JPH02254004A - Heavy duty pneumatic radial tire for ice load - Google Patents

Abstract

PURPOSE:To improve the durability of a tire on a dry road and so forth while securing its ice performance by specifying respectively the ratio of groove area in a tread surface, the number of the pitches and their area ratio in a block arrange in a central portion and a shoulder portion, the number of cuts formed in the block and so on. CONSTITUTION:In the tread surface of a tire, plural blocks 3 are formed out of plural main groove 1 and plural sub grooves 2 crossing them. At the central portions 3C of respective block 3, one cut 4 in a radial direction is disposed, and at a shoulder portion 3S, three cuts 4 in a radial direction are disposed respectively. The ratio of groove area in the tread surface is established as 34%-38%. The ratio of total pitches in the central portion 3C and a shoulder portion 3S is established as 2:1 and the area ratios in the central portion 3C and the shoulder portion 3S per pitch are established as 1:1.6-1:1.9 respectively. The groove width of sub groove 2 in the shoulder portion 3S is established as at least 80% of the groove width of the main groove 1.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is intended for use on icy and snowy roads, which improves belt durability and block crack resistance on dry roads without reducing driving performance and braking performance on icy and snowy roads. Regarding heavy-duty pneumatic radial tires.

[Conventional technology]

A conventional pneumatic radial tire for ice and snow roads (hereinafter referred to as a tire for ice and snow roads) has a plurality of polygonal main grooves 1 extending in the circumferential direction of the tire on the tread surface and a main groove l as shown in FIG. It has a tread pattern consisting of blocks 3, which are arranged with a plurality of sub-grooves 2 that cross and connect to the outside of the shoulder, and are divided by these main grooves and sub-grooves, and which increases the driving force on snowy roads. Therefore, Tseng and Tong made the groove area ratio of the main groove and the sub-groove to the tread surface relatively large at 40 to 50χ. In addition, spike pins were driven into a part of the block 3 to improve braking and driving performance, especially on frozen roads, but spike pins have the disadvantage of damaging the road surface and generating dust pollution when driving on dry roads. there were.

In order to eliminate the dust pollution caused by this spiked tire, we installed a radial kerf in the block 3 as shown in Figure 3 in an attempt to create a standless tire that provides good performance on icy and snowy roads without the need to drive in spike bins. There was one in which a plurality of thin cuts 4 were formed to improve performance on ice and snow roads due to the edge effect of the kerf.

However, when the above tires for icy and snowy roads are used for heavy-duty vehicles, the compression force on the tread is high and the pressure distribution becomes large, so the groove area ratio is 40% as described above.
In addition to the large size of ~50χ, if the block is fragmented by the kerf, the strength of the block will decrease, braking performance will decrease, and the shearing force applied during driving and braking on dry roads will cause cracks and cracks in the block. There has been a problem that this tends to occur and durability is impaired.

A possible solution to this problem is to reduce the groove area ratio and increase the area per block (thus increasing the rigidity. However, tires with deep grooves and shoulder If the rubber of the tire is thick, the tire tends to accumulate heat, which tends to cause separation of the belt provided to reinforce the tread.

[Problem to be solved by the invention]

The purpose of the present invention is to improve dry road tires such as crack resistance and belt durability while maintaining excellent braking and driving performance in tires for ice and snow roads in which thin cuts like kerfs are made in blocks arranged on the tread surface. It is an object of the present invention to provide a tire for use on icy and snowy roads for heavy-duty vehicles with improved performance, and particularly to provide a heavy-duty pneumatic tire for use on icy and snowy roads of an ultra-deep groove type.

[Means to solve the problem]

An object of the present invention is to arrange blocks in the circumferential direction of the tire, which are partitioned by three main grooves arranged in the tire circumferential direction on the tread surface and a plurality of sub grooves arranged in a direction intersecting these main grooves. has a trend pattern, the groove area ratio of the tread surface is 34% to 38χ, the total pitch number ratio of blocks arranged in the center part to blocks arranged in the shoulder part is 2:1, and The area ratio of the block in the center part and the block in the shoulder part per pitch is t:t, e~1:1.9, and the block in the center part has one thin radial direction approximately in the center. The block of the shoulder part is provided with three thin cuts in the radial direction at approximately equal intervals, and the width of the minor groove of the shoulder part is at least 8 oz of the width of the main groove. This can be achieved with load tires.

FIG. 1 is a plan view of a trend pattern of a heavy-duty tire for icy and snowy roads, showing an embodiment of the present invention.

As shown in the figure, the tread surface of the tire of the present invention has three main grooves 1 extending in the tire circumferential direction and a plurality of sub grooves 2 in the radial direction intersecting the main grooves 1. Blocks 3 partitioned by sub-grooves 2 are arranged in the circumferential direction of the tire.

Among these block groups, the blocks 3 arranged in two rows in the center part have only one thin cut 4 in the radial direction approximately in the center of the block, and the blocks arranged in one row in both shoulder parts each have a thin notch 4 in the radial direction. 3 is provided with three thin cuts 4 in the radial direction at approximately equal intervals.

In the above-described configuration, the tire of the present invention needs to have a groove area ratio of the tread surface within a range of 34 to 38χ.

In this way, by making the groove area ratio smaller than that of conventional tires for ice and snow roads, the average area per block becomes large, making it possible to exhibit block strength that can withstand heavy loads. In addition, good braking performance can be achieved on frozen roads.

Here, the groove area ratio refers to a value calculated by measuring the ground contact area of the tread under the conditions of maximum air pressure and maximum load specified by JATMA, and according to the formula below.

[Simply reducing the groove area ratio of the tread surface compared to the groove area ratio (40 to 50χ) of conventional tires for ice and snow roads will not improve the strength for heavy loads. Even if countermeasures can be taken, driving performance on snowy roads etc. will deteriorate.

To take such measures, the tire of the present invention has a certain size difference between the blocks arranged in the center part and the blocks arranged in the shoulder part, assuming the above groove area ratio, as explained below. It should be set up.

That is, the ratio of the total number of pitches of blocks arranged in the center part to the total number of pitches of blocks arranged in the shoulder part is set to 2:1, and the number of pitches of blocks arranged in the center part is increased. Further, the ratio of the area per pitch of the block in the center part to the area per pitch of the block in the shoulder part is set in the range of 171.6 to 1:1.9,
The aim is to increase the area of the block in the shoulder section.

Here, the pitch is the smallest unit when the blocks forming the tread pattern are measured in the tire circumferential direction. In addition, the total pinch number ratio is the ratio of the total number of blocks (total number of pitches) per row of blocks arranged in the center part to the total number of blocks (total number of pitches) per row of blocks arranged in the shoulder part. It is.

In the present invention, this total pinch number ratio is set to 2=1,
More specifically, it is preferable that the number of blocks in the center part be around 100 and the number of blocks in the shoulder part be around 50.

Further, in the present invention, the block area per pitch means the average value obtained by dividing the total area of blocks arranged in a row in each center portion or shoulder portion by the total number of blocks.

The reason for setting the total pitch number ratio and block area ratio per pitch between the center part and shoulder part of the tread surface is that the center part mainly contributes to drivability on snowy roads. This is based on the knowledge that the shoulder part greatly contributes to braking performance on icy and snowy roads. Therefore, even if the groove area ratio is smaller than that of conventional tires, the total pitch number ratio of the blocks in the center part is doubled compared to that of the shoulder parts, and the area per pitch of the blocks in the center part is doubled compared to the shoulder part. (By doing so, it is possible to exhibit good snow chewing properties on snowy roads and ensure sufficient drive performance. Also, due to the above relationship, the blocks in the shoulder part have a large area. Because it comes to that,
Demonstrates sufficient braking performance on icy and snowy roads. Additionally, the thin radial notches provided in the block contribute to improved driveability and braking performance on icy and snowy roads. However, the center part receives high ground pressure during driving, and cranks are likely to occur in the thin cut. Therefore, only one thin cut is provided in the center block, which has a relatively small area, and the block has an abbreviation of It must be placed in the center.

On the other hand, since the shoulder block has a larger area than the center block, three thin cuts are provided, and the edge effect improves the braking performance of the tire. However, the number of thin cuts in the shoulder block should be limited to three in order to ensure the block's crack resistance, and should be provided at approximately equal intervals. In addition, the spacing of the thin cuts provided in the blocks of this shoulder section is 5 to 8 during tread development (TDW).
It is desirable to set it to χ.

The depth of this thin cut may be constant for all blocks, or may be changed for each block.

Furthermore, it is preferable that at least one end of the thin cut reaches the edge of the block in order to provide performance on ice and snow roads. Preferably, both ends of the thin notch reach the edge of the block, as shown in Figure 1.The direction of this thin notch may be substantially radial, at a slight angle to the radial direction. It may have. The shape can also be a straight line, a curved line, a broken line, or the like.

Further, the sub-groove provided in the shoulder portion of the tire of the present invention must have a width of at least 80x of the main groove width. This is because relatively large blocks are arranged in the shoulder portion, which results in poor heat dissipation in the drying path, which tends to cause belt separation due to heat accumulation. In particular, in the case of a deep groove type tire for ice and snow roads, the volume of the shoulder portion becomes even larger, which further deteriorates heat dissipation and deteriorates belt durability. Therefore, by setting the width of the sub-groove as described above, it is possible to prevent a decrease in belt durability due to heat accumulation.

Furthermore, the groove depth of the main groove of the tire of the present invention is not particularly limited, but in the case of a deep groove type tire for icy and snowy roads for heavy-duty vehicles, JIS D 4202 r specifications of automobile tires are used. In Explanation Table 9 on page 11, in the section for the maximum groove depth, Extra Heavy Tread [Ext
It is preferable to use the depth applied to tires for ice and snow roads having an extra heavy trend described in the column RA HeavyTread (EHT).

〔Example〕

EXAMPLES Hereinafter, the tire of the present invention will be specifically explained with reference to Examples.

In the examples, braking performance, pitching performance as driving performance, belt durability, and crank resistance were each evaluated by the following methods.

Futagami M dynamic accent: A large vehicle (2/D) was equipped with test tires on all wheels, and braking was applied from 40 km/h on a snowy road, the braking distance at that time was measured, and the value was compared to the comparison tire I. The measured value of 10
Expressed as an index set to 0.

The larger this number is, the better the braking performance is.

Oil content on ice l: Test tires were mounted on all wheels of a large vehicle (2/D), brake was applied from 40 km/h on an icy road, the braking distance was measured, and the value was compared to that of the comparison tire ■. Measured value 10
Expressed as an index set to 0.

The larger this number is, the better the braking performance is.

Nikami climbing standing blood: Test tires were attached to the drive wheels of a large vehicle (2/D), and the time required to climb up a slope from an initial speed of 30 km/h to 200 m on a snow-compacted road was measured. The values are expressed as an index, with the measured value of the comparative tire ■ being 100.

The higher this number is, the better the pitching (driving) performance is.

Pyrotechnical durability: The evaluation tire was installed on an indoor drum testing machine, and the speed was 81K.
The load was gradually increased from the JIS maximum load in m/hr, and evaluation was made based on the distance traveled until failure occurred. The values are expressed as an index with the value of the comparative tire ■ being 100. The larger this value is, the better the belt durability is.

1-hour standing and failure: The test tire was attached to the drive wheels of a large vehicle, and after driving for 15,000 km on a course with frequent braking and driving, evaluation was made based on the number of cracks that occurred from thin cuts. It is expressed as an index with the value of Comparative Tire 1 as 100. The larger this number is, the better the crank resistance is.

The following four types of tires were created, each having a different tread pattern, total block pinch number ratio, block area ratio per pitch, number of thin cuts, and sub-groove width. The specifications of the above tires are summarized in the table.

Ori 1: A tire having the tread pattern shown in Fig. 1 that satisfies the total number of pitches of blocks specified in the present invention, the area ratio of blocks per pitch, the number of thin cuts, and the width of the minor grooves. .

Nine-way earthwork: The area ratio of blocks per pinch and the groove width of the sub-groove specified in the present invention are satisfied, but the total pitch number ratio of blocks is 1:1, and neither the center part nor the shoulder part A tire having a tread pattern as shown in Fig. 2 in which thin cuts are not provided in the blocks.

MIL Kuni (lIr): A tire having the tread pattern shown in Fig. 3, which is the same as Comparative Tire I except that three thin cuts were also provided in each of the center and shoulder blocks.

Katana "Hita/Koei" -: A tire having a tread pattern shown in FIG. 4, which differs only in that no sub-groove is provided in the shoulder portion of the tire of the present invention.

The sizes, trend surface groove area ratios, tread development widths (TDWs), and main groove depths of these tires were all the same and were as follows.

Tire size: 100OR2014PR Groove area ratio:
35% Trend development width (TDW) 7214mm Main groove depth: 20. Omn The driving performance, braking performance, belt durability, and crack resistance of these tires are shown below. The results are shown in the table.

(Next summer and below, blank spaces) From the table, it can be seen that the tire of the present invention has the same held durability and crack resistance on dry roads as Comparative Tire I, and has significantly superior braking and driving performance on icy and snowy roads. On the other hand, although the comparative tire (3) has excellent braking performance on ice, its crack resistance is greatly reduced and its performance on dry roads is unsatisfactory. In addition, although the comparison tire ■ has the same performance on ice and snow as the inventive tire, the belt durability has significantly decreased.
Practical performance on dry roads is not satisfied.

〔Effect of the invention〕

According to the present invention, in a heavy-duty pneumatic tire for icy and snowy roads having block backs on the tread surface, the groove area ratio of the tread surface is set to 34 to 38χ, and grooves are arranged in the tire circumferential direction in the center part and the shoulder part. By specifying the pitch number and area ratio of the blocks, as well as the number of thin cuts formed in the blocks, we can ensure braking and driving performance on icy and snowy roads, while improving tire performance on dry roads such as belt durability and crank resistance. can be improved.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of the tread pattern of the tire of the present invention, and FIGS. 2, 3, and 4 are plan views showing trend patterns of comparative tires (2), (2), and (2), respectively. 1... Main groove, 2... Minor groove, 3... Block, 4...
・Thin incision.

Claims (1)

[Claims] It has a tread pattern in which blocks partitioned by three main grooves arranged in the tire circumferential direction on the tread surface and a plurality of sub grooves arranged in a direction intersecting the main grooves are arranged in the tire circumferential direction, The groove area ratio of the tread surface is 34% or more.
38%, and the total pitch number ratio of blocks arranged in the center part and blocks arranged in the shoulder part is 2:
1, and the area ratio of the center block and shoulder block per pitch is 1:1.6 to 1:1.
．． 9, the center block has one thin cut in the radial direction approximately at the center, the shoulder block has three thin cuts in the radial direction at approximately equal intervals, and the shoulder block has three thin cuts in the radial direction at approximately equal intervals. A heavy-load pneumatic radial tire for use on icy and snowy roads, in which the width of the sub-groove is at least 80% of the width of the main groove.