JP5340073B2 - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of restraining shoulder-dropping abrasion and step-down abrasion, even when a small block is arranged in a shoulder area for further effectively improving rolling resistance. <P>SOLUTION: A vertical row is arranged so that the mutual small blocks for constituting an adjacent vertical row are different in a phase in the tire peripheral direction, and has a lateral force regulating part constituted of a joining element joined to a buttress block and a land element connected to the joining element and extending inside in the tire width direction, between the small blocks for constituting the outermost vertical row in the tire width direction. The land element and the small block adjacent inside in the tire width direction of the outermost small block in the tire width direction, are joined at least in tread grounding time. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention provides a small block group in which a plurality of small blocks defined by grooves are arranged in a plurality of columns and a plurality of rows within the tread contact width, and the tread contact is provided outside the small block in the tire width direction. The present invention relates to a pneumatic tire provided with a buttress block array composed of buttress blocks extending across the ends.

  Since the rolling resistance of the tire affects the fuel consumption of the vehicle, the necessity of reducing this rolling resistance has been increased in accordance with the recent consideration for environmental load. In order to reduce rolling resistance, it is necessary to reduce the energy consumed by the stress and strain accompanying the rolling of the tire, but the bead portion and the sidewall portion extending outward in the tire radial direction from the bead portion It is known that the energy consumed in the tread portion is the largest when comparing the energy consumed in the tread portion located across both sidewall portions.

  For the purpose of reducing this rolling resistance, for example, in the tire described in Patent Document 1, from the ground contact end of each block in the block row of the shoulder region (width direction outer portion of the tread portion) to the portion outside the tire axial direction. The structure which provides a sipe is adopted. By providing the sipe in this way, when the tire travels and enters the ground contact area, the circumferential and axial shear strain generated from the shoulder area to the buttress area (side wall portion side portion from the shoulder area) is alleviated. Because.

JP-A-7-228106

  By the way, in this patent document 1, as a block provided in a tread part, the rectangular parallelepiped comparatively big block (For example, it is divided into five in the tire width direction) is employ | adopted. However, even if a sipe is provided on the outer side in the tire axial direction from the grounding end of the block, in such a relatively large block, when the tire rotates and enters the grounding area, the grounding area for each block is wide. It becomes. Each block receives an impact from the road surface at the time of ground contact, but it is difficult for the block to have appropriate flexibility when the ground contact area of each block is wide. Therefore, in recent years, it has been demanded that the block on the surface of the tread has an appropriate flexibility to obtain further good rolling resistance. This flexibility has been required among the blocks on the tread surface, in particular, for blocks located in the shoulder region where the block deformation is large during impact from the road surface or cornering.

  In response to the above requirements, the applicant further effectively reduces the rolling resistance of the tire by providing a group of blocks formed by closely gathering a plurality of small blocks partitioned by grooves in the shoulder region of the tread surface. I found that I can do it. In this way, if a plurality of small blocks are provided, the ground contact area between the tire tread surface and the road surface of the block is subdivided at the time of ground contact, so that each block can have flexibility. .

However, when a large number of small blocks are arranged on the tread surface in this manner, the width of the land portion in the width direction of the small blocks is reduced, so that the shear rigidity in the width direction is lowered.
And when the tire rolls, the tread surface that is rounded with a certain curvature is forced against the flat ground, and the round shape is forced to deform straight, but this forced deformation is In particular, it occurs in small blocks located in the shoulder region of the tread surface. Then, the deformation in the width direction is repeatedly performed on the small block located in the region, forcibly deforming when pressed against the ground and returning to the original when leaving the ground. In this way, the small block located in the shoulder region causes the most shear deformation.
In cornering, in particular, lateral force in the width direction is applied to the small blocks located in the shoulder region on the tread surface. Therefore, also by this lateral force, the small block located in the portion is most susceptible to shear deformation.

As described above, the shear deformation is most likely to occur in the small block in the shoulder region. However, as this is repeated, the small block may not withstand the shearing force, and shoulder fall wear or step down wear may occur.
It has been found that this shoulder fall wear and step down wear are most likely to occur particularly in the block rows formed by the small blocks located on the outermost side in the tire width direction among the small blocks formed in the shoulder region.

  Accordingly, it is an object of the present invention to solve the above-mentioned problems, and even if a small block is arranged in the shoulder region in order to improve the rolling resistance more effectively, the shoulder drop wear Another object of the present invention is to provide a pneumatic tire that can suppress step down wear.

In order to achieve the above object, this pneumatic tire is
Provided within the tread contact width is a small block group in which a plurality of small blocks partitioned by grooves are arranged in a plurality of columns and a plurality of rows, and across the tread contact end on the outer side in the tire width direction of the small blocks. In a pneumatic tire provided with a buttress block row consisting of extending buttress blocks,
Both regions outside the position corresponding to 80% of the tread contact width with respect to the tire equatorial plane as a shoulder region are shoulder regions, and at least a part of the small blocks constituting the small block group in the shoulder region. And place
The columns are arranged so that the small blocks constituting the adjacent columns have different phases in the tire circumferential direction,
In the shoulder region, a reference pitch length of the small block group is PL (mm), a width of the small block group is SAW (mm), and the small blocks are divided by the reference pitch length PL and the width SAW. When the number of the small blocks existing in the reference area of the group is a (pieces) and the negative rate in the reference area is N (%),
a / (PL × SAW × (1-N / 100))
The block number density S per unit actual contact area of the small block group given by is in the range of 0.003 / mm ² or more and 0.04 / mm ² or less,
A lateral force restricting portion constituted by a joining element joined to the buttress block and a land element connected to the joining element and extending inward in the tire width direction between the small blocks constituting the outermost column in the tire width direction. Prepared,
The pneumatic tire is characterized in that the land element and the small block adjacent to the inner side in the tire width direction of the outermost small block in the tire width direction are joined at least at the time of tread contact.

  Here, the “tread contact width” is an industrial standard effective in an area where tires are 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. The “tread contact end” means the outermost point of the tread contact width in the tire width direction.

  Further, the “column” referred to here means a column made up of small blocks arranged at a predetermined interval in the circumferential direction. Multiple columns are arranged in the tire width direction. And “so that the phase in the tire circumferential direction is different” means that on the tread surface, a plurality of small blocks of the same shape constituting the column are mutually in the circumferential direction with each of the small blocks constituting the adjacent column. It refers to the state of staggered arrangement.

  The “reference pitch length of the small block group” here refers to the minimum unit of the repeated pattern of small blocks in one column constituting the small block group. For example, one small block and its small block If the repeating pattern of the pattern is defined by the groove that divides, the tire circumferential length for one small block and the tire circumferential length for one groove adjacent to the tire circumferential direction of this small block are added. This is used as the reference pitch length of the small block.

  The “small block group width SAW” refers to the length in the tire width direction of the small block group in the small block region.

  The “actual ground contact area” of the small block group means the total surface area of all blocks in the reference area of the small block group. In other words, it is defined by the product of the reference pitch length PL and the width SAW. The area obtained by subtracting the area of the groove defining each small block from the area of the reference area.

  In addition, “between small blocks constituting the outermost column in the tire width direction” means a circumferential space formed by the small blocks in a plurality of small blocks arranged in the first column from the tire width direction. Say that.

  In addition, “join at least when the tread is grounded” means that when the tread is not grounded, the end of the land element in the tire width direction and the small block may or may not be in contact with each other. This means that when the tread contacts the road surface, the end of the land element on the inner side in the tire width direction comes into contact with the small block.

  Moreover, in the pneumatic tire of the said invention, it is preferable that the length of the said joining element in the tire circumferential direction is more than the length of the said land element in the tire circumferential direction.

  In the pneumatic tire according to the invention, the length of the land element in the direction perpendicular to the extending direction is 1 mm or more and less than 2 mm, and the groove among the grooves forming the small blocks of the small block group It is preferable that the length of the groove in which the land element is arranged is 2 mm or more in a direction orthogonal to the extending direction of the land element.

Moreover, in the pneumatic tire of the said invention, it is preferable that the average height of the said land element is 1/3 or more and 9/10 or less of the height of the said buttress block.
Here, the height of the land element extending from the joining element of the buttress block toward the joining element of the small block may not be the same height as will be described later. Therefore, the “average height” of the land element referred to here means the average height of the entire land element when the land elements extend at different heights.

  The shape of the surface contour of the small block is preferably a polygonal shape.

  According to the present invention, in order to improve rolling resistance more effectively, even in the case where a small block is arranged in the shoulder region, in particular, in the tire width direction of the small block located in the outermost row in the tire width direction. Since the shear deformation can be reduced, it is possible to provide a pneumatic tire capable of suppressing shoulder wear and step-down wear.

Fig.1 (a) is the partial expanded view which showed the tread pattern of one Embodiment of the pneumatic tire by this invention, FIG.1 (b) is the figure which expanded a part of Fig.1 (a). . FIG. 2A is a cross-sectional view in the tire width direction of an embodiment of a pneumatic tire according to the present invention, and FIG. 2B shows a modification example when the tire of FIG. 2A is loaded. It is a figure. Fig.3 (a) is the figure which expanded the tread pattern of the pneumatic tire shown to Fig.1 (a), Furthermore, FIG.3 (b) is the figure which expanded a part of Fig.3 (a). It is the figure which expanded the tread pattern of one Embodiment of the pneumatic tire by this invention. Fig.5 (a) is the figure which expanded the cross section of the tire width direction of the tread pattern of one Embodiment of the pneumatic tire by this invention. FIG.5 (b) is the figure which expanded the cross section of the tire width direction of the tread pattern of other embodiment of the pneumatic tire by this invention. FIG. 6 is a partial development view showing a tread pattern of still another embodiment of the pneumatic tire according to the present invention. FIG. 6 is a partial development view showing a tread pattern of still another embodiment of the pneumatic tire according to the present invention.

  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 a tire) according to an embodiment of the present invention. In the drawing, the vertical direction indicates the tire circumferential direction (direction parallel to the equator plane C), and the left-right direction indicates the tire width direction (direction orthogonal to the equator plane C).

  2A, the tire according to the embodiment includes a tread portion 21 that forms a tread surface of the tire, and a pair of tread portions 21 connected to both ends in the width direction via a shoulder region and a buttress region. A carcass 8 having a sidewall portion 20 and 20 and extending in a toroidal manner between a pair of left and right bead portions 7 and 7 located on the opposite side of the shoulder region side of the pair of sidewall portions 20 and 20. This is a tire having a tire structure according to the custom, comprising a belt layer 9 disposed on the outer side in the tire radial direction of the crown portion of the carcass 8.

As shown in FIG. 1, when the length between the tread ground contact ends 2 of the tire 1 (tread ground contact width) is TW, symmetrically with respect to the equator plane C, at least 80% of the tread ground contact width TW. A plurality of small blocks that are partitioned by grooves 3a and 3b in the region from the outer side in the tire width direction to the ground contact edge 2 than the range W (hereinafter, this region is referred to as a shoulder region SA in the present invention) are closely packed together. A small block group SGb.
Here, the groove 3a refers to a space in the circumferential direction formed by the small blocks constituting the column, and the groove 3b refers to a groove that intersects the groove 3a. These grooves have such a width that adjacent small blocks are not completely constrained to each other and can be individually moved, and preferably have a width of 0.7 mm to 3 mm.

The surface contour shape of the small block 4 is preferably a polygonal shape. 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 small block independently movable.
Furthermore, the surface contour shape is preferably a regular octagon as shown in FIGS. 1 (a) and 1 (b), for example. 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, by making the surface contour shape a regular octagon, the block falls down in multiple directions and can sufficiently support the adjacent blocks. In addition, when the surface contour shape is a regular octagon, it is preferable that the groove | channel 3a which divides | segments a small block has the 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 groove 3b intersecting with the groove 3a (groove inclined with respect to the equator plane) is preferably 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.
However, the surface contour shape of the small block of the present invention is not necessarily limited to the above shape. In this way, the grooves are partitioned and the individual small blocks are freely independent so that they can have flexibility when grounded without being constrained by the adjacent small blocks (or buttress blocks described later). As long as it can move.

The surface area of the small block 4 is preferably 100 mm ² or more and 1200 mm ² or less.
By subdividing the block so that the ground contact area is in this range, the shear strain on the tread surface can be reduced and the bulging deformation of the block can be reduced. As a result, each block can be moved within an appropriate range so as to be flexible with respect to an impact from the road surface, while shearing of the block can be suppressed.
The reason why the contact area is within this range is that if the area is smaller than 100 mm ² , the contact area of each block is too small to withstand the impact from the road surface, and shearing tends to occur. Further, if it is larger than 1200 mm ² , the surface area of the block becomes too large and the flexibility of the individual blocks is lost.

  As shown in FIGS. 1 (a) and 1 (b), a plurality of columns in which the small blocks 4 are arranged at predetermined intervals in the circumferential direction are arranged in the width direction on the tire surface to form adjacent columns. The small blocks 4 to be arranged are arranged so as to have different phases in the tire circumferential direction. That is, the small 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 where centroids of adjacent small 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 (a), the centroids of the small blocks 4 forming the outermost column in the tire width direction and the second column from the outermost side adjacent to the column are half blocks. The tires are shifted in the tire circumferential direction. Therefore, in this case, when attention is paid to the plurality of small blocks arranged on the tread surface in the tire width direction, the small blocks forming the columns for every other row (every other row) have 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 small blocks having the same phase may not necessarily form columns for every other column, but may form columns every other column.

As described above, the small blocks as described above having a polygonal shape and a small surface area are arranged on the tread surface in a staggered manner, so that each block is flexible. The effect of improving the grounding property for each block and reducing the rolling resistance can be obtained.
The above effect is particularly remarkable in the shoulder region where the shear deformation of the block is most likely to occur. This is because by providing a relatively small small block on the shoulder side in this way, the tread portion in the vicinity of both end portions of the belt layer that is dominant in rolling resistance can be subdivided (that is, the tread portion in the vicinity of the belt end is formed). This is because the energy loss of the tread portion during rolling of the tire load can be significantly reduced.

In addition, since the small blocks 4 are arranged in a zigzag pattern in the tire circumferential direction as described above, it is possible to exert an excellent edge effect by sequentially causing the edges of each small block to act during tire rolling. it can.
Moreover, since the contact timing to the road surface can be shifted between the small blocks 4 adjacent in the tire width direction, pattern noise can also be reduced.

  Further, the tire 1 has a buttress block row BGb on the tire surface on the outer side in the tire width direction (that is, the outer side in the tire width direction of the contact width TW) from the ground contact end 2. This buttress block row BGb is configured by arranging a plurality of buttress blocks 6 extending in the tire circumferential direction from the tread ground contact end to the width direction outward from the inner side in the tire width direction across the tread ground contact end.

Further, as shown in FIG. 1A, the buttress block 6 constitutes a column in the tire width direction inner side adjacent to a column in the outermost side in the tire width direction (that is, a column in the second column from the outermost side in the tire width direction). When one small block among the small blocks 4 is, for example, 4a, it is arranged so that at least a part of the buttress block 6 is positioned on a straight line drawn from the small block 4a to the outside in the tire width direction. .
Here, the width in the tire circumferential direction of the buttress block 6 is the same as the length in the tire circumferential direction of the small block 4, and the diagram of the buttress block 6 is on the straight line extending outward from the centroid of the small block 4 in the tire width direction. It is preferred that the mind is also located.

Further, in the tire 1, in the small block group SGb in the shoulder region SA, the reference pitch length of the small block 4 is PL (mm), the width of the small block group SGb is SAW (mm), and the reference pitch length. The number of small blocks 4 existing in the reference area Z (shaded area in FIG. 3A) of the small block group Gb divided by the length PL and the width SAW is a (number), When the negative rate of N is N (%)
a / (PL × SAW × (1-N / 100))
The block number density S per unit actual ground contact area of the small block group SGb is in the range of 0.003 / mm ² or more and 0.04 / mm ² or less.

  When counting the number of blocks a in the reference zone Z, if the block exists across 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. It is counted using the ratio of the remaining area of the remaining blocks. 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 smallest unit of the repeated pattern of small blocks in one block column constituting the small block group SGb. For example, one small block 4 is represented by the small block. 4 is defined by the grooves 3a and 3b dividing the tire 4, the tire circumferential length of one small block and the tire circumference of one groove 3a adjacent to the small block in the tire circumferential direction. The sum of the direction length is the reference pitch length.

Further, “the width SAW in the tire width direction of the shoulder region SA” refers to the total length in the tire width direction of the small block group SGb in the small size of the small blocks 4 existing in the shoulder region SA. That is, when the length in the tire width direction of the small block group in each of the shoulder regions SA located on both outer sides in the tire width direction is SA1 and SA2, the width SAW is the total width of SA1 + SA2. Means.
For example, in this embodiment shown in FIG. 3, the small block 4 and the buttress block 6 are symmetrically arranged with respect to the equatorial plane C in the area SA from the outer side in the tire width direction to the grounding end 2 than the range W of 80% of the tread grounding width TW. The end is arranged. Accordingly, the tire width direction length SA1 of the small block group existing in the shoulder region SA on one side is the tire width direction length SA1 of the shoulder region SA of the buttress block 6 existing on the inner side in the tire width direction from the ground contact edge 2. The tire width direction length is subtracted. If the tread surface of the tire is symmetrical with respect to the equator plane C, the same applies to SA2, and therefore the width SAW in the tire width direction of the shoulder region SA in the embodiment of FIG. 3 is SA1 * 2. Will mean.

  The “actual ground contact area” of the small block group SGb refers to the total surface area of all small blocks in the reference area of the small block group SGb. In other words, the reference pitch length PL and the width of the small block area SA This is an area obtained by subtracting the areas of the grooves 3a and 3b defining the individual small blocks 4 from the area of the reference area defined by the product with SAW.

  As described above, since the small blocks 4 are densely arranged while securing a sufficient groove area in the small block group SGb, the total edge length and edge direction components (different directions) of the small blocks 4 are adopted. The number of edges facing the surface can be increased, and an excellent edge effect can be exhibited. Further, since the size of the small block 4 is reduced and the sipe is not formed, the grounding property of each small block can be improved and high wet performance can be exhibited. Furthermore, by reducing the size of each small block 4, the distance from the central region of the small block 4 to the peripheral edge of the block can be reduced, so that the water film removal effect by the small block 4 can be improved.

Further, the negative rate N in the small block group SGb is preferably 5% to 50%. When the negative rate N in the small block group SGb is less than 5%, the groove area is too small and the drainage is insufficient, and the size of each block is too large, making it difficult to achieve the required edge effect. Because it becomes. On the other hand, if it exceeds 50%, the ground contact area becomes too small and the steering stability may be lowered. Further, when the number density S of the small blocks 4 in the small block group SGb is less than 0.003 (pieces / mm ² ), it is difficult to realize a high edge effect without forming a sipe. When the number density S exceeds 0.04 (pieces / mm ² ), the small block 4 becomes too small and it is difficult to achieve the required block rigidity.

  However, if the small block 4 is formed only on the tread surface, the small block 4 located in the shoulder region cannot withstand the shearing force caused by the load received from the rim 5 repeated many times. In some cases, there may be a problem that step-down wear occurs. And this time, the applicant has found that among the small blocks located in the shoulder region, in particular, the small blocks constituting the outermost column in the tire width direction in the ground contact region are most susceptible to shear deformation.

  Here, a mechanism in which the tread portion receives a force transmitted from the bead portion when a load is applied to the tire 1 will be described using a tire having the structure shown in FIG. First, when a load is applied to the tire 1 installed on the rim 5, a load is applied from the bead portion 7 to the sidewall portion 20, the buttress region, and the shoulder region in a direction perpendicular to the tread (FIG. 2 (a)). . This vertical force is transmitted as stress to the tread portion 21 in the substantially tire width direction through the shoulder region. When this stress is transmitted, the tread portion 21 receives a force on the inner side in the width direction as shown in FIG. 2B, so that shear deformation occurs in the small block 4 near the road surface (that is, the small block 4 in the shoulder region). Therefore, the deformation of the tread portion 21 when a load is applied to the tire 1 is as shown in FIG.

  Thus, although the small blocks located in the shoulder region are likely to undergo shear deformation in the width direction, among these small blocks, the small block located in the outermost column in the tire width direction of the ground contact surface is the outermost of the ground contact end 2. Because it is located nearby, it is directly stressed. Therefore, the small blocks located in the outermost column in the tire width direction are particularly susceptible to deformation due to stress.

Furthermore, a lateral force in the tire width direction is applied particularly to the small blocks located in the shoulder region of the tread surface not only when the load is applied but also during cornering. And since the small block which comprises the outermost column is arrange | positioned in the position nearest from a grounding end, it is most easy to produce a deformation | transformation also by the presence or absence of the grounding of the tread surface at the time of this cornering.
In addition, there is a groove between the outermost small column in the column and the small inner block in the tire width direction adjacent thereto (that is, the small block constituting the second column from the outermost side). Even when the outermost small block in the outermost column that has received a force falls down, it is difficult to sufficiently transmit the lateral force to the small blocks that form the second column from the adjacent outermost column.

  As described above, when the small blocks 4 are formed on the tire surface, among the small blocks located in the shoulder region, the small blocks constituting the outermost column in the tire width direction are most likely to undergo shear deformation. As a result of repeating this deformation, there arises a problem that shoulder wear and step-down wear occur.

In order to solve the above problem, in the tire 1 of the present invention, a plurality of small blocks constituting a column adjacent to the outermost column in the tire width direction (second column inward from the outermost side in the tire width direction) and A lateral force restricting portion is provided between the small block and a buttress block arranged on a straight line drawn outward in the tire width direction.
According to this characteristic configuration, the force applied from the buttress block to the inner side in the tire width direction can be absorbed by the small block in the second row from the outermost row on the inner side in the width direction from the outermost column. It is possible to reduce the force applied directly to the small blocks in the outermost column in the direction, and to suppress shear deformation of the small blocks.

  Hereinafter, the lateral force restricting portion, which is a feature of the present invention, will be described based on various forms.

  As shown in FIG. 4, the lateral force restricting portion 10 includes a joining element 11 joined to the buttress block 6 at an inner position in the tire width direction of one buttress block, and the joining element 11 at an inner position in the tire width direction. And a land element 12 connected to the ground.

  When a buttress block connected to the land element 12 is located on a straight line drawn from a small block to the outer side in the tire width direction, the end of the land element 12 on the inner side in the tire width direction is a part of the small block. Join. In other words, the lateral force restricting portion 10 is disposed between the blocks of the plurality of small blocks constituting the outermost column L1 in the tire width direction. Each of the small blocks 4b constituting the column L2 in the row is connected to the buttress block 6 positioned on the straight line including the row.

  However, the end portion on the inner side in the width direction of the land element 12 that is a part of the lateral force regulating portion does not always have to be joined to the small block, and there is a groove between the end portion and the small block. May be. That is, the end portion and the small block are usually separated from each other, and when the tire surface is in contact with the road surface due to load or cornering, the end portion and the small block may be formed to contact at least one point. Good.

  In this way, by connecting the small block and the small block and the buttress block positioned on the same straight line in the tire width direction, the small block positioned in the outermost row in the tire width direction by a force from the buttress block toward the ground contact end. It is possible to suppress the deformation of the block as compared with the conventional case. The buttress block does not transmit this stress (lateral force) directly to the small blocks located in the outermost column, but the second row from the outermost row inside the outermost row via the lateral force restricting part. This is because stress (lateral force) can be absorbed into the small blocks.

  For the above reasons, when there is a groove between the end of the land element and the small block, the force is transmitted from the buttress block to the small block arranged in the inner column in the width direction from the outermost column. As described above, the distance between the grooves needs to be a distance such that the land element and the small block are connected when the tire is in contact with the ground.

In this way, the small block connected to the buttress block is a small block constituting the second column from the outermost side in the tire width direction, so that the force applied in the width direction is sufficiently absorbed in the shoulder region, and the width is further increased. The force transmitted in the direction inner direction can be effectively suppressed.
This is because the small blocks constituting the second column from the outermost row in the tire width direction are arranged on the inner side in the width direction than the outermost row, and therefore have a smaller curvature than the outermost row. In other words, the small blocks in the second row from the outermost side can more firmly contact the road surface when the tire contacts the ground, and as a result, the force transmitted from the buttress block can be sufficiently absorbed. Because.

Further, as shown in FIG. 4, when the lateral force regulating portion 10 is viewed in a projection view with respect to the tire surface, the tire circumferential direction length x1 of the joining element 11 on the buttress block side is the tire circumferential direction length of the land element 12. It is formed at a distance of x2 or more.
Here, since the joining element of the buttress block needs to sufficiently transmit the lateral force to the land element, it is preferable that the boundary portion between each block and each joining element has the widest configuration. That is, the tire circumferential direction length of this boundary part should just be more than the tire circumferential direction length of a land element.

Further, the length of the land element in the tire circumferential direction only needs to be long enough to transmit the lateral force without causing collapse when the lateral force is transmitted from the buttress block to the small block. Therefore, although the width of the land element may have the same length as the joining element, in order to prevent the land element from contacting the small blocks constituting the outermost column in the tire width direction, It is preferable that the length is equal to or shorter than the joining element.
Specifically, the circumferential length of the groove in which the land element is formed is 2 mm or more. Therefore, in order to prevent the small block forming the groove from coming into contact with the land element, the length in the direction orthogonal to the extending direction of the land element is 1 mm or more and less than 2 mm. The reason why it is shorter than 1 mm is that if it is made too thin, the land element may collapse at the time of stress transmission. However, the circumferential length of the land element does not need to be the same throughout, and if the thickness is such that the lateral force from the buttress block can be transmitted to the small block, a different circumferential length is required. You may have.

  FIGS. 5A and 5B are arrow views showing a cross section of the tire obtained by cutting the lateral force regulating portion along lines A-A ′ and B-B ′. In this cross section, the average height H in the tire radial direction of the land element 12 which is one of the components of the lateral force regulating portion is 1/3 or more and 9/10 or less of the tire radial direction height of the buttress block or the small block. Preferably, it is 1/2 of the height in the tire radial direction of the buttress block or small block. Therefore, the surface contours of the small block and buttress block remain on the tire surface.

  Thus, if the height of the land element is made lower than the height of the buttress block or the small block, the groove between the blocks is not completely blocked. That is, wet performance can be maintained, and each block can be individually grounded while remaining in an independent state. Therefore, even if the lateral force restricting portion that suppresses the lateral force is provided, the above-described effects of the small block can be sufficiently exhibited.

The average height H in the tire radial direction of the land element 12 is set to 1/3 or more of the tire radial direction height of the buttress block or the small block. This is because it cannot endure and collapse may occur, and the lateral force cannot be sufficiently transmitted from the buttress block to the small block. Further, the land element cannot sufficiently suppress the deformation of the buttress block, and the block may fall down. In addition, the height of 9/10 or less is that if the height is higher than this, the height of the land element and the height of the block become substantially the same height, and the groove between the blocks is blocked by the land element in the tire width direction. Because it will be. That is, the groove provided in the circumferential direction is closed, and the drainage performance is deteriorated.
Therefore, if the average height of the land elements in the tire radial direction is ½ of the height of the block in the tire radial direction, the land elements will not collapse or the blocks will collapse, and the drainage will be maintained. Thus, the lateral force can be sufficiently regulated.

  The above-mentioned average height H of the land element 12 means that the height of the land element extending from the buttress block toward the small block is within the land element as shown in FIGS. 5 (a) and 5 (b). When different, it refers to the average of the radial height of the entire extending land element. That is, it means a value obtained by dividing the area of the land element in the tire cross section by the length of the land element in the tire width direction.

  As described above, when the heights of the land elements are not uniform but different, when the land elements and the small blocks are connected in advance, the center portion of the land elements is the lowest as shown in FIG. Can be formed. That is, among the land elements, the portion closer to the buttress block and the small block has a higher height and can be formed to gradually decrease toward the center of the land element in the tire width direction. By adopting this shape, the connection between the land element and each block can be strengthened, and the lateral force can be effectively transmitted from the buttress block to the small block. Moreover, since the height of the center part of a land element is low, drainage can also be ensured.

  Further, when the land element and the small block are separated from each other and are joined at the time of tire contact, as shown in FIG. 5 (b), the end of the land element in the width direction from the joint element on the buttress block side It can form so that it may decrease gradually toward. By adopting this shape, even when the buttress block collapses somewhat and the end of the land element and the small block are joined when the tire contacts the ground, the height of the land element at the joint with the small block is low. Also, stress can be transmitted and sufficient drainage can be secured.

  In addition, what is necessary is just to form this side force control part 10 by a normal method using a metal mold | die etc. so that it may have the said shape at the time of vulcanization in a tire formation process. Therefore, in this specification, for the sake of explanation, the lateral force restricting portion is described separately from the joining element and the land element. However, the lateral force restricting portion can be formed integrally with the block. It should be noted.

  Further, in the embodiment shown in FIG. 1, the small blocks 4 are illustrated so as to be arranged over the entire contact width TW, but the small blocks 4 are at least outside in the tire width direction of the range W (that is, shoulders). Area SA) and the inner side in the tire width direction from the tread grounding end 2 may be disposed. Therefore, as shown in FIG. 6, the tire according to the present invention can have a tread pattern in which, for example, the small block 4 is provided in the shoulder region SA, and the main groove is provided in the tread portion on the inner side in the tire width direction. In addition, although not shown here, for example, a small block 4 is provided at least in the shoulder region SA, and a tread portion on the inner side in the tire width direction is provided with a rib or a block pattern partitioned by main grooves, lateral grooves, sipes, and the like. It can also be provided.

  In the embodiment shown in FIG. 1, the circumferential lengths of the small block 4 and the buttress block 6 are equal. For example, as shown in FIG. 7, two rows correspond to one buttress block. The buttress block can also be arranged so that the length in the circumferential direction is equal to (the total distance between the two small blocks and the groove between the small blocks is the circumferential distance of one buttress block).

  As described above, the shapes, arrangements, and the like of the small blocks and buttress blocks described above are only examples for explaining the present invention, and the shapes thereof can be appropriately changed without departing from the spirit of the present invention. is there.

  According to the present invention, even when a small block is arranged in the shoulder region, deformation is particularly likely to occur by transmitting stress (lateral force) to the small block on the inner side in the width direction from the outermost column in the tire width direction. It was possible to suppress the shear deformation in the width direction of the small blocks located in the outermost column in the tire width direction, and to suppress the shoulder fall wear and the step-down wear.

DESCRIPTION OF SYMBOLS 1 Tire 2 Grounding end 3a, 3b Groove 4 Small block 5 Rim 6 Buttress block 7 Bead part 8 Carcass 9 Belt layer 10 Lateral force control part 11 Joining element 12 Land element SGb Small block group BGb Buttress block row SA Shoulder area

Claims (5)

Provided within the tread contact width is a small block group in which a plurality of small blocks partitioned by grooves are arranged in a plurality of columns and a plurality of rows, and across the tread contact end on the outer side in the tire width direction of the small blocks. In a pneumatic tire provided with a buttress block row consisting of extending buttress blocks,
Both regions outside the position corresponding to 80% of the tread contact width with respect to the tire equatorial plane as a shoulder region are shoulder regions, and at least a part of the small blocks constituting the small block group in the shoulder region. And place
The columns are arranged so that the small blocks constituting the adjacent columns have different phases in the tire circumferential direction,
In the shoulder region, a reference pitch length of the small block group is PL (mm), a width of the small block group is SAW (mm), and the small blocks are divided by the reference pitch length PL and the width SAW. When the number of the small blocks existing in the reference area of the group is a (pieces) and the negative rate in the reference area is N (%),
a / (PL × SAW × (1-N / 100))
The block number density S per unit actual contact area of the small block group given by is in the range of 0.003 / mm ² or more and 0.04 / mm ² or less,
A lateral force restricting portion constituted by a joining element joined to the buttress block and a land element connected to the joining element and extending inward in the tire width direction between the small blocks constituting the outermost column in the tire width direction. Prepared,
The pneumatic tire characterized in that the land element and a small block adjacent to the inner side in the tire width direction of the outermost small block in the tire width direction are joined at least at the time of tread contact.   The pneumatic tire according to claim 1, wherein a length of the joining element in the tire circumferential direction is equal to or greater than a length of the land element in the tire circumferential direction. The length of the land element in the direction perpendicular to the extending direction is 1 mm or more and less than 2 mm,
The length of the groove in which the land element is arranged among the grooves forming the small blocks of the small block group is 2 mm or more in a direction orthogonal to the extending direction of the land element. The pneumatic tire according to 1 or 2.   The pneumatic tire according to any one of claims 1 to 3, wherein an average height of the land element is not less than 1/3 and not more than 9/10 of a height of the buttress block.   The pneumatic tire according to any one of claims 1 to 4, wherein the shape of the surface contour of the small block is a polygonal shape.

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