JPS592641B2 - Radial pneumatic tires for heavy vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial pneumatic tire for heavy vehicles, and more specifically, to a tire with four main groove ribs used for driving on general highways, it is capable of preventing uneven wear that tends to occur frequently, especially in the front wheels. ,
This invention relates to a radial pneumatic tire for heavy vehicles that has been improved so that various performances required of the tire can be reduced without impairing them.

In general, a radial pneumatic tire for heavy vehicles (hereinafter referred to as radial pneumatic tire for heavy vehicles) equipped with a steel cord belt layer is located between the carcass, which consists of cords arranged in the radial direction with respect to the tire's equatorial plane, and the part corresponding to the ground contact part of the tire, that is, the tread. Radial tires (radial tires) have become extremely popular recently because they have many advantages over bias-ply tires, such as wear resistance, puncture resistance, low fuel consumption, low heat generation, and low noise.

However, in the case of the above-mentioned radial tires, as mentioned above, since there is a highly rigid belt layer in the tire club and run part, the stiffness of the shoulder part is inferior to that of the tire center part, and the shoulder part tends to move easily. There is.

For this reason, parts of the left and right shoulders of the tread are more likely to wear than parts of the center of the tread, and as a result, so-called uneven wear is more likely to occur.

In particular, the tires installed on the front wheels have toe-in and camber.
Due to the influence of wheel alignment, etc., there is a strong tendency for uneven wear in a part of the shoulder.

In the first place, this type of radial tire is often used under very harsh conditions such as heavy loads and continuous high-speed running, and in the past, the lifespan was shortened due to failure of so-called casings such as belt separation and chafer separation. was a big problem.

However, recently, improvements have been made in the materials used in tires to address these problems, and the occurrence of these types of failures has become extremely rare.

Recently, shortened lifespan due to premature wear caused by the aforementioned uneven wear of the tread has become a major problem.

The uneven wear that occurs in this type of pattern is: (1) Sliding wear in which a part of the shoulder wears faster than a part of the crown center, and (2) Wave-like wear in which the shoulder ribs of the tread wear in a wave-like manner. The wear occurs from a part of the crown center to a part of the shoulder as shown by diagonal lines in Fig. 2a, and the wave-like wear occurs in the rotational direction of the tire as shown by diagonal lines in Fig. 6a. On the other hand, the shaded area is b1 in Figure 6.
As shown here, it wears in a wave pattern.

Particularly 1. As shown in FIG. 1, in the conventional four main groove type radial tire, the ratio B/W of the shoulder rib width B to the tread width W was less than 17%.

During driving, such tires often wear out earlier in the shoulder than in the crown center, which is so-called sliding wear.As mentioned above, improvements in the materials used in tires have prevented this uneven wear from occurring in the casing. Nowadays, the number of failures in tires has become very low, and this is the main cause of reduced tire life.Moreover, tires that have suffered from this sliding wear have a rounded tread surface, so there are cases where proper puff radius cannot be obtained and retreading is not possible. Many were extremely uneconomical.

An object of the present invention is to reduce the uneven wear that occurs in a radial pneumatic tire for heavy vehicles having a rib-type tread pattern with four main grooves as described above, without impairing other required characteristics of the tire, thereby extending the life of the tire. It is an object of the present invention to provide a radial pneumatic tire for heavy vehicles that is significantly improved and can facilitate tire retreading.

The radial pneumatic diamond for heavy vehicles according to the present invention that achieves the above object has a total of four zigzag-shaped main grooves arranged in the circumferential direction of the tread, two on each side of the circumferential center line,
In a radial pneumatic diamond for heavy vehicles having a rib-type tread pattern in which ribs are formed in five areas divided into these main grooves, the width B of both left and right shoulder ribs of the tread pattern is 18% to 22% of the tread width W1. %, and the width C of the main groove in the direction perpendicular to the tread circumferential direction is in the range of 4% to 8% of the tread width W, and the point bite D of the main groove is within the tread width W.
It is characterized by being set at 2% to 7%.

Embodiment 1 The radial pneumatic tire for heavy vehicles of the present invention will be described below with reference to the drawings, starting with Example 1.

The radial pneumatic tire E for heavy vehicles of the present invention shown in FIG. By arranging the grooves 2', 2, 2, 2', the tread can be divided into a central area A and an area A2 that surrounds this central area A.
．． A1. A1. A tread formed with a rib-type tread pattern divided into five areas in total, a carcass consisting of cords arranged in the radial direction with respect to the tire equatorial plane, and a belt layer arranged between the carcass and the tread. In the radial pneumatic tire for heavy vehicles, the width B of both left and right shoulder ribs of the tread pattern is set in a range of 18% to 22% with respect to the tread width W,
Further, the width C of the main grooves 2', 2, 2, 2' in a direction perpendicular to the circumferential direction of the tire is 4% with respect to the tread width W.
-8%, and the main grooves 2', 2, 2
, 2' are set in a range of 2% to 7% with respect to the tread width W.

Next, the circumstances leading to the above-mentioned present invention and the results of experiments will be explained in detail.

The present inventor focused on the ratio of the shoulder rib width B to the tread width W and determined how to reduce the uneven wear described above without impairing the various performances required of the tire. As a result of experiments conducted with tires with various ratios, it was found that the higher the ratio, the less shoulder drop wear occurs, but conversely the durability of the belt portion decreases.

After further examining these results and conducting experiments, we succeeded in obtaining a ratio that could reduce slip-off wear without impairing the durability of the belt section.

In other words, sliding wear is strongly controlled by the rigidity of both the left and right shoulder ribs adjacent to the outside of the zigzag-shaped main groove 2' continuous in the circumferential direction of the tire, that is, by the shoulder rib width B. If the shoulder rib width B is narrow, Rib rigidity becomes weaker,
The shaded area in FIG. 2a shows the occurrence of slip-off wear, which causes premature wear.

FIG. 2B shows its cross section.

However, if the shoulder rib width B becomes too wide, the amount of rubber increases in the part that moves the most, and although heat generation increases, the heat dissipation area decreases by 1, which causes belt separation that increases heat by 1.

Therefore, it is important to balance the abrasion resistance due to the shoulder rib width and the heat dissipation performance due to the shoulder rib width.

As a result of the experiment, when the ratio B/W of the shoulder rib width B to the tread width W is less than 18%, the durability of the belt part is at a good level in the indoor durability test, but the amount of sliding wear is large, As the ratio becomes smaller, the amount of sliding wear increases rapidly.

Further, when the ratio is greater than 22%, the amount of sliding wear is very small and uneven wear is good, but the durability of the belt portion shows a sharp decline.

Therefore, the appropriate range of the ratio B/W that simultaneously satisfies both the durability of the slip-off wear-resistant sleeve and the belt part is 18% to 2.
It was concluded that 2%.

Next, under the condition that the ratio B/W of the shoulder rib width B to the tread width W is 18 to 22%, the width C of the main grooves 2 and 2' was varied and examined. When the main groove width was less than 4%, the actual contact area at the time of contact with the ground increased and wear resistance improved, but on the other hand, the drainage effect of the grooves decreased and braking performance on wet roads decreased. I found out that it does.

Also, when the main groove width is wider than 8% of the tread width 1ζ, the drainage effect of the grooves is large and the braking t'A on a wet road surface is
= -1i, although there were no problems, the width of the three ribs in the crown center became very narrow, which weakened the rib rigidity and showed a tendency for centerwear.
It was found that another type of uneven wear called rib patching (see Figures 5a and 5b) occurred on the 2nd and 4th ribs adjacent to the shoulder ribs.

Therefore, when the ratio of the shoulder rib width B to the tread width W is B/WfJ (in the range of 18 to 22%), it is optimal that the ratio of the main groove width C to the tread width W is in the range of 4 to 8%. The conclusion was obtained.

Furthermore, as a result of various studies on the point bite D of the main grooves 2 and 2' under the condition that the ratio B/W of the shoulder rib width B to the tread width W is 18 to 22%, the point bite D with respect to the tread width was When the bite was less than 2%; c. The main groove became almost straight, resulting in insufficient traction in the traveling direction, and at the same time, the deterioration of braking performance due to slipping became significant.

Further, when the point bite was larger than 7% with respect to the tread width, another type of uneven wear called wavy wear occurred on the shoulder ribs.

Therefore, when the ratio B/W of the shoulder rib width B to the tread width W is in the range of 18 to 22%, the ratio of the tread width W of the point bite D of the main groove to this is 2 to 7%.
It was concluded that the optimum range is .

Furthermore, the ratio B/W of the shoulder rib width B to the tread width W1 is 18 to 22%, and the ratio C/W of the main groove width C to the tread width Wt is 4 to 8%, and Ratio D/W of main groove point by hD to tread width W
As a result of evaluating tires that meet the conditions of 2 to 7%, the braking performance was good and uniform, with no tendency for center wear and no uneven wear (rib punching, wavy wear). Of course, the decrease in the durability of the belt was slight and did not pose any practical problems.

Hereinafter, a detailed description will be given based on examples.

The contents of the test tires and test conditions are as follows.

☆ Contents of the test tire (10,0OR20-14,PR
) Test conditions In-house actual vehicle test Size: 10.0OR2014PR Internal pressure: 7.25 kg/C11￥') Mounia, 50V x 20 Load:
2500kg/Mounting position: Front wheel Road surface: 100% paved road Mileage: 200.0Ian Speed: 30-80Ian/h Indoor durability test size: 10.0OR20]4PR Internal pressure: 7.25kg/= Rimnia , 50V
corresponds approximately to an application example according to the present invention.

FIG. 3 shows the four types of test tires S and T mentioned above.

Ratio B of shoulder rib width B to tread width W when Y is run for approximately 20,000 b under the above-mentioned actual vehicle test conditions
FIG. 3 is a diagram showing the relationship between /W and the amount of sliding wear.

Figure 4 also shows four types of test tires S, T, X,
The figure shows the relationship between the ratio B/W and the belt durability index when the Y was run under the indoor durability test conditions described above.

The results of these two tests are shown in the following table.

The embodiment according to the present invention (T, X, Y) is different from the conventional pattern (
Compared to S), the amount of sliding wear in the actual vehicle test was reduced to about 1/4 to about 1/12, showing evidence of a significant effect.

Moreover, regarding the durability in the durability test, Example (T)
is almost the same as in the conventional case, and although a slight decrease is seen in Example

However, in Example (g), the level is reduced to about half of the conventional level.

In FIGS. 5a and 5b, the ratio B/W of the shoulder rib width B to the tread width W is 18% (corresponding to Example T),
FIG. 3 is a diagram showing rib punching that occurs in pattern 1 in which the ratio C/W of the main groove width C to the tread width W is 9%.

The shaded area is the area where rib punching occurred.

FIG. 5a shows the cross section FF.

When the amount of wear is f, the relationship between f and C/W is as shown in FIG.

It can be seen that the amount of wear of the rib punch increases rapidly when the ratio of the main groove width to the tread width exceeds 8%.

Figure 6a shows the shoulder rib width B relative to the tread width W.
The ratio B/W is 18% (corresponding to Example T), and the ratio D/W of point-by-ID of the main groove to the tread width W is
FIG. 3 is a diagram showing wave-like wear that occurs in a pattern containing 8% W.

The shaded area is the worn part.

In FIG. 6, the cross sections G to G are shown.

Letting the amount of wear be g, the relationship between g and D/W is as shown in FIG.

It can be seen that the amount of wave wear increases rapidly when the ratio of the main groove point bite to the tread width exceeds 7%.

In addition, in the embodiment of the present invention shown in FIG. 9, B/W=
18.6%, C/W=6.0%, D/W-2.2%.

As described above, the present invention arranges a total of four zigzag-shaped main grooves, two on each side of the circumferential center line in the circumferential direction 1 of the tread, and five ribs divided by these main grooves. In a radial pneumatic tire for heavy vehicles having a rib-type tread pattern, the width B of both left and right shoulder ribs of the tread pattern is 18% to 18% of the tread width W.
The width C of the main groove in the direction orthogonal to the tread circumferential direction is within the range of 4 to 8% of the tread width W, and the point bite D of the main groove is within the tread width W. 2% to 7%, the uneven wear, especially the sliding wear, which tends to occur frequently in the tread pattern of the four main groove rib type radial pneumatic tires for heavy vehicles, which has become a major problem. , wavy wear, rib punching, shoulder rib width relative to tread width, main groove width,
By appropriately setting the ratio of main groove point bite, etc., it is possible to effectively reduce tread wear without impairing other characteristics required for the tire, such as belt durability, main groove drainage effect, and traction. It is possible to make the tires more uniform and significantly extend the life of the tires.

At the same time, since tread wear becomes more uniform as described above, an appropriate puff radius can be obtained during retreading, and the factor of uneven wear among the factors that prevent retreading can be eliminated.

[Brief explanation of drawings]

Fig. 1 is a pattern development diagram showing the tread pattern of a conventional radial pneumatic tire for heavy vehicles that has one and four main grooves in the circumferential direction, and Fig. 2a shows uneven wear that occurs in the conventional pattern, especially slippage. A pattern development diagram showing wear, Figure 2 is a sectional view taken along line E-E in Figure 2A, Figure 3 is a diagram showing the ratio of the shoulder rib width B to the tread width W (a diagram showing the relationship between OA and sliding wear e, Figure 4 is a diagram showing the relationship between OA and sliding wear e). The figure shows the ratio of the shoulder rib width B to the tread width W1 (a figure showing the relationship between OA and the belt durability index, Figure 5 a is a pattern development diagram showing uneven wear and especially one rib patching, Figure 5 Figure 6a is a sectional view taken along line F-F in Figure 6a, and Figure 6a is a pattern development diagram showing uneven wear, especially wavy wear.
Figure 7 is a diagram showing the relationship between the ratio of the main groove width C to the tread width W and the amount of rib punching wear g, and Figure 8 is a diagram showing the relationship between the ratio of the main groove width C to the tread width W and the amount of rib punching wear g. FIG. 9 is a diagram showing the relationship between the percentage of main groove point bite D and the amount of wavy wear g, and FIG. 9 is a developed tread pattern diagram showing an embodiment of the present invention. 1... Tread, 2, 2'... Main groove,
A...Central area, A1. A2...Area sandwiching the center area, B...Curved shoulder rib width, W...
...Tread width, C...Main groove width, D...
・Point part-time job.

Claims (1)

[Claims] 1. In the circumferential direction of the tread, 2 on both sides of the circumferential center line.
A radial pneumatic diamond for heavy vehicles having a rib type tread pattern in which a total of four zigzag-shaped main grooves are arranged and five ribs divided by these main grooves are formed. The left and right shoulder rib width B is in the range of 18% to 22% of the tread width W,
The width C of the main groove in the direction orthogonal to the tread circumferential direction is in the range of 4% to 8% of the tread width W, and the point hide D of the main groove is 2% to the tread width W.
A radial pneumatic tire for heavy vehicles characterized by a pneumatic tire set at % to 7%.