JPH04103411A - Heavy load pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the performance of anti-skidding on a frozen road without sacrificing other demanded performances, by providing auxiliary grooves having a specific angle against a tire peripheral direction so as to run through blocks within the specific range of tread width. CONSTITUTION:At a tire, three peripheral main grooves 11-13 are formed in continuation, and sub-grooves 21, 22, 31, 32 are provided at ribs formed by these, and a block pattern tread portion is formed. And a plurality of sipes 41, 46 intersecting in the tire peripheral direction are provided at respective blocks 40, 45. In this instance, respective continuous two auxiliary grooves 51, 52 are provided in the tire peripheral direction so that they may run through blocks 40, 45 within the range in which a distance W from the tread center line 60 to a tread width TW is 0.2 or less. And the width GW of each auxiliary groove 51, 52 to the width TW is set at 0.02-0.03.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-duty pneumatic radial tire for trucks, buses, etc.

[Prior Art and Problems to be Solved by the Invention] Conventionally, in the field of heavy-duty tires, so-called spike tires, in which bottles are driven into the tire tread, have been common for winter use. However, since spiked tires scrape the road surface and cause dust pollution, the development of studless tires is desired.

This type of studless tire has multiple main grooves continuous in the tire circumferential direction, sub-grooves in each rib to form a block, and each block has a large number of sipes that intersect in the tire circumferential direction. Those having a tread pattern are known.

Now, the required performance on frozen roads is braking, starting, indexing,
Performance such as skidding resistance can be mentioned, but the ability to prevent skidding is especially important. This is because, unlike other performances, it is difficult for drivers to compensate for this with driving techniques. Insufficient anti-skid performance may cause a so-called jackknife phenomenon, for example, when a trailer is running, resulting in a serious accident.

However, it has been difficult to obtain sufficient anti-skid performance with the conventional tires in which each block is simply provided with a large number of sipes.

The present invention achieves the following by improving the groove device of the tire tread.
An object of the present invention is to provide a pneumatic radial tire for heavy loads that has improved anti-skid performance on frozen roads without sacrificing other required performances.

[Means for Solving the Problems] The heavy-duty pneumatic radial tire according to the present invention has a tire circumferential direction such that the distance W from the tread center line to the tread width TW is 0.2 or less across the block. A plurality of continuous auxiliary grooves with an angle of 5° or less are provided, and the width GW of each auxiliary groove with respect to the tread width TW is set to be 0°02 or more and 0.03 or less.

[Function] In general, a portion of the tread shoulder has a lower ground pressure than a portion of the tread center, and when the vehicle is under a low load such as when the vehicle is empty, the ground pressure of a portion of the tread shoulder becomes extremely low. On the other hand, in a part of the tread center where the distance W from the tread center line to the tread width TW is 0.2 or less, the ground contact pressure is highest, as will be explained later with an example, and when the load changes. The ground pressure change is also very small. Therefore, in this range, a large frictional force with the road surface can be stably obtained.

In the heavy-duty pneumatic radial tire according to the present invention, a plurality of auxiliary grooves facing approximately in the circumferential direction of the tire are continuously provided in this range where a large frictional force can be stably obtained.
The edges of the block rubber formed by providing these grooves efficiently scratch the frozen road surface when skidding.

By realizing the second major edge effect, skid resistance performance is greatly improved.

If the angle of the auxiliary groove to the tire circumferential direction exceeds 5",
During side skidding, the t angle & between the direction in which the lateral force acts and the block edge formed by forming the auxiliary groove becomes too small, resulting in a small lateral resistance force.

The ratio of the auxiliary groove width GW to the tread width TW is 0.02.
If it is less than that, the block edges that sandwich the auxiliary groove will stick together when receiving lateral force, and the edge effect will disappear. When the ratio of GW to TW exceeds 0.03, the groove area in a part of the tread center becomes too large, making it impossible to obtain sufficient block rigidity, and uneven wear resistance deteriorates.

[Example] FIG. 1 is a partially developed view showing a tread pattern of a heavy-duty pneumatic radial tire according to an example of the present invention.

As shown in the figure, this tire has three main grooves in the circumferential direction.
1, 12, and 13 are continuously formed, and the tread portion has a block pattern in which sub grooves 2], 22, 31, and 32 are provided on the ribs formed thereby. Each block 40.45 is provided with a plurality of sipes 41.46 that intersect in the tire circumferential direction.

Further, the blocks 40 are arranged in a range where the distance W from the tread center line 60 to the tread width TW is 0.2 or less.
．． Two continuous auxiliary grooves 51 and 52 are provided in the circumferential direction of the tire so as to traverse the groove 45. Tread width T
The width GW of each auxiliary groove 51, 5.2 with respect to W is 0.0
It is 2 or more and 0.03 or less.

As shown in FIG. 2, the auxiliary groove 58 may have a zigzag shape. However, the tire circumferential direction 70 of the auxiliary groove center line 73
The angle with respect to the zigzag angle θ must be 5° or less.

FIG. 3 is a graph showing the relationship between the distance from the center line BO and the ground contact pressure in the tread portion of the radial tire of size 10.0OR2014PR. The air pressure filled in the tire is 7.25 kg/cm".However, 1620 kg (empty), 2160 kg, 270 kg
Graphs are drawn for three types of load of 0 kg.

As can be seen from the figure, the ground contact pressure of the tread shoulder portion is lower than that of a portion of the tread center, and especially when the load is low, the ground contact pressure of the tread shoulder portion becomes extremely low. On the other hand, the distance MW from the tread center line to the tread width TW in a part of the tread center is 0.
The ground pressure is highest in the range of 2 or less, and the ground pressure change when the load changes is very small.

Therefore, in this range, a large frictional force with the road surface can be stably obtained.

In the above-mentioned pneumatic radial tire for heavy loads according to this embodiment, the auxiliary grooves 51 and 52 in the tire circumferential direction are continuously provided in this range where a large frictional force can be stably obtained.
The edges 6162, H, 67 (see FIG. 1) of the block rubber formed by providing these grooves efficiently scratch the frozen road surface during skidding. By realizing this large edge effect, the anti-skid performance is greatly improved.

Table 1 shows the results of a skid resistance test and an uneven wear resistance test conducted on 10 tires of the same size (10,0OR2014PR) with different tread patterns. However, tire A-1 has two auxiliary grooves 51.5
2, and tire J is a conventional snow tire. The tread width TW is 206 mm in both cases.

The anti-skid performance index in the same table was obtained based on the lap time measurement results per lap on the frozen circular turning test stand, with Tire J set as 100. However, the larger the value of the index, the better the anti-skid performance. Regarding the uneven wear resistance performance, the maximum measured value of the block level difference in a part of the tread center after 50,000 km of running is shown.

(Left below) Tires A, B, and C show the influence of the auxiliary groove zigzag angle θ on anti-skid performance. When θ is 5″ or less (Tires A and B, however, θ-0° indicates a straight line), the anti-skid performance improves markedly, but when it exceeds 5° (Tire C), the performance does not improve much. I can't see it.

Tires D and E have auxiliary grooves at i! W/
This is a modified version of TW. When W/TW is 0.2 or less (tires A and D), the anti-skid performance is significantly improved, but when it exceeds 0.2 (tire E), the performance does not improve much.

Tires F, G, H, and I are different from Tire A in that the width GW of the auxiliary groove is changed. When GW/TW is 0.02 or more and 0.03 or less (tires A and G), the anti-skid performance is significantly improved compared to the conventional example (tire J) without deterioration of uneven wear resistance. When GW/TW is less than 0.02 (tire F), there is not much improvement in anti-skid performance, and when it exceeds 0.03 (tire H, 1), uneven wear resistance deteriorates.

As mentioned above, θ-0''~5', W/TW≦0.2,
Only in the case of tires A, B, D, and G that satisfy all the conditions of GW/TW-〇, 02 to 0.03, the anti-skid performance on frozen roads can be improved without deteriorating the uneven wear resistance performance. It was shown that

[Effects of the Invention] The heavy-duty pneumatic radial tire according to the present invention has an angle of 5'' with respect to the tire circumferential direction so that the distance W from the tread center line to the tread width TW is 0.2 or less across the block. The following plural continuous auxiliary grooves are provided, and the width GW of each auxiliary groove with respect to the tread width TW is set to 0°02 or more and 0.03 or less, and the tread center can be stably obtained with a large frictional force. Since a plurality of auxiliary grooves of appropriate width are continuously provided in the tire circumferential direction, the grooves provide a large edge effect due to the block rubber formed, and at the same time prevent uneven wear of the block. Therefore, according to the present invention, it is possible to significantly improve skid resistance on frozen roads without sacrificing uneven wear resistance.

[Brief explanation of the drawing]

Figure 'is1 is a partially exploded view showing a tread pattern of a heavy-duty pneumatic radial tire according to an embodiment of the present invention, Figure 2 is a plan view showing a modified example of the auxiliary groove, and Figure 3 is the same as that shown in Figure 1. 2 is a graph showing the relationship between the distance from the center line and the ground contact pressure in the tread portion of the tire. Explanation of symbols 11.12.18...Main groove, 21, 22, 81.12
...Minor groove, 40.45...Block, 41.46.
...Sipe, 51,52.53...Auxiliary groove, 80...
・Tread center line, L...load load, GW・
...Width of the auxiliary groove, TW...Tread width, W...Position of the auxiliary groove (distance from the tread center line), θ・
...Auxiliary groove zigzag angle.

Claims (1)

[Claims] 1. A plurality of continuous main grooves are formed in the circumferential direction of the tire, a sub-groove is provided in each rib to form a block, and a plurality of sipes that intersect in the circumferential direction of the tire are provided in each block. In a heavy-duty pneumatic radial tire with a tread pattern, the angle to the tire circumferential direction is 5 degrees or less so that the distance (W) from the tread center line to the tread width (TW) is 0.2 or less across the block. A pneumatic radial tire for heavy loads, characterized in that a plurality of continuous auxiliary grooves are provided, and the width (GW) of each auxiliary groove relative to the tread width (TW) is 0.02 or more and 0.03 or less.