JP2011183927A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having optimal tread pattern arrangement, without causing partial abrasion in a shoulder area, for sufficiently exhibiting respective performances, for making both compatible in a further improvement in on-ice performance and the other performance required for the tire. <P>SOLUTION: A polygonal block group formed by arranging a polygonal block of a plurality of pentagons or more partitioned/formed by a thin groove in a longitudinal row and a plurality of lateral rows of at least two rows, is arranged between two circumferential directional main grooves in a tread grounding width. The longitudinal row is arranged so as to be mutually different in a phase in the tire circumferential direction of the mutual polygonal blocks for constituting the adjacent longitudinal rows. The center in the tire width direction of the polygonal block group is positioned in an area having a width of 50% of the tread grounding width with a tire equatorial plane as the center. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a polygonal shape in which a plurality of pentagonal or more polygonal blocks defined by narrow grooves are arranged in at least two columns and a plurality of rows between two circumferential main grooves within the tread contact width. The present invention relates to a pneumatic tire provided with a block group.

  In a conventionally known tread pattern of a pneumatic tire for improving driving, braking and turning performance on snowy and snowy road surfaces, wet road surfaces, etc., as shown in FIG. A block pattern that uniformly partitions and forms a square shape or a triangular shape within the tread contact surface is used, and in addition, in order to improve the performance on ice and snow using the edge effect, sipes are placed in the block where the partition is formed. It is widely and generally provided.

  Here, when the sipe is formed as described above for improving the edge effect, the blocks divided by the sipe may fall down at the time of contact with the ground, so usually the ground contact is improved and the performance on ice and snow is ensured. Therefore, these quadrangular and triangular blocks are designed with a uniform and relatively large ground contact area.

JP 2008-56057 A

  However, if a block pattern with a relatively large contact area is uniformly arranged in the tread contact surface in this way, the rigidity of each block will increase, so that each block will have sufficient flexibility when contacting the tire. Becomes difficult. As a result, with such a configuration, it is not easy to give the block sufficient road surface followability, particularly when stepping on or kicking out.

  On the other hand, in recent years, there has been an increasing demand for further improvements in vehicle performance. For winter pneumatic tires that are primarily intended for running on snowy and snowy roads, In addition, it is required to have various performances necessary for a tire in a well-balanced manner so as to have sufficient performance such as road surface followability of the block.

  As a result of intensive studies by the inventors of the present application under such a request, the block has a pentagonal or more polygonal shape as compared with the conventional case where a square or triangular block is provided in the tread ground plane. In addition, it was found that the performance on ice / snow can be improved and the better road surface followability of the block can be ensured when densely arranged with a relatively small contact area. This is because, when such a polygonal block is used, the total edge length and the number of edges are increased, and each block can be deformed more flexibly than the conventional one when rolling with a tire.

However, in the shoulder region (outer region in the width direction of the tread portion) of the tread portion of the tire, the belt layer positioned on the radially inner side of the shoulder region is forced by pressing the surface of the tread portion against a flat road surface. Stretched. When the tread portion leaves the road surface, the forcibly stretched belt layer attempts to return to its original shape. In this way, when the tire rolls, the shape deformation of the block is repeated in the shoulder region. It is known that due to this change in shape, shoulder fall wear and step-down wear are likely to occur particularly in the block land portion located in the shoulder region among the blocks forming the tread portion.
Therefore, if the above polygonal blocks are simply arranged uniformly on the entire surface of the tread, the polygonal blocks located in the shoulder region will be worn out among the plurality of polygonal blocks. There is concern.

  In addition, when a plurality of polygonal blocks are densely arranged, the groove width for partitioning the blocks is narrow, and the drainage line is not linear but has a complicated interlaced line. It becomes difficult to maintain sex. Accordingly, there is a concern that the drainage of the entire tire is deteriorated by uniformly arranging the polygonal blocks over the entire tread contact surface.

  Accordingly, the present invention provides an optimum tread pattern that exhibits each performance sufficiently and is less likely to cause uneven wear in the shoulder region in order to achieve further improvement in performance on ice and snow and other performances required for the tire. It is an object to provide a pneumatic tire having an arrangement.

On the other hand, the inventors of the present application have various performances such as performance on ice and snow, road surface followability, drainage, etc., all of which are important in terms of tire function. It was not necessarily uniform on the tread contact surface, and it was found that the tread contact surface area was different depending on the tire installation direction and the condition of the contact surface at the time of tire load rolling.
In addition to uniformly arranging the polygonal blocks on the tread contact surface, in consideration of the above facts and the characteristics of each tread contact surface area, By arranging the shape block at the optimum position in the tread contact surface, the idea of realizing a more effective tread pattern having various balances required for the tire in a well-balanced manner as a whole tire was obtained.

That is, the pneumatic tire according to the present invention is
Provided between two circumferential main grooves within the tread contact width is a polygonal block group in which a plurality of pentagonal or more polygonal blocks defined by narrow grooves are arranged in at least two columns and a plurality of rows. The columns are arranged such that the phases in the tire circumferential direction between the polygonal blocks constituting the adjacent columns are different from each other,
The center in the tire width direction of the polygonal block group is a pneumatic tire characterized by being located in a region having a width of 50% of the tread contact width with the tire equatorial plane as the center.

  Here, the “tread contact width” is an industrial standard effective in an area where a tire is produced or used, for example, The Tire and Rim Association Inc. in the United States. Assembling the tires to the standard rims of the standard sizes described in “Year Book” in Europe, “Standard Manual” of The European Tire and Rim Technical Organization in Japan, and “JATMA Year Book” of Japan Automobile Association in Japan, This refers to the maximum width of the surface where the tire surface comes into contact with the ground in the state where the maximum load (maximum load capacity) of the single wheel in the applicable size and the air pressure corresponding to the maximum load are applied.

  Further, the “vertical column” referred to here is a column composed of polygonal blocks arranged at predetermined intervals in the circumferential direction. A plurality of columns are arranged in at least two rows in the tire width direction.

  Arranging the polygonal blocks so that the phases are different in the tire circumferential direction means that on the tread surface, a plurality of polygonal blocks of the same shape that make up the columns form individual polygonal blocks that make up the adjacent columns It is a state in which they are arranged in a staggered manner so as to be displaced from each other in the circumferential direction.

  The “center in the tire width direction of the polygonal block group” refers to the center in the tire width direction of a region where the polygonal blocks are densely arranged. That is, when the polygonal blocks are arranged in a plurality of rows, it is the center of the line segment connecting the outermost points in the tire width direction of the two polygonal blocks located on the outermost side in the tire width direction.

Further, in the pneumatic tire according to the present invention, the mounting direction to the vehicle is determined, and when the vehicle is mounted, the center in the tire width direction of the polygonal block group is in the tread half region which is the inside of the vehicle. It is preferable that it exists in the tread half area used as the vehicle outer side.
Here, “the direction of mounting on the vehicle is determined” means that an indicator such as a character, figure, pattern or the like indicating the mounting direction on the vehicle is attached to the user on the outer surface of the tire. Say that.

Moreover, in the pneumatic tire according to the present invention, a side block row in which a plurality of side blocks partitioned by the circumferential main grooves, the widthwise lateral grooves, and the narrow grooves are arranged in the circumferential direction is the polygonal block group. It is preferable that one row is provided on each side of the tire width direction.
The “widthwise transverse groove” referred to here refers to a transverse groove that intersects the circumferential narrow groove formed on the outside in the widthwise direction and the circumferential main groove of the outermost polygonal block in the widthwise direction.

Moreover, in the pneumatic tire according to the present invention, it is preferable that lengths in the tire width direction of the polygonal block group and the side block row are 7.5% to 50% of the tread contact width.
Here, “the length in the tire width direction of the polygonal block group and the side block row” means that the two circumferential main grooves defining the side block in the cross section in the tire width direction are on the side of each polygonal block group. This is the length of the line connecting the points.

  Moreover, in the pneumatic tire according to the present invention, it is preferable that the depth of the narrow groove defining the polygonal block is smaller than the depth of the circumferential main groove.

In the pneumatic tire according to the present invention, the actual ground contact area of the polygonal block each is preferably 50mm ² ~250mm ^2. Here, the “actual ground contact area” refers to the surface area of the polygonal block in an unloaded state.

In the pneumatic tire according to the present invention, the polygonal block includes a reference pitch length of the polygonal block group as PL (mm), a width of the polygonal block group as GbW (mm), and the reference pitch length. When the number of the polygonal blocks existing in the reference area of the polygonal block group divided by the width PL and the width GbW is a, and the negative rate in the reference area is N%,
S = a / (PL × GbW × (1-N / 100))
The block number density S per unit actual ground contact area of the polygonal block group given by is preferably in the range of 0.003 / mm ² or more and 0.04 / mm ² or less.

  Here, the “reference pitch length of the polygonal block group” refers to the minimum unit of the repeating pattern of the polygonal block in one column constituting the polygonal block group within the tread contact width, For example, when a repeating pattern of a pattern is defined by one polygonal block and a groove that divides the polygonal block, the tire circumferential length of one polygonal block and the tire circumferential direction of this polygonal block are adjacent to each other. The sum of the tire circumferential length of one groove to be used is the reference pitch length of the polygonal block.

  The “width of the polygonal block group” refers to the length of the polygonal block group in the tire width direction within the tread contact width.

  The “real contact area” of the polygonal block group means the total surface area of all the polygonal blocks in the reference area of the polygonal block group, and is, for example, the product of the reference pitch length PL and the width GbW. It refers to the area defined by subtracting the area of the grooves defining the individual polygonal blocks from the area of the reference area.

In the pneumatic tire according to the present invention, it is preferable that at least one of the circumferential main grooves has a bottom-up block in the groove.
Here, the “bottom-up block” is a block formed in the groove, and one side in the width direction is connected to the side block, and means a block having a lower block height than the side block.

  According to the present invention, by considering the characteristics of each area of the tread contact surface according to the state of use, not only the performance on ice and snow but also various other tire performances are provided, and uneven wear in the shoulder area is unlikely to occur. A pneumatic tire having an optimal tread pattern arrangement can be provided.

(A) is the partial expanded view which showed the tread pattern of one Embodiment of the pneumatic tire according to this invention, (b) is the figure which expanded a part of (a). (A) is a figure which shows the state of the negative camber at the time of tire mounting, (b) is the partial expanded view which showed one Embodiment of the tread pattern of the pneumatic tire according to this invention in the mounting state of (a). It is. (A) is a figure which shows the state of the negative camber at the time of tire mounting, (b) is the partial expanded view which showed one Embodiment of the tread pattern of the pneumatic tire according to this invention in the mounting state of (a). It is. It is a figure which shows the bottom raising block provided in a circumferential direction main groove, and is the arrow line view cut | disconnected along line PP of FIG.2 (b). It is a figure which shows the tread pattern of a comparative example tire. It is a figure which shows the tread pattern of the conventional tire.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial development view showing a tread pattern of a pneumatic tire (hereinafter referred to as “tire”) according to an embodiment of the present invention. In the drawing, the vertical direction indicates the tread circumferential direction, and the horizontal direction (direction perpendicular to the equator plane C) indicates the tread width direction.

As shown in FIG. 1, a plurality of pentagons that are partitioned by a first narrow groove 3 a and a second narrow groove 3 b in a part of the tread region between the tread grounding ends 2, 2 of the tire 1. A polygonal block group Gb in which the polygonal blocks 4 (hereinafter simply referred to as “polygonal blocks”) are densely arranged is arranged.
Here, the first narrow groove 3a refers to a groove in a substantially width direction between polygonal blocks, and the second narrow groove 3b refers to a groove that intersects the first narrow groove 3a. . These grooves have widths such that adjacent polygonal blocks are not completely constrained to each other and each block can be moved individually, and preferably have a width of 0.7 mm to 3 mm. It is.

  In the tire of this embodiment, as described above, since the configuration in which the polygonal blocks 4 are densely arranged while ensuring a sufficient negative rate in the polygonal block group Gb is adopted, the total edge of each block The length and edge direction (the number of edges facing different directions) can be increased, and an excellent edge effect can be exhibited. As a result, the performance on ice and snow can be improved. In addition, by forming blocks with grooves instead of sipes, individual blocks can be moved independently while being densely arranged, and can be flexibly deformed at the time of grounding, improving the grounding performance of the tread, As a result, the performance on ice and snow can be improved more effectively.

  The polygonal blocks 4 are arranged in a plurality of columns, preferably at least two or more columns in the tire width direction, which are arranged at predetermined intervals in the circumferential direction. Further, the polygonal blocks 4 and 4 forming adjacent columns are arranged so that the phases are different in the tire circumferential direction. That is, the polygonal blocks 4 are arranged in a staggered manner (staggered lattice shape) in the tire circumferential direction.

  Here, the phase being different in the tire circumferential direction means a state in which centroids of adjacent polygonal blocks forming adjacent columns are not located on the same straight line in the tire width direction. For example, in the example shown in FIG. 1, the centroid of the polygonal block row L1 and the polygonal block constituting the polygonal block row L2 adjacent to the polygonal block row L1 are shifted in the tire circumferential direction by half the block. . Accordingly, when there are a plurality of block rows shifted in the tire circumferential direction by half a block in this way, when focusing on the plurality of polygonal blocks arranged on the tread surface in the tire width direction, every row ( Polygonal blocks forming every other column) are arranged in the same phase in the tire width direction (that is, the centroids are located on the same straight line).

  However, the positions of the columns having different phases in the tire circumferential direction are not necessarily different from each other by half of the blocks as described above. Therefore, although not shown, the polygonal blocks having the same phase are not necessarily blocks that form columns for every column, but may be blocks that form columns every plurality of columns.

  In this way, by arranging the polygonal blocks of the polygonal block group so that the phases are different in the tread circumferential direction, the blocks can be arranged densely and the space on the tread surface can be used effectively. When moving, under the formation of a larger number of polygonal blocks, the edges of each block can be acted on one after another to achieve a better edge effect. Also, if the phases are shifted in this way, the timing of grounding to the road surface can be shifted between blocks adjacent in the tread width direction, so that pattern noise can be reduced.

Note that in the polygonal block group Gb of this tire 1, the actual ground contact area of each of which is 50mm ² ~250mm ^2, it is preferable that a relatively small block.

If a relatively small block is used, the rigidity of the block will be reduced, so that the flexibility of the block will be improved, the tread will be more grounded, and in particular, performance on ice and snow (brake, traction, cornering, etc.) will be improved. Because it can. In addition, since the distance from the central area of the block to the peripheral edge of the block can be reduced by using a relatively small block, the water film removal effect by the polygonal block 4 can also be improved. Therefore, according to the tire of this embodiment, the performance on ice and snow is drastically improved by realizing excellent grounding property and edge effect and efficiently removing the water film by the polygonal block 4. be able to.
Here in the range of 50mm ² ~250mm ^2, when thus smaller than 50 mm ^2, the height of the block is higher than the block surface area than (i.e. deep groove), the reduction in the bending rigidity of the block This is because falling occurs, and handling of dry performance / wet performance / ice performance / snow performance deteriorates. On the other hand, if it is larger than 250 mm ² , the performance on ice and snow cannot be improved by using a relatively small block as described above. Moreover, if each block is enlarged, the drainage resistance due to the polygonal block increases when traveling on a wet road surface, and the hydroplaning performance deteriorates.

Further, in the polygonal block group Gb of the tire 1, the reference pitch length of the polygonal block is PL (mm), the width of the polygonal block group Gb is GbW (mm), the reference pitch length PL and the width. The number of polygonal blocks 4 existing in the reference zone Z (shaded area in FIG. 1A) of the polygonal block group Gb divided by GbW is a, and the negative rate in the reference zone Z is N %
S = a / (PL × GbW × (1-N / 100))
It is preferable that the block number density S per unit actual ground contact area of the polygonal block group Gb is in the range of 0.003 / mm ² or more and 0.04 / mm ² or less.

When the number density S of the polygonal blocks is less than 0.003 / mm ² , it is difficult to realize a high edge effect without forming a sipe, while the number density S of the polygonal blocks is 0.04 / mm2. too small polygonal blocks exceeds mm ^2, because it is difficult to realize the desired block rigidity.

  Here, when counting the number a of blocks a in the reference zone Z, if the block exists between the inside and outside of the reference zone Z and cannot be counted as one, it is within the reference zone with respect to the surface area of the block. The remaining area ratio of the remaining blocks is counted. For example, in the case of a block straddling the inside and outside of the reference area Z and only half of the block exists in the reference area Z, it can be counted as 1/2.

  In the above formula, the “reference pitch length” refers to the minimum unit of the repeated pattern of polygon blocks in one block column constituting the polygon block group Gb. For example, one polygon block 4 is When the repeated pattern of the pattern is defined by the first narrow groove 3a and the second narrow groove 3b that define the polygonal block 4, the length in the tire circumferential direction of one polygonal block and the polygonal block The reference pitch length is obtained by adding the tire circumferential direction length of one first narrow groove 3a adjacent in the tire circumferential direction.

  The “real contact area” of the polygonal block group Gb refers to the total surface area of all the polygonal blocks in the reference area of the polygonal block group Gb. For example, the reference pitch length PL and the polygonal shape From the area obtained by subtracting the areas of the first fine grooves 3a and the second fine grooves 3b defining the individual polygonal blocks 4 from the area of the reference area defined by the product of the block group width GbW. Can be sought.

  Further, in the tread region between the tread grounding ends 2 and 2 of the tire 1, the circumferential main grooves 5 and 6 and the lateral transverse grooves are formed on both sides in the tire width direction of the polygonal block group Gb formed as described above. 7 and 8 and blocks formed by the first and second narrow grooves 3a and 3b (hereinafter referred to as “side blocks 9”) are arranged in the circumferential direction.

The side blocks 9 are arranged as side block rows SB and SB one by one between the polygonal block group Gb and the circumferential main grooves 5 and 6, respectively. And the block shape by the side of the polygonal block group Gb of the side block 9 is formed in the zigzag shape according to the shape of the polygonal block 4 like the example shown in FIG. The block shape on the 6th side is preferably formed so as to have a straight part so that the groove is linear.
This is because, by forming the circumferential main groove in a straight line, drainage can be improved, and straight running stability on ice and snow can be improved. On the other hand, by forming a groove in accordance with the shape of the polygonal block 4 on the side of the polygonal block group Gb, a groove around the polygonal block 4 (that is, between the polygonal block 4 and the side block 9 (that is, This is because a groove having the same shape and width as the narrow grooves 3a and 3b) can be secured, so that the same effect as that of other polygonal blocks can be obtained also in the polygonal blocks adjacent to the side blocks.

Further, the side block 9 is formed to have a larger ground contact area than the polygonal block 4.
When the tire is loaded, the shoulder block collapses due to the load from the cornering or rim, and a force is applied from the outer side to the inner side in the tire width direction, which may cause a load on the block in the center of the tread. . At this time, if the ground contact area of the side block 9 formed in the circumferential direction so as to surround the polygonal block group Gb is increased as described above to increase the rigidity of the block, this side block 9 becomes the outer side in the tire width direction. Therefore, the force applied from the outside in the width direction to the polygonal block 4 located closer to the center of the tread than the side block 9 can be suppressed. As a result, since the polygonal block 4 positioned between the side blocks 9 and 9 can be grounded in a good state, the above-mentioned performance on ice and snow can be effectively exhibited.

Moreover, it is preferable that the actual ground contact area of one side block differs from the actual ground contact area of the block of the other side in the side blocks 9 and 9 located on both sides in the tire direction across the polygonal block group Gb.
As described above, when the tire is loaded, the shoulder-side block falls due to cornering or a load applied from the rim, and the block located on the outer side in the tire width direction is more likely to receive a force from the outer side in the tire width direction toward the inner side. Accordingly, it is preferable to increase the actual contact area of the side block located on the outer side in the tire width direction among the both side blocks sandwiching the polygonal block group Gb. This is because by increasing the block rigidity of the side block, it is possible to reduce the lateral force load on the polygonal block located on the inner side in the tire width direction. The actual ground contact area of the side block located on the inner side (opposite side) in the tire width direction is preferably smaller than the actual ground contact area of the side block located on the outer side in the tire width direction. If a large block is placed on both sides of the polygonal block, the polygonal block sandwiched between these large blocks cannot be moved flexibly, and the above-mentioned effects such as performance on ice and snow can be sufficiently exhibited. Will not be able to. Therefore, by reducing the size of one side block, the edge component of the block is increased, and the traction performance and braking performance on ice and snow can be improved as in the case of the adjacent polygonal block.

  Moreover, it is preferable that the width direction horizontal groove between the side blocks which divide and form a side block is 1 mm-8 mm. If the actual ground contact areas of the side blocks in the tire width direction are different as described above, the number of width direction lateral grooves formed between the side blocks having a larger block area is reduced, and the width of the width direction lateral grooves is reduced accordingly. It is preferable that the width is larger than the lateral groove formed between the side blocks having a small block area. In the example shown in FIG. 1, the widthwise lateral grooves 8 formed between the side blocks having a large block area are formed larger than the widthwise lateral grooves 7 formed between the side blocks having a small block area. Specifically, the widthwise lateral groove between the side blocks having the larger block area is preferably 3 mm to 8 mm. This is because the groove volume can be secured and the traction brake performance on snow can be improved. On the other hand, the widthwise lateral groove between the side blocks having a smaller block area is preferably 1 mm to 5 mm. This is because the groove width of the side block having the smaller block area can be increased by reducing the groove width. Thus, the groove width of the widthwise lateral groove can be appropriately changed according to the target performance of the tire.

  In addition, as shown in FIG. 1, it is preferable to form sipes in the polygonal block and the side block. By forming the sipe, it is possible to enhance the water removal effect in the central region of each block and improve the performance on ice and snow using the edge effect of each block. Moreover, since the flexibility of the tread is improved, the grounding property can be improved. However, such a sipe does not necessarily need to be formed, and may be appropriately formed as necessary. This is because, by not forming sipes, it is possible to increase the rigidity of each block and make it difficult for the blocks to collapse.

  In the pneumatic tire according to the present invention, as shown in FIG. 1, the tire width direction center GbC of the polygonal block group Gb has a tread grounding width TW (between the tread grounding ends 2 and 2 between the tire equatorial plane C). It is located within the tread ground contact width TWh having a width of 50% of the tread width). That is, the tire width direction center GbC of the polygonal block group Gb is located in a width region of 25% of the tread ground contact width with respect to the tread region on the left and right from the tread center, and the polygonal block group Gb is It will be located near the center of the tread.

As described above, uneven wear tends to occur in the shoulder region of the tread portion, but the mechanism of occurrence of uneven wear will be briefly described.
When a load is applied to the tire, a vertical force is applied from the rim to the tread surface. This vertical force passes through the bead portion and the sidewall portion, and then passes substantially inward in the tire width direction through the shoulder region. This is transmitted as a lateral force toward the center of the tread. When this lateral force is transmitted, the tread block receives a force inward in the width direction. Among the tread blocks, the block in the vicinity of the road surface located outside in the tire width direction (that is, the block in the shoulder region). ), The most shear deformation occurs. Further, not only when a load is applied, but also during cornering, the shoulder region block located on the outer side in the tire width direction, particularly the block located near the ground contact end, is most likely to be deformed.

Therefore, by arranging the polygonal block group near the tread center instead of the shoulder region as in the present invention, it is possible to reduce the influence of the polygonal block from the lateral force, such as on-ice performance and road surface followability. It is possible to make the original functions effective. In other words, since the polygonal block is not arranged in the shoulder region that is easily affected by the shear deformation, the polygonal block is hardly worn by the influence of the lateral force or the like. Therefore, the shape of the polygonal block can be maintained in a good state for a long time.
Further, the tire equatorial plane C, which is the center of the tread portion, is included in a region having a high probability of being in contact with the road surface regardless of whether it travels perpendicularly to the road surface or has an inclination angle such as cornering. Therefore, if the configuration in which the center GbC in the tire width direction of the polygonal block group Gb is located in a region having a width of 50% of the tread contact width TW with the tire equatorial plane C as the center, the polygonal block group Gb is the tire equator. Since it is arranged closer to the surface C, it is possible to effectively exhibit performance on ice and snow, road surface followability, and the like in the central region of the tread.

Here, in general, pneumatic tires, such as negative camber or positive camber, when the vehicle is set to have a camber angle, or when the camber angle is used due to a change in load or a change over time during use of the tire The frequency of ground contact with the road surface of the tread and the load on the tread portion are different between the inner side and the outer side of the vehicle.
That is, in the case of a negative camber, the tread portion that is on the inner side of the vehicle is strongly grounded to the road surface, and the tread portion that is on the outer side of the vehicle mounting tends to be lifted off the road surface. On the other hand, in the case of the positive camber, the tread portion that is on the outside of the vehicle is strongly grounded to the road surface, and the tread portion that is on the inside of the vehicle tends to lift from the road surface.

  Therefore, in the pneumatic tire according to the present invention, as shown in FIG. 1, it is preferable that the center GbC in the tire width direction of the polygonal block group Gb exists only in either one of the tread half regions. That is, the polygonal block group Gb is preferably arranged so that the length in the tire width direction is asymmetric with respect to the tire equatorial plane C in the tread contact surface. Specifically, in FIG. 1, when the tread region having the tread contact width TW is divided into the left and right with respect to the paper surface with the equator plane C as a boundary line, the tire width direction center GbC of the polygonal block group Gb is It is preferably arranged in either the left half region or the right half region.

  When the vehicle has a camber angle, the tread portion in the half area on either the inside or the outside of the vehicle is in contact with the road surface. Therefore, the number of edges in the tread half area can be increased by arranging the polygonal block 4 in the tread half area on the side in contact with the road surface according to the direction and situation when traveling, and the block is independent. This is because it is possible to further improve the performance on ice and snow and the road surface followability. On the other hand, by arranging a normal block pattern in other tread areas, it is possible to maintain other performances necessary for the tire (for example, tread grounding performance and hydroplaning performance) in a good state. Because it becomes.

In other words, if the polygon block group is simply provided on the tread surface ignoring the presence of the camber angle, the block is placed in an area where the contact frequency with the road surface is low even when the polygon block is placed. In such a case, the effect of the polygonal block that improves the performance on ice and snow cannot be used effectively.
Conversely, if the polygonal blocks are densely packed in the tread region where the frequency of ground contact with the road surface is low, the rigidity of the entire tire is lowered, and the overall ground contact performance may not be maintained well. In addition, if too many polygonal blocks that are intricately arranged are disposed on the whole, drainage is disadvantageous, and the hydroplaning performance may not be maintained well.
Therefore, according to the performance required for each area of the tread, by selecting and arranging blocks each having different performance, an overall better pneumatic tire having various tire performances can be obtained. It becomes possible to provide.

Specifically, as shown in FIG. 2B, in the case of a negative camber in which the orientation of the vehicle is determined so that the direction indicated by the arrow is the inside of the vehicle, the tread portion that is the inside of the vehicle is A polygonal block group Gb is arranged on the area plane.
Under the negative camber, the region on the inner side of the tire equatorial plane C is the region directly below the ground contact with the road surface. If the ground contact area is located relatively inside in the vehicle width direction, it will affect the performance when traveling straight, especially when the polygonal block group is in the ground contact area. The brake / traction performance on ice and snow during straight traveling can be improved by the function of the polygonal block having such performance on ice and snow and road surface followability.

Conversely, as shown in FIG. 3B, in the case of a positive camber in which the orientation of the vehicle is determined so that the direction indicated by the arrow is the inside of the vehicle, the region of the tread portion that is the outside of the vehicle A polygonal block group Gb is arranged on the surface.
Under the positive camber, the region on the outer side of the tire equatorial plane C is the region directly below the ground contact with the road surface. If the ground contact area is located relatively outside in the vehicle width direction, it will affect the performance especially during cornering while traveling. Thus, if the polygonal block group is in the ground contact area, the above-mentioned Thus, it is possible to improve the performance on ice and snow due to having many edge components. In addition, the function of the polygonal block having the grounding performance and the like can particularly improve the handling performance during cornering.

  Further, the tire width direction length W of the polygonal block group Gb and the side block row SB, that is, the tire width direction length between the two circumferential main grooves 5, 6 defining the side blocks 9, 9 is It is 7.5 to 50% of the tread contact width TW, more preferably 15 to 40%.

As described above, when the polygonal block 4 is provided, the performance on ice and snow can be advantageously improved. Therefore, the region of the polygonal block group Gb is preferably wide. On the other hand, since the polygonal block 4 has an intricate shape of a pentagon or more, if these are densely arranged in the entire tread, the drainage performance may deteriorate and the hydroplaning performance may deteriorate. is there.
Therefore, in consideration of the above facts, in order to maintain both the performance on ice and snow and the hydroplaning performance in a balanced manner, the polygonal block group Gb and the side block row SB are 7.5 to 50% of the tread ground contact width TW. It is preferable to arrange in the range. If it is less than 7.5% of the tread contact width TW, the performance on ice and snow cannot be effectively improved. If it is longer than 50% of the tread contact width TW, the hydroplaning performance is good. This is because it cannot be secured. This is more effective when the polygonal block group Gb and the side block row SB are arranged in a range of 15 to 40% of the tread ground contact width TW.

The groove depths of the first narrow grooves 3 a and the second narrow grooves 3 b that define the polygonal block 4 are smaller than the groove depths of the circumferential main grooves 5 and 6 that define the side blocks 9 and 9. It is preferable to configure as described above.
Since the polygonal block 4 has a relatively small contact area, the rigidity of the polygonal block 4 is lower than the rigidity of the side block 9. Therefore, by forming the groove depths of the first narrow groove 3a and the second narrow groove 3b that define the polygonal block 4 to be smaller than the groove depths of the circumferential main grooves 5, 6, the polygonal block can be a little. This is because the rigidity of 4 can be increased and the running stability can be improved. As a result, since the ground contact property of the polygonal block 4 is stabilized, the performance on ice and snow by the polygonal block can be functioned more effectively. In this way, by reducing the depth of the first narrow groove 3a and the second narrow groove 3b, mainly the handling performance of dry performance / wet performance / on-ice performance / on-snow performance, and braking performance on ice. / Uneven wear performance can be improved.

  In addition, as shown in FIG. 4, it is preferable to provide a bottom-up block (grooving) 10 in the circumferential main grooves 5 and 6 that define the side blocks 9 and 9. FIG. 4 is an arrow view cut along the line PP in FIG. In this embodiment, a bottom-up block 10 is provided in the circumferential main groove 5, and a pocket 10 a extending substantially in the tire width direction is formed in the bottom-up block 10. With this configuration, the block edge is also formed in the main groove, so that the performance on snow can be improved. Further, since the opening of the main groove has a sufficient groove width, the hydroplaning performance is not deteriorated. The bottom-up block may be provided in either one of the circumferential main grooves (5 or 6) or in both the circumferential main grooves (5 and 6).

  Next, an example tire according to the present invention and a conventional tire according to the prior art were respectively prototyped, and performance evaluations on ice performance and snow performance were performed. Moreover, since evaluation of partial wear in the shoulder region in the example tires was also performed, these will be described below.

An example tire is a tire provided with the polygonal block group and the side block row shown in FIG. 1 of a radial tire for a passenger car having a size of 195 / 65R15. In this tire, a part of the tread portion has a block group in which a plurality of independent blocks, which are defined by grooves, are densely packed. The surface contour shape of each block was a substantially regular octagon, and the size of each part was as follows.
Circumferential main groove: 5 mm, 12 mm, 7 mm (from the left side of FIG. 1)
Groove depth of circumferential main groove: 9mm
Circumferential length of the polygonal block (BL): 13.0 mm
Length in width direction of polygonal block (BW): 15.6 mm
Distance between polygonal blocks adjacent in the tread circumferential direction (BGL): 3.4 mm
Distance between polygonal blocks adjacent in the tread width direction (BGW): 9.5 mm
Polygon-shaped block height (BH): 7 mm
Reference pitch length (PL): 32.9 mm
Width of polygonal block group and side block row: 52.1 mm
Ratio of contact width of polygonal block group: 32%
Side block (center side) length: 14.9mm
Side block (outside) length: 28.8mm
Polygon shaped block area: 154mm ²
The central position in the width direction of the polygonal block group: 17.5 mm from the tire equator to the inside of the vehicle (the center position of the tire half width is 40 mm from the tire equator)

  First, this example tire was mounted on a vehicle such that the center of the polygonal block group in the tire width direction was on the inside of the vehicle, and performance evaluation of ice brake / traction performance and snow brake / traction performance was performed.

  Next, the same example tires as described above are mounted on the vehicle so that the center of the polygonal block group in the tire width direction is on the outer side of the vehicle, and performance evaluation of ice cornering / brake performance and snow cornering / brake performance is performed. went.

  On the other hand, the conventional tire is a tire having the tread pattern shown in FIG. 6, and the width of the circumferential main groove is 5 mm for both main grooves on the outer side in the tire width direction and 9.5 mm for the main groove on the inner side in the tire width direction. did. The other configuration was based on the tire of the example.

Above, the brake on ice is the index of the measured value of the braking distance when the test course on the ice plate road surface is fully braked at a speed of 20 km / h, and the traction on ice is the time from start to acceleration on the test course on the ice plate road surface. The index of the measured value, the cornering on ice indicates the index of the measured value of the overall feeling evaluation of the braking performance, the starting performance, the straight traveling performance, and the cornering performance in the test course of the ice sheet road surface. In addition, the snow brake accelerates the measured value of the braking distance when the test course on the pressure snow road surface is fully braked at a speed of 40 km / h, and the snow traction accelerates the test course on the snow snow road surface to an initial speed of 10 km / h to 45 km / h. The index of the measured value of the section time at the time, the cornering on the snow indicates the index of the measured value of the overall feeling evaluation of the braking performance, the starting performance, the straight traveling performance, and the cornering performance on the test course of the snowy road surface.
The evaluation in Table 1 indicates that the performance on ice or the performance on snow is improved as the numerical value is increased with the conventional tire having an index of 100.

  From the results in Table 1, the example tire in which the polygonal block group and the side block row are provided on a part of the tread surface is provided with the polygonal block group and the side block row on the inner side when the vehicle is mounted as in Example 1. In this case, the brake / traction performance on ice / snow is particularly good with respect to the conventional tire, and the brake / corning performance on ice / snow is particularly good with respect to the conventional tire when the vehicle is mounted outside as in the second embodiment. I found it excellent.

Further, the tires of Examples after measurement under the above conditions were visually evaluated for the occurrence of uneven wear in the shoulder region. As a result of the evaluation, in both Example 1 and Example 2, uneven wear in the shoulder region of the Example tire was not confirmed.
For comparison, a tire (hereinafter referred to as a comparative tire) in which a polygonal block as shown in FIG. 5 is arranged in the shoulder region on the inner side of the vehicle at the time of mounting is prepared, and uneven wear in the shoulder region is evaluated. did. The evaluation of uneven wear was performed by measuring the amount of step wear between blocks when traveling 5000 km in various driving modes on a general road in a dry state. The results are shown in Table 2 below.

  As a result, in the comparative tire, occurrence of uneven wear was confirmed in the blocks in the shoulder region.

  In addition, it is preferable that the surface outline shape of the polygonal block 4 arrange | positioned in a tread ground contact width is a polygonal shape more than a pentagon. This is because a sufficient contact area on the tire surface can be ensured by adopting this shape. Moreover, it is because it can mutually support the fall of a block between adjacent blocks, making each polygonal block movable independently.

More preferably, the surface contour shape of the polygonal block 4 is a substantially regular octagon as shown in FIG. This is because if the number of corners is too small, the block cannot fall down in many directions and the flexibility is poor. In addition, if the polygon is an octagon or more, one side becomes too short, and the surface in contact with the adjacent block when falling down becomes small, making it difficult to support each other. Therefore, when the surface contour shape is a substantially regular octagon, the block falls down in many directions and can sufficiently support the adjacent blocks. In addition, when the surface contour shape is a regular octagon, it is preferable that the 1st fine groove 3a which divides the polygonal block 4 has circumferential direction distance to such an extent that a groove | channel is not obstruct | occluded between adjacent blocks at the time of grounding. On the other hand, the second narrow groove 3b that intersects the first narrow groove 3a and is inclined with respect to the equator plane is formed such that adjacent blocks are close to each other to such an extent that the groove is closed at the time of ground contact. It is preferable.
However, the surface contour shape of the polygonal block of the present invention is not necessarily limited to the above shape. In this way, the grooves are partitioned and can move freely and independently so that each polygonal block can have flexibility when grounded without being constrained by the adjacent polygonal block. If possible.

  Moreover, arrangement | positioning, shape, etc., such as a polygonal block and a side block in the Example shown above are only illustrations, and another form can also be implemented. The number of block rows, the number of blocks, the shape, the size, and the like shown here are all examples for explaining the tire according to the present invention, and are appropriately changed without departing from the gist of the present invention. Note that this is possible.

  According to the present invention, by configuring the block shape and block arrangement according to the purpose of use and the situation when the tire vehicle is mounted, the performance on ice and snow is improved while ensuring various tire performances, and uneven wear in the shoulder region is reduced. It became possible to prevent the occurrence.

DESCRIPTION OF SYMBOLS 1 Tire 2 Grounding end 3a, 3b Narrow groove 4 Polygonal block 5, 6 Circumferential main groove 7, 8 Width direction lateral groove 9 Side block 10 Bottom raising block W Polygonal block group Gb and side block row SB length in tire width direction C Equatorial plane Gb Polygonal block group GbC Polygonal block group tire width direction center GbW Polygonal block group tire width direction length SB side block row TW Tread contact width TWh 50% width of tread contact width TW

Claims (9)

Provided between two circumferential main grooves within the tread contact width is a polygonal block group in which a plurality of pentagonal or more polygonal blocks defined by narrow grooves are arranged in at least two columns and a plurality of rows. The columns are arranged such that the phases in the tire circumferential direction between the polygonal blocks constituting the adjacent columns are different from each other,
The pneumatic tire is characterized in that the center of the polygonal block group in the tire width direction is located in a region having a width of 50% of the tread contact width with the tire equatorial plane as the center.   The direction of mounting to a vehicle is determined, and when the vehicle is mounted, the center in the tire width direction of the polygonal block group is in a tread half region which is the inside of the vehicle. Pneumatic tires.   The mounting direction to a vehicle is determined, and when the vehicle is mounted, the center in the tire width direction of the polygonal block group is in the tread half region which is the vehicle outer side. Pneumatic tires.   Side block rows formed by arranging a plurality of side blocks defined by the circumferential main grooves, the width direction lateral grooves, and the narrow grooves in the circumferential direction are provided on both sides of the polygonal block group in the tire width direction. The pneumatic tire according to any one of claims 1 to 3, wherein   5. The tire width direction length of the polygonal block group and the side block row is 7.5% to 50% of the tread ground contact width, according to claim 1. Pneumatic tires.   The pneumatic tire according to any one of claims 1 to 5, wherein a depth of the narrow groove defining the polygonal block is smaller than a depth of the circumferential main groove. The actual ground contact area of the polygonal blocks each of which being a 50mm ² ~250mm ^2, pneumatic tire according to any one of claims 1 to 6. The polygonal block is defined by a reference pitch length of the polygonal block group as PL (mm), a width of the polygonal block group as GbW (mm), and the reference pitch length PL and the width GbW. When the number of polygonal blocks existing in the reference area of the polygonal block group is a, and the negative rate in the reference area is N%,
S = a / (PL × GbW × (1-N / 100))
The block number density S per unit actual ground contact area of the polygonal block group given by is within a range of 0.003 / mm ² or more and 0.04 / mm ² or less. The pneumatic tire according to any one of 1 to 7.   The pneumatic tire according to any one of claims 1 to 8, wherein at least one of the circumferential main grooves has a raised block in the groove.

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