DE112019006446B4 - tire - Google Patents

Abstract

A pneumatic tire for which a direction of rotation is predetermined, the pneumatic tire comprising:a tread portion (1) extending in a tire circumferential direction and having an annular shape;a pair of sidewall portions (2) respectively arranged on both sides of the tread portion (1); anda pair of bead portions (3) each arranged on an inner side of the sidewall portions (2) in the tire radial direction,wherein the tread portion (1) has an outer surface on which a plurality of lug grooves (20, 30) extending in the tire width direction and narrow circumferential grooves (40) connecting adjacent lug grooves (20, 30) in the tire circumferential direction are formed,wherein the tread portion (1) comprises a plurality of center blocks (51) defined on a center side by the lug grooves (20, 30) and the narrow circumferential grooves (40),wherein the center blocks (51) comprise first center blocks (51A) arranged eccentrically on one side in the tire width direction with respect to a tire equator (CL), and second center blocks (51B) arranged eccentrically on another side in the tire width direction with respect to the tire equator (CL) are,wherein the first center blocks (51A) and the second center blocks (51B) are arranged alternately in the tire circumferential direction,wherein each of the first center blocks (51A) and each of the second center blocks (51B) has a front ground contact side axial edge (e1) running along the tire width direction on a front ground contact side and crossing the tire equator (CL), a rear ground contact side axial edge (e2) running along the tire width direction on a rear ground contact side and crossing the tire equator (CL), a pair of front ground contact side diagonal edges (e3, e4) running diagonally such that a block width gradually increases from both ends of the front ground contact side axial edge (e1) to the rear ground contact side, anda rear ground contact side diagonal edge (e5) extending in a region protruding from the tire equator (CL) in a different direction from one of the pair of front ground contact side diagonal edges (e3, e4) and connecting one of the pair of diagonal edges of the front ground contact side (e3, e4) and the axial edge of the rear ground contact side (e2), and wherein each of the axial edge of the front ground contact side (e1) and the axial edge of the rear ground contact side (e2) has an angle with respect to the tire width direction in a range of -10° to 10°.

Description

Technical area

The present invention relates to a pneumatic tire suitable as a heavy-duty pneumatic tire, and more particularly to a pneumatic tire capable of providing improved traction performance on snow while adequately maintaining mileage on unpaved roads.

State of the art

Heavy-duty pneumatic tires used on construction vehicles such as dump trucks must have excellent mileage (traction performance) especially on unpaved roads. Thus, a block-based tread pattern is used, including a large number of lug grooves extending in the tire width direction (see for example JP4676959B2 ).

Meanwhile, in recent years, the performance requirements for various tires have increased, and the tires described above must improve not only the mileage on unpaved roads but also the traction performance on snow.

JP H09 188 109 A discloses a pneumatic tire having a tread portion having main grooves extending from both tread ends and terminating in land portions near an equatorial line. The main grooves extend from the end positions to the connecting positions with a curvature that gradually increases along the groove extending direction, and the main grooves have arrangement configurations that extend in the range of 70 to 90 degrees until they extend from the connecting positions and then open to the tread ends. Further, along the main grooves, at certain intervals in a range corresponding to 70 to 80% of the tread width around the equatorial line, auxiliary grooves are arranged with both ends opening into the two main grooves. Moreover, in a tire-ground contact region formed under the condition of a certain air pressure and a certain load, the auxiliary grooves are arranged at transverse angles in the range of 10 to 40 degrees to the preceding contour line of the ground contact side.

JP 2012 171 606 A discloses a pneumatic tire having narrow zigzag grooves, narrow lateral grooves and narrow widthwise grooves in a tread portion, thereby forming two block rows. In the blocks, a plurality of block landing portions are arranged side by side in a polygon shape having five or more sides along a tire circumferential direction. The lateral narrow grooves are arranged within the 1/2-3/4 position range of a distance from a tire equator to a tread end, and they extend in the same direction of the respective tread ends from the tire equator side at prescribed inclination angles relative to the tire circumferential direction.

JP 2017 128 217 A discloses a pneumatic tire having a tread portion intermediate a first tread end and a second tread end. In a central region of the tread portion, a plurality of crown blocks are provided in the tire circumferential direction, the crown block having a first lateral edge extending from the vicinity of the tire equator to the first tread end side along the axial direction of the tire, and a second lateral edge extending from the both ends of the first lateral edge in the tire circumferential direction, a first crown block having a trapezoidal distal end portion having a pair of first oblique edges extending obliquely so as to gradually increase toward one side, and a second crown block having a trapezoidal distal end portion having a trapezoidal shape, a second lateral edge extending toward the side of the tire, and a second lateral edge extending diagonally from the both ends of the second lateral edge so that the block width in the axial direction of the tire gradually increases toward one side in the tire circumferential direction, and a second crown block having a trapezoidal distal end portion having a pair of second oblique edges. The first crown block and the second crown block are provided alternately in the tire circumferential direction.

EP 3 189 983 A1 discloses a pneumatic tire having a tread portion with a first tread pattern and a second tread pattern. The first tread pattern and the second tread pattern are formed substantially symmetrically to the tire equator and arranged such that their profile phases are shifted from each other in the circumferential direction of the tire. Each of the first tread pattern and the second tread pattern is provided with lateral inclined grooves each extending axially inwardly with an inclination from a tread edge to an axially inner end. ck located near the tire equator, wherein an inner connecting groove connects a pair of circumferentially adjacent lateral inclined grooves, and an outer connecting groove connects a pair of circumferentially adjacent lateral inclined grooves. A central connecting groove is arranged to connect a pair of axially adjacent inclined grooves.

EP 3 401 123 A2 discloses a pneumatic tire having a tread portion. The tread portion includes a plurality of oblique grooves extending obliquely from a first tread edge positioned on one side in the tire axial direction to a tire equator, and a plurality of oblique land portions each defined between a pair of the oblique grooves adjacent to each other in the tire circumferential direction. Each of the oblique land portions is provided with a plurality of connecting grooves each connected between the pair of oblique grooves.

Brief description of the invention

Technical problem

An object of the present invention is to provide a pneumatic tire which can provide improved traction performance on snow while adequately maintaining mileage on unpaved roads.

the solution of the problem

[0006] This object is achieved according to the invention with a pneumatic tire as set out in claims 1, 8 and 9. In order to achieve the above-described object, a pneumatic tire for which a direction of rotation is determined includes a tread portion extending in a tire circumferential direction and having an annular shape, a pair of sidewall portions each disposed on both sides of the tread portion, and a pair of bead portions each disposed on an inner side of the sidewall portions in a tire radial direction. The tread portion has an outer surface on which a plurality of lug grooves extending in a tire width direction and narrow circumferential grooves connecting adjacent lug grooves in the tire circumferential direction are formed. The tread portion includes a plurality of center blocks defined on a center side by the lug grooves and the narrow circumferential grooves. The center blocks include first center blocks arranged eccentrically on one side in the tire width direction with respect to a tire equator and second center blocks arranged eccentrically on another side in the tire width direction with respect to the tire equator. The first center blocks and the second center blocks are arranged alternately in the tire circumferential direction. Each of the first center blocks and each of the second center blocks includes a front ground contact side axial edge that runs along the tire width direction on a front ground contact side and crosses the tire equator, a rear ground contact side axial edge that runs along the tire width direction on a rear ground contact side and crosses the tire equator, a pair of front ground contact side diagonal edges that run diagonally such that a block width gradually increases from both ends of the front ground contact side axial edge to the rear ground contact side, and a rear ground contact side diagonal edge that is inclined in a region protruding from the tire equator in a direction different from one of the pair of front ground contact side diagonal edges and that connects one of the pair of front ground contact side diagonal edges and the rear ground contact side axial edge. Each of the axial edge of the front ground contact side (e1) and the axial edge of the rear ground contact side (e2) has an angle with respect to the tire width direction in a range of -10° to 10°.

Advantageous effects of the invention

In an embodiment according to the present invention, in the tire including a block-based tread pattern having the plurality of blocks defined by the lug grooves and the narrow circumferential grooves, the center blocks arranged near the tire equator are configured to have the shape described above. Thus, groove components in the tire width direction of the lug grooves can be sufficiently ensured, and traction performance on unpaved roads (hereinafter referred to as off-road traction performance) and traction performance on snow can be improved. In particular, the center block arranged near the tire equator has the plurality of axial edges and diagonal edges. Accordingly, edge components with respect to both the tire width direction and the tire circumferential direction can be increased, resulting in improvement. enhancing the traction performance on snow. Consequently, the off-road traction performance can be appropriately maintained and the traction performance on snow can be improved if the edge components are increased.

In an embodiment of the present invention, in each of the first center block and the second center block, a distance A from a connection point between the axial edge of the rear ground contact side and the diagonal edge of the rear ground contact side to the tire equator, and a distance B from a connection point between the axial edge of the front ground contact side and the other of the pair of diagonal edges of the front ground contact side that is not connected to the diagonal edge of the rear ground contact side to the tire equator preferably satisfy a relationship of 0.40 ≤ A/B ≤ 0.68. Consequently, the off-road traction performance and the snow traction performance can be improved in a balanced manner.

In an embodiment of the present invention, an angle α formed by the diagonal edge of the rear ground contact side of the first center block or the second center block and the axial edge of the front ground contact side of the second center block or the first center block is preferably in a range of 55° ≤ α ≤ 75°. Consequently, the off-road traction performance and the snow traction performance can be improved in a balanced manner.

In an embodiment of the present invention, the lug grooves preferably include lug grooves extending to an inner side in the tire width direction from a tread edge on one side with respect to the tire equator and intersecting with the tire equator, and lug grooves extending to an inner side in the tire width direction from a tread edge on the other side with respect to the tire equator and intersecting with the tire equator. Preferably, the lug grooves are arranged alternately in the tire circumferential direction. Each of the lug grooves preferably includes a first groove portion intersecting with the tire equator and extending in the tire width direction, and a second groove portion inclined from one end of the first groove portion at a smaller angle than that of the first groove portion with respect to the tire circumferential direction and extending to the tread edge. Another end of the first groove portion is preferably in communication with the second groove portion of the lug groove adjacent in the tire circumferential direction. The first groove portion is preferably located on the front ground contact side of an end portion on the tread edge side of the lug groove. When a distance from the tire equator to the tread edge is W, a region between a position separated from the tire equator in the tire width direction by 0.5W and the tire equator is an inner region, and a region between the position separated from the tire equator in the tire width direction by 0.5W and the tread edge is an outer region, the second groove portion is preferably curved or bent so that an average angle with respect to the tire circumferential direction of the second groove portion in the inner region is smaller than an average angle with respect to the tire circumferential direction of the second groove portion in the outer region. The center block preferably has a maximum length in the tire width direction that is 25% to 35% of an extended tread width. The lug grooves each formed of the first groove portion and the second groove portion are provided, and thus low noise performance can be improved while improving off-road traction performance. In other words, the first groove portions extending along the tire width direction are arranged near the tire equator where the contribution to traction performance is large, and the first groove portions communicate with the other lug grooves (the second groove portions), and thus the traction performance can be effectively improved. Further, the second groove portions are curved or bent as described above, and thus the groove length can be increased. In addition, the traction performance can be improved and the occurrence of air column resonance can be reduced. In addition, by properly ensuring the maximum width of the center block, the block rigidity can be sufficiently ensured and favorable traction performance can be exhibited.

In an embodiment of the present invention, a plurality of shoulder blocks are preferably defined on a shoulder side of the tread portion by the lug grooves and the circumferential narrow grooves, and shallow grooves having at least one bending point are preferably formed in road contact surfaces of each of the center blocks and each of the shoulder blocks. In particular, the shallow groove has the bending point. Thus, groove components in the tire circumferential direction and groove components in the tire width direction can be increased in a balanced manner, and traction performance on snow in the tire circumferential direction and in the width direction can be effectively improved.

In an embodiment of the present invention, the shallow groove formed in each of the center blocks preferably has one end communicating with each of the narrow circumferential grooves and another end communicating with the lug grooves. Preferably, when the shallow grooves formed in each of the center blocks project toward the tire equator, the protrusion components of the shallow grooves do not overlap each other. The shallow groove formed in the shoulder block preferably has both ends terminating inside the block, and the shallow groove is preferably located on the front ground contact side of a crest of the shoulder block located on an inner side in the tire width direction on the road contact surface. By thus providing the shallow grooves having the appropriate shape in the center blocks located near the tire equator where the contribution to traction performance is large, the traction performance on snow can be effectively improved. In addition, since the shallow grooves are arranged as described above so as not to overlap each other, excessive decrease in block rigidity over the entire tire circumference can be avoided, the snow traction performance and the off-road traction performance in the tire circumferential direction can be excellently matched, and these performances can be provided to a high degree in a compatible manner. Furthermore, the edge components on the front ground contact side can be increased and the snow performance can be effectively improved while suppressing the decrease in the rigidity of the shoulder blocks. On the other hand, since there is no shallow groove on the rear ground contact side and block rigidity and the amount of rubber are ensured, uneven wear (sawtooth wear) can be effectively suppressed.

In an embodiment of the present invention, the lug groove preferably has a maximum depth of 15 mm to 28 mm. In a heavy-duty pneumatic tire having such characteristics in terms of traction performance, stone rejection performance and low noise performance, an embodiment of the present invention can exhibit particularly excellent performance.

In the embodiment of the present invention, the "tread edges" refer to both ends of a tread pattern part of the tire when the tire is mounted on a regular rim, inflated to a regular internal pressure, and unloaded (unloaded state). The "distance W from the tire equator to the tread edge in the tire width direction" in the embodiment of the present invention corresponds to 1/2 of an extended tread width (“tread width” specified by JATMA) which is a linear distance between the tread edges measured along the tire width direction in the state described above. A "regular rim" is a rim defined by a standard for each tire according to a system of standards that includes standards that the tires meet, and refers to a "standard rim" as defined by the Japan Automobile Tire Manufacturers Association Inc. (JATMA), a "draft rim" as defined by the Tire and Rim Association Inc. (TRA), and a "measurement rim" as defined by the European Tire and Rim Technical Organization (ETRTO). In the system of standards, including standards that tires meet, "regular internal pressure" is an air pressure defined by each of the standards for each tire and is referred to as "maximum air pressure" in the case of JATMA, as the maximum value in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and as "INFLATION PRESSURE" in the case of ETRTO.

However, the “regular internal pressure” is 180 kPa in a case where a tire is a passenger car tire.

Short description of the drawings

• 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention.
• 2 is a front view illustrating a tread surface of a pneumatic tire according to an embodiment of the present invention.
• 3 is a cross-sectional view taken on the tread surface of 2 formed central blocks.
• 4(a) and 4(b) are front views each illustrating another prior art example of center blocks formed on the tread surface.

Description of embodiments

Configurations of embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As in 1 , a pneumatic tire of an embodiment of the present invention includes a tread portion 1, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged in the sidewall portions 2 on an inner side in the tire radial direction. In 1 reference character “CL” denotes a tire equator and reference character “E” denotes a tread edge. In the illustrated example, the tread edges E coincide with edges on an outer side in the tire width direction of blocks that are outermost in the tire width direction (edge portions formed by road contact surfaces of the blocks on an outer side in the tire width direction and side surfaces on an outer side in the tire width direction). Although in 1 not illustrated because 1 is a meridian cross-sectional view, the tread portion 1, the sidewall portions 2 and the bead portions 3 each extend in the tire circumferential direction to form a ring shape. Thus, a toroidal basic structure of the pneumatic tire is configured. Although the description using 1 Essentially based on the illustrated meridian cross-section, all tire components extend in the tire circumferential direction and form the ring shape.

A carcass layer 4 is disposed between the left and right pairs of bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction and is folded back from a vehicle inner side to a vehicle outer side around a bead core 5 disposed in each of the bead portions 3. In addition, bead fillers 6 are disposed on the periphery of the bead cores 5, and each bead filler 6 is enclosed by a main body portion and a folded back portion of the carcass layer 4. On the other hand, in the tread portion 1, a plurality of belt layers 7 (four layers in 1 ) is embedded on an outer peripheral side of the carcass layer 4. The belt layers 7 each include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, with the reinforcing cords of the different layers being arranged crosswise. In these belt layers 7, an inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in a range of, for example, 10° to 60°. Although not in the pneumatic tire of 1 In the embodiment of the present invention, a belt reinforcing layer (not illustrated) may be additionally provided on the outer peripheral side of the belt layers 7. When the belt reinforcing layer is provided, the belt reinforcing layer includes, for example, an organic fiber cord oriented in the tire circumferential direction. An angle of the organic fiber cord with respect to the tire circumferential direction may be set to, for example, 0° to 5°.

A tread rubber layer 11 is arranged on the outer peripheral side of the carcass layer 4 and the belt layers 7 in the tread portion 1. A side rubber layer 12 is arranged on an outer peripheral side of the carcass layer 4 (outer side in the tire width direction) in the sidewall portions 2. A rim cushion rubber layer 13 is arranged on the outer peripheral side of the carcass layer 4 (outer side in the tire width direction) in the bead portions 3. The tread rubber layer 11 may be structured such that two kinds of rubber layers (a crown tread rubber layer and an under tread rubber layer) having different physical properties are layered in the tire radial direction.

The embodiment of the present invention can be applied to such a general pneumatic tire; however, the cross-sectional structure thereof is not limited to the basic structure described above.

As in 2 , the lug grooves 20 (may be referred to as “lug grooves 20 on one side” in the following description) and the lug grooves 30 (may be referred to as “lug grooves 30 on the other side” in the following description) are provided on a surface of the tread portion 1 of the pneumatic tire according to the embodiment of the present invention. The lug grooves 20 extend from the tread edge E on one side (the right side in the drawing) with respect to the tire equator CL to an inner side in the tire width direction and overlap with the tire equator CL. The lug grooves 30 extend from the tread edge E on the other side (the left side in the drawing) with respect to the tire equator CL to an inner side in the tire width direction and overlap with the tire equator CL. A plurality of lug grooves 20 on one side and a plurality of lug grooves 30 on the other side are provided.

The lug grooves 20, 30 include first groove portions 21, 31 which intersect with the tire equator CL and extend along the tire width direction, and second groove portions 22, 32 which are inclined from one end of the first groove portions 21, 31 at a smaller angle than that of the first groove portions 21, 31 with respect to the tire circumferential direction and extend to the tread edges E, respectively. Specifically, the lug groove 20 includes, on one side, the first groove portion 21 which intersects with the tire equator CL and extends along the tire width direction, and the second groove portion 22 which is inclined from the one end of the first groove portion 21 (the end portion on the one side (the right side in the drawing) with respect to the tire equator) at an angle smaller than that of the first groove portion 21 with respect to the tire circumferential direction and extends to the tread edge E. Likewise, the lug groove 30 on the other side includes the first groove portion 31 which intersects with the tire equator CL and extends along the tire width direction, and the second groove portion 32 which is inclined from the one end of the first groove portion 31 (the end portion on the other side (left side in the drawing) with respect to the tire equator) at an angle smaller than that of the first groove portion 31 with respect to the tire circumferential direction and extends to the tread edge E.

The lug grooves 20 on one side and the lug grooves 30 on the other side are alternately arranged one after another in the tire circumferential direction. Note that, as described above, since the lug grooves 20, 30 extend substantially in directions opposite to each other from the tire equator CL, the first groove portions 21 of the lug grooves 20 on one side and the first groove portions 31 of the lug grooves 30 on the other side are alternately arranged in the tire circumferential direction on the tire equator CL. Meanwhile, the second groove portions 22 of the lug grooves 20 on the one side are arranged at intervals in the tire circumferential direction on one side with respect to the tire equator CL, and the second groove portions 32 of the lug grooves 30 on the other side are arranged at intervals in the tire circumferential direction on the other side with respect to the tire equator CL. In the embodiment of the present invention, as long as the first groove portions 21, 31 are alternately arranged so as to be adjacent to each other on the tire equator CL, the lug grooves 20, 30 are regarded as being alternately arranged unless otherwise specified.

The other ends of the first groove portions 21, 31 of the respective lug grooves 20, 30 are connected to the second groove portions 32, 22 of the other lug grooves 30, 20 adjacent in the tire circumferential direction. In other words, the first groove portion 21 of the lug groove 20 on one side is connected to the second groove portion 32 of the lug groove 30 on the other side adjacent in the tire circumferential direction, and the first groove portion 31 of the lug groove 30 on the other side is connected to the second groove portion 22 of the lug groove 20 on the one side adjacent in the tire circumferential direction.

The first groove portions 21, 31 of the respective lug grooves 20, 30 are located on a front ground contact side (entrance side) of end portions on the tread edge E side of the respective lug grooves 20, 30. That is, the pneumatic tire of the embodiment of the present invention is a tire in which a rotation direction R is provided. Meanwhile, each of the lug grooves 20, 30 has a shape for the entire groove inclined in a direction opposite to the rotation direction R from the tire equator CL side to an outside in the tire width direction.

In the embodiment of the present invention, in addition to the lug grooves 20, 30, narrow circumferential grooves 40 are provided. Each of the narrow circumferential grooves 40 extends along the tire circumferential direction to connect the second groove portions adjacent in the tire circumferential direction on one side of the tire equator CL, that is, to connect the second groove portions 22 of the lug grooves 20 on the one side adjacent in the tire circumferential direction on one side with respect to the tire equator CL, or the second groove portions 32 of the lug grooves 30 on the other side adjacent in the tire circumferential direction on the other side with respect to the tire equator CL.

The narrow circumferential groove 40 is a groove having a groove width that is smaller than those of the lug grooves 20, 30. In particular, the lug grooves 20, 30 each have a groove width of, for example, 5 mm to 30 mm and a groove depth of, for example, 8 mm to 28 mm. In particular, when the tire is a heavy-duty pneumatic tire, the groove depth is preferably, for example, 15 mm to 28 mm. In contrast, the narrow Circumferential groove 40 has a groove width of e.g. 7 mm to 11 mm and a groove depth of e.g. 15 mm to 20 mm.

The lug grooves 20, 30 and the circumferential narrow grooves 40 separate a plurality of blocks 50. Of the plurality of blocks 50, a block positioned closer to the tire equator CL side (center side of the tread portion 1) than the circumferential narrow groove 40 is called a center block 51, and a block positioned closer to the tread edge E side (shoulder side of the tread portion 1) than the circumferential narrow groove 40 is called a shoulder block 52. The center blocks 51 include first center blocks 51A arranged eccentrically on one side in the tire width direction with respect to the tire equator CL, and second center blocks 51B arranged eccentrically on the other side in the tire width direction with respect to the tire equator CL. In other words, each of the first center blocks 51A and the second center blocks 51B has a shape such that at least a portion of the first center block 51A and the second center block 51B protrudes from the tire equator CL in the tire width direction. The first center blocks 51A and the second center blocks 51B are arranged alternately in the tire circumferential direction.

As in 3 As illustrated, each of the center blocks 51 includes a plurality of edges e. Specifically, each center block 51 includes a front ground contact side axial edge e1 (entering side) that runs along the tire width direction on the front ground contact side (entering side) and crosses the tire equator CL, a rear ground contact side axial edge e2 (exiting side) that runs along the tire width direction on the rear ground contact side (exiting side) and crosses the tire equator CL, a pair of front ground contact side diagonal edges e3, e4 that run diagonally so that the block width in the tire width direction gradually increases from opposite ends of the front ground contact side axial edge e1 to the rear ground contact side, and a rear ground contact side diagonal edge e5 that is inclined in a different direction from the front ground contact side diagonal edge e3 in a region that protrudes from the tire equator CL and intersects the front ground contact side diagonal edge e3 and the rear ground contact side. In particular, the diagonal edge e3 of the front ground contact side and the diagonal edge e5 of the rear ground contact side are preferably inclined in directions opposite to each other. Note that, in the illustrated example, each center block 51 includes, in addition to the aforementioned edges e1 to e5, an edge extending along the second groove portion 22, 32 of the lug groove 20, 30 and an edge extending along the narrow circumferential groove 40, and the diagonal edge e3 of the front ground contact side and the diagonal edge e5 of the rear ground contact side are inclined in directions opposite to each other. In the illustrated example, all the edges constituting each center block 51 are straight; however, each center block 51 may include an edge having a curved shape or a zigzag shape.

The axial edge of the front ground contact side e1 and the axial edge of the rear ground contact side e2 are both arranged at an angle of -10° or larger and 10° or smaller with respect to the tire width direction. In the illustrated example, the axial edges e1, e2 both extend at an angle of 0° with respect to the tire width direction.

The center block 51 includes the above-described plurality of edges e1 to e5, and thus a cutout shape is formed in a region of the center block 51 protruding from the tire equator CL. Specifically, as this cutout shape, a triangular region surrounded by the first groove portion 21 of the lug groove 20 on one side, the second groove portion 32 of the lug groove 30 on the other side located adjacent to the lug groove 20 in the tire circumferential direction, and the diagonal edge e5 of the rear ground contact side of the first center block 51A is formed. In addition, a triangular region is formed which is surrounded by the first groove portion 31 of the lug groove 30 on the other side, the second groove portion 22 of the lug groove 20 on the one side which is adjacent to the lug groove 30 in the tire circumferential direction, and the diagonal edge of the rear ground contact side e5 of the second center block 51B. By forming such triangular regions, the groove volume of the lug grooves 20, 30 can be increased and mud can be gripped on unpaved roads, and meanwhile, snow can be gripped on snow-covered roads, which contributes to improving off-road traction performance and traction performance on snow.

According to the pneumatic tire described above, in a tire including a block-based tread pattern in which the plurality of blocks 50 are defined by the lug grooves 20, 30 and the narrow circumferential grooves 40, the center blocks 51 arranged near the tire equator CL are configured to have the shape described above. Thus, groove components in tires width direction of the lug grooves 20, 30 can be sufficiently ensured, and off-road traction performance and snow traction performance can be improved. In particular, each of the center blocks 51 arranged near the tire equator CL has a plurality of axial edges and diagonal edges. Accordingly, edge components with respect to both the tire width direction and the tire circumferential direction can be increased, which contributes to improving snow traction performance. Consequently, off-road traction performance can be properly maintained, and snow traction performance can be improved if the edge components are increased.

Further, by the presence of the narrow circumferential grooves 40, the noise is scattered by the narrow circumferential grooves 40, whereby the low noise performance can be improved. In addition, groove components can be added in the tire circumferential direction by the narrow circumferential grooves 40, and thus lateral slip of the tire during traction is prevented and stability can be improved.

In the pneumatic tire described above, in each of the first center block 51A and the second center block 51B, P1 is a connection point between the axial edge of the rear ground contact side e2 and the diagonal edge of the rear ground contact side e5, and P2 is a connection point between the axial edge of the front ground contact side e1 and the diagonal edge of the front ground contact side e4. The distance between the connection point P1 on the axial edge of the rear ground contact side e2 and the tire equator CL is defined as a distance A, and the distance between the connection point P2 on the axial edge of the front ground contact side e1 and the tire equator CL is defined as a distance B (see 3 ). At this time, the distance A and the distance B preferably satisfy a relationship of 0.40≤A/B≤0.68. By appropriately setting the distance A with respect to the distance B as just described, the off-road traction performance and the snow traction performance can be improved in a balanced manner. Here, if the ratio between the distance A and the distance B is less than 0.40, the block rigidity decreases and the uneven wear resistance performance tends to deteriorate. On the other hand, if the ratio between the distance A and the distance B is greater than 0.68, sufficient traction performance cannot be obtained.

Further, the angle formed by the diagonal edge of the rear ground contact side e5 of the first center block 51A or the second center block 51B and the axial edge of the front ground contact side e1 of the second center block 51B or the first center block 51A is defined as an angle α. The angle α is preferably set in a range of 55°≤α≤75°. Further, the angle formed by the diagonal edge of the front ground contact side e3 of the first center block 51A or the second center block 51B and the axial edge of the rear ground contact side e2 of the second center block 51B or the first center block 51A is defined as an angle β. The angle β can be set in a range of 50°≤β≤60°. By appropriately setting the angle α or the angle β as just described, the off-road traction performance and the traction performance on snow can be improved in a balanced manner. Here, if the angle α or the angle β is outside the range described above, the effect of improving the traction performance cannot be sufficiently achieved. Note that when the axial edge e1 of the front ground contact side, the axial edge e2 of the rear ground contact side, the diagonal edge e3 of the front ground contact side, or the diagonal edge e5 of the rear ground contact side is not straight but formed in a curved shape or a zigzag shape, the angle α or the angle β as described above is measured based on straight lines connecting both end portions of the edges.

If in 2 the distance from the tire equator CL to the tread edge E in the tire width direction is denoted by W, the area between a position separated by 0.50 W from the tire equator CL in the tire width direction is an inner area Sa, and the area between the position separated by 0.50 W from the tire equator CL in the tire width direction and the tread edge E is an outer area Sb, the second groove portions 22, 32 of the lug grooves 20, 30 are each curved or bent such that an average angle θa of the second groove portions 22, 32 with respect to the tire circumferential direction in the inner area Sa is smaller than an average angle θb of the second groove portions 22, 32 with respect to the tire circumferential direction in the outer area Sb. In other words, the second groove portions 22, 32 of the lug grooves 20, 30 gently curve so that the inclination angles with respect to the tire circumferential direction gradually decrease from the tread edge E side to the tire equator CL side, or are bent with at least one bending point. In addition, the maximum length L in the tire width direction of the center block 51 is set to 25% to 35% of the developed tread width TW.

Since the tread pattern is configured as described above, the low noise performance can be improved while the off-road traction performance is improved. In other words, the first groove portions 21, 31 extending along the tire width direction are arranged near the tire equator CL where the contribution to traction performance is large, and the first groove portions 21, 31 communicate with the second groove portions 32, 32 of the lug grooves 30, 20, and thus the traction performance can be effectively improved. Further, the second groove portions 22, 32 are curved or bent as described above, and thus the groove length can be increased. In addition, the traction performance can be improved and the occurrence of air column resonance can be reduced. In addition, by appropriately ensuring the maximum width of the center block 51, the block rigidity can be sufficiently ensured and favorable traction performance can be exhibited. Here, if the size relationship between the average angles θa and θb of the second groove portions 22, 32 is reversed, the curved or bent shape of the second groove portions 22, 32 is inappropriate, and the effect of improving the traction performance cannot be sufficiently achieved.

The second groove portions 22, 32 of the lug grooves 20, 30 are configured so that the angle with respect to the tire circumferential direction gradually decreases toward the tire equator CL as described above. In such a case, the average angle θa of the second groove portions 22, 32 with respect to the tire circumferential direction in the inner region Sa is preferably set to a value of 35° to 45°, and the average angle θb of the second groove portions 22, 32 with respect to the tire circumferential direction in the outer region Sb is preferably set to a value of 70° to 85°. Accordingly, each portion of the second groove portions 22, 32 has an appropriate angle, and the second groove portions 22, 32 are each formed in an appropriate curved or bent shape. Consequently, the traction performance is advantageously improved by increasing the lug groove length. When the average angle θa of the second groove portions 22, 32 is less than 35°, the groove components in the tire width direction are reduced, and thus it is difficult to sufficiently improve the traction performance. When the average angle θa of the second groove portions 22, 32 exceeds 45°, the difference from the average angle θb becomes small, the second groove portions 22, 32 cannot be sufficiently bent or curved, and the lug groove length does not increase sufficiently, and thus it is difficult to sufficiently improve the traction performance. When the average angle θb of the second groove portions 22, 32 is less than 70°, the difference from the average angle θa becomes small, the second groove portions 22, 32 cannot be sufficiently bent or curved, and the lug groove length does not increase sufficiently, and thus it is difficult to sufficiently improve the traction performance. When the average angle θb of the second groove portions 22, 32 exceeds 85°, the difference from the average angle θa becomes large, and the second groove portions 22, 32 are greatly curved or bent, and thus it is difficult to ensure an appropriate groove shape.

In addition, it is to be noted that the average angle of each of the second groove portions 22, 32 of the lug grooves 20, 30 can be obtained as an angle formed with respect to the tire circumferential direction by a straight line connecting center points in the groove width direction of the lug grooves 20, 30 at boundary positions of the area of each of the lug grooves 20, 30. It is to be noted that, as illustrated, on the tire equator CL and the tread edge E, the center point on the tire equator CL or the tread edge E of extension lines drawn to the tire equator CL or the tread edge E of each of the second groove portions 22, 32 is used.

As described above, the first groove portions 21, 31 are mainly arranged in the vicinity of the tire equator CL where the contribution to traction performance is large to ensure groove constituents in the tire width direction. Accordingly, the first groove portions 21, 31 preferably extend in a direction substantially perpendicular to the tire circumferential direction. Specifically, an angle θc of the first groove portions 21, 31 with respect to the tire circumferential direction is preferably from 80° to 100°. As a result, the traction performance can be effectively improved by the first groove portions 21, 31. When the angle θc of the first groove portions 21, 31 is less than 80° or exceeds 100°, the inclination of the first groove portions 21, 31 with respect to the tire width direction increases and the groove components in the tire width direction cannot be sufficiently secured, and thus the effect of improving the traction performance is limited.

In addition, 2 a shallow groove 60 having at least one bending point is formed on a road contact surface of each of the blocks 50. The shallow groove 60 is a groove having a groove depth smaller than that of the lug grooves 20, 30 and the narrow circumferential groove 40, and the groove depth may preferably be set to 1 mm to 3 mm, and the groove width may be set to be, for example, 1 mm to 3 mm. When the groove depth of the shallow groove 60 is less than 1 mm, the shallow groove 60 is too shallow, and thus the effect produced by providing the shallow groove 60 cannot be achieved. When the groove depth of the shallow groove 60 exceeds 3 mm, the influence on the block rigidity increases. In the following description, the shallow groove 60 formed in the center block 51 is referred to as the shallow center groove 61, and the shallow groove 60 formed in the shoulder blocks 52 is referred to as the shallow shoulder groove 62. In the illustrated example, both the shallow center groove 61 and the shallow shoulder groove 62 have a bending point. Although the number of the shallow grooves 60 formed in each block 50 is not particularly limited, it is preferable that one shallow groove 60 is provided in each block 50 as illustrated in the drawing.

In the embodiment of the present invention, the shallow groove 60 having the bending point on the road contact surface of each block 50 is provided in the tire having the block-based tread pattern in which the plurality of blocks 50 are defined by the lug grooves 20, 30 and the narrow circumferential grooves 40 as described above to ensure off-road traction performance. Thus, groove components in the tire circumferential direction and groove components in the tire width direction can be increased in a balanced manner, and the traction performance on snow in the tire circumferential direction and in the width direction can be effectively improved.

Furthermore, as illustrated, the shallow center groove 61 preferably has one end communicating with the narrow circumferential groove 40 and the other end communicating with the second groove portion 22, 32 of the lug groove 20, 30. Further, the shallow center groove 61 is preferably bent along an outer edge on the entering side or the exiting side of the center block 51. At this time, the shallow center groove 61 is preferably located within a range of ±5 mm in the tire circumferential direction from the center position in the tire circumferential direction of the center block 51. In addition, it is preferable that when the shallow center grooves 61 protrude toward the tire equator CL, protrusion components of the shallow center grooves 61 do not overlap with each other. By thus providing the shallow center grooves 61 having the appropriate shape in the center blocks 51 located near the tire equator CL where a contribution to traction performance is large, the snow traction performance can be effectively improved. In addition, since the shallow center grooves 61 do not overlap as described above, an excessive decrease in block rigidity over the entire tire circumference can be avoided, the snow traction performance and the off-road traction performance in the tire circumferential direction can be excellently balanced, and these performances can be provided to a high degree in a compatible manner.

On the other hand, as illustrated, both ends of the shallow shoulder groove 62 preferably blindly terminate in the shoulder block 52. In addition, the shallow shoulder groove 62 is preferably bent along an outer edge on the entering side of the shoulder block 52. In addition, the shallow shoulder groove 62 is preferably arranged on the entering side with respect to a position of a crest on an inner side in the tire width direction of the road contact surface of the shoulder block 52. By providing the shallow shoulder grooves 62 in this manner, the edge components on the entering side can be increased and the performance on snow can be effectively improved while suppressing the decrease in the rigidity of the shoulder blocks 52. On the other hand, since there is no shallow groove on the exiting side, uneven wear (sawtooth wear) can be effectively suppressed and the block rigidity and the rubber amount can be ensured.

While the lug grooves 20, 30 may have a completely uniform groove depth, the first groove portions 21, 31 are preferably configured to be appropriately shallower than the second groove portions 22, 32. In particular, the groove depth of the first groove portions 21, 31 of the lug grooves 20, 30 is preferably 65% to 75% of the groove depth of the second groove portions 22, 32. This can increase the rigidity of the blocks (center blocks 51) adjacent to the first groove portions 21, 31, which is advantageous in improving traction performance.

While the groove depths of each of the lug grooves 20, 30 and the narrow circumferential grooves 40 can be set to the ranges described above, the narrow circumferential groove 40 is preferably configured to be appropriately shallower than the lug grooves 20, 30. Specifically, the groove depth of the narrow circumferential groove 40 is preferably set to be 75% to 85% of the groove depth of the second groove portions 22, 32 of the lug grooves 20, 30. Thus, since the narrow circumferential groove 40 is provided to be appropriately shallower than the second groove portions 22, 32, the rigidity of the blocks (the center block 51 and the shoulder block 52) adjacent to the narrow circumferential grooves 40 can be increased, which is advantageous in improving traction performance.

Examples

Pneumatic tires according to the prior art example, comparative example and claims 1 to 6 were manufactured, each of the pneumatic tires having a tire size of 315/80R22.5, a 1 illustrated basic structure includes a tread portion in which a plurality of lug grooves extending in the tire width direction and narrow circumferential grooves connecting adjacent lug grooves in the tire circumferential direction are formed, and a plurality of center blocks defined on a center side of the tread portion by the lug grooves and the narrow circumferential grooves. In the pneumatic tire, the shape of the center blocks, the presence or absence of diagonal edges on a rear ground contact side, the presence or absence of axial edges on the front ground contact side and a rear ground contact side, a ratio (A/B) of a distance A to a distance B, an inclination angle α of diagonal edges on the rear ground contact side, an angle change of the lug groove, an angle near a tire equator of the lug groove, the presence or absence of an opening of the lug groove to the other lug groove, and the arrangement of a shallow groove in each of the blocks were set as shown in Table 1.

For “shape of the middle block” in Table 1, the corresponding drawing number is described. The shape of the middle blocks of the 4(a) The prior art example illustrated differs largely from that in 2 illustrated form, but sections correspond to those of 2 , as shown in the drawings. In addition, the shape of the middle blocks of the 4(b) illustrated comparative example of the prior art from that of 2 by the fact that the middle block has no diagonal edge (in 2 illustrated as edge e5) on the rear ground contact side.

Furthermore, "angle change of lug groove" in Table 1 means whether the inclination angle of the lug groove with respect to the tire circumferential direction gradually decreases from the tread edge side toward the tire equator side. Furthermore, "angle of lug groove near the tire equator" in Table 1 means whether the angle of the lug groove with respect to the tire circumferential direction is perpendicular near the tire equator.

The pneumatic tires were evaluated for off-road traction performance and snow traction performance according to the following evaluation method, and the results are shown in Table 1.

Off-road traction performance:

Each of the test tires was mounted on a wheel with a rim size of 22.5×9.00, inflated to an air pressure of 850 kPa, and mounted on a drive shaft of a test vehicle (truck with the axle arrangement of 6×4), and subjected to sensory evaluation by a test driver on a test track of an unpaved road. The evaluation results are expressed as index values, with the value of the prior art example set as 100. Larger index values indicate excellent off-road traction performance.

Traction performance on snow

Each of the test tires was mounted on a wheel with a rim size of 22.5×9.00, inflated to an air pressure of 850 kPa, and mounted on a drive shaft of a test vehicle (truck with the axle arrangement of 6×4), and subjected to sensory evaluation by a test driver on a test track of a snow-covered road. The evaluation results are expressed as index values, with the value of the prior art example set as 100. Larger index values indicate excellent traction performance on snow.
[Table 1-I] Example of the state of the art Comparative example of the state of the art example 1 Example 2 Shape of the middle block 4(a) 4(b) 3 3 Presence of diagonal edges on the rear ground contact side Yes No Yes Yes Presence of axial edges on the front ground contact side and the rear ground contact side No Yes Yes Yes Ratio of distance A to distance B (A/B) - - 0.3 0.8 Inclination angle α of the diagonal edge on the rear ground contact side - - 45° 45° Angle change of the lug groove Gradually reduced Gradually reduced Gradually reduced Gradually reduced Angle of the lug groove near the tire equator Not vertical Perpendicular Perpendicular Perpendicular Presence of an opening of one lug groove to another lug groove No Yes Yes Yes Arrangement of a shallow groove in each block No No No No Off-road traction performance 100 98 103 101 Traction performance on snow 100 98 103 103 [Table 1-II] Example 3 Example 4 Example 5 Example 6 Shape of the middle block 3 3 3 3 Presence of diagonal edges on the rear ground contact side Yes Yes Yes Yes Presence of axial edges on the front ground contact side and the rear ground contact side Yes Yes Yes Yes Ratio of distance A to distance B (A/B) 0.5 0.5 0.5 0.5 Inclination angle α of the diagonal edge on the rear ground contact side 45° 80° 60° 60° Angle change of the lug groove Gradually reduced Gradually reduced Gradually reduced Gradually reduced Angle of the lug groove near the tire equator Perpendicular Perpendicular Perpendicular Perpendicular Presence of an opening of one lug groove to another lug groove Yes Yes Yes Yes Arrangement of a shallow groove in each block No No No Yes Off-road traction performance 105 105 106 106 Traction performance on snow 105 105 107 109

As shown in Table 1, the off-road traction performance and the snow traction performance were improved in each of Examples 1 to 6 compared with the prior art example.

On the other hand, since each of the center blocks is configured such that the center block in the comparative example does not have a diagonal edge on the rear ground contact side, the effect of improving the off-road traction performance and the traction performance on snow cannot be sufficiently achieved.

List of reference symbols

1

Tread section

2

Side wall section

3

Bead section

20, 30

Stud groove

40

Narrow circumferential groove

51

Middle block

51A

First middle block

51B

Second middle block

CL

Tire equator

E

Tread edge

e

edge

e1

Axial edge on the front ground contact side

e2

Axial edge on the rear ground contact side

e3, e4

Diagonal edge on the front ground contact side

e5

Diagonal edge on the rear ground contact side

Claims (9)

A pneumatic tire for which a direction of rotation is predetermined, the pneumatic tire comprising: a tread portion (1) extending in a tire circumferential direction and having an annular shape; a pair of sidewall portions (2) respectively arranged on both sides of the tread portion (1); and a pair of bead portions (3) each arranged on an inner side of the sidewall portions (2) in the tire radial direction, the tread portion (1) having an outer surface on which a plurality of lug grooves (20, 30) extending in the tire width direction and narrow circumferential grooves (40) connecting adjacent lug grooves (20, 30) in the tire circumferential direction are formed, the tread portion (1) comprising a plurality of center blocks (51) defined on a center side by the lug grooves (20, 30) and the narrow circumferential grooves (40), the center blocks (51) comprising first center blocks (51A) arranged eccentrically on one side in the tire width direction with respect to a tire equator (CL), and second center blocks (51B) arranged eccentrically on another side in the tire width direction with respect to the tire equator (CL), the first Center blocks (51A) and the second center blocks (51B) are alternately arranged in the tire circumferential direction, each of the first center blocks (51A) and each of the second center blocks (51B) having a front ground contact side axial edge (e1) running along the tire width direction on a front ground contact side and crossing the tire equator (CL), a rear ground contact side axial edge (e2) running along the tire width direction on a rear ground contact side and crossing the tire equator (CL), a pair of front ground contact side diagonal edges (e3, e4) running diagonally such that a block width gradually increases from both ends of the front ground contact side axial edge (e1) to the rear ground contact side, and a rear ground contact side diagonal edge (e5) running in a direction away from the tire equator (CL). standing portion inclined in a direction other than one of the pair of diagonal edges of the front ground contact side (e3, e4) and connecting one of the pair of diagonal edges of the front ground contact side (e3, e4) and the axial edge of the rear ground contact side (e2), and wherein each of the axial edge of the front ground contact side (e1) and the axial edge of the rear ground contact side (e2) has an angle with respect to the tire width direction in a range of -10° to 10°. Pneumatic tires according to Claim 1 wherein, in each of the first center block (51A) and the second center block (51B), a distance A from a connection point (P1) between the axial edge of the rear ground contact side (e2) and the diagonal edge of the rear ground contact side (e5) to the tire equator (CL), and a distance B from a connection point (P2) between the axial edge of the front ground contact side (e1) and the other of the pair of diagonal edges of the front ground contact side (e3, e4) which is not connected to the diagonal edge of the rear ground contact side (e5) to the tire equator (CL) satisfy a relationship 0.40 ≤ A/B ≤ 0.68. Pneumatic tires according to Claim 1 or 2 wherein an angle α formed by the diagonal edge of the rear ground contact side (e5) of the first center block (51A) or the second center block (51B) and the axial edge of the front ground contact side (e1) of the second center block (51B) or the first center block (51A) is in a range of 55° ≤ α ≤ 75°. Pneumatic tyres in accordance with one of the Claims 1 until 3 , wherein the lug grooves (20, 30) comprise lug grooves (20) extending to an inner side in the tire width direction from a tread edge (E) on one side with respect to the tire equator (CL) and intersecting with the tire equator (CL), and lug grooves (30) extending to an inner side in the tire width direction from a tread edge (E) on the other side with respect to the tire equator (CL) and intersecting with the tire equator (CL), wherein the lug grooves (20, 30) are arranged alternately in the tire circumferential direction, each of the lug grooves comprises a first groove portion (21, 31) intersecting with the tire equator (CL) and extending in the tire width direction, and a second groove portion (22, 32) extending from one end of the first groove portion (21, 31) at an angle smaller than that of the first groove portion (21, 31), is inclined with respect to the tire circumferential direction and extends toward the tread edge (E), another end of the first groove portion (21, 31) communicating with the second groove portion (22, 32) of the lug groove (20, 30) adjacent in the tire circumferential direction, the first groove portion (21, 31) being disposed on the front ground contact side of an end portion on the tread edge side of the lug groove (20, 30) when a distance from the tire equator (CL) to the tread edge (E) is W, a region between a position separated from the tire equator (CL) in the tire width direction by 0.5 W and the tire equator (CL) is an inner region (Sa), and a region between the position separated from the tire equator (CL) in the tire width direction by 0.5 W and the tread edge (E) is an outer region (Sb), the second groove portion (22, 32) is curved or bent such that an average angle (θa) with respect to the tire circumferential direction of the second groove portion (22, 32) in the inner region (Sa) is smaller than an average angle (θb) with respect to the tire circumferential direction of the second groove portion (22, 32) in the outer region (Sb), and the center block (51) has a maximum length L in the tire width direction which is 25% to 35% of an extended tread width (TW). Pneumatic tyres in accordance with one of the Claims 1 until 4 wherein a plurality of shoulder blocks (52) are defined on a shoulder side of the tread portion (1) by the lug grooves (20, 30) and the narrow circumferential grooves (40), and shallow grooves (60) having at least one bending point are formed in road contact surfaces of each of the center blocks (51) and each of the shoulder blocks (52). Pneumatic tires according to Claim 5 , wherein the shallow groove (61) formed in each of the center blocks (51) has one end communicating with each of the narrow circumferential grooves (40) and another end communicating with the lug grooves (20, 30), and projection components of the shallow grooves (60) do not overlap each other when the shallow grooves (61) formed in each of the center blocks (51) are projected toward the tire equator (CL), and the shallow groove (62) formed in the shoulder block (52) has both ends terminating inside the block (52), and the shallow groove (62) formed in the shoulder block (52) on the front floor con contact side of a vertex of the shoulder block (52) which is arranged on an inner side in the tire width direction on the road contact surface. Pneumatic tyres in accordance with one of the Claims 1 until 6 , wherein the lug groove (20, 30) has a maximum depth of 15 mm to 28 mm. A pneumatic tire for which a direction of rotation is predetermined, the pneumatic tire comprising: a tread portion (1) extending in a tire circumferential direction and having an annular shape; a pair of sidewall portions (2) respectively arranged on both sides of the tread portion (1); and a pair of bead portions (3) each arranged on an inner side of the sidewall portions (2) in a tire radial direction, wherein the tread portion (1) has an outer surface on which a plurality of lug grooves (20, 30) extending in the tire width direction and narrow circumferential grooves (40) connecting adjacent lug grooves (20, 30) in the tire circumferential direction are formed, wherein the tread portion (1) includes a plurality of center blocks (51) defined on a center side by the lug grooves (20, 30) and the narrow circumferential grooves (40), wherein the center blocks (51) include first center blocks (51A) arranged eccentrically on one side in the tire width direction with respect to a tire equator (CL), and second center blocks (51B) arranged eccentrically on another side in the tire width direction with respect to the tire equator (CL), wherein the first center blocks (51A) and the second center blocks (51B) are arranged alternately in the tire circumferential direction, wherein each of the first center blocks (51A) and each of the second center blocks (51B) has a front ground contact side axial edge (e1) running along the tire width direction on a front ground contact side and crossing the tire equator (CL), a rear ground contact side axial edge (e2) running along the tire width direction on a rear ground contact side and crossing the tire equator (CL), a pair of front ground contact side diagonal edges (e3, e4) running diagonally such that a block width gradually increases from both ends of the front ground contact side axial edge to the rear ground contact side, and a rear ground contact side diagonal edge extending in a region protruding from the tire equator (CL) in a different direction from one of the pair of front ground contact side diagonal edges (e3, e4) and connecting one of the pair of diagonal edges of the front ground contact side (e3, e4) and the axial edge of the rear ground contact side (e2), the lug grooves (20, 30) comprise lug grooves extending to an inner side in the tire width direction from a tread edge (E) on one side with respect to the tire equator (CL) and intersecting with the tire equator (CL), and lug grooves extending to an inner side in the tire width direction from a tread edge (E) on the other side with respect to the tire equator and intersecting with the tire equator (CL), the lug grooves being arranged alternately in the tire circumferential direction, each of the lug grooves comprises a first groove portion (21, 31) intersecting with the tire equator (CL) and extending in the tire width direction, and a second groove portion extending from one end of the first Groove portion (21, 31) is inclined at an angle smaller than that of the first groove portion (21, 31) with respect to the tire circumferential direction and extends toward the tread edge (E), another end of the first groove portion (21, 31) communicating with the second groove portion (22, 32) of the lug groove adjacent in the tire circumferential direction, wherein the first groove portion (21, 31) is arranged on the front ground contact side of an end portion on the tread edge side of the lug groove, when a distance from the tire equator (CL) to the tread edge (E) is W, a region between a position separated from the tire equator (CL) in the tire width direction by 0.5 W and the tire equator (CL) is an inner region, and a region between the position separated from the tire equator (CL) in the tire width direction by 0.5 W, and the tread edge (E) is an outer region, the second groove portion (22, 32) is curved or bent such that an average angle with respect to the tire circumferential direction of the second groove portion (22, 32) in the inner region is smaller than an average angle with respect to the tire circumferential direction of the second groove portion (22, 32) in the outer region, and the center block (51) has a maximum length L in the tire width direction which is 25% to 35% of an extended tread width (TW). A pneumatic tire for which a direction of rotation is predetermined, the pneumatic tire comprising: a tread portion (1) extending in a tire circumferential direction and having an annular shape; a pair of sidewall portions (2) respectively arranged on both sides of the tread portion (1); and a pair of bead portions (3) each arranged on an inner side of the sidewall portions (2) in a tire radial direction, the tread portion (1) having an outer surface on which a plurality of lug grooves (20, 30) extending in the tire width direction and narrow circumferential grooves (40) connecting adjacent lug grooves (20, 30) in the tire circumferential direction are formed, the tread portion (1) comprising a plurality of center blocks (51) defined on a center side by the lug grooves (20, 30) and the narrow circumferential grooves (40), the center blocks (51) comprising first center blocks (51A) arranged eccentrically on one side in the tire width direction with respect to a tire equator (CL), and second center blocks (51B) arranged eccentrically on another side in the tire width direction with respect to the tire equator (CL), the first Center blocks (51A) and the second center blocks (51B) are alternately arranged in the tire circumferential direction, each of the first center blocks (51A) and each of the second center blocks (51B) having a front ground contact side axial edge (e1) running along the tire width direction on a front ground contact side and crossing the tire equator (CL), a rear ground contact side axial edge (e2) running along the tire width direction on a rear ground contact side and crossing the tire equator (CL), a pair of front ground contact side diagonal edges (e3, e4) running diagonally such that a block width gradually increases from both ends of the front ground contact side axial edge (e1) to the rear ground contact side (e1), and a rear ground contact side diagonal edge (e5) extending in a region protruding from the tire equator (CL) in a different direction from one of the pair of front ground contact side diagonal edges (e3, e4) and connecting one of the pair of diagonal edges of the front ground contact side (e3, e4) and the axial edge of the rear ground contact side (e2), and wherein a plurality of shoulder blocks (52) are defined on a shoulder side of the tread portion (1) by the lug grooves (20, 30) and the narrow circumferential grooves (40), and shallow grooves (60) having at least one bending point are formed in road contact surfaces of each of the center blocks (51) and each of the shoulder blocks (52).

Images