JP5778510B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a block formed on a tread surface of a tire is provided with one or more sipes extending in a tread width direction and a narrow groove with which a facing groove wall contacts when the road surface is not grounded. In particular, the present invention proposes a technique for further improving the on-ice frictional characteristics of a tire without greatly reducing the block rigidity.

  In a pneumatic tire formed by dividing a plurality of block rows into a tread tread surface by a plurality of circumferential grooves continuous in the tread circumferential direction and a plurality of lateral grooves intersecting the circumferential grooves and extending in the tread width direction, A technique for improving friction characteristics on ice by providing a plurality of sipes in a block is known. According to this technology, the traction performance on ice can be achieved by the edge effect of cutting the water film on ice with a sipe edge to scratch the ice surface and the drainage effect of sucking and draining the cut water film into the sipe gap. It is assumed that the brake performance can be improved. Here, it is generally said that the edge effect can be enhanced as the edge pressure and edge length at the corners (edges) of the small blocks partitioned by sipes increase.

By the way, in order to further enhance the edge effect and drainage effect, if the number of sipes per block is increased, the block rigidity decreases and the block collapses and the contact area with the road surface decreases. On the contrary, the friction characteristics on ice may be deteriorated.
As a conventional technique for suppressing such a decrease in the contact area, for example, as described in Patent Document 1, a plurality of sipes are extended in a zigzag shape on the surface of the block, and the zigzag shape is also formed on the protruding base side of the block. A tire is known in which the block portions defined by these sipes are supported by each other so as to suppress the collapse of the blocks.

JP 2006-123636 A

However, in the tire described in Patent Document 1, it is difficult to further enhance the edge effect because the sipe edge pressure of the block part is reduced by suppressing the collapse deformation of the block part. .
For this reason, there has been a strong demand for the appearance of a new tire that further suppresses the falling deformation of the block portion and further enhances the edge effect to further improve the friction characteristics on ice.

  An object of the present invention is to provide a novel pneumatic tire that can further enhance the edge effect of the block formed on the tread surface and further improve the friction characteristics on ice.

The present invention divides a plurality of block rows on a tread tread surface by a plurality of circumferential grooves continuous in the tread circumferential direction and a plurality of horizontal grooves intersecting the circumferential grooves and extending in the tread width direction. In the pneumatic tire provided with one or more sipes extending in the tread width direction,
Each block is provided with a plurality of narrow grooves extending in a direction intersecting with the direction in which the sipe extends, and in which the groove walls facing each other when the road surface is not grounded are in contact with each other ,
The depth of the narrow groove is 5% to 20% with respect to the maximum protruding height of the block from the circumferential groove bottom or the lateral groove bottom,
An extending angle of the small groove is made in the range of 30 ° to 60 ° with respect to the tread width direction.

Here, “sipe” is a groove having an opening width wider than the narrow groove formed in the block, for example, about 0.2 to 2.0 mm, and while being in contact with the road surface. At least a part of the facing groove walls is in contact.
In addition, “the groove walls that are opposed to each other when the road surface is not in contact with each other” is a narrow groove. When the narrow groove is not in contact with the road surface, the entire surface of the opposed groove walls is in contact with the road surface. When grounding, some of the facing groove walls may slightly open.

  And it is preferable to make the said sipe extend in a zigzag shape also in the depth direction while extending in the tread tread surface.

Each of the plurality of blocks defined on the tread surface is provided with one or more sipes extending in the tread width direction, extending in a direction intersecting with the extending direction of the sipes, and opposing groove walls are By providing a plurality of narrow grooves that are in contact with each other when the road surface is not grounded, an edge formed by the narrow grooves can be added to the block while ensuring a sufficient ground contact area with the road surface. The edge effect can be further enhanced.
And since these fine grooves can also function as a fine drainage means for the water film on ice, the drainage effect can be further enhanced, and the on-ice friction characteristics can be further improved.

  In this tire, when the depth of the narrow groove is 5% to 20% with respect to the maximum protruding height from the circumferential groove bottom or the lateral groove bottom of the block, the depth of the narrow groove is optimized and the block The edge effect can be more fully exhibited while suppressing the falling deformation.

  If the extension angle of the narrow groove with respect to the tread width direction is too small, the block is liable to collapse, and if the extension angle is too large, there is a concern that it may be difficult to exert the edge effect during braking and driving. The extending angle of the groove is preferably in the range of 30 ° to 60 °. Within this range, the above-mentioned concern can be removed and the frictional properties on ice can be further improved.

  When the sipe is extended in a zigzag shape in the tread tread, and the zipe is extended also in the depth direction, the collapsed deformation is sufficiently suppressed by the support of the block portion divided by the sipe. Therefore, the improvement of the on-ice friction characteristic due to the provision of the narrow groove can be made more reliable.

1 is a partially developed plan view of a tread surface and an enlarged plan view of a block, schematically showing an embodiment of a pneumatic tire according to the present invention. It is an expanded sectional view which follows the AA line of the block shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings.
In addition, since the internal reinforcement structure of a tire is the same as that of a general pneumatic tire, illustration is abbreviate | omitted here.

In the tread surface 1 shown in FIG. 1, a plurality of circumferential grooves 2 continuously extending in an annular shape in the tread circumferential direction are arranged on the tire equator line E and at positions symmetrical to the equator line E. For example, a plurality of horizontal grooves 3 that extend linearly in the tread width direction and intersect with the circumferential grooves 2 are provided, and a plurality of block rows 4 are formed by these grooves 2 and 3. Is formed.
By the way, each block row 4 shown in the figure is formed by arranging a plurality of blocks 4a having a rectangular planar outline in the tread circumferential direction at a required pitch. Here, the block row 4 can also include a shoulder block row formed by extending the lateral grooves 3 to a shoulder region located further outward than the outermost circumferential groove 2 in the tread width direction.

Each block 4a includes one or more sipes 5 extending in the tread width direction. Here, the sipe “extending in the tread width direction” means that the extending component in the tread width direction of the sipe is longer than the extending component in the tread circumferential direction, and within the tread surface 1 of the sipe. The extending form of the sipe can be various forms such as a straight line, a curved form, a zigzag form, or a combination thereof, and the extending form of the sipe in the depth direction is a straight line. In addition to being extended, it can have various forms such as a curved shape, a zigzag shape, or a combination thereof.
As shown in the figure, each sipe 5 extends linearly in the tread width direction and opens in the adjacent circumferential groove 2 in both outer regions in the tread width direction of the block 4a, while in the central region of the block 4a, It extends in a zigzag shape with a constant amplitude in the tread circumferential direction. In the depth direction of the sipe 5, as shown in FIG. 2, the sipe 5 may extend in a zigzag shape so as to have an amplitude in the tread circumferential direction.
Each block 4 a is divided into a plurality of block portions 4 a ₁ by a sipe 5.

Further, the block 4 a includes a plurality of narrow grooves 6 extending in a direction intersecting with the extending direction of the sipe 5.
Here, the narrow groove 6 further divides the block portion 4a ₁ and has a groove width (slot) narrower than the sipe 5, and forms a plurality of edges 4b in the block 4a together with the sipe 5, while facing each other. The groove walls to be brought into contact with each other when the road surface is not grounded.
The narrow groove 6 shown in FIG. 1 is inclined linearly at an angle a with respect to the tread width direction, and the narrow groove 6 has a curved shape, a zigzag shape, or a combination thereof. It can also be extended in various forms.

For example, as shown in FIG. 2, the tire configured as described above has not only a sipe edge 4b but also a narrow groove on the ice surface when the braking force is exerted in the direction indicated by the arrow on the ice surface. Since the edge 4b can also act, the edge effect can be greatly enhanced.
On the other hand, even if the number of edges is increased by the narrow grooves 6, since the narrow grooves 6 are in contact with each other when the road surface is not grounded as described above, the block rigidity is greatly reduced. There is nothing. Moreover, since the water film on ice can be sucked not only into the sipe 5 but also into the narrow groove 6, the drainage effect can be further enhanced, and the on-ice friction characteristics can be further improved.

Here , the depth c of the narrow groove 6 is in the range of 5% to 20% with respect to the maximum projecting height b from the bottom surface of the circumferential groove 2 or the lateral groove 3 of the block 4a shown in FIG. .
When the depth c of the fine groove 6 is too shallow, narrow grooves 6, it is difficult to sufficiently exhibit the edge effect and drainage effect and, when the depth c of the narrow groove 6 becomes too deep, leaning in block 4a Since deformation is likely to occur, the above range ensures the further improvement of the on-ice friction characteristics.

Incidentally, extending the angle a of the narrow grooves 6 shall be the range of 30 ° to 60 ° with respect to the tread width direction.
That is, if the extension angle a is too small, the block 4a is likely to fall down, and if the extension angle a is too large, the edge effect may not be sufficiently exhibited. In the case of the range, it is possible to remove these inconveniences and further improve the friction characteristics on ice.

Further, when the sipe 5 is extended in a zigzag manner in the tread tread surface 1 as in the illustrated example, and the zipe 5 is also extended in the depth direction, the opposing block portions 4a ₁ support each other. Thus, the falling deformation of the block 4a is sufficiently suppressed, so that the improvement of the on-ice friction characteristic by providing the narrow groove 6 can be made more reliable.

  By the way, as shown in FIG. 1, the direction in which the narrow groove 6 extends is preferably the direction from the outer side in the tread width direction toward the tire equator line E along the tire rotation direction. That is, the narrow groove 6 is inclined in the opposite direction with a half width of the tread from the tire equator line E as a boundary. According to this, since the water film on ice can be sucked into the narrow groove 6 and the water can be drained outward in the tire width direction, the drainage effect of the narrow groove 6 can be further enhanced.

  Moreover, the sipe 5 may be inclined and extended in an angle range of 0 ° to 30 ° with respect to the tread width direction. Here, “inclination in an angle range of 0 ° to 30 °” means the angle of the straight line connecting the outer end portion and the inner end portion of the sipe in the tire width direction with respect to the tread width direction. The sipe may be inclined while extending in a shape.

On the other hand, in the illustrated example, the planar contour of the block 4a is rectangular, but the lateral groove 3 is inclined in the range of 0 ° to 30 ° with respect to the tread width direction, so that the block is parallelogram-shaped planar contour. In the case where the block is provided, when the block contacts the road surface, coupling deformation occurs, so that the edge effect can be further exhibited.
In addition, when the inclination angle of the lateral groove 3 exceeds 30 ° with respect to the tread width direction, the collapse of the block becomes too large and the ground contact area is reduced. To secure.

The circumferential pitch length of the sipes 5 adjacent to each other is preferably in the range of 2.4 to 5.0 mm, and the circumferential pitch length of the narrow grooves 6 adjacent to each other is also 2.4. It is preferable to set it as the range of -5.0 mm.
In other words, when the circumferential pitch length of the sipe 5 and the narrow groove 6 is smaller than 2.4 mm, the collapsed deformation of the block becomes too large to reduce the ground contact area, and they are larger than 5.0 mm. This is because a sufficient improvement in the edge effect cannot be expected.

Hereinafter, each of the conforming tire according to the present invention, which is the basic structure shown in FIGS. 1 and 2, each having a size of 195 / 65R15, and the conventional tire that is the same as the conforming tire except that the narrow groove 6 is not provided. As a matter of course, these tires were incorporated into a standard rim, filled with an internal pressure of 200 kPa and mounted on a passenger car, and a braking test on ice was performed. The results are shown in Table 1 together with the specifications of each tire. The maximum protruding height b of the block from the circumferential groove bottom or the lateral groove bottom was 10.0 mm.
Here, the braking test was performed by measuring the braking distance from the initial speed of 40 km / h until full braking was applied and calculating the average deceleration from the initial speed and the braking distance.
The results shown in Table 1 are values in which the average deceleration is expressed as an index using the conventional tire as a control. The larger the index value, the higher the braking performance and the better the friction characteristics on ice.

  As a result, it has been clarified that the tires according to the present invention provided with narrow grooves exhibit braking performance equal to or higher than that of conventional tires and have excellent friction characteristics on ice. The depth of the narrow groove is 5% to 20% with respect to the maximum protruding height of the block from the circumferential groove bottom or the lateral groove bottom, and the extending angle of the narrow groove is 30 ° to the tread width direction. Tires with a 60 ° range gave particularly good results.

1 tread surface 2 circumferential groove 3 horizontal groove 4 block row 4a block 4b edge 5 sipe 6 narrow groove E tire equator line

Claims (2)

A plurality of block rows are defined on the tread surface by a plurality of circumferential grooves continuous in the tread circumferential direction and a plurality of horizontal grooves that intersect the circumferential grooves and extend in the tread width direction, and each block has a tread width direction. A pneumatic tire provided with one or more sipes extending to
Each block is provided with a plurality of narrow grooves that extend in a direction intersecting with the direction in which the sipe extends, and in which the facing groove walls are in contact with each other when the road surface is not grounded ,
The depth of the narrow groove is 5% to 20% with respect to the maximum protruding height of the block from the circumferential groove bottom or the lateral groove bottom,
A pneumatic tire in which the extending angle of the narrow groove is in a range of 30 ° to 60 ° with respect to the tread width direction . The pneumatic tire according to claim 1, wherein the sipe extends in a zigzag shape in a tread surface, and also extends in a zigzag shape in the depth direction.

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