JP7024465B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

In pneumatic tires, a plurality of grooves are formed on the tread surface for the purpose of draining water between the tread surface and the road surface when traveling on a wet road surface, but the grooves on the tread surface have an action other than drainage. May cause. For example, in the groove on the tread surface, a stone may enter and the groove may bite the stone. Therefore, in the pneumatic tire described in Patent Document 1, the lug groove depth of the central land row and the second land row The depth of the rug groove is shallower than the depth of the main groove, and the depth of the lug groove of the second land row is shallower than the depth of the lug groove of the central land row. We are trying to improve the biteability and uneven wear resistance.

Japanese Patent No. 5059383

Here, among the pneumatic tires, there are so-called studless tires having improved running performance on ice or snow. Since studless tires are not only used on ice and snow roads in winter, but are often used all year round, not only performance on ice and snow but also comprehensive performance with a good balance of uneven wear resistance and fuel efficiency is required. Has been done. In such studless tires, it is common practice to increase the groove volume or arrange a large number of sipes in order to improve the performance on ice and snow. However, when the groove volume is increased or a large number of sipes are arranged, the block rigidity is lowered, so that uneven wear is likely to occur.

In addition, the ground contact characteristics of pneumatic tires change depending on the weight of the vehicle during traveling, but especially for trucks and buses where the difference between the weight when the cargo is not loaded and the weight when the cargo is loaded is large. The change in ground contact characteristics with the change in the weight of the vehicle is remarkable. For example, in a truck or a bus, when an empty vehicle is not loaded with cargo, the contact area of the pneumatic tire with the road surface is smaller than that when the vehicle is loaded with cargo. In this case, since the number of grooves located in the ground contact area is reduced, the studless tires used for relatively large vehicles such as trucks and buses tend to deteriorate the traction performance on the snowy road surface when the vehicle is empty. Traction performance on snowy roads can be ensured by increasing the groove volume and sipes, but if the groove volume and sipes are increased, uneven wear is likely to occur. It was very difficult to achieve both.

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 achieving both ice and snow performance and uneven wear resistance.

In order to solve the above-mentioned problems and achieve the object, the pneumatic tire according to the present invention has the tire equatorial line in the tire width direction across the tire equatorial plane among a plurality of circumferential main grooves extending in the tire circumferential direction. The two inner circumferential main grooves, which are the circumferential main grooves arranged on both sides of the surface, and the circumferential main groove arranged on the outer side of each of the two inner circumferential main grooves in the tire width direction. Of the outer peripheral main groove which is a groove and a plurality of lug grooves extending in the tire width direction, a central lug groove arranged between the two inner peripheral main grooves and a plurality of lug grooves extending in the tire width direction. Among the lug grooves, an intermediate lug groove arranged between the inner peripheral main groove and the outer peripheral main groove adjacent to each other in the tire width direction, two inner peripheral main grooves and the said. A central block partitioned by a central lug groove and an intermediate block partitioned by the inner circumferential main groove, the outer circumferential main groove, and the intermediate lug groove are provided, and the central lug groove and the intermediate lug are provided. Each groove has one or more groove wall bent portions, which are portions where the angle in the groove width direction with respect to the depth direction of the lug groove changes, and the groove wall bent portion has the groove wall bent portion. The distance from the tread tread in the groove depth direction of the lug groove to the groove wall bending portion closest to the tread tread is larger than that of the groove wall bending portion formed in the groove wall of the intermediate lug groove. The groove wall bent portion formed on the groove wall of the groove is characterized in that it is larger.

Further, in the pneumatic tire, it is preferable that the central lug groove and the intermediate lug groove have the same groove depth.

Further, in the pneumatic tire, it is preferable that the central lug groove and the intermediate lug groove have a deeper groove depth in the intermediate lug groove than in the central lug groove.

Further, in the pneumatic tire, the distance between the central lug groove and the intermediate lug groove from the tread tread to the groove wall bending portion closest to the tread tread in the groove depth direction is the groove depth. It is preferably in the range of 65% or more and 90% or less.

Further, in the pneumatic tire, it is preferable that the groove depth of the central lug groove and the intermediate lug groove is within a range of 65% or more and 85% or less of the groove depth of the circumferential main groove, respectively.

Further, in the pneumatic tire, it is preferable that the width of the central block in the tire width direction is within a range of 15% or more and 30% or less of the tread development width.

Further, in the pneumatic tire, it is preferable that the central lug groove is formed at two or more extending direction bending portions, which are portions where the angle in the tire circumferential direction with respect to the tire width direction changes.

Further, in the pneumatic tire, it is preferable that the pitch of the central lug groove in the tire peripheral direction is within a range of 1% or more and 3% or less of the tire peripheral length.

Further, in the pneumatic tire, it is preferable that the contact area of the central block is within a range of 1.8 times or more and 2.3 times or less the contact area of the intermediate block.

Further, in the pneumatic tire, a central fine groove extending in the tire circumferential direction with a groove width narrower than the groove width of the lug groove is formed between the two inner circumferential main grooves, and the central block is formed. It is preferable that the tire is divided into two in the tire width direction by the central narrow groove.

Further, in the pneumatic tire, the central lug groove and the intermediate lug groove that open with respect to the same inner peripheral direction main groove have an opening position with respect to the inner peripheral direction main groove of 0.5 of the tire peripheral length. It is preferable that the tires are arranged so as to be offset in the tire peripheral direction within the range of% or more and 1.0% or less.

Further, in the pneumatic tire, the groove depth of the outer circumferential main groove is preferably in the range of 155% or more and 185% or less with respect to the groove width.

Further, in the pneumatic tire, the shoulder lug groove, which is the lug groove extending in the tire width direction, and the outer peripheral main groove and the shoulder lug groove are formed on the outer side of the outer peripheral direction main groove in the tire width direction. A row of shoulder blocks having shoulder blocks to be partitioned is arranged, and the intermediate lug groove and the shoulder lug groove that open to the same outer peripheral main groove have an opening position with respect to the outer peripheral main groove. It is preferable that the tires are arranged so as to be offset in the tire circumference direction within a range of 0.5% or more and 1.0% or less of the tire circumference.

Further, in the pneumatic tire, a shoulder narrow groove extending in the tire circumferential direction with a groove width narrower than the groove width of the lug groove is formed on the outer side of the outer peripheral direction main groove in the tire width direction, and the shoulder block row. Is preferably divided into two in the tire width direction by the shoulder narrow groove.

Further, in the pneumatic tire, the groove depth of the shoulder narrow groove is preferably in the range of 55% or more and 65% or less with respect to the groove depth of the outer peripheral direction main groove.

Further, in the pneumatic tire, the shoulder lug groove preferably has a groove depth within a range of 75% or more and 85% or less with respect to the groove depth of the central lug groove.

Further, in the pneumatic tire, it is preferable that the intermediate block is arranged so as to be offset in the tire circumferential direction with respect to the central block and the shoulder block.

Further, in the pneumatic tire, it is preferable that the intermediate block and the shoulder block are chamfered with a depth of 5 mm or more at a portion where the outer circumferential main groove and the lug groove intersect.

Further, in the pneumatic tire, at least four sipes including open sipes having both ends opened at the ends of the blocks are arranged in the central block and the intermediate block, and the open sipes have a sipe length. It is preferable that the sipe has a three-dimensional shape that oscillates in the sipe width direction with respect to both the radial direction and the sipe depth direction.

The pneumatic tire according to the present invention has an effect that both performance on ice and snow and uneven wear resistance can be achieved at the same time.

FIG. 1 is a plan view showing a tread tread of a pneumatic tire according to an embodiment. FIG. 2 is a detailed view of part A of FIG. FIG. 3 is a detailed view of part B of FIG. FIG. 4 is a sectional view taken along the line CC of FIG. FIG. 5 is a cross-sectional view taken along the line DD of FIG. FIG. 6 is a detailed view of the F portion of FIG. FIG. 7 is a modification of the pneumatic tire according to the embodiment, and is an explanatory view when the relative angle between the groove walls on both sides of the groove wall bending portion bends more than 180 °. FIG. 8 is a modified example of the pneumatic tire according to the embodiment, and is an explanatory view in the case where the groove wall bending portion is formed only on one groove wall. FIG. 9 is a modification of the pneumatic tire according to the embodiment, and is an explanatory view when a plurality of groove wall bending portions are formed on one groove wall. FIG. 10 is a modification of the pneumatic tire according to the embodiment, and is an explanatory view when a plurality of groove wall bending portions are formed on one groove wall. FIG. 11 is a modification of the pneumatic tire according to the embodiment, and is an explanatory view when a plurality of groove wall bending portions are formed on one groove wall. FIG. 12 is a modified example of the pneumatic tire according to the embodiment, and is an explanatory view when a protrusion is formed on the groove bottom. FIG. 13A is a chart showing the results of the performance evaluation test of the pneumatic tire. FIG. 13B is a chart showing the results of the performance evaluation test of the pneumatic tire. FIG. 13C is a chart showing the results of the performance evaluation test of the pneumatic tire. FIG. 13D is a chart showing the results of the performance evaluation test of the pneumatic tire. FIG. 13E is a chart showing the results of the performance evaluation test of the pneumatic tire.

Hereinafter, embodiments of the pneumatic tire according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. Further, the components in the following embodiments include those that can be easily conceived by those skilled in the art, or those that are substantially the same.

[Embodiment]
In the following description, the tire radial direction refers to the direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial inner side is the side toward the rotation axis in the tire radial direction and the tire radial outer side. Refers to the side away from the axis of rotation in the tire radial direction. Further, the tire circumferential direction means a circumferential direction with the rotation axis as the central 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 in the tire width direction. The side away from the tire equatorial 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, and the tire equatorial plane CL is the center of the pneumatic tire 1 in the tire width direction. The position in the tire width direction coincides with the center line in the tire width direction, which is the position. The tire width is the width in the tire width direction between the outermost portions in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equatorial line is a line on the tire equatorial plane CL and along the tire circumferential direction of the pneumatic tire 1.

FIG. 1 is a plan view showing a tread tread 3 of a pneumatic tire 1 according to an embodiment. In the pneumatic tire 1 shown in FIG. 1, a tread portion 2 is arranged on the outermost portion in the tire radial direction, and the surface of the tread portion 2, that is, a vehicle on which the pneumatic tire 1 is mounted (not shown). ) Is formed as a tread tread 3 at a portion that comes into contact with the road surface during traveling. A plurality of circumferential main grooves 30 extending in the tire circumferential direction and a plurality of lug grooves 40 extending in the tire width direction are formed on the tread tread 3. The tread tread 3 is divided into a plurality of blocks 10 which are land portions by the plurality of circumferential main grooves 30 and lug grooves 40.

Specifically, four main grooves 30 in the circumferential direction are formed side by side in the tire width direction, and two inner grooves are arranged on both sides of the tire equatorial plane CL in the tire width direction with the tire equatorial plane CL interposed therebetween. A circumferential main groove 31 and two outer peripheral main grooves 32 arranged one on the outer side of each of the two inner peripheral main grooves 31 in the tire width direction are provided. Further, the lug groove 40 includes a central lug groove 41 arranged between two inner peripheral main grooves 31, an inner peripheral main groove 31 adjacent to each other in the tire width direction, and an outer peripheral main groove 32. An intermediate lug groove 42 is provided between the two, and a shoulder lug groove 43 is provided on the outer side of the outer peripheral direction main groove 32 in the tire width direction.

The circumferential main groove 30 here means a vertical groove having at least a part extending in the tire circumferential direction. Generally, the circumferential main groove 30 has a groove width of 5.0 mm or more, a groove depth of 7.5 mm or more, and has a treadware indicator (slip sign) indicating the end of wear inside. In the present embodiment, the circumferential main groove 30 has a groove width of 5.0 mm or more and a groove depth of 10 mm or more, and the tire equatorial line where the tire equatorial surface CL and the tread tread 3 intersect. It is substantially parallel to (center line). The circumferential main groove 30 may extend linearly in the circumferential direction of the tire, or may be provided in a wavy shape or a zigzag shape. Further, the lug groove 40 has a groove width of 5.0 mm or more and 10 mm or less, and a groove depth of 10 mm or more and 20 mm or less.

A plurality of blocks 10 are formed on the tread tread 3 by a plurality of circumferential main grooves 30 and a lug groove 40. Specifically, between the two inner circumferential main grooves 31, a central block 11 which is a block 10 partitioned by the two inner circumferential main grooves 31 and the central lug groove 41 is arranged. Further, between the inner peripheral direction main groove 31 and the outer peripheral direction main groove 32 adjacent to each other in the tire width direction, the inner peripheral direction main groove 31, the outer peripheral direction main groove 32, and the intermediate lug groove 42 are partitioned. An intermediate block 12 which is a block 10 is arranged. Further, on the outer side of the outer peripheral direction main groove 32 in the tire width direction, a shoulder block 13, which is a block 10 partitioned by the outer peripheral direction main groove 32 and the shoulder lug groove 43, is arranged.

The plurality of blocks 10 formed on the tread tread 3 as described above form a block row by arranging in the tire circumferential direction between the circumferential main grooves 30 adjacent to each other in the tire circumferential direction. That is, the central block 11 forms the central block row 21 between the two inner peripheral main grooves 31 by arranging a plurality of the central blocks 11 in the tire circumferential direction. Further, the intermediate block 12 forms an intermediate block row 25 between the inner peripheral main groove 31 and the outer peripheral main groove 32 adjacent to each other in the tire width direction by arranging a plurality of the intermediate blocks 12 in the tire circumferential direction. Further, a plurality of shoulder blocks 13 are arranged in the tire circumferential direction to form a shoulder block row 26 on the outer side of the outer peripheral main groove 32 in the tire width direction.

Further, the tread tread 3 is formed with a circumferential fine groove 50 extending in the tire circumferential direction with a groove width narrower than the groove width of the circumferential main groove 30 and the groove width of the lug groove 40. Specifically, the circumferential fine groove 50 is arranged on the outer side in the tire width direction of the central fine groove 51 arranged between the two inner peripheral main grooves 31 and the outer peripheral main groove 32. A shoulder narrow groove 52 is provided. That is, the central fine groove 51 is formed in the central block row 21 located between the two inner peripheral main grooves 31, and the shoulder narrow groove 52 is located outside the outer peripheral main groove 32 in the tire width direction. It is formed in the shoulder block row 26. The circumferential fine groove 50 referred to here has a groove width within a range of 1 mm or more and 5 mm or less, and a groove depth within a range of 10 mm or more and 15 mm or less.

Of the circumferential fine grooves 50 formed as described above, the central fine groove 51 is arranged between the two inner peripheral main grooves 31 and substantially near the center in the tire width direction, and is located near the center of the tire equatorial line. It is located on the surface CL or in the vicinity of the tire equatorial surface CL. Both ends of the central fine groove 51 formed in this way in the tire circumferential direction are open to the central lug groove 41. That is, the central fine groove 51 is formed so as to extend in the tire circumferential direction between the central lug grooves 41 adjacent to each other in the tire circumferential direction, and both ends are opened in the central lug groove 41, respectively.

Further, the shoulder narrow groove 52 is arranged near the center in the tire width direction between the main groove 32 in the outer peripheral direction and the design end E which is the outer end of the tread tread 3 in the tire width direction. The design end E referred to here refers to the outermost end in the tire width direction of the tread portion 2, and is the outermost end in the tire width direction in which the groove is formed in the tread portion 2. The shoulder narrow groove 52 formed in this way extends in the tire circumferential direction and repeatedly bends in the tire width direction. That is, the shoulder narrow groove 52 has a zigzag shape that extends in the tire circumferential direction and repeatedly bends in the tire width direction, and extends in the tire circumferential direction.

Further, a plurality of sipes 60 are formed in each block 10 formed on the tread tread 3, and in particular, at least four sipes 60 including an open sipes 61 are formed in the central block 11 and the intermediate block 12. It is arranged. The sipes 60 formed in each block 10 are formed by repeatedly bending in the tire circumferential direction while extending in the tire width direction.

The sipe 60 referred to here is formed in a fine groove shape on the tread tread 3, and the pneumatic tire 1 is rim-assembled on a regular rim to form a narrow groove under normal internal pressure internal pressure conditions and no load. When the fine grooves are located on the ground plane formed on the flat plate when the wall surface is not in contact with each other but when the load is applied in the vertical direction on the flat plate, or when the land part where the fine grooves are formed collapses. It means that the wall surfaces constituting the narrow groove or at least a part of the portion provided on the wall surface come into contact with each other due to the deformation of the land portion. The regular rim is a "standard rim" specified by JATMA, 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. In the present embodiment, the sipe 60 has a width of less than 1 mm and a depth of 5.0 mm or more and 15 mm or less.

FIG. 2 is a detailed view of part A of FIG. The central lug groove 41 arranged between the two inner peripheral direction main grooves 31 is open to the inner peripheral direction main grooves 31 having different ends in the tire width direction. Further, the central lug groove 41 is formed by bending in the tire circumferential direction at a plurality of points while extending in the tire width direction, that is, the central lug groove 41 has an angle in the tire circumferential direction with respect to the tire width direction. The extending direction bending portion 45, which is a portion where the tire changes, is formed at two or more locations.

In the present embodiment, the extending direction bending portions 45 are formed at two positions with respect to one central lug groove 41. The bending directions of the two extending direction bending portions 45 when facing from one inner circumferential main groove 31 side to the other inner circumferential main groove 31 side along the central lug groove 41 are opposite to each other. As a result, the central lug groove 41 is formed in a crank-like shape. Further, in the central lug groove 41 formed in a crank shape, each of the portions extending from the two extending direction bending portions 45 toward the inner peripheral direction main groove 31 is inclined with respect to the tire width direction. The direction of inclination and the angle of inclination are two portions extending from the bending portion 45 in the extending direction toward the main groove 31 in the inner peripheral direction, and have the same direction and angle as each other. The plurality of central lug grooves 41 arranged between the two inner circumferential main grooves 31 are all formed in the same shape.

In the central lug groove 41 formed in this way, the pitch Pc in the tire peripheral direction is within the range of 1% or more and 3% or less of the tire peripheral length. The tire circumference is the length in the tire circumference direction on the tread tread 3 at the position of the tire equatorial plane CL. In the present embodiment, since the central narrow groove 51 and the central lug groove 41 are formed on the tire equatorial surface CL, the tire circumference is such that the tread tread 3 of the central block 11 is on the central fine groove 51 or the central lug groove. It is measured as being extended to the top of 41. In the central lug groove 41, the pitch Pc of the central lug groove 41, which is the distance between the central lug grooves 41 adjacent to each other in the tire circumferential direction in the tire circumferential direction, is 1% or more with respect to the tire circumference measured in this way. It is within the range of 3% or less.

Further, the central block 11 is divided into two in the tire width direction by a central fine groove 51 formed between two main grooves 31 in the inner peripheral direction. That is, the central narrow groove 51 opens at both ends in the tire circumferential direction with respect to the central lug groove 41 that divides both sides of the central block 11 in the tire circumferential direction at a position near the center in the tire width direction of the central block 11. Therefore, the central block 11 is divided into two in the tire width direction by the central narrow groove 51. Each portion of the central block 11 divided into two by the central fine groove 51 is a divided central block 11a, and the divided central blocks 11a are formed on both sides of the central fine groove 51 in the tire width direction. That is, the divided central block 11a is partitioned by a main groove 31 in the inner peripheral direction, a central lug groove 41, and a central fine groove 51, respectively.

The central block row 21 formed by arranging a plurality of central blocks 11 side by side in the tire circumferential direction is formed by dividing each central block 11 into two divided central blocks 11a by a central fine groove 51. The central block row 21 itself is also divided into two divided block rows 22 by the central narrow groove 51. In this case, the divided block row 22 is a block row formed by arranging a plurality of divided central blocks 11a in the tire circumferential direction.

The central narrow groove 51, which divides the central block 11 and whose end portion opens in the central lug groove 41, opens with respect to the extending direction bending portion 45 of the central lug groove 41. Further, the central fine groove 51 is formed so that the groove depth is within a range of 50% or more and 75% or less with respect to the groove depth of the main groove 31 in the inner peripheral direction.

Since the central fine groove 51 is open to the bending portion 45 in the extending direction of the central lug groove 41, the divided central blocks 11a located on both sides of the central fine groove 51 in the tire width direction are mutually in the tire circumferential direction. It is arranged at an offset. That is, since the central lug groove 41 for partitioning the divided central block 11a is formed in a crank shape, the positions of the bending portions 45 in the extending direction in the central lug groove 41 in the tire circumferential direction are located on both sides in the tire width direction. It's different. Since the central narrow groove 51 is open to the extending direction bending portion 45 of the central lug groove 41 formed in such a crank shape, the central lug groove 41 is the extending direction bending portion 45. As the positions in the tire circumferential direction are different on both sides in the tire width direction, the divided central blocks 11a located on both sides in the tire width direction of the central narrow groove 51 also have the same in the tire circumferential direction as the central lug groove 41. The position is different. As a result, the divided central blocks 11a located on both sides of the central narrow groove 51 in the tire width direction are arranged so as to be offset in the tire circumferential direction.

Further, the inner peripheral direction main groove 31 is formed by repeatedly bending in the tire width direction while extending in the tire circumferential direction, whereby the central block 11 is formed at both ends in the tire width direction and outward in the tire width direction. A protruding portion 14 is formed. The protrusion 14 formed in the central block 11 is formed at a position closer to one of the central lug grooves 41 in the portion of the central block 11 partitioned by the inner circumferential main groove 31.

That is, since the central block 11 is partitioned by the inner peripheral direction main groove 31 and the central lug groove 41, both sides of the portion of the central block 11 partitioned by the inner peripheral direction main groove 31 in the tire circumferential direction are Each central lug groove 41 is arranged, and each central lug groove 41 is open to the inner peripheral direction main groove 31. The protrusion 14 is formed in the vicinity of one of the central lug grooves 41 in the tire circumferential direction among the portions thus partitioned by the inner circumferential main groove 31 in the central block 11. Further, the protrusions 14 formed at two positions on both sides of one central block 11 in the tire width direction are formed in the vicinity of the central lug grooves 41 which are different from each other. The protrusion 14 formed in this way has a length in the tire circumferential direction of 50% or less of the length in the tire circumferential direction of the portion partitioned by the inner peripheral main groove 31.

Further, two open sipes 61 and two closed sipes 62 are formed in the central block 11. Of these, the open sipe 61 is a sipe 60 in which both ends of the sipe 60 in the length direction are opened at the ends of the block. The end of the block in this case also includes the end of the divided central block 11a, which is a block in which the central block 11 is divided by the central narrow groove 51. That is, the open sipe 61 formed in the central block 11 has one end in the length direction of the sipe 60 opened at the end portion defined by the central block 11 or the inner peripheral main groove 31 in the divided central block 11a, and the other. The ends are open at the ends partitioned by the central groove 51 in the split central block 11a.

Further, the closed sipe 62 is a sipe 60 whose both ends in the length direction of the sipe 60 are terminated in the block 10, and in the central block 11 divided into two by the central narrow groove 51, the closed sipe 62 is a sipe. Both ends in the length direction of 60 are terminated within the split central block 11a. In the present embodiment, in the central block 11, two open sipes 61 arranged in the tire circumferential direction and two open sipes 61 arranged on both sides of the open sipes 61 in the tire circumferential direction are arranged in each divided central block 11a. Four sipe 60s with the closed sipe 62 of the above are formed.

Of the sipes 60 formed in the central block 11, the open sipes 61 are so-called three-dimensional sipes that oscillate in the sipes width direction with respect to both the sipes length direction and the sipes depth direction. It is a sipe. That is, the open sipe 61, which is a three-dimensional sipe, has an amplitude in the sipe width direction in both the cross-sectional view with the sipe length direction as the normal direction and the cross-sectional view with the sipe depth direction as the normal direction. It has a curved sipe wall surface. Further, the open sipe 61 is bent at five or more points while extending in the tire width direction on the tread tread surface 3.

Further, the closed sipe 62 is a so-called two-dimensional sipe, which is a two-dimensional sipe that extends straight without bending when extending in the tire width direction or in the tire depth direction. That is, the closed sipe 62, which is a two-dimensional sipe, has a straight sipe wall surface in an arbitrary cross-sectional view (cross-sectional view including the sipe width direction and the sipe depth direction) with the sipe length direction as the normal. is doing. In the present embodiment, the closed sipe 62 is repeatedly bent a plurality of times in the tire circumferential direction while extending in the tire width direction, and has the same shape as the shape appearing on the tread tread tread 3 from the opening portion to the tread tread tread 3 to the sipe bottom. Is formed up to.

The width Wc of the central block 11 formed as described above is within a range of 15% or more and 30% or less of the tread development width TDW (see FIG. 1) in the tire width direction. In this case, the width Wc of the central block 11 in the tire width direction is the distance in the tire width direction between the portions of the protrusions 14 formed on both sides of the central block 11 in the tire width direction, which are located on the outermost sides in the tire width direction. ing. The width Wc of the central block 11 in the tire width direction with respect to the tread development width TDW is preferably in the range of 20% or more and 25% or less.

FIG. 3 is a detailed view of part B of FIG. The circumferential groove 50 is not formed in the intermediate block row 25, and the intermediate block row 25 is a single row of block rows formed by arranging a plurality of intermediate blocks 12 in the tire circumferential direction. The intermediate lug groove 42 formed in the intermediate block row 25 configured in this manner and arranged between the adjacent inner circumferential main groove 31 and the outer circumferential main groove 32 has both ends in the inner circumferential main groove. It is open to 31 and the outer circumferential main groove 32. Specifically, in the intermediate lug groove 42, the inner end portion in the tire width direction is opened in the inner peripheral direction main groove 31, and the outer end portion in the tire width direction is opened in the outer peripheral direction main groove 32. In this way, the intermediate lug groove 42 that opens in the inner peripheral direction main groove 31 and the outer peripheral direction main groove 32 and extends in the tire width direction has a pitch Pm in the tire circumferential direction in the tire circumferential direction of the central lug groove 41. It is almost the same size as the pitch Pc.

Further, the central lug groove 41 and the intermediate lug groove 42 that open with respect to the same inner peripheral direction main groove 31 have an opening position with respect to the inner peripheral direction main groove 31 of 0.5% or more and 1.0% of the tire peripheral length. They are arranged so as to be offset in the tire circumferential direction within the following range. That is, the central lug groove 41 and the intermediate lug groove 42 that open with respect to the same inner peripheral direction main groove 31 are the opening 41a of the central lug groove 41 with respect to the inner peripheral direction main groove 31 and the inner circumference in the intermediate lug groove 42. The distance Lc in the tire circumferential direction from the opening 42a with respect to the directional main groove 31 is within the range of 0.5% or more and 1.0% or less of the tire peripheral length. In this case, the distance Lc between the opening 41a of the central lug groove 41 and the opening 42a of the intermediate lug groove 42 in the tire circumferential direction is from the opening 41a of each central lug groove 41 or the opening 42a of the intermediate lug groove 42. As seen, it is the distance between the closest openings 41a and 42a in the tire circumferential direction.

As described above, the central lug groove 41 of the central block row 21 and the intermediate lug groove 42 of the intermediate block row 25 have substantially the same pitch in the tire circumferential direction and are displaced from each other in the tire circumferential direction. In the intermediate block row 25 in which a plurality of intermediate blocks 12 partitioned by the intermediate lug grooves 42 are arranged side by side in the tire circumferential direction, the intermediate block row 25 is also arranged in the tire circumferential direction with respect to the central block row 21. It is arranged so that it is offset from the tire. That is, the intermediate block row 25 is arranged so as to be offset in the tire peripheral direction within a range of 0.5% or more and 1.0% or less of the tire peripheral length with respect to the central block row 21. Therefore, the central block 11 constituting the central block row 21 and the intermediate block 12 constituting the intermediate block row 25 are arranged so as to be relatively offset in the tire circumferential direction.

Further, the distance Lc between the opening 41a of the central lug groove 41 and the opening 42a of the intermediate lug groove 42 in the tire circumferential direction is 30% or more and 50% with respect to the pitch Pc in the tire circumferential direction of the central lug groove 41. It is within the following range. The intermediate lug groove 42, which is arranged so as to be displaced in the tire circumferential direction with respect to the central lug groove 41, extends in the tire width direction and is inclined in the tire circumferential direction with respect to the tire width direction. The inclination direction of the intermediate lug groove 42 in the tire circumferential direction is opposite to the inclination direction of the portion of the central lug groove 41 between the extending direction bending portion 45 and the inner circumferential main groove 31. Further, the intermediate lug grooves 42 arranged on both sides of the tire equatorial surface CL in the tire width direction have the same inclination directions in the tire circumferential direction with respect to the tire width direction.

Further, the inner peripheral direction main groove 31 is formed by repeatedly bending in the tire width direction while extending in the tire peripheral direction, so that the protruding portion 15 is formed in the intermediate block 12 as well as the central block 11. .. The protrusion 15 of the intermediate block 12 is also formed on the side partitioned by the outer circumferential main groove 32. That is, the intermediate block 12 has a protrusion 15 formed on the side partitioned by the inner peripheral main groove 31 in the intermediate block 12 and projecting inward in the tire width direction, and the outer peripheral main groove 32 in the intermediate block 12. A protruding portion 15 formed on the side to be partitioned and projecting outward in the tire width direction is formed. As described above, the protrusions 15 formed at two locations on both sides of the intermediate block 12 in the tire width direction have the two protrusions 15 each other as the tire circumference of the intermediate block 12, similar to the protrusions 14 of the central block 11. Of the intermediate lug grooves 42 arranged on both sides in the direction, the intermediate lug grooves 42 are formed in the vicinity of the intermediate lug grooves 42 which are different from each other.

Further, two open sipes 61 and two closed sipes 62 are formed in the intermediate block 12. The open sipe 61 formed in the intermediate block 12 has one end in the length direction of the sipe 60 opened at the end partitioned by the inner circumferential main groove 31 in the intermediate block 12, and the other end is the outer side in the intermediate block 12. It is open at the end partitioned by the circumferential main groove 32. The closed sipe 62 formed in the intermediate block 12 is terminated in the intermediate block 12 at both ends in the length direction of the sipe 60. In the present embodiment, the intermediate block 12 includes two open sipes 61 arranged in the tire circumferential direction and two closed sipes 62 arranged one on each side of the open sipes 61 in the tire circumferential direction. Book sipes 60 are formed.

Further, as for the sipe 60 formed in the intermediate block 12, the open sipe 61 is a three-dimensional sipe and the closed sipe 62 is a two-dimensional sipe, similarly to the sipe 60 formed in the central block 11. Further, the open sipe 61 is bent at five or more points while extending in the tire width direction on the tread tread surface 3.

The width Wm of the intermediate block 12 formed as described above is within a range of 7% or more and 15% or less of the tread development width TDW (see FIG. 1) in the tire width direction. In this case, the width Wm of the intermediate block 12 in the tire width direction is the tire between the portions located on the innermost side in the tire width direction and the outermost part in the tire width direction in the protrusions 15 formed on both sides of the intermediate block 12 in the tire width direction. It is the distance in the width direction.

The width of the central block 11 and the intermediate block 12 are different in the tire width direction, and the pitch Pc of the central lug groove 41 in the tire circumferential direction and the pitch Pm of the intermediate lug groove 42 in the tire circumferential direction are almost the same size. Therefore, the ground contact areas are different from each other. Specifically, the ground contact area of the central block 11 is within the range of 1.8 times or more and 2.3 times or less with respect to the ground contact area of the intermediate block 12. The ground contact area in this case is the area of the portion actually grounded when the block 10 is grounded, that is, the area obtained by excluding the area of the groove located in this region from the area of the region where the block 10 is formed. ing.

FIG. 4 is a sectional view taken along the line CC of FIG. FIG. 5 is a cross-sectional view taken along the line DD of FIG. The central lug groove 41 for partitioning the central block 11 and the intermediate lug groove 42 for partitioning the intermediate block 12 have the same groove depth. That is, the central lug groove 41 and the intermediate lug groove 42 have the same groove depth Dc of the central lug groove 41 and the groove depth Dm of the intermediate lug groove 42. The central lug groove 41 and the intermediate lug groove 42 do not have to have exactly the same groove depth, and the difference between the groove depths of both lug grooves 40 is within ± 5%. good. In other words, the difference between the central lug groove 41 and the intermediate lug groove 42 between the groove depth Dc of the central lug groove 41 and the groove depth Dm of the intermediate lug groove 42 is within ± 5%. That is, when the difference between the groove depths of the central lug groove 41 and the intermediate lug groove 42 is within ± 5%, the groove depths of the central lug groove 41 and the intermediate lug groove 42 are the same. It shall be.

Further, the central lug groove 41 and the intermediate lug groove 42, which are formed at the same groove depth as described above, have a groove depth of 65% or more and 85% of the groove depth of the circumferential main groove 30, respectively. It is within the following range. That is, the central lug groove 41 and the intermediate lug groove 42 have the groove depth Dc of the central lug groove 41 with respect to both the groove depth of the inner peripheral direction main groove 31 and the groove depth of the outer peripheral direction main groove 32. And the groove depth Dm of the intermediate lug groove 42 are within the range of 65% or more and 85% or less, respectively. The groove depth Dc of the central lug groove 41 and the groove depth Dm of the intermediate lug groove 42 are preferably in the range of 70% or more and 80% or less of the groove depth of the circumferential main groove 30, respectively.

Further, the central lug groove 41 and the intermediate lug groove 42 each have one or more groove wall bent portions 47, which are portions where the angle of the lug groove 40 in the groove width direction with respect to the depth direction changes. is doing. The groove wall bent portion 47 has a cross section including the central lug groove 41 and the intermediate lug groove 42 in the groove width direction and the groove depth direction of each groove, that is, a cross section in which each groove is viewed in the extending direction of the groove. , The groove wall 46 is a bent portion.

In the present embodiment, in the central lug groove 41, one groove wall bending portion 47 is formed on both of the facing groove walls 46, and the central lugs of the groove wall bending portions 47 of the facing groove walls 46 are formed. The positions of the grooves 41 in the groove depth direction are the same as each other. Similarly, in the intermediate lug groove 42, one groove wall bending portion 47 is formed on each of the facing groove walls 46, and the intermediate lug groove 42 between the groove wall bending portions 47 of the facing groove walls 46 is formed. The positions in the groove depth direction are the same as each other.

Further, the groove wall bending portion 47 of the central lug groove 41 and the groove wall bending portion 47 of the intermediate lug groove 42 both reduce the groove width of the lug groove 40 when going from the tread tread 3 to the groove wall bending portion 47. It is bent so that the degree to which the groove width becomes smaller when going from the groove wall bent portion 47 to the groove bottom 48 is larger than that. That is, the relative angle between the groove wall bent portion 47 of the central lug groove 41 and the groove wall bent portion 47 of the intermediate lug groove 42 is less than 180 ° between the portions located on both sides of the groove wall bent portion 47 in the groove wall 46. The portion of the groove wall 46 on the groove bottom 48 side of the groove wall 46 is closer to the opposite groove wall 46 than the portion of the groove wall 46 on the tread tread 3 side of the groove wall bend 47. The groove wall 46 is bent in a direction in which the groove wall 46 is greatly inclined in the direction.

As described above, the groove wall bending portion 47 formed in both the central lug groove 41 and the intermediate lug groove 42 has a distance from the tread tread 3 to the groove wall bending portion 47 in the groove depth direction of the lug groove 40. The groove wall bending portion 47 formed in the groove wall 46 of the central lug groove 41 is larger than the groove wall bending portion 47 formed in the groove wall 46 of the intermediate lug groove 42. That is, the distance DBc from the tread tread 3 in the groove depth direction of the central lug groove 41 to the groove wall bent portion 47 of the central lug groove 41 is from the tread tread 3 in the groove depth direction of the intermediate lug groove 42 to the intermediate lug groove 42. The distance to the groove wall bent portion 47 is larger than the distance DBm. Specifically, the distance DBc from the tread tread 3 of the central lug groove 41 to the groove wall bent portion 47 and the distance DBm from the tread tread 3 of the intermediate lug groove 42 to the groove wall bent portion 47 are 0.7 ≦. The relationship is within the range of (DBm / DBc) <1.

Further, in the central lug groove 41 and the intermediate lug groove 42, the distance from the tread tread 3 to the groove wall bent portion 47 in the groove depth direction is within a range of 65% or more and 90% or less of the groove depth, respectively. There is. That is, in the central lug groove 41, the distance DBc from the tread tread 3 to the groove wall bent portion 47 in the groove depth direction of the central lug groove 41 is 65% or more and 90% or less of the groove depth Dc of the central lug groove 41. It is within the range. Similarly, in the intermediate lug groove 42, the distance DBm from the tread tread 3 to the groove wall bent portion 47 in the groove depth direction of the intermediate lug groove 42 is 65% or more and 90% or less of the groove depth Dm of the intermediate lug groove 42. It is within the range of.

In the central lug groove 41, the distance DBc from the tread tread 3 to the groove wall bent portion 47 in the groove depth direction of the central lug groove 41 is 70% or more and 80% or less of the groove depth Dc of the central lug groove 41. It is preferably within the range. Similarly, in the intermediate lug groove 42, the distance DBm from the tread tread 3 to the groove wall bent portion 47 in the groove depth direction of the intermediate lug groove 42 is 70% or more and 80% or less of the groove depth Dm of the intermediate lug groove 42. It is preferably within the range.

FIG. 6 is a detailed view of the F portion of FIG. The shoulder block row 26 arranged on the outer side of the main groove 32 in the outer peripheral direction in the tire width direction is divided into two in the tire width direction by the shoulder narrow groove 52. That is, the shoulder block row 26 is divided into two by the shoulder narrow groove 52, and has two block rows 27 adjacent to each other in the tire width direction via the shoulder narrow groove 52. Further, in the shoulder block row 26, the block row 27 outside the shoulder narrow groove 52 in the tire width direction is formed with a widthwise narrow groove 58 which is a narrow groove extending in the tire width direction.

The shoulder lug grooves 43 arranged on the outer side of the main groove 32 in the outer peripheral direction in the tire width direction are arranged on both sides of the shoulder narrow groove 52 in the tire width direction. That is, the shoulder lug grooves 43 are arranged in both block rows 27 arranged on both sides of the shoulder narrow grooves 52 in the tire width direction. Of the shoulder lug grooves 43, the shoulder lug groove 43 arranged inside the shoulder narrow groove 52 in the tire width direction has an inner end portion in the tire width direction opened in the outer peripheral direction main groove 32 and is outside in the tire width direction. The end of the tire is open in the shoulder groove 52. Further, the shoulder lug groove 43 arranged inside the shoulder narrow groove 52 in the tire width direction has a pitch in the tire circumferential direction that is substantially the same as the pitch Pm in the tire circumferential direction of the intermediate lug groove 42. .. Further, the shoulder lug groove 43 arranged inside the shoulder narrow groove 52 in the tire width direction has a groove depth within a range of 75% or more and 85% or less with respect to the groove depth of the central lug groove 41. It has become.

Further, of the shoulder lug grooves 43, the shoulder lug groove 43 arranged on the outer side of the shoulder narrow groove 52 in the tire width direction has an inner end portion in the tire width direction opened in the shoulder narrow groove 52 and is outer in the tire width direction. The end of the tire is open at the design end E. At that time, the end portion of the shoulder lug groove 43 on the side that is open to the shoulder narrow groove 52 is open to the bent portion of the shoulder narrow groove 52 that is formed in a zigzag shape.

Further, the shoulder lug grooves 43 arranged on both sides of the shoulder narrow groove 52 in the tire width direction are arranged at different positions in the tire circumferential direction between the shoulder lug grooves 43 on both sides of the shoulder narrow groove 52 in the tire width direction. It is set up.

Further, the widthwise groove 58 arranged on the outer side of the shoulder groove 52 in the tire width direction has an end portion on the inner side in the tire width direction at a bent portion of the shoulder groove 52 formed in a zigzag shape. It is opened, and the outer end in the tire width direction is opened at the design end E. On the outside of the shoulder narrow groove 52 in the tire width direction, the shoulder lug groove 43 extending in the tire width direction and the width direction narrow groove 58 are alternately arranged in the tire circumferential direction.

Of the two block rows 27 of the shoulder block row 26, the block row 27 located inside the shoulder narrow groove 52 in the tire width direction is partitioned by the outer circumferential main groove 32, the shoulder lug groove 43, and the shoulder narrow groove 52. A plurality of shoulder blocks 13 which are blocks 10 to be formed are lined up in the tire circumferential direction. Four closed sipes 62 are formed on each shoulder block 13. The closed sipe 62 formed on the shoulder block 13 is a two-dimensional sipe whose ends in the length direction of the sipe 60 are terminated within the shoulder block 13.

Further, the block row 27 located on the outer side of the shoulder narrow groove 52 in the tire width direction is a plurality of shoulders which are blocks 10 partitioned by the shoulder lug groove 43, the width direction fine groove 58, the shoulder narrow groove 52, and the design end E. The blocks 13 are lined up in the tire circumferential direction. Further, the shoulder blocks 13 of the two adjacent block rows 27 via the shoulder narrow groove 52 are arranged so as to be offset in the tire circumferential direction with respect to the shoulder blocks 13 of the other block row 27.

The outer circumferential main groove 32 that partitions the inner side of the shoulder block row 26 formed in the tire width direction has a groove depth within a range of 155% or more and 185% or less with respect to the groove width. Here, the outer peripheral main groove 32 is repeatedly bent in the tire width direction while extending in the tire peripheral direction, and the groove width also changes with the bending in the tire width direction. In this case, The groove width of the outer peripheral direction main groove 32 is the maximum width of the groove width of the outer peripheral direction main groove 32. The shoulder narrow groove 52 arranged on the outer side of the outer peripheral direction main groove 32 in the tire width direction has a groove depth in the range of 55% or more and 65% or less with respect to the groove depth of the outer peripheral direction main groove 32. It is inside.

Further, among the shoulder lug grooves 43, the shoulder lug groove 43 arranged inside the shoulder narrow groove 52 in the tire width direction has an inner end portion in the tire width direction opened in the outer peripheral direction main groove 32, but is the same. The intermediate lug groove 42 and the shoulder lug groove 43 that open with respect to the outer peripheral main groove 32 have an opening position with respect to the outer peripheral main groove 32 within a range of 0.5% or more and 1.0% or less of the tire peripheral length. It is arranged so as to be offset in the tire circumferential direction. That is, the intermediate lug groove 42 and the shoulder lug groove 43 that open to the same outer circumferential main groove 32 are the opening 42b for the outer circumferential main groove 32 in the intermediate lug groove 42 and the outer circumference in the shoulder lug groove 43. The distance Ls in the tire circumferential direction with respect to the opening 43a with respect to the directional main groove 32 is within the range of 0.5% or more and 1.0% or less of the tire peripheral length. In this case, the distance Ls between the opening 42b of the intermediate lug groove 42 and the opening 43a of the shoulder lug groove 43 in the tire circumferential direction is from the opening 42b of each intermediate lug groove 42 or the opening 43a of the shoulder lug groove 43. As seen, it is the distance between the closest openings 42b and 43a in the tire circumferential direction.

As described above, the intermediate lug groove 42 of the intermediate block row 25 and the shoulder lug groove 43 arranged inside the shoulder narrow groove 52 in the tire width direction have substantially the same pitch in the tire circumferential direction. Moreover, since the shoulder blocks 13 are arranged so as to be offset from each other in the tire circumferential direction, the shoulder block row 26 in which a plurality of shoulder blocks 13 partitioned by the shoulder lug grooves 43 are arranged side by side in the tire circumferential direction is also in the middle. It is arranged so as to be offset in the tire circumferential direction with respect to the block row 25. That is, the block row 27 located inside the shoulder narrow groove 52 in the shoulder block row 26 in the tire width direction is within a range of 0.5% or more and 1.0% or less of the tire circumference with respect to the intermediate block row 25. The tires are arranged so as to be offset in the circumferential direction. Therefore, the intermediate block 12 constituting the intermediate block row 25 and the shoulder block 13 constituting the block row 27 located inside the shoulder narrow groove 52 in the shoulder block row 26 in the tire width direction are relatively in the tire circumferential direction. It is arranged in a staggered manner.

Further, in the intermediate block 12 and the shoulder block 13 partitioned by the outer circumferential main groove 32, a chamfer 16 is formed at a portion where the outer circumferential main groove 32 and the lug groove 40 intersect. The chamfer 16 is formed so that the depth of the lug groove 40 from the tread tread 3 in the groove depth direction is 5 mm or more. Specifically, the chamfer 16 formed in the intermediate block 12 is formed at a portion where the intermediate lug groove 42 for partitioning the intermediate block 12 and the outer circumferential main groove 32 intersect, that is, the outer side in the intermediate block 12. It is formed in a portion where the opening 42b of the intermediate lug groove 42 with respect to the circumferential main groove 32 is located. Further, the chamfer 16 formed in the shoulder block 13 is formed at a portion where the shoulder lug groove 43 for partitioning the shoulder block 13 and the main groove 32 in the outer peripheral direction intersect, that is, the outer circumference in the shoulder block 13. It is formed in a portion where the opening 43a of the shoulder lug groove 43 with respect to the directional main groove 32 is located.

Of the chamfers 16 formed as described above, the chamfer 16 of the intermediate block 12 is formed only in one of the two intermediate blocks 12 partitioned by one intermediate lug groove 42. Similarly, the chamfer 16 of the shoulder block 13 is formed only on one of the two shoulder blocks 13 partitioned by one shoulder lug groove 43. In other words, the chamfer 16 of the intermediate block 12 is formed only on one of the groove walls facing each other forming the opening 42b of the intermediate lug groove 42, and the chamfer 16 of the shoulder block 13 is a shoulder. Of the opposing groove walls forming the opening 43a of the lug groove 43, only one of the groove walls is formed.

The pneumatic tire 1 according to the present embodiment is used as a heavy load pneumatic tire. When the pneumatic tire 1 is mounted on the vehicle, it is mounted on the vehicle in an inflated state by assembling the rim on the rim wheel. The pneumatic tire 1 in a state of being rim-assembled on a rim wheel is used by being mounted on a large vehicle such as a truck or a bus.

When a vehicle equipped with the pneumatic tire 1 travels, the pneumatic tire 1 rotates while the tread tread 3 located below the tread tread 3 is in contact with the road surface. When traveling on a dry road surface with a vehicle equipped with pneumatic tires 1, the driving force and braking force are transmitted to the road surface and turning force is generated mainly by the frictional force between the tread tread surface 3 and the road surface. It runs by letting it run. Further, when traveling on a wet road surface, water between the tread tread surface 3 and the road surface enters the circumferential main groove 30, the lug groove 40, etc., and the water between the tread tread surface 3 and the road surface is formed in these grooves. Run while draining. This makes it easier for the tread tread 3 to come into contact with the road surface, and the frictional force between the tread tread 3 and the road surface allows the vehicle to travel.

Further, when traveling on a snowy road surface, the pneumatic tire 1 compacts the snow on the road surface with the tread tread surface 3, and the snow on the road surface enters the circumferential main groove 30 and the lug groove 40, whereby these snows are formed. Will be compacted in the groove. In this state, the shearing force acts on the snow in the groove due to the driving force and the braking force acting on the pneumatic tire 1 and the force acting in the tire width direction due to the turning of the vehicle. A so-called snow column shear force is generated between the pneumatic tire 1 and the snow. When traveling on a snowy road surface, the shearing force of the snow column generates resistance between the pneumatic tire 1 and the road surface, so that driving force and braking force can be transmitted to the road surface, and the vehicle is on the snowy road surface. It will be possible to drive in.

Further, when traveling on a snowy road surface or an ice road surface, the edge effect of the circumferential main groove 30, the lug groove 40, and the sipe 60 is also used. That is, when traveling on a snowy road surface or an ice road surface, the edge of the circumferential main groove 30, the edge of the lug groove 40, and the edge of the sipe 60 are caught on the snow surface or the ice surface, and the vehicle travels using the resistance. Further, when traveling on an ice road surface, the water on the surface of the ice road surface is absorbed by the sipe 60 to remove the water film between the ice road surface and the tread tread surface 3, so that the ice road surface and the tread tread surface 3 come into contact with each other. It becomes easier to do. As a result, the tread tread 3 has a large resistance to the road surface on ice due to the frictional force and the edge effect, and the running performance of the vehicle equipped with the pneumatic tire 1 can be ensured.

As described above, when traveling on a snowy road surface or an ice road surface, grooves such as the circumferential main groove 30 and the lug groove 40 and the sipe 60 are important, but the performance when traveling on the snowy road surface and the ice road surface. When the groove depth is increased with an emphasis on the performance on ice and snow, the rigidity of the block 10 tends to decrease. When the rigidity of the block 10 is lowered, the block 10 is likely to be worn, and in particular, the wear is likely to be large in a portion having low rigidity, so that uneven wear is likely to occur.

On the other hand, in the pneumatic tire 1 according to the present embodiment, the groove wall bending portion 47 is formed in each of the groove walls 46 of the central lug groove 41 and the intermediate lug groove 42. Therefore, while ensuring the groove depths of the central lug groove 41 and the intermediate lug groove 42, the rigidity of the central block 11 partitioned by the central lug groove 41 and the rigidity of the intermediate block 12 partitioned by the intermediate lug groove 42 are increased. Can be secured. As a result, the rigidity of the vicinity of both ends of the block 10 in the tire circumferential direction is lowered, so that the portion of the tread tread 3 of the block 10 on the kick-out side during rotation of the pneumatic tire 1 is significantly worn. It is possible to suppress heel and toe wear.

Further, in the groove wall bent portion 47, the distance from the tread tread 3 to the groove wall bent portion 47 is larger than that of the groove wall bent portion 47 formed in the groove wall 46 of the intermediate lug groove 42, in the groove wall of the central lug groove 41. The groove wall bent portion 47 formed in 46 is larger. Therefore, the central lug groove 41 has a larger groove volume than the intermediate lug groove 42. In a large vehicle such as a truck or a bus, the ground contact area when the vehicle is empty is significantly smaller than the ground contact area when the cargo is fully loaded, so that the traction performance on the snowy road surface when the vehicle is empty tends to deteriorate. Since the groove volume of the central lug groove 41 formed in the central block row 21 can be secured, which is easy to touch down with a relatively large load even when the vehicle is empty, the snow column shear force when the vehicle is empty can be secured. As a result, traction performance on a snowy road surface can be ensured regardless of the cargo loading state. As a result, both ice and snow performance and uneven wear resistance can be achieved.

Further, since the central lug groove 41 and the intermediate lug groove 42 have the same groove depth, the central block 11 partitioned by the central lug groove 41 and the intermediate block 12 partitioned by the intermediate lug groove 42 It is possible to prevent the difference in rigidity from becoming too large. As a result, due to the difference in rigidity between the central block 11 and the intermediate block 12, the way of wear changes between the blocks 10, and it is possible to suppress the occurrence of uneven wear. As a result, the uneven wear resistance can be improved more reliably.

Further, the central lug groove 41 and the intermediate lug groove 42 have distances DBc and DBm from the tread tread 3 to the groove wall bending portion 47 within a range of 65% or more and 90% or less of the groove depths Dc and Dm. , It is possible to suppress heel and toe wear while ensuring traction performance on snowy roads more reliably. That is, when the distances DBc and DBm of the groove wall bending portion 47 of the central lug groove 41 and the intermediate lug groove 42 from the tread tread 3 are less than 65% of the groove depths Dc and Dm, the groove wall bending portion 47 May get too close to the tread tread 3. In this case, the groove volume of the central lug groove 41 and the intermediate lug groove 42 may become too small to secure the snow column shearing force, and it may be difficult to secure the traction performance on the snowy road surface. Further, when the distances DBc and DBm of the groove wall bent portion 47 of the central lug groove 41 and the intermediate lug groove 42 from the tread tread 3 exceed 90% of the groove depths Dc and Dm, the groove wall bent portion 47 There is a risk that the tread tread 3 will be too far away. In this case, it may be difficult to secure the rigidity of the central block 11 partitioned by the central lug groove 41 and the intermediate block 12 partitioned by the intermediate lug groove 42, and it may be difficult to suppress heel and toe wear.

On the other hand, the distances DBc and DBm of the groove wall bent portion 47 of the central lug groove 41 and the intermediate lug groove 42 from the tread tread 3 are within the range of 65% or more and 90% or less of the groove depths Dc and Dm. In this case, the rigidity of the central block 11 and the intermediate block 12 can be ensured while ensuring the groove volume of the central lug groove 41 and the intermediate lug groove 42. As a result, it is possible to suppress heel and toe wear while ensuring traction performance on a snowy road surface more reliably. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

Further, since the groove depths Dc and Dm of the central lug groove 41 and the intermediate lug groove 42 are within the range of 65% or more and 85% or less of the groove depth of the circumferential main groove 30, respectively, the central lug groove 41 It is possible to secure the rigidity of the central block 11 and the intermediate block 12 while ensuring the snow column shearing force in the intermediate lug groove 42 for a relatively long period of time. That is, when the groove depths Dc and Dm of the central lug groove 41 and the intermediate lug groove 42 are less than 65% of the groove depth of the circumferential main groove 30, the groove depths Dc and Dm are too shallow and the tread. When the wear of the tread surface 3 progresses, there is a possibility that the shearing force of the snow column tends to decrease. In this case, the traction performance on the snowy road surface may deteriorate at an early stage after the start of use of the pneumatic tire 1. If the groove depths Dc and Dm of the central lug groove 41 and the intermediate lug groove 42 exceed 85% of the groove depth of the circumferential main groove 30, the groove depths Dc and Dm are too deep and the central block. There is a risk that it will be difficult to secure the rigidity of 11 and the intermediate block 12. In this case, it may be difficult to suppress heel and toe wear.

On the other hand, when the groove depths Dc and Dm of the central lug groove 41 and the intermediate lug groove 42 are within the range of 65% or more and 85% or less of the groove depth of the circumferential main groove 30, the central lug groove 41 It is possible to secure the rigidity of the central block 11 and the intermediate block 12 while ensuring the snow column shearing force in the intermediate lug groove 42 for a relatively long period of time. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

Further, since the width Wc in the tire width direction of the central block 11 is within the range of 15% or more and 30% or less of the tread deployment width TDW, the performance on ice and snow can be improved regardless of the load state of the cargo. .. That is, when the width Wc of the central block 11 in the tire width direction is less than 15% of the tread deployment width TDW, the width Wc of the central block 11 which is easy to touch with a relatively large load even when the vehicle is empty is too narrow. There is a risk that the ground contact area when the vehicle is empty will be too small. In this case, it may be difficult to secure the traction performance on the snowy road surface when the vehicle is empty. When the width Wc of the central block 11 in the tire width direction exceeds 30% of the tread expansion width TDW, a portion other than the central block 11 such as the groove width of the circumferential main groove 30 and the width Wm of the intermediate block 12 There is a risk that it will be difficult to secure the width in the tire width direction. In this case, it may be difficult to secure the snow column shearing force in the circumferential main groove 30 and the intermediate lug groove 42, and it may be difficult to secure steering stability and traction performance on a snowy road surface other than when the vehicle is empty. ..

On the other hand, when the width Wc of the central block 11 in the tire width direction is within the range of 15% or more and 30% or less of the tread expansion width TDW, the width Wc of the central block 11 is secured on the snow when the vehicle is empty. While ensuring traction performance on the road surface, it is possible to secure steering stability and traction performance on snowy road surfaces other than when the vehicle is empty. As a result, the performance on ice and snow can be improved more reliably.

Further, since the central lug groove 41 has two or more bent portions 45 in the extending direction, the number of the central lug grooves 41 with respect to the central block 11 and the volume of the central lug groove 41 with respect to the volume of the central block 11 You can increase the ratio. This makes it possible to more reliably secure the traction performance on the snowy road surface. As a result, the performance on ice and snow can be improved more reliably.

Further, since the pitch Pc in the tire peripheral direction of the central lug groove 41 is within the range of 1% or more and 3% or less of the tire peripheral length, the empty vehicle can be more reliably suppressed from the heel and toe wear of the central block 11. It is possible to secure the traction performance on the snowy road surface at the time. That is, when the pitch Pc of the central lug groove 41 in the tire peripheral direction is less than 1% of the tire peripheral length, the pitch Pc of the central lug groove 41 is too small, so that the central block 11 is partitioned by the central lug groove 41. It may be difficult to secure rigidity. In this case, it may be difficult to suppress the heel and toe wear of the central block 11. Further, when the pitch Pc of the central lug groove 41 in the tire peripheral direction exceeds 3% of the tire peripheral length, the number of the central lug grooves 41 may be too small. In this case, it may be difficult to secure the traction performance on the snowy road surface when the vehicle is empty.

On the other hand, when the pitch Pc of the central lug groove 41 in the tire peripheral direction is within the range of 1% or more and 3% or less of the tire peripheral length, the rigidity of the central block 11 is ensured and the heel of the central block 11 is pressed. While suppressing toe wear more reliably, it is possible to more reliably secure traction performance on a snowy road surface when the vehicle is empty. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

Further, since the ground contact area of the central block 11 is within the range of 1.8 times or more and 2.3 times or less of the ground contact area of the intermediate block 12, the traction performance on the snowy road surface when the vehicle is empty can be more reliably performed. Can be secured. That is, if the ground contact area of the central block 11 is less than 1.8 times the ground contact area of the intermediate block 12, the number of sipes 60 that can be arranged in the central block 11 may decrease. In this case, it becomes difficult to secure the edge amount of the central block 11 which is easy to touch the ground with a relatively large load even when the vehicle is empty, so that it may be difficult to secure the traction performance on the snowy road surface when the vehicle is empty. When the ground contact area of the central block 11 exceeds 2.3 times the ground contact area of the intermediate block 12, the edge of the portion of the central block 11 partitioned by the circumferential main groove 30 and the central lug groove 41. However, there is a risk that it will be too small with respect to the ground contact area of the central block 11. Also in this case, since it is difficult to secure the edge amount of the central block 11, there is a possibility that it is difficult to secure the traction performance on the snowy road surface when the vehicle is empty.

On the other hand, when the ground contact area of the central block 11 is within the range of 1.8 times or more and 2.3 times or less of the ground contact area of the intermediate block 12, the traction performance on the snowy road surface when the vehicle is empty is determined. It can be secured more reliably. As a result, the performance on ice and snow can be improved more reliably.

Further, since the central block 11 is divided into two in the tire width direction by the central fine groove 51 extending in the tire circumferential direction, the edge of the central block row 21 can be increased while suppressing the decrease in the rigidity of the central block 11. .. As a result, it is possible to secure steering stability on a snowy road surface while suppressing heel and toe wear of the central block 11. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

Further, the central lug groove 41 and the intermediate lug groove 42 that open with respect to the same inner peripheral direction main groove 31 have an opening position with respect to the inner peripheral direction main groove 31 of 0.5% or more and 1.0% of the tire peripheral length. Since the central lug groove 41 and the intermediate lug groove 42 are arranged so as to be offset in the tire circumferential direction within the following range, the central lug groove 41 and the intermediate lug groove 42 can be distributed and arranged in the tire circumferential direction. This makes it possible to more reliably secure the traction performance on the snowy road surface. As a result, the performance on ice and snow can be improved more reliably.

Further, since the groove depth of the outer circumferential main groove 32 is within the range of 155% or more and 185% or less with respect to the groove width, the heel and toe can be more reliably secured on the snowy road surface. Wear can be suppressed. That is, when the groove depth of the outer peripheral direction main groove 32 is less than 155% with respect to the groove width, the groove volume of the outer peripheral direction main groove 32 becomes too small and it becomes difficult to secure the snow column shearing force. There is a risk that it may be difficult to ensure steering stability on snowy roads. Further, when the groove depth of the outer peripheral direction main groove 32 exceeds 185% with respect to the groove width, the groove depth of the outer peripheral direction main groove 32 is too deep, so that the outer peripheral direction main groove 32 is used for partitioning. It may be difficult to secure the rigidity of the block 10, and it may be difficult to suppress heel and toe wear.

On the other hand, when the groove depth of the outer peripheral direction main groove 32 is within the range of 155% or more and 185% or less with respect to the groove width, the outer side is secured while ensuring the groove volume of the outer peripheral direction main groove 32. The rigidity of the block 10 partitioned by the circumferential main groove 32 can be ensured. As a result, it is possible to suppress heel and toe wear while ensuring steering stability on a snowy road surface more reliably. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

Further, the intermediate lug groove 42 and the shoulder lug groove 43 that open with respect to the same outer peripheral main groove 32 have an opening position with respect to the outer peripheral main groove 32 of 0.5% or more and 1.0% of the tire peripheral length. Since the intermediate lug grooves 42 and the shoulder lug grooves 43 are arranged so as to be offset in the tire circumferential direction within the following range, the intermediate lug grooves 42 and the shoulder lug grooves 43 can be distributed and arranged in the tire circumferential direction. This makes it possible to more reliably secure the traction performance on the snowy road surface. As a result, the performance on ice and snow can be improved more reliably.

Further, since the shoulder block row 26 is divided into two in the tire width direction by the shoulder narrow groove 52 extending in the tire circumferential direction, the edge of the shoulder block row 26 can be increased while suppressing the decrease in the rigidity of the shoulder block 13. can. As a result, it is possible to secure steering stability on a snowy road surface while suppressing heel and toe wear of the shoulder block 13. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

Further, since the groove depth of the shoulder narrow groove 52 is within the range of 55% or more and 65% or less with respect to the groove depth of the main groove 32 in the outer peripheral direction, the snow removal performance of the shoulder narrow groove 52 is ensured. , The rigidity of the shoulder block 13 can be ensured. That is, when the groove depth of the shoulder narrow groove 52 is less than 55% of the groove depth of the main groove 32 in the outer peripheral direction, the groove depth of the shoulder narrow groove 52 is too shallow, so that the shoulder is shouldered when traveling on a snowy road surface. Snow is likely to be clogged in the narrow groove 52, and it may be difficult to secure the snow removal performance. Further, when the groove depth of the shoulder narrow groove 52 exceeds 65% of the groove depth of the main groove 32 in the outer peripheral direction, the groove depth of the shoulder narrow groove 52 is too deep, so that the rigidity of the shoulder block 13 is ensured. It may be difficult to do. In this case, it may be difficult to suppress heel and toe wear.

On the other hand, when the groove depth of the shoulder narrow groove 52 is within the range of 55% or more and 65% or less of the groove depth of the main groove 32 in the outer peripheral direction, the snow removal performance of the shoulder narrow groove 52 is ensured. At the same time, the rigidity of the shoulder block 13 can be ensured. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

Further, since the groove depth of the shoulder lug groove 43 is within the range of 75% or more and 85% or less with respect to the groove depth of the central lug groove 41, the shoulder block 13 ensures traction performance on a snowy road surface. Heal and toe wear can be suppressed more reliably. That is, when the groove depth of the shoulder lug groove 43 is less than 75% of the groove depth of the central lug groove 41, the groove depth of the shoulder lug groove 43 is too shallow, so that the shoulder lug groove 43 has a groove depth. It may be difficult to secure the snow column shear force. In this case, it may be difficult to secure traction performance on a snowy road surface. Further, when the groove depth of the shoulder lug groove 43 exceeds 85% with respect to the groove depth of the central lug groove 41, the groove depth of the shoulder lug groove 43 is too deep, and the shoulder lug groove 43 is used for partitioning. It may be difficult to secure the rigidity of the shoulder block 13. In this case, it may be difficult to suppress heel and toe wear.

On the other hand, when the groove depth of the shoulder lug groove 43 is within the range of 75% or more and 85% or less with respect to the groove depth of the central lug groove 41, the snow column shear force in the shoulder lug groove 43 is applied. While ensuring the traction performance on the snowy road surface, the heel and toe wear of the shoulder block 13 can be suppressed more reliably. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

Further, since the intermediate block 12 is arranged offset in the tire circumferential direction with respect to the central block 11 and the shoulder block 13, a plurality of blocks 10 adjacent to each other in the tire width direction when the pneumatic tire 1 rotates. Can be prevented from being separated from the road surface at the same time, and a plurality of blocks 10 adjacent to each other in the tire width direction can be prevented from being separated from the road surface at different timings. As a result, it is possible to suppress large wear of the kick-out side portion of each block 10, and it is possible to more reliably suppress heel and toe wear. As a result, the uneven wear resistance can be improved more reliably.

Further, since the chamfer 16 is formed in the intermediate block 12 and the shoulder block 13 at the intersection of the outer circumferential main groove 32 and the lug groove 40, the stress concentration acting on the intermediate block 12 and the shoulder block 13 is concentrated. Can be alleviated, and uneven wear can be suppressed more reliably. As a result, the uneven wear resistance can be improved more reliably.

Further, since the open sipe 61 formed in the central block 11 and the intermediate block 12 is formed as a three-dimensional sipe 60, the block 10 is formed by forming the sipe 60 while ensuring the performance on ice and snow by the sipe 60. It is possible to suppress a decrease in the rigidity of the. That is, since the three-dimensional shape sipe 60 has a stronger meshing force between the facing sipe wall surfaces than the two-dimensional shape sipe 60, the three-dimensional shape sipe 60 suppresses a decrease in the rigidity of the block 10 and is biased. Performance on ice and snow can be ensured by the edge effect while suppressing wear. As a result, it is possible to more reliably achieve both ice and snow performance and uneven wear resistance.

[Modification example]
In the pneumatic tire 1 according to the above-described embodiment, the central lug groove 41 and the intermediate lug groove 42 have the same groove depth, but the central lug groove 41 and the intermediate lug groove 42 do not. , The groove depth may be different. The central lug groove 41 and the intermediate lug groove 42 may have a deeper groove depth in the intermediate lug groove 42 than in the central lug groove 41, for example. The groove depth of the intermediate lug groove 42 is deeper than that of the central lug groove 41, that is, the groove depth of the central lug groove 41 is made shallower than the groove depth of the intermediate lug groove 42. The rigidity of the central block 11 partitioned by 41 can be improved more reliably. As a result, it is possible to more reliably suppress heel and toe wear of the central block 11 which tends to touch the ground with a large load regardless of the load state of the cargo. As a result, the uneven wear resistance can be improved more reliably.

Further, in the pneumatic tire 1 according to the above-described embodiment, the groove wall bending portions 47 formed in the groove wall 46 of the central lug groove 41 and the intermediate lug groove 42 are formed on both sides of the groove wall bending portion 47 in the groove wall 46. Although the groove wall bending portion 47 is bent in a direction in which the relative angle of the located portion is less than 180 °, the groove wall bending portion 47 may be bent in any other form.

FIG. 7 is a modification of the pneumatic tire 1 according to the embodiment, and is an explanatory view when the relative angle between the groove walls 46 on both sides of the groove wall bending portion 47 bends more than 180 °. The groove wall bent portion 47 formed in the central lug groove 41 and the intermediate lug groove 42 is, for example, as shown in FIG. 7, at a position on the tread tread 3 side of the groove wall bent portion 47, from the tread tread 3 to the groove wall. The groove width becomes smaller toward the bent portion 47, and the groove width may be bent so as to be substantially constant at the position on the groove bottom 48 side of the groove wall bent portion 47. In other words, in the groove wall bent portion 47 of the central lug groove 41 and the intermediate lug groove 42, the groove walls 46 facing each other are formed in a tapered shape on the tread tread 3 side of the groove wall bent portion 47, and the groove wall 46 is formed. On the groove bottom 48 side of the groove wall bent portion 47, the groove walls 46 facing each other may be bent so as to be formed in parallel. That is, the groove wall bending portion 47 of the central lug groove 41 and the intermediate lug groove 42 has a tread tread surface from the groove wall bending portion 47 in the groove wall 46 rather than the portion on the groove bottom 48 side of the groove wall bending portion 47 in the groove wall 46. Even if the portion on the 3rd side is bent in a direction in which the relative angle of the portions located on both sides of the groove wall bending portion 47 in the groove wall 46 exceeds 180 ° so that the inclination angle of the groove wall 46 is larger. good.

Further, in the pneumatic tire 1 according to the above-described embodiment, the groove wall bending portions 47 formed in the groove wall 46 of the central lug groove 41 and the intermediate lug groove 42 are formed in both of the opposite groove walls 46. The groove wall bending portion 47 may not be formed on both groove walls 46. FIG. 8 is a modification of the pneumatic tire 1 according to the embodiment, and is an explanatory view when the groove wall bending portion 47 is formed only on one groove wall 46. The groove wall bending portion 47 formed in the central lug groove 41 and the intermediate lug groove 42 is formed only in one groove wall 46 of the facing groove walls 46, and the other groove is formed, for example, as shown in FIG. The groove wall bending portion 47 may not be formed on the wall 46. It is sufficient that one or more groove wall bending portions 47 formed in the groove wall 46 of the central lug groove 41 and the intermediate lug groove 42 are provided in each of the facing groove walls 46.

Further, a plurality of groove wall bending portions 47 formed in the groove wall 46 of the central lug groove 41 and the intermediate lug groove 42 may be formed in one groove wall 46. FIG. 9 is a modification of the pneumatic tire 1 according to the embodiment, and is an explanatory view when a plurality of groove wall bending portions 47 are formed on one groove wall 46. As shown in FIG. 9, for example, two groove wall bending portions 47 of the central lug groove 41 and the intermediate lug groove 42 may be formed on one groove wall 46. In this way, when a plurality of groove wall bending portions 47 are formed on one groove wall 46, the distance in the groove depth direction from the tread tread tread 3 to the groove wall bending portion 47a closest to the tread tread 3 is intermediate. The groove wall bending portion 47a formed on the groove wall 46 of the central lug groove 41 may be larger than the groove wall bending portion 47a formed on the groove wall 46 of the lug groove 42. That is, when a plurality of groove wall bending portions 47 are formed on one groove wall 46, the distance in the groove depth direction from the tread tread surface 3 to the groove wall bending portion 47a closest to the tread tread surface 3 in the intermediate lug groove 42. It is sufficient that the distance DBc in the groove depth direction from the tread tread 3 to the groove wall bending portion 47a closest to the tread tread 3 in the central lug groove 41 is larger than the DBm.

When a plurality of groove wall bending portions 47 are formed in one groove wall 46 of the central lug groove 41 or the intermediate lug groove 42 in this way, the tread tread tread 3 is closest to the tread tread 3 in the groove depth direction. It is preferable that the distance to the groove wall bent portion 47a is within the range of 65% or more and 90% or less of the groove depth.

Further, when a plurality of groove wall bending portions 47 are formed in one groove wall 46 of the central lug groove 41 or the intermediate lug groove 42, the grooves of the plurality of groove wall bending portions 47 formed in the same groove wall 46 are formed. The positions in the depth direction may be the same. FIG. 10 is a modification of the pneumatic tire 1 according to the embodiment, and is an explanatory view when a plurality of groove wall bending portions 47 are formed on one groove wall 46. In the central lug groove 41 and the intermediate lug groove 42, for example, as shown in FIG. 10, two groove wall bending portions 47 are formed on one groove wall 46, and the groove depth direction between the two groove wall bending portions 47 is formed. By having the same position in the groove wall 46, the portion between the groove wall bending portions 47 in the groove wall 46 may be formed in a rug shape in which the portion between the groove wall bending portions 47 is formed in parallel with the tread tread surface 3.

FIG. 11 is a modification of the pneumatic tire 1 according to the embodiment, and is an explanatory view when a plurality of groove wall bending portions 47 are formed on one groove wall 46. Further, when a plurality of groove wall bending portions 47 are formed in one groove wall 46 of the central lug groove 41 or the intermediate lug groove 42, the groove wall bending portions 47 having different bending directions are formed in one groove wall 46. Three or more may be formed. In this case, for example, as shown in FIG. 11, a portion in which the opposing groove walls 46 are formed in a tapered shape by three or more groove wall bending portions 47 formed in one groove wall 46, and a hinamatsuri shape. It may be formed in one groove wall 46 in combination with the portion formed in.

FIG. 12 is a modification of the pneumatic tire 1 according to the embodiment, and is an explanatory view when a protrusion 49 is formed on the groove bottom 48. Further, as shown in FIG. 12, the central lug groove 41 and the intermediate lug groove 42 may have a protrusion 49 protruding from the groove bottom 48 in the direction of the tread tread 3 at the groove bottom 48. The shape of the groove bottom 48 of the central lug groove 41 and the intermediate lug groove 42 does not matter as long as the groove wall bent portion 47 is formed on the groove wall 46.

Further, in the central lug groove 41 and the intermediate lug groove 42, the groove wall bent portions 47 formed in the groove wall 46 may be formed in different forms from each other. If the central lug groove 41 and the intermediate lug groove 42 have one or more groove wall bending portions 47 on the facing groove walls 46, the number of groove wall bending portions 47, the bending form, and the shape of the groove bottom 48. Does not matter.

Further, in the above-described embodiment, the groove wall bent portion 47 is formed in the groove wall 46 of the central lug groove 41 and the intermediate lug groove 42, but the shoulder lug groove 43 and the circumferential main groove 30 have the same embodiment. A groove wall bent portion may be formed.

Further, in the above-described embodiment, the extending direction bending portions 45 are formed at two locations of one central lug groove 41, but the extending direction bending portions 45 are formed at three locations with respect to one central lug groove 41. It may be formed as described above. It is preferable that the number of the extending direction bending portions 45 formed in one central lug groove 41 is appropriately set according to the pitch Pc or the like of the central lug groove 41.

Further, in the above-described embodiment, the central block 11 is divided into two in the tire width direction by the central narrow groove 51, but the central block 11 may be divided into three or more. That is, in the central fine groove 51, two or more central fine grooves 51 may be formed between the two inner peripheral main grooves 31. Similarly, two or more shoulder narrow grooves 52 may be formed on the outer side of the outer peripheral direction main groove 32 in the tire width direction, and the shoulder block row 26 may be formed in the tire width direction by the two or more shoulder narrow grooves 52. It may be divided into three or more divisions. The central fine groove 51 is preferably set as appropriate according to the width Wc of the central block 11 in the tire width direction, the ratio of the width Wc of the central block 11 to the tread development width TDW, and the like. Similarly, it is preferable that the shoulder narrow groove 52 is appropriately set according to the width of the shoulder block row 26 in the tire width direction, the ratio of the width of the shoulder block row 26 to the tread expansion width TDW, and the like.

Further, in the above-described embodiment, the chamfer 16 is formed in the portion of the intermediate block 12 and the shoulder block 13 on the outer peripheral direction main groove 32 side, but the chamfer 16 is the inner peripheral direction main groove 31 in the intermediate block 12. It may be formed at a portion where the intermediate lug groove 42 and the intermediate lug groove 42 intersect. Further, a chamfer 16 having the same shape may be formed at a portion of the central block 11 where the main groove 31 in the inner peripheral direction and the central lug groove 41 intersect.

Further, two open sipes 61 and two closed sipes 62 are formed in the divided central block 11a and the intermediate block 12 of the central block 11, and four closed sipes 62 are formed in the shoulder block 13. However, the sipes 60 formed in each block 10 may be formed in a number or configuration other than this. It is preferable that the sipe 60 formed in the block 10 is appropriately set according to the position and size of the block 10 forming the sipe 60.

Further, in the above-described embodiment, four circumferential main grooves 30 are formed, but the circumferential main groove 30 may be other than four. The circumferential main groove 30 includes a central lug groove 41 arranged between at least two inner peripheral main grooves 31, an inner peripheral main groove 31 adjacent to each other in the tire width direction, and an outer peripheral main groove 32. Any number of lug grooves 42 can be provided as long as the intermediate lug grooves 42 arranged between the lugs and the lug grooves 42 can be provided.

[Example]
13A to 13E are charts showing the results of performance evaluation tests of pneumatic tires. Hereinafter, with respect to the above-mentioned pneumatic tire 1, the performance of the conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and the pneumatic tire of the comparative example compared with the pneumatic tire 1 according to the present invention. The evaluation test of. In the performance evaluation test, traction performance on ice and snow road surfaces, steering stability on ice and snow, and uneven wear resistance, which is the performance regarding the difficulty of uneven wear, were tested.

In the performance evaluation test, the tire 1 with a tire nominal size of 275 / 80R22.5 specified by JATTA is rim-assembled on the rim wheel of the specified rim specified by JATTA, and the air pressure is the maximum air pressure specified by JATTA. It was adjusted to 2D4 and mounted on a 2-D4 test vehicle (truck) for a test run.

As for the evaluation method of each test item, regarding the performance on ice and snow, the feeling evaluation by the test driver is performed when the test vehicle runs on the test course having the ice road surface and the snow road surface, and the feeling evaluation is described later. The example was evaluated by expressing it as an exponent as 100. The larger the value, the higher the steering stability on ice and snow roads, and the better the performance on ice and snow.

Regarding the uneven wear resistance, the amount of wear of heel and toe after traveling 20,000 km in the test vehicle, specifically, the difference in the amount of wear between the kicking side and the stepping side of each block 10 is measured. The difference in the measured amount of wear is indicated by an index of 100 in the conventional example described later. The larger this value is, the smaller the difference in the amount of wear between the kicking side and the stepping side of the block 10, that is, the heel & toe wear is small, and the uneven wear resistance is excellent.

The performance evaluation test compares the conventional pneumatic tire, which is an example of the conventional pneumatic tire, the pneumatic tires 1 according to the present invention, Examples 1 to 41, and the pneumatic tire 1 according to the present invention. Forty-three types of pneumatic tires with the comparative example of pneumatic tires were performed. Of these, in the conventional pneumatic tire, the groove wall bending portion 47 is not formed in the central lug groove 41 and the intermediate lug groove 42.

In FIGS. 13A to 13E, in the "normal arrangement" in the "arrangement form of the divided central blocks", the divided central blocks 11a located on both sides of the central narrow groove 51 in the tire width direction are offset in the tire circumferential direction. However, it shows an arrangement state in which the positions of the divided central blocks 11a in the tire circumferential direction are substantially the same. Further, in FIGS. 13A to 13E, "-" in the "arrangement form of the shoulder block" indicates a state in which the shoulder narrow groove 52 is not formed on the outer side of the main groove 32 in the outer peripheral direction in the tire width direction. Further, in FIGS. 13A to 13E, in the "normal arrangement" in the "arrangement form of the intermediate block, the central block and the shoulder block", the intermediate block 12 is offset in the tire circumferential direction with respect to the central block 11 and the shoulder block 13. It shows an arrangement state in which the positions of the intermediate block 12, the central block 11 and the shoulder block 13 in the tire circumferential direction are substantially the same.

Further, in the pneumatic tire of the comparative example, although the groove wall bending portion 47 is formed in each groove wall 46 of the central lug groove 41 and the intermediate lug groove 42, the tread tread surface 3 to the groove wall bending portion 47. The distance is larger in the intermediate lug groove 42 than in the central lug groove 41.

On the other hand, in Examples 1 to 41, which are examples of the pneumatic tire 1 according to the present invention, the groove wall bending portion 47 is formed in each groove wall 46 of the central lug groove 41 and the intermediate lug groove 42. The distance from the tread tread 3 to the groove wall bent portion 47 is larger in the central lug groove 41 than in the intermediate lug groove 42. Further, the pneumatic tire 1 according to the first to 41st embodiments has a distance DBc, DBm, and a circumference from the tread tread 3 to the groove wall bent portion 47 with respect to the groove depths Dc and Dm of the central lug groove 41 and the intermediate lug groove 42. The width Wc of the central block 11 in the tire width direction and the extension of the central lug groove 41 with respect to the groove depths Dc and Dm of the central lug groove 41 and the intermediate lug groove 42 with respect to the groove depth of the directional main groove 30 and the tread expansion width TDW. Number of tire treads 45, pitch Pc of central lug groove 41 with respect to tire circumference length, area of central block 11 with respect to area of intermediate block 12, number of divisions of central block 11, arrangement form of division center block 11a, main groove in circumferential direction The groove depth with respect to the groove width of 30, the arrangement form of the shoulder block 13, the groove depth of the shoulder narrow groove 52 with respect to the groove depth of the circumferential main groove 30, the groove depth of the central lug groove 41 with respect to the groove depth Dc of the shoulder lug groove 43. The groove depth, the intermediate block 12, the arrangement form of the central block 11 and the shoulder block 13, and the shape of the open sipe 61 are different from each other.

As a result of performing a performance evaluation test using these pneumatic tires 1, as shown in FIGS. 13A to 13E, the pneumatic tires 1 according to Examples 1 to 41 are ice and snow as compared with the conventional example and the comparative example. It was found that both high performance and uneven wear resistance can be improved. That is, the pneumatic tire 1 according to the first to 41st embodiments can have both performance on ice and snow and uneven wear resistance.

1 Pneumatic tire 2 Tread part 3 Tread tread 10 block 11 Central block 11a Divided central block 12 Intermediate block 13 Shoulder block 16 Chamfering 21 Central block row 22 Divided block row 25 Intermediate block row 26 Shoulder block row 27 Block row 30 Circumferential main Groove 31 Inner circumferential main groove 32 Outer circumferential main groove 40 Lag groove 41 Central lug groove 42 Intermediate lug groove 43 Shoulder lug groove 45 Extended direction bent part 46 Groove wall 47 Groove wall bent part 50 Circumferential fine groove 51 Central thin Groove 52 Shoulder tread 60 Sipe 61 Open sipe 62 Closed sipe

Claims (19)

Of the plurality of circumferential main grooves extending in the tire circumferential direction, two inner circumferential main grooves which are the circumferential main grooves arranged on both sides of the tire equatorial plane in the tire width direction with the tire equatorial plane in between. When,
The outer circumferential main groove, which is the circumferential main groove, arranged on the outer side of each of the two inner circumferential main grooves in the tire width direction,
Of the plurality of lug grooves extending in the tire width direction, a central lug groove arranged between the two inner circumferential main grooves and a central lug groove.
Of the plurality of lug grooves extending in the tire width direction, an intermediate lug groove disposed between the inner peripheral direction main groove and the outer peripheral direction main groove adjacent to each other in the tire width direction,
A central block partitioned by the two inner circumferential main grooves and the central lug groove,
An intermediate block partitioned by the inner circumferential main groove, the outer circumferential main groove, and the intermediate lug groove,
Equipped with
The central lug groove and the intermediate lug groove each have one or more groove wall bent portions, which are portions where the angle in the groove width direction with respect to the depth direction of the lug groove changes.
In the groove wall bending portion, the distance from the tread tread in the groove depth direction of the lug groove to the groove wall bending portion closest to the tread tread is formed in the groove wall of the intermediate lug groove. A pneumatic tire characterized in that the bent portion of the groove wall formed on the groove wall of the central lug groove is larger than the bent portion. The pneumatic tire according to claim 1, wherein the central lug groove and the intermediate lug groove have the same groove depth. The pneumatic tire according to claim 1, wherein the central lug groove and the intermediate lug groove have a deeper groove depth in the intermediate lug groove than in the central lug groove. The distance between the central lug groove and the intermediate lug groove in the groove depth direction from the tread tread to the groove wall bending portion closest to the tread tread is in the range of 65% or more and 90% or less of the groove depth. The pneumatic tire according to any one of claims 1 to 3. The one according to any one of claims 1 to 4, wherein the central lug groove and the intermediate lug groove are each in the range of 65% or more and 85% or less of the groove depth of the circumferential main groove. Pneumatic tires. The pneumatic tire according to any one of claims 1 to 5, wherein the central block has a width in the tire width direction within a range of 15% or more and 30% or less of the tread development width. The air according to any one of claims 1 to 6, wherein the central lug groove has two or more extending direction bending portions, which are portions where the angle in the tire circumferential direction with respect to the tire width direction changes. Tires with. The pneumatic tire according to any one of claims 1 to 7, wherein the central lug groove has a pitch in the tire peripheral direction within a range of 1% or more and 3% or less of the tire peripheral length. The pneumatic tire according to any one of claims 1 to 8, wherein the central block has a ground contact area within a range of 1.8 times or more and 2.3 times or less with respect to the ground contact area of the intermediate block. A central fine groove extending in the tire circumferential direction is formed between the two inner peripheral main grooves with a groove width narrower than the groove width of the lug groove.
The pneumatic tire according to any one of claims 1 to 9, wherein the central block is divided into two in the tire width direction by the central narrow groove. The central lug groove and the intermediate lug groove that open with respect to the same inner peripheral main groove have an opening position with respect to the inner peripheral main groove of 0.5% or more and 1.0% or less of the tire peripheral length. The pneumatic tire according to any one of claims 1 to 10, which is arranged so as to be offset in the tire circumferential direction within the range. The pneumatic tire according to any one of claims 1 to 11, wherein the outer circumferential main groove has a groove depth in the range of 155% or more and 185% or less with respect to the groove width. On the outer side of the outer peripheral direction main groove in the tire width direction, a shoulder having a shoulder lug groove which is the lug groove extending in the tire width direction and a shoulder block defined by the outer peripheral direction main groove and the shoulder lug groove. Block rows are arranged,
The intermediate lug groove and the shoulder lug groove that open with respect to the same outer peripheral main groove have an opening position with respect to the outer peripheral main groove of 0.5% or more and 1.0% or less of the tire peripheral length. The pneumatic tire according to any one of claims 1 to 12, which is arranged so as to be offset in the tire circumferential direction within the range. On the outer side of the outer peripheral direction main groove in the tire width direction, a shoulder narrow groove extending in the tire circumferential direction with a groove width narrower than the groove width of the lug groove is formed.
The pneumatic tire according to claim 13, wherein the shoulder block row is divided into two in the tire width direction by the shoulder narrow groove. The pneumatic tire according to claim 14, wherein the shoulder narrow groove has a groove depth in the range of 55% or more and 65% or less with respect to the groove depth of the outer peripheral direction main groove. The pneumatic tire according to any one of claims 13 to 15, wherein the shoulder lug groove has a groove depth in the range of 75% or more and 85% or less with respect to the groove depth of the central lug groove. The pneumatic tire according to any one of claims 13 to 16, wherein the intermediate block is arranged so as to be offset in the tire circumferential direction with respect to the central block and the shoulder block. 13. Pneumatic tires. At least four sipes including open sipes having both ends opened at the ends of the blocks are arranged in the central block and the intermediate block.
The pneumatic tire according to any one of claims 1 to 18, wherein the open sipe is a sipe having a three-dimensional shape that oscillates in the sipe width direction with respect to both the sipe length direction and the sipe depth direction. ..

Images