JP6821995B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

For example, the pneumatic tire described in Patent Document 1 includes a low-angle belt having a cord inclined at an angle of 5 ° or more and 30 ° or less with respect to the tire circumferential direction in the belt layer, and 45 with respect to the tire circumferential direction. It has been shown to have a high angle belt with a cord tilted at an angle of ° or more and 90 ° or less.

Further, for example, in the pneumatic tire described in Patent Document 2, it is shown that a pair of intersecting belt layers and a circumferential belt are laminated as a belt layer.

Japanese Unexamined Patent Publication No. 2008-260343 JP 2015-174469

Pneumatic tires for heavy loads mounted on trucks, buses, etc., and in particular, pneumatic tires having a low flatness, have the low angle belt of Patent Document 1 and Patent Document 2 for the purpose of maintaining the shape of the tread portion. A circumferential belt (hereinafter collectively referred to as a circumferential belt) is applied.

In the vicinity of the equatorial surface of the tire in the region where the circumferential belt is located, the circumferential rigidity is large due to the circumferential belt, so that it is possible to suppress the diameter growth when new and over time. On the other hand, on the outer side of the circumferential belt in the tire width direction, the circumferential rigidity is relatively small and the diameter growth is large as compared with the vicinity of the tire equatorial plane, and there is a problem that uneven wear occurs due to this.

The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of improving uneven wear resistance even in a configuration having a circumferential belt.

In order to solve the above-mentioned problems and achieve the object, the pneumatic tire according to one aspect of the present invention is a tire in which cords extending along the tire circumferential direction are arranged side by side in the tire width direction at the tread portion. A circumferential belt arranged in the tire width direction including the position of the equatorial plane and a tread surface of the tread portion extending along the tire circumferential direction and provided side by side in the tire width direction and arranged on the tire equatorial plane. A circumferential groove including a central circumferential groove, an outer circumferential groove arranged on the outermost side in the tire width direction, an intermediate circumferential groove arranged between the central circumferential groove and the outer circumferential groove, and the above. At least three land portions divided in the tire width direction by the intermediate circumferential groove between the central circumferential groove and the outer circumferential groove, and the circumferential groove adjacent to the tire width direction in each of the land portions. The land is provided with lateral grooves that are open at both ends and inclined with respect to the tire circumferential direction and are provided side by side in the tire width direction, and the inclination angle of the lateral grooves with respect to the tire circumferential direction is close to the tire equatorial plane. It is the smallest in the part, and the land part closer to the outside in the tire width direction is larger.

According to this pneumatic tire, the rigidity of the land portion closest to the equatorial plane of the tire is reduced by the acute angle of inclination of the lateral groove with respect to the tire circumferential direction, and the rigidity of the land portion is gradually increased toward the outside in the tire width direction. Therefore, the circumferential rigidity is increased by the circumferential belt to suppress the diameter growth at the time of new product and with time, and the rigidity difference between the vicinity of the tire equatorial plane and the outer side in the tire width direction caused by the circumferential belt is suppressed. As a result, it is possible to equalize the circumferential rigidity of the tread portion in the tire width direction and suppress the occurrence of uneven wear, and it is possible to improve the uneven wear resistance performance even in a configuration having a circumferential belt. ..

Further, in the pneumatic tire according to one aspect of the present invention, the lateral groove has a larger difference in inclination angle between the two adjacent land portions in the tire width direction as it is closer to the tire equatorial plane, and is outward in the tire width direction. The closer it is, the smaller it is preferable.

According to this pneumatic tire, the difference in the acute angle of inclination of the lateral groove with respect to the tire circumferential direction in the two adjacent land portions in the tire width direction is the difference in the rigidity of the two adjacent land portions. Therefore, the difference in the angle of inclination of the lateral groove with respect to the tire circumferential direction is larger as it is closer to the tire equatorial plane and smaller as it is closer to the outside in the tire width direction, so that the closer to the tire equatorial plane is the adjacent land portion in the tire width direction. Since the difference in rigidity becomes large, it is possible to suppress excessive peripheral rigidity near the tire equatorial plane due to the circumferential belt. As a result, it is possible to further equalize the circumferential rigidity of the tread portion in the tire width direction and suppress the occurrence of uneven wear, and even in a configuration having a circumferential belt, the effect of improving the uneven wear resistance performance can be achieved. It can be obtained remarkably.

Further, in the pneumatic tire according to one aspect of the present invention, the region partitioned between the outer circumferential grooves is set as the center region, and the tire width direction dimension Wf of the center region and the tire width direction of the circumferential belt The relationship with the dimension Wg is preferably Wg / Wf ≧ 1.03.

Since the circumferential rigidity does not increase in the region outside the tire width direction of the circumferential belt, it is not necessary to equalize the rigidity by the acute angle of inclination of the lateral groove with respect to the tire circumferential direction in this region. Therefore, it is preferable to arrange the entire center region within the range of the circumferential belt.

Further, in the pneumatic tire according to one aspect of the present invention, the closer the tire radial dimensional difference at both ends in the tire width direction of the land portion is to the tire equatorial plane, the closer to the tire equatorial plane, the closer to the tire equatorial plane, the closer the tire radial dimension difference at both ends in the tire width direction of the land portion is to the normal rim and the normal internal pressure. Smaller, larger as it is closer to the outside in the tire width direction, and the tire radial dimension difference Do of the land portion on the outermost side in the tire width direction and the tire radial dimension difference Dm of the land portion adjacent to the inner side in the tire width direction. The relationship is preferably Do / Dm ≧ 1.5.

According to this pneumatic tire, the smaller the tire radial dimensional difference at both ends in the tire width direction in the land area, the smaller the peripheral rigidity, and conversely, the larger the tire width direction, the larger the peripheral rigidity, and the outermost tire in the tire width direction. The larger the radial dimensional difference Do and the tire radial dimensional difference Dm of the land portion adjacent to the inner side of the tire width direction are, the larger the rigidity difference becomes. Therefore, the circumferential rigidity is reduced in the land portion while the circumferential rigidity near the tire equatorial plane is increased by the circumferential belt, and the circumferential rigidity is reduced in the land portion in the outer side in the tire width direction by the circumferential belt. By increasing the circumferential rigidity and defining the difference in rigidity of the land portion near the outside in the tire width direction by the relationship of Do / Dm, the difference in circumferential rigidity in the tire width direction due to the circumferential belt is suppressed in the land portion. be able to. As a result, it is possible to further equalize the circumferential rigidity of the tread portion in the tire width direction and suppress the occurrence of uneven wear, and even in a configuration having a circumferential belt, the effect of improving the uneven wear resistance performance can be achieved. It can be obtained remarkably.

Further, in the pneumatic tire according to one aspect of the present invention, the land portion is partitioned by two adjacent circumferential grooves in the tire width direction and two adjacent lateral grooves in the tire circumferential direction. A block is formed, and a small block is formed in which the block is divided in the tire width direction by a narrow groove whose both ends are opened in two adjacent lateral grooves in the tire circumferential direction. and the surface area S _I close the small blocks to the equatorial plane, the relationship between the surface area S _O of the small blocks closest to the tire width direction outside, it is preferable that S O _/ S _I ≧ 1.01.

According to this pneumatic tire, at block, most small block area S _O near the tire width direction outside, which is larger than the most surface area of the small block near the tire equatorial plane S _I, more tire width in the block The rigidity on the side closer to the outer side in the direction can be increased. As a result, it is possible to further equalize the circumferential rigidity of the tread portion in the tire width direction and suppress the occurrence of uneven wear, and even in a configuration having a circumferential belt, the effect of improving the uneven wear resistance performance can be achieved. It can be obtained remarkably.

Further, in the pneumatic tire according to one aspect of the present invention, the land portion is partitioned by two adjacent circumferential grooves in the tire width direction and two adjacent lateral grooves in the tire circumferential direction. The blocks are formed, and it is preferable that the aspect ratio of the tire circumferential dimension L of each block and the tire width direction dimension We is 1.2 ≦ L / We ≦ 2.0.

According to this pneumatic tire, the rigidity difference due to the block can be easily generated by setting the aspect ratio between the tire circumferential dimension L of the block and the tire width direction dimension We in the above range.

According to the present invention, uneven wear resistance can be improved even in a configuration having a circumferential belt.

FIG. 1 is a cross-sectional view of a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 3 is an enlarged plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view of the tread portion of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is an enlarged cross-sectional view of the tread portion of the pneumatic tire according to the embodiment of the present invention. FIG. 6 is an enlarged plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 7 is an enlarged view of the meridional cross section of the pneumatic tire according to the embodiment of the present invention. FIG. 8 is an enlarged plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 9 is an enlarged plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 10 is an enlarged plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 11 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components of this embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within a range self-evident by those skilled in the art.

FIG. 1 is a cross-sectional view of a part of the pneumatic tire according to the present embodiment, and FIG. 2 is a plan view of a tread portion of the pneumatic tire according to the present embodiment. FIG. 3 is an enlarged plan view of the tread portion of the pneumatic tire according to the present embodiment. 4 and 5 are enlarged cross-sectional views of the tread portion of the pneumatic tire according to the present embodiment.

In the following description, the tire radial direction means a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial inside is the side toward the rotation axis in the tire radial direction and the tire radial outside. Refers to the side away from the rotation axis in the tire radial direction. The tire circumferential direction refers to a circumferential direction centered on the rotation axis. The tire width direction means a direction parallel to the rotation axis, the inside in the tire width direction is the side toward the tire equatorial plane (tire equatorial line) CL in the tire width direction, and the outside in the tire width direction is the tire width direction. Refers to the side away from the tire equatorial plane CL. The tire equatorial plane CL is a plane that is orthogonal to the rotation axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1. The tire equatorial line is a line on the tire equatorial plane CL along the tire circumferential direction of the pneumatic tire 1. In the present embodiment, the tire equatorial line is designated by the same code “CL” as the tire equatorial plane.

The pneumatic tire 1 according to the present embodiment is a heavy-duty pneumatic tire applied to a truck, a bus, or the like. As shown in FIG. 1, the pneumatic tire 1 has a tread portion 21, shoulder portions 22 on both outer sides in the tire width direction thereof, and sidewall portions and bead portions that are sequentially continuous from each shoulder portion 22. There is. In FIG. 1, the sidewall portion and the bead portion are omitted. Further, the pneumatic tire 1 includes a carcass layer 24 and a belt layer 25.

The tread portion 21 is made of a rubber material (tread rubber) and is exposed on the outermost side of the pneumatic tire 1 in the tire radial direction, and the surface thereof serves as the contour of the pneumatic tire 1. A tread surface 21A is formed on the outer peripheral surface of the tread portion 21, that is, on the tread surface that comes into contact with the road surface during traveling.

The shoulder portion 22 is a portion on both outer sides of the tread portion 21 in the tire width direction. Further, although not clearly shown in the drawing, the sidewall portion is exposed to the outermost side in the tire width direction of the pneumatic tire 1. The bead portion has a bead core and a bead filler, although not explicitly shown in the drawing. The bead core is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler is a rubber material arranged in a space formed by folding the end portion of the carcass layer 24 in the tire width direction outward at the position of the bead core in the tire width direction.

In the carcass layer 24, each end in the tire width direction is folded back from the inside in the tire width direction to the outside in the tire width direction by a pair of bead cores, and is hung in a toroid shape in the tire circumferential direction to form a tire frame. is there. The carcass layer 24 is formed by coating a plurality of carcass cords (not shown) arranged side by side with an angle in the tire circumferential direction while having an angle with respect to the tire circumferential direction along the tire meridian direction with a coated rubber. The carcass cord is made of steel or organic fiber (such as polyester, rayon or nylon).

In the present embodiment, the belt layer 25 has a multi-layer structure in which four belts 25A, 25B, 25C, and 25D are laminated in the tire radial direction, and is arranged outside the tire radial direction on the outer periphery of the carcass layer 24 in the tread portion 21. , The carcass layer 24 is covered in the tire circumferential direction. The belts 25A, 25B, 25C, and 25D have a cord (not shown) at a predetermined angle with respect to the tire circumferential direction (for example, 45 ° or more and 90 ° or less with respect to the tire circumferential direction) coated with coated rubber. Is. The cord consists of steel or organic fibers (such as polyester, rayon or nylon). The belts 25A, 25B, 25C, and 25D are provided with the cords crossed in the stacking in the tire radial direction. The belt layer 25 may be provided with at least two belts laminated in the tire radial direction so as to intersect the cords.

Further, the belt layer 25 is provided with a circumferential belt 26. The circumferential belt 26 has a cord (not shown) having an angle of 0 ° (including ± 5 °) with respect to the tire circumferential direction arranged side by side in the tire width direction and coated with a coated rubber. The cord consists of steel or organic fibers (such as polyester, rayon or nylon). The circumferential belt 26 is arranged in the tire width direction including the position of the tire equatorial plane CL between the belts of the belt layer 25. In the present embodiment, the circumferential belt 26 is arranged between the belts 25B and 25C. That is, the circumferential belt 26 is arranged so as to be overlapped on the inner side or the outer side in the tire radial direction of the two belts provided so as to cross the cords in the belt layer 25.

Further, as shown in FIGS. 2 to 5, the tread portion 21 extends along the tire circumferential direction on the tread surface 21A, and has seven or more circumferential grooves 3 which are straight grooves parallel to the tire equatorial line CL. An odd number (7 in this embodiment) is provided. The circumferential groove 3 has a groove width of 8 mm or more and 15 mm or less (Wa in FIGS. 3 and 5) and a groove depth of 10 mm or more and 28 mm or less (dimensions from the opening position of the tread surface 21A to the groove bottom: FIGS. 4 and 5). It is a groove of Ha) of 5. The tread surface 21A extends along the tire circumferential direction by each circumferential groove 3, and the rib-shaped land portion 5 in which eight or more even numbers (eight in the present embodiment) are lined up in the tire width direction is formed. It is formed.

The circumferential groove 3 includes a central circumferential groove 3A whose center is arranged on the equatorial plane CL of the tire, an outer circumferential groove 3C arranged on the outermost side in the tire width direction, a central circumferential groove 3A, and an outer circumferential groove. Includes an intermediate circumferential groove 3B arranged between the 3Cs. Further, the land portion 5 includes an inner land portion 5A arranged inside the tire width direction of both outer circumferential grooves 3C and an outer land portion 5B arranged outside the tire width direction of both outer circumferential grooves 3C. Including. Further, the region inside the tire width direction of both outer circumferential grooves 3C in which the inner land portion 5A is arranged is referred to as a center region Ce. That is, the inner land portion 5A is arranged in the center region Ce.

Further, as shown in FIGS. 2 to 5, both ends of the tread portion 21 are opened in two circumferential grooves 3 adjacent to each other in the tire width direction in each inner land portion 5A of the center region Ce on the tread surface 21A. A lateral groove (also referred to as a groove in the width direction) 4 is provided. The lateral groove 4 refers to a groove having a groove width of 1 mm or more and 4 mm or less (Wb in FIG. 3) and a groove depth of 1 mm or more and 5 mm or less (dimensions from the opening position of the tread surface 21A to the groove bottom: Hb in FIG. 4). .. Then, in the inner land portion 5A, a block 51 is formed in which each land portion 5 partitioned by the adjacent circumferential grooves 3 is divided by the lateral groove 4. As shown in FIG. 2, the lateral grooves 4 are provided so that the openings to the circumferential grooves 3 face each other on both groove walls in the tire width direction of the circumferential grooves 3 so as to be continuous in the tire width direction. Although it is arranged, it is not limited to this, and it does not have to be continuous in the tire width direction.

Further, as shown in FIGS. 2 to 5, the tread portion 21 is a block 51 in which both ends are opened in two lateral grooves 4 adjacent to each other in the tire circumferential direction in the block 51 partitioned by the circumferential groove 3 and the lateral groove 4. A groove 6 is provided. The narrow groove 6 has a groove width of 1 mm or more and 4 mm or less (Wc in FIGS. 3 and 5) and a groove depth of 1 mm or more and 5 mm or less (dimensions from the opening position of the tread surface 21A to the groove bottom: Hc in FIG. 5). The groove of. Then, the block 51 is formed with a small block 51A divided in the tire width direction by the narrow groove 6. In FIGS. 2 to 5, two narrow grooves 6 are provided side by side in the tire width direction in one block 51, so that the small blocks 51A are the central small block 51Aa at the center in the tire width direction and the tire width direction thereof. Includes two outer small blocks 51Ab on each side. Further, in the fine groove 6 shown in FIG. 3, a bent portion 6A is formed in the middle, but the bent portion 6A may not be formed and the fine groove 6 may be formed so as to extend linearly (FIG. 9). reference). Further, at least one narrow groove 6 may be provided for the block 51 (see FIG. 10). In this case, the small block 51A does not have the central small block 51Aa and has two narrow grooves 6 on both sides in the tire width direction. Includes outer small block 51Ab.

Further, as shown in FIGS. 2 to 5, the tread portion 21 has one end communicating with the circumferential groove 3 on the tread surface 21A and the other end not intersecting the narrow groove 6 and the land portion 5 (small block 51A (outside)). It may have a sipe 7 formed terminally within the small block 51Ab)). The sipe 7 reduces the rigidity of the land portion 5 (small block 51A (outer small block 51Ab)) and relaxes the ground pressure, so that the uneven wear resistance performance can be improved. The same number of sipes 7 are provided in one block 51, and all sipes 7 have the same groove width Wd, groove depth Hd, and groove length Ld. Therefore, the sipe 7 is not caused by changing the rigidity in each land portion 5. The groove width Wd, groove depth Hd, and groove length Ld of the sipe 7 are 0.3 mm ≦ Wd ≦ 2.0 mm with respect to the tire width direction dimension We of the land portion 5 and the groove depth Ha of the circumferential groove 3. It is a groove that satisfies the relationship of 0.3 ≦ Hd / Ha ≦ 1.0 and 0.03 ≦ Ld / We ≦ 0.2.

Further, as shown in FIGS. 3 and 4, the tread portion 21 is chamfered 4A at the corner of the land portion 5 (block 51) on the acute-angled side where the lateral groove 4 is inclined and opened with respect to the circumferential groove 3. May be formed. By providing the chamfer 4A, the land portion 5 (block 51) is less likely to be peeled or chipped, and the durability can be maintained.

FIG. 6 is an enlarged plan view of the tread portion of the pneumatic tire according to the present embodiment. FIG. 7 is an enlarged view of the meridional cross section of the pneumatic tire according to the present embodiment. 8 to 10 are enlarged plan views of the tread portion of the pneumatic tire according to the present embodiment.

In the pneumatic tire 1 of the present embodiment, as shown in FIGS. 3 and 6, the inclination angle θ of the acute angle of the lateral groove 4 with respect to the tire circumferential direction is in the land portion 5 (inner land portion 5A) close to the tire equatorial plane CL. It is the smallest, and the land portion 5 (inner land portion 5A) closer to the outside in the tire width direction is larger. In the present embodiment, as shown in FIG. 6, three land portions 5 (inner land portions 5A) are provided on the outer side in the tire width direction with the tire equatorial plane CL (central circumferential groove 3A) as a boundary. .. In these three land portions 5 (inner land portion 5A), the inclination angle θ1 of the acute angle of the lateral groove 4 with respect to the tire circumferential direction in the land portion 5 (inner land portion 5A) closest to the tire equatorial plane CL and the tire width direction The acute angle θ2 of the lateral groove 4 with respect to the tire circumferential direction in the intermediate land portion 5 (inner land portion 5A) and the acute angle of the lateral groove 4 with respect to the tire circumferential direction in the outermost land portion 5 (inner land portion 5A) in the tire width direction. There is an acute angle θ3 of. Then, the relationship between these inclination angles θ1, θ2, and θ3 satisfies θ1 <θ2 <θ3.

According to the pneumatic tire 1, the rigidity of the land portion 5 (inner land portion 5A) closest to the tire equatorial plane CL is reduced by the acute-angled inclination angles θ1, θ2, and θ3 of the lateral groove 4 with respect to the tire circumferential direction. The rigidity of the land portion 5 (inner land portion 5A) is gradually increased toward the outside in the width direction. Therefore, the circumferential rigidity is increased by the circumferential belt 26 to suppress the diameter growth at the time of new product and over time, and the rigidity difference between the vicinity of the tire equatorial plane CL caused by the circumferential belt 26 and the outside in the tire width direction is suppressed. To do. As a result, it is possible to equalize the circumferential rigidity of the tread portion 21 in the tire width direction and suppress the occurrence of uneven wear, and improve the uneven wear resistance performance even in the configuration having the circumferential belt 26. Can be done.

The inclination angle θ of the acute angle of the lateral groove 4 with respect to the tire circumferential direction is preferably 50 ° or more and 80 ° or less. When the inclination angle θ of the acute angle of the lateral groove 4 with respect to the tire circumferential direction approaches 0 °, the rigidity of the acute angle portion weakens, which causes baldness or chipping. Further, when the inclination angle θ of the acute angle of the lateral groove 4 with respect to the tire circumferential direction approaches 90 °, the rigidity becomes too strong, and it becomes difficult to make a difference in rigidity between the block 51 on the CL side of the tire equatorial plane and the block 51 on the outer side in the width direction. Uneven wear resistance is reduced. From the above, it is preferable that the inclination angle θ of the acute angle of the lateral groove 4 with respect to the tire circumferential direction is 50 ° or more and 80 ° or less in order to maintain the rigidity of the block appropriately. Further, as shown in FIG. 2, the lateral groove 4 is provided so that the opening portion to the circumferential groove 3 faces each other on both groove walls in the tire width direction of the circumferential groove 3, and the tire equatorial plane CL is a boundary. Has a relationship of the inclination angles θ (θ1, θ2, θ3) on the outer side in the tire width direction. For this reason, the lateral grooves 4 are arranged in a substantially S shape in the entire center region Ce from the end to the end in the tire width direction. Further, the block 51 is also arranged in a substantially S shape in the entire center region Ce from the end in the tire width direction to the end like the lateral groove 4. By arranging the lateral grooves 4 and the block 51 continuously in the tire width direction in a substantially S shape in this way, it becomes easy to make the circumferential rigidity of the tread portion 21 described above uniform in the tire width direction. Even if the lateral grooves 4 and the block 51 are not continuous in the tire width direction, the circumferential rigidity in the tire width direction can be made uniform.

Further, in the pneumatic tire 1 of the present embodiment, the difference in the acute angle inclination angle θ of the lateral groove 4 with respect to the tire circumferential direction in the two adjacent land portions 5 (inner land portions 5A) in the tire width direction is the tire equatorial plane CL. It is preferable that the closer to the tire width, the larger the tire, and the closer to the outside in the tire width direction, the smaller the tire. In the present embodiment, as shown in FIG. 6, three land portions 5 (inner land portions 5A) are provided on the outer side in the tire width direction with the tire equatorial plane CL (central circumferential groove 3A) as a boundary. .. In these three land portions 5 (inner land portion 5A), the inclination angle θ1 of the acute angle of the lateral groove 4 with respect to the tire circumferential direction in the land portion 5 (inner land portion 5A) closest to the tire equatorial plane CL and the tire width direction The acute angle θ2 of the lateral groove 4 with respect to the tire circumferential direction in the intermediate land portion 5 (inner land portion 5A) and the acute angle of the lateral groove 4 with respect to the tire circumferential direction in the outermost land portion 5 (inner land portion 5A) in the tire width direction. There is an acute angle θ3 of. Then, there are θ2-θ1 and θ3-θ2 as differences in the inclination angle θ of the acute angle of the lateral groove 4 with respect to the tire circumferential direction in the two land portions 5 (inner land portions 5A) adjacent to each other in the tire width direction. Then, the relationship between θ2-θ1 and θ3-θ2 satisfies θ2-θ1> θ3-θ2.

According to the pneumatic tire 1, the difference in the inclination angle θ of the acute angle of the lateral groove 4 with respect to the tire circumferential direction in the two adjacent land portions 5 (inner land portion 5A) in the tire width direction is the difference between the two adjacent land portions 5. This is the difference in rigidity of (inner land portion 5A). Therefore, the difference in the inclination angle θ of the acute angle of the lateral groove 4 with respect to the tire circumferential direction is larger as it is closer to the tire equatorial plane CL and smaller as it is closer to the outside in the tire width direction, so that the closer to the tire equatorial plane CL is, the more adjacent it is in the tire width direction. Since the difference in rigidity of the land portion 5 (inner land portion 5A) is large, it is possible to suppress excessive peripheral rigidity in the vicinity of the tire equatorial plane CL due to the circumferential belt 26. As a result, it is possible to further equalize the circumferential rigidity of the tread portion 21 in the tire width direction and suppress the occurrence of uneven wear, and even in the configuration having the circumferential belt 26, the uneven wear resistance performance is improved. The effect can be remarkably obtained.

It should be noted that the relationship between θ2-θ1 and θ3-θ2 satisfies 1 ° ≦ (θ2-θ1) − (θ3-θ2) ≦ 5 °, that the lateral groove 4 causes the circumferential rigidity of the tread portion 21 in the tire width direction. This is preferable for further homogenization.

Further, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 1, the inner regions of the outer circumferential grooves 3C and 3C in which the inner land portion 5A is arranged are designated as the center region Ce in the tire width direction. It is preferable that the relationship between the tire width direction dimension Wf of the region Ce and the tire width direction dimension Wg of the circumferential belt 26 is Wg / Wf ≧ 1.03.

Since the circumferential rigidity does not increase in the region outside the tire width direction of the circumferential belt 26, it is not necessary to equalize the rigidity of the lateral groove 4 with respect to the tire circumferential direction by an acute angle θ. Therefore, it is preferable to arrange the entire center region Ce within the range of the circumferential belt 26.

It should be noted that the relationship between the tire width direction dimensions Wf and Wg satisfies Wg / Wf ≧ 1.05, and the circumferential belt covers the range of uniform rigidity due to the acute angle inclination angle θ of the lateral groove 4 with respect to the tire circumferential direction. It is preferable because it can be sufficiently arranged within the range of 26.

Further, in the pneumatic tire 1 of the present embodiment, in a no-load state assembled on a regular rim and filled with a regular internal pressure, the difference in tire radial dimension at both ends in the tire width direction of the land portion 5 (inner land portion 5A) is the tire equatorial line. The closer to the surface CL, the smaller, the closer to the outside in the tire width direction, the larger, and the tire radial dimensional difference Do of the land portion 5 (inner land portion 5A) on the outermost side in the tire width direction, and the land adjacent to the inner side in the tire width direction. It is preferable that the relationship between the tire radial dimensional difference Dm of the portion 5 (inner land portion 5A) is Do / Dm ≧ 1.5. In the present embodiment, as shown in FIG. 7, three land portions 5 (inner land portions 5A) are provided on the outer side in the tire width direction with the tire equatorial plane CL (central circumferential groove 3A) as a boundary. .. In these three land parts 5 (inner land part 5A), the tire radial dimensional difference D1 at both ends in the tire width direction in the land part 5 (inner land part 5A) closest to the tire equatorial plane CL and the middle in the tire width direction. Tire radial dimension difference D2 at both ends in the tire width direction in the land portion 5 (inner land portion 5A) and tire radial dimension difference at both ends in the tire width direction at the outermost land portion 5 (inner land portion 5A) in the tire width direction. There is D3 and. The relationship between these tire radial dimensional differences D1, D2, and D3 is D1 <D2 <D3, and the tire radial dimensional difference Do (D3) of the outermost land portion 5 (inner land portion 5A) in the tire width direction. ) And the tire radial dimensional difference Dm (D2) of the land portion 5 (inner land portion 5A) adjacent to the inside in the tire width direction satisfies D3 / D2 ≧ 1.5.

Here, the regular rim is a "standard rim" specified by JATTA, a "Design Rim" specified by TRA, or a "Measuring Rim" specified by ETRTO. The normal internal pressure is the "maximum air pressure" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO.

According to the pneumatic tire 1, the smaller the tire radial dimensional difference at both ends in the tire width direction in the land portion 5 (inner land portion 5A), the smaller the peripheral rigidity, and conversely, the larger the tire width direction, the larger the peripheral rigidity, and the most tire. The tire radial dimensional difference Do of the outer land portion 5 (inner land portion 5A) in the width direction and the tire radial dimensional difference Dm of the land portion 5 (inner land portion 5A) adjacent to the inner side of the tire width direction are tires. The larger the tire radial dimensional difference Do on the outer side in the width direction, the larger the difference in rigidity. Therefore, the circumferential rigidity near the tire equatorial plane CL is increased by the circumferential belt 26, whereas the circumferential rigidity is reduced in the land portion 5 (inner land portion 5A), and the circumferential rigidity is decreased by the circumferential belt 26 on the outer side in the tire width direction. The relationship between Do / Dm is the difference in rigidity of the land portion 5 (inner land portion 5A) near the outside in the tire width direction while increasing the circumferential rigidity in the land portion 5 (inner land portion 5A). By specifying the above, it is possible to suppress the difference in the circumferential rigidity in the tire width direction due to the circumferential belt 26 in the land portion 5 (inner land portion 5A). As a result, it is possible to further equalize the circumferential rigidity of the tread portion 21 in the tire width direction and suppress the occurrence of uneven wear, and even in the configuration having the circumferential belt 26, the uneven wear resistance performance is improved. The effect can be remarkably obtained.

Regarding the relationship between the tire radial dimensional differences Do and Dm, it is satisfied that Do / Dm ≧ 2.0, and the land on the outer side in the tire width direction near the outer end in the tire width direction of the circumferential belt 26 having a large difference in peripheral rigidity. It is preferable to increase the difference in rigidity of the portion 5 (inner land portion 5A) so that the circumferential rigidity of the tread portion 21 in the tire width direction can be further made uniform.

Further, in the pneumatic tire 1 of the present embodiment, the land portion 5 (inner land portion 5A) is adjacent to the two circumferential grooves 3 adjacent in the tire width direction and the tire circumferential direction as shown in FIG. A plurality of blocks 51 partitioned by two lateral grooves 4 are formed, and the blocks 51 are divided in the tire width direction by narrow grooves 6 having both ends open in two adjacent lateral grooves 4 in the tire circumferential direction. A small block 51A is formed. Then, as shown in FIGS. 8 to 10, at block 51, the most tire and the equatorial plane surface area of the outer small block 51Ab near CL _{S I,} and the surface area _{S O} of the outer small block 51Ab closest to the tire width direction outside _{relationship,} it is preferable that _S O / S _I ≧ 1.01.

According to this pneumatic tire 1, at block 51, the surface area S _O of closest to the tire width direction outside the outer small block 51Ab is from greater than the surface area S _I of the outer small block 51Ab closest to the tire equatorial plane CL , The rigidity of the side closer to the outside in the tire width direction in the block 51 can be increased. As a result, it is possible to further equalize the circumferential rigidity of the tread portion 21 in the tire width direction and suppress the occurrence of uneven wear, and even in the configuration having the circumferential belt 26, the uneven wear resistance performance is improved. The effect can be remarkably obtained.

Incidentally, the surface area _S I, the relationship of _{S O} may be satisfied _{1.03 ≦ S O / S I ≦} 1.10, in terms of the range that do not excessive rigidity difference in the tire width direction in the block 51 preferable. Further, the surface area _S I, _{S O,} it is assumed that free of sipes 7 described above. That is, the sipe 7 is not caused by changing the rigidity. Therefore, as described above, the same number of sipes 7 are provided in one block 51, and all sipes 7 have the same groove width Wd, groove depth Hd, and groove length Ld.

Further, in the pneumatic tire 1 of the present embodiment, the land portion 5 (inner land portion 5A) is adjacent to the two circumferential grooves 3 adjacent in the tire width direction and the tire circumferential direction as shown in FIG. A plurality of blocks 51 partitioned by two lateral grooves 4 are formed, and the aspect ratio between the tire circumferential dimension L of each block 51 and the tire width direction dimension We is 1.2 ≦ L / We ≦ 2. It is preferably 0.0.

According to the pneumatic tire 1, the rigidity difference due to the block 51 can be easily generated by setting the aspect ratio between the tire circumferential dimension L of the block 51 and the tire width direction dimension We in the above range.

The aspect ratio between the tire circumferential dimension L of the block 51 and the tire width direction dimension We satisfies the range of 1.4 ≦ L / We ≦ 1.8, but the difference in rigidity due to the block 51 is excessive. It is more preferable to make it within the range that does not become.

In this embodiment, performance tests related to uneven wear resistance were performed on a plurality of types of test tires under different conditions (see FIG. 11).

In this performance test, a pneumatic tire (heavy load pneumatic tire) with a tire size of 445 / 50R22.5 was assembled to a regular rim (22.5 "x 14.00") specified by TRA, and the regular internal pressure (830 kPa). Was filled and mounted on the trailer shaft of the test vehicle (6 x 4 tractor trailer).

In the performance test regarding the uneven wear resistance performance, after the test vehicle has traveled 10 km, the groove depths of the inner circumferential groove and the outer circumferential groove are measured, and the difference is measured as the uneven wear amount. Then, based on this measurement result, an index evaluation based on the conventional example (100) is performed. In this evaluation, the larger the value, the better the uneven wear resistance performance, which is preferable.

The pneumatic tires of the conventional example and Examples 1 to 18 shown in FIG. 11 are divided in the tire width direction by the circumferential belt and the intermediate circumferential groove between the central circumferential groove and the outer circumferential groove 3 Each land portion is provided with a lateral groove having both ends opened in a circumferential groove adjacent to the tire width direction and inclined with respect to the tire circumferential direction and provided in a plurality of lateral grooves in the tire width direction. In the pneumatic tire of the conventional example, the inclination angle θ1 of the lateral groove in the land portion closest to the tire equatorial plane CL with respect to the tire circumferential direction and the acute angle of the lateral groove in the land portion in the middle of the tire width direction with respect to the tire circumferential direction The relationship between the inclination angle θ2 and the acute angle inclination angle θ3 with respect to the tire circumferential direction of the lateral groove in the land portion on the outermost side in the tire width direction is θ1 = θ2 = θ3. On the other hand, the pneumatic tires of Examples 1 to 18 satisfy θ1 <θ2 <θ3. Further, prior art, pneumatic tires of Examples 1 to Example 10 has no narrow grooves, the surface area S _O of the pneumatic tire has a narrow grooves small blocks Examples 11 18 , the relationship of S _I are defined.

As shown in the test results of FIG. 11, it can be seen that the pneumatic tires of Examples 1 to 18 have improved uneven wear resistance.

1 Pneumatic tire 21 Tread part 21A Tread surface 22 Shoulder part 24 Carcass layer 25 Belt layer 25A, 25B, 25C, 25D Belt 26 Circumferential belt 3 Circumferential groove 3A Central circumferential groove 3B Intermediate circumferential groove 3C Outer circumferential groove 4 Lateral groove 4A chamfer 5 Land part 5A Inner land part 5B Outer land part 51 block 51A Small block 51Aa Central small block 51Ab Outer small block 6 Fine groove 6A Bending part 7 Sipe Ce center area CL Tire equatorial plane
D1, D2, D3 tire radial dimensional difference Do, Dm tire radial dimension difference L tire circumferential dimension S _I, the tire width direction dimension Wg circumferential direction of the tire width direction dimension Wf center region of the surface area We block _{S O} small block Dimension of the belt in the tire width direction θ (θ1, θ2, θ3) The angle of inclination of the lateral groove with respect to the tire circumferential direction.

Claims (5)

In the tread portion, cords extending along the tire circumferential direction are arranged side by side in the tire width direction, and the circumferential belt is arranged in the tire width direction including the position of the tire equatorial plane.
The tread surface of the tread portion extends along the tire circumferential direction and is provided side by side in the tire width direction. The central circumferential groove arranged on the tire equatorial plane and the outermost circumference arranged on the outermost side in the tire width direction. A circumferential groove including a directional groove, an intermediate circumferential groove arranged between the central circumferential groove and the outer circumferential groove, and
At least three land portions divided in the tire width direction by the intermediate circumferential groove between the central circumferential groove and the outer circumferential groove.
In each of the land portions, both ends are opened in the circumferential groove adjacent to the tire width direction, and the lateral grooves are provided so as to be inclined with respect to the tire circumferential direction and arranged side by side in the tire width direction.
With
The inclination angle of an acute angle with respect to the tire circumferential direction of the lateral grooves, minimum at the land portion closer to the tire equatorial plane, rather magnitude as the land portion near the outer side in the tire width direction,
In a no-load state assembled on a regular rim and filled with regular internal pressure, the tire radial dimensional difference at both ends of the land portion in the tire width direction is smaller as it is closer to the tire equatorial plane, larger as it is closer to the outside in the tire width direction, and is the largest tire. The relationship between the tire radial dimensional difference Do of the land portion on the outer side in the width direction and the tire radial dimensional difference Dm of the land portion adjacent to the inner side in the tire width direction is Do / Dm ≧ 1.5. Pneumatic tires featuring. In the tread portion, cords extending along the tire circumferential direction are arranged side by side in the tire width direction, and the circumferential belt is arranged in the tire width direction including the position of the tire equatorial plane.
The tread surface of the tread portion extends along the tire circumferential direction and is provided side by side in the tire width direction. The central circumferential groove arranged on the tire equatorial plane and the outermost circumference arranged on the outermost side in the tire width direction. A circumferential groove including a directional groove, an intermediate circumferential groove arranged between the central circumferential groove and the outer circumferential groove, and
At least three land portions divided in the tire width direction by the intermediate circumferential groove between the central circumferential groove and the outer circumferential groove.
In each of the land portions, both ends are opened in the circumferential groove adjacent to the tire width direction, and the lateral grooves are provided so as to be inclined with respect to the tire circumferential direction and arranged side by side in the tire width direction.
With
The inclination angle of an acute angle with respect to the tire circumferential direction of the lateral grooves, minimum at the land portion closer to the tire equatorial plane, rather magnitude as the land portion near the outer side in the tire width direction,
The land portion is formed with a plurality of blocks partitioned by the two circumferential grooves adjacent in the tire width direction and the two lateral grooves adjacent in the tire circumferential direction, and are adjacent to each other in the tire circumferential direction. A small block in which the block is divided in the tire width direction is formed by a narrow groove having both ends opened in the two lateral grooves.
In the block, most the closer to the tire equatorial plane and the small block area S _I of the relationship between the surface area S _O of the small blocks closest to the tire width direction outside, is S O _/ S _I ≧ 1.01 pneumatic tire, characterized in that,. The inflated groove according to claim 1 or 2 , wherein the difference in inclination angles between the two adjacent land portions in the tire width direction is larger as it is closer to the tire equatorial plane and smaller as it is closer to the outside in the tire width direction. tire. The region partitioned between the outer circumferential grooves is defined as a center region, and the relationship between the tire width direction dimension Wf of the center region and the tire width direction dimension Wg of the circumferential belt is Wg / Wf ≧ 1.03. The pneumatic tire according to any one of claims 1 to 3 . The land portion is formed with a plurality of blocks partitioned by two adjacent circumferential grooves in the tire width direction and two adjacent lateral grooves in the tire circumferential direction, and the tire circumferential direction of each block is formed. The pneumatic tire according to any one of claims 1 to 4 , wherein the aspect ratio between the dimension L and the tire width direction dimension We is 1.2 ≦ L / We ≦ 2.0.

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