JP5364317B2 - tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire maintaining steering stability and improved in wear resistance on a wet road surface by optimizing the shape of lateral grooves in outer block land section rows. <P>SOLUTION: A plurality of block land section rows made up of a large number of block land sections 4 are dividedly formed in a tread section 1. In middle block land section rows 6 on a tire equatorial plane side, the block land sections 4 constituting them are deviatedly placed from each other in the tire circumferential direction. The extending direction of a groove section 7 between the block land sections adjacent to each other in the tire width direction is tilted to the tire width direction and the tire circumferential direction. The distance between the block land sections adjacent to each other in the tire width is shorter than the distance between the block land sections adjacent to each other in the tire circumferential direction. In the lateral grooves 3A between the block land sections adjacent to each other in the tire circumferential direction in the outer block land section rows 8, at least the depth thereof at a shoulder side end portion is smaller than the depth of residual portions. The tire circumferential length of the lateral grooves 3A is not more than 10% of the groove depth of the lateral grooves 3A. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  According to the present invention, a plurality of block land is provided in the tread portion by disposing a plurality of tire circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves communicating with two adjacent tire circumferential grooves. The present invention relates to a tire, in particular, a heavy-duty tire, in which a plurality of block land rows are formed, and the wear resistance is improved on the premise of maintaining steering stability on the wet road surface of the tire.

  In general, a heavy duty tire increases the flatness of the tire and increases the belt rigidity in order to support a considerable weight. Further, in order to enable traveling under various traveling conditions, a tread pattern in which block land portions are arranged in the entire tread portion is often used.

  In a heavy duty tire adopting such a tread pattern, the load load is higher than that of a general vehicle tire, and therefore, uneven wear due to heel and toe wear tends to occur during traveling in proportion to the load applied. . Heel and toe wear is caused by excessive deformation of the block land during rolling of the tire load, and the amount of wear at the stepping end (the part that makes contact with the ground first) is reduced, and the tire end in the tire circumferential direction (the last is the grounding) (Part to be) means wear that increases the amount of wear. Therefore, there is a problem that a difference in wear occurs mainly at both ends of the block land portion in the tire circumferential direction, and the wear life of the tire is shortened.

  Many countermeasures have been tried as countermeasures against such uneven wear. Among them, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-171318, a portion of the lateral groove that defines the block is made shallower, that is, by providing a bottom raised portion in the lateral groove, the tire circumferential direction of the block land portion It is said that a method for preventing the uneven wear caused by the falling deformation is effective by increasing the stress against the falling deformation to suppress the increase of the driving force load per unit area.

  Heavy load tires mounted on trucks and buses have a high flatness ratio and high belt rigidity, so that when the tire is rolling, the belt rotates due to the driving force being applied, and the road surface is grounded. Due to the friction of the tread portion, a difference in displacement occurs between the belt portion and the tread portion as shown in FIG. 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. In the tire described in Japanese Patent Laid-Open No. 6-171318, although there is a certain effect in preventing uneven wear, the slipping phenomenon of the block land portion at the time of tire load rolling cannot be sufficiently suppressed. The increase in the amount of wear in the block land due to the above cannot be suppressed, and there remains a problem in terms of wear resistance. Also, in general, it is possible to effectively suppress the amount of wear of the block land portion by increasing the rigidity of the rubber constituting the block land portion and suppressing excessive falling deformation of the block land portion. Further, the rigidity of the block land portion becomes too high, and there is a possibility that the block land portion may be broken due to baldness or cracks when rolling the tire.

  Therefore, in order to solve such problems of the prior art, the applicant of the present application is adjacent to the tread portion in the international application PCT / JP2008 / 59826 with a plurality of circumferential grooves extending in the tire circumferential direction. A tire in which a plurality of block land portions composed of a plurality of block land portions are defined by disposing a plurality of lateral grooves communicating with two circumferential grooves, with the circumferential grooves interposed therebetween. The block land portions constituting the block land portion rows adjacent to each other are arranged so as to be shifted from each other in the tire circumferential direction, and the extending direction of the groove portion between the adjacent block land portions in the tire width direction is the tire width. The tire which inclines with respect to the direction and the tire circumferential direction, and the distance between the block land parts adjacent to a tire width direction was shorter than the distance between the block land parts adjacent to a tire circumferential direction was proposed. By adopting the above configuration, the negative rate of the tread part is increased, the drainage performance is improved, the steering stability on the wet road surface is secured, and the excessive deformation of the block land part is suppressed, and the sliding wear It is possible to suppress uneven wear caused by the wear, and the wear resistance is improved. Details will be described below.

  As a result of the decrease in the area where the tread surface contacts the road surface due to the increase in belt rigidity, the inventor has an excessive increase in the circumferential shear force at the time of kicking out the tread where sliding wear occurs. I found it connected. FIG. 2 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 any position of the block land portion in contact with the road surface when driving force is applied. 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. 2, 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 stepping on. As a result of intensive research based on the idea that it is possible, as shown in FIG. 3, the next block land portion is caused by the reaction of the lift due to the increased 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 can efficiently generate a stepping force and can exhibit the characteristics shown by the broken line in FIG. It has also been found that this phenomenon can be effectively demonstrated by bringing the tire circumferential distance between the block land portions closer, 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 the tire circumferential contact between the block land parts is eliminated. As a result of searching for a configuration that can effectively utilize the action between the block land portions, the configuration of the present invention was found. In the configuration of the present invention, between the two block land portion rows adjacent in the tire width direction, the block land portions constituting them are arranged to be shifted from each other in the tire circumferential direction, and adjacent to the tire width direction. The extending direction of the groove portion between the block land portions is inclined with respect to the tire width direction and the tire circumferential direction, and the distance between the block land portions adjacent in the tire width direction is larger than the distance between the block land portions adjacent in the tire circumferential direction. Since the distance is short, the groove portion between the block land portions adjacent to each other in the tire width direction is formed while the rubber bulging component (FIG. 4) due to contact between the block land portions adjacent to each other in the tire peripheral direction is suppressed. By utilizing the fact that the distance between the block land portions is short and the distance between the block land portions is short, it is possible to efficiently generate a driving force load when the vehicle is depressed. 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.

  However, since there is a demand for further extending the life of the tire, that is, further improving the wear resistance, an object of the present invention is to optimize the shape of the block land portion and the arrangement position thereof. An object of the present invention is to provide a tire with further improved wear resistance on the premise of maintaining steering stability on a wet road surface.

In order to achieve the above object, the present invention provides a tread portion with a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves communicating with two adjacent circumferential grooves. A tire in which a plurality of block land portions composed of a plurality of block land portions are partitioned and formed in a central block land portion row that is at least two block land portion rows adjacent to each other across the circumferential groove. The block land portions are configured to be shifted from each other in the tire circumferential direction, and the extending direction of the groove 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. The distance between the block land portions adjacent in the tire width direction is shorter than the distance between the block land portions adjacent in the tire circumferential direction, and the outer block land portion row on the outer side in the tire width direction of the central block land portion row. The transverse groove between the block land portions adjacent to each other in the tire circumferential direction has a depth at least at the end on the shoulder side smaller than the depth of the remaining portion, and the tire circumferential direction length of the transverse groove is the groove depth of the transverse groove. The minimum depth of the lateral groove between the block land portions adjacent to each other in the tire circumferential direction in the outer block land portion row is in a range of 0.4 to 0.8 times the maximum depth. For all the block land portions in the central block land portion row, the tire width direction length of the tire circumferential direction end portion of the block land portion is A, and the length in the tire width direction of the central portion of the block land portion is Where B is the ratio A / B is in the range of 1/3 to 1 / 1.5. 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. The “groove depth of the lateral groove” means the maximum groove depth of the lateral groove.

  Further, in the outer block land portion row, the tire width direction length of the portion having the maximum depth of the transverse groove between the block land portions adjacent in the tire circumferential direction is 0.4 to the tire width direction length of the block land portion. A range of 0.7 times is preferable.

  Furthermore, 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.

In addition, in the central block land portion row, the ratio d ₁ / d ₂ of the block land portion distance d ₁ adjacent in the tire circumferential direction to the block land portion distance d ₂ adjacent in the tire width direction is 1/0. The ratio d ₁ / d ₂ is preferably in the range of 1 / 0.7 to 1 / 0.4.

In addition, in the central block land portion row, the ratio d ₃ / d ₁ of the tire circumferential direction length d ₃ of the block land portion to the block land portion distance d ₁ adjacent in the tire circumferential direction is 1/0 . The ratio d ₃ / d ₁ is preferably in the range of 1 / 0.17 to 1 / 0.07.

  In the central block land portion row, the distance between the block land portions adjacent in the tire width direction is preferably 1.0 to 5.0 mm.

  Furthermore, in the central block land portion row, the distance between the block land portions adjacent in the tire circumferential direction is preferably 3.0 to 10.0 mm.

  Furthermore, it is preferable that a narrow groove that connects two circumferential grooves adjacent to the block land portion in the tire width direction is disposed in the block land portion.

  In addition, it is preferable that the narrow groove is opened to the circumferential groove at the center of the block land portion.

In addition, the tire circumferential length of the narrow groove is preferably in the range of 5 to 20% of the groove depth of the lateral groove. The central block land portion row may be composed of two block land portion rows.

  According to the present invention, by optimizing the shape of the lateral groove in the outer block land portion row, it is possible to provide a tire with improved wear resistance on the premise of maintaining steering stability on a wet road surface. Become.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 5 (a) is a developed view of a portion of the tread portion of a tire, FIG. 5 (b) is a sectional view taken along line I-I of the tread portion shown in Figure 5 (a). FIGS. 6A and 6B are cross-sectional views in the tire width direction of the lateral grooves in the outer block land portion row of the other tires according to the present invention. FIG. 7 is a development view of a part of the tread portion of the tire, and FIG. 8 is a development view 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. Figure 14 is a perspective view of the outer block land portion row other tire of that.

In this tire , as shown in FIG. 5A, a plurality of circumferential grooves 2 extending in the tire circumferential direction and a plurality of adjacent circumferential grooves 2 and 2 are communicated with the tread portion 1. By arranging the lateral grooves 3, a plurality of block land portion rows 5 composed of a large number of block land portions 4 are partitioned. Among the block land portion rows 5, in the central block land portion row 6 which is at least two block land portion rows 5 and 5 adjacent to each other across the circumferential groove 2, between the adjacent block land portion rows 5 and 5. The block land portions 4 constituting them are arranged so as to be shifted from each other in the tire circumferential direction, and the extending direction of the groove portion 7 between the block land portions adjacent to each other in the tire width direction is the tire width direction and the tire circumferential direction. The distance d ₂ between the block land portions adjacent in the tire width direction is shorter than the distance d ₁ between the block land portions adjacent to each other in the tire circumferential direction.
As described above, by adopting the above configuration, in the central block land portion row 6, while suppressing the rubber bulging component (FIG. 4) due to contact between the block land portions 4 adjacent in the tire circumferential direction, By utilizing the fact that the groove portion 7 between the block land portions adjacent in the tire width direction is inclined in the tire circumferential direction and the tire width direction and the distance between the block land portions is short, as shown in FIG. Due to the reaction between them, it is possible to efficiently generate a driving force burden at the time of depression. In addition, it is preferable that the block land portions 4 adjacent in the tire width direction are arranged with a half pitch shift in the tire circumferential direction. Because the block land portion 4 is arranged with a half-pitch shift, the deformation force that collapses and deforms at the time of tire load rolling can be effectively transmitted to the block land portion 4 adjacent in the tire width direction. 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 4. In this way, the gradient of the tire circumferential direction shear force from stepping on to kicking out becomes small, and the shearing force at the time of kicking in which sliding wear occurs becomes small, so that sliding wear is reduced. At this time, from the viewpoint of more effectively suppressing sliding wear, the inclination angle of the groove portion 7 between the block land portions adjacent in the tire width direction with respect to the tire circumferential direction in the extending direction may be 15 ° or more. preferable.

Further, in the tire according to the present invention, in the outer block land portion row 8 which is the block land portion row 5 on the outer side in the tire width direction of the central block land portion row 6, the tire circumferential direction length of the lateral groove 3A (that is, in the tire circumferential direction). The distance d ₁ ) between adjacent block land portions is 10% or less of the groove depth of the lateral groove 3A. In general, the block land portion on the shoulder side is loaded with a force in the direction opposite to the tire traveling direction due to the difference in tire diameter, deforms in the direction opposite to the block land portion on the equator plane side, and on the equatorial plane side. Similar to the block land portion 4, it wears unevenly. Therefore, the inventor has intensively studied, in the outer block land portion row 8 on the shoulder side, according to the principle shown in FIG. 3, the force that effectively shears and disperses the tire from the viewpoint of preventing sliding wear. It has been found that it is appropriate to set the length in the tire circumferential direction of the lateral groove 3A between the block land portions adjacent in the circumferential direction to 10% or less of the groove depth of the lateral groove 3.

Furthermore, the tire of the present invention is a lateral groove 3A of the outer side block land row 8, the depth from the tread surface 9 until the groove bottom 10, than the end of the tire equatorial plane CL side, the shoulder side end P is smaller and the groove bottom 10 on the shoulder side is shallower. Since the inventor applies a large lateral force to the edge portion 11A on the outer side in the tire width direction of the block land portion 4 of the outer block land portion row 8 during cornering traveling, the edge portion 11A on the outer side in the tire width direction It has been found that the block land portion 4 wears out earlier than the edge portion 11B on the inner side in the width direction, and the block land portion 4 wears unevenly. Therefore, by adopting the above configuration, the depth of the lateral groove 3A of the outer block land portion row 8 is made shallower on the shoulder side, and the rigidity at the edge portion 11A on the outer side in the tire width direction of the block land portion 4 is improved. Even when a large lateral force is sometimes applied to the edge portion 11A on the outer side in the tire width direction of the block land portion 4 of the outer block land portion row 8, it is possible to sufficiently resist the lateral force. As a result, sliding wear at the edge portion 11A on the outer side in the tire width direction is suppressed, the wear difference between the edge portion 11A on the outer side in the tire width direction and the central portion 12 of the block land portion 4 is reduced, and uneven wear is suppressed. As a result, uneven wear is effectively suppressed not only in the central block land portion row 6 but also in the outer block land portion 8, so that the period until the tire is rejected due to the progress of wear becomes longer and the tire life is extended. be able to.

The groove bottom shape of the lateral groove 3A shown in FIG. 5 (b) is varied in depth by changing the groove depth stepwise so that the groove bottom 10 has a stepped shape, but FIG. ), It is possible to vary the depth of the lateral groove 3A by uniformly inclining the groove bottom 10 of the lateral groove 3A with respect to the tire width direction. Alternatively, as shown in FIG. 6B, the depth of the lateral groove 3A can be varied by inclining the groove bottom 10 of the lateral groove 3A at a plurality of different angles. The configuration of the central land row 6 of the tire of the present invention, between the block land portion arrays 5, 5 adjacent contact two rows, block land portions 4 constituting them are arranged mutually offset in the tire circumferential direction Further, the extending direction of the groove portion 7 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 further, the distance between the block land portions adjacent in the tire circumferential direction is d _1. , short distance d ₂ between the block land portions adjacent in the tire width direction, and as long as the ratio a / B is in the range of 1 / 3-1 / 1.5, also possible to other configurations It is. For example, as shown in FIG. 7, the length of the cross-section in the tire width direction of the block land portion 4 of the central block land portion row 6 is from the tire circumferential direction both ends 13 and 13 of the block land portion 4 to the center of the block land portion 4. The tire having the tread portion 1 having a shape that increases once toward the portion 12 and then becomes shorter is a reference tire that is not an invented tire.

Further, in the outer block land portion row, the minimum depth H ₁ of the transverse grooves between the block land portions adjacent in the tire circumferential direction is preferably in the range of 0.4 to 0.8 times the maximum depth H ₂ . Such minimum depth H ₁ is maximized when made depth 0.40 times less than H _2, the rigidity in the tire width direction outer edge portion 7 of the block land portion is sufficiently improved, uneven wear is effectively Although it is suppressed, there is a possibility that the groove volume is insufficient, the drainage performance is lowered, and the steering stability on the wet road surface is not sufficiently improved. On the other hand, such minimum depth H ₁ is, when more than 0.8 times the maximum depth H _2, since the rigidity in the tire width direction outer edge portion 7 of the block land portion is not sufficiently improved, uneven wear May not be effectively suppressed.

Furthermore, in the outer block land portion row 8, the tire width direction length W ₁ of the portion having the maximum depth H ₂ of the lateral groove 3 A between the block land portions adjacent in the tire circumferential direction is equal to the tire width direction of the block land portion 4. it is preferably in the range of 0.4 to 0.7 times the length _{W 2.} When the tire width direction length W _{1 of the} portion 14 having the maximum depth H ₂ exceeds 0.7 times the tire width direction length W ₂ of the block land portion, the tire width direction of the block land portion 4 Since the rigidity of the outer edge portion 11A is not sufficiently improved, there is a possibility that uneven wear cannot be effectively suppressed. On the other hand, when the tire width direction length W _{1 of the} portion 14 having the maximum depth H ₁ is less than 0.4 times the tire width direction length W ₂ of the block land portion 4, Although rigidity at the edge portion 11A on the outer side in the tire width direction is effectively secured and uneven wear is suppressed, drainage performance is reduced due to insufficient groove volume, and steering stability on wet road surfaces may not be sufficiently improved. is there.

  Further, from the viewpoint of the interaction between the block land portions as described above, and from the viewpoint of maintaining the action until the end of wear, it is adjacent in the tire width direction in both the central block land portion row 6 and the outer block land portion row 8. It is preferable that the groove depth of the groove portion between the block land portions (that is, the lateral groove 3) is in the range of 60 to 100% of the groove depth of the circumferential groove 2A.

Further, as shown in FIGS. 8 and 9, the length of the cross section in the tire width direction of the block land portion 4 increases from the tire circumferential direction both ends 13, 13 of the block land portion 4 to the central portion 12 of the block land portion 4. 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 4 from the both ends 13 and 13 in the tire circumferential direction of the block land portion 4 to the central portion 12 of the block land portion 4, When the land portion 4 is grounded obliquely with respect to the road surface, compressive stress is concentrated in the central region of the block land portion 4 as shown in FIG. As shown in FIG. 9, even if a force to deform from the kicking end 15 toward the stepping end 16 is generated, it is inclined with respect to the tire circumferential direction on the kicking end 15 side of the block land portion 4. A force Q that causes the wall portion of the block land portion 4 to bulge in the normal direction is generated. At this time, the component force R of the force Q to be expanded is generated in the opposite direction from the left and right wall portions of the block land portion 4 and is mutually offset in the block land portion 4, and the other component force P resists the force that the rubber in the central region of the block land portion 4 tries to deform from the kicking end 15 toward the stepping end 16. As a result, excessive deformation of the block land portion 4 is suppressed, and uneven wear and sliding wear of the block land portion 4 can be prevented. Moreover, as shown in FIG. 11, the deformation | transformation (solid line) at the time of applying driving force to the block land part 4 of the tire according to this invention which does not apply the above-mentioned block shape, and the shape according to this invention as mentioned above were employ | adopted. Comparing the deformation (dotted line) when the driving force is applied to the block land portion 4, the block land portion 4 in the latter tire is moved to the block kicking end side by the same mechanism as when kicking out when stepped on. Although the deformation of the rubber is suppressed, the suppressed deformation acts in the direction of increasing the lifting of the kicking end 15 of the block land portion 4 that has already been stepped on due to the incompressibility of the rubber. As a result, since the shear deformation of the block land portion 4 to be stepped on next increases, the shear force during stepping increases as shown in FIG. The effect of becoming smaller can be produced synergistically. At this time, when the tire width direction length of the end portion in the tire circumferential direction of the block land portion 4 is A and the tire width direction length of the central portion 12 of the block land portion 4 is B , the ratio A / B is , Preferably in the range of 1/3 to 1 / 1.5. This is because if the ratio of the lengths is out of the range, the deformation of the block land portion 4 cannot be effectively prevented when the block land portion 4 is grounded obliquely. This is because sliding wear may occur.

  At this time, the same block land portion 4 faces the same circumferential groove 2, and the groove portion 7 between the block land portions adjacent to each other in the tire width direction is seen from the tire equatorial plane when viewed in the tire circumferential direction. It is preferable that the opening angle is in the opposite direction. Because, when the extending direction of the groove portion 7 between the block land portions adjacent to each other in the tire width direction is the same, it is possible to effectively cope with an 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. Further, the inclination in the extending direction of the groove portion adjacent to the tire width direction and the inclination of the block land portion 4 generated by increasing the cross-sectional length in the tire width direction of the central portion of the block land portion 4 face each other. By making it an array, it is possible to form a block pattern without generating wasted space in the tire width direction, and to effectively demonstrate wear resistance performance without compromising both the configuration and operation of each other. Pattern design by combining with ribs, shoulder ribs, lugs and the like is also facilitated.

Further, in the central block land portion row 6, the ratio d ₁ / d ₂ of the block land portion distance d ₁ adjacent in the tire circumferential direction to the block land portion distance d ₂ adjacent in the tire width direction is 1/0. It is preferably within the range of 85 to 1 / 0.3 , more preferably within the range of 1 / 0.7 to 1 / 0.4 . When the ratio d ₁ / d _{2 of the} distance d ₁ between the block land portions adjacent in the tire circumferential direction to the distance d ₂ between the block land portions adjacent in the tire circumferential direction is larger than 1 / 0.3 , the tire circumference even enough is distance d ₁ between the block land portions adjacent in the direction, it becomes too short distance d ₂ between the block land portions adjacent in the tire width direction. Therefore, the block land portions 4 adjacent to each other in the tire width direction come into contact with each other during tire load rolling, and the deformation force that collapses and deforms is not effectively transmitted to the block land portions 4 adjacent to the tire width direction. There is a possibility that the shearing force in the land portion 4 is not effectively dispersed and sliding wear is caused. On the other hand, when the ratio d ₁ / d _{2 of the} distance d ₁ between the block land portions adjacent in the tire circumferential direction to the distance d ₂ between the block land portions adjacent in the tire width direction is smaller than 1 / 0.85 , even enough that distance d ₂ between the block land portions adjacent in the tire width direction, becomes too short distance d ₁ between the block land portions adjacent in the tire circumferential direction. Therefore, when the block land portion 4 comes in contact with the road surface, the block land portions 4 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, in the central block land portion row 6, the ratio d ₃ / d ₁ of the tire circumferential direction length d ₃ of the block land portion 4 to the block land portion distance d ₁ adjacent in the tire circumferential direction is 1/0 . It is preferably in the range of 25 to 1 / 0.05 , more preferably in the range of 1 / 0.17 to 1 / 0.07 . When the ratio d ₃ / d _{1 of the} distance d ₁ between the block land portions adjacent to each other in the tire circumferential direction of the tire circumferential direction length d ₃ of the block land portion 4 is larger than 1 / 0.05 , When the block land portion 4 falls and deforms during movement, the block land portion 4 adjacent in the tire circumferential direction approaches too much. Therefore, as shown in FIG. 4, when the block land portion 4 of the tread portion 1 that is in contact with the road surface is pressed and deformed, the block land portion 4 adjacent to the tire circumferential direction in the center of the tread portion 1. They come into contact with each other and the outer block land portion 4 is pushed outward in the tire circumferential direction, and the block land portion 4 falls excessively in both directions of the tire rotation direction 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 15 increases, there is a possibility of causing sliding wear due to the falling deformation. On the other hand, when the ratio d ₃ / d ₁ of the tire circumferential direction length d ₃ of the block land portion 4 to the block land portion distance d ₁ adjacent in the tire circumferential direction is smaller than 1 / 0.25 , the tire Since the block land portions 4 adjacent to each other in the circumferential direction are too far apart, the shear force of the block land portions 4 adjacent to the tire circumferential direction is distributed in a well-balanced manner using the shear force of the kicking end 15 of the block land portion 4. Can still cause sliding wear.

Furthermore, in the central block land portion row 6, distance _{d 2} between the block land portions adjacent in the tire width direction is preferably in the range of 1.0 to 5.0 mm, more preferably 1.5 to 3. It is in the range of 5 mm. When the distance d ₂ between the block land portions adjacent in the tire width direction exceeds 5.0mm, it distance d ₂ between the block land portions adjacent in the tire width direction too long. As a result, the deforming force that collapses and deforms cannot be transmitted to the block land portion 4 adjacent in the tire width direction, causing excessive tilt deformation in the tire circumferential direction, resulting in slippage of the block land portion 4. Wear may occur. On the other hand, if the distance d ₂ between the block land portions adjacent in the tire width direction 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 4 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 4 adjacent in the tire width direction. However, excessive collapse deformation may be caused, and there is a possibility that the wear due to the sliding of the block land portion 4 may also be caused.

In addition, in the central block land row 6, 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 4.0 to 8. It is in the range of 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 4 increases 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 4 comes into contact with the road surface, the block land portion 4 comes into contact with the tire in the circumferential direction, and deformation due to rubber bulging shown in FIG. 4 may occur, resulting in a decrease in wear resistance.

  In addition, as shown in FIGS. 12 to 13, the block land portion 4 is provided with a narrow groove 17 that communicates the two circumferential grooves 2 and 2 adjacent to the block land portion 4 in the tire width direction. It is preferable that Generally, in the block land portion where no narrow groove is provided, the grip force tends to be weakened as far as the kicking end, and the desired grip performance may not be obtained. However, as described above, by providing a narrow groove in the block land portion and providing the kicking end 15 again, the grip force of the block land portion 4 can be improved as a whole, so that the torque from the engine is more efficient. Therefore, it is possible to improve the grip performance by converting it into driving force. At this time, the narrow groove 17 may be bent or refracted in the block land portion 4.

  The narrow groove 17 is preferably open to the circumferential groove 2 at the central portion 12 of the block land portion 4. This is because when the narrow groove 17 is open in a region off the central portion 12 of the block land portion 4, the grip force as a driving force cannot be distributed in a balanced manner in the block land portion 4, and the engine This is because there is a possibility that the torque from the motor cannot be efficiently converted into driving force.

  Furthermore, the tire circumferential direction length of the narrow groove 17 is preferably in the range of 5 to 20%, more preferably in the range of 7 to 18% of the groove depth (diameter direction depth) of the lateral groove 3. is there. When the tire circumferential direction length of the narrow groove 17 is less than 5% of the groove depth of the lateral groove 3, the tire circumferential direction length of the narrow groove 17 becomes too short. As a result, as in the case where the narrow groove 17 is not provided in the block land portion 4, the grip force decreases from the stepping end 16 toward the kicking end 15, and the effect of arranging the fine groove 17 may be lost. There is sex. On the other hand, when the tire circumferential direction length of the narrow groove 17 exceeds 20% of the groove depth of the lateral groove 3, the tire circumferential direction length of the narrow groove 17 becomes too long. As a result, it becomes impossible to transmit the force due to the reaction between the block land portions 4 divided by the narrow grooves 17 in the block land portion 4, which may cause excessive falling deformation and sliding wear due to that. There is sex. In order to obtain a sufficient effect until the end of wear, the groove depth of the narrow groove 17 is preferably 60 to 100% of the groove depth of the lateral groove 3.

Furthermore, it is preferably in a range of tire circumferential direction length d ₃ of the block land portion 4 of 1.0 to 2.5% of the tire circumferential length. To effectively Kanade the blocking effect of the land portion 4 of the invention as described above, it is appropriate tire circumferential direction length d ₃ of the block land portion 4 is not more than 2.5% of the tire circumferential length. This is because if this value exceeds 2.5%, the block shear rigidity increases excessively, and there is a possibility that the block land portion 4 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 4 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 4 excessively decreases When the driving force is applied to the block land portion 4, the block land portion 4 is excessively sheared and the sliding wear cannot be sufficiently suppressed. Therefore, by setting the range of the tire circumferential length d ₃ of the block land portion 4 of 1.0 to 2.5% of the tire circumferential length, rigidity of the block land portion 4 is ensured, and, above the block land Since the effect of the portion 4 is effectively exhibited, the wear resistance may be improved.

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 structure shown in FIGS. 8 , 12, and 13 , uneven wear according to the present invention can be prevented by arranging two blocks on the tread surface as a single unit with the block land portion row 5 in one row. However, although three or more rows of block land portions 5 can be formed as one unit, illustration is omitted, five rows can be arranged as one unit. Further, as shown in FIG. 14, in the outer block land portion row 8, it is possible to further improve the drainage performance by using a shallow groove 18 in the vicinity of the block land portions 4 adjacent in the tire circumferential direction.

  Next, the pneumatic tires of the present invention (Example tires 1 to 7) and the configuration of the outer block land portion row are out of the scope of the present invention, but the other configurations are similar to the pneumatic tire of the present invention. An experimental tire (comparative example tires 1 and 2) and a pneumatic tire of a conventional example having a rectangular block land portion (conventional example tire) are prototyped as heavy duty pneumatic tires with a tire size of 11R / 22.5, respectively. Since the performance evaluation was performed, it will be described below.

  The comparative tires 1 and 2 each include a tread portion configured as shown in FIG. The tread portion has two rib-shaped land portions and a plurality of block land portion rows surrounded by the rib-like land portions, and is adjacent to the tire block direction in the central block land portion row among the block land portion rows. The extending direction of the groove between the block land portions 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 greater than the distance between the block land portions adjacent to each other in the tire circumferential direction. Is shorter. Further, in the outer block land portion row, the depth of the lateral groove is constant, and has the specifications shown in Table 1, respectively.

  In addition, all of Example tires 1 and 4 to 7 have a tread portion configured as shown in FIG. 15, and each of Example tires 2 and 3 has a tread portion configured as shown in FIGS. The tread portion has two rib-shaped land portions and a plurality of block land portion rows surrounded by the rib-like land portions, and is adjacent to the tire block direction in the central block land portion row among the block land portion rows. The extending direction of the groove between the block land portions 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 greater than the distance between the block land portions adjacent to each other in the tire circumferential direction. Is shorter. Moreover, in the outer block land portion row, the depth of the lateral groove is smaller on the shoulder side than on the tire equatorial plane side so that the groove bottom is uniformly inclined as shown in FIG. Further, in the outer block land portion row, the tire circumferential length of the lateral groove is 10% or less of the groove depth of the lateral groove. Example tires 1 to 7 have the specifications shown in Table 1, respectively.

  The conventional tire has the configuration of the tread portion shown in FIG. 16 and has a rectangular block land portion. Moreover, it has the item shown in Table 1.

  Each of these test tires is attached to a rim having a size of 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 750 kPa (relative pressure) and a tire load load of 25. 0 kN (per one) was applied and subjected to various evaluations.

  Wear resistance in the central block land row is measured by measuring the wear amount in the central portion of the block land portion after running 50000 km on the test road, and the wear amount in the central portion of the block land portion in the conventional tire is indexed to a maximum value of 100. The relative values of other tires were obtained and evaluated by comparing them. In addition, it represents that it is excellent in the abrasion resistance in a center block land part row | line | column, so that a numerical value is small, and the result is shown in Table 2. Further, the wear resistance in the outer block land portion row is determined by measuring the difference in wear between the center portion of the block land portion in the outer block land portion row and the edge portion on the outer side in the tire width direction after the above-mentioned traveling for 50000 km. The difference in wear of the block land portion was indexed with a maximum value of 100, and relative values were obtained for the other tires and evaluated by comparing them. In addition, it represents that it is excellent in the abrasion resistance in an outer block land part row | line | column, so that a numerical value is small, and the result is shown in Table 2.

  In addition, the driving stability on wet roads is evaluated by a professional driver with a feeling of driving stability when driving on wet road surface conditions with a water film of 2 mm on a test course with a steel plate. The relative value was obtained for the other tires, and the evaluation values were compared by using the evaluation value as a reference value (100). In addition, it shows that it is excellent in the steering stability in a wet road surface, so that a numerical value is large, and the result is shown in Table 2.

  As is apparent from the results in Table 2, the amount of wear at the central portion of the block land portion in the central block land portion row is reduced in Comparative Tires 1 and 2 and Example Tires 1 to 7 as compared with the conventional tires. doing. Moreover, although the wear difference of the block land part in an outer side block land part row | line | column is small in the comparative example tires 1-2 and the example tires 1-7 compared with the conventional example tire, especially the example tire 1 In FIG. 7, it is remarkably small. Furthermore, the handling stability on the wet road surface was maintained or improved in all tires compared to the conventional tires.

  As is apparent from the above, according to the present invention, by optimizing the shape of the lateral groove in the outer block land portion row, the wear resistance is improved on the premise of maintaining steering stability on the wet road surface. Tires can be provided.

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. (A) is a development view about a part of the tread portion of the tire , and (b) is a cross-sectional view taken along line II of the tread portion shown in (a). (A) And (b) is a tire width direction sectional view of a transverse groove in an outside block land part row of other tires according to this invention. FIG. 6 is a development view of a part of a tread portion of another tire. 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 outer side block land part row | line | column of the other tire according to this invention. FIG. 3 is a development view of a part of a tread portion of an example tire. FIG. 6 is a development view of a part of a tread portion of a conventional tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2, 2A Circumferential groove 3, 3A Transverse groove 4 Block land part 5 Block land part row | line | column 6 Central block land part row | line | column 7 Groove part 8 between the block land parts adjacent to a tire width direction Outer block land part row | line | column 9 Tread part tread 10 Cross groove bottom 11A, 11B Edge part 12 Block land part center part 13 Block land part tire circumferential direction both ends 14 Part having maximum depth 15 Extrusion end 16 Step end 17 Narrow groove 18 Shallow groove

Claims (13)

A plurality of blocks composed of a large number of block land portions are provided in the tread portion by arranging a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves communicating with two adjacent circumferential grooves. A tire in which a land line is partitioned,
In the central block land portion row which is at least two block land portion rows adjacent to each other with the circumferential groove interposed therebetween, the block land portions constituting them are arranged to be shifted from each other in the tire circumferential direction, and the tire width 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. The distance between the block land is short,
In the outer block land portion row on the outer side in the tire width direction of the central block land portion row, the lateral groove between the block land portions adjacent to each other in the tire circumferential direction has a depth at least at the end portion on the shoulder side. Smaller than the length, and the tire circumferential length of the transverse groove is 10% or less of the groove depth of the transverse groove,
In the outer block land portion row, the minimum depth of the lateral groove between the block land portions adjacent in the tire circumferential direction is in a range of 0.4 to 0.8 times the maximum depth,
For all block land portions in the central block land portion row, the tire width direction length of the tire circumferential direction end of the block land portion is A, and the length in the tire width direction of the central portion of the block land portion is When B, the ratio A / B is in the range of 1/3 to 1 / 1.5.   In the outer block land portion row, the tire width direction length of the portion having the maximum depth of the lateral groove between the block land portions adjacent in the tire circumferential direction is 0.4 to 0 of the tire width direction length of the block land portion. The tire according to claim 1, which is in a range of .7 times.   The tire according to claim 1 or 2, 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 central portion of the block land portion. In the central block land portion row, the ratio d ₁ / d ₂ of the block land portion distance d ₁ adjacent in the tire circumferential direction to the block land portion distance d ₂ adjacent in the tire width direction is 1/0. The tire according to any one of claims 1 to 3, which is in a range of 85 to 1 / 0.3. The tire according to claim 4, wherein the ratio d ₁ / d ₂ is in a range of 1 / 0.7 to 1 / 0.4. In the central block land portion row, the ratio d ₃ / d ₁ of the tire circumferential direction length d ₃ of the block land portion to the block land portion distance d ₁ adjacent to the tire circumferential direction is 1 / 0.25. The tire according to any one of claims 1 to 5, which is in a range of 1 / 0.05. The tire according to claim 6, wherein the ratio d ₃ / d ₁ is in a range of 1 / 0.17 to 1 / 0.07.   The tire according to any one of claims 1 to 7, wherein in the central block land portion row, a distance between block land portions adjacent in the tire width direction is 1.0 to 5.0 mm.   The tire according to any one of claims 1 to 8, wherein in the central block land portion row, a distance between block land portions adjacent to each other in the tire circumferential direction is 3.0 to 10.0 mm.   The tire according to any one of claims 1 to 9, wherein a narrow groove that connects two circumferential grooves adjacent to the block land portion in the tire width direction is disposed in the block land portion.   The tire according to claim 10, wherein the narrow groove is open to the circumferential groove at a central portion of the block land portion.   The tire according to claim 10 or 11, wherein a tire circumferential direction length of the narrow groove is within a range of 5 to 20% of a groove depth of the lateral groove.   The tire according to any one of claims 1 to 12, wherein the central block land portion row includes two block land portion rows.

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