JP3096351B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention improves the durability of a tire by preventing uneven wear which tends to occur on a block disposed in a shoulder region, and can be suitably used as a tire for an all-wheel drive vehicle. Regarding tires.

[0002]

2. Description of the Related Art In a pneumatic tire, so-called heel-and-toe wear may occur in which an edge of a rib or a block arranged in a tread shoulder region is abnormally worn.

[0003]

In order to prevent such uneven wear, conventionally, methods such as changing the radius of curvature of the tread and changing the shape of the block have been used. Changing the mold will increase the cost, and in addition, the image of the tread pattern will be significantly changed, which will affect the running performance.

[0004] The inventor conducted a detailed investigation on the worn condition of old tires in order to investigate the cause of such uneven wear. As a result, in the case of a tire in which heel and toe wear has occurred, the tire has a shoulder block a. A slip (indicated by an arrow f in FIG. 7) occurs in a direction inclined to the equator side c with respect to the tire advancing direction, and the slip causes heel and toe wear w on the rear side of the block a in the tire advancing direction.
(Shown by oblique lines in FIG. 7).

[0005] Therefore, in order to prevent the occurrence of such uneven wear, it is necessary to suppress the slip. For this purpose, a siping extending in a direction intersecting the direction of the slip is provided.
It has been found that by allowing the block a to follow this slip, the occurrence of uneven wear can be prevented.

The present invention improves the durability by preventing the occurrence of uneven wear such as heel-and-toe wear without lowering the running performance, thereby improving the durability, and can be suitably used as a tire for all-wheel drive vehicles. It aims to provide tires.

[0007]

SUMMARY OF THE INVENTION The present invention is a pneumatic tire having a block pattern and a rib block pattern having a shoulder block disposed on both sides of the tire along a tread edge by a circumferential groove and a lateral groove. The block circumferential length A, which is the distance in the tire circumferential direction between the earliest landing point of the shoulder block that contacts the earliest with the rotation of the tire and the last landing point that touches the last, is at least 0.25 times and A distance of 0.5 times or less, in a region B from the trailing edge facing the lateral groove and separated from the trailing edge facing the lateral groove to the leading side, the leading side is directed outward in the tire axial direction, and the tire is A pneumatic tire characterized by forming a plurality of sipes inclined at an angle of 30 ° or more and 60 ° or less with respect to an axial direction.

The siping preferably has a depth h in a direction normal to the tread surface of not less than 0.25 times and not more than 0.65 times the height H of the shoulder block.

[0009] The tread pattern may be a pattern having a direction in which lateral grooves arranged on both sides of the tire equator are inclined in symmetric directions.

[0010]

[Effect] Heel and toe wear is caused by slipping of the tread surface between the tire and the ground when the tire is running. Also, as shown in FIG. 7, the slip occurs in a direction in which the first arrival side is directed toward the tire equator side, that is, inward in the tire axial direction with reference to the trailing edge of the block. Therefore, by arranging sipes extending in the direction intersecting with the direction of the slip, the block can easily move following the acting force causing the slip, thereby reducing the occurrence of uneven wear. It can be prevented.

As shown in FIG. 4, tires were trial-produced with various angles of inclination of the siping with respect to the tire axis, and the amount of heel and toe wear was adjusted.
The result that the wear was the least in the range of 0 ° was obtained. Based on this result, the range of the inclination angle θ is set to 30
It was set to と 60 °.

The siping is provided at a distance of at least 0.25 times and at most 0.5 times the circumferential length A of the block in the area B between the rear edge facing the lateral groove and the front edge. ing. In the shoulder block, the heel and toe wear occurs on the rear arrival side of the block. By providing the region B siping located on the rear arrival side, uneven wear that tends to occur in the tread shoulder region is reduced. It can be effectively prevented. In addition, since no siping is performed on the first side where the force acts on the shoulder block at the time of touching the ground, that is, outside the area B, it is possible to prevent the block from being broken due to the impact force.

In setting the area B, as shown in FIG. 5, a tire was trial-produced with a different ratio B / A between the area B and the circumferential length A, and the relationship between the heel-and-toe wear amount and the rate of occurrence of rubber chipping. Investigation was conducted to find that the value of the ratio B / A was 0.25.
Below, while heel and toe wear increases sharply,
When the value of the ratio B / A exceeded 0.5, it was confirmed that rubber chipping occurred in the region B of the shoulder block, and the occurrence rate was significantly increased. Therefore, in order to suppress both uneven wear and rubber chipping, the area B is set to a range of 0.25 to 0.5 times the length A in the block circumferential direction.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. 1 to 3, a pneumatic radial tire 1 has a tread edge formed by a plurality of circumferential grooves 2 on a tread surface 10 and a plurality of lateral grooves 3 arranged in a direction intersecting with the circumferential grooves. A block pattern having shoulder blocks 4 along E is formed.

As shown in FIG. 2, the pneumatic tire 1 has a tread portion 12, a sidewall portion 13 extending radially inward from both sides of the tread portion 12, and a bead positioned inside the sidewall portion 13 in the tire radial direction. A carcass 16 that turns the bead core 15 of the bead portion 14 from the tread portion 2 through the sidewall portion 13 from the inside to the outside in the tire axial direction, and a tread portion 12 And a belt layer 17 disposed inside the carcass 16 in the radial direction, and a bead apex 18 having a triangular cross section is raised outside the bead core 15 in the tire radial direction.
7, a reinforcing layer 2 covering the belt layer 17 is provided.
One is placed.

The carcass 16 has at least one carcass cord having a radial or semi-radial arrangement inclined at an angle of 70 to 90 ° with respect to the tire equator C in this embodiment, and one carcass cord in this embodiment. An organic fiber cord such as nylon, polyester, or aromatic polyamide is used as the carcass cord.

The belt layer 17 comprises two belt plies in this embodiment, and each belt ply is made of nylon,
A belt cord made of an organic fiber cord such as polyester or aromatic polyamide fiber or a steel cord is arranged in a direction crossing each other.

In the present embodiment, on the tread surface 10, the circumferential grooves 2 are arranged in the vicinity of the tread edge E and two central circumferential grooves 2A, 2A sandwiching the tire equator C. It has two lateral circumferential grooves 2B, 2B and a lateral groove 3B.
... extend from the tread edges E on both sides toward the center of the tread near the tire equator C, and are connected to each other at the center. The lateral groove 3 is formed as an inclined groove in which the tire equator C rises in the tire traveling direction. Therefore, in the present embodiment, the lateral groove 3 is formed with directionality.

Further, between the central circumferential groove 2A and the side circumferential groove 2B, intermediate circumferential grooves 3C connecting the adjacent lateral grooves 3 and inclined with respect to the tire equator are provided. Intervenes.

Each of the circumferential groove 2 and the lateral groove 3 has a groove width GW of 0.04 to 0.12 times the tread width WT,
The groove depth GH is set to 0.06 to 0.1 of the tread width WT.
It is set to a range of 6 times.

In this embodiment, the shoulder block 4
The circumferential groove 2A on the side, the intermediate circumferential groove and the adjacent two grooves
It has a generally fan-like shape that is long in the tire axis direction and surrounded by the horizontal grooves 3.

Here, in a single shoulder block 4, the distance in the tire circumferential direction between the earliest landing point F of the shoulder block 4 and the last landing point R of the shoulder block 4 is the block circumference length. A is defined. This shoulder block 4 is connected to the final landing point R and has a lateral groove 3.
0.2 mm of the block peripheral length A from the rear edge 5 facing
A plurality of sipes 6 are formed in a region B until a distance of 5 times or more and 0.5 times or less is separated to the first-arrival side.

The siping 6 is inclined in the area B with the first arrival side outward in the tire axial direction, and the angle θ is 30 ° or more and 60 ° or less. The leading end of the siping 6 facing the first arrival side is interrupted at the boundary of the region B or is opened in the circumferential groove 2A on the side. Are arranged in parallel with each other by being inclined at the same angle θ, and the pitch length P in the tire axial direction between the centers of the adjacent sipes 6 is 3 The range is about 5 mm. Pitch length P is 3
If it is less than 5 mm, there is a danger of missing the rubber in the shoulder block 4. If it exceeds 5 mm, the rubber thickness between the sipes 6 and 6 increases, and the rigidity of the block 4 in the region B increases. This is because uneven wear easily occurs.

The siping 6 has a siping width t perpendicular to the groove center line of 0.03 mm or more and 0.8 mm or less in a normal state where the tire is assembled on a rim and a normal internal pressure is applied. If it is less than 0.03 mm, it is difficult to process the siping, and if it is more than 0.8 mm, stone biting is likely to occur during traveling, and there is a risk of breakage such as chipping of the shoulder block 4.

The siping 6 is not only a straight line but also a tilt angle θ.
If it is within the above range within the region B, it may extend in a curved shape, or may have a zigzag shape in which the inclination of the direction line is restricted to the angle θ.

The siping 6 has a tread surface 1
The depth h in the direction of the normal line N to 0 is the block height H of the shoulder block 4 provided with the siping 6, that is, the depth h of the circumferential groove 2 and the lateral groove 3 surrounding the block. It is set to be 25 times or more and 0.65 times or less. FIG. 6 shows the ratio (h / h) of the siping depth h to the block height H.
3 shows the relationship between H) and the wear amount of the heel and toe and the occurrence rate of rubber chipping with respect to H). The heel and toe wear amount is remarkable when the depth ratio h / H is less than 0.25, that is, when the depth h is small. I do. Therefore, in order to prevent both uneven wear and rubber chipping, the depth ratio h / H is set to 0.25 or more and 0.6 or more.
It is preferably set to 5 or less.

The siping 6 may be located on the normal line N, may be inclined with respect to the normal line, or may be a bent groove.

The tread pattern can be formed as a rib block pattern having a rib at the center by forming the lateral groove 3 extending from both sides as a discontinuous groove interrupted near the tire equator C.

[0029]

[Specific example] The tire size is 205R16 and FIG.
The tires (Examples 1 to 3) having the configuration shown in Table 1 were prototyped, and their performance was tested. For comparison, a test was also performed on a tire having a conventional configuration (Comparative Example 1) and a tire having a configuration other than the present application (Comparative Examples 2 to 7), and the performances were compared.

The test conditions are as follows. (1) Toe and heel abrasion resistance After the test tire was mounted on an actual vehicle and traveled 40,000 km, the remaining groove depth was measured at 10 places on the first and the last side of the shoulder block, respectively, and the difference d was obtained. Was calculated by the following formula. Comparative Example 1 dm of tire / dm × 100 of test tire The larger the value, the better.

(2) Wear at the first arrival point side After traveling 40,000 km in the same manner as in (1), the depth of the shallow groove was measured at 10 places at the edge of the first arrival block of the shoulder block. Calculated. Average shallow groove of test tire / average remaining groove of comparative example 1 tire ×
100 The higher the numerical value, the better.

(3) Braking Performance On a dry road surface, the distance from when the vehicle was locked to when the vehicle was suddenly braked at a speed of 80 km / H until it stopped was measured, and evaluated by the following equation. Comparative Example 1 Stopping distance of tire / Stopping distance of test tire ×
100 The higher the numerical value, the better.

(4) Wet grip performance 80 km on a wet control road surface with a water depth of 3 mm
From the rate of / H, a test was performed using the same method as in (3) and evaluated. Table 1 shows the test results.

[0034]

[Table 1]

[0035]

As described above, the pneumatic tire of the present invention has the following features.
In the region located on the rear arrival side of the shoulder block, the gist is to form a plurality of sipes each of which inclines the first arrival side outward in the tire axial direction. Without
Uneven wear, such as heel and toe wear, which tends to occur on the rear arrival side of the shoulder block can be prevented, and the durability of the tire can be increased.

[Brief description of the drawings]

FIG. 1 is a developed plan view showing a tread pattern according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a sectional view showing siping.

FIG. 4 is a graph showing the relationship between the inclination angle of siping and the amount of heel and toe wear.

FIG. 5 is a graph showing a relationship between a circumferential length of a region B, a heel and toe wear amount, and a rubber chipping occurrence rate.

FIG. 6 is a graph showing a relationship between a ratio of a siping depth to a block height, a heel and toe wear amount, and a rubber chipping occurrence rate.

FIG. 7 is a developed perspective view showing a tread pattern of a conventional tire.

[Explanation of symbols]

 2, 2A, 2B, 2C Circumferential groove 3 Lateral groove 4 Shoulder block 5 Rear edge 6 Siping 7 Tread surface A Block circumferential length B Area E Tread edge F First arrival point N Normal R Last arrival point θ Angle

Claims (2)

(57) [Claims] 1. A pneumatic tire having a block pattern and a rib block pattern having a shoulder block disposed on both sides of a tire along a tread edge by a circumferential groove and a lateral groove, wherein the shoulder block is rotated as the tire rotates. Of the block circumferential length A, which is the distance in the tire circumferential direction between the earliest landing point that comes in contact with the first and the last landing point that comes in last, is not less than 0.25 times and not more than 0.5 times. ,
In a region B extending from the trailing edge facing the lateral groove and separated from the trailing edge facing the lateral groove to the leading side, the leading sides are respectively directed outward in the tire axial direction and 30 ° to the tire axial direction.
A pneumatic tire characterized by forming a plurality of sipes inclined at an angle of not less than 60 °. 2. The siping according to claim 1, wherein a depth h in a direction normal to a tread surface is not less than 0.25 and not more than 0.65 times the height H of the shoulder block. The pneumatic tire as described.