JPH09240220A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress both of river wear and heal and toe abrasion and to prevent biting of a stone in the circumference groove by arranging a projection with an appropriate dimension in the groove bottom of the circumference groove and properly forming a tread face shape in a block land part. SOLUTION: A plurality of circumference grooves 2 and lateral grooves 3 are arranged in a tread 1, and by means of these grooves, multiple sectioned block land parts 4a, 4b, 4c are formed, while a low part, 8 is provided in the proper position in each of the block land parts 4a, 4b, 4c, and a projection 9 is arranged in the groove bottom of the circumference groove 2. A length between a tread opening end (a) position in the circumference groove 2 and a width end position (c) of the tread opening end (a) position side on a projection upper face 10 and a length between a tread opening end (b) position in the circumference groove 2 and a width position (d) of the tread opening end (b) position side on the projection upper face 10 are projected on a straight line along the tire diameter direction and on a straight line along the tire width direction, and distances D1 , D2 are provided by measurement of the projected lengths on the straight line along the tire diameter direction, while distances W1 , W2 are provided by measurement of the projected length on the straight line along the tire width direction. The distances D1 , D2 , W1 , W2 satisfy the following relationship: D1 >0.5×W1 , D2 >0.5×W2 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a tread with a plurality of circumferential grooves extending along the circumference of a tire, and a plurality of lateral grooves communicating with at least one of the circumferential grooves. It relates to pneumatic radial tires for heavy loads, which are formed by partitioning the tread into a large number of block land parts, and tires mainly used for trucks and dump trucks, etc. In addition to restraining, stone trapping in the circumferential groove is also prevented.

[0002]

2. Description of the Related Art A heavy-duty pneumatic radial tire having a block pattern formed by arranging a circumferential groove and a lateral groove on a tread, for example, a tire used for trucks and dump trucks, has a block land portion and a river wear. Uneven wear due to heel and toe wear is likely to occur.

[0003] As means for suppressing riverware,
A protrusion is provided on the groove bottom of the circumferential groove, and the upper surface of this protrusion is arranged slightly inward of the tread surface of the block land portion in the tire radial direction so that the force that promotes wear is concentrated on the protrusion and acts as a block. It is useful to suppress uneven wear on the land. However, heel and toe wear cannot be suppressed only by providing a protrusion on the groove bottom of the circumferential groove, and the circumferential groove has a problem that pebbles and the like are easily caught by providing the protrusion. .

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a river wear by providing a protrusion having an appropriate size on the groove bottom of a circumferential groove and optimizing a tread shape of a block land portion. An object of the present invention is to provide a heavy-duty pneumatic radial tire capable of suppressing uneven wear of the block land portion caused by both heel-and-toe wear and preventing stone trapping in the circumferential groove.

[0005]

In order to achieve the above object, a pneumatic radial tire for heavy load according to the present invention is provided with a plurality of circumferential grooves extending along the circumference of the tire in a tread, and the circumferential grooves. A plurality of lateral grooves that communicate with at least one of the above, and by these, a large number of block land portions are formed in the tread by partitioning, and the block land portions are directed from the inland portion toward the edge or corner. The circumferential groove has a lower portion where the height is gradually reduced, and the circumferential groove has a protrusion at the groove bottom that extends continuously or intermittently along the arrangement direction of the circumferential groove. Under the condition that the tire is filled with the specified air pressure, the grounding condition that is inside the tire radial direction from the position of the tread opening end (a, b) of the circumferential groove provided with the protrusion and further adds the specified mass to the tire It will be placed in sliding contact with the road surface below, and Between the open end (a) position of the projection and the width end position (c) of the upper surface of the protrusion on the side of the tread opening end (a) position, and the position of the tread opening end (b) of the circumferential groove, and the upper surface of the protrusion. Between the width end position (d) on the tread opening end (b) position side and the distance measured by projecting on a straight line along the tire radial direction are D ₁ and D ₂ , respectively, along the tire width direction. Distances measured by projecting on a straight line are W ₁ and W ₂ respectively
Then, the relationships between D ₁ and W ₁ and D ₂ and W ₂ are D ₁ > 0.5 × W ₁ and D ₂ > 0.5 × W ₂ , respectively.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a developed view showing a part of a tread portion of a typical heavy duty pneumatic radial tire according to the present invention, in which 1 is a tread, 2 is a circumferential groove, and 3 is a lateral groove. 4 is a block land portion, 5 is an inland portion of the block land portion,
6 is the edge of the block land, 7 is the corner of the block land, 8
Is a lower part, and 9 is a protrusion. A tire having a tread pattern shown in FIG. 1 includes a tread 1, a plurality of circumferential grooves 2 extending along the circumference of the tire, and a plurality of lateral grooves 3 communicating with at least one of the circumferential grooves 2. Is provided, and a large number of block land portions 4a, 4b, 4c are formed in the tread 1 by these.

The block land portions 4a, 4b and 4c are formed in the inland portion 5 thereof.
From the edge 6 or the corner 7 (Fig. 2 (c)) to the land height H
Has a lower portion 8 that gradually decreases (FIG. 2 (a)). Note that, in FIG. 1, in order to clearly show the lower portion 8, hatching is provided for convenience. The lower portion 8 is provided in a block land portion where heel and toe wear occurs. For example, in the case of the block land portion 4a located in the tread shoulder region, the outer portion in the tire width direction of the block land portion 4a is more likely to be worn than other portions, so that the lower portion 8 should be provided in this portion. Preferably (FIG. 2 (a)), and in the case of the block land portion 4b or 4c located in the area sandwiched between the circumferential grooves 2, the stepping side and the kicking side of the block land portion 4b or 4c are worn. Because it is easy to do
It is preferable to provide the lower portion 8 in these portions (see FIG. 2).
(b)) Further, the lower portion 8 may be provided only on the corner 7 of the block land portion where wear is likely to occur (FIG. 2 (c)), and the arrangement position of the lower portion 8 is a portion where heel and toe wear is likely to occur. Can be provided as needed.

The circumferential groove 2 has a projection 9 on the bottom of the groove.
FIG. 3 shows the cross-sectional shapes of the block land portion and the projection when cut along the line D-D in FIG. This protrusion 9 has its upper surface 10
However, under the condition that the tire is filled with a specified air pressure, the tire is in the tire radial direction inside of the tread opening end positions a and b of the circumferential groove 2 provided with the protrusion, and the grounding condition in which the specified mass is further added to the tire. It is arranged below so as to be in sliding contact with the road surface, whereby the force promoting wear is concentrated on the projections 9 and the river wear of the block land portion can be suppressed. Although FIG. 1 shows the case where the projections 9 are continuously provided along the arrangement direction of the circumferential groove 2, they may be provided intermittently as shown in FIG. 4, and there is no particular limitation. .

When the projection 9 is provided in the circumferential groove 2, between the tread opening end position a of the circumferential groove 2 and the width end position c of the projection upper surface 10 on the tread opening end position a side, and The distance D measured by projecting on a straight line along the tire radial direction between the tread opening end position b of the circumferential groove 2 and the width end position d of the protrusion upper surface 10 on the tread opening end position b side. ₁ , D ₂
Distances W ₁ and W measured by projecting on a straight line along the tire width direction
The relationship with ₂ is D ₁ ≦ 0.5 × W ₁ , D ₂ ≦ 0.5 × W
_In the case of 2, pebbles and the like are likely to be sandwiched between the groove wall of the circumferential groove 2 and the projection 9, and stone trapping is likely to occur in the circumferential groove.
Therefore, in the present invention, the circumferential groove is formed by configuring the relationship between D ₁ and W ₁ and D ₂ and W ₂ such that D ₁ > 0.5 × W ₁ and D ₂ > 0.5 × W ₂ , respectively. It is possible to prevent the stone trapping that tends to occur in 2.

[0010]

EXAMPLES Specific examples of the heavy duty pneumatic radial tire according to the present invention will now be described with reference to the drawings. -Examples The heavy-duty pneumatic radial tires of Examples have the tread pattern shown in Fig. 1, and the tire size is 1000R20,1.
1R22.5, the tread 1 has four circumferential grooves 2 extending along the circumference of the tire and a plurality of lateral grooves communicating between the circumferential grooves 2 and between the circumferential groove 2 and the tread end 11. 3 was provided, and by these, a large number of block land portions were formed in the tread 1. The block land area consists of three types of block land areas 4a, 4b,
Each block land portion 4a, 4b, 4c is provided with a lower portion 8 in which the block height gradually decreases from the inland portion 5 toward the edge 6 on each tread surface 5. The lower portion 8 is provided on the tire width direction outer side portion of the block land portion 4a, and on the stepping side and the kicking side portion of the block land portions 4b and 4c. A continuous protrusion 9 is provided on the groove bottom of the circumferential groove 2 along the arrangement direction of the circumferential groove 2. Further, as shown in FIG. 3, the protrusion 9 has a distance D ₁ or D ₂ measured by projecting between a and c and between b and d on a straight line along the tire radial direction, which is 2.
The distance was set to 0 mm and the distances W ₁ and W ₂ projected on a straight line along the tire width direction were both set to 1.5 mm.
The other tire structures used were the same as those of a normal heavy-duty pneumatic radial tire.

Comparative Example 1 The heavy-duty pneumatic radial tire of Comparative Example 1 has substantially the same tire structure as that of the Example except that the groove bottom of the circumferential groove 2 does not have the protrusion 9.

Comparative Example 2 The heavy-duty pneumatic radial tire of Comparative Example 2 has ac
And b-d are projected on a straight line along the tire radial direction and the distances D ₁ and D ₂ are both 2.5 mm, and the distance W ₁ is projected on a straight line along the tire width direction. And W ₂ are arranged to be 5.0 mm and 4.0 mm, respectively, and have substantially the same tire structure as the embodiment.

Conventional Example 1 The heavy-duty pneumatic radial tire of Conventional Example 1 has no lower portion 8 on the block land portion 4 and has no projection 9 on the bottom of the circumferential groove 2. The tire structure is almost the same as that of the embodiment.

Conventional Example 2 The heavy-duty pneumatic radial tire of Conventional Example 2 does not have the lower portion 8 on the block land portion 4, and is located between a and c and between b and
The distances d ₁ and D ₂ projected on a straight line along the tire radial direction are both 2.5 mm, and the distances W ₁ and W ₂ projected on a straight line along the tire width direction are measured. 5 mm each,
The tire structure is almost the same as that of the embodiment except that the tire structure is arranged to be 4 mm.

(Test Method) Each of the above-mentioned test tires was tested to evaluate the tire performance. The test was performed for wear resistance and presence or absence of stone trapping in the circumferential groove. Abrasion resistance was examined for both riverwear and heel and toe wear and evaluated for each. These abrasion resistances were evaluated by the width of the river wear and the amount of step difference between heel and toe. Table 1 shows the evaluation results. The wear resistance A in the table is evaluated from the amount of wear caused by river wear, and the wear resistance B is evaluated from the amount of wear caused by heel and toe wear,
In both evaluations, the case where uneven wear hardly occurs and the wear is uniform is described as “◯”, and the case where uneven wear occurs is described as “x”.

[0016]

[Table 1]

From the results shown in Table 1, in the example, neither uneven wear due to river wear nor heel-and-toe wear occurred, and no stone trapped in the circumferential groove. On the other hand, in Conventional Examples 1 and 2 and Comparative Example 1, either one of river wear and heel and toe wear occurred, and in Comparative Example 2, neither river wear nor heel and toe wear occurred. However, stone trapping occurred in the circumferential groove.

[0018]

According to the present invention, both river wear and heel and toe wear can be suppressed, and stone trapping in the circumferential groove can be prevented.

[Brief description of drawings]

FIG. 1 is a plan view showing a part of a tread portion of a typical pneumatic radial tire for heavy load according to the present invention when it is developed.

FIG. 2 (a) is a perspective view of one of the block land portions 4a shown in FIG. 1 taken out, and FIG. 2 (b) is one of the block land portions 4b or 4c shown in FIG. It is a perspective view when it is viewed from above, and (c) is a view showing a modified example of the block land portion.

3 is a cross-sectional view taken along the line DD of FIG.

FIG. 4 is a plan view showing a part of a tread portion of another embodiment in a developed state.

[Explanation of symbols]

 1 tread 2 circumferential groove 3 lateral groove 4a, 4b, 4c block land part 5 block land part inland part 6 block land part edge 7 block land part corner 8 low part 9 protrusion 10 protrusion top surface 11 tread edge 12 Tire equator

Claims (1)

[Claims] 1. A tread is provided with a plurality of circumferential grooves extending along the circumference of a tire, and a plurality of lateral grooves communicating with at least one of the circumferential grooves, whereby a large number of treads are provided on the tread. In a heavy-duty pneumatic radial tire that is formed by partitioning the block land portion of, the block land portion has a lower portion where the land portion height gradually decreases from the inland portion toward the edge or corner, and The groove has a projection on the bottom of the groove that extends continuously or intermittently along the arrangement direction of the circumferential groove, and the upper surface of this projection is
Under the condition that the tire is filled with the specified air pressure, it is on the inner side in the tire radial direction from the position of the tread opening end (a, b) of the circumferential groove provided with the protrusion, and the grounding condition that further adds the specified mass to the tire It makes a sliding contact with the road surface at a position between the tread opening end (a) position of the circumferential groove and the width end position (c) of the upper surface of the protrusion on the side of the tread opening end (a) position and the circle. The distance between the tread opening end (b) position of the circumferential groove and the width end position (d) of the upper surface of the protrusion on the tread opening end (b) position side was projected on a straight line along the tire radial direction and measured. Assuming that the distances are D ₁ and D ₂ , respectively, and the distances measured by projecting on straight lines along the tire width direction are W ₁ and W ₂ , respectively, the relationship between D ₁ and W ₁ and D ₂ and W ₂ is D, respectively. ₁
> 0.5 × W ₁ , D ₂ > 0.5 × W _{2 A} pneumatic radial tire for heavy loads, characterized in that: