JP6126572B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy duty pneumatic tire capable of exhibiting excellent performance on snow.

  For example, Patent Document 1 below proposes a heavy duty pneumatic tire in which a plurality of blocks are formed in a tread portion. Each block is divided into three parts, a pair of outer pieces and a central piece between them, by two divided sipes crossing the blocks in the tire axial direction.

  The outer piece of the block of Patent Document 1 has a protrusion protruding in a step shape on one side in the tire axial direction in order to strongly press and harden the snow in the longitudinal groove.

  However, in the outer piece of the block of Patent Document 1, the edge facing the longitudinal groove on the opposite side of the protrusion extends linearly along the tire circumferential direction. The outer piece having such an edge tended to have a small deflection toward the protruding portion at the time of grounding. Therefore, there has been room for further improvement in order to more strongly compress the snow in the flutes.

JP 2005-280457 A

  The present invention has been devised in view of the actual situation as described above, and its main purpose is to provide a heavy duty pneumatic tire capable of exhibiting excellent on-snow performance on the basis of improving the shape of the block. Yes.

  The present invention is a heavy duty pneumatic tire having a plurality of blocks divided in a tread portion by vertical grooves extending in the tire circumferential direction and horizontal grooves extending in the tire axial direction, wherein at least one of the blocks is A split sipe consisting of only two crossing the block in the tire axial direction is divided into a pair of outer pieces and a central piece between them, and the central piece has a pair of vertical edges facing the vertical grooves. The first outer piece, which is one of the outer pieces, has a protrusion protruding stepwise from the vertical edge of the central piece to the outside of the block on one longitudinal groove side in the tire axial direction. And the other longitudinal groove side in the tire axial direction has a non-projecting portion that does not protrude from the vertical edge of the central piece to the outside of the block, and the non-projecting portion passes through the divided sipes. Vertical It is characterized in that it includes a first edge which is inclined in a direction intersecting the Tsu-di.

  In the heavy duty pneumatic tire of the present invention, it is preferable that the protrusion includes a second edge inclined in a direction intersecting with the vertical edge of the center piece via the divided sipe.

  In the heavy duty pneumatic tire of the present invention, it is preferable that the protrusion includes a third edge that is continuous with the second edge and is inclined in the same direction as the vertical edge.

  In the heavy duty pneumatic tire of the present invention, the second outer piece, which is the other of the outer pieces, is stepped from the vertical edge of the central piece to the outside of the block on the other longitudinal groove side in the tire axial direction. It is desirable to have a protruding protrusion and a non-protruding portion that does not protrude outside the block from the vertical edge of the central piece on the one longitudinal groove side in the tire axial direction.

  In the heavy-duty pneumatic tire of the present invention, the front tread portion has a block pair in which two blocks are adjacent to each other through the vertical groove, and the protrusions of the block pair have the vertical groove through the vertical groove. It is desirable to face at least partly.

  In the heavy-duty pneumatic tire of the present invention, the vertical edge is linear, the lateral groove facing the first outer piece has a tie bar having a raised groove bottom, and the tie bar extends along the lateral groove. It is desirable to extend over the extension line of the vertical edge on one side of the center piece in the tire axial direction.

  In the heavy duty pneumatic tire of the present invention, the outer piece has a linear lateral edge facing the lateral groove, and the protrusion protrudes from the extension line, and the extension line and the lateral edge The tie bar length in the tire axial direction from the intersection point to the outer end on one side in the tire axial direction of the tie bar is the maximum width of the protrusion in the tire axial direction from the intersection point to the outer end in the tire axial direction of the protrusion. It is desirable that it is 0.2 to 0.8 times.

  The heavy-duty pneumatic tire of the present invention has a plurality of blocks in the tread portion that are divided by a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire axial direction. At least one of the blocks is divided into three parts, that is, a pair of outer pieces and a central piece between them by a split sipe composed of only two that cross the block in the tire axial direction.

  The central piece has a pair of vertical edges facing the vertical grooves. The first outer piece, which is one of the outer pieces, has a protrusion that protrudes stepwise from the vertical edge of the central piece to the outside of the block on one longitudinal groove side in the tire axial direction. Such a protrusion of the first outer piece strongly presses and hardens the snow in the longitudinal groove and can exert a large snow column shear force.

  The first outer piece has a non-projecting portion that does not protrude outward from the vertical edge of the central piece on the other vertical groove side in the tire axial direction. Such a non-protruding portion of the first outer piece is useful for maintaining the volume of the longitudinal groove and thus improving the wet performance.

  The non-projecting portion of the first outer piece includes a first edge that is inclined in a direction intersecting with the vertical edge via the split sipe. The first edge of the first outer piece and the vertical edge of the central piece together with the edge of the divided sipe form a corner portion that protrudes toward the vertical groove, and exhibits a large edge effect on, for example, a snowy road surface.

  In addition, the non-projecting portion having the first edge as described above serves to bend the first outer piece toward the projecting side due to the snow in the longitudinal groove or the reaction force of the ground contact surface. As a result, the protrusions can more strongly push the snow in the vertical grooves. On the other hand, as the first outer piece moves away from the ground contact surface, the bent first outer piece is restored, and the snow that has been compacted by the protrusion is quickly discharged to the outside of the tire. Therefore, the performance on snow is further enhanced.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is an enlarged view of the center land part of FIG. It is an enlarged view of the center block of FIG. FIG. 4 is a cross-sectional view of the divided sipe of FIG. FIG. 3 is a cross-sectional view of the tie bar in FIG. It is an enlarged view of the middle land part of FIG. It is an enlarged view of the inner side shoulder land part and outer side shoulder land part of FIG. It is an expanded view of the tread part of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a heavy duty pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. The tire 1 of the present embodiment is, for example, a winter tire, and the tread portion 2 is divided into a plurality of vertical grooves 3 extending in the tire circumferential direction and a plurality of horizontal grooves 7 extending in the tire axial direction. A plurality of blocks 8 are formed.

  The longitudinal groove 3 of the present embodiment includes, for example, a center main groove 4, a shoulder main groove 5, and a shoulder sub groove 6.

  The center main groove 4 is provided, for example, on the tire equator C side most. A pair of center main grooves 4 are provided on both sides of the tire equator C, for example. The center main groove 4 extends continuously in the tire circumferential direction.

  The shoulder main groove 5 is provided, for example, on the outer side in the tire axial direction of each center main groove 4. The shoulder main groove 5 extends continuously in the tire circumferential direction.

  The groove width W1 of the center main groove 4 and the groove width W2 of the shoulder main groove 5 are, for example, 3.0% to 8.0% of the tread ground contact width TW. The groove depth of the center main groove 4 and the shoulder main groove 5 is preferably 10 to 25 mm, for example.

  The tread contact width TW is a distance in the tire axial direction between the tread contact ends Te and Te of a normal tire 1 that is assembled to a normal rim (not shown) and filled with a normal internal pressure and is unloaded. is there.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “highest air pressure”, TRA is the table “TIRE LOAD LIMITS AT” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  The “tread contact end Te” is a contact position on the outermost side in the tire axial direction when the normal tire 1 is loaded with a normal load and contacted with a flat surface with a camber angle of 0 °.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “Maximum load capacity”, TRA is “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  The shoulder sub-groove 6 extends, for example, continuously in the tire circumferential direction on the tread ground contact Te side. The shoulder minor groove 6 is linear, for example.

  The shoulder sub-groove 6 has a groove width W3 that is smaller than the center main groove 4 and the shoulder main groove 5, for example. The groove width W3 of the shoulder sub-groove 6 is, for example, 0.10 to 0.15 times the groove width W2 of the shoulder main groove 5. Similarly, the shoulder sub-groove 6 has a groove depth smaller than that of the center main groove 4 and the shoulder main groove 5. The groove depth of the shoulder sub-groove 6 is preferably 5 to 13 mm, for example.

  The tread portion 2 is divided into, for example, a center land portion 10, a middle land portion 11, an inner shoulder land portion 12, and an outer shoulder land portion 13 by a center main groove 4, a shoulder main groove 5, and a shoulder sub groove 6. Has been.

  FIG. 2 shows an enlarged view of the center land portion 10. As shown in FIG. 2, the center land portion 10 is provided between the pair of center main grooves 4 and 4. The center land portion 10 is divided into a plurality of center blocks 15 by a plurality of center lateral grooves 14.

  Each center lateral groove 14 communicates between the pair of center main grooves 4 and 4. Each center lateral groove 14 extends in a straight line, for example, and is inclined in the same direction.

  An angle θ1 of the center lateral groove 14 with respect to the tire axial direction is, for example, 3 to 7 °. The groove width W6 of the center lateral groove 14 is preferably 5 to 10 mm, for example.

  FIG. 3 shows an enlarged view of the center block 15. As shown in FIG. 3, the center block 15 is provided with two divided sipes 18 that cross the block in the tire axial direction.

  The divided sipe 18 extends along the center lateral groove 14, for example. For example, the divided sipes 18 of the present embodiment extend substantially parallel to each other. Each divided sipe 18 may extend at different angles with respect to the tire axial direction.

  4 shows a cross-sectional view taken along line AA of the divided sipe 18 of FIG. As shown in FIG. 4, the divided sipe 18 has a groove depth d1 of 5 to 10 mm, for example.

  The split sipe 18 includes, for example, a main body portion 34 extending in a tire radial direction except for the bottom portion, and an opening 35 having a step-like width increasing outside the main body portion 34 in the tire radial direction.

  The main body 34 extends, for example, in a wave shape in a tread plan view (see FIG. 3). The width W4 of the main body 34 is, for example, 0.3 to 1.0 mm. The depth d2 of the main body 34 is, for example, 4.0 to 9.5 mm.

  A width W5 of the opening 35 is, for example, 0.5 to 2.0 mm. The depth d3 of the opening 35 is, for example, 0.5 to 1.5 mm. The opening 35 of the present embodiment is formed, for example, by expanding the sipe width by the sipe walls 38 on both sides.

  The split sipe 18 having the main body 34 and the opening 35 effectively absorbs moisture on the road surface when traveling on ice, and exhibits excellent performance on ice.

  As shown in FIG. 3, the center block 15 is divided into three parts, that is, a pair of outer pieces 20 and a central piece 24 between them, by providing only the above-described two divided sipes 18.

  Each of the outer pieces 20 and the central piece 24 is formed as a plain block piece that is not provided with cuts such as sipes. Each of the outer pieces 20 and the central piece 24 as described above serves to suppress uneven wear of the block.

  The center piece 24 has, for example, a rectangular tread. As a desirable mode, central piece 24 of this embodiment has a tread of parallelogram shape as a whole, for example.

  The central piece 24 has a pair of vertical edges 36, 36 facing the center main groove 4 (shown in FIG. 2, the same applies hereinafter). Each vertical edge 36 is inclined in the same direction with respect to the tire axial direction and extends linearly, for example. As a desirable mode, in the present embodiment, the vertical edges 36 are provided in parallel to each other.

  The first outer piece 21 that is one of the outer pieces 20 has a protrusion 25 that protrudes stepwise from the vertical edge 36 of the central piece 24 to the outside of the block on one center main groove 4 side in the tire axial direction. ing. Such protrusions 25 can strongly press and harden the snow in the longitudinal grooves and exert a large snow column shear force.

  The first outer piece 21 has a non-protruding portion 28 that does not protrude outward from the vertical edge 36 of the central piece 24 on the other center main groove 4 side in the tire axial direction. Such a non-projecting portion 28 of the first outer piece 21 is useful for maintaining the volume of the center main groove 4 and thus improving the wet performance.

  In addition, the non-projecting portion 28 includes a first edge 29 that is inclined in a direction intersecting with the vertical edge 36 via the split sipe 18. The first edge 29 of the first outer piece 21 and the vertical edge 36 of the central piece 24 together with the edge of the divided sipe 18 form a corner portion 23 that protrudes toward the center main groove 4 side. Such a corner portion 23 digs deeply into the road surface when, for example, running on an icy road or a snowy road, and exerts a large frictional force by the edge.

  In addition, the non-projecting portion 28 having the first edge 29 as described above is useful for bending the first outer piece 21 toward the projecting portion 25 due to the snow in the longitudinal groove or the reaction force of the ground contact surface. Thereby, the protrusion 25 can press and harden the snow in the center main groove 4 more strongly. On the other hand, as the first outer piece 21 moves away from the ground contact surface, the bent first outer piece 21 is restored, and the snow that has been compacted by the protrusion 25 is quickly discharged to the outside of the tire. Therefore, snow does not remain in the groove, and the performance on snow is further enhanced.

  The protrusion 25 is, for example, a second edge 30 that inclines in a direction intersecting with the vertical edge 36 of the center piece 24 via the split sipe 18, and is connected to the second edge 30 and inclines in the same direction as the vertical edge 36. 3rd edge 31 is included. In such a protrusion 25, the second edge 30 pushes snow away from the snow in the longitudinal groove, and the third edge 31 strongly pushes the snow. Thereby, a hard snow column is formed.

  The protrusion 25 of the first outer piece 21 protrudes from the extension line 32 of the vertical edge 36 of the center piece 24. The maximum protrusion amount W7, which is the distance in the tire axial direction from the outer end 39 of the protrusion 25 to the extension line 32, is preferably 0.10 times the width W10 (shown in FIG. 2) of the center block 15 in the tire axial direction. As mentioned above, More preferably, it is 0.15 times or more, Preferably it is 0.25 times or less, More preferably, it is 0.20 times or less. Such a protrusion 25 balances wet performance and performance on snow in a well-balanced manner.

  The second outer piece 22, which is the other of the outer pieces 20, protrudes stepwise from the vertical edge 36 of the central piece 24 to the outside of the block on the other center main groove 4 side in the tire axial direction (right side in FIG. 3). A protrusion 25 is provided. Moreover, the second outer piece 22 has a non-projecting portion 28 that does not protrude outward from the vertical edge 36 of the central piece 24 on the side of one center main groove 4 in the tire axial direction (left side in FIG. 3). ing. Such 2nd outer piece 22 exhibits the effect similar to the 1st outer piece 21 mentioned above, and improves on-snow performance.

  In the center block 15 of the present embodiment, it is desirable that the maximum protrusion amount W7 of the protrusion 25 of the first outer piece 22 is the same as the maximum protrusion amount W8 of the protrusion 25 of the second outer piece 22. Such a block having the protrusions 25, 25 (hereinafter sometimes referred to as the first block 41) can suppress uneven wear of each outer piece 20.

  As shown in FIG. 2, it is desirable that the center lateral groove 14 facing the outer piece 20 is provided with a tie bar 37 having a raised groove bottom. Such a tie bar 37 is useful for suppressing excessive deformation of the block and improving wear resistance.

  FIG. 5 shows a cross-sectional view of the tie bar 37 of FIG. As shown in FIG. 5, the tie bar depth d5 from the tread surface 8s of the block to the upper surface 37s of the tie bar 37 is desirably 0.4 to 0.6 times the maximum groove depth d4 of the center lateral groove 14. Such a tie bar 37 is useful for enhancing wear resistance while maintaining on-snow performance and wet performance.

  As shown in FIG. 3, the tie bar 37 straddles the extension line 32 of the vertical edge 36 on one side of the central piece 24 in the tire axial direction. Such a tie bar 37 enhances the edge effect of the protrusion 25 and suppresses the damage.

  In order to further enhance the above effect, the tie bar length L1 in the tire axial direction is preferably 0.2 times or more, more preferably 0.4 times or more, and preferably 0.8 times the maximum protrusion width W11. Below, more preferably 0.6 times or less. The tie bar length L1 in the tire axial direction is the length of the tie bar 37 from the intersection 43 of the extension line 32 and the lateral edge 33 of the outer piece 20 to the outer end 37e on one side of the tie bar 37 in the tire axial direction. The maximum protrusion width W11 is the width of the protrusion 25 from the intersection 43 to the outer end 39 of the protrusion 25 in the tire axial direction.

  As shown in FIG. 2, the center land portion 10 is preferably provided with a plurality of the first blocks 41 described above in the tire circumferential direction. Thereby, the single flow of a tire is suppressed and straight running stability is improved.

  As a desirable mode, as for the center land part 10, it is desirable for the projection part 25 of each outer piece 20 adjacent via the center lateral groove 14 to be provided in the mutually same side of a tire axial direction, respectively. Thus, when traveling on snow, the adjacent protrusions 25, 25 can cooperate to strongly press and harden snow, and a large shear force on snow can be obtained. In addition, since the center lateral groove 14 is arranged between the outer pieces 20 and 20, the compressed snow is not held between the outer pieces 20 and 20, and the outer side of the tire is smoothly removed from the outside of the tire. To be discharged.

  FIG. 6 shows an enlarged view of the middle land portion 11 of FIG. As shown in FIG. 6, the middle land portion 11 is provided between the center main groove 4 and the shoulder main groove 5. The middle land portion 11 is a block row in which a plurality of middle blocks 45 divided by a plurality of middle lateral grooves 44 are arranged in the tire circumferential direction.

  The middle lateral groove 44 communicates, for example, between the center main groove 4 and the shoulder main groove 5. For example, the middle lateral groove 44 is inclined in the direction opposite to the center lateral groove 14 (shown in FIG. 2) with respect to the tire axial direction. Moreover, the middle lateral groove 44 is displaced in the tire circumferential direction with respect to the center lateral groove 14.

  The middle lateral groove 44 has a tie bar 37 with a raised groove bottom, like the central lateral groove 14. Such a tie bar 37 serves to suppress excessive deformation of the middle block 45.

  The middle block 45 has the same configuration as the above-described center block 15 (shown in FIG. 3). Of the components of the middle block 45, the components common to the center block 15 may be assigned the same reference numerals.

  As shown in FIG. 1, the middle block 45 of the present embodiment is adjacent to the above-described center block 15 via the center main groove 4 to form a block pair. In this case, it is desirable that the protrusion 25 of the middle block 45 and the protrusion 25 of the center block 15 face at least partly via the center main groove 4. As a result, the snow in the center main groove 4 is pressed against the protrusions 25 on both sides in the tire axial direction, and a hard snow column is formed.

  As shown in FIG. 6, the middle block 45 includes, for example, the first block 41 (shown in FIG. 3) and the second block 42 described above. The second block 42 is a block in which the maximum protrusion amount W7 and the maximum protrusion amount W8 are different. In the present embodiment, the first blocks 41 and the second blocks 42 are alternately provided in the tire circumferential direction. Thereby, the amount of deformation of each block in the tire axial direction is different, and clogging of snow into the longitudinal groove is suppressed.

  In the second block 42 of the present embodiment, for example, the maximum protrusion amount W7 of the first outer piece 21 is larger than the maximum protrusion amount W8 of the protrusion 25 of the second outer piece 22. As a desirable mode, as for the 2nd block 42, the larger protrusion 25 is provided in the tire axial direction outside.

  Generally, the shoulder main groove 5 tends to have a lower ground pressure acting than the center main groove 4 and a smaller compressive force of snow in the groove. In the second block 42 of the present embodiment, since the larger protrusion 25 is provided on the shoulder main groove 5 side, a hard snow column is formed even in the shoulder main groove 5.

  The maximum protrusion amount W7 of the protrusion 25 of the first outer piece 21 of the second block 42 is preferably 1.65 times or more than the maximum protrusion amount W8 of the protrusion 25 of the second outer piece 22 of the second block 42. Preferably it is 1.75 times or more, preferably 2.00 times or less, more preferably 1.90 times or less. Such a 2nd block 42 exhibits the above-mentioned effect, maintaining wet performance.

  FIG. 7 shows an enlarged view of the inner shoulder land portion 12 and the outer shoulder land portion 13. As shown in FIG. 7, the inner shoulder land portion 12 is provided between the shoulder main groove 5 and the shoulder sub-groove 6. The inner shoulder land portion 12 is a block row in which inner shoulder blocks 48 divided by a plurality of inner shoulder lateral grooves 47 are arranged in the tire circumferential direction.

  For example, the inner shoulder lateral groove 47 communicates between the shoulder main groove 5 and the shoulder sub-groove 6. For example, the inner shoulder lateral groove 47 is inclined in the direction opposite to the middle lateral groove 44 (shown in FIG. 6) with respect to the tire axial direction. Each inner shoulder lateral groove 47 is displaced with respect to the middle lateral groove 44 in the tire circumferential direction, for example.

  The inner shoulder block 48 is divided into three parts, for example, a pair of outer pieces 20 and 20 on both sides in the tire circumferential direction and a central piece 24 between them by providing only two divided sipes 18. ing.

  In the inner shoulder block 48, only one of the outer pieces 20, 20 has a protrusion 25 protruding in a step shape inward in the tire axial direction from the central piece 24. Such an inner shoulder block 48 strongly compresses the snow in the shoulder main groove 5 while maintaining the drainage of the shoulder main groove 5.

  The outer side shoulder land part 13 is provided in the tire axial direction outer side of the shoulder subgroove 6, for example. The outer shoulder land portion 13 is a block row in which outer shoulder blocks 50 divided by a plurality of outer shoulder lateral grooves 49 are arranged in the tire circumferential direction.

  Each outer shoulder lateral groove 49 extends, for example, along the tire axial direction. Each outer shoulder lateral groove 49 is displaced with respect to each inner shoulder lateral groove 47 in the tire circumferential direction, for example. The groove width of the outer shoulder lateral groove 49 is desirably increased gradually toward the outer side in the tire axial direction, for example. Such outer shoulder lateral grooves 49 exhibit excellent wet performance and wandering performance.

  The outer shoulder lateral groove 49 of the present embodiment includes a first outer shoulder lateral groove 51 and a second outer shoulder lateral groove 52 having a smaller groove width than the first outer shoulder lateral groove 51. For example, the first outer shoulder lateral grooves 51 and the second outer shoulder lateral grooves 52 are alternately provided in the tire circumferential direction.

  The outer shoulder block 50 is provided with, for example, a lag sipe 54 that extends inward in the tire axial direction from the edge 53 on the outer side in the tire axial direction and ends in the outer shoulder block 50. Such a lag sipe 54 exhibits excellent wandering performance while suppressing chipping of the outer shoulder block 50.

  It is desirable that the lag sipe 54 bends and terminates in the tire circumferential direction in the outer shoulder block 50, for example. As a further desirable mode, a pair of lug sipes 54 are provided on the outer shoulder block 50 of the present embodiment, and one lug sipes 54a and the other lug sipes 54b are bent in opposite directions and terminated. Such a pair of lug sipes 54a and 54b reduces the rigidity of the outer shoulder block 50 in the axial direction of the tire to improve the wandering performance, and further suppresses the cracking of the block starting from the inner end of the sipe. Useful.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to illustrated embodiment, It can deform | transform and implement in a various aspect.

A heavy-duty pneumatic tire of size 11R22.5 having the basic pattern of FIG. 1 was prototyped. As a comparative example, as shown in FIG. 8, a tire having a block in which each protrusion of a pair of outer pieces is provided on the same longitudinal groove side was manufactured. Each test tire was tested on snow performance, wet performance, and wear resistance. The common specifications and test methods for each test tire are as follows.
Wearing rim: 8.25 × 22.5
Tire internal pressure: 900kPa
Test vehicle: 10t truck, 50% of the standard load capacity loaded in the center of the loading platform Tire mounting position: all wheels

<Snow performance>
The distance when the test vehicle was accelerated from 5 km / h to 20 km / h on a snowy road surface was measured by GPS. A result is an index which sets a comparative example as 100, and shows that the performance on snow is excellent, so that a numerical value is small.

<Wet performance>
Under the following conditions, the passing time when the test vehicle passed the test course having a total length of 10 m was measured. The results are displayed as an index with the passing time of the comparative example as 100. The smaller the value, the better.
Test vehicle: 10t truck (2-D car)
Loading state: Half-loading state in front of loading platform Test tire mounting location: All wheels Road surface: Asphalt with a 5mm thick water film Starting method: 2nd speed-1500rpm fixed with clutch connected.

<Abrasion resistance>
The amount of wear of the center block after traveling a certain distance on the dry road surface with the test vehicle was measured. The results are displayed as an index with the wear amount of the center block of Comparative Example 1 as 100. It shows that abrasion resistance performance is excellent, so that a numerical value is small.
The test results are shown in Table 1.

As is clear from Table 1, it was confirmed that the heavy-duty pneumatic tires of the Examples balance wet performance and performance on snow in a well-balanced manner.

2 Tread portion 3 Vertical groove 7 Horizontal groove 8 Block 18 Divided sipe 20 Outer piece 21 First outer piece 24 Center piece 25 Projection 28 Non-projection 29 First edge 36 Vertical edge

Claims (7)

A heavy-duty pneumatic tire having a plurality of blocks divided by a longitudinal groove extending in the tire circumferential direction and a lateral groove extending in the tire axial direction on the tread portion,
At least one of the blocks is divided into three parts, a pair of outer pieces and a central piece between them, by a split sipe consisting of only two that cross the block in the tire axial direction.
The central piece has a pair of vertical edges facing the vertical groove and inclined with respect to the tire circumferential direction ,
The first outer piece, which is one of the outer pieces, has a protrusion projecting stepwise from the vertical edge of the central piece to the outside of the block on one longitudinal groove side in the tire axial direction. On the other side of the vertical groove in the direction, it has a non-projecting part that does not protrude outside the block from the vertical edge of the central piece,
In addition, the non-projecting portion includes a first edge that is inclined in a direction intersecting the vertical edge via the split sipe,
The heavy load pneumatic tire according to claim 1, wherein the protrusion includes a third edge inclined in the same direction as the vertical edge with respect to a tire circumferential direction .   2. The heavy duty pneumatic tire according to claim 1, wherein the protrusion includes a second edge inclined in a direction intersecting with the vertical edge of the center piece via the divided sipe. The heavy duty pneumatic tire according to claim 2, wherein the third edge is continuous with the second edge . A heavy-duty pneumatic tire having a plurality of blocks divided by a longitudinal groove extending in the tire circumferential direction and a lateral groove extending in the tire axial direction on the tread portion,
At least one of the blocks is divided into three parts, a pair of outer pieces and a central piece between them, by a split sipe consisting of only two that cross the block in the tire axial direction.
The central piece has a pair of vertical edges facing the vertical groove,
The first outer piece, which is one of the outer pieces, has a protrusion projecting stepwise from the vertical edge of the central piece to the outside of the block on one longitudinal groove side in the tire axial direction. On the other side of the vertical groove in the direction, it has a non-projecting part that does not protrude outside the block from the vertical edge of the central piece,
In addition, the non-projecting portion includes a first edge that is inclined in a direction intersecting the vertical edge via the split sipe,
The second outer piece, which is the other of the outer pieces, has a protrusion projecting stepwise from the vertical edge of the central piece to the outside of the block on the other longitudinal groove side in the tire axial direction. A heavy-duty pneumatic tire having a non-protruding portion that does not protrude outward from the vertical edge of the central piece on the one longitudinal groove side in the direction. A heavy-duty pneumatic tire having a plurality of blocks divided by a longitudinal groove extending in the tire circumferential direction and a lateral groove extending in the tire axial direction on the tread portion,
At least one of the blocks is divided into three parts, a pair of outer pieces and a central piece between them, by a split sipe consisting of only two that cross the block in the tire axial direction.
The central piece has a pair of vertical edges facing the vertical groove,
The first outer piece, which is one of the outer pieces, has a protrusion projecting stepwise from the vertical edge of the central piece to the outside of the block on one longitudinal groove side in the tire axial direction. On the other side of the vertical groove in the direction, it has a non-projecting part that does not protrude outside the block from the vertical edge of the central piece,
In addition, the non-projecting portion includes a first edge that is inclined in a direction intersecting the vertical edge via the split sipe,
The front tread portion has a block pair in which the two blocks are adjacent via the longitudinal groove,
The block pair is a heavy duty pneumatic tire characterized in that the protrusions of each other face each other at least in part through the longitudinal groove. A heavy-duty pneumatic tire having a plurality of blocks divided by a longitudinal groove extending in the tire circumferential direction and a lateral groove extending in the tire axial direction on the tread portion,
At least one of the blocks is divided into three parts, a pair of outer pieces and a central piece between them, by a split sipe consisting of only two that cross the block in the tire axial direction.
The central piece has a pair of vertical edges facing the vertical groove,
The first outer piece, which is one of the outer pieces, has a protrusion projecting stepwise from the vertical edge of the central piece to the outside of the block on one longitudinal groove side in the tire axial direction. On the other side of the vertical groove in the direction, it has a non-projecting part that does not protrude outside the block from the vertical edge of the central piece,
In addition, the non-projecting portion includes a first edge that is inclined in a direction intersecting the vertical edge via the split sipe,
The vertical edge is linear;
The transverse groove facing the first outer piece has a tie bar with a raised groove bottom;
The heavy load pneumatic tire characterized in that the tie bar extends along the lateral groove and straddles an extension line of the vertical edge on one side of the central piece in the tire axial direction. The outer piece has a linear lateral edge facing the lateral groove;
The protrusion protrudes from the extension line,
The tie bar length in the tire axial direction from the intersection of the extension line and the lateral edge to the outer end on one side of the tire tie in the tire axial direction is the tire from the intersection to the outer end in the tire axial direction of the protrusion. The heavy-duty pneumatic tire according to claim 6, which is 0.2 to 0.8 times the maximum protrusion width in the axial direction.

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