JPH05213014A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic tire for heavy load having excellent wetness resistance while driving and braking performances are kept. CONSTITUTION:The ground blocks 3 of treads which are separated in the peripheral direction of a tire and mutually independent have tread patterns divided by a lateral groove 5 to separate the ground block 3, and a small ground block 10 having a ground face whose area is narrower than the area of the ground face of the ground block 3 is provided so that the ground face of the small ground block 10 in the lateral groove 5 may have difference 11 in level being radially inside from the ground face of the ground block 3. In addition, a thin groove 12 which is about the same in the depth of the groove as the lateral groove 5 and the same in the longitudinal direction of the groove as the lateral groove 5 is formed between the stepping-in and projecting ends of the ground block 3 and the small ground block 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic radial tire for heavy loads such as trucks and buses.

[0002]

2. Description of the Related Art Generally, in pneumatic tires, rib type, lug type, rib-lug type, block type and rib-block type tread patterns are selected according to the application. From the viewpoint of control performance and wet performance, a block or rib-block type tread pattern is adopted.

However, the block or rib-block type tread pattern has a strong tendency to cause so-called heel-and-toe wear (uneven wear) due to block motion due to rolling of the tire in a tire contact area under high load. Met. Therefore, a heavy duty pneumatic tire disclosed in Japanese Patent Laid-Open No. 54-70503 has been proposed (conventional example 1).

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Is a padless (small grounding block) with a narrow groove arranged in the lateral groove that separates the grounding block. In this case, since the groove depth of the narrow groove is shallow and there is only one narrow groove, However, there was a problem that the wet performance was poor.

According to the present invention, in the small grounding block arranged in the lateral groove, the stepping end and the jumping-out end of the small grounding block and the grounding block have a depth substantially equal to the groove depth of the lateral groove and the same groove longitudinal direction. It is an object of the present invention to provide a pneumatic tire in which wet resistance is ensured while maintaining driving performance and braking performance regardless of before and after wear by providing two narrow grooves in the direction.

[0006]

The present invention relates to a grounding block 3 of a tread which is separated from each other in the tire circumferential direction and is independent of each other.
A small ground block 10 having a tread pattern divided by a lateral groove 5 separating the ground block 3 and having a ground plane smaller than the ground plane of the ground block 3.
In a pneumatic tire in which the ground contact surface of the small ground contact block 10 has a step 11 radially inside the ground contact surface of the ground contact block 3 in the lateral groove 5, in order to achieve the above object, the following technical I am taking steps.

That is, according to the present invention, the thin groove 12 having a groove depth substantially equal to that of the lateral groove 5 and having a groove longitudinal direction in the same direction is formed as a small groove at the stepping end and the jumping end of the ground block 3. It is characterized in that it is formed between the ground blocks 10.

[0008]

[Operation] When the pneumatic tire 1 according to the present invention is mounted on an automobile and the vehicle runs, the lateral groove 5 from the contact surface of the contact block 3
Since the grounding surface of the small grounding block 10 arranged inside has a low step, the driving performance and the braking performance at the stepping end and the jumping out end of the grounding block 3 are secured.

The grounding surfaces of the grounding block 3 and the small grounding block 10 both come into contact with the road surface, but since the grounding surface of the small grounding block 10 has no groove, its rigidity is ensured, while the grounding block 3 Since the area is smaller than the ground contact surface, it wears earlier than the ground contact block 3 to maintain the step. Further, even in the latter half of wear, the groove depth of the narrow groove 12 is the lateral groove.
Since it is the same as that of 5, the above-mentioned step is maintained, the driving performance and braking performance are not impaired, and
Since 12 is two and the groove depth is substantially the same as that of the lateral groove 5 and the groove direction is also the same, the drainage property is good.

[0010]

Embodiments of the present invention will now be described with reference to the drawings in comparison with two conventional examples. FIG. 1 shows an embodiment of the present invention, FIG. 2 shows a conventional example A, and FIG. 3 shows a conventional example B.
Since the tread patterns are almost the same in the three cases, the conventional examples A and B common to the embodiment of the present invention are denoted by A and B, respectively.

In the figure, pneumatic tires 1, 1A, 1B are radial tires for heavy load, and here, for heavy load,
Mainly used for vehicles such as trucks and buses. The pneumatic tire has its tread 2,2A, 2B
, The grounding blocks 3, 3A, 3B are separately arranged in the tire circumferential direction (tire rotation direction) 4, 4A, 4B, and the lateral grooves are arranged.
It is divided by 5,5A, 5B and has vertical grooves 6,6
It has a block pattern divided in the tire axial direction by A and 6B.

The grounding block includes a pair of left and right center blocks 7L, 7R, 7LA, 7RA, 7LB, 7RB and a pair of left and right side blocks 8L, 8R, 8LA, 8RA, 8LB, 8RB and a pair of left and right shoulder blocks 9L, 9R, It consists of 9LA, 9RA, 9LB, 9RB. The center block has a substantially trapezoidal ground contact surface having two triangular sides in a plan view, and is arranged through a lateral groove in the tire circumferential direction.The corresponding center blocks are shifted in phase by 1/2 pitch in the circumferential direction. The vertical groove has a zigzag shape.

The side block has a substantially trapezoidal ground contact surface having two triangular sides in a plan view, and is arranged through lateral grooves in the tire circumferential direction with the two triangular sides facing outward (outward in the tire axial direction). It is offset by 1/2 pitch phase in the circumferential direction with respect to the center block, and in cooperation with the center block, it is sectioned in the circumferential direction by straight vertical grooves. The shoulder block has a substantially trapezoidal ground contact surface having two triangular sides in a plan view, is arranged through lateral grooves in the tire circumferential direction with the two triangular sides facing inward, and in the circumferential direction with the corresponding side block.
The phases are shifted by 1/2 pitch, and they are further divided into zigzag vertical grooves in cooperation with the two triangular sides of the side block.

Small grounding blocks are provided in the lateral grooves 5,5A, 5B of the respective grounding blocks 3,3A, 3B divided by the lateral grooves 5,5A, 5B of the center block, the side blocks and the shoulder block.
10,10A, 10B are arranged. In the embodiment of the present invention, as shown in FIGS. 1B and 1C, a small grounding block 10 having a grounding surface having an area smaller than the area of the grounding surface of the grounding block 3 is provided in the lateral groove 5. The ground contact surface is located inside the ground surface of the ground block with a step 11, and as shown in FIG. 1C, the groove depth is approximately the same as the groove depth of the lateral groove 5 and the groove longitudinal direction is the same direction. Two grooves 12 are formed between the stepped end and the jumping end of the ground block 3.

However, the small grounding block 10 in the shoulder blocks 9L and 9R has a lateral groove depth as shown in FIG. 1 (B).
(See Fig. 1 (E)) The depth is about 1/3. In the embodiment, as shown in FIG. 1B, the height of the small grounding block 10 is 4 mm, the depth of the narrow groove 12 is 5 mm, and the step 11 is 1 mm. In the center-side ground block as shown in FIG. 1C, the height of the small ground block 10 shown in FIG.
Has a depth of 15 mm, and the step 11 has a depth of 1 mm.
As shown in (D), the depth of the vertical groove is 17 mm, and as shown in FIG. 1 (E), the depth of the horizontal groove is 17 mm.

On the other hand, in the conventional example A shown in FIG. 2, the lateral groove 5A in the ground block 3A on the center side is formed.
2C has a depth of 15 mm as shown in Fig. 2 (C). There is no small grounding block in this lateral groove 5A, and a small grounding block 10A with a step 11A of 5 mm in the lateral groove 5A of the shoulder grounding block 3A is fine. It is provided without going through the groove.

On the other hand, in the conventional example B shown in FIG. 3, a small grounding block 10B having a narrow groove 12B having a depth of 4 mm in the center is provided in the lateral groove 5B of the grounding block 3B at the shoulder, and also in the center side. Lateral groove of each ground block 3B
5B is provided with a small grounding block 10B having a step 11B of 1 mm, and a fine groove having the same depth as the lateral groove at the center of the block 10B.
12B is formed.

Next, the heel and toe wear amounts of the pneumatic tires of the examples of the present invention and the pneumatic tires of Conventional Examples A and B were compared by experiments. Experimental condition 10 ton vehicle with 2 front wheels and 4 ton wheels with 10.00 R20 size tires of the present invention and conventional examples A and B were mounted, and heel-and-toe after traveling 10,000 km mainly on highways. The amount of wear was measured by the amount of step.

Since only the braking force acts on the front tires, heel and toe wear often occurs, and the data in Table 1 below are the data for the front tires. Moreover, the measurement position of the step amount is 1, 1A, 1B to 6, 6A, 6B shown in FIGS. 1, 2 and 3.
The larger the amount of step, the worse.

[0020]

[Table 1]

In Table 1, the wet performance test conditions are as follows. Judgment by braking distance on wet and wet asphalt road Wet and wet braking test by JIS D 1013 test method Load JIS uniform loading 100% Braking initial speed 60km / HR Tire internal pressure 7.25kg / cm ^{2 In} Table 1, ABCDEF is In the present invention, the parts shown in FIG. 1, the conventional example A in FIG. 2 and the conventional example B in FIG. 3 are indicated.

[0022]

The present invention is as described above, and according to the present invention, the small grounding block arranged in the lateral groove can have its grounding area substantially filled with the width of the lateral groove to eliminate the narrowing of the area. In order to prevent the rigidity of the small grounding block from decreasing, and further to the step-in end and the jumping-out end of the small grounding block and the grounding block, there are two lateral grooves each having a depth substantially equal to the groove depth and a groove longitudinal direction in the same direction. It is possible to provide a pneumatic tire that guarantees wet resistance while maintaining driving performance and braking performance regardless of the former and latter half of wear by providing the narrow groove.

[Brief description of drawings]

1 shows an embodiment of the present invention, FIG. 1 (A) is a perspective view,
1B is a bb sectional view of FIG. 1A, FIG. 1C is a cc sectional view of FIG. 1A, and FIG. 1D is d- of FIG. 1A. FIG. 1E is a sectional view taken along the line ee of FIG. 1A.

2 shows a conventional example A, FIG. 2 (A) is a perspective view, FIG.
2B is a sectional view taken along line bb of FIG. 2A, and FIG.
It is a cc sectional view of (A).

3 shows a conventional example B, FIG. 3 (A) is a perspective view, FIG.
3B is a sectional view taken along line bb of FIG. 3A, and FIG.
It is a cc sectional view of (A).

[Explanation of symbols]

 1 Pneumatic tire 2 Tread portion 3 Grounding block 5 Horizontal groove 10 Small grounding block 11 Step 12 Fine groove

Claims (1)

[Claims] 1. A grounding block (3) of a tread that is separated from each other in the tire circumferential direction and has a tread pattern divided by a lateral groove (5) separating the grounding block (3), and the grounding block. A small grounding block (10) having a grounding surface having an area smaller than the area of the grounding surface of (3) is provided in the lateral groove.
In a pneumatic tire in which the ground contact surface of the small ground contact block (10) has a step (11) radially inside the ground contact surface of the ground contact block (3) in (5), the groove depth of the lateral groove (5) and A thin groove (12) with the same groove depth and the same groove longitudinal direction is used as the ground block (3).
A pneumatic tire characterized in that it is formed between the step-in end and the jump-out end of and the small ground contact block (10).