JPH115409A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the abrasion resistance and stability of operation without lowering the wet performance by setting an angle between a cord and a narrow groove of the most outside belt layer of a pneumatic radial tire within the specified numeric range. SOLUTION: A center block 18, a second block and a shoulder block arranged in a tire equatorial surface CL side, which are blocked by plural circumferential main grooves 14 and plural lateral grooves 16 formed in a tread of a pneumatic radial tire. Angle θ to be formed by a cord 26 of the most outside belt layer 24, which is provided adjacent inside of the tire radial direction and which is made of non-drawing cord such as a steel cord and which is inclined at 0-several degree in relation to the tire radial direction (direction A), is set at 75-105 degree so as to restrict the drawing of the center block 18 in the cord direction, and while enlargement of the groove width of the narrow groove 28 at the time of charging inner pressure is restricted.

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, and more particularly to a pneumatic radial tire used for heavy-duty vehicles such as trucks, buses, and small trucks, and having a block on a tread tire equatorial plane side.

[0002]

2. Description of the Related Art Among pneumatic radial tires used for heavy-duty vehicles such as trucks, buses and light trucks, there is a pneumatic radial tire having a block on the tire equator side of a tread. In this block, a narrow groove extending along the tire axial direction is formed to obtain wet performance.

[0003]

However, when a narrow groove is provided in a block, there is a problem that the rigidity of the block is reduced, thereby causing a decrease in wear resistance and steering stability.

[0004] In view of the above fact, it is an object of the present invention to provide a pneumatic radial tire capable of simultaneously satisfying the three performances of wet performance, steering stability and wear resistance.

[0005]

The inventor has conducted various investigations and experiments on a conventional pneumatic radial tire for a heavy-duty vehicle, and as a result, the width of the narrow groove can be increased by filling the tire with internal pressure. It was found that the proportion of the area of the narrow groove per contact area of the block increased, and the rigidity of the block decreased, causing a decrease in wear resistance. Also,
In a conventional pneumatic radial tire for heavy-duty vehicles, the angle between the direction of the narrow groove provided in the block and the direction of the cord of the outermost layer belt is less than 75 ° or 105 °.
Was over.

[0006] In order to examine the relationship between the cords of the outermost layer belt and the narrow grooves, the inventor prototyped a block sample and examined the relationship between the angle between the cords and the narrow grooves and the block rigidity.

First, as shown in FIG. 5, an embedded rubber sheet 102 of steel cords 100 arranged in a cord shape.
(200mm x 200mm x 5mm) rectangular block 104
A plurality of rigid test samples (150 mm × 150 mm × 20 mm) integrated with each other were produced, and a narrow groove 108 was carved in a block 104 of the rigid test sample to form a test piece 106.
Note that a plurality of test pieces 106 having different angles of the narrow grooves 108 with respect to the steel cord 100 were produced.

[0008] As shown in FIG.
The transparent acrylic plate 11 with the block 104 facing downward.
0, a load W is applied to the test piece 106, and the test piece 106 is pulled in the horizontal direction (the direction of arrow F: a direction corresponding to the tire circumferential direction). TV camera 112
And the amount of change in the width of the narrow groove was measured.

As a result of the test, the change in the width of the narrow groove
At 90 ° with respect to the steel cord 100 is the smallest (see FIG. 7 (A)), and the change increases as the distance from 90 ° increases (see FIG. 7 (B)).

The results of the test are shown in the graph of FIG. The numerical value on the vertical axis of the graph represents the amount of change in the width of the narrow groove as a rigidity index, and is expressed as an index with 100 when the angle between the narrow groove 108 and the steel cord 100 is 90 °. Note that the smaller the numerical value, the lower the block rigidity.

From this graph, it can be seen that the block rigidity can be maintained high (index of 90 or more) by setting the angle between the narrow groove 108 and the steel cord 100 to 75 to 105 °. It is also found that it is preferable that the angle is preferably 85 to 95 °, that is, substantially orthogonal.

When the angle between the cord of the outermost belt layer and the narrow groove is in the range of 85 to 95 °, the expansion of the narrow groove during the internal pressure filling can be suppressed most effectively.

The invention described in claim 1 has been made in view of the above fact, and is provided with a carcass straddling in a toroidal manner between a pair of bead cores, and a carcass disposed radially outside the carcass, A belt including a plurality of layers of a belt layer obtained by rubberizing a plurality of cords, and a tread disposed radially outward of the belt, the tread having a block at least on a tire equatorial plane side, The block is a pneumatic radial tire in which a narrow groove is formed, wherein an angle between a cord of the outermost belt layer and the narrow groove is in a range of 75 to 105 °.

Next, the operation of the pneumatic radial tire according to the first aspect will be described. The pneumatic radial tire expands due to the filling of the internal pressure, and tension acts on the tire surface portion. At this time, the tread is affected by the adjacent outermost belt layer.

On the other hand, in the belt layer, since a plurality of non-extensible cords are arranged in a cord shape, they hardly extend in the cord direction.

Therefore, if the direction of the narrow groove of the block is made substantially perpendicular to the direction of the cord of the belt layer adjacent to the block, the extension of the block in the cord direction can be suppressed.
As a result, expansion of the groove width can be suppressed.

In the pneumatic radial tire of the present invention, the angle between the cord of the outermost belt layer and the narrow groove of the block on the equatorial plane of the tire is set to a substantially right angle in the range of 75 to 105 °. The expansion of the narrow groove at the time is suppressed. This suppresses a decrease in rigidity of the block on the tire equatorial plane side, and suppresses a decrease in wear resistance.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a pneumatic radial tire according to the present invention will be described with reference to FIGS.

The pneumatic radial tire 10 of the present embodiment
The carcass straddles in a toroidal manner between a pair of bead cores, a belt composed of a plurality of belt layers arranged on the outside in the tire radial direction of the carcass and rubberized a plurality of cords, And a tread arranged radially outside the tire.

As shown in FIG. 1, a plurality of circumferential main grooves 14 and a plurality of lateral grooves 16 are formed in a tread 12 of a pneumatic radial tire 10 according to the present embodiment. Tire equatorial plane C divided by 16
The vehicle includes a center block 18 disposed on the L side, a second block 20 disposed on both sides of the center block 18 in the tire width direction, and a shoulder block 22 disposed on both sides of the second block 20 in the tire width direction.

Each of the center block 18, the second block 20 and the shoulder block 22 is formed with a narrow groove 28 extending substantially along the tire width direction. In addition,
The narrow groove 28 divides each block into two sub-blocks.

As shown in FIG. 2, the cord 26 of the outermost belt layer 24 adjacent to the tread 12 in the tire radial direction is used.
Is a non-extensible cord such as a steel cord that is inclined at 0 to several degrees with respect to the tire radial direction (the direction of arrow A).

Here, the angle θ between the narrow groove 28 formed in the center block 18 and the cord 26 of the outermost belt layer 24 is in the range of 75 ° to 105 °, preferably 85 °.
It is set within the range of ~ 95 °.

Next, the operation of the pneumatic radial tire 10 of the present embodiment will be described. In the pneumatic radial tire 10 according to the present embodiment, the angle θ formed between the cord 26 of the outermost belt layer 24 and the narrow groove 28 is in the range of 75 to 105 °, so that the elongation of the center block 18 in the cord direction is suppressed. Therefore, it is possible to suppress an increase in the groove width of the narrow groove 28 during the internal pressure filling.

As described above, since the expansion of the width of the narrow groove 28 of the center block 18 can be suppressed, the reduction in block rigidity of the center block 18 is small, and the reduction in wear resistance can be suppressed. Furthermore, the center block 18
Therefore, a decrease in block rigidity can be suppressed, so that a decrease in steering stability can also be suppressed. (Test Example) In order to confirm the effects of the present invention, a conventional tire and an example tire (TBR 315 /
80R22.5) and abrasion resistance, steering stability,
A comparison was made for wet performance.

Example tire: The tire described in the above embodiment (see FIGS. 1 and 2), and the angle θ formed between the narrow groove 28 formed in the center block 18 and the cord 26 of the outermost belt layer 24. Is a tire set at 85 °.

Conventional tire: A tire having a tread pattern shown in FIG. 3, and a narrow groove 122 formed in a center block 120 and an outermost belt layer 1 as shown in FIG.
This is a tire in which the angle θ between the tire 24 and the cord 126 is set to 60 °. The tread pattern of the example tire and the tread pattern of the conventional tire are symmetrical.

The dimensions of the center block 18 of the example tire and the center block 120 of the conventional tire are 40 mm in the tire circumferential direction, 38 mm in the tire width direction, and 23 mm in height. The dimensions of the narrow groove 28 of the example tire and the narrow groove 122 of the conventional tire are 2 mm in groove width and 1 in groove depth.
5 mm.

Abrasion resistance test method: The tires were mounted on four vehicles of European users, and the amount of wear when the running distance reached 100,000 km was measured, and the average value was determined.

The evaluation was made in the form of an index with the conventional tire being 100. The larger the value, the better the wear resistance (the smaller the amount of wear).

Driving stability test method: The test was conducted on a dry asphalt road test course. Lane changes were performed at various speeds between 40 and 80 km / h, and the behavior of the vehicle at that time was evaluated by the feeling of the test driver.

The conventional tires are represented by an index with 100 as the index. In addition, it shows that steering stability is so excellent that a numerical value is large.

Wet performance test method: Performed on a test course with a water depth of 1.0 mm. The stopping distance from 30 km / h was measured, and the evaluation was made in the form of an index with the conventional tire set to 100.

The larger the value, the better the wet performance (the shorter the stopping distance).

[0035]

[Table 1]

As a result of the test, it is understood that the tires of the present invention to which the present invention is applied are superior to the conventional tires in abrasion resistance, steering stability and wet performance.

[0037]

As described above, the pneumatic radial tire according to the first aspect is configured as described above, so that a decrease in block rigidity on the tire equatorial plane side having a high contact pressure can be suppressed. It has an excellent effect that abrasion resistance and steering stability can be improved without lowering wet performance than before.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic radial tire according to an embodiment of the present invention.

FIG. 2 is an enlarged plan view of a tread partly in section.

FIG. 3 is a plan view of a tread of a tire according to a conventional example.

FIG. 4 is an enlarged plan view of a tread in which a part of a tire according to a conventional example is sectioned.

FIG. 5 is a perspective view of a test piece.

FIG. 6 is an explanatory diagram of a test method for rigidity of a test piece.

FIGS. 7A and 7B are explanatory diagrams showing a state of a block of a test piece observed by a television camera.

FIG. 8 is a graph showing a relationship between an angle θ between a narrow groove and a steel cord and a narrow groove width.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic radial tire 12 Tread 18 Center block (block) 24 Outermost belt layer 26 Code 28 Narrow groove

Claims (1)

[Claims] 1. A carcass that straddles in a toroidal manner between a pair of bead cores, and a belt that is disposed radially outside of the carcass and that includes a plurality of belt layers formed by rubberizing a plurality of cords. A tread disposed radially outside the belt in the tire radial direction, wherein the tread has a block at least on the tire equatorial plane side, and the block is a pneumatic radial tire having a narrow groove formed therein. The angle between the cord of the outer belt layer and the narrow groove is 75 to 1
A pneumatic radial tire characterized by being in the range of 05 °.