire.

For this reason, as shown in FIG. 3(b), railway wear along the edges of each wide rib 12 defined by the main groove 11 extending in a substantially zigzag shape in the circumferential direction of the tire is prevented. Zigzag-shaped narrow ribs extending in the circumferential direction of the tire and cooperating with the main groove 11 are spaced substantially parallel to each other along the side walls of the wide ribs 12 in order to suppress the vibration. A tire with 16 narrow grooves I8 was proposed.

In this tire, narrow ribs 16 defined by zigzag-shaped main grooves and narrow grooves extending in the tire circumferential direction function as wear sacrifice parts, and wide ribs 16 facing the narrow ribs 16
Since uneven wear along the edges 2 is suppressed and the tire tread is worn almost uniformly, the life of the tire is improved.

(Problem to be Solved by the Invention) However, in this tire, since the rigidity of the narrow ribs 16 is smaller than that of the wide ribs 12, the narrow ribs 16 substantially affect the tire life. However, due to the provision of the narrow ribs 16, the volume occupied by the wide ribs 12 excluding the narrow ribs is smaller than the tire having the tread pattern shown in FIG. The disadvantage is that the tire life is shorter than that of the tire.

For this reason, the groove width of the main groove 11 is narrowed without reducing the volume of the rib portion excluding the narrow rib 16 from the wide rib 12, and the volume of the rib portion in the entire tire is made equal to that of the tire shown in Figure (a). At the same level, it is possible to suppress the decrease in tire life, but in that case, the groove width of the main groove 11 would be narrowed, which would impair the drainage performance of the tire and reduce wet performance, which is another problem. occurs.

The present invention was made in view of such problems,
The purpose is to provide a heavy-duty pneumatic tire with improved drainage and uneven wear resistance properties without impairing tire life.

(Means for Achieving the Object) In order to achieve this object, in the present invention, the tread forming the tire tread portion is partitioned by main grooves extending in the circumferential direction and mutually extending in the width direction of the tire. In a heavy-duty pneumatic tire comprising a plurality of ribs spaced apart from each other, the main groove side of at least one rib extends approximately in a zigzag shape in the circumferential direction of the tire, and the portion closest to the main groove is 1% of the tread width.
Narrow ribs are formed by disposing narrow grooves spaced apart from each other and extending substantially in a zigzag pattern in the circumferential direction of the tire, and the amplitude of the narrow grooves is made larger than the amplitude of the main groove.

Further, in order to further improve drainage performance, it is preferable that the main groove extends in the tire circumferential direction substantially parallel to the tire equatorial plane, and that its amplitude is substantially zero. In order to sufficiently suppress uneven wear at the edges of the wide ribs, the surfaces of the narrow ribs should be located on the inner side of the tread portion in the tire radial direction.

(Function) According to this tire, since the amplitude of the main groove is smaller than that of the narrow groove, smooth drainage by the main groove is ensured, while
Because the narrow grooves have a larger amplitude than the main groove, the shape of the adjacent wide rib portion can be maintained in a zigzag shape similar to that of conventional tires, so that traction and braking performance are not impaired. In addition, since the occurrence of uneven wear along the narrow ribs defined by the main groove and the narrow grooves cooperating therewith or along the wide ribs is suppressed, the life of the tire will not be shortened.

(Embodiments) Hereinafter, preferred embodiments to which the present invention is applied will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a tire to which the present invention is applied, and shows a tread half forming a tread portion thereof. Further, since the structure of the tire shown in this example is equivalent to that of a known tire having a radial structure, a description thereof will be omitted here.

The tire 20 has a main groove 22 formed in the tread forming the tread surface thereof, which extends in a substantially zigzag shape in the circumferential direction of the tire, and the main groove 22 has a plurality of wide ribs 24 spaced apart from each other in the width direction of the tire. compartmentalize.

The main groove side portions of these wide ribs 24 have narrow grooves 26 spaced apart from each other on the side walls thereof and extending in a zigzag shape in the tire circumferential direction.
are respectively disposed, and cooperate with the main groove 22 to form narrow ribs 28 extending in a crooked manner in the tire circumferential direction.

Further, the narrow grooves 26 and the main grooves 22 have substantially equal zig-sag pitches PM and PN in the circumferential direction of the tire, whereas the amplitude SN of the narrow grooves 26 is set larger than the amplitude SM of the main grooves 22.

This selection is made so that the amplitude SM of the main groove 22 extending in a zigzag shape in the tire circumferential direction is smaller than that of the narrow groove 26, that is, the amplitude SM of the main groove 22 extending in a zigzag shape is smaller than that of the main groove extending in a zigzag shape. This is to reduce the drainage resistance due to the zigzag-shaped main groove 22 by making the difference between 32 and 32 smaller than the difference between them in the narrow groove 26, and the main groove 22 has a groove width of 2% or more of the tire tread width. This is because, in the case where the amplitude SM of the main groove is smaller than that of the narrow groove 26, better drainage performance is exhibited.

The reason why the amplitude SN of the narrow groove 26 is set larger than that of the main groove 22 is due to the fact that the amplitude of the main groove 22 is set to a smaller SM. This is to compensate for the decrease in performance. Note that the narrow grooves 26 herein refer to grooves whose width is within the range of 1.0% to 0.1% of the tread width.

Preferably, the surface of the narrow rib 28 defined by the narrow groove 26 and the main groove 22 is positioned radially inward from the tire tread, and the distance between the main groove and the narrow groove is set to the closest distance between them. 1% or more of the tread width in the part where the
It shall be located within 10% of the tread width at the farthest point.

This occurs when the distance between the narrow grooves 26 and the main groove 22 is smaller than 1% of the tread width at the part where the narrow grooves 26 and the main groove 22 are closest, or when the distance between the grooves at the part where they are farthest from each other is smaller than 1% of the tread width. This is because if the distance is greater than 10% of the tread width, uneven wear at the edges of the wide ribs 24 along the narrow grooves 26 cannot be effectively prevented. By locating the surface of the narrow rib 28 inward in the tire radial direction from the surface of the wide rib 24, that is, the tire tread surface, uneven wear at the edge of the wide rib along the narrow groove 26 can be more securely prevented. can be prevented.

Moreover, by adopting such a configuration, the drainage performance of the main groove 22 can be improved, and the volume of the wide rib portion excluding the narrow rib 28 can be made approximately the same as that of a conventional tire. Abrasion resistance properties are not impaired.

By the way, in the embodiment shown in FIG. 1, the main groove extends in a zigzag shape in the tire circumferential direction, but as shown in FIG. In other words, the main groove 22 may extend in the circumferential direction substantially parallel to the tire equatorial plane S. In that case, the main groove 22 may extend substantially linearly in the circumferential direction. , the drainage performance can be further improved. The structure of the tire shown in this embodiment is the same as that of the tire shown in FIG. 1, except that the main groove 22 extends substantially linearly in the circumferential direction, so a description thereof will be omitted.

In order to investigate the life span, uneven wear resistance, and wet performance of the tire according to the present invention, a comparative test was conducted using the conventional tire shown in FIG. 3, and the following results were obtained. The size of each tire used in the comparative test was TBR10,0.
It is OR20.

◎Test tires: - Invention tire 1: A tire with the tread pattern shown in Figure 1, with a tread width of 200 mm, a main groove width of 10 mm, and a groove depth of 14.
value, amplitude SM5.0mm, zigzag pitch PM35mm
, groove width of the narrow groove, O+++m, groove depth 14+nm, amplitude SN7.6a+m, zigzag pitch P N35mm, and the distance of closest approach between the main groove and the narrow groove and the distance between shells are each 1.2 of the tread width. % and 2.5%.

- Invention Tire 2: A tire having the tread pattern shown in FIG. 2, with a tread width of 200 mm and a main groove width of 8. Omm, groove depth 14
mm, groove width of narrow groove 1. Omm, groove depth 14mm, amplitude S
N8. (lI+1[11, zig-sag pitch P pi 3
5 mm, and the closest distance between the main groove and the narrow groove and the distance between shells were respectively 1.2% and 5.2% of the tread width.

- Comparison Tire 1: A tire with a tread pattern shown in Figure 3(a), tread width 2'00 mm, main groove groove width 19.4 mm,
Groove depth 14mm, amplitude S, 7.6mm, zig-sag pitch P
x35mm.

- Comparison Tire 2: A tire with the tread pattern shown in Figure 3(b), tread width 200 mm, main groove width 19.4 mm, groove depth 14 nun, amplitude SM 7.6 mm, narrow groove groove width. 1.
0 cabinet, groove depth 14mm, amplitude SM7.6M, main groove and UR
The zigzag pitch P of the grooves is 35 mm, and the distance between the main groove and the narrow groove is 4.0 mm.

◎Test method: ・Tire life and uneven wear resistance performance: Each test tire was assembled on a regular rim, the regular internal pressure was applied, and the test tires were alternately mounted on the front wheels of a 2D-4 car, and after driving for 60,000 hours, The life of the tire and the width of uneven wear that occurred along the edge of the wide rib that opposes the narrow rib were measured, and each was evaluated using an index.

・Wet performance: Driving at a speed of 4 per hour on a test track with a 3.0 mm thick water film.
The distance traveled by the test vehicle until it stopped was measured and evaluated as an index.

◎Test results The test results are shown in the table below. Note that each performance is better as the index is larger.

It can be seen that uneven wear resistance and drainage performance can be improved without impairing ear life.

(Effects of the Invention) Thus, according to the present invention, it is possible to provide a heavy-duty pneumatic tire that has superior drainage and uneven wear resistance performance compared to conventional tires.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a half of the tread portion of a preferred embodiment of a heavy-duty pneumatic tire according to the present invention, with respect to the equatorial plane; FIG. FIGS. 3(a) and 3(fb) are cross-sectional views showing the half of the tread of the example tread relative to the equatorial plane, and FIGS. It is a diagram. 20.40 - Tire 22 - Main groove 24 wide rib 26 - Narrow groove 28 - Narrow rib 30 - Protruding corner 32 - recessed part Fig. 1 zO

Claims (1)

[Scope of Claims] 1. A heavy-duty pneumatic tire comprising a tread forming a tire tread portion, a plurality of wide ribs separated from each other in the width direction of the tire and separated by a main groove extending in the circumferential direction of the tread. , narrow grooves are provided on the main groove side of at least one wide rib, extending in a substantially zigzag shape in the circumferential direction of the tire, with the part closest to the main groove spaced apart by 1% or more of the tread width. A heavy-duty pneumatic tire characterized by forming ribs and making the amplitude of the narrow grooves larger than the amplitude of the main grooves. 2. The pneumatic tire for heavy loads according to claim 1, wherein the amplitude of the main groove is substantially zero. 3. The pneumatic tire for heavy loads according to claim 1 or 2, characterized in that the surface of the narrow rib is located inside the tread portion in the radial direction of the tire.