JP2010030466A - Tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire preventing the degradation of the productivity and the draining performance of the tire by properly making a shape of a groove bottom, and improving wear resistance and stone biting preventive performance while ensuring flexibility in pattern designing. <P>SOLUTION: In the tire, a block land part line 5 composed of a large number of block land parts 4 is divided and formed on a tread portion 1. The groove depth H of a lateral groove 3 is at least partially increases gradually from a start point 6 on a tire equator surface CL side of the lateral groove 3 toward the outside in a tire width direction. On the groove bottom 8 of the lateral groove 3, a protrusion 9 projecting out to the outside in a tire diametrical direction is provided. <P>COPYRIGHT: (C)2010,JPO&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 load tire, in which a block land portion row made up of sections is formed, and improves the stone biting prevention performance of the tire.

  The heavy load tire has a relatively deep tread groove, so when driving on gravel roads or forest roads, road stones or gravel bite into the groove, and this stone bite was embedded in the tread part. It is easy to damage the belt layer. Therefore, in order to prevent the above-mentioned stone biting, the groove depth is made shallow so that stones or gravel is not bitten deeply, or as disclosed in Patent Document 1, the depth of the groove By providing a step or inclination on the side wall of the groove so that the directional groove width is reduced, a compressive stress is generated from the side wall, which acts to push out the bitten stone or gravel, or disclosed in Patent Document 2. As described above, tires having improved stone biting prevention performance have been proposed by providing protrusions on the side walls of the grooves so that stones or gravel is difficult to bite in the first place.

JP-A-60-236807 JP-A-6-115318

  However, in the tire with shallow grooves and the tire described in Patent Document 1, even if the stone biting prevention performance is sufficiently ensured, the groove volume cannot be sufficiently ensured and the drainage performance may be deteriorated. There is. Further, in the tire described in Patent Document 2, the protrusions are lifted, and the expected stone biting prevention performance is not exhibited, the productivity of the mold is hindered due to the complicated shape of the mold, or the structure Is complicated, it may be a factor limiting the degree of freedom in pattern design.

  Accordingly, the object of the present invention is to optimize the groove shape, thereby suppressing a decrease in drainage performance and tire productivity and ensuring freedom in pattern design, while preventing wear and preventing stone biting. The object is to provide a tire with improved performance.

  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. In a tire in which a block land portion row composed of a large number of block land portions is partitioned, the groove depth of the lateral groove is gradually increased at least partially from the starting point on the tire equatorial plane side to the outer side in the tire width direction. The tire is characterized in that it includes a protrusion protruding outward in the tire radial direction at the bottom of the lateral groove. Adopting the configuration as described above, and gradually increasing the groove depth of the lateral groove between the block land portions adjacent in the tire circumferential direction from the starting point of the lateral groove on the tire equatorial plane side toward the outer side in the tire width direction. Thus, even if stones or gravel is bitten in the lateral groove, the stone or gravel is pushed from the groove bottom and the tire width direction outer side and pushed out in the tire width direction, so that the stone biting prevention performance can be effectively improved. It becomes possible. In addition, since the groove bottom of the lateral groove has a protrusion protruding outward in the tire radial direction, even if stones or gravel is likely to be caught in the horizontal groove, the protrusion causes the stone or gravel to move outward in the tire radial direction. Since it is pressed and pushed out, it is possible to further improve the stone biting prevention performance. Furthermore, since it is not necessary to significantly reduce the groove volume, it is possible to suppress a decrease in drainage performance as compared with a case where the groove depth is reduced (shallow) as a whole. Furthermore, since the configuration described above is simple in shape, the productivity of the tire and the degree of freedom in pattern design are not impaired.

  Further, it is preferable that at least a part of the groove bottom of the lateral groove is inclined at 65 ° or less with respect to the tire width direction.

  Furthermore, it is preferable that the minimum value of the groove depth of the lateral groove is in the range of 6 to 50% of the maximum value of the groove depth of the horizontal groove.

  Furthermore, it is preferable that the block land portions constituting them are arranged so as to be shifted from each other in the tire circumferential direction between adjacent block land portion rows. Here, “displaced” means a block in which the circumferential end of the block land portion is adjacent to the tire width direction by changing the start point of the arrangement pitch in the tire circumferential direction of the block land portion adjacent to the tire width direction. Arrangement that does not match between land parts shall be said.

  In addition, the extending direction of the groove between the block land portions adjacent in the tire width direction is inclined with respect to the tire width direction and the tire circumferential direction, and more than the distance between the block land portions adjacent in the tire circumferential direction, It is preferable that the distance between the block land portions adjacent to each other in the tire width direction is short. Here, the “groove portion” is a part of the circumferential groove and refers to a groove extending between the block land portions adjacent in the tire width direction.

  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 in the tire circumferential direction of the block land portion 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.

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

  Furthermore, the ratio of the distance between the block land portions adjacent in the tire circumferential direction to the length of the block land portion in the tire circumferential direction is preferably in the range of 1: 0.25 to 1: 0.05.

  According to the present invention, by optimizing the shape of the groove bottom, the deterioration of drainage performance and tire productivity is suppressed, and the degree of freedom in pattern design is ensured. It is possible to provide a tire with improved biting prevention performance.

  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 the line I-I in FIG. The block land portion 4 indicated by a dotted line is a block land portion 4 adjacent in the circumferential direction). 2 (a) and 2 (b) are cross-sectional views of lateral grooves in another tire 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 to 9 are development views of a part of a 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.

  In the tire of the present invention, as shown in FIGS. 1A and 1B, a plurality of circumferential grooves 2 extending in the tire circumferential direction and two adjacent circumferential grooves 2 are communicated with the tread portion 1. By arranging a plurality of transverse grooves 3, block land portion rows 5 composed of a large number of block land portions 4 are partitioned. The groove depth H of the lateral groove 3 gradually increases from the starting point 6 on the tire equatorial plane CL side of the lateral groove 3 toward the outer side in the tire width direction. Adopting such a configuration, the groove depth of the lateral groove 3 is gradually increased at least partially from the starting point 6 on the tire equatorial plane side of the lateral groove toward the outer side in the tire width direction, thereby ensuring sufficient groove volume and drainage performance. , And even if stones or gravel 7 is caught in the lateral grooves 3, the stones or gravel 7 is pressed from the groove bottom 8 of the lateral grooves 3 to the outside in the tire radial direction and pushed out of the lateral grooves 3. It is possible to effectively improve the stone biting prevention performance. Further, the groove bottom 8 of the lateral groove 3 is provided with a protruding portion 9 protruding outward in the tire radial direction. Since the groove bottom 8 of the horizontal groove 3 has a protruding portion 9 protruding outward in the tire radial direction, even if stone or gravel 7 is likely to be caught in the horizontal groove 3, the protruding portion 9 causes the stone or gravel 7 to move. Since it is pushed out in the tire radial direction and pushed out, it is possible to further improve the stone biting prevention performance. In addition, since the above-described configuration is not complicated in shape, it is not necessary to prepare a mold having a complicated shape, and an advantageous effect is obtained that does not impair the productivity and pattern design freedom of the tire. Although the groove bottom 8 of the lateral groove 3 shown in FIG. 1 is uniformly inclined with respect to the tire width direction, only a part of the groove bottom 8 of the horizontal groove 3 is inclined as shown in FIG. It is also possible to have a shape. Alternatively, as shown in FIG. 2B, the groove bottom 8 of the lateral groove 3 can be inclined at a plurality of different angles. Moreover, the arrangement | positioning position of the projection part 9 is not limited to the position of the example of illustration, If it is the groove bottom 8 of the horizontal groove 3, it can provide in arbitrary positions. Furthermore, in the illustrated example, one protrusion 9 is provided on the groove bottom 8 of the lateral groove 3, but a plurality of protrusions 9 are provided on the groove bottom 8 of the lateral groove 3 according to the desired stone-curling prevention performance. Is also possible.

  The inventor, in the block land portion 4 which is adjacent to the tire width direction and is arranged so as to be shifted from each other in the tire circumferential direction, the stone or gravel 7 bites into the lateral groove 3 between the block land portions adjacent in the tire circumferential direction. I found it easy to get involved. This is because the lateral groove 3 between the block land portions adjacent to each other in the tire circumferential direction is surrounded by the wall of the land portion from three directions, and when turning and exhibiting grip force, Or gravel is easy to enter. Therefore, with respect to a tire having block land portions that are arranged so as to be shifted from each other in the tire circumferential direction, the above-described stone biting prevention performance is improved in the lateral groove 3 between the block land portions adjacent in the tire circumferential direction. It is preferable to dispose the lateral groove 3 having the configuration.

  Further, at least a part of the groove bottom 8 of the lateral groove 3 is inclined at 65 ° or less with respect to the tire width direction, that is, the line segment 10 along the groove bottom 8 of the lateral groove 3 in the tire width direction cross section, and the tire The angle X formed with the line segment 11 along the width direction (tire central axis) is preferably 65 ° or less. As shown in FIG. 1B, when the groove bottom 8 of the lateral groove 3 is uniformly inclined with respect to the tire width direction and the angle X is more than 65 °, the lateral groove Since the tire radial direction length of 3 is too short, not only the groove volume is insufficient and drainage performance is lowered, but also stones or gravel 7 is likely to be bitten, and stone biting prevention performance may be lowered. is there. Further, when only a part of the groove bottom 8 of the lateral groove 3 is inclined as shown in FIG. 2A and the angle X exceeds 65 °, the inclination of the groove bottom 3 is increased. The stone or gravel 7 is likely to be bitten between the portion 12 that is formed and the side wall portion 13 that faces the inclined portion 12, and the stone biting prevention performance may be reduced.

  Furthermore, it is preferable that the minimum value of the groove depth H of the lateral groove 3 is in the range of 50 to 94% of the maximum value of the groove depth H of the lateral groove 3. If the minimum value of the groove depth H of the horizontal groove 3 is less than 50% of the maximum value of the groove depth H of the horizontal groove 3, the groove volume may be insufficient and the drainage performance may not be sufficiently ensured. On the other hand, when the minimum value of the groove depth H of the horizontal groove 3 exceeds 94% of the maximum value of the groove depth H of the horizontal groove 3, the groove bottom 8 hardly tilts. Since the compressive stress that presses the stone or gravel 7 from the inside in the radial direction and the tire width direction to the outside becomes small and the stone or gravel 7 becomes difficult to be discharged, there is a possibility that the stone biting prevention performance is lowered. is there.

In general, heavy load tires have a large flatness and high belt rigidity, so that when the tire is rolling, the belt portion rotates due to the driving force being applied, 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 demonstrated by reducing the tire circumferential distance between the block land parts, but when the tire circumferential distance between the block land parts is made closer, as shown in FIG. Because 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, 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 use the action between the block land portions, the following configurations were found.

In the tire having the configuration found by the inventor, the extending direction of the groove portion 14 between the block land portions adjacent 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. than between block land portion a distance d _1, distance d ₂ between the block land portions adjacent in the tire width direction is shorter. Between the block land portions 4 and 4 adjacent to each other in the tire width direction, the block land portions 4 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 4 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. Can do. 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.
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 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 suppressing sliding wear more effectively, the inclination angle of the extending direction of the groove portion 14 between the block land portions adjacent 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. In addition, 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, the groove depth of the groove portion 14 between the block land portions adjacent in the tire width direction is the circumferential groove. It is preferably in the range of 60 to 100% of the groove depth of 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 of the block land portion 4 in the tire width direction is temporarily increased from the tire circumferential direction end portions 15 and 15 to the center portion 16 and then shortened. Is also possible.

  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 15, 15 of the block land portion 4 to the central portion 16 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 tire circumferential direction both ends 15 and 15 of the block land portion 4 to the center portion 16 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, the block that is inclined with respect to the tire circumferential direction on the side of the kicking end of the block land portion 4 even if a force that tries to deform from the kicking end 17 toward the stepping end 18 occurs. A force Q that causes the wall portion of the 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 17 toward the stepping end 18. 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) of the block land part at the time of applying a driving force to the block land part which does not apply the above-mentioned block shape, and the shape and arrangement | positioning according to this invention as mentioned above were applied. Comparing with the deformation (dotted line) when the driving force is applied to the block land portion 4, the block land portion 4 according to the present invention has a rubber toward the block kicking end side by the same mechanism as when kicking out when stepped on. However, due to the incompressibility of the rubber, the suppressed deformation acts in a direction to increase the lifting of the kicking end 17 of the block land portion 4 that has already been stepped on. As a result, since the shear deformation of the block land portion 4 to be stepped on next increases, the shearing force during stepping increases as shown in FIG. The effect of becoming smaller can be obtained synergistically. At this time, the ratio of the tire width direction length B of the central portion 16 of the block land portion 4 to the tire width direction length A of the tire circumferential direction end portion 15 of the block land portion 4 is 1: 3 to 1: It is preferable to be in the range of 1.5. This is because if the length ratio is out of the range, deformation of the block land portion 4 cannot be effectively prevented, for example, when the block land portion 4 is grounded obliquely, and uneven wear and slippage of the block land portion occur. This is because wear may occur.

  Furthermore, in the same block land portion 4, facing the same circumferential groove 2, 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. Further, the inclination of the extending direction of the groove part adjacent to the tire width direction and the inclination of the block land part 4 caused by increasing the cross-sectional length of the central part 16 of the block land part 4 in the tire width direction are faced to 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 range of the tire circumferential direction length d ₃ of the block land portion 4 of 1.0 to 2.5% of the tire circumferential length. If the tire circumferential direction length d ₃ of the block land portion 4 exceeds 2.5% of the circumferential length of the tire, increase the block shear rigidity excessively, as described above, lifting of the block land portion 4 was finished already depression is It may not be obtained sufficiently. 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 undergoes excessive shear deformation, 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, 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 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, 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 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 the swelling of the rubber 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 4 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 4, the tire circumferential ratio of 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 4 falls and deforms, the block land portion 4 adjacent in the tire circumferential direction gets too close. Therefore, as shown in FIG. 6, 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 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 4, 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 4 is too far away, the shear force of the block land portion 4 adjacent to the tire circumferential direction cannot be distributed in a balanced manner using the shear force of the kicking end 17 of the block land portion 4. 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 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 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 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, 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 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. 6 may occur, resulting in a decrease in wear resistance.

  In addition, as shown in FIGS. 12 and 13, the block land portion 4 is provided with a narrow groove 19 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 Thus, by providing the kicking end 17 again, the grip force of the block land portion 4 can be improved as a whole, and the torque from the engine can be efficiently converted into driving force. . At this time, the narrow groove 19 may be bent or refracted in the block land portion 4.

  The narrow groove 19 is preferably open to the circumferential groove 2 at the central portion 16 of the block land portion 4. This is because when the narrow groove 19 is opened in a region off the central portion 16 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 19 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. When the tire circumferential direction length of the narrow groove 19 is less than 5% of the groove depth of the lateral groove 3, the tire circumferential direction length of the narrow groove 19 becomes too short. As a result, as in the case where the narrow groove 19 is not disposed in the block land portion 4, the grip force decreases from the stepping end 18 toward the kicking end 17, and the effect of disposing the narrow groove 19 may be lost. There is sex. On the other hand, when the tire circumferential direction length of the narrow groove 19 exceeds 20% of the groove depth of the lateral groove 3, the tire circumferential direction length of the narrow groove 19 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 19 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 19 is preferably 60 to 100% of the groove depth of the lateral groove 3.

  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 the land block 5 are arranged as one unit, and at least one block of the land block 5 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 5.

  Next, although the shape of the groove bottom of the lateral groove is out of the scope of the present invention, the pneumatic tires (comparative tires 1 to 3) having other configurations similar to the pneumatic tire of the present invention and the present invention. Each of the pneumatic tires (Example tires) was manufactured as a heavy-duty pneumatic tire having a tire size of 11R22.5 and performance evaluation was performed.

The comparative tires 1 to 3 and the example tires all have a tread portion configured as shown in FIG. 14, but the shape of the lateral groove is as shown in FIGS. 15 (a), 15 (b), 15 (c), and FIG. 15 (d). As shown in FIG. 15A, the lateral groove of the comparative example tire 1 has a tire width direction length of 30.0 mm and a groove depth of 16.5 mm uniformly. As shown in FIG. 15B, the lateral groove of the comparative tire 2 has a groove depth of 16.5 mm, a deep groove portion having a tire width direction length of 18.0 mm, and a groove depth of 11.5 mm. It consists of the shallow groove part whose tire width direction length is 12.0 mm, and the part which connects both parts is orthogonal to the tire width direction. As shown in FIG. 15C, the comparative example tire 3 has a groove bottom that is uniformly inclined so that the angle X is 13 °, and its length in the tire width direction is 30.0 mm. As shown in FIG. 15 (d), the tire of the example tire has a groove bottom inclined so that the angle X is 13 °, the tire width direction length is 30.0 mm, and the tire is placed on the groove bottom of the lateral groove. Protrusions projecting radially outward and having a height of 3.5 mm and a tire width direction length of 4.0 mm are provided.

  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 the front wheel and rear wheel (drive wheel) of the tractor vehicle used for the test. Air pressure: 900 kPa (relative pressure) Applying the tire load equivalent to the maximum load capacity specified in JATMA, running about 80000 km on the test road, counting the stones and gravel caught, and the number of stones and gravel in the lateral groove of the comparative tire 1 as a standard The values were indexed, and relative values were obtained for the other tires and evaluated by comparing them. In addition, it shows that it is excellent in the stone biting prevention performance, so that a numerical value is large, and the result is shown in Table 1.

  The drainage performance was measured by measuring the acceleration when the vehicle was started on a test course laid with a wet steel plate so that the water film was 2 mm from the running time of a predetermined distance. Was used as a reference value and indexed, and relative values were obtained for other tires and evaluated by comparing them. In addition, it represents that it is excellent in drainage performance, so that a numerical value is large, and the result is shown in Table 1.

  As is clear from the results in Table 1, the example tires have significantly improved anti-stone-breaking performance compared to the comparative example tires 1 to 3. Moreover, the fall of drainage performance is also suppressed.

  As is clear from the above, by optimizing the shape of the groove bottom, while ensuring the productivity of the tire, drainage performance, and freedom in pattern design, wear resistance and stone biting prevention performance are achieved. It has become possible to provide improved tires.

(A) is a development view of a part of a tread portion of a typical tire according to the present invention, and (b) is a cross-sectional view taken along line II 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. FIG. 3 is a development view of a part of a tread portion of a tire used in an example. (A) is sectional drawing of the lateral groove of the comparative example tire 1, (b) is sectional drawing of the lateral groove of the comparative example tire 2, (c) is sectional drawing of the lateral groove of the comparative example tire 3. (D) is sectional drawing of the lateral groove of an Example tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2, 2A Circumferential groove | channel 3 Horizontal groove 4 Block land part 5 Block land part row | line | column 6 Starting point on the tire equatorial plane side of a horizontal groove 7 Stone or gravel 8 Horizontal groove bottom 9 Protrusion 10 Line along the horizontal groove bottom Minute 11 Line 12 along tire width direction Inclined portion 13 Side wall portion 14 Groove portion between block land portions adjacent to tire width direction 15 Tire circumferential direction end portion 16 of block land portion Central portion 17 of block land portion Kick Exit end 18 Depression end 19 Narrow groove

Claims (8)

A block land portion composed of a large number of block land portions by disposing a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves communicating with two adjacent circumferential grooves in the tread portion. In a tire with compartments formed,
The groove depth of the lateral groove is gradually increased at least partially from the starting point on the tire equatorial plane side of the lateral groove toward the outer side in the tire width direction,
A tire comprising a projecting portion protruding outward in a tire radial direction at a groove bottom of the lateral groove.   The tire according to claim 1, wherein at least a part of a groove bottom of the lateral groove is inclined at 65 ° or less with respect to the tire width direction.   The tire according to claim 1 or 2, wherein a minimum value of the groove depth of the lateral groove is in a range of 50 to 94% of a maximum value of the groove depth of the horizontal groove.   The tire according to any one of claims 1 to 3, wherein the block land portions constituting the block land portion rows adjacent to each other in the tire width direction are arranged to be shifted from each other in the tire circumferential direction.   The extending direction of the groove portion between the block land portions adjacent 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 width direction rather than the distance between the block land portions adjacent in the tire circumferential direction. The tire according to claim 4, wherein the distance between the block land portions is short.   6. The length of the cross-section in the tire width direction of the block land portion is increased from both ends in the tire circumferential direction of the block land portion to a central portion of the block land portion, according to claim 1. Tires.   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 within a range of 1: 0.85 to 1: 0.3. The tire according to any one of 6.   The ratio of the distance between block land parts adjacent to the tire circumferential direction to the tire circumferential direction length of the block land part is in a range of 1: 0.25 to 1: 0.05. The tire according to any one of the above.

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