JP6019693B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve uneven wear resistance and traction performance.

  The conventional pneumatic tire employs a configuration that suppresses the heel and toe wear of the block by forming the bottom upper portion in the lug groove of the block row and reinforcing the block rigidity. Further, in such a configuration, the traction performance of the tire (braking / driving performance on a wet road) can be ensured by dividing the block and the bottom upper portion with sipes. As a pneumatic tire employing such a configuration, a technique described in Patent Document 1 is known.

JP 2005-7919 A

  An object of the present invention is to provide a pneumatic tire capable of improving uneven wear resistance and traction performance.

In order to achieve the above object, a pneumatic tire according to the present invention includes a plurality of circumferential main grooves extending in the tire circumferential direction, a plurality of lug grooves extending in the tire width direction, the circumferential main groove, and A pneumatic tire comprising at least one row of land portions having a plurality of blocks partitioned by the lug grooves, wherein the left and right blocks partitioned by the lug grooves are recessed in an edge portion on the lug groove side. Each of the lug grooves has a bottom upper part separated from the left and right blocks, and the bottom upper part is inserted and disposed in each of the left and right recesses , and the tread surface and the bottom upper part of the block The step G with respect to the top surface has a relationship of 0.1 ≦ G / H ≦ 0.7 with respect to the groove depth H of the lug groove .

  In the pneumatic tire according to the present invention, when the block is deformed at the time of tire contact, the adjacent block and the bottom upper portion of the lug groove mesh with each other and support each other. Thereby, block rigidity is reinforced and there exists an advantage which the uneven wear-proof performance of a tire improves. Moreover, since the bottom upper part is inserted and arrange | positioned at a recessed part, a block and a bottom upper part can mesh | engage in the tire circumferential direction and the tire width direction in both directions. Accordingly, there is an advantage that the block rigidity is reinforced in both the tire circumferential direction and the tire width direction, and the traction performance of the tire (braking / driving performance and skid resistance on a wet road) is improved.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view showing a tread surface of the pneumatic tire depicted in FIG. 1. FIG. 3 is an enlarged plan view showing the land portion shown in FIG. FIG. 4 is a cross-sectional view taken along line AA showing the land portion shown in FIG. 3. FIG. 5 is a cross-sectional view taken along the line B-B showing the land portion shown in FIG. 3. FIG. 6 is an explanatory diagram illustrating a modification of the land portion illustrated in FIG. 3. FIG. 7 is an explanatory diagram illustrating a modification of the land portion illustrated in FIG. 3. FIG. 8 is an explanatory view showing a modification of the land portion shown in FIG. FIG. 9 is an explanatory view showing a modification of the land portion shown in FIG. FIG. 10 is an explanatory view showing a modification of the land portion shown in FIG. FIG. 11 is an explanatory diagram illustrating a modification of the land portion illustrated in FIG. 3. FIG. 12 is an explanatory diagram illustrating a modification of the land portion illustrated in FIG. 3. FIG. 13 is an explanatory diagram illustrating a modification of the land portion illustrated in FIG. 3. FIG. 14 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 15 is an explanatory view showing a land portion of a conventional pneumatic tire.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire 1 according to an embodiment of the present invention. FIG. 1 shows a heavy-duty radial tire mounted on a truck, a bus, etc. as an example of the pneumatic tire 1. Reference sign CL is a tire equator plane.

  The pneumatic tire 1 includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair. Bead rubbers 17 and 17 (see FIG. 1).

  The pair of bead cores 11 and 11 has an annular structure and constitutes the core of the left and right bead portions. The pair of bead fillers 12 and 12 includes a lower filler 121 and an upper filler 122, which are disposed on the tire radial direction outer periphery of the pair of bead cores 11 and 11, respectively, to reinforce the bead portion.

  The carcass layer 13 has a single-layer structure and is bridged in a toroidal shape between the left and right bead cores 11 and 11 to constitute a tire skeleton. Further, both ends of the carcass layer 13 are wound and locked from the inner side in the tire width direction to the outer side in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, nylon, polyester, rayon, etc.) with a coating rubber and rolling them, and has an absolute value of 85 [deg] or more and 95. [Deg] The following carcass angle (inclination angle in the fiber direction of the carcass cord with respect to the tire circumferential direction).

  The belt layer 14 is formed by laminating a plurality of belt plies 141 to 143, and is arranged around the outer periphery of the carcass layer 13. These belt plies 141 to 143 include, for example, a high-angle belt 141 and a pair of cross belts 142 and 143. Each belt ply 141 to 143 is formed by rolling a plurality of belt cords made of steel or organic fiber material with a coat rubber and rolling the belt cord, and a predetermined belt angle (inclination of the belt cord in the fiber direction with respect to the tire circumferential direction). Corner).

  FIG. 2 is a plan view showing a tread surface of the pneumatic tire 1 shown in FIG. 1.

  The pneumatic tire 1 includes five circumferential main grooves 2 extending in the tire circumferential direction, six rows of land portions 3 defined by the circumferential main grooves 2, and a tire width direction. A plurality of lug grooves 4 are provided in the tread portion (see FIG. 2).

  For example, in the configuration of FIG. 2, the five circumferential main grooves 2 are arranged symmetrically about the tire equatorial plane CL, and four rows of center land portions 3 and a pair of left and right shoulder land portions 3 are partitioned. ing. All the land portions 3 have a plurality of lug grooves 4 respectively. Further, these lug grooves 4 have an open structure that penetrates the land portion 3 in the tire width direction, and are arranged at predetermined intervals in the tire circumferential direction. Thereby, all the land parts 3 are divided into the some block 31, and the block pattern is formed.

  In addition, the circumferential direction main groove means the circumferential direction groove | channel which has a groove width of 5 [mm] or more. The lug groove refers to a lateral groove having a groove width of 2 [mm] or more.

[Bottom upper part of lug groove]
FIG. 3 is an enlarged plan view showing the land portion 3 shown in FIG. 4 and 5 are an AA sectional view (FIG. 4) and a BB sectional view (FIG. 5) showing the land portion 3 shown in FIG. In these drawings, FIG. 3 shows a block row constituting one row of land portions 3 arranged in the tire circumferential direction. 4 and 5 show a tire circumferential direction sectional view (FIG. 4) and a groove length direction sectional view (FIG. 5) on the bottom upper portion 41 of the lug groove 4.

  As shown in FIG. 3, in this pneumatic tire 1, the left and right blocks 31, 31 defined in the lug groove 4 have recesses 32 at the edge part on the lug groove 4 side. In addition, the lug groove 4 has a bottom upper portion 41 that raises the lug groove 4 to the bottom. The bottom upper portion 41 is separated from the left and right blocks 31 and 31 partitioned by the lug groove 4 and is inserted (bite in) into the recesses 32 and 32 of the left and right blocks 31 and 31, respectively. Therefore, a pair of blocks 31, 31 adjacent to each other in the tire circumferential direction and a bottom upper portion 41 of the lug groove 4 that partitions these blocks 31, 31 are arranged in the tire circumferential direction in the recesses 32, 32 of the blocks 31, 31. They are arranged so as to wrap in the tire width direction.

  For example, in the configuration of FIG. 3, the lug groove 4 is an inclined groove that is inclined with respect to the tire width direction in plan view of the tread, and substantially rhombic blocks 31 and 31 are partitioned. Further, the blocks 31, 31 adjacent to each other in the tire circumferential direction with the lug groove 4 interposed therebetween have a recess 32 at the center part of the edge part on the lug groove 4 side. In other words, the recesses 32 are respectively formed in the left and right groove walls of the lug groove 4. Moreover, these recessed parts 32 and 32 have a rectangular shape or a parallelogram shape in a tread plan view, and are disposed to face each other with the lug groove 4 interposed therebetween.

  Moreover, the lug groove 4 has the bottom upper part 41 in the center part of the groove length direction. The bottom upper portion 41 is a convex portion raised like a block from the groove bottom, and is separated from the left and right groove walls of the lug groove 4. Further, the bottom upper portion 41 has a rectangular shape or a parallelogram shape in a tread plan view, and is arranged by inserting both end portions in the tire circumferential direction into the left and right concave portions 32 and 32. Further, the inner peripheral surface of the recess 32 and the end shape of the bottom upper portion 41 have substantially the same shape, so that they are arranged with a certain gap S therebetween.

  A gap S between the recess 32 and the bottom upper portion 41 is a sipe or a narrow groove, and has a predetermined width Ws and depth Hs. Specifically, the width Ws of the gap S is in the range of 0.3 [mm] ≦ Ws ≦ 3.0 [mm]. As described above, the concave portion 32 and the bottom upper portion 41 are arranged close to each other with a predetermined gap S, so that the concave portion 32 and the bottom upper portion 41 can be engaged with each other and supported when the block 31 is deformed.

  Further, the depth Hs of the gap S (see FIG. 4) based on the tread surface of the block 31 and the groove depth H of the lug groove 4 (see FIGS. 4 and 5) are 0.5 ≦ Hs / H ≦ 1.0 relationship. Thereby, the separation state of the concave portion 32 and the bottom upper portion 41 is ensured until the end of wear. For example, in the configuration of FIGS. 3 to 5, the gap S has a constant width Ws and a constant depth Hs all around the recess 32. Further, the depth Hs of the gap S and the groove depth H of the lug groove 4 are equal (Hs / H = 1.0).

  The width Ws of the gap S is measured as a no-load state while applying a specified internal pressure by mounting the tire on a specified rim. Further, the groove depth H of the lug groove 4 is measured on the basis of the maximum groove depth position of the lug groove 4.

  Here, the prescribed rim refers to “applied rim” prescribed in JATMA, “Design Rim” prescribed in TRA, or “Measuring Rim” prescribed in ETRTO. The specified internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is air pressure 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

  Further, the step G (see FIG. 5) between the tread surface of the block 31 and the top surface of the bottom upper portion 41 has a relationship of 0.1 ≦ G / H ≦ 0.7 with respect to the groove depth H of the lug groove 4. . The ratio G / H is preferably in the range of 0.3 ≦ G / H ≦ 0.7. Accordingly, the top surface of the bottom upper portion 41 is arranged offset from the tread surface of the block 31 toward the groove bottom side. The height of the bottom upper portion 41 is a difference H−G between the step G of the bottom upper portion 41 and the groove depth H of the lug groove 4. 3 to 5, the tread surface of the block 31 and the top surface of the bottom upper portion 41 are parallel, and the bottom upper portion 41 has a flat top surface. For this reason, the bottom upper part 41 has a constant step G over the entire top surface.

  Further, the lap width X in the tire circumferential direction between the recess 32 and the bottom upper portion 41 has a relationship of 0.1 ≦ X / L ≦ 0.5 with respect to the circumferential length L of the block 31 (see FIG. 3). ). Further, the ratio X / L is preferably in the range of 0.1 ≦ X / L ≦ 0.3. The wrap width X is preferably in the range of 0.5 [mm] to 15 [mm].

  The lap width X is measured as an average value of the width in the tire circumferential direction of the region where the concave portion 32 and the bottom upper portion 41 overlap in a projection view in the tire width direction. In the configuration of FIG. 3, since the concave portion 32 and the bottom upper portion 41 have a rectangular shape in a tread plan view, the wrap width X is constant in the groove length direction of the lug groove 4. Moreover, since the recessed part 32 and the bottom upper part 41 have a uniform cross section in the groove depth direction of the lug groove 4, the lap width X is constant in the groove depth direction of the lug groove 4 (FIGS. 4 and 5). reference).

  Further, the width W1 of the bottom upper portion 41 and the width W2 of the block 31 have a relationship of 0.3 ≦ W1 / W2 ≦ 0.8 (see FIG. 3). The ratio W1 / W2 is preferably in the range of 0.3 ≦ W1 / W2 ≦ 0.5.

  Further, the width W2 of the block 31 and the widths W3 and W4 from the maximum width position of the recess 32 to the left and right edge portions of the block 31 satisfy the relationship of 0.1 ≦ W3 / W2 and 0.1 ≦ W4 / W2. Have. Therefore, the recessed part 32 is arrange | positioned in the center part (middle of the lug groove 4) of the tire width direction of the block 31. FIG. The upper limits of the ratios W3 / W2 and W4 / W2 are restricted by the relationship between the ratio W1 / W2 and the width Ws of the gap S.

  In addition, all said width W1-W4 is measured as a dimension of a tire width direction. Further, the width W <b> 1 is measured as the maximum value in the meshing region between the concave portion 32 and the bottom upper portion 41. The widths W2 to W4 are measured as the width in the tire width direction of the edge portion of the block 31 on the lug groove 4 side.

  In this pneumatic tire 1, when the block 31 is deformed at the time of tire contact, the adjacent blocks 31, 31 and the bottom upper portion 41 of the lug groove 4 are engaged with each other and supported. Thereby, block rigidity is reinforced and the uneven wear-proof performance of a tire improves. Moreover, since the bottom upper part 41 is inserted and arrange | positioned at the recessed part 32, the block 31 and the bottom upper part 41 can mesh | engage in the tire circumferential direction and the both directions of a tire width direction. As a result, the block rigidity is reinforced in both the tire circumferential direction and the tire width direction, and the traction performance of the tire (braking and driving performance and skid resistance on a wet road) is improved.

  In the configuration of FIG. 2, all land portions 3 are block rows having blocks 31 and lug grooves 4. However, the present invention is not limited to this, and some of the land portions 3 may be ribs continuous in the tire circumferential direction (not shown).

  In the configuration of FIG. 2, all the land portions 3 in the center region have a meshing structure with the concave portion 32 of the block 31 and the bottom upper portion 41 of the lug groove 4. On the other hand, the land portions 3 in the left and right shoulder regions do not have such a meshing structure. However, the present invention is not limited to this, and the land portions 3 in the left and right shoulder regions may have a meshing structure between the concave portion 32 of the block 31 and the bottom upper portion 41 of the lug groove 4 (not shown). The center region means a region on the inner side in the tire width direction from the left and right outermost circumferential main grooves 2 (the left and right circumferential main grooves 2, 2 on the outermost side in the tire width direction), and the shoulder region is It refers to the area outside the center area in the tire width direction.

[Modification]
6-8 is explanatory drawing which shows the modification of the land part 3 described in FIG. These drawings show a pair of blocks 31 and 31 and a bottom upper portion 41 of the lug groove 4 in one row of land portions 3.

  In the configuration of FIG. 3, the concave portion 32 of the block 31 and the bottom upper portion 41 of the lug groove 4 have a rectangular shape that meshes with each other in a tread plan view. However, the present invention is not limited to this, and the concave portion 32 of the block 31 and the bottom upper portion 41 of the lug groove 4 may have any meshing structure. Examples of the meshing structure include the following structures.

  For example, in the configuration of FIG. 6, the concave portion 32 of the block 31 has an arc shape in the plan view of the tread, and the bottom upper portion 41 of the lug groove 4 has an elliptical shape. The bottom upper portion 41 of the groove 4 is disposed so as to be able to mesh with a predetermined gap S therebetween.

  In the configuration of FIG. 7, the concave portion 32 of the block 31 has a triangular shape in the plan view of the tread, and the bottom upper portion 41 of the lug groove 4 has a hexagonal shape. The bottom upper portion 41 of the groove 4 is disposed so as to be able to mesh with a predetermined gap S therebetween.

  Further, in the configuration of FIG. 8, the concave portion 32 of the block 31 has an arc shape in which the opening on the lug groove 4 side is narrowed in plan view of the tread, and the bottom upper portion 41 of the lug groove 4 has circular ends. It has a gourd shape with connected parts. And it arrange | positions so that it may mesh | engage through the predetermined clearance gap S so that the edge part of the bottom upper part 41 may be engage | inserted by the recessed part 32 of the block 31. FIG.

  FIG. 9 and FIG. 10 are explanatory diagrams showing modifications of the land portion 3 shown in FIG. These drawings show sectional views in the tire circumferential direction of a pair of blocks 31 and 31 and a bottom upper portion 41 of the lug groove 4 in one row of land portions 3.

  In the configuration of FIG. 4, the concave portion 32 of the block 31 and the bottom upper portion 41 of the lug groove 4 have a uniform cross-sectional shape in the groove depth direction of the lug groove 4. Such a configuration is preferable in that the concave portion 32 and the bottom upper portion 41 using a molding die can be easily processed.

  On the other hand, in the configuration of FIGS. 9 and 10, the concave portion 32 of the block 31 and the bottom upper portion 41 of the lug groove 4 have a shape that is widened in the groove depth direction of the lug groove 4. . Such a configuration is preferable in that the area of the bottom upper portion 41 is increased as the wear progresses and the rigidity of the bottom upper portion 41 is increased, so that the area where the blocks 31 and 41 are in contact with each other is increased and the supporting effect is amplified. Note that, as described above, the lap width X is measured as an average value of the width in the tire circumferential direction in the region where the recess 32 and the bottom upper portion 41 overlap in a projection view in the tire width direction.

  FIG. 11 and FIG. 12 are explanatory views showing a modification of the land portion 3 shown in FIG. These drawings show a transparent perspective view of one side wall surface of the three-dimensional sipe.

  In the configuration of FIG. 3, the gap S between the concave portion 32 of the block 31 and the bottom upper portion 41 of the lug groove 4 is constituted by a two-dimensional sipe. The two-dimensional sipe refers to a sipe having a straight sipe wall surface in a cross-sectional view perpendicular to the sipe length direction.

  However, the present invention is not limited thereto, and the gap S between the concave portion 32 of the block 31 and the bottom upper portion 41 of the lug groove 4 may be constituted by a three-dimensional sipe. The three-dimensional sipe is a sipe having a sipe wall surface that is bent in the sipe width direction in a cross-sectional view perpendicular to the sipe length direction. The three-dimensional sipe has an action of reinforcing the rigidity of the land portion because the meshing force of the opposing sipe wall surfaces is stronger than that of the two-dimensional sipe.

  Examples of the configuration in which the gap S is formed of a three-dimensional sipe include the configurations in FIGS. 11 and 12. In the configuration of FIG. 10 as well, it can be said that the gap S is composed of a three-dimensional sipe.

  The three-dimensional sipe shown in FIG. 11 has an opening that has a linear shape or an arc shape in plan view of the tread surface of the land. In addition, the three-dimensional sipe has a wave-like shape that repeats bending or bending from one end to the other while gradually increasing the swing width as the sipe depth increases from this opening to at least 80% wear position of the land. Have. Also, at a predetermined sipe depth position, a perpendicular line is drawn from each end of the three-dimensional sipe to the center line passing through the center of the wavy shape of the three-dimensional sipe, and the distance between the legs of these perpendicular lines is sipe. The length is L (not shown). At this time, the sipe length L decreases as the sipe depth increases. In addition, the peripheral length (actual length) of the sipe on the tread of the land portion is M0 [mm], the sipe length L at the 80% wear position is L80 [mm], and the sipe length at the 80% wear position is L80 [mm]. The peripheral length is M80 [mm] (not shown). At this time, the ratio L80 / M0 and the ratio M80 / M0 satisfy the conditions of 0.85 ≦ L80 / M0 ≦ 0.90 and 1.0 ≦ M80 / M0 ≦ 1.15. As such a three-dimensional sipe, for example, a technique described in JP 2006-56502 A is known.

  Further, the three-dimensional sipe shown in FIG. 12 has a first offset portion projecting to one side in the sipe width direction and a second offset projecting to the other side in the sipe width direction at a position on the inner side in the tire radial direction from the first offset portion. Part. Further, the sipe length L1 (not shown) when the tire is new and the sipe length L2 (not shown) when 80% wear is substantially the same (0.95 ≦ L2 / L1 ≦ 1.05). ). Further, the sipe peripheral length M1 (not shown) when the tire is new and the sipe peripheral length M2 (not shown) when worn 80% are 1.10 ≦ M2 / M1 ≦ 1.50. Have a relationship. Moreover, the planar shape of the sipe at the time of 80% wear has a parallel portion with respect to the planar shape of the sipe in a new tire. Further, the total length P2 (not shown) of the parallel portion and the sipe length L1 when the tire is new have a relationship of 0.20 ≦ P2 / L1 ≦ 0.80. As such a three-dimensional sipe, for example, a technique described in Japanese Patent Application Laid-Open No. 2009-255688 is known.

  FIG. 13 is an explanatory view showing a modification of the land portion 3 shown in FIG.

  In the configuration of FIG. 3, the concave portions 32 of the blocks 31 and the bottom upper portions 41 of the lug grooves 4 are arranged in a row in the tire circumferential direction in one row of land portions 3. However, the present invention is not limited to this, and the plurality of bottom upper portions 41 may be arranged with their positions shifted from each other in the tire width direction (see FIG. 13). For example, in the configuration of FIG. 13, the plurality of bottom upper portions 41 are arranged in a staggered manner in the tire circumferential direction while shifting positions in the tire width direction.

[effect]
As described above, the pneumatic tire 1 includes the plurality of circumferential main grooves 2 extending in the tire circumferential direction, the plurality of lug grooves 4 extending in the tire width direction, the circumferential main groove 2 and the lugs. And at least one row of land portions 3 having a plurality of blocks 31 partitioned into grooves 4 (see FIG. 2). Moreover, the left and right blocks 31 and 31 defined in the lug groove 4 have recesses 32 and 32 at the edge part on the lug groove 4 side, respectively (see FIG. 3). Also, the lug groove 4 has a bottom upper portion 41 separated from the left and right blocks 31, 31. Further, the bottom upper portion 41 is inserted and disposed in the left and right concave portions 32, 32, respectively.

  In such a configuration, when the block 31 is deformed at the time of tire contact, the adjacent blocks 31 and 31 and the bottom upper portion 41 of the lug groove 4 mesh with each other and support each other. Thereby, block rigidity is reinforced and there exists an advantage which the uneven wear-proof performance of a tire improves. Moreover, since the bottom upper part 41 is inserted and arrange | positioned at the recessed part 32, the block 31 and the bottom upper part 41 can mesh | engage in both directions of a tire circumferential direction and a tire width direction. Accordingly, there is an advantage that the block rigidity is reinforced in both the tire circumferential direction and the tire width direction, and the traction performance of the tire (braking / driving performance and skid resistance on a wet road) is improved. For example, at the time of braking / driving, the block 31 and the bottom upper portion 41 mesh with each other in the tire circumferential direction, so that the block rigidity in the tire circumferential direction is ensured and the braking / driving performance of the tire is improved. Further, when the vehicle is turning, the block 31 and the bottom upper portion 41 are engaged with each other in the tire width direction, so that the block rigidity in the tire width direction is secured and the skid performance of the tire is improved.

  In this pneumatic tire 1, the width Ws of the gap S between the recess 32 and the bottom upper portion 41 is in the range of 0.3 [mm] ≦ Ws ≦ 3.0 [mm] (see FIG. 3). In such a configuration, the width Ws of the gap S is optimized, so that when the block 31 is deformed when the tire is in contact with the ground, the engagement between the concave portion 32 and the bottom upper portion 41 is appropriately ensured. Thereby, there exists an advantage by which the rigidity of the block 31 is ensured appropriately.

  In the pneumatic tire 1, the depth Hs of the gap S between the recess 32 and the bottom upper portion 41 with respect to the tread surface of the block 31 is 0.5 ≦ Hs / with respect to the groove depth H of the lug groove 4. It has a relationship of H ≦ 1.0 (see FIG. 4). Thereby, there exists an advantage by which the isolation | separation state of the recessed part 32 and the bottom upper part 41 is ensured until the last stage of wear.

  Further, in the pneumatic tire 1, the step G between the tread surface of the block 31 and the top surface of the bottom upper portion 41 has a relationship of 0.1 ≦ G / H ≦ 0.7 with respect to the groove depth H of the lug groove 4. (See FIG. 5). In such a configuration, the positional relationship between the tread surface of the block 31 and the top surface of the bottom upper portion 41 is optimized, so that the edge component on the lug groove 4 side of the block 31 is ensured. Thereby, there exists an advantage by which the braking / driving performance of a tire is ensured.

  In the pneumatic tire 1, the lap width X in the tire circumferential direction between the recess 32 and the bottom upper portion 41 is 0.1 ≦ X / L ≦ 0.5 with respect to the circumferential length L of the block 31. There is a relationship (see FIG. 3). In such a configuration, there is an advantage that when the block 31 is deformed in the tire width direction, the engagement between the block 31 and the bottom upper portion 41 is appropriately ensured.

  Further, in the pneumatic tire 1, the width W1 of the bottom upper portion 41 and the width W2 of the block 31 have a relationship of 0.3 ≦ W1 / W2 ≦ 0.8 (see FIG. 3). In such a configuration, since the width W1 of the bottom upper portion 41 is appropriately secured, there is an advantage that the rigidity of the bottom upper portion 41 is properly secured and the engagement between the concave portion 32 and the bottom upper portion 41 is appropriately secured.

  In particular, in such a configuration, the bottom upper portion 41 has a structure in which the left and right blocks 31, 31 are separated from each other with a gap S therebetween, and is smaller than the left and right blocks 31, 31 (see FIGS. 3 to 5). ). Then, the bottom upper part 41 has lower rigidity than the left and right blocks 31, 31, and easily slips when the tire contacts the ground. For this reason, as the wear progresses, the bottom upper portion 41 wears faster than the left and right blocks 31, 31, and the positional relationship (step G) between the top surface of the bottom upper portion 41 and the tread surface of the block 31 is maintained. Accordingly, there is an advantage that the edge component on the lug groove 4 side of the block 31 is secured from the time when the tire is new to the end of wear, and the braking / driving performance of the tire is secured.

  In the pneumatic tire 1, the width W2 of the block 31 and the widths W3 and W4 from the recess 32 to the left and right edge portions of the block 31 are 0.1 ≦ W3 / W2 and 0.1 ≦ W4 / W2. (See FIG. 3). In such a configuration, the widths W3 and W4 from the maximum width position of the concave portion 32 to the left and right edge portions of the block 31 are ensured, whereby the block rigidity on the left and right sides of the concave portion 32 is ensured. Thereby, when the bottom upper part 41 and the block 31 mesh in the tire width direction, there exists an advantage which these support appropriately.

  Moreover, in this pneumatic tire 1, the clearance gap S between the recessed part 32 and the bottom upper part 41 consists of a three-dimensional sipe (refer FIGS. 10-12). In such a configuration, there is an advantage that the reinforcing action of the block rigidity by the bottom upper portion 41 is improved as compared with the configuration in which the gap S is formed of a two-dimensional sipe.

  FIG. 14 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 15 is an explanatory view showing a land portion of a conventional pneumatic tire.

  In this performance test, evaluations on (1) uneven wear resistance, (2) braking / driving performance, and (3) skid resistance were performed on a plurality of different pneumatic tires (see FIG. 14). In this performance test, a pneumatic tire having a tire size of 275 / 80R22.5 is assembled to an applicable rim specified by JATMA, and the highest pneumatic pressure and maximum load specified by JATMA are applied to the pneumatic tire. In addition, pneumatic tires are attached to all wheels of a 6 × 2 truck that is a test vehicle.

  (1) In the evaluation on uneven wear resistance performance, after the test vehicle travels 50,000 [km] on a general pavement, the uneven wear generated in the block is observed and index evaluation is performed. This evaluation is based on the conventional example as the standard (100), and the larger the index value, the better. If the numerical value is 103 or more, it is recognized that there is an advantage.

  In the evaluation on (2) braking / driving performance and (3) skid resistance, the test vehicle runs on the specified wet test road, and a specialized driver performs sensory evaluation on braking / driving and skidding. This evaluation is based on the conventional example as the standard (100), and the larger the index value, the better. If the numerical value is 103 or more, it is recognized that there is an advantage.

  The pneumatic tires 1 of Examples 1 to 10 have the configurations shown in FIGS. The pneumatic tire of Example 11 is the same as the pneumatic tire 1 of Example 1, but the gap S is formed of the three-dimensional sipe shown in FIG. Moreover, in the pneumatic tire 1 of Example 1, W1 = 14.5 [mm], W2 = 35.5 [mm], W3 = W4 = 9.8 [mm], X = 4.0 [mm], L = 42.5 [mm], H = Hs = 20.0 [mm], and G = 5.0 [mm].

  The conventional pneumatic tire has the configuration shown in FIG. 15, and the block and the bottom upper portion are not wrapped in the tire circumferential direction.

  As shown in the test results, it can be seen that in the pneumatic tires 1 of Examples 1 to 11, the uneven wear resistance is improved (maintained), and the braking / driving performance and the skid resistance are improved.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 2 circumferential main groove, 3 land part, 31 block, 32 recessed part, 4 lug groove, 41 bottom upper part, 11 bead core, 12 bead filler, 121 lower filler, 122 upper filler, 13 carcass layer, 14 belt Layer, 141 high angle belt, 142, 143 cross belt, 15 tread rubber, 16 sidewall rubber, 17 bead rubber

Claims (6)

At least one row having a plurality of circumferential main grooves extending in the tire circumferential direction, a plurality of lug grooves extending in the tire width direction, and a plurality of blocks partitioned by the circumferential main grooves and the lug grooves A pneumatic tire comprising a land portion,
The left and right blocks partitioned into the lug grooves each have a recess at the edge portion on the lug groove side, the lug grooves have bottom tops separated from the left and right blocks, and the bottom tops Inserted into the left and right recesses, respectively , and
The step G between the tread surface of the block and the top surface of the bottom upper portion has a relationship of 0.1 ≦ G / H ≦ 0.7 with respect to the groove depth H of the lug groove. tire.   The pneumatic tire according to claim 1, wherein a width Ws of a gap between the concave portion and the bottom upper portion is in a range of 0.3 [mm] ≦ Ws ≦ 3.0 [mm]. Tire circumferential direction of the wrap width X between the bottom upper and the recess, the circumferential direction length L of the block, to claim 1 or 2 having the relationship 0.1 ≦ X / L ≦ 0.5 The described pneumatic tire. The pneumatic tire according to any one of claims 1 to 3 , wherein a width W1 of the bottom upper portion and a width W2 of the block have a relationship of 0.3 ≦ W1 / W2 ≦ 0.8. The width W2 of the block and the widths W3 and W4 from the maximum width position of the concave portion to the left and right edge portions of the block have a relationship of 0.1 ≦ W3 / W2 and 0.1 ≦ W4 / W2. Item 5. The pneumatic tire according to any one of Items 1 to 4 . The pneumatic tire according to any one of claims 1 to 5 , wherein a gap between the concave portion and the bottom upper portion is formed of a three-dimensional sipe.

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