JP5093880B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that improves performance on ice and snow while maintaining uneven wear performance.

Various so-called studless tires have been developed that do not have spikes and improve performance on snow and snow.
In this studless tire, in order to improve the performance on ice and snow, it is divided into a number of blocks by a main groove extending zigzag or linearly along the equator of the tire on the tread surface and a lug groove that is a groove in the tire width direction, A pattern in which sipes in the width direction are provided in each block is used.

  For studless tires with such snow and snow performance, especially for heavy duty studless tires such as trucks and buses, the most demanded performance currently relates to the improvement of traction performance on snow and snow. This is an improvement in the traction performance on ice and snow when the vehicle is empty with a small area.

By the way, the reason why the sipe is provided in the block of the conventional studless tire is that the water film generated between the road surface and the tire is eliminated from the past knowledge, and the road surface water film is cut by the edge portion and reliably contacted with the road surface. This is because it is known that it has a function of improving traction performance and driving stability on ice and snow.
Therefore, in order to improve the traction performance on ice and snow, it is conceivable to increase the number of the sipes. However, simply increasing the number of sipes results in subdivision of the blocks, resulting in a decrease in block rigidity and a reduction in tire life. And problems such as increased wear and uneven wear occur.
As described above, it is not easy to achieve a harmony between how to suppress a decrease in block rigidity due to an increase in the number of sipes.

By the way, there are two types of sipe: a double-sided opening type in which both ends of the block are open, and a single-sided opening type in which only one side is open. Therefore, although traction performance can be improved, there is a weak point in uneven wear. On the other hand, the sipe on one side has a small edge effect, but the narrow small land portions (blocks) that are partitioned reinforce each other, so that the rigidity of the entire block is maintained and uneven wear resistance is good. .
Therefore, in order to solve the above-described problem, a pneumatic tire is aimed at improving the starting performance when empty on snow and ice of the studless tire by paying attention to the characteristics of the both-side opening sipe and the one-side opening sipe. It has been proposed (see Patent Document 1).

FIG. 3 shows an example of this conventional pneumatic tire.
On the tread 112 of the pneumatic tire 110, circumferential main grooves 114, 118 and sub-grooves 116, 120 are alternately formed outward from the equator plane CL of the tire. A plurality of lateral grooves 122, 124, 126 are formed between the main grooves 114, 118 and the sub-grooves 116, 118.
In addition, wide lateral grooves 128 and narrow lateral grooves 130 are alternately formed on the outer side in the tire axial direction of the sub-groove 120 at intervals in the tire circumferential direction.

The center block 132 and the second block 136 defined by the main groove, the sub-groove, and the lateral groove are each formed with a pair of both-side opening sipes 134 and 136 extending along the tire width direction. The side block 140 is formed with one-side opening sipes 142 and 144 extending along the tire width direction.
The shoulder block 146 is formed with a one-side opening sipe 148 extending along the tire circumferential direction. The one-side opening sipe 148 has one end opening in the wide lateral groove 128 and the other end terminating in the block.

  As described above, in the conventional studless tire, the center block 132 and the second block 136 are formed with the two side-opening sipes 134 and 138 having long edge components in the axial direction of the tire, while the region on the shoulder portion side of the tread 112 that easily causes uneven wear. That is, the side block 140 and the shoulder block 146 are formed with one-side opening sipes 144 and 148 extending along the tire circumferential direction, and adopt a configuration giving priority to suppressing uneven wear.

However, as described above, as the number of sipes increases, the size of the block itself defined by the sipes decreases, resulting in a problem that the rigidity of the block is reduced, the tire life is shortened, and uneven wear is increased. Come.
Therefore, in the conventional pneumatic tire, if more sipes are formed in the center block or the second block, the rigidity of the block is reduced and the above-mentioned problems occur. Can not.

JP 2002-362114 A

  The object of the present invention is to improve the conventional pneumatic tire, suppress the decrease in block rigidity of the tire by the structure of the block itself, and increase the sipe while suppressing the amount of uneven wear, thereby improving the performance on ice and snow. It is to improve further.

According to the first aspect of the present invention, a plurality of main grooves extending in the circumferential direction in the tread portion, one end of the land portion row sandwiched between the main grooves is opened in one main groove, and the other end is in the land portion row. A plurality of large blocks defined by a first lug groove that terminates, a second lug groove that has one end opened in the other main groove and the other end terminated in the land portion row, and the first lug groove And a small block obtained by dividing the large block in the width direction by a circumferential sipe connecting the second lug groove, and among the large blocks, the small block inside the shoulder block tire has one end. Two widthwise sipes having an opening in the main groove and the other end opened in the circumferential sipe are arranged, and the small block of the large block other than the shoulder block extends in the width direction and extends in the width direction. At least four width-direction sipes communicating with the circumferential sipes are arranged. Is the ratio of the complementary lengths of the maximum width and the left right of the small block of the small block is characterized by a range of 0.15 to 0.3.
The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the main groove includes a land portion row in the center in the width direction and land portion rows adjacent to the left and right of the land portion row in the center in the width direction. The outermost land portion row in the width direction, and the land portion row adjacent to the left and right of the land portion row in the center in the width direction with respect to the width of the land portion row in the center in the width direction, and the outermost land portion in the width direction Each of the column widths is in the range of 80 to 100%.
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the depth of the widthwise sipe is shallower than the depth of the main groove.
According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the depth of the widthwise sipe is in the range of 50 to 70% of the depth of the main groove. And

(Function)
The present invention improves the edge effect of pneumatic tires, particularly heavy duty pneumatic tires, by arranging a larger number of sipes than shoulder blocks in the center block and second block, which are always treads when the vehicle is empty or loaded. It was. At the same time, the overlap distance between adjacent small blocks (also referred to as mutual complementary distance) is set to an appropriate value within a predetermined range, so that deformation of the small blocks can be constrained to reduce block rigidity. The traction performance on ice and snow is improved while suppressing the above.
In the shoulder block that is unlikely to become a tread when empty, the uneven wear performance is maintained at the same level as conventional tires by suppressing the number of sipes installed with priority given to securing rigidity as before.

  According to the present invention, it is possible to improve the running performance on ice and snow, particularly the traction performance when the vehicle is empty, while maintaining the tire life and the durability of the block and maintaining the uneven wear performance.

1 is a development view of a tread portion of a heavy duty pneumatic tire according to an embodiment of the present invention, FIG. 2A is a partially enlarged view of FIG. 1, and FIG. 2B is a partially enlarged view thereof. is there.
As shown in FIGS. 1 and 2A, in the heavy duty pneumatic tire according to the present embodiment, a plurality of, here, four wide main grooves 12 extending in the circumferential direction are arranged in the tread portion 10 of the tire, and the main tire The land portion row 14 (1), (2) sandwiched between the grooves 12 has a first end opened in one main groove 12 and the other end terminated in the land portion row 14 (1), (2). The lug groove 20 (1) is divided by the second lug groove 20 (2), one end of which opens into the other main groove 12 and the other end terminates in the land row 14 (1), (2). A large number of large blocks (center block 30 (1), second block 30 (2)) are formed. The large blocks 30 (1) and 30 (2) are the same in the lateral direction with a sipe 24 extending zigzag in the circumferential direction connecting the first lug groove 20 (1) and the second lug groove 20 (2). It is divided into left and right small blocks 32a and 32b having a width.

  Further, the outer side of the outermost main groove 12 in the width direction is a shoulder land portion 14 (3). The shoulder land portion 14 (3) has a third lug groove 20 (3) having one end opened in the main groove 12 and the other end terminating in the land portion 14 (3), and the shoulder land portion 14 facing inward from the tire outer side. The large block 30 (3) is defined by the wide fourth lug groove 20 (4) extending in the width direction and terminating at (3) and the fifth narrow lug groove 20 (5). The large block 30 (3) is divided into small blocks 32c and 32d inside and outside in the tire width direction by a linear sipe 25 (1) extending in the circumferential direction.

  The first and second lug grooves 20 (1) and 20 (2) and the third lug groove 20 (3) and the fourth and fifth lug grooves 20 (4) and (5) are arranged in the tire circumferential direction. The small blocks 32a32b and 32c, 32d are in a positional relationship shifted from each other by a predetermined distance in the tire circumferential direction.

  The small blocks 32a and 32b of the large block (center block) 30 (1) at the center in the width direction of the tire and the large blocks (second blocks) 30 (2) on the left and right sides thereof extend in the width direction, respectively. In the illustrated example, four sheets in the width direction sipe 26 communicating with the groove 12 and the circumferential direction sipe 24 are formed for each small block.

  In contrast, the small block 32 (c) inside the tire of the shoulder block 30 (3) has two width-direction sipes 26 having one end opened in the main groove 12 and the other end opened in the circumferential sipe 25. In the outer small block 32 (d), a circumferential sipe 25 (one end is opened in the fourth lug groove 20 (4) and the other end is terminated in the block 32 (d). Only 2) is formed. That is, the shoulder block has a configuration in which the suppression of uneven wear is given priority over the edge effect as in the conventional case.

  Since the small blocks 32a and 32b of the center block 30 (1) and the second block 30 (2) of the present embodiment are divided by zigzag sipes 24 extending in the circumferential direction, the tire width direction thereof is seen through. When I try, they overlap each other. That is, as shown in FIG. 2B, each of the small blocks 32a and 32b has a length: W1 (= W−2t) obtained by subtracting a value twice the width t of the sipe 24 from the maximum width W of the zigzag groove of the sipe 24. They overlap in the tire width direction (here, the overlapping length is called the mutual complementary distance).

Since the small blocks 32a and 32b overlap each other in the width direction in this manner, the areas where the small blocks 32a and 32b come into contact with each other when the small blocks 32a and 32b are deformed under a load are overlapped. When one small block is deformed, the rigidity can be supplemented by supporting the other small block and suppressing the deformation.
This rigidity complementation increases the rigidity of the center block 30 (1) and the second block 30 (2), which are large blocks, as a result, and as a result, the center block 30 (1) and the second block 30 (2) are more than conventional. It is possible to form the sipe 26 having many openings on both sides.
By adopting this configuration, while maintaining the rigidity of the block, the edge effect is improved, and the running performance when running on an icy and snowy surface, particularly the traction performance when empty can be greatly improved.

Here, the ratio (complementation rate) of the maximum width W1 of the small block 32a or 32b and the length (mutual complementary length) W2 where the small blocks 32a or 32b on the left and right in the width direction overlap each other: W1 / W2 A range of 0.15 to 0.3 is preferable.
The reason is that if W1 / W2 is less than 0.15, the contact area in the deformation of the small blocks 32a and 32b becomes small, so the action of the small blocks restraining the deformation is not sufficient, and the deformation becomes large. There are problems of shortening the service life and increasing the amount of uneven wear. Also, if W1 / W2 exceeds 0.3, the rigidity of the small block in, for example, the shaded area in FIG. 1 is lowered, causing problems in uneven wear and block durability.

In the present embodiment, there are four circumferential grooves 12, each of which has a (center) land portion row 14 (1) in the center in the width direction and a (second) land portion row 14 adjacent to the left and right of the center land portion row. (2) and the outermost (shoulder) land portion row 14 (3) in the width direction are partitioned.
In the present embodiment, with respect to the width of the land portion row at the center in the width direction, the width of the land portion row adjacent to the left and right of the land portion row at the center in the width direction and the width of the outermost land portion row in the width direction are each 80 to It is in the range of 100%.
This is because the land section row in the center of the tire width direction is always in contact with the ground regardless of whether it is empty or loaded, and is the part that has the greatest impact on the performance on ice and snow. By setting the width of the land portion row adjacent to the width of the land portion row and the outermost land portion row in the width direction to a width that does not cause uneven wear, the ice and snow surface is maintained while maintaining rigidity. This is to enhance the traction effect on the running.

In this embodiment, the depth of the width direction sipe 26 is shallower than the depth of the main groove 12, and the depth of the width direction sipe 26 is 50 to 70 of the depth of the main groove 12. % Is preferable.
This is because if the sipe 26 is deeper than the depth of the main groove 12, the block rigidity is insufficient, and if it is too shallow, the sipe may disappear after the middle stage of wear. This is because the range in which the block rigidity can be achieved is taken into consideration.

In the pneumatic tire according to the present embodiment, the center block 30 (1) serving as the tread surface of the tire when empty and the four side-opening sipe 26 of the second block 30 (2) are provided. The number is not limited to four, and may be five, for example, as long as a desired block rigidity is obtained in relation to the mutual complementary length between the small blocks 32a and 32b. In short, it is only necessary to compensate for the decrease in the block rigidity due to the provision of the width-direction sipes by the interaction between the small blocks 32a and 32b.
Moreover, although the said width direction sipe 26 is illustrated as a linear thing, it is not restricted to this, The bending blade of 1 bending or more may be sufficient.

  As described above, the pneumatic tire according to the present embodiment increases the edge of the center block and the second block, which are the treads when the vehicle is empty, to improve the traction performance on ice and snow, and to reduce the rigidity accompanying it. The rigidity is complemented based on the mutual complementary length of the small blocks, ensuring the same rigidity as the conventional product, and the number of sipes in the width direction of the shoulder portion is set to only two in this embodiment. Thus, the uneven wear performance in the shoulder block can be maintained.

In order to confirm the block rigidity, uneven wear performance, and traction performance on an ice / snow surface of the studless tire which is an embodiment of the present invention, a test was performed in comparison with a conventional product and a comparative product.
<Test method>
Confirmation of uneven wear was carried out by attaching the main wheel to a 2-D / 4 loader with 100% load, and confirming the amount of uneven wear when the rim size was 7.50 and the air pressure was 900 kPa and the wear rate was 50%. The block stiffness was calculated from the block dimension of the CL block. In the actual vehicle test, the conditions shown in the paragraph “0028” were performed under the conditions shown in Tables 3 and 4.

In the test, all the tires used for comparison had four circumferential grooves, and consisted of a center block in the center in the tire width direction, second blocks on both left and right sides, and shoulder blocks on both left and right sides. The block rigidity was compared with the amount of uneven wear (the amount of uneven wear when the wear rate was 50%).
The table shows the results of these tests (actual tests), Table 1 summarizes the comparison results of rigidity, and Table 2 summarizes the amount of uneven wear.
Here, the test tire is a radial ply tire for trucks and buses having a tire size of 11R22.5 16PR defined by JATMA YEAR BOOK (2006 Japan Automobile Tire Association Standard).
In the actual vehicle test, the vehicle is a truck with 2-D (front wheel is 2 wheels and 1 axle, rear wheel is 1 axle of drive double wheels) and chassis (rear axle is 2 axles of 2 wheels), rim size: 7 .50, air pressure: 900 kPa. The place was on the test course.

That is,
1. Conventional product: A
As a conventional product, the complementary distance ratio between small blocks is 0.12, and the number of sipes is 2 for the central block in the width direction, 2 for blocks adjacent to the left and right, and 2 for the shoulder block The amount of uneven wear when the block rigidity and the wear rate were 50% was set to 100 (index).
2. Comparative product: B
As a comparative product, the complementary distance ratio between small blocks is 0.12 as in the conventional product. However, the number of sipes is 4 at the center block in the width direction, 4 at the right and left adjacent blocks, and 2 at the shoulder block. I saw the block rigidity of the thing. As a result, as shown in Table 1, the block rigidity was 90, which was 10% lower than the conventional product. As a result, the amount of uneven wear when the wear rate was 50% increased by 105% to 5%.
3. Product: C
As an implemented product, the complementary distance ratio between small blocks is 0.18, and the number of sipes is 4 in the central block in the width direction, 4 in the block adjacent to the right and left, and 2 in the shoulder block, as in the comparative product I saw the block rigidity. As a result, the block rigidity was 101, which was slightly higher than the conventional product, but increased. Further, the amount of uneven wear when the wear rate was 50% was not different from the conventional product.

Based on the above results, the snow and snow performance of the implemented product is greatly improved by using four sipe on the tire width direction center block and the left and right second blocks with high contact pressure, and two sipe on the shoulder block even when empty. In addition, as is clear from the comparison between the conventional product and the comparative product, the rigidity of the small block decreases, but by increasing the complementary distance, the rigidity of the small blocks is complemented. It can be seen that the same rigidity is maintained.
In addition, in order to increase the edge component, the amount of uneven wear was increased to 4 for the center block in the center in the tire width direction and the second block on the left and right sides of the sipe, compared to 2 for the conventional product. As for the shoulder block, there is a concern about the shoulder drop wear of the shoulder portion. As a result, the uneven wear amount maintained the same performance as before.

Next, the results of the traction test on ice will be described.
The engine speed was kept constant and the test was performed on the ice surface.
When the traction on ice of the conventional product A was set to 100, the comparative product B was 120 and the implementation product C was 125.
That is, the traction on ice was improved by 25% over the conventional product.

In the traction test on snow, the engine speed was fixed and the test was performed on the road surface of snow.
As a result, when the traction on ice of the conventional product A was 100, the comparative product B was 110, and the implementation product C was 115.
That is, the traction on ice was improved by 15% compared to the conventional product.

  As described above, in the embodiment product C of the present invention, the number of sipe in the width direction can be increased without lowering the rigidity of the tire as compared with the conventional tire A, and as a result, particularly on an icy and snowy surface when the vehicle is empty. It was proved that the traction improved.

It is a figure which shows the tread pattern of the pneumatic tire of this invention. FIG. 2A is an enlarged view of a part of the tire shown in FIG. FIG. 2B is a diagram for explaining the mutual complementary distance of small blocks. It is a figure which shows the tread pattern of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Tread part, 12 ... Main groove, 14 (1) -14 (3) ... Land part row | line | column, 20 (1) -20 (5) ... 1st-5th lug groove 24 ... Circumferential sipe, 26 ... Width sipe, 30 (1) ... Center block, 30 (2) ... Second block, 30 (3) ... Shoulder block, 32a to 32d ... small blocks.

Claims (4)

A plurality of main grooves extending in the circumferential direction in the tread portion, and a first lug groove having one end opened in one main groove in the land portion row sandwiched between the main grooves and the other end terminating in the land portion row A plurality of large blocks defined by a second lug groove having one end opened in the other main groove and the other end terminated in the land portion row, the first lug groove and the second lug groove In a pneumatic tire having a small block obtained by dividing the large block in the width direction by a circumferential sipe connecting
Among the large blocks, the small block inside the tire of the shoulder block is provided with two widthwise sipes having one end opened in the main groove and the other end opened in the circumferential sipe,
Wherein said small blocks of a large block other than the shoulder block is at least four widthwise sipes are disposed in communication with the circumferential sipe and the main groove extending in the width direction, the maximum width and the left right of the small block A pneumatic tire characterized in that the ratio of the mutually complementary lengths of the small blocks is in the range of 0.15 to 0.3. In the pneumatic tire according to claim 1,
The main groove defines a land portion row in the center in the width direction, a land portion row adjacent to the left and right of the land portion row in the center in the width direction, and a land portion row on the outermost side in the width direction,
The width of the land portion row adjacent to the left and right of the land portion row at the center in the width direction and the width of the land portion row at the outermost side in the width direction are each in the range of 80 to 100% with respect to the width of the land portion row at the center in the width direction. A pneumatic tire characterized by that. In the pneumatic tire according to claim 1 or 2,
The pneumatic tire according to claim 1, wherein a depth of the sipe in the width direction is shallower than a depth of the main groove. The pneumatic tire according to any one of claims 1 to 3, wherein a depth of the width direction sipe is in a range of 50 to 70% of a depth of the main groove.

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