JP2012041024A - Tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire including a block formed with a plurality of sipes along a tread width direction and suppressing uneven wear in a tire peripheral direction without reducing edges.SOLUTION: This tire 1 includes the block 10 sectioned by a plurality of groove parts and formed with three or more sipes extending in the tread width direction in a tread part 5. When a tire radial direction depth from a block tread 10a to the bottom of the sipe at the tire radial direction inside is a sipe depth D in cross section along the tire peripheral direction and a tire radial direction, the sipe depth becomes shallower from a center O of the block 10 in the tire peripheral direction toward a side surface 10b of the block 10 in the tire peripheral direction.

Description

  The present invention relates to a tire having a block in which a plurality of sipes are formed along a tread width direction.

  Conventionally, tires in which sipes extending in the tread width direction are formed on a block are widely known. By forming the sipe, the edge of the block is increased, and the traction performance is improved particularly on an icy and snowy road. However, since the end portion of the block in the tire circumferential direction easily falls down due to the formation of the sipe, a difference in block rigidity occurs between the end portion and the central portion of the block, and uneven wear occurs.

  In order to suppress the occurrence of uneven wear, a method is known in which the sipe formed at the end of the block is a so-called three-dimensional sipe or the sipe formation interval is changed (see Patent Document 1).

  Unevenness is formed inside the block by a three-dimensional sipe extending in a zigzag shape in the tread width direction and the tire radial direction. The unevenness of the block supports the unevenness of the adjacent block portion across the sipe, and the block rigidity is improved.

  Further, by making the distance from the sipe closest to the side surface of the block in the circumferential direction of the block to the side surface of the block larger than the interval between the other sipes, it is difficult for the block end to fall down.

JP 2005-41339 A

  However, even if the block rigidity is improved by the three-dimensional sipe, there is a difference in the block rigidity between the central portion and the end portion of the block, and uneven wear sometimes occurs. Moreover, when the space | interval from the side surface of a block to the sipe near a side surface is enlarged, the number of sipes which can be formed in a block will be restricted. Therefore, the edge of the block is reduced, and the required traction performance may not be obtained.

  Moreover, in the tire of patent document 1, the block rigidity between the edge part and center part of a block was not considered. That is, the block rigidity of the block portion from the sipe close to the side surface of the block to the next sipe close to the side surface is smaller than the block rigidity of the central portion and the end portion of the block, and uneven wear may occur.

  Therefore, the present invention has been made in view of such a situation, and in a tire having a block in which a plurality of sipes are formed along the tread width direction, the deviation in the tire circumferential direction is achieved without reducing the edge. It aims at providing the tire which controlled wear.

  In order to solve the above-described problems, the present invention has the following features. A feature of the present invention is a tire provided with a block in which three or more sipes extending in the tread width direction are formed in the tread portion, and a cross section along the tire circumferential direction and the tire radial direction. In the cross section, in the cross section, from the center of the block in the tire circumferential direction, the tire radial direction depth from the block tread surface in contact with the road surface of the block to the bottom of the sipe inside the tire radial direction is the sipe depth. The gist is that the sipe depth becomes shallower toward the side surface of the block in the tire circumferential direction.

  According to the features of the present invention, in the cross section along the tire circumferential direction and the tire radial direction, the sipe depth becomes shallower from the center of the block in the tire circumferential direction toward the side surface of the block in the tire circumferential direction. The block portion where the sipe depth is shallower is divided by the sipe, and the block portion is less likely to fall down. For this reason, the block rigidity of the edge part of a block improves. The central part of the block is easy to fall down in that the sipe depth is deep, but the rigidity of the block is large because it supports each other adjacent block parts. Accordingly, the difference in block rigidity between the center portion and the end portion of the block is reduced, and the block rigidity can be made uniform from the center to the side surface of the block. As a result, uneven wear of the block can be suppressed.

  Since the difference in block rigidity can be reduced without adjusting the sipe interval, the number of sipe forming the edge does not decrease.

  Another feature of the present invention is that, in the cross section, the sipe depth is shallow so that a line connecting the bottoms of the sipe formed from the center of the block to the side surface of the block is a straight line. The gist.

  Another feature of the present invention is that the sipe extends in the tread width direction in a zigzag shape and linearly extends in the tire radial direction, and extends in the tread width direction in a zigzag shape, or in a zigzag shape or A three-dimensional sipe that refracts and extends in the tire radial direction, and when the block is equally divided into three in the tire circumferential direction, a region located in the center is defined as a central region, and at both ends in the tire circumferential direction Assuming that the positioned region is an end region, the two-dimensional sipe is formed in the central region, and the three-dimensional sipe is formed in the end region.

  Another feature of the present invention is that, in the tire circumferential direction, the sipe depth of the side sipe formed closest to the side surface is a depth from the block tread surface to the bottom surface of the groove portion. The point is that it is deeper than half.

  Another feature of the present invention is that the sipe depth of the deepest sipe is defined as a deepest sipe formed at the center of the block including the center of the block in the tire circumferential direction. The gist is that the depth is 70% or more of the depth of the groove, which is the depth from the block tread surface to the bottom surface of the groove.

  Another feature of the present invention is summarized in that the sipe depth of the deepest sipe is 80% or more of the groove depth.

  Another feature of the present invention is that the sipe includes a two-dimensional sipe extending zigzag in the tread width direction and linearly extending in the tire radial direction, and in the cross section, the center of the block in the tire circumferential direction. The block length that is the length from the block circumferential surface to the side surface of the block is A, the groove depth that is the depth from the block tread surface to the bottom surface of the groove portion is B, and the tire circumferential direction is The tire from the side surface of the block to the two-dimensional sipe in the tire circumferential direction, where C is the sipe depth of the deepest sipe formed at the center of the block including the center of the block and the sipe depth is the deepest sipe When the circumferential length is x and the sipe depth of the two-dimensional sipe having the tire circumferential length x is D2, D2 = (B / 2) {C- (B / 2)} × (x / A), so as to satisfy (x ≦ A), the two-dimensional sipes, the gist to be formed.

  Another feature of the present invention is that the sipe includes a three-dimensional sipe that extends in the tread width direction in a zigzag shape and extends in the tire radial direction in a zigzag shape, or in the tire circumferential direction in the cross section. The block length, which is the length from the center of the block to the side surface of the block in the tire circumferential direction, is A, and the groove portion depth, which is the depth from the block tread surface to the bottom surface of the groove portion, is B, and the tire Formed in the center of the block including the center of the block in the circumferential direction, the sipe depth of the deepest sipe that is the deepest sipe is C, and is formed closest to the side surface of the block in the tire circumferential direction The tire circumferential length to the sipe is x, a constant in the range of 0.80 to 0.95 is R, and the three-dimensional Assuming that the sipe depth of the die is D3, the above 3 is satisfied so that D3 = {(B / 2) + [C− (B / 2)] × (x / A)} × R, (x ≦ A). The gist of dimensional sipes is that they are formed.

  Another feature of the present invention is that the sipe includes a three-dimensional sipe extending in the tread width direction and the tire radial direction in a zigzag shape, and the three-dimensional sipe extending in the tire radial direction in the cross section is formed in a zigzag shape. And a linear straight sipe portion sandwiched between the zigzag sipe portion and the block tread surface in the tire radial direction, and the tire radial length of the zigzag sipe portion is: The gist is that the straight sipe portion is longer than the length in the tire radial direction.

  According to the present invention, in a tire having a block in which a plurality of sipes are formed along the tread width direction, it is possible to provide a tire that suppresses uneven wear in the tire circumferential direction without reducing edges.

FIG. 1 is a cross-sectional view of the tire 1 according to this embodiment along the tread width direction and the tire radial direction. FIG. 2 is an explanatory diagram for explaining the arrangement of the blocks of the tread portion 5 of the tire 1 according to the present embodiment. FIG. 3A is a perspective view of the block 10 according to the present embodiment. FIG.3 (b) is AA sectional drawing of Fig.3 (a). FIG. 4A is a perspective view of a block 10 according to a modification of the present embodiment. FIG. 4B is a BB cross-sectional view of FIG. Fig.5 (a) is a perspective view of the block 10 which concerns on the modification of this embodiment. FIG.5 (b) is CC sectional drawing of Fig.5 (a). FIG. 6A is a perspective view of a block 10 according to a modification of the present embodiment. FIG. 6B is a DD cross-sectional view of FIG. Fig.7 (a) is a perspective view of the block 10 which concerns on the modification of this embodiment. FIG.7 (b) is EE sectional drawing of Fig.7 (a).

  An example of a tire according to the present invention will be described with reference to the drawings. Specifically, (1) schematic configuration of tire 1, (2) block 10, (3) modified example of sipe 100, (4) other embodiments, (5) operational effects, (6) comparative evaluation will be described. To do.

  In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. It should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. It goes without saying that the drawings include parts having different dimensional relationships and ratios.

(1) Schematic Configuration of Tire 1 A schematic configuration of the tire 1 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of the tire 1 according to this embodiment along the tread width direction and the tire radial direction. FIG. 2 is an explanatory diagram for explaining the arrangement of the blocks of the tread portion 5 of the tire 1 according to the present embodiment.

  As shown in FIGS. 1 and 2, the tire 1 according to the present embodiment includes a block 10, a circumferential groove 20, a width groove 25, a bead core 40, a carcass 50, and a belt 60.

  As shown in FIGS. 1 and 2, the block 10 is partitioned by a plurality of circumferential grooves 20 and width grooves 25 in the tread portion 5. In the present embodiment, the block 10 is partitioned so as to have a tire circumferential direction length L and a tread width direction length W. The circumferential groove 20 is a groove extending along the tire circumferential direction. The width direction groove portion 25 is a groove portion extending along the tread width direction.

  The bead core 40 is disposed in the bead portion. The carcass 50 is disposed so as to straddle the pair of bead cores 40. Two belts 60 are arranged outside the carcass 50 in the tire radial direction in the tread portion 5.

(2) Block 10
The block 10 according to the present embodiment will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3A is a perspective view of the block 10 according to the present embodiment. FIG.3 (b) is AA sectional drawing of Fig.3 (a). Therefore, FIG.3 (b) is sectional drawing along the tire radial direction and tire circumferential direction of the block 10 which concerns on this embodiment.

  As shown in FIGS. 3A and 3B, the block 10 is formed with three or more sipes extending in the tread width direction. Specifically, five sipes 100 are formed in the block 10. The sipe 100 includes three types of sipe 110, sipe 120, and sipe 130. The sipe 110 is located at the center O in the tire circumferential direction of the block 10. The sipe 120 is located between the sipe 110 and the sipe 130 in the tire circumferential direction. The sipe 130 is positioned closest to the side surface 10b of the block 10 in the tire circumferential direction in the tire circumferential direction. The sipes 100 are formed at equal intervals in the tire circumferential direction.

  As shown in FIG. 3B, the block length, which is the length from the center O of the block 10 to the side surface 10b in the tire circumferential direction, is A. Therefore, L = 2A. A groove depth which is a depth from the block tread surface 10a to the bottom surface 28 of the width direction groove 25 is defined as B. The sipe depth of the deepest sipe that is formed at the center of the block including the center O and has the deepest sipe depth is C. Therefore, in the present embodiment, the deepest sipe is the sipe 110. The depth in the tire radial direction from the block tread surface 10a in contact with the road surface of the block 10 to the bottom of the sipe 100 on the inner side in the tire radial direction is a sipe depth D. Therefore, the sipe depth D of the sipe 110 is C. Further, the sipe depth of the side surface sipe formed closest to the side surface 10b is defined as Ds. Therefore, in this embodiment, the side sipe is the sipe 130. Therefore, the sipe depth D of the sipe 130 is Ds.

  As shown in FIG. 3B, the depth C from the block tread 10 a to the bottom 115 of the sipe 110 is deeper than the sipe depth D from the block tread 10 a to the bottom 125 of the sipe 120. The sipe depth D from the block tread 10 a to the bottom 125 of the sipe 120 is deeper than the sipe depth Ds from the block tread 10 a to the bottom 135 of the sipe 130. Accordingly, the sipe depth becomes shallower from the center O toward the side surface 10b in the tire circumferential direction. More specifically, the sipe depth is shallow so that the bottoms of the sipe 100 formed from the center O to the side surface 10b, that is, lines connecting the bottom 115, the bottom 125, and the bottom 135 are straight lines.

  The sipe depth C of the sipe 130 is equal to the groove depth B that is the depth to the bottom surface 28 of the widthwise groove 25. Therefore, the sipe depth C of the sipe 130 is 70% or more of the groove depth B. Thus, the sipe depth C of the sipe 130 is preferably 70% or more of the groove depth B. The sipe depth C of the sipe 130 is more preferably 80% or more of the groove depth B. Further, the sipe depth Ds of the side sipe is more preferably deeper than half of the groove depth B.

  The sipe 100 has a groove width that can be closed when the block 10 is grounded. Specifically, the sipe 100 has a groove width of 1.5 mm or less. However, in a tire used for a large bus or truck such as a TBR tire, the groove width of the sipe may be 1.5 mm or more. Since the sipe has such a groove width, the blocks support each other at the time of ground contact, so that the block rigidity can be increased.

(3) Modified Example of Sipe 100 A modified example of the tire 1 according to the present embodiment will be described with reference to FIGS. 4 to 7. In the following description, portions similar to those of the tire according to the above embodiment are omitted as appropriate. FIG. 4A is a perspective view of a block 10 according to a modification of the present embodiment. FIG. 4B is a BB cross-sectional view of FIG. Fig.5 (a) is a perspective view of the block 10 which concerns on the modification of this embodiment. FIG.5 (b) is CC sectional drawing of Fig.5 (a). FIG. 6A is a perspective view of a block 10 according to a modification of the present embodiment. FIG. 6B is a DD cross-sectional view of FIG. Fig.7 (a) is a perspective view of the block 10 which concerns on the modification of this embodiment. FIG.7 (b) is EE sectional drawing of Fig.7 (a).

(3.1) Modification 1
As shown in FIGS. 4A and 4B, six sipes 200 extending in the tread width direction are formed in the block 10. The sipe 200 includes a two-dimensional sipe that extends in a zigzag shape in the tread width direction and linearly extends in the tire radial direction.

  The sipe 200 includes a sipe 210, a sipe 220, and a sipe 230, which are three types of sipes. The sipe 210 is located at the center of the block 10 in the tire circumferential direction. The sipe 210 is deviated from the center O, which is the center of the block 10 in the tire circumferential direction. The sipe 220 is located between the sipe 210 and the sipe 230 in the tire circumferential direction. The sipe 230 is located closest to the side surface 10b in the tire circumferential direction. In the sipe 200, sipe intervals are not uniform in the tire circumferential direction. Specifically, in the tire circumferential direction, the distance between the sipe 210 and the distance between the sipe 210 and the sipe 220 are the same, but the distance between the sipe 210 and the sipe 220 and the distance between the sipe 220 and the sipe 230. Is different.

  In the sipe 200, the sipe intervals are not uniform in the tire circumferential direction, but the bottoms of the sipe 200 formed from the center O to the side surface 10b, that is, the lines connecting the bottom 215, the bottom 225, and the bottom 235 are straight. In addition, the sipe depth becomes shallower.

  Here, the length in the tire circumferential direction from the side surface 10b to the sipe 200 in the tire circumferential direction is defined as x. The sipe depth D2 of the sipe in which the tire circumferential direction length is x satisfies the following formula 1.

D2 = (B / 2) + {C− (B / 2)} × (x / A) (Formula 1)
x is a numerical value not more than A (that is, x ≦ A).

  If the sipe 200 is formed so as to satisfy Formula 1, uneven wear in the tire circumferential direction can be suppressed.

(3.2) Modification 2
As shown in FIGS. 5A and 5B, five sipes 300 extending in the tread width direction are formed in the block 10. The sipe 300 is formed of a three-dimensional sipe that extends in the tread width direction in a zigzag shape, refracts, and extends in the tire radial direction.

  The sipe 300 includes a sipe 310, a sipe 320, and a sipe 330, which are three types of sipes. The sipe 310 is located at the center of the block 10 in the tire circumferential direction. The sipe 320 is located between the sipe 310 and the sipe 330 in the tire circumferential direction. The sipe 330 is located closest to the side surface 10b in the tire circumferential direction. The sipes 300 are formed at equal intervals in the tire circumferential direction.

  In the sipe 300, the sipe depth is shallow so that the bottoms of the sipe 300 formed from the center O to the side surface 10b, that is, lines connecting the bottom 315, the bottom 325, and the bottom 335 are straight lines.

  Here, the length in the tire circumferential direction from the side surface 10b to the sipe 300 in the tire circumferential direction is defined as x. Let R be a constant in the range of 0.80 or more and 0.95 or less. The sipe depth D3 of the sipe in which the tire circumferential length is x satisfies the following Expression 2.

D3 = {(B / 2) + [C- (B / 2)] × (x / A)} × R
x is a numerical value not more than A (that is, x ≦ A).

  If the sipe 300 is formed so as to satisfy Formula 2, uneven wear in the tire circumferential direction can be suppressed.

(3.3) Modification 3
As shown in FIGS. 6A and 6B, five sipes 400 extending in the tread width direction are formed in the block 10. The sipe 400 is a three-dimensional sipe that extends in a zigzag shape in the tread width direction and extends in a zigzag shape in the tire radial direction.

  The sipe 400 includes three types of sipe 410, a sipe 420, and a sipe 430. The sipe 410 is located at the center of the block 10 in the tire circumferential direction. The sipe 420 is located between the sipe 410 and the sipe 430 in the tire circumferential direction. The sipe 430 is located closest to the side surface 10b in the tire circumferential direction. The sipes 400 are formed at equal intervals in the tire circumferential direction.

  The sipe 400 includes a zigzag zigzag sipe portion and a linear straight sipe portion sandwiched between the zigzag sipe portion and the block tread surface 10a in the tire radial direction. The tire radial direction length d2 of the zigzag sipe part is longer than the tire radial direction length d2 of the linear sipe part. Specifically, the sipe 410 includes a straight sipe portion 412 and a zigzag sipe portion 417. The tire radial direction length d2 of the zigzag sipe portion 417 is longer than the tire radial direction length d2 of the linear sipe portion 412. Similarly, the sipe 420 includes a straight sipe portion 422 and a zigzag sipe portion 427. The tire radial direction length d2 of the zigzag sipe portion 427 is longer than the tire radial direction length d2 of the linear sipe portion 422. The sipe 430 includes a straight sipe portion 432 and a zigzag sipe portion 437. The tire radial direction length d2 of the zigzag sipe portion 437 is longer than the tire radial direction length d2 of the linear sipe portion 432.

  The sipe 400 has a shallow sipe depth so that the bottoms of the sipe 400 formed from the center O to the side surface 10b, that is, lines connecting the bottom 415, the bottom 425, and the bottom 435 are straight. Moreover, the sipe 400 is formed so that Formula 2 may be satisfy | filled similarly to the modification 3.

(3.4) Modification 4
As shown in FIGS. 7A and 7B, seven sipes 500 extending in the tread width direction are formed in the block 10. The sipe 500 includes a two-dimensional sipe extending zigzag in the tread width direction and extending linearly in the tire radial direction, and a three-dimensional sipe extending zigzag in the tread width direction and extending zigzag in the tire radial direction.

  When the block 10 is equally divided into three in the tire circumferential direction, a region located in the center is defined as a central region CR, and regions located at both ends in the tire circumferential direction are defined as end region ER. Therefore, the tire circumferential direction lengths of the center region CR and the end region ER are L / 3, respectively. Sipe 510 and sipe 520, which are two-dimensional sipes, are formed in the central region CR. The three-dimensional sipe sipe 530 and sipe 540 are formed in the end region ER.

  The sipe 510 is located at the tire circumferential center O of the block 10. The sipe 520 is located between the sipe 510 and the sipe 530 in the tire circumferential direction. The sipe 530 is located between the sipe 530 and the sipe 540 in the tire circumferential direction. The sipe 530 includes a straight sipe portion 532 and a zigzag sipe portion 537. The sipe 540 is located closest to the side surface 10b in the tire circumferential direction. The sipe 540 includes a straight sipe portion 542 and a zigzag sipe portion 547. The sipes 100 are formed at equal intervals in the tire circumferential direction.

  The sipe depth becomes shallower from the center O toward the side surface 10b in the tire circumferential direction. Sipe 510 and sipe 520 that are two-dimensional sipes are formed so as to satisfy Equation 1. Sipe 530 and sipe 540 that are three-dimensional sipes are formed so as to satisfy Equation 2. Therefore, the bottom portion 535 of the sipe 530 and the bottom portion 545 of the sipe 540 have a sipe depth as compared with the case where the bottom portion of the two-dimensional sipe is formed at the same position in the tire circumferential length x from the side surface 10b to the sipe 500. Becomes shallower. Accordingly, in the sipe 500, the bottoms of the sipe 500 formed from the center O to the side surface 10b, that is, the lines connecting the bottom 515, the bottom 525, the bottom 535, and the bottom 545 are not straight lines. In this way, the depth of the three-dimensional sipe is reduced to adjust the block rigidity of the end region ER. As a result, there is no difference in block rigidity between the center region CR and the end region ER, and uneven wear in the tire circumferential direction can be suppressed. The sipe 530 and the sipe 540 include a zigzag zigzag sipe part and a linear straight sipe part sandwiched between the zigzag sipe part and the block tread surface 10a in the tire radial direction. This is the same as the third modification.

(4) Other Embodiments Although the contents of the present invention have been disclosed through the embodiments of the present invention, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. The present invention includes various embodiments not described herein.

  For example, in the present embodiment and the modification, the sipe depth is deeper than half of the groove depth B that is the depth from the block tread surface 10a to the bottom surface 28, but this is not necessarily required. For example, the sipe depth Ds of the side sipe may be B / 2. Furthermore, Ds <B / 2 may be satisfied.

  In addition, a linear one-dimensional sipe, a two-dimensional sipe, and a three-dimensional sipe may be formed in the block 10 in the tread width direction and the tire radial direction.

  The tire according to the present invention may be a pneumatic tire or a tire filled with rubber. Moreover, a gas-filled tire other than air containing a rare gas such as argon may be used.

(5) Effects According to the present invention, in the cross section along the tire circumferential direction and the tire radial direction, the sipe depth D increases from the center O of the block 10 in the tire circumferential direction toward the side surface 10b in the tire circumferential direction. It becomes shallower. The block portion where the sipe depth D is shallower than the sipe is less likely to fall down. For this reason, the block rigidity of the edge part of a block improves. The central part of the block is easy to fall down in that the sipe depth D is deep, but the block at the central part of the block has high rigidity because it supports each other with the adjacent block part. Therefore, the difference in block rigidity between the center portion and the end portion of the block 10 is reduced, and the block rigidity can be made uniform from the center to the side surface of the block 10. As a result, uneven wear of the block 10 can be suppressed.

  Further, since the difference in block rigidity between the central portion and the end portion of the block 10 can be reduced without adjusting the sipe interval, the number of sipes forming the edge is not reduced. Therefore, the traction performance can be maintained.

  According to the present invention, the sipe depth D is shallow so that the line connecting the bottoms of the sipe formed from the center O of the block 10 to the side surface 10b is a straight line. Thus, by forming the sipe, the block rigidity can be made uniform from the center O of the block 10 to the side surface 10b. As a result, uneven wear of the block 10 can be suppressed.

  According to the present invention, including a two-dimensional sipe and a three-dimensional sipe, the two-dimensional sipe is formed in the central region CR, and the three-dimensional sipe is formed in the end region ER. By forming a three-dimensional sipe having higher rigidity than the two-dimensional sipe in the end region ER, the block rigidity can be made uniform.

  According to the present invention, the sipe depth D of the side sipe formed closest to the side surface 10b in the tire circumferential direction is the groove depth that is the depth from the block tread surface 10a to the bottom surface 28 of the widthwise groove portion 25. Deeper than half of B. In the studless tire, if the height of the block 10 is worn down to half of the height from the block tread surface 10a to the bottom surface 28, it cannot be used as a studless tire in terms of safety. By making the sipe depth D deeper than half of the height from the block tread surface 10a to the bottom surface 28, even if the block 10 is reduced to a half that can be effectively used as a studless tire, sipe exists and effective traction performance is achieved. Can demonstrate.

  According to the present invention, when the sipe having the deepest sipe depth is defined as the deepest sipe, the sipe depth C of the deepest sipe is determined from the block tread surface 10a. The depth is 70% or more of the groove depth B which is the depth to the bottom surface 28. Further, the sipe depth C of the deepest sipe is 80% or more of the groove depth. By deepening the deepest sipe by 70% or more, the edge acts effectively due to the collapse of the block, and effective traction performance can be exhibited. Further, by increasing the sipe depth C of the deepest sipe, the sipe depth D of the side sipe can be made deeper than half of the groove depth B.

  According to the present invention, a sipe includes a two-dimensional sipe, and D2 = (B / 2) + {C− (B / 2)} × (x / A) where the sipe depth of the two-dimensional sipe is D2. , (X ≦ A), the two-dimensional sipe is formed. Further, the sipe includes a three-dimensional sipe, and when the sipe depth of the two-dimensional sipe is D2, D3 = {(B / 2) + [C− (B / 2)] × (x / A)} × R , (X ≦ A), the three-dimensional sipe is formed. By determining the sipe depth so as to satisfy these equations, the block rigidity can be made uniform from the center O of the block 10 to the side surface 10b. As a result, uneven wear of the block 10 can be suppressed.

  According to the present invention, the sipe includes a three-dimensional sipe extending in the tread width direction and the tire radial direction in a zigzag manner, and the three-dimensional sipe includes a zigzag zigzag sipe portion, and a zigzag sipe portion and a block tread surface in the tire radial direction. 10a, and the tire radial direction length of the zigzag sipe part is longer than the tire radial direction length of the linear sipe part. Since the zigzag sipe portion is longer than the straight sipe portion, the block rigidity can be further improved. When the zigzag sipe portion is in contact with the block tread surface 10a, the block tread surface 10a and the zigzag portion form a portion having an acute edge angle in the tire radial direction and a portion having an obtuse angle. Wear is fast at the sharp edge part. By forming the straight sipe portion on the block tread surface 10a side, the block surface can be evenly worn and uneven wear can be suppressed.

(6) Comparative evaluation In order to confirm the effect of the present invention, the amount of wear was compared. In the tire used for the evaluation, five sipes are formed in the tread width direction in the block. In the block of Example 1, a two-dimensional sipe was formed. In the block of Example 2, a three-dimensional sipe was formed. In the block of Example 3, the sipe formed at the center of the block and the sipe adjacent to the center of the block were two-dimensional sipe. The sipe formed near the side surface in the tire circumferential direction was a three-dimensional sipe. In the block of Comparative Example 1, a two-dimensional sipe was formed. Sipe distance relationships are shown in Table 1. A is the distance from the tire circumferential side surface 10b of the block to the center O of the block 10. B is the distance from the block tread surface 10 a to the bottom surface 28 of the width direction groove 25. xa is a tire circumferential direction distance from the side surface 10b to a sipe formed near the side surface in the tire circumferential direction. xb is the distance in the tire circumferential direction from the side surface 10b to the next sipe formed near the side surface in the tire circumferential direction. C is the groove depth of the sipe formed at the center O of the block 10. Ca is the groove depth of the sipe formed near the side surface in the tire circumferential direction. Cb is the groove depth of the sipe formed next near the side surface in the tire circumferential direction.

  The amount of wear was measured by running the tire on which each sipe was formed under the following measurement conditions. Specifically, the amount of wear at the center O portion (center portion) of the block 10 and the amount of wear at the circumferential end of the block 10 were measured. Further, the wear amount at the center portion with respect to the wear amount at the end portion was defined as a partial wear rate. As the uneven wear rate is closer to 1, uneven wear in the tire circumferential direction is suppressed. The results are shown in Table 1.

・ Tire size: 195 / 65R15
・ Rim size: 6JJ
・ Vehicle: FF vehicle ・ Internal pressure: 230kPa
・ Load: 60kg and driver ・ Mileage: 5000km

  As shown in Table 1, as compared with the comparative example in which all the groove depths of the sipe are the same, all the tires according to the working examples have a partial wear rate close to 1. That is, uneven wear in the tire circumferential direction is suppressed. In particular, in Example 3, the amount of wear at the center and the end is equal. As described above, according to the present invention, it was found that uneven wear in the tire circumferential direction can be suppressed.

  It should be noted that the technical scope of the present invention is not limited to this embodiment, but is defined only by the invention specifying matters according to the scope of claims reasonable from the description of the entire specification described above.

  DESCRIPTION OF SYMBOLS 1 ... Tire, 5 ... Tread part, 10 ... Block, 10a ... Block tread, 10b ... Side face, 20 ... Circumferential groove part, 25 ... Width direction groove part, 28 ... Bottom face, 40 ... Bead core, 50 ... Carcass, 60 ... Belt, 100,110,120,130,200,220,230,300,310,320,330,400,410,420,430,500,510,520,530,540 ... Sipe, 115,125,135,215 225, 235, 315, 325, 335, 415, 425, 435, 515, 525, 535, 545 ... bottom, 412, 422, 432, 532, 542 ... linear sipes, 417, 427, 437, 537, 547 ... Zigzag sipe part

Claims (9)

In the tread portion, a tire including a block that is partitioned by a plurality of groove portions and has three or more sipes extending in the tread width direction,
In the section along the tire circumferential direction and the tire radial direction, when the tire radial depth from the block tread surface contacting the road surface of the block to the bottom of the sipe inside the tire radial direction is the sipe depth,
In the cross section, the sipe depth becomes shallower from a center of the block in the tire circumferential direction toward a side surface of the block in the tire circumferential direction.   The tire according to claim 1, wherein in the cross section, the sipe depth is shallow so that a line connecting the bottom portions of the sipe formed from the center of the block to the side surface of the block is a straight line. The sipe extends in the tread width direction in a zigzag shape and linearly extends in the tire radial direction, and extends in the tread width direction in a zigzag shape, and zigzags or refracts in the tire radial direction. Extending three-dimensional sipe,
When the block is equally divided into three in the tire circumferential direction, a region located in the center is a central region, and regions located at both ends in the tire circumferential direction are end regions,
The two-dimensional sipe is formed in the central region;
The tire according to claim 1, wherein the three-dimensional sipe is formed in the end region.   2. The sipe depth of a side sipe formed closest to the side surface in the tire circumferential direction is deeper than half of a groove depth that is a depth from the block tread surface to a bottom surface of the groove portion. 4. The tire according to any one of items 1 to 3. When the sipe having the deepest sipe depth is formed at the center of the block including the center of the block in the tire circumferential direction,
The tire according to any one of claims 1 to 4, wherein the sipe depth of the deepest sipe is a depth of 70% or more of a groove portion depth that is a depth from the block tread surface to a bottom surface of the groove portion. .   The tire according to claim 5, wherein the sipe depth of the deepest sipe is 80% or more of the groove depth. The sipe includes a two-dimensional sipe that extends in a zigzag manner in the tread width direction and linearly extends in the tire radial direction,
In the cross section, A is a block length that is a length from the center of the block in the tire circumferential direction to a side surface of the block in the tire circumferential direction, and a depth from the block tread surface to the bottom surface of the groove portion. The groove depth is B, the sipe depth of the deepest sipe that is formed at the block center including the center of the block in the tire circumferential direction, and the sipe depth is the deepest sipe, and C is the sipe depth in the tire circumferential direction. When the tire circumferential length from the side surface of the block to the two-dimensional sipe is x, and the sipe depth of the two-dimensional sipe where the tire circumferential length is x is D2,
D2 = (B / 2) + {C− (B / 2)} × (x / A), (x ≦ A)
The tire according to any one of claims 1 to 6, wherein the two-dimensional sipe is formed so as to satisfy the condition. The sipe includes a three-dimensional sipe that extends in a zigzag shape in the tread width direction and extends in the tire radial direction in a zigzag shape or refracted,
In the cross section, A is a block length that is a length from the center of the block in the tire circumferential direction to a side surface of the block in the tire circumferential direction, and a depth from the block tread surface to the bottom surface of the groove portion. The groove depth is B, the sipe depth of the deepest sipe that is formed at the block center including the center of the block in the tire circumferential direction, and the sipe depth is the deepest sipe, and C is the sipe depth in the tire circumferential direction. The tire circumferential length from the side surface of the block to the sipe formed closest to the tire is x, a constant in the range of 0.80 to 0.95 is R, and the sipe depth of the three-dimensional sipe Is D3,
D3 = {(B / 2) + [C- (B / 2)] × (x / A)} × R, (x ≦ A)
The tire according to any one of claims 1 to 7, wherein the three-dimensional sipe is formed so as to satisfy the condition. The sipe includes a three-dimensional sipe extending in a zigzag shape in the tread width direction and the tire radial direction,
In the cross section, the three-dimensional sipe extending in the tire radial direction includes a zigzag zigzag sipe part and a linear straight sipe part sandwiched between the zigzag sipe part and the block tread in the tire radial direction. Comprising and including
The tire according to any one of claims 1 to 8, wherein the tire radial direction length of the zigzag sipe portion is longer than the tire radial direction length of the linear sipe portion.

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