JP2010058696A - Tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire with improved friction resistance and crack resistance while maintaining a traction performance on a wet road by making a sipe into a proper shape in a tire having a sipe at a rib-like land part. <P>SOLUTION: In this tire, one or more rows of rib-like land parts are provided on a tread part, and sipes are provided to the rib-like land parts. Also, depth of the sipes at least at a shoulder side end is smaller than depth of the residual portion. Furthermore, an enlarged portion having a tire circumferential length larger than an opening width of the sipes on a tread of a tread part is provided at least to a part of a groove bottom of the sipe. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tire having at least one row of rib-like land portions in a tread portion and having a sipe in the rib-like land portions, particularly a heavy load tire, and maintains the traction performance on the wet road surface of such tires. However, the wear resistance and crack resistance are improved.

  The rib-like land portion has higher wear resistance because of its higher rigidity than the block land portion. However, the rib-like land portion has a problem that uneven wear called river wear, in which the vicinity of the edge is locally worn in the circumferential direction, is likely to occur. Riverwear has a small step near the edge of the rib due to the lateral force applied to the tire during traveling, and the stepped portion is dragged due to the difference in diameter, causing sliding wear. The amount of wear is larger than the amount of wear on the center side of the rib-like land portion, resulting in uneven wear.

  Moreover, in order to improve the traction performance on the wet road surface of a tire having a rib-like land portion, for example, Patent Document 1 discloses a tire provided with sipes on the rib-like land portion.

JP-A-6-80002

  However, the tire of Patent Document 1 improves the traction performance on the wet road surface by sipe, but the rigidity of the rib-shaped land portion decreases, so when a lateral force is applied to the rib-shaped land portion during cornering traveling, The lateral force cannot be sufficiently resisted, and sliding wear occurs, and in particular, the edge portion on the outer side in the tire width direction of the rib-like land portion is worn early. As a result, the wear difference from the central portion of the rib-like land portion becomes large, and uneven wear (river wear) occurs. Further, when both edge portions of the rib-like land portion are compared, lateral force is more heavily applied to the edge portion on the outer side in the tire width direction. The edge portion on the outer side in the tire width direction has a larger wear amount than the edge portion. Furthermore, in the tire described in Patent Document 1, no consideration has been given to the fact that cracks are likely to occur at the groove bottom portion of the sipe during rolling of the tire load.

  Accordingly, an object of the present invention is to improve wear resistance and crack resistance on the premise of maintaining traction performance on wet road surfaces by optimizing the sipe shape in a tire having a sipe in a rib-like land portion. Is to provide tires.

  In order to achieve the above object, the present invention provides a tire having one or more rows of rib-like land portions in the tread portion and having sipes in the rib-like land portions, and the sipe has a depth at least at the end on the shoulder side. However, it is smaller than the depth of the remaining portion, and at least a part of the groove bottom of the sipe includes an enlarged portion having a tire circumferential length larger than the opening width of the sipe on the tread surface. It is. The “sipe opening width” herein refers to the length of the sipe in the tire circumferential direction on the tread surface.

  Moreover, it is preferable to provide an enlarged part in the groove bottom part which has the maximum depth.

  Furthermore, it is preferable to provide the enlarged portion in the groove bottom portion having the minimum depth.

  Furthermore, in the sipe, the minimum depth is preferably in the range of 0.50 to 0.95 times the maximum depth.

  In addition, it is preferable that the tire width direction length of the portion of the sipe having the maximum depth is in a range of 0.1 to 0.9 times the length of the rib-like land portion in the tire width direction.

  In addition, the length of the sipe in the tire width direction is preferably 0.80 or more times the length of the rib-like land portion in the tire width direction.

  Moreover, it is preferable that the depth of a sipe is 0.30 times or more of the depth of the circumferential groove which pinches | interposes a rib-like land part.

  Furthermore, a plurality of block land portion rows are defined by arranging a plurality of lateral grooves communicating with two adjacent circumferential grooves, and the circumferential groove is sandwiched between the block land portion rows. In at least two adjacent block land portion rows, the block land portions constituting the block land portion rows adjacent to each other across the circumferential groove are arranged so as to be shifted from each other in the tire circumferential direction. The extending direction of the groove portion between the block land portions adjacent to each other is inclined with respect to the tire width direction and the tire circumferential direction, and is adjacent to the tire width direction rather than the distance between the block land portions adjacent to the tire circumferential direction. It is preferable that the distance between the block land portions is short. Here, the “groove portion” is a part of the circumferential groove, which means a groove extending between the block land portions adjacent in the tire width direction, and “displaced” means the tire width. The arrangement is such that the circumferential edge of the block land portion does not coincide between the block land portions adjacent to each other in the tire width direction by changing the starting point of the arrangement pitch in the tire circumferential direction of the block land portion adjacent in the direction. And

  In addition, it is preferable that the length of the cross section of the block land portion in the tire width direction increases from both ends of the block land portion in the tire circumferential direction to the center portion of the block land portion. Here, the “center portion of the block land portion” refers to a region extending from the center position in the tire circumferential direction of the block land portion to both ends of the block land portion and in a range of 5 to 30% of the tire circumferential direction length of the block land portion. Shall.

  In addition, the ratio of the distance between block land portions adjacent in the tire width direction to the distance between block land portions adjacent in the tire circumferential direction is preferably in the range of 1: 0.85 to 1: 0.3.

  Moreover, it is preferable that ratio of the distance between the block land parts adjacent to a tire circumferential direction with respect to the tire circumferential direction length of a block land part exists in the range of 1: 0.25 to 1: 0.05.

  According to the present invention, in a tire having a sipe in a rib-like land portion, the tire is improved in wear resistance and crack resistance on the premise of maintaining traction performance on a wet road surface by optimizing the sipe shape. Can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a development view of a part of a tread portion of a typical tire according to the present invention, and FIG. 1B is a cross-sectional view taken along a line I-I in FIG. 1 (c) is a sectional view in the tire circumferential direction of the rib-like land portion of FIG. 1 (a), and FIG. 1 (d) is a perspective view of the rib-like land portion of FIG. 1 (a). FIGS. 2A and 2B are sectional views in the tire width direction of rib-like land portions in other tires according to the present invention. FIG. 3 is a diagram showing the relationship between the presence / absence of a driving force load and the movement position of the tread portion. FIG. 4 is a diagram showing a shearing force from the road surface when a driving force is applied. FIG. 5 is a diagram showing a deformation in an adjacent block land portion when a driving force is applied. FIG. 6 is a view showing a deformation in the block land portion when the block land portion adjacent in the tire circumferential direction is too close. 7 and 8 are development views of a part of the tread portion of another tire according to the present invention. FIG. 9 is a perspective view of the block land portion shown in FIG. FIG. 10A is a diagram showing the block land portion that is pressed horizontally against the road surface and is grounded, and FIG. 10B is pressed obliquely against the road surface and is grounded. It is the figure which showed the block land part. FIG. 11 is a diagram showing deformation in adjacent block land portions when driving force is applied. 12 and 13 are development views of a part of the tread portion of another tire according to the present invention. FIG. 14 is a perspective view of a rib-like land portion of another tire according to the present invention.

As shown in FIGS. 1 (a) and 1 (b), the tire according to the present invention is provided with a plurality of rows of rib-like land by disposing a plurality of circumferential grooves 2 extending in the tire circumferential direction in the tread portion 1. The section 3 is partitioned. The rib-shaped land portion 3 is provided with a sipe 4 that communicates two circumferential grooves 2 and 2 adjacent to the rib-shaped land portion in the tire width direction. In addition, as shown in FIG. 1 (b), the sipe 4 has a depth from the tread portion tread surface 5 to the groove bottom 6 of the sipe 4 on the shoulder side rather than the end portion on the tire equatorial plane CL side. P is smaller and the groove bottom 6 on the shoulder side is shallower. By adopting such a configuration and reducing the depth of the sipe 4 provided in the rib-like land portion 3 on the shoulder side, the rigidity of the edge portion 7 on the outer side in the tire width direction of the rib-like land portion 3 is improved. Therefore, even when a lateral force is greatly applied to the edge portion 7 on the outer side in the tire width direction of the rib-like land portion 3 during cornering traveling, the lateral force can be sufficiently resisted, and the edge portion on the outer side in the tire width direction can be resisted. The sliding wear in 7 is suppressed. As a result, the wear difference between the edge portion 7 on the outer side in the tire width direction and the central portion 8 of the rib-like land portion 3 is reduced, and uneven wear can be suppressed. Further, as shown in FIGS. 1C and 1D, the groove bottom 6 of the sipe 4 is provided with an enlarged portion 9 having a tire circumferential direction length larger than the opening width of the sipe 4 in the tread portion tread surface 5. . In general, when the tire rolls, the rubber on the groove bottom side of the sipe is repeatedly deformed, and stress is repeatedly applied to the rubber on the groove bottom of the sipe. May occur. If this crack propagates to the inner belt member or the like, there will be a problem in terms of durability. As a countermeasure, by providing the enlarged portion 9 on the groove bottom side of the sipe 4, the stress concentrated on the rubber at the groove bottom of the sipe 4 is distributed in a well-balanced manner, and cracks occur in the rubber on the groove bottom side of the sipe 4. Can be suppressed. Further, when the block land portion row 13 having the above-described configuration is provided, the rib-like land portion 3 according to the present invention is provided on the outer side in the tire width direction of the block land portion row 13, that is, on the shoulder side, as shown in the drawing. To do.
Note that the sipe 4 shown in FIG. 1 has the depth of the groove bottom 6 changed stepwise by changing the depth of the groove bottom 6 stepwise, but the depth is changed as shown in FIG. In addition, it is possible to vary the depth of the sipe 4 by uniformly inclining the groove bottom 6 of the sipe 4 with respect to the tire width direction. Alternatively, as shown in FIG. 2B, the depth of the sipe 4 can be varied by inclining the groove bottom 6 of the sipe 4 at a plurality of different angles.

  Moreover, it is preferable to provide the enlarged part 9 in the groove bottom part 10 which has the maximum depth. In general, as the sipe depth increases, the rigidity of the rib-like land portion decreases and the amount of rubber deformation at the time of tire load rolling increases, so that the load is applied to the groove bottom of the sipe. Stress also increases. Therefore, stress tends to concentrate on the groove bottom portion 10 having the maximum depth among the groove bottoms of the sipe, and cracks are likely to occur. As a countermeasure, by providing the enlarged portion 9 in the groove bottom portion 10 having the maximum depth, the stress applied to the groove bottom portion 10 can be efficiently dispersed, and the occurrence of cracks can be prevented. .

  Furthermore, it is preferable to provide the enlarged part 9 in the groove bottom part 11 having the minimum depth. As described above, since the deformation amount of the groove bottom portion 10 having the maximum depth at the time of tire load rolling is large, the groove having the minimum depth follows the deformation of the groove bottom portion 10 having the maximum depth. It will deform | transform excessively so that the bottom part 11 may be pulled. As a result, the stress is excessively concentrated on the groove bottom portion 11 having the minimum depth, and cracks are easily generated in the groove bottom portion 11. In particular, since the groove bottom portion 11 having the minimum depth close to the groove bottom portion 10 having the maximum depth is deformed by being pulled more strongly, cracks tend to be generated. As a countermeasure, by providing the enlarged portion 9 in the groove bottom portion 11 having the minimum depth, the stress applied to the groove bottom portion 11 can be efficiently dispersed to prevent the occurrence of cracks. . Alternatively, as a more preferred embodiment, as shown in FIGS. 2A and 2B, the enlarged portions 9 are provided in both the groove bottom portion 10 having the maximum depth and the groove bottom portion 11 having the minimum depth, It is possible to suppress the generation of cracks over the entire sipe.

Furthermore, among the depth of the sipe 4, the minimum depth _{H 1} is preferably in the range of from 0.50 to 0.95 times the maximum depth _{H 2.} When the minimum depth H ₁ is less than 0.50 times the maximum depth H ₂ , the rigidity of the edge portion 7 on the outer side in the tire width direction of the rib-like land portion 3 is sufficiently improved, and uneven wear is reduced. Although suppressed, the traction performance on the wet road surface by disposing the sipe 4 may be reduced. On the other hand, such minimum depth H ₁ is when it exceeds 0.95 times the maximum depth H _2, although traction performance on a wet road surface by disposing the sipe 4 is sufficiently ensured, the rib-like land Since the rigidity of the edge portion 7 on the outer side in the tire width direction of the portion 3 is not sufficiently improved, there is a possibility that uneven wear cannot be effectively suppressed. From this point of view, of the depth of the sipe 4, the minimum depth _{H 1} is, more preferably in the range of 0.60 to 0.85 times the maximum depth _{H 2.}

In addition, in the sipe 4, the tire width direction length W ₁ of the portion 10 having the maximum depth H ₂ is 0.1 to 0.9 times the tire width direction length W ₂ of the rib-like land portion 3. It is preferable to be in the range. Tire width direction length W ₁ of the portion 10 having such a maximum depth H ₂ is, in the case of more than 0.9 times the tire width direction length W ₂ of the rib-like land portion 3 is disposed sipe 4 Although the traction performance on the wet road surface is effectively improved, the rigidity at the edge portion 7 on the outer side in the tire width direction of the rib-like land portion 3 is not sufficiently improved, and therefore, uneven wear may not be effectively suppressed. There is. On the other hand, when the tire width direction length W _{1 of the} portion 10 having the maximum depth H ₁ is less than 0.1 times the tire width direction length W ₂ of the rib-like land portion 3, the rib-like land portion. Although the rigidity at the edge portion 7 on the outer side in the tire width direction 3 is effectively secured and uneven wear is suppressed, there is a possibility that the traction performance on the wet road surface due to the sipe 4 is not sufficiently improved.

In addition, the length W ₃ of the sipe 4 in the tire width direction is preferably 0.80 or more times the length W ₂ of the rib-like land portion 3 in the tire width direction. This is because, when the tire width direction length W ₃ of the sipe 4 is less than 0.80 times the rib-like land portion 3 in the tire width direction length W ₂ is also disposed sipe 4, wet road This is because the traction performance may not be sufficiently improved. At this time, the depth of the sipe 4 is preferably 0.30 or more times the depth of the circumferential grooves 2 and 2 sandwiching the rib-like land portion 3. Because, when the depth of the sipe 4 is less than 0.30 times the depth of the circumferential grooves 2 and 2 sandwiching the rib-like land portion 3, even if the sipe 4 is provided, the traction on the wet road surface This is because the performance may not be improved sufficiently. When the depths of the two circumferential grooves 2 and 2 sandwiching the rib-like land portion 3 are different, the depth of the sipe 4 is 0 of the depth of the circumferential groove 2 having a larger depth. It is preferably 30 times or more.

  Moreover, it is preferable that the tire circumferential direction length of the sipe 4 is less than 1.5 mm. This is because when the tire circumferential length of the sipe 4 is 1.5 mm or more, the rib-like land portion 3 is largely divided in the tire circumferential direction, uneven wear due to heel and toe wear occurs, and the rib-like land This is because the rigidity of the portion may be reduced, and the steering stability may be deteriorated. In general, the sipe function can be secured, and the technically manufacturable length of the sipe is about 0.5 mm.

In addition, since heavy load tires usually have a large flatness and high belt rigidity, the rotation of the belt portion due to the driving force being applied when rolling the tire load and the tread portion that is in contact with the road surface. As shown in FIG. 3, the friction causes a difference in displacement between the belt portion and the tread portion, and the tread portion falls excessively and deforms. As a result, since the driving force burden per unit area of the tread portion increases, a slip phenomenon occurs on the road surface of the block land portion, and the wear amount of the block land portion increases due to the slip phenomenon.
Here, the inventor believes that the increase in belt rigidity reduces the area where the tread surface contacts the road surface, resulting in an excessive increase in the circumferential shear force when the tread is kicked, which causes sliding wear. It was found that this led to a decline. FIG. 4 shows the driving force of the circumferential shear force (the driving force acting on the tire contact surface) from the time of stepping to the time of kicking out at an arbitrary position of the block land portion in contact with the road surface when the driving force is loaded. The change from no load is shown. In the tire of the prior art, as indicated by the solid line, the circumferential shear force hardly changes when the driving force is not applied when the pedal is depressed, and then monotonously increases when the tire is kicked. The sum of these forces generated from the time of stepping to the time of kicking (the integrated value of the circumferential shear force generated from the time of stepping to the time of kicking) accelerates the vehicle as a force acting on the tire shaft, but the contact area has decreased. In this case, the decrease in the integrated value due to the decrease in the area is compensated by the rapid change from the time of stepping per unit area to the time of kicking, so the circumferential shear force at the time of kicking increases and wear resistance is increased. descend. As shown by a broken line in FIG. 4, it is possible to compensate for this by reducing the circumferential shear force at the time of kicking by generating a circumferential shear force (change from when no driving force is applied) from the time of depression. As a result of intensive research based on the idea that it is possible, as shown in FIG. 5, the next block land portion is caused by the reaction of lifting due to the increase in shear deformation of the block land portion that has already been stepped on, which occurs when driving force is applied. It has been found that an increase in deformation that is pressed against the road surface side can efficiently generate a force at the time of depression, and can exhibit the characteristics shown by the broken line in FIG. It has also been found that this phenomenon can be effectively exerted by reducing the tire circumferential distance between the block land portions, but when the tire circumferential distance between the block land portions is made closer, as shown in FIG. The contact between the block land parts generates a force in the same direction as the driving force at the time of kicking and the wear resistance is reduced, so the influence of contact between the block land parts in the tire circumferential direction is eliminated. However, as a result of searching for a configuration that can effectively use the action between the block land portions, the following configurations were found.

The tire having the configuration found by the inventor extends in the tire circumferential direction to the land portion between the rib-shaped land portions 3 and 3 having the above-described sipes, that is, the land portion on the inner side in the tire width direction of the rib-shaped land portion 3. By arranging a plurality of circumferential grooves 2 and a plurality of transverse grooves 20 communicating two adjacent circumferential grooves 2, 2, a plurality of block land portion rows composed of a plurality of block land portions 12 13, the extending direction of the groove 14 between the block land portions adjacent to each other in the tire width direction is inclined with respect to the tire width direction and the tire circumferential direction. adjacent than distance d ₁ between the block land portions of a tire distance d ₂ between the block land portions adjacent in the tire width direction is shorter. Between the block land portion rows 13 adjacent to each other in the tire width direction, the block land portions 12 constituting them are arranged to be shifted from each other in the tire circumferential direction, and between the block land portions adjacent to each other in the tire width direction. The extending direction of the groove portion 14 is inclined with respect to the tire width direction and the tire circumferential direction, and the block land portion distance d adjacent in the tire width direction is greater than the block land portion distance d ₁ adjacent in the tire circumferential direction. ₂ is short, the groove portion 14 between the block land portions adjacent to each other in the tire width direction has the groove 14 between the block land portions adjacent to each other in the tire width direction while suppressing the bulging component of rubber due to contact between the block land portions 12 adjacent to each other in the tire peripheral direction. By utilizing the fact that the distance between the block land portions is short and the inclination between the block land portion and the tire width direction, as shown in FIG. It can be. Thereby, the gradient of the circumferential shearing force from the time of depression to the time of kicking becomes small, and sliding wear can be effectively suppressed. From these, in the rib-like land portion 3 located on the shoulder side, uneven wear due to river wear is suppressed for the reasons described above, and the block land portion row sandwiched between the rib-like land portions 3 and 3 In FIG. 13, since uneven wear due to sliding wear is suppressed, the wear resistance of the entire tire is improved, and the tire life until the tire is discarded can be increased.
In addition, it is preferable that the block land portion 12 adjacent in the tire width direction is disposed with a half pitch shift in the tire circumferential direction. This is because the block land portion 12 is arranged with a half-pitch shift, so that the deformation force that collapses and deforms can be effectively transmitted by the block land portion 12 adjacent in the tire width direction when rolling the tire. This is because it is possible to reduce the driving force burden per unit area of the tread portion 1 and prevent wear due to the slip phenomenon on the road surface of the block land portion 12. In this way, the gradient of the tire circumferential shearing force from stepping on to kicking out becomes small, and the shearing force at the time of kicking that causes sliding wear is reduced, so that sliding wear is reduced.

  In addition, from the viewpoint of more effectively suppressing sliding wear, the inclination angle of the groove portion 14 between the block land portions adjacent to each other in the tire width direction with respect to the tire circumferential direction is in a range of 15 ° to 70 °. It is preferable to do. Further, from the viewpoint of the interaction between the block land portions as described above, and from the viewpoint of maintaining the interaction until the end of wear, the groove depth of the groove portion 14 between the block land portions adjacent to each other in the tire width direction is the circumferential direction. It is preferable to be in the range of 60 to 100% of the groove depth of the groove 2A. Here, the configuration of the tread portion 1 of the tire according to the present invention is not limited to the configuration shown in FIG. 1, and other configurations may be adopted as long as the above-described conditions are satisfied. . For example, as shown in FIG. 7, the length of the cross-section in the tire width direction of the block land portion 12 is temporarily increased from the tire circumferential direction end portions 15 and 15 to the center portion 16 and then shortened. Is also possible.

  Furthermore, as shown in FIGS. 8 and 9, the length of the cross-section in the tire width direction of the block land portion 12 increases from the tire circumferential direction both ends 15, 15 of the block land portion 12 to the central portion 16 of the block land portion 12. It is preferable. As a result of earnest research on the wear of the block land portion when the tire having the block land portion, in particular, a heavy duty tire having a high flatness ratio is used as a drive wheel, the inventors have obtained the following knowledge. That is, if the block land portion is pressed horizontally against the road surface and brought into contact with the ground, the stress caused by the incompressibility of the rubber is applied to the stepping end and the kicking end of the block land portion as shown in FIG. In the case of kicking in which tread wear occurs due to slippage of the tread portion, the tread portion is pressed obliquely against the road surface by the belt, so the stress caused by the incompressibility of the rubber is shown in FIG. As shown, it is loaded at the center of the block land. In particular, in the case of tires with a high flatness ratio and high belt rigidity, the tread part is pressed more strongly against the road surface, so the stress caused by the incompressibility of the rubber is greatly applied to the central part of the block land part. It becomes. The force generated along with the compression deformation is loaded in the same direction as the traveling direction of the vehicle and promoted by the driving force of the engine torque, leading to an increase in sliding wear. Therefore, as described above, by increasing the length of the cross section in the tire width direction of the block land portion 12 from the both ends 15 and 15 in the tire circumferential direction of the block land portion 12 to the center portion 16 of the block land portion 12, When the land portion 12 is grounded obliquely with respect to the road surface, compressive stress is concentrated in the central region of the block land portion 12 as shown in FIG. As shown in FIG. 9, the block that is inclined with respect to the circumferential direction of the tire on the side of the kicking end of the block land portion 12, even if a force that tends to deform from the kicking end 17 toward the stepping end 18 is generated. A force Q that causes the wall portion of the land portion 12 to bulge in the normal direction is generated. At this time, the component force R of the force Q to be swelled is generated in the opposite direction from the left and right wall portions of the block land portion 12, and is mutually offset within the block land portion 12. P resists the force that the rubber in the central region of the block land portion 12 tends to deform from the kicking end 17 toward the stepping end 18. As a result, excessive deformation of the block land portion 12 is suppressed, and uneven wear and sliding wear of the block land portion 12 can be prevented. Moreover, as shown in FIG. 11, the deformation | transformation (solid line) at the time of applying a driving force to the block land part 12 of the tire according to this invention which does not apply the above-mentioned block shape, and this invention which applied the block shape as mentioned above When the driving force is applied to the block land portion 12 in the tire according to the above (the dotted line), the block land portion 12 of the latter tire has a block kicking end by a mechanism similar to that at the time of kicking when stepped on. The deformation of the rubber to the side is suppressed, but due to the incompressibility of the rubber, the suppressed deformation acts in the direction of increasing the lifting of the kicking end 17 of the block land portion 12 that has already been stepped on. As a result, since the shear deformation of the block land portion 12 to be stepped on next increases, the shear force at the time of stepping increases as shown in FIG. The effect of becoming smaller can be produced synergistically. At this time, the ratio of the tire width direction length B of the central portion 16 of the block land portion 12 to the tire width direction length A of the tire circumferential direction end portion 15 of the block land portion 12 is 1: 3 to 1: It is preferable to be in the range of 1.5. This is because if the ratio of the length is out of the range, the deformation of the block land portion 12 cannot be effectively prevented when the block land portion 12 is grounded obliquely, etc. This is because sliding wear may occur.

  In addition, the same block land portion 12 faces the same circumferential groove 2, and the groove portion 14 between the block land portions adjacent to each other in the tire width direction is opposite to the tire equatorial plane when viewed in the tire circumferential direction. It is preferable that the opening angle is in the direction. Because, when the extending direction of the groove portion 14 between the block land portions adjacent to each other in the tire width direction is the same, it is possible to effectively cope with input from a certain direction and prevent sliding wear. This is because there is a possibility that sliding wear cannot be prevented without effectively dealing with input from other directions. In addition, the inclination in the extending direction of the groove portion adjacent to the tire width direction and the inclination of the block land portion 12 caused by increasing the cross-sectional length in the tire width direction of the central portion 16 of the block land portion 12 face each other. By configuring the block pattern without generating useless space in the tire width direction, it is possible to effectively demonstrate wear resistance performance without damaging the configuration and operation of both, Pattern design by combination with second ribs, shoulder ribs, lugs and the like is also facilitated.

In addition, it is preferable that the tire circumferential length d ₃ of the block land portion 12 is in the range of 1.0 to 2.5% of the tire circumferential length. To effectively bring out the effects of the block land portion 12 of the present invention as described above, it is suitable that the tire circumferential direction length d ₃ of the block land portion 12 is less than 2.5% of the tire circumferential length. This is because if this value exceeds 2.5%, the block shear rigidity will increase excessively, and there is a possibility that the block land portion 12 that has already been stepped on may not be sufficiently lifted. It is. However, the tire circumferential direction length d ₃ of the block land portion 12 is not more than 2.5% of the tire circumferential length, if it is less than 1.0%, the rigidity of the block land portion 12 is too decreased When the driving force is applied to the block land portion 12, the block land portion 12 is excessively sheared and deformed, and the sliding wear cannot be sufficiently suppressed. Therefore, by setting the range of 1.0 to 2.5% of the tire circumference the tire circumferential direction length d ₃ of the block land portion 12, the rigidity of the block land portion 12 is ensured, and, above the block land Since the effect of the portion 12 is effectively exhibited, there is a possibility that the wear resistance can be prevented from being reduced.

In addition, the ratio of the distance d ₂ between the block land portions adjacent in the tire width direction to the distance d ₁ between the block land portions adjacent in the tire circumferential direction may be in the range of 1: 0.85 to 1: 0.3. More preferably, it exists in the range of 1: 0.7-1: 0.4. When the ratio of the distance d ₂ between the block land portions adjacent in the tire circumferential direction to the distance d ₁ between the block land portions adjacent in the tire circumferential direction is larger than 1: 0.3, the block adjacent in the tire circumferential direction even enough that the land portion distance d _1, is too short distance d ₂ between the block land portions adjacent in the tire width direction. Therefore, the block land portions 12 adjacent to each other in the tire width direction come into contact with each other at the time of tire load rolling, and the deformation force that collapses and deforms is not effectively transmitted to the block land portions 12 adjacent to the tire width direction. There is a possibility that the shear force in the land portion 12 is not effectively dispersed and sliding wear is caused. On the other hand, for the distance d ₁ between the block land portions adjacent in the tire circumferential direction, the ratio of the distance d ₂ between the block land portions adjacent in the tire width direction is 1: is smaller than 0.85, adjacent in the tire width direction even enough that distance d ₂ between the block land portions is, becomes too short distance d ₁ between the block land portions adjacent in the tire circumferential direction. Therefore, when the block land portion 12 contacts the road surface, the block land portions 12 come into contact with each other in the tire circumferential direction, and deformation due to rubber bulging shown in FIG. there's a possibility that.

Further, the ratio of the distance d ₁ between the block land portions adjacent in the tire circumferential direction to the tire circumferential direction length d ₃ of the block land portion 12 is preferably in the range of 1: 0.25 to 1: 0.05. More preferably, it is in the range of 1: 0.17 to 1: 0.07. With respect to the tire circumferential direction length d ₃ of the block land portion 12, the circumferential ratio of the distance d ₁ between the block land portions adjacent in the direction is 1: greater than 0.05, the block land portion when the tire is rolling under load When 12 falls down and deforms, the block land portion 12 adjacent in the tire circumferential direction approaches too much. Therefore, as shown in FIG. 6, when the block land portion 12 of the tread portion 1 that is in contact with the road surface is pressed and deformed, the block land portion 12 adjacent to the tire circumferential direction in the center of the tread portion 1. They come into contact with each other, and the block land portion 12 outside them is pushed outward in the tire circumferential direction, and the block land portion 12 collapses excessively in both directions of the rotation direction of the tire and the direction opposite to the rotation direction. Will be. As a result, since the force in the same direction as the direction in which the driving force is applied at the kicking end 17 increases, there is a possibility of causing sliding wear due to the falling deformation. On the other hand, with respect to the tire circumferential direction length d ₃ of the block land portion 12, the ratio of the distance d ₁ between the block land portions adjacent in the tire circumferential direction is 1: smaller than 0.25 is adjacent in the tire circumferential direction Since the block land portion 12 is too far away, the shear force of the block land portion 12 adjacent to the tire circumferential direction cannot be distributed in a well-balanced manner using the shear force of the kicking end 17 of the block land portion 12. Again, there is a possibility of causing sliding wear.

Furthermore, the distance d ₂ between the block land portions adjacent to each other in the tire width direction is preferably in the range of 1.0 to 5.0 mm, and more preferably in the range of 1.5 to 3.5 mm. When the block land portion distance d ₂ exceeds 5.0 mm, the block land portion distance d ₂ adjacent in the tire width direction becomes too long. As a result, the deforming force that collapses and deforms cannot be transmitted to the block land portion 12 adjacent in the tire width direction, causing excessive tilt deformation in the tire circumferential direction, resulting in the slip of the block land portion 12. Wear may occur. On the other hand, if the inter-block land portion a distance d ₂ is less than 1.0mm, the distance d ₂ between the block land portions adjacent in the tire width direction is too short. Therefore, at the time of tire load rolling, the block land portions 12 adjacent to each other in the tire width direction come into contact with each other, and the deformation force that collapses and deforms can be effectively transmitted to the block land portions 12 adjacent in the tire width direction. However, there is a possibility that excessive falling deformation is caused, and that wear due to slippage of the block land portion 12 is also caused.

In addition, the distance d ₁ between the block land portions adjacent to each other in the tire circumferential direction is preferably in the range of 3.0 to 10.0 mm, more preferably in the range of 4.0 to 8.0 mm. If the distance d ₁ between the block land portions adjacent in the tire circumferential direction exceeds 10.0mm, the distance d ₁ between the block land portions adjacent in the tire circumferential direction is too long. As a result, the ground pressure of the block land portion 12 may increase excessively, and the wear resistance may decrease. On the other hand, if the distance d ₁ between the block land portions adjacent in the tire circumferential direction is less than 3.0mm, the distance d ₁ between the block land portions adjacent in the tire circumferential direction is too short. Therefore, when the block land portion 12 comes into contact with the road surface, the block land portion 12 contacts in the tire circumferential direction, and deformation due to the swelling of the rubber shown in FIG. 6 may occur, resulting in a decrease in wear resistance.

  In addition, as shown in FIGS. 12 and 13, the block land portion 12 is provided with a sipe 4 that communicates the two circumferential grooves 2 and 2 adjacent to the block land portion 12 in the tire width direction. It is preferable to become. Thus, by providing the kicking end 17 again, the grip force of the block land portion 12 can be improved as a whole, and the torque from the engine can be efficiently converted into driving force. . At this time, the sipe 4 may be bent or refracted in the block land portion 12.

  Moreover, it is preferable that the sipe 4 provided in the block land portion 12 opens in the circumferential groove 2 at the central portion 16 of the block land portion 12. This is because when the sipe 4 is open in a region off the central portion 16 of the block land portion 12, the grip force as a driving force cannot be distributed in a balanced manner within the block land portion 12, This is because it may not be possible to efficiently convert the torque to drive force.

  Further, the tire circumferential length of the sipe 4 provided in the block land portion 12 is preferably in the range of 5 to 20% of the groove depth (diameter depth) of the lateral groove 20, and more preferably 7 to It is in the range of 18%. When the tire circumferential direction length of the sipe 4 is less than 5% of the groove depth of the lateral groove 20, the tire circumferential direction length of the sipe 4 becomes too short. As a result, as in the case where the sipe 4 is not disposed on the block land portion 12, the grip force decreases from the step-in end 18 toward the kick-out end 17, and the effect of disposing the sipe 4 may be lost. is there. On the other hand, when the tire circumferential direction length of the sipe 4 exceeds 20% of the groove depth of the lateral groove 20, the tire circumferential direction length of the sipe 4 becomes too long. As a result, it becomes impossible to transmit force due to the reaction between the block land portions 12 separated by the sipe 4 in the block land portion 12, thereby causing excessive falling deformation and possibly causing sliding wear. There is. In order to obtain a sufficient effect until the end of wear, the groove depth of the sipe 4 of the block land portion 12 is preferably 60 to 100% of the groove depth of the lateral groove 20.

  The above description shows only a part of the embodiment of the present invention, and these configurations can be combined alternately or various changes can be made without departing from the gist of the present invention. For example, in a tire having the configuration shown in FIGS. 1, 7, 8, 12, and 13, two blocks of land blocks 13 are set as one unit, and at least one unit of block land portions 13 is arranged on the tread surface. However, one unit can be arranged on the tread portion tread as three or more block land portion rows 13. Further, as shown in FIG. 14, the drainage performance can be further improved by using the shallow groove 19 in the region where the sipe 4 is provided. Further, when the sipe of the rib-like land portion 3 is deformed by an input in the tire circumferential direction at the time of tire load rolling, the portion 10 having the maximum groove depth of the groove bottom 6 of the sipe 4 and the minimum groove depth. From the viewpoint of dispersing the stress concentrated on the connection region 21 with the portion 11 having, and preventing the occurrence of cracks (tearing), the following configuration is preferable. That is, it is preferable that the inclination angle X of the connection region 21 with respect to the tire width direction (the tire axial direction) is in the range of 110 to 160 ° as an obtuse angle. This is because when the inclination angle X exceeds 160 °, the rigidity of the edge portion 7 on the outer side in the tire width direction of the rib-shaped land portion 3 is not sufficiently improved (stabilization of the rigidity difference in the rib-shaped land portion 3 is ensured). This is because there is a possibility that the effect of suppressing the uneven wear by reducing the rigidity difference in the rib-like land portion 3 may not be sufficiently exhibited. On the other hand, when the inclination angle X is less than 110 °, the stress concentrated on the connection region 21 cannot be effectively dispersed, and a crack may occur in the connection region 21. Furthermore, the enlarged portion 9 of the sipe 4 in the illustrated example has a circular flask shape as seen in the tire circumferential cross section, but the shape is not limited to this, and an elliptical shape or other shapes It can also be. However, in the case of other shapes having corners, from the viewpoint of preventing the rib-like land portion 3 from being deformed at the time of tire load rolling and generating cracks at the enlarged portion 9, such corners are used. The part preferably has a curvature.

  Next, a conventional tire having a sipe with a constant depth in the rib-like land portion and having an enlarged portion at the bottom of the groove, but not having an enlarged portion, but other configurations are similar to the pneumatic tire of the present invention The pneumatic tire (comparative example tire) having the structure and the pneumatic tire (example tires 1 to 3) of the present invention were respectively prototyped as heavy duty pneumatic tires having a tire size of 11R / 22.5, and performance evaluation was performed. Since it went, it demonstrates below.

  The conventional tire, the comparative example tire, and the example tires 1 to 3 each include a tread portion having the configuration shown in FIG. The tread portion has a plurality of rib-like land portions and a plurality of block land portion rows surrounded by the plurality of rib land portions, and in the block land portion rows, the extension of the groove portion between the block land portions adjacent to each other in the tire width direction. The direction is inclined with respect to the tire width direction and the tire circumferential direction, and the distance between the block land portions adjacent to each other in the tire width direction is shorter than the distance between the block land portions adjacent to each other in the tire circumferential direction. The sipes provided on the rib-like land portions of the conventional tire, the comparative tire, and the example tires 1 to 3 are shown in FIGS. 16 (a) and 16 (b), FIGS. 17 (a) and 17 (b), respectively. 18 (a) and (b), FIGS. 19 (a) and 19 (b), and FIGS. 20 (a) and 20 (b). The sipe of the conventional tire has a tire width direction length of 0.7 mm, a tire width direction length of 20 mm, a depth of 16 mm, and a flask-like enlarged portion having a diameter of 2 mm at the groove bottom. The sipe of the comparative example tire has a tire width direction length of 0.7 mm, a tire width direction length of 20 mm, a maximum groove depth of 16 mm, and a minimum groove depth of 13 mm. The portion having the maximum groove depth is a tire. The portion on the equator plane side and having the minimum groove depth is on the shoulder side. Further, the inclination angle X of the connecting region between the portion having the maximum groove depth and the portion having the minimum groove depth with respect to the tire width direction is 150 °. The sipe of Example tire 1 has a tire width direction length of 0.7 mm, a tire width direction length of 20 mm, a maximum groove depth of 16 mm, a minimum groove depth of 13 mm, and the portion having the maximum groove depth is The portion on the tire equatorial plane side and having the minimum groove depth is on the shoulder side. Further, the inclination angle of the connecting region between the portion having the maximum groove depth and the portion having the minimum groove depth with respect to the tire width direction is 150 °, and the portion having the minimum groove depth has a flask shape with a diameter of 2 mm. It has an enlarged part. The sipe of Example tire 2 has a tire width direction length of 0.7 mm, a tire width direction length of 20 mm, a maximum groove depth of 16 mm, a minimum groove depth of 13 mm, and the portion having the maximum groove depth is The portion on the tire equatorial plane side and having the minimum groove depth is on the shoulder side. Further, the inclination angle of the connecting region between the portion having the maximum groove depth and the portion having the minimum groove depth with respect to the tire radial direction is 150 °, and the portion having the maximum groove depth has a flask-like shape having a diameter of 2 mm. Has an enlarged part. The sipe of Example tire 3 has a tire width direction length of 0.7 mm, a tire width direction length of 20 mm, a maximum groove depth of 16 mm, a minimum groove depth of 13 mm, and the portion having the maximum groove depth is The portion on the tire equatorial plane side and having the minimum groove depth is on the shoulder side. The inclination angle of the connecting region between the portion having the maximum groove depth and the portion having the minimum groove depth with respect to the tire radial direction is 150 °, and the portion having the minimum groove depth and the maximum groove depth are included. The part has a flask-like enlarged part with a diameter of 2 mm.

  The traction performance on the wet road surface is as follows. Each of these test tires is attached to a rim of size 7.5 × 22.5 to form a tire wheel, which is attached to a driving wheel of a tractor vehicle used for the test, and has an air pressure of 900 kPa (relative pressure). ), Tire load load of 8.34kN (per one) was applied, and a start acceleration test was performed on a wet road surface condition with a water film of 2mm on a test course laid with an iron plate. The time was measured, the time required for the comparative tire was indexed as a reference value, and relative values were obtained for the other tires and evaluated by comparing them. In addition, it shows that it is excellent in the traction performance in a wet road surface, so that a numerical value is large, and the result is shown in Table 1.

  Uneven wear resistance is confirmed by visually checking if uneven wear due to river wear occurs after running the above vehicle on the test road until the wear rate of the rib-like land reaches 70%. It was evaluated by doing. The results are shown in Table 1.

  Crack resistance refers to whether or not cracks have occurred in the portion of the sipe having the minimum groove depth after running the above vehicle on the test road until the wear rate of the rib-like land reaches 40%. After that, after traveling until the wear rate of the rib-like land reaches 70%, it is visually determined whether or not cracks have occurred in the portion having the maximum groove depth of the sipe. Confirmed and evaluated. The results are also shown in Table 1.

  As is clear from the results in Table 1, compared to the conventional tires, the comparative tires and the example tires 1 to 3 were suppressed from uneven wear due to riverware. The example tires 1-3 maintained the traction performance on the wet road surface effectively as in the conventional tires and the comparative example tires. Further, in the example tire 1 in which the enlarged portion is provided in the portion having the minimum groove depth of the sipe, generation of cracks in the portion having the minimum groove depth was effectively suppressed. On the other hand, in the example tire 2 in which the enlarged portion is provided in the portion having the maximum groove depth of the sipe, occurrence of cracks in the portion having the maximum groove depth was effectively suppressed. Further, in the example tire 3 in which the enlarged portion is provided in both the portion having the maximum groove depth and the portion having the minimum groove depth of the sipe, the portion having the maximum groove depth and the portion having the minimum groove depth of the sipe Both cracks were effectively suppressed.

  As is apparent from the above, according to the present invention, in the tire having a sipe in the rib-like land portion, by optimizing the sipe shape, the wear resistance is assumed on the premise of maintaining the traction performance on the wet road surface. It is also possible to provide a tire with improved crack resistance.

(A) is a development view of a part of a tread portion of a typical tire according to the present invention, (b) is a cross-sectional view taken along line II in (a), and (c) is (a) 2 is a cross-sectional view in the tire circumferential direction of the rib-like land portion in (), and (d) is a perspective view of the rib-like land portion in (a). (A) And (b) is sectional drawing of the lateral groove of the other tire according to this invention. It is the figure which showed the relationship between the presence or absence of a driving force load, and the movement position of a tread part. It is the figure which showed the shear force from the road surface at the time of applying driving force. It is the figure which showed the deformation | transformation in the adjacent block land part when driving force is loaded. It is the figure which showed the deformation | transformation in a block land part when the block land part adjacent to a tire circumferential direction is approaching too much. FIG. 6 is a development view of a part of a tread portion of another tire according to the present invention. FIG. 6 is a development view of a part of a tread portion of another tire according to the present invention. It is a perspective view of the block land part shown in FIG. (A) is the figure which showed the block land part which pressed horizontally with respect to the road surface, and was earth | grounding, (b) is the block land part which pressed diagonally with respect to the road surface, and is earthing | grounding. FIG. It is the figure which showed the deformation | transformation in the adjacent block land part when driving force is loaded. FIG. 6 is a development view of a part of a tread portion of another tire according to the present invention. FIG. 6 is a development view of a part of a tread portion of another tire according to the present invention. It is a perspective view of the rib-like land part of the other tire according to this invention. FIG. 3 is a development view of a part of a tread portion of a tire used in an example. (A) is a tire width direction sectional view (II-II line sectional view) of a rib-like land portion of a conventional tire, and (b) is a tire circumferential direction sectional view of a rib-like land portion of a conventional tire (III-). FIG. (A) is tire width direction sectional drawing (II-II sectional view) of the rib-like land part of a comparative example tire, (b) is tire circumferential direction sectional drawing (III-) of the rib-like land part of a comparative example tire. FIG. (A) is a tire width direction sectional view (II-II line sectional view) of a rib-like land part of example tire 1, and (b) is a tire circumferential direction sectional view of a rib-like land part of example tire 1 ( It is a III-III line sectional view). (A) is a tire width direction sectional view (II-II line sectional view) of a rib-like land part of example tire 2, (b) is a tire circumferential direction sectional view of a rib-like land part of example tire 2 ( It is a III-III line sectional view). (A) is a tire width direction sectional view (II-II line sectional view) of a rib-like land part of example tire 3, (b) is a tire circumferential direction sectional view of a rib-like land part of example tire 3 ( It is a III-III line sectional view).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2, 2A Circumferential groove | channel 3 Rib-like land part 4 Sipe 5 Tread part tread surface 6 Sipe groove bottom 7 Edge part 8 of rib-like land part outer side of tire width direction Central part 9 of rib-like land part Expansion part 10 A portion 11 having the maximum groove depth 12 A portion having the minimum groove depth 12 Block land portion 13 Block land portion row 14 Groove portion 15 between block land portions adjacent to each other in the tire width direction Tire circumferential direction end portion 16 of the block land portion Central part 17 of block land part Extrusion end 18 Depression end 19 Shallow groove 20 Lateral groove 21 Connection area

Claims (11)

A tire having one or more rows of rib-like land portions in the tread portion and having sipes on the rib-like land portions,
The sipe has a depth at least at the end on the shoulder side that is smaller than the depth of the remaining portion,
A tire characterized in that an enlarged portion having a tire circumferential direction length larger than an opening width of the sipe in a tread portion tread is provided at least at a part of the groove bottom of the sipe.   The tire according to claim 1, wherein the enlarged portion is provided in a groove bottom portion having a maximum depth.   The tire according to claim 1 or 2, comprising the enlarged portion in a groove bottom portion having a minimum depth.   The tire according to any one of claims 1 to 3, wherein in the sipe, the minimum depth is in a range of 0.50 to 0.95 times the maximum depth.   The tire width direction length of the portion having the maximum depth of the sipe is in a range of 0.1 to 0.9 times the length of the rib-shaped land portion in the tire width direction. The tire according to one item.   The tire according to any one of claims 1 to 5, wherein the length of the sipe in the tire width direction is 0.80 times or more the tire width direction length of the rib-like land portion.   The tire according to any one of claims 1 to 6, wherein a depth of the sipe is 0.30 or more times a depth of a circumferential groove sandwiching the rib-like land portion. By arranging a plurality of transverse grooves communicating with two adjacent circumferential grooves, a plurality of block land portions are partitioned,
Among the block land portion rows, in at least two block land portion rows adjacent to each other across the circumferential groove, the block land portions constituting the block land portion rows adjacent to each other across the circumferential groove are tires. The groove extending direction between the block land portions adjacent to each other in the tire width direction is inclined with respect to the tire width direction and the tire circumferential direction, and is adjacent to the tire circumferential direction. The tire according to any one of claims 1 to 7, wherein a distance between the block land portions adjacent in the tire width direction is shorter than a distance between the block land portions.   The tire according to claim 8, wherein a length of a cross section of the block land portion in a tire width direction increases from both ends of the block land portion in a tire circumferential direction to a center portion of the block land portion.   The ratio of the distance between block land portions adjacent in the tire width direction to the distance between block land portions adjacent in the tire circumferential direction is in a range of 1: 0.85 to 1: 0.3. Tire described in.   The ratio of the distance between block land portions adjacent in the tire circumferential direction to the tire circumferential direction length of the block land portion is in a range of 1: 0.25 to 1: 0.05. The tire according to claim 1.

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