JP2011189858A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of restraining partial wear by uniforming shearing force in a grounding surface, by taking into consideration load force different in response to an arranging position of a small block, while maintaining excellent rolling resistance by the small block. <P>SOLUTION: A small block group formed by arranging a plurality of small blocks partitioned-formed by a groove in a plurality of longitudinal rows and a plurality of lateral rows, is arranged in a tread grounding width. A buttress block row formed by arranging a buttress block extending by straddling the tread grounding end in the circumferential direction, is arranged outside in the tire width direction of the small block. In a shoulder area, a land part in the buttress block circumferential direction for connecting the buttress block adjacent in the circumferential direction, is arranged in at least one buttress block row. <P>COPYRIGHT: (C)2011,JPO&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 blocks in the tire width direction. The present invention relates to a pneumatic tire provided with a buttress block array in which buttress blocks extending across the ends are arranged in the circumferential direction.

  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 the 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 side portion extending from the bead portion to the tire radial direction, It is known that the energy consumed in the tread portion is the largest when the energy consumed in the tread portion located across both side portions is compared.

  On the other hand, in Patent Document 1, when a tire rotates and enters a contact area, a shoulder region (a width direction outer side region of the tread portion) and a buttress region (a side wall and a shoulder that continue further outward in the width direction) of the tread portion. In the region between the regions), an expansion deformation extending in the circumferential direction and a compression deformation including bending to push the block in the shoulder region in the direction of the equatorial plane of the tire occur, and the loss due to this deformation is It is disclosed that the rolling resistance of the tire is greatly affected. And in the tire of patent document 1, in order to reduce the rolling resistance of a tire by relieving the shear distortion by the deformation | transformation of this circumferential direction and the width direction, in the tire width direction from the ground contact edge of each block in the block row | line | column of a shoulder area | region The structure which provides a sipe in the outer part is employ | adopted.

JP-A-7-228106

  As described above, in the invention of Patent Document 1, a sipe is formed on the outer side in the tire width direction with respect to the tread ground contact end, thereby trying to relieve the circumferential and width shearing forces input to the tread portion. However, since the rolling resistance of the tire is mainly caused by a hysteresis loss caused by the deformation of the tread portion at the time of rolling of the tire, further realization of the rolling resistance is required as the performance of automobiles in recent years increases. .

  The applicant, as shown in FIG. 1, provides the tire rolling resistance more than before by providing a block group in which a plurality of small blocks partitioned by grooves are densely arranged in at least the shoulder region of the tread portion. It has been found that it can be effectively reduced. In conventional tires, the rigidity of the block was high, and the block could not move flexibly according to the contact point, but if multiple small blocks were provided in the tread as described above, the block tire at the time of contact This is because the ground contact area between the tread surface and the road surface is subdivided as compared with the prior art, so that each block can be independently moved, and flexibility at the time of ground contact can be provided. And the effect by formation of such a small block is especially remarkable in the shoulder area | region which has a large curvature and is easy to receive the shear force of the circumferential direction and the width direction.

  On the other hand, since the tire outer diameter length of the center region is longer than the tire outer diameter length of the shoulder region when viewed in the width direction around the tire equatorial plane, the tire is positioned in the center region and the shoulder region at the time of tire contact. There is a problem that the shearing force to the block to be made becomes uneven. That is, when a plurality of such small blocks are formed, the shear force between the small block located in the center region and the small block located in the shoulder region becomes uneven, resulting in uneven wear particularly in the shoulder region. There is a problem of end.

  As a solution to the above problem, it is considered to provide a connecting part (tie bar) between the blocks in order to improve the non-uniform shear force and suppress uneven wear by increasing the rigidity of the subdivided blocks again. It is done. However, the inadvertent connection between the blocks, in turn, reduces the effect of the small blocks, each of which is independently movable and flexible, and it becomes impossible to obtain good rolling resistance. .

  Therefore, even when a small block is arranged at least in the shoulder region within the tread contact width, the present invention maintains a good rolling resistance by the small block and further varies depending on the arrangement position of the small block. It is an object of the present invention to provide a pneumatic tire that can suppress uneven wear by making the shearing force in the ground contact surface uniform by connecting the blocks in consideration of the load force.

  In order to achieve the above-mentioned object, the inventor has conducted extensive research on the arrangement of the connecting portions between the blocks of the tread portion, and the tire outer diameter length in the center region is longer than the outer tire length in the shoulder region. Due to the existence of the difference, it has been found that a force in the driving direction mainly acts in the center region and a force in the braking direction mainly acts in the shoulder region when the tire is driven. And even if it is a case where a connection part is provided between blocks based on this knowledge, while maintaining good rolling resistance without reducing the effect by a small block, between blocks which can control uneven wear It has been found that the following configuration is effective as the arrangement configuration of the connecting portion.

That is, the pneumatic tire according to the present invention 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 array in which extending buttress blocks are arranged in the circumferential direction,
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 phases in the tire circumferential direction of the small blocks constituting the adjacent columns are different from each other,
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,
In the shoulder region, a pneumatic tire is characterized in that at least one buttress block row includes a buttress block circumferential land portion that connects buttress blocks adjacent in the circumferential direction.

  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” refers to the minimum unit of the repeated pattern of the small blocks in one column constituting the small block group in the shoulder region. For example, one small block and its small block When the repeating pattern of the pattern is defined by the grooves defining the small blocks, the tire circumferential length for one small block and the tire circumferential length for one groove adjacent to the small block in the tire circumferential direction Is added as the reference pitch length of the small block.

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

  The “actual ground contact area” of the small block group refers to the total surface area of all small blocks in the reference area of the small block group, and is defined by, for example, the product of the reference pitch length PL and the width SAW. , Refers to the area obtained by subtracting the area of the groove defining each small block from the area of the reference area.

In the pneumatic tire according to the present invention, a small block circumferential land portion that connects small blocks adjacent to each other in the tire circumferential direction is disposed between the small blocks constituting the column, and the buttress block circumferential land portion is disposed. And when the said small block circumferential direction land part is made into the tread circumferential direction land part, it is preferable that the volume of the said tread circumferential direction land part is larger in the tread circumferential direction land part located in the tire width direction outer side.
Here, the small block circumferential land portion may be arranged, for example, between the small blocks constituting the outermost column in the tire width direction, or configure the second column from the outermost side, and further the third column You may arrange | position between the small blocks to perform. Further, the small block circumferential land portion may be arranged between any number of columns of small blocks or between all columns of small blocks.

Moreover, it is preferable to arrange | position the width direction land part which connects the blocks which adjoin the tire width direction between the blocks which comprise the said buttress block row | line | column and the said small block row | line | column.
Here, between the blocks constituting the adjacent block row is the width direction groove between the buttress block row and the outermost small block row in the tire width direction, and between the small blocks having different phases in the tire circumferential direction. This is the width direction groove.

The average height of the land portion in the circumferential direction of the buttress block is preferably 1/3 or more and 9/10 or less of the height of the buttress block.
The height of the circumferential land portion may not be constant in the tire width direction, as will be described later. Accordingly, the “average height” of the circumferential land portion of the buttress block referred to here means an average value of different heights of the entire circumferential land portion of the buttress block.

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

Still further, the pneumatic tire according to the present invention has a direction to be mounted on the vehicle, and the buttress block having the buttress block circumferential land portion has a vehicle inner side centered on the tire equatorial plane when the vehicle is mounted. It is preferable to be located at.
Here, “the direction of mounting on the vehicle is determined” means that an indicator such as a character, a figure, or a pattern indicating the mounting direction on the vehicle is attached to the user on the outer surface of the tire. Say that.

  According to the present invention, even when a small block is arranged at least in the shoulder region, the shear force in the tread contact surface can be made uniform while maintaining good rolling resistance due to the small block. A pneumatic tire capable of suppressing uneven wear in the shoulder portion can be provided.

Fig.1 (a) is the partial expanded view which showed the tread pattern of one Embodiment of the pneumatic tire according to this invention, FIG.1 (b) is the figure which expanded a part of Fig.1 (a). . It is sectional drawing of the tire width direction of one Embodiment of the pneumatic tire according to this invention. Fig.3 (a) is an enlarged view of the right half part of the pneumatic tire shown to Fig.1 (a), Furthermore, FIG.3 (b) is the figure which expanded a part of Fig.3 (a). 4A is an enlarged view of the tread pattern of the embodiment of the pneumatic tire shown in FIG. 1A, and FIG. 4B is a line AA ′ in FIG. 4A. It is an arrow line view cut | disconnected along. It is a figure which shows the tread pattern of other embodiment of the pneumatic tire according to this invention. Fig.5 (a) is the figure which expanded the tread pattern, FIG.5 (b) is a schematic diagram of the tire width direction cross section of each tread circumferential direction land part and buttress block in Fig.5 (a). It is a figure which shows the tread pattern of further another embodiment of the pneumatic tire according to this invention. (A) And (b) is a figure which shows the tread pattern of further another embodiment of the pneumatic tire of the mounting direction designation | designated according to this invention, respectively.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a partial development view showing a tread pattern of a pneumatic tire 1 (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).

  FIG. 2 is a cross-sectional view of the tire 1 of this embodiment in the tire width direction. As shown in FIG. 2, the tire 1 includes a tread portion 21 that forms a tread surface of the tire, and a pair of sidewall portions 20 and 20 that are connected to both ends in the width direction of the tread portion 21 via shoulder regions. Further, a carcass 8 extending in a toroidal shape between a pair of left and right bead portions 7, 7 located on the opposite side of the pair of sidewall portions 20, 20 from the shoulder region side, and a tire of a crown portion of the carcass 8 It is a tire having a tire structure according to a custom, including a belt layer 9 disposed on the radially outer side.

As shown in FIG. 1A, when the length between the tread grounding ends 2 and 2 (tread grounding width) of the tire 1 is TW, at least the tread grounding width is symmetrical with respect to the equator plane C. A plurality of small areas defined by a groove 3a and a groove 3a in a region from the outer side in the tire width direction to the ground contact edge 2 than the range W of 80% of TW (hereinafter, this region is referred to as a shoulder region SA in the present invention). It has a small block group SGb in which the blocks 4 are densely packed together.
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.

  In FIG. 1A, the small block 4 is illustrated so as to be disposed over substantially the entire tread contact width TW. However, the small block 4 has at least a range W (centered on the tire equator plane, It may be arranged symmetrically in the tire width direction outer side (that is, the shoulder region SA) of the tread contact width TW and the inner side of the tread contact end 2 in the tire width direction. Therefore, although not shown here, for example, a small block 4 is provided in the shoulder region SA, and a tread pattern in which a main groove is provided in the tread portion on the inner side in the tire width direction, or at least the small block 4 is provided in the shoulder region SA, Ribs and block patterns defined by main grooves, lateral grooves, sipes, and the like may be provided in the tread portion on the inner side in the tire width direction.

  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.

  Further, the tire 1 has a buttress block row BGb on the tire surface in the tire width direction outer side from the contact end 2 (that is, the tire width direction outer side of the contact width TW). In this buttress block row BGb, a plurality of buttress blocks 6 are arranged in the tire circumferential direction, extending from the inner side in the tire width direction to the tread grounding end 2 and partially extending in the shoulder region SA and extending outward in the width direction. Is made up of.

  1 (a) and 1 (b), the tire circumferential direction length of the buttress block 6 is the same as the tire circumferential direction length of the small block 4, and the small blocks in the second row from the outermost side in the tire width direction are shown. Although the centroid of the buttress block 6 is located on a straight line drawn from the centroid of 4 outward in the width direction, the centroid is not necessarily limited to this embodiment. For example, the buttress block 6 is formed so that two rows of small blocks have a circumferential width of one row of buttress blocks (two small blocks are the circumferential distance of one buttress block). May be.

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 Gb 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. When the pattern repeat pattern is defined by the grooves 3a and 3b that divide 4, the tire circumferential direction length of one small block and the tire circumferential direction of one groove 3a adjacent to the tire circumferential direction of this small block The reference pitch length is obtained by adding the length.

Further, “the width SAW in the tire width direction of the shoulder region SA” refers to the sum of the lengths in the tire width direction of the small block groups that are arranged in the shoulder region SA and in which the small blocks 4 are densely arranged. That is, the length in the tire width direction of the small block group in each of the shoulder areas SA located on both outer sides in the tire width direction is SA1 (the shoulder area on the right half of the equator plane C shown in FIG. 1A). , SA2 (the shoulder region on the left half of the equatorial plane C shown in FIG. 1A), the width SAW means the sum of SA1 + SA2.
For example, in the embodiment of FIG. 3 (a) showing the right half of FIG. 1 (a), the ground contact end from the outer side in the tire width direction is more symmetrical with respect to the equator plane C than the range W of 80% of the tread ground contact width TW. The end portions of the small block 4 and the buttress block 6 are arranged in the area SA up to 2, but the tire width direction length SA1 of the small block group is one side from the end portion of the right half of the range W in the tire width direction. This means the length of the small block existing in the shoulder region SA to the outermost side in the tire width direction. If the tread pattern of this 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 FIGS. 3 (a) and 3 (b). Means SA1 * 2.

  The “actual ground contact area” of the small block group SGb refers to the total surface area of all the small blocks in the reference area of the small block group SGb. For example, the reference pitch length PL and the width SAW of the shoulder region SA Can be obtained from the area obtained by subtracting the areas of the grooves 3a and 3b partitioning the individual small blocks 4 from the area of the reference area defined by the product of

In this way, the small blocks are made densely arranged after reducing the size of the blocks, so that the grounding performance of each small block can be improved and each block can be moved flexibly. Therefore, an effect of reducing rolling resistance can be achieved.
This effect is particularly remarkable in the shoulder region where the shear deformation of the block is most likely to occur. Therefore, it is preferable that the small block group is provided at least in the shoulder region. This is because by providing such a relatively small small block on the shoulder side, the tread portion in the vicinity of both end portions of the belt layer 9 that is dominant in rolling resistance can be subdivided (that is, the tread portion in the vicinity of the belt end). This is because the energy loss of the tread portion at the time of tire load rolling can be significantly reduced.

In addition, the block number density S per unit actual ground contact area of the small block group Gb is preferably in the range of 0.003 / mm ^{2 to} 0.04 / mm ² . When the number density S of small blocks is less than 0.003 (pieces / mm ² ), it is difficult to realize a high edge effect without forming a sipe, while the number density S of small blocks is 0.04 (pieces). / Mm ² ), the small block becomes too small, and it is difficult to achieve a desired block rigidity.

Incidentally, the surface area of the small blocks 4 is preferably 100 mm ² or more 1200 mm ² or less in size. 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.

  However, only by forming the small block on the tread surface in this way, in particular, the small block located in the shoulder region having a small outer diameter is subjected to friction caused by repeated rotation, resulting in uneven wear. Problems arise.

Here, the mechanism that uneven wear is likely to occur especially in the shoulder region block due to the presence of the tire diameter difference will be described.
In the cross section in the tire width direction, the diameter R ′ of the shoulder region is usually smaller than the diameter R of the center region. Therefore, comparing the travel distance of the blocks arranged in each region when the tire makes one revolution, a difference of 2π (R−R ′) is generated in the travel distance of the blocks in both regions. Here, the angular velocities of rotation of the tires are the same in both regions, while the whole tire tries to move at the same tangential speed in the contact surface. In other words, the block in the shoulder region where the tangential speed is slow proceeds while being dragged toward the traveling direction of the center region where the tangential speed is fast. As a result, the block of the shoulder region having a small diameter is subjected to slippage in the traveling direction and a circumferential shear force (control force) opposite to the traveling direction, so that the wear energy increases. Will occur.

  Therefore, in order to solve the above problem, in the tire 1 according to the present invention having a plurality of small blocks, in the shoulder region, at least one buttress block row is connected to at least one buttress block circumferentially adjacent buttress blocks. It is characterized by arranging directional land.

  Below, the tire according to this invention provided with the buttress block circumferential direction land part provided in the shoulder area | region and between the buttress blocks adjacent to the circumferential direction first is demonstrated based on various forms.

  FIG. 4 is a view showing an embodiment of a tire according to the present invention. As shown in FIG. 4A, the buttress block circumferential land portion 10 is provided at least between the adjacent buttress blocks 6 constituting the buttress block row BGb and in the shoulder region SA. Here, in the tread pattern development view of FIG. 4A, the buttress block circumferential land portion 10 is shown in black, but this is for clarity and the actual color is not different from the buttress block 6. . The same applies to other drawings.

  In this way, if buttress blocks adjacent in the circumferential direction are connected to each other by a land portion in the shoulder region, due to the difference in diameter, a circumferential shear force (in the braking direction) in which the block located in the shoulder region is opposite to the traveling direction. This is because the blocks are connected to each other in the circumferential direction even when subjected to (force), and this land portion is supported and prevents the blocks from being bent too much. Moreover, it is because a shear force can be transmitted to an adjacent block via this land part, and a force can be disperse | distributed. Thus, by increasing the rigidity of the buttress block in the shoulder region, it is possible to more effectively suppress the occurrence of uneven wear than in the past.

FIG. 4B is an arrow view of the buttress block 6 of FIG. 4A cut along the line AA ′. The average height H in the tire radial direction of the land portion in the circumferential direction of the buttress block is shown in FIG. Is not less than 1/3 and not more than 9/10 of the height in the tire radial direction of the buttress block, and preferably 1/2 of the height in the tire radial direction of the buttress block. Therefore, the surface contour of the buttress block remains on the tire surface.
Here, as shown in FIG.4 (b), the height of the buttress block circumferential direction land part arrange | positioned between buttress blocks may differ in a land part. Therefore, when the height of the buttress block circumferential land portion extending between the blocks is different in the land portion, the average height of the buttress block circumferential land portion is averaged of the different heights. Say the value. That is, it means a value obtained by dividing the area of the circumferential land portion of the buttress block in the circumferential section of the tire by the circumferential length of the circumferential land portion.

  As described above, if the height in the tire radial direction of the circumferential portion of the buttress block in the tire radial direction is made lower than the height of the buttress block, the groove between the blocks is not completely closed. That is, wet performance can be maintained, and each block can be individually grounded while remaining in an independent state.

The average height H in the tire radial direction of the buttress block circumferential land is set to 1/3 or more of the tire radial height of the buttress block. This is because the force cannot be withstood and collapse may occur, and the force cannot be sufficiently transmitted between the blocks. Further, the circumferential land portion cannot support the deformation of the block, and the block may fall down.
Moreover, the height of 9/10 or less is that if the height is higher than this, the height of the circumferential land portion and the height of the block become substantially the same height, and the groove between the blocks is the tire in the circumferential land portion. It is because it will block in the circumferential direction. In other words, the groove provided in the width direction is closed by the circumferential land portion, and the drainage performance is deteriorated.
Therefore, if the average height in the tire radial direction of the buttress block circumferential land portion is ½ of the tire radial direction height of the buttress block, the circumferential land portion collapses and the block collapses, and it is good. With the excellent drainage maintained, the load force in the braking direction applied to the block located in the shoulder region can be suppressed as compared with the conventional case.

  Further, when the height of the buttress block circumferential land portion is not uniform and is different, it is preferable to form the center portion of the circumferential land portion to be the lowest as shown in FIG. 4B, for example. That is, it is preferable to form the circumferential land portion so that the portion closer to the block has a higher height and gradually decreases toward the center in the tire circumferential direction of the circumferential land portion. By adopting this shape, the connection between the buttress block circumferential land portion and each buttress block can be strengthened, and the force applied in the circumferential direction can be effectively transmitted from the block to the block. And since the height of the center part of the circumferential direction land part is low, drainage can also be ensured.

Also, here, the buttress block circumferential land portion extending in the tire circumferential direction is preferably configured such that the boundary between each buttress block and each buttress block circumferential land portion is widest in the tire width direction. . That is, it is preferable that the tire width direction length in the boundary portion is equal to or greater than the tire width direction length in the circumferential center portion of the circumferential land portion.
Specifically, the length of the buttress block circumferential land portion in the tire width direction is 10 mm or more and less than 40 mm. The reason why the length is shorter than 40 mm is that if the length is longer than this, buttress blocks are firmly connected to each other and cannot be freely moved by individual blocks. This is because if the length in the tire width direction of the directional land portion is shortened, the land portion may collapse.

In addition, what is necessary is just to form a buttress block circumferential direction land part by a normal method using a metal mold | die etc. so that it may have the said shape at the time of vulcanization | cure in a tire shaping | molding process. Therefore, in this specification, the buttress block circumferential land portion and the buttress block are distinguished from each other for explanation, but the buttress block circumferential land portion can also be formed integrally with the block. It should be noted.
Moreover, although the height and shape of the buttress block circumferential land portion provided in the buttress block have been described here, such a configuration is described in detail below in the small block circumferential land portion and width direction land portion provided in the small block. Is also applicable.

FIG. 5 is a view showing another embodiment of the tire according to the present invention. In the example shown in FIG. 5, in addition to the configuration in which the circumferential land portion is arranged between the buttress blocks shown in FIG. 4, as the land portion that connects the small blocks to each other between the small blocks adjacent in the tire circumferential direction, A small block circumferential land portion 11 is arranged. The small block circumferential land portion 11 may be disposed, for example, between the small blocks adjacent in the circumferential direction constituting the outermost column L1 in the tire width direction, the second row L2 from the outermost side, and further here Although not shown in the figure, they may be arranged between the circumferentially adjacent small blocks 4 constituting the third column L3.
By connecting not only the buttress block row but also the small block column consisting of small blocks in the circumferential direction by the circumferential land portion, even if a circumferential shear force opposite to the traveling direction is applied, these circumferential land The block is supported, and the block in the shoulder region can have an appropriate block rigidity without being bent too much. Further, since not only the buttress block row but also the small block row can transmit the force between the blocks adjacent in the circumferential direction, the shear force can be more effectively distributed.

In addition, although it is preferable to arrange | position this small block circumferential direction land part 11 between the small blocks which adjoin the circumferential direction which comprises the column in a shoulder area | region, the circumference | surroundings which comprise any several rows of the column in a tread area | region are comprised. You may arrange | position between the small blocks adjacent to a direction.
The reason why it is preferable to place the small block circumferential land portion in the shoulder region is that, as described above, the shearing force in the braking direction is applied particularly to the block in the shoulder region due to the diameter difference. This is because if the circumferential land portion is arranged with respect to the block located in the region, the shear force directly received by each block can be reduced, and the occurrence of uneven wear can be more effectively suppressed.
Further, in FIG. 5, the small block circumferential land portion 11 is shown in black, but as described in the buttress block circumferential land portion 10 in FIG. 4, for the sake of clarity, the actual color is the buttress. Same as block 6.

  When the circumferential land portions between the buttress blocks 6 and the small blocks 4 arranged across the plurality of rows are compared, as shown in FIG. 5, the circumferential land portions located on the outer side in the tire width direction. Is formed so as to have a larger volume.

Here, “the circumferential land portion located on the outer side in the tire width direction has a larger volume” means that, for example, as shown in FIG. The width direction length of the circumferential direction land part located outside means the state where it is longer than the width direction length of the circumferential direction land part located inside the tire width direction. That is, when the buttress block circumferential land portion 10 and the small block circumferential land portion 11 are compared, the length in the width direction of the buttress block circumferential land portion 10 is always longer. Are compared, it is the state where the width direction length of the small block circumferential direction land portion 11 becomes longer as it is located on the outer side in the tire width direction.
Further, for example, as shown in FIG. 5B, when viewed in a tire radial cross section, the circumferential height of the circumferential land portion located on the outer side in the tire width direction is the circumferential direction located on the inner side in the tire width direction. A state that is higher than the radial height of the land. That is, when comparing the buttress block circumferential land and the small block circumferential land, the radial height of the buttress block circumferential land is always higher, and the small block circumferential land is compared with each other The state where the radial direction height of a small block circumferential direction land part is so high that it is located in the tire width direction outer side is said.

  As described above, the reason why the volume in the circumferential land portion provided in the outer block in the tire width direction is larger is that the block closer to the ground end has a larger curvature and smaller outer diameter. It is easy to receive a strong circumferential shear force in the braking direction, and uneven wear tends to occur. Therefore, by providing a larger number of circumferential land portions that reduce the shear force in the circumferential direction directly received by the individual blocks with respect to the blocks on the outer side in the tire width direction, the occurrence of uneven wear in the shoulder region is more effectively achieved. This is because it can be relaxed.

  In addition, as a configuration for increasing the volume of the land portion on the outer side in the tire width direction, as described above, it is possible to adjust either the length in the width direction or the height in the radial direction. Both the length and the height in the radial direction may be configured to be longer and higher as the land portion on the outer side in the width direction. However, even if the circumferential land portion located on the outer side in the tire width direction is configured to have a larger volume as a result, the land portion on the outer side in the tire width direction is longer in the width direction, but on the outer side in the tire width direction. When the radial land height is lower as the circumferential land portion is located, or conversely, the radial land height is higher as the circumferential land portion located at the outer side in the tire width direction, while the land portion outside the tire width direction is as a width direction. Is short, it cannot be said that “the circumferential land portion located on the outer side in the tire width direction has a larger volume”.

FIG. 6 is a view showing still another embodiment of the tire according to the present invention. In the example shown in FIG. 6, as shown in FIGS. 4 and 5, a circumferential land portion (buttress block circumferential land portion 10, small block) between blocks (buttress block 6, small block 4) adjacent in the tire circumferential direction. In addition to the configuration in which the block circumferential land portion 11) is disposed, a width direction land portion 12 for connecting small blocks adjacent to each other in the tire width direction is disposed in the center region CA. In the example illustrated in FIG. 6, the width-direction land portion 12 includes, for example, a small block 4a that forms a column L3 of small blocks passing through the equator plane C, and a column L4 that is adjacent to the column L3 and the small block 4a. Are arranged between the small blocks 4b adjacent to each other in the width direction so that the phases are different by half a block, and the small blocks 4a and 4b are connected.
Here, the center area CA refers to an area up to a position corresponding to 25% of the tread contact width with the tire equatorial plane C as the center. Therefore, in the example of FIG. 6, only the small blocks adjacent to each other in the width direction (for example, the small blocks 4 a and the small blocks 4 b) constituting the small block columns L <b> 3 and L <b> 4 are connected by the width direction land portion 12. However, as long as it is within the center region, the small blocks adjacent in the width direction may be connected to each other in other columns as necessary.

  Considering the force in the tire width direction, if a load is applied to the tire installed on the rim, a load from the width direction is applied from the rim to the sidewall portion, from the sidewall portion to the shoulder region, and the center region. Therefore, as shown in FIG. 6, the block deformation by the stress transmitted from the width direction side can be suppressed by connecting the small block in the center region with the width direction land portion 12. Further, when the small blocks are connected to each other in the width direction by the width direction land portion 12, the block rigidity when the tire turns at the time of rolling effectively increases, so that the steering stability of the entire tire can be improved.

  Further, as described above, the shoulder region block having a small diameter is dragged to the center region having a large diameter and receives a force (braking force) in the direction opposite to the traveling direction due to the presence of the diameter difference. On the other hand, the block in the center region having a large diameter receives a force (driving force) in the traveling direction by this reaction. Thus, due to the difference in force mainly received by the shoulder region and the center region, the balance of the wear amount is lost, and uneven wear may occur in the width direction. Accordingly, as in the embodiment shown in FIG. 6, the circumferential land portions (the buttress block circumferential land portion 10 and the small block circumferential land portion 11) are provided in the shoulder region SA, while the width region land is formed in the center region CA. By adopting a configuration in which the portion 12 is provided, various shear forces in the tread ground surface can be made uniform, and uneven wear of the entire tread portion can be suppressed.

  FIGS. 7A and 7B are views showing still another embodiment of the tire according to the present invention. The tire according to this embodiment is an asymmetric pattern tire in which the mounting direction is designated such that the arrow direction shown in FIG. 7 is the inside when each tire vehicle is mounted. That is, in the tire of FIG. 7A, the buttress block circumferential land portions 10 and 10 are arranged on both sides, but the buttress block circumferential land portion side that is formed longer in the width direction is mounted when the tire is mounted. Used inside the vehicle. The tire of FIG. 7B is used such that the buttress block circumferential land portion 10 is disposed only on one side, and the side having the buttress block circumferential land portion 10 is inside the vehicle when mounted. And these tires are used in the state of a negative camber so that it may incline to the vehicle inner side when it is mounted.

  In the case of the negative camber, generally, the bending of the block portion on the inclined side on the inner side of the mounting becomes larger, and the contact length of the block portion becomes longer than the contact length of the block portion on the outer side of the mounting. As a result, the force in the braking direction applied to the block on the inner side of the mounting increases more than the force in the braking direction applied to the block on the outer side of the mounting, and as a result, uneven wear in the block on the inner side of the mounting is likely to occur. Therefore, if a circumferential land portion is provided for the inner block to which more force in the braking direction is applied, and blocks adjacent in the circumferential direction are connected to each other, the forces applied to the individual blocks are dispersed and uneven wear occurs. Can be suppressed.

In the embodiment shown in FIG. 7 (a), buttress block circumferential land portions 10a and 10b are provided on both the inner and outer sides of the mounting. However, the buttress block circumferential land portion 10a on the inner side is mounted in the width direction. It is configured to be long. Moreover, when the tread circumferential direction land part (the buttress block circumferential direction land part 10 and the small block circumferential direction land part 11) is provided over several block row | line like FIG. In each, the width direction length of the circumferential land portion of each block row is preferably shortened from the outer side in the tire width direction toward the equator plane.
As described above, the inner side of the mounting receives more force in the braking direction than the outer side of the mounting. Therefore, in consideration of the load amount of this force, the block is prevented from being bent excessively by forming the volume of the circumferential land portion larger toward the mounting inner side as in the embodiment shown in FIG. It is possible to distribute the force more evenly between the blocks to be performed.
In this embodiment, the example of adjusting the length in the width direction is shown as an example in which the volume is increased toward the inner side of the mounting. However, it can be realized by adjusting the height in the radial direction as a matter of course.

  In the embodiment shown in FIG. 7 (b), tread circumferential land portions (buttress block circumferential land portion 10 and small block circumferential land portion 11) are arranged on the inner side of the mounting. The portion 12 is arranged. The reason for this configuration is that it receives mainly the force in the braking direction on the inner side of the mounting, and suppresses this force, while on the outer side of the mounting, mainly receives the lateral force generated from the side when turning the vehicle. This is to suppress block deformation due to the lateral force. According to such a configuration, it is possible to arrange land portions suitable for each region so as to reduce the load of the force in consideration of the direction of the force mainly applied to each region.

  As described above, by arranging the buttress block circumferential land portion, small block circumferential land portion, and width direction land portion, the small block is formed on the tread surface and the rolling resistance is maintained, particularly in the shoulder region. It is possible to suppress the occurrence of easy uneven wear.

In addition, as for the surface outline shape of the small block 4 arrange | positioned at a tread part, polygonal shape is preferable. 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.
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, when the surface contour shape is a regular octagon, the block falls 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 circumferential direction distance to such an extent that a groove | channel does not block | close between adjacent blocks at the time of grounding. In contrast, the groove 3b that intersects the groove 3a and inclines with respect to the equator plane is preferably formed such that adjacent blocks are close to each other so 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.

  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.

  In addition, arrangement | positioning of the circumferential direction land part and the width direction land part in some embodiment shown above is only an illustration, and another form can also be implemented by combining these. Further, not only the shape and number of the circumferential land portion and the width direction land portion, but also the shape and arrangement of the buttress block and the small block are all shown in the embodiment described here to explain the tire according to the present invention. It should be noted that the embodiment can be appropriately changed without departing from the spirit of the present invention.

  According to the present invention, even when a small block is arranged in at least the shoulder region of the tread portion, a load force that varies depending on the arrangement position of the small block is considered while maintaining a good rolling resistance due to the small block. Thus, the shearing force in the ground contact surface can be made uniform, and uneven wear of the block in the tread portion can be suppressed.

DESCRIPTION OF SYMBOLS 1 Tire 2 Grounding end 3 Groove 4 Small block 5 Rim 6 Buttress block 7 Bead part 8 Carcass 9 Belt layer 10 Buttress block circumferential land part 11 Small block circumferential land part 12 Width direction land part SGb Small block group BGb Buttress block row SA shoulder area CA center area

Claims (6)

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 array in which extending buttress blocks are arranged in the circumferential direction,
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 phases in the tire circumferential direction of the small blocks constituting the adjacent columns are different from each other,
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 pneumatic tire characterized in that, in the shoulder region, a buttress block circumferential land portion that connects buttress blocks adjacent in the circumferential direction is arranged in at least one buttress block row.   A small block circumferential land portion connecting small blocks adjacent to each other in the tire circumferential direction is arranged between the small blocks constituting the column, and the buttress block circumferential land portion and the small block circumferential land portion are tread-circulated. 2. The pneumatic tire according to claim 1, wherein the tread circumferential land portion has a larger volume in the tread circumferential land portion located on the outer side in the tire width direction when the directional land portion is used.   The width direction land part which connects the blocks which adjoin each other in the tire width direction is arrange | positioned between the blocks which comprise the said buttress block row | line | column and the said small block row | line | column which adjoin each other, It is characterized by the above-mentioned. Pneumatic tire.   The air according to any one of claims 1 to 3, wherein an average height of the land portion in the circumferential direction of the buttress block is not less than 1/3 and not more than 9/10 of a height of the buttress block. Enter tire.   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.   The mounting direction to a vehicle is determined, and the buttress block including the circumferential land portion of the buttress block is located inside the vehicle with the tire equatorial plane as the center when the vehicle is mounted. The pneumatic tire according to any one of 1 to 5.

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