JPH09216504A - Pneumatic tire for snow and ice road - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the performance of a pneumatic tire on ice remarkably while ensuring the performance on snow same as an usual tire for a snow and ice road. SOLUTION: A rib 2 divided to right/left two main grooves 1a, 1b extended in a tire periphery direction is arranged in at least the central area of a tread surface and many sips 4 extending to a tire width direction are arranged on the rib 2 and also subgrooves 3a extending upto the rib 2 central area from a right side main groove 1a and the sub-grooves 3b extending upto the rib 2 central area from a left side main groove 1b are arranged alternately in a tire periphery direction and the ratio w/W for the tire grounded width W of the rib width w is made to 0.2-0.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a snow / ice road pneumatic tire, and more particularly to a snow / ice road pneumatic tire having improved on-ice performance without deteriorating snow performance.

[0002]

2. Description of the Related Art Conventionally, pneumatic tires for snow and ice roads use a rubber compound having a low hardness at low temperatures and an excellent adhesive friction force as a cap tread rubber, and a tread pattern as shown in FIG. On the ice by forming a large number of blocks 25 by the main grooves 21 in the direction of the tire and the auxiliary grooves 23 in the direction of the tire width and arranging a large number of sipes 24 in the blocks 25 in the direction of the tire width to form a block pattern having a large edge effect. It is common to improve performance.

[0003]

However, in the block pattern as shown in FIG. 2, when the hardness of the cap tread rubber is low and the number of sipes is too large, the rigidity of the block becomes low, and the block becomes liable to travel on ice. Since it falls down and cannot be grounded sufficiently, there is a drawback that the performance on ice is rather deteriorated.

As a countermeasure against such a defect, Japanese Patent Laid-Open No. 4-8
In Japanese Patent No. 5017, a rib 26 extending in the tire circumferential direction is provided instead of the block as shown in FIG.
There is proposed a snow / ice road tire in which a large number of sipes 24 are provided in No. 6 to ensure tread rigidity. However, ribs must be wide ribs because rigidity cannot be increased with narrow ribs. Wide ribs are advantageous for improving on-ice performance, but because there is no lug groove like block patterns, the snow pillar effect However, there is a drawback that the performance on snow is deteriorated. An object of the present invention is to provide a pneumatic tire for snow and ice roads, which has substantially the same performance on snow as that of conventional tires for snow and ice roads, while significantly improving the performance on ice.

[0005]

SUMMARY OF THE INVENTION According to the present invention for solving the above-mentioned problems, a rib divided into two left and right main grooves extending in the tire circumferential direction is arranged at least in the central region of the tread surface, and the rib has a tire width. A plurality of sipes extending in the direction are arranged, and a sub-groove extending from the right main groove to the rib central area and a sub-groove extending from the left main groove to the rib central area are alternately arranged in the tire circumferential direction. The ratio w / W of the width w to the tire ground contact width W is set to 0.2 to 0.5.

As described above, the relatively wide ribs are arranged in the central area of the tread surface, and a large number of sipes extending in the tire width direction are arranged on the ribs, so that the tread rigidity is increased and the edge effect is increased. The performance can be greatly improved. In addition, the rib has a sub-groove extending from the main groove on the side to the center of the rib width, so the snow column effect of the sub-groove prevents the snow performance from deteriorating and ensures the same snow performance as the conventional snow and ice road tires. can do.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on an embodiment shown in the drawings. FIG. 1 is a tread pattern of a pneumatic tire for snow and ice roads showing an embodiment of the present invention, in which two left and right main grooves 1a and 1b are relatively thick in the central area of the tread surface, and left and right are relatively thin in the shoulder area. Two main grooves 11a and 11b are provided in the tire circumferential direction.

The two main grooves 1a and 1b in the central region are formed in a zigzag shape, and a rib 2 is formed between them.
On the rib 2, sub-grooves 3a extending from the right main groove 1a to the rib central region and sub-grooves 3b extending from the left main groove 1b to the rib central region are alternately arranged in the tire circumferential direction.
In addition, the sub-grooves 3a and 3b are provided one by one in every zigzag pitch of the main grooves 1a and 1b, and are arranged on the left and right by a half pitch in the tire circumferential direction. Due to such arrangement of the sub-grooves 3a and 3b, the rib 2 in the central portion has a shape that continuously meanders in a large zigzag shape on the tire circumference.

The rib 2 is provided with a large number of sipes 4 extending in the tire width direction. Each of these sipes 4 is provided so that one end thereof is open to one of the main grooves 1a and 1b or the sub-grooves 3a and 3b, and the other end is inside the rib 2. Blocks 5 are divided by a large number of lateral grooves 6 between the main grooves 1a and 1b in the central area and the main grooves 11a and 11b in the shoulder area, and between the main grooves 11a and 11b and the shoulder ends. Are formed, and two block rows are formed in each shoulder region. Each block 5 is provided with a large number of sipes 4 in the tire width direction similarly to the central rib 2.

In the above tread structure, the tread rubber has a JIS A hardness of 40 to 60 at 0 ° C.
Preferably 44 to 54, more preferably 48 to 52 rubber compounds are used. If the JIS A hardness (0 ° C.) is less than 40, the tire durability will decrease, and 6
If it exceeds 0, the rigidity of the tread is too high and the performance on ice is deteriorated.

In the present invention, the main grooves 1a, 1b for partitioning the rib 2 in the central region of the tread surface may have a zigzag shape as in the illustrated example or a straight shape. However, it is preferable that the zigzag shape is advantageous in enhancing the edge effect and the snow column effect. Also, rib 2 in the central area
The rib width w of the tire is set to be relatively wide, and the tire ground contact width W
The ratio w / W is set in the range of 0.2 to 0.5. It is preferably 0.3 to 0.4. When it is less than 0.2, the rigidity of the rib cannot be sufficiently obtained, and the improvement of the performance on ice is small. On the other hand, if it exceeds 0.5, the rigidity of the tread is excessively increased and the performance on snow is deteriorated.

Here, the rib width w is defined as the average value of the maximum width and the minimum width when it changes in the longitudinal direction due to the zigzag of the main grooves 1a, 1b or unevenness. Further, the tire ground contact width W is a value obtained when the air pressure specified by JATMA is filled and a design normal load is applied. In the present invention, the sub-grooves 3a, 3 provided on the rib 2 are provided.
In b, one end must be open to either one of the main grooves 1a and 1b, and the other end must be in the central region of the rib 2, but the length measured in the tire width direction Is preferably in the range of 40 to 60% with respect to the rib width w.

Further, at least 75% of the sipes 4 provided on the ribs 2 have a sipe length s.
Is 0.75 to 0.9 as a ratio s / w to the rib width w.
5 is preferable, and more preferably 0.8 to
It is good to set it to 0.9. If it is less than 0.75, the edge amount is small, so that the improvement in on-ice performance cannot be obtained.
If it exceeds the above range, the cut is too large and the durability is reduced, and cracks may occur from the sipe.

[0014]

【Example】

Example 1 The tire size is 185 / 65R14, the tread rubber hardness is JIS A hardness 50, the tread pattern is FIG. 1, and the sipe length s of the central region rib is s / w = 0.90. Five kinds of tires (invention tires 1 to 3 and comparative tires 1 and 2) in which the value of / W was changed as shown in Table 1 were manufactured.

The tire size and the hardness of the tread rubber are the same as above, but the conventional tire 1 having the tread pattern in the block pattern of FIG. 2 and the conventional tire 1 having the tread pattern of FIG.
A conventional tire 2 including a book rib and four block rows was manufactured. Similarly, the tire size and tread rubber hardness are the same as above, and the tread pattern is w / w as shown in FIG.
A comparative tire 3 having W of 0.3, a central rib and four block rows was manufactured.

The above-mentioned eight types of snow and ice road tires were evaluated for their on-ice performance and on-snow performance by the following test methods, and the evaluation results shown in Table 1 were obtained. As is clear from Table 1, all of the tires 1 to 3 of the present invention have substantially improved ice performance while ensuring the same snow performance as the conventional tire 1. Moreover, w / W is 0.
It can be seen that the comparative tire 1 smaller than 2 does not sufficiently improve the on-ice performance, and the comparative tire 2 larger than 0.5 has a large decrease in the on-snow performance. Further, it can be seen that the comparative tire 3 having no sub-groove has excellent on-ice performance, but inferior on-snow performance.

Performance test on ice Rim 14 × 5 1 / 2J, internal pressure 200 kPa, displacement 1
It was mounted on an 800 cc FF passenger car and tested as follows. (Breaking property on ice) A braking distance was measured when lock braking was performed from a running speed of 40 km / h on an ice road test course where the ice temperature and the air temperature were -3 ° C to -6 ° C. The measurement result was evaluated by the reciprocal number, and the result was shown as an index with the conventional tire 1 being 100. The larger this index, the better the braking performance on ice. Here, an index of 108 or more was evaluated as effective.

(Ice climbing property) Ice temperature and temperature are -3 ° C to -6
Initial speed of 20km / in ice course climbing test course at ℃
Acceleration was performed from h and the time of a certain section was measured. The reciprocal of the measurement result was evaluated, and the result was expressed by an index with the conventional tire 1 being 100. The larger this index, the better the performance on the ice. Here, an index of 108 or more was evaluated as effective.

Performance test on snow Rim 14 × 5 1 / 2J, internal pressure 200 kPa, displacement 1
It was mounted on an 800 cc FF passenger car and tested as follows. (Breaking property on snow) A braking distance was measured when lock braking was performed from a running speed of 40 km / h on a snowy road test course where the snow temperature and the air temperature were -1 ° C to -5 ° C. The measurement result was evaluated by the reciprocal number, and the result was shown as an index with the conventional tire 1 being 100. The larger this index, the better the snow braking performance. Here, the index of 95 is set as an allowable lower limit.

(Slope climbing on snow) Snow temperature and temperature are -1 ° C to -5
Initial speed of 20km / in a snowy road test course at ℃
Acceleration was performed from h and the time of a certain section was measured. The reciprocal of the measurement result was evaluated, and the result was expressed by an index with the conventional tire 1 being 100. The larger this index, the better the snow climbing performance. Here, the index of 95 is set as an allowable lower limit.

[0021]

Example 2 A tire size of 185 / 65R14, a tread rubber hardness of JIS A hardness of 50, a tread pattern of FIG. 1, and a w / W of 0.3 are common, and a sipe provided on a central rib is used. Tires 4 to 8 of the present invention were manufactured in which the ratio s / w of the length s to the rib width w was varied as shown in Table 2.

The durability of each of these five types of tires was evaluated by the following test methods, and the results shown in Table 2 were obtained. As is clear from Table 2, when the sipe of the central rib is too long, cracks occur in the sipe and the durability of the tread is reduced. (Durability test) Rim 14 x 5 1/2 J, internal pressure 200 kPa
As a result, after mounting on an FF passenger car with a displacement of 1800 cc and traveling 30,000 km in an urban area, the occurrence of a failure from a sipe was visually confirmed.

[0024]

Example 3 Tire size is 185 / 65R14, tread pattern is FIG. 1, w / W ratio in the central rib is 0.3, s / w
The common point is that the tread rubber is 0.8.
Nine types of snow and ice road tires having A hardness (0 ° C.) changed in the range of 36 to 62 were manufactured.

The results of the on-ice braking test conducted on these tires by the above-described test method are shown in FIG. However, the evaluation was indicated by an index with a tire having JIS A hardness of 51 as 100. In addition, JIS D4
The durability performance test of 230 was carried out, and the result of judging acceptable (◯) and unacceptable (×) depending on the traveling condition of the required conditions is shown in Table 3 below.
It was as follows.

[0027]

As is clear from FIG. 5 and Table 3, when the JIS A hardness of the tread rubber is low, the braking performance on ice is improved, but the durability is reduced. Also, JIS
It can be seen that as the A hardness increases, the braking performance on ice decreases. In particular, it can be seen that by setting the range of 40 to 60, the braking performance on ice and the durability are balanced.

[0029]

According to the pneumatic tire for snow and ice roads of the present invention, a large number of sipes extending in the tire width direction are arranged on the rib formed by two main grooves provided in the circumferential direction of the tread surface, Sub-grooves extending from the main groove to the central area are alternately arranged in the tire circumferential direction, and the rib width is set to a specific range with respect to the tire ground contact width, so that snow performance equivalent to that of conventional pneumatic tires for snow and ice roads is secured. On the other hand, the performance on ice can be greatly improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a tread pattern of a tire of the present invention.

FIG. 2 is a plan view showing a tread pattern of a conventional tire.

FIG. 3 is a plan view showing another example of the tread pattern of the conventional tire.

FIG. 4 is a plan view illustrating a tread pattern of a comparative tire.

FIG. 5 is a graph showing the relationship between the hardness of tread rubber and the performance on ice.

[Explanation of symbols]

 1a, 1b Main groove 2 Ribs 3a, 3b Sub groove 4 Sipe 5 Block row w Rib width W Tire ground width s Sipe length

Claims (5)

[Claims] 1. A rib divided into two left and right main grooves extending in the tire circumferential direction is arranged at least in the central region of the tread surface, and a large number of sipes extending in the tire width direction are arranged on the rib, and at the right side Sub-grooves extending from the main groove to the rib central region and sub-grooves extending from the left main groove to the rib central region are alternately arranged in the tire circumferential direction, and a ratio w / W of the rib width w to the tire ground contact width W is set. Pneumatic tire for snow and ice roads made 0.2-0.5. 2. The rib is formed such that the sipe is opened to either one of two main grooves or sub grooves on the left and right of the rib, and at least 75% of the sipe has the sipe length s. The ratio s / w to the width w is 0.75 to 0.
95. The pneumatic tire for snow and ice roads according to claim 1. 3. The pneumatic tire for snow and ice roads according to claim 1, wherein the two left and right main grooves are formed in a zigzag shape in the tire circumferential direction. 4. The pneumatic tire for snow and ice roads according to any one of claims 1 to 3, wherein a row of blocks made up of sipes is arranged in the shoulder area of the tread surface. 5. The pneumatic tire for snow and ice roads according to claim 1, wherein the tread rubber has a JIS A hardness at 0 ° C. of 40 to 60.