JP6082368B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy duty pneumatic tire capable of improving uneven wear resistance.

  In the following Patent Document 1, a plurality of blocks are provided in the tread portion by providing a plurality of main grooves extending continuously in a zigzag shape in the tire circumferential direction and a plurality of lateral grooves communicating between the main grooves. Is proposing a heavy-duty pneumatic tire classified by. The tread surface of each block is divided into a substantially hexagonal shape. Such a block is excellent in rigidity balance as compared with, for example, a block having a substantially square tread surface.

JP 2007-145209 A

  Generally, when a tire is used as a drive wheel, slip occurs between the tread surface of each block and the road surface during driving. In addition, when the tire is loaded, a larger ground pressure acts on the tire equator block in the tread portion than on the tread end block. Due to these effects, even in the tire as described in Patent Document 1, there is a risk that uneven wear such as center wear and heel and toe wear may occur in the block on the tire equator side.

  This invention is made | formed in view of the above actual conditions, and makes it the main objective to provide the heavy duty pneumatic tire which can improve uneven wear-proof performance.

  The present invention provides a load in which a plurality of blocks are divided by providing a plurality of main grooves continuously extending in the tire circumferential direction and a plurality of lateral grooves communicating between the main grooves in the tread portion. A pneumatic tire for heavy use, wherein the main groove includes a pair of crown main grooves extending zigzag on both sides of the tire equator, and the lateral groove is a crown having a substantially hexagonal shape between the crown main grooves. It includes a plurality of crown transverse grooves that divide the block, and in each of the crown blocks, the length of each side of the tread surface is in a range of 0.8 to 1.3 times that of all other sides. It is characterized by.

  In the heavy-duty pneumatic tire according to the present invention, the main groove includes a shoulder main groove extending zigzag on the outer side in the tire axial direction of each crown main groove, and the width of the crown main groove is determined by the shoulder main groove. It is desirable to be smaller than the groove width of the groove.

  In the heavy duty pneumatic tire according to the present invention, the lateral groove includes a plurality of shoulder lateral grooves that divide a shoulder block between the shoulder main groove and a tread end, and an area of a tread surface of the crown block is: It is desirable that it is larger than the area of the tread of the shoulder block.

  In the heavy duty pneumatic tire according to the present invention, it is preferable that a land ratio of a crown region between the crown main grooves is larger than a land ratio of a shoulder region between the shoulder main groove and the tread end.

  In the heavy-duty pneumatic tire according to the present invention, the lateral groove includes a plurality of middle lateral grooves that divide a middle block having a substantially hexagonal tread surface between the crown main groove and the shoulder main groove, In each of the middle blocks, the length of each side of the tread surface is preferably in a range of 0.8 to 1.3 times that of all other sides.

  In the heavy duty pneumatic tire according to the present invention, it is desirable that a maximum width of the crown block in the tire axial direction is larger than a maximum width of the middle block in the tire axial direction.

  In the heavy duty pneumatic tire according to the present invention, it is preferable that the crown lateral groove is inclined in a direction different from the middle lateral groove.

  In the heavy duty pneumatic tire according to the present invention, the distance from the tire equator to the zigzag groove center line of the shoulder main groove is preferably in the range of 50% to 75% of the tread half width.

  The heavy-duty pneumatic tire according to the present invention includes a pair of crown main grooves extending zigzag on both sides of the tire equator in the tread portion, and a plurality of crown blocks in which the tread has a substantially hexagonal shape between the crown main grooves. A crown transverse groove is provided. Since the tread surface of the crown block is formed in a substantially hexagonal shape, for example, the tread surface is excellent in rigidity balance as compared with a block having a substantially rectangular shape.

  In each crown block, the length of each side of the tread surface is in a range of 0.8 to 1.3 times that of all other sides. In such a crown block, since the shape of the tread surface approaches a regular hexagon, the rigidity balance is further enhanced. For this reason, even when the tire of the present invention is used as a drive wheel, the slip with respect to the road surface generated at each part of the tread surface of the crown block is made uniform, and as a result, uneven wear resistance can be improved.

It is an expanded view of the tread part of one Embodiment of this invention. FIG. 2 is a partial enlarged view on the left side of a tread portion including the vicinity of a tire equator C in FIG. 1. FIG. 3 is a partially enlarged view in the vicinity of a crown block in FIG. 2. FIG. 3 is a partially enlarged view of the vicinity of the middle block in FIG. 2. It is an enlarged view of the middle block of FIG. FIG. 3 is a partially enlarged view of the vicinity of a shoulder block in FIG. 2.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread portion 2 of the heavy duty pneumatic tire of the present embodiment (hereinafter sometimes simply referred to as “tire”). FIG. 2 shows an enlarged view of the left side portion including the vicinity of the tire equator C of the tread portion 2 of FIG.

  As shown in FIGS. 1 and 2, the tread portion 2 is provided with a plurality of main grooves 3 extending continuously in the tire circumferential direction.

  The main groove 3 of the present embodiment is a pair of crown main grooves 4 and 4 disposed on both sides of the tire equator C, and the outer side in the tire axial direction of each crown main groove 4 and extends most on the tread end Te side. A pair of shoulder main grooves 5 and 5 are included.

  The main groove 3 allows the tread portion 2 to have a crown region 7 between the crown main grooves 4 and 4, a middle region 8 between the crown main groove 4 and the shoulder main groove 5, and the shoulder main groove 5 and the tread end. A shoulder region 9 between Te is divided. The crown region 7, the middle region 8, and the shoulder region 9 are provided with a crown lateral groove 11, a middle lateral groove 12, and a shoulder lateral groove 13, respectively. Thereby, the crown region 7, the middle region 8 and the shoulder region 9 of the tread portion 2 are divided into a crown block 15, a middle block 16 and a shoulder block 17, respectively.

  In the present specification, the “tread end” is a position on the outermost side in the tire axial direction of the contact surface of the tread portion 2 when a normal tire is loaded with a normal load and brought into contact with a plane with a camber angle of 0 °. It is.

  The “normal state” is a no-load state in which a tire is assembled on a normal rim (not shown) and filled with a normal internal pressure. In the present specification and claims, unless otherwise specified, the dimensions of each part of the tire are values in a normal state. In the normal state, the tire axial distance between the tread ends Te, Te is defined as the tread width TW.

  The “regular rim” is a rim determined 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. For example, “maximum air pressure” for JATMA, “TIRE” for TRA The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  “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. For example, “maximum load capacity” for JATMA, “table for TRA” The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO.

  The crown main groove 4 extends in a zigzag shape continuously in the tire circumferential direction. The crown main groove 4 alternately includes first inclined portions 4c and second inclined portions 4d that are inclined in opposite directions in the tire circumferential direction. Thereby, the crown main groove 4 alternately includes inner top portions 4a protruding toward the tire equator C side and outer top portions 4b protruding toward the opposite side to the inner top portion 4a in the tire circumferential direction.

  In order to maintain the desired block rigidity of the crown block 15 and sufficient drainage in the crown region 7, the angle α1 of the first inclined portion 4c and the second inclined portion 4d of the crown main groove 4 with respect to the tire circumferential direction is, for example, It is desirable to be determined within a range of 15 to 25 degrees. In order to maintain sufficient drainage in the crown region 7, the groove width W1 (shown in FIG. 1) of the crown main groove 4 is, for example, 1.0% to 5.0% of the tread width TW, more preferably It is desirable to be determined within the range of 1.5 to 4.0%.

  As with the crown main groove 4, the shoulder main groove 5 extends in a zigzag manner continuously in the tire circumferential direction. That is, the shoulder main groove 5 alternately includes first inclined portions 5c and second inclined portions 5d that are inclined in opposite directions to each other in the tire circumferential direction. As a result, the shoulder main groove 5 alternately includes inner top portions 5a projecting toward the tire equator C side and outer top portions 5b projecting opposite to the inner top portion 5a in the tire circumferential direction.

  In order to maintain the desired block rigidity of the middle block 16 and drainage in the middle region 8 to the shoulder region 9, the angle α2 of the shoulder main groove 5 with respect to the respective tire circumferential directions of the first inclined portion 5c and the second inclined portion 5d. Is preferably determined within a range of 15 to 25 degrees, for example. Similarly, in order to maintain drainage in the middle region 8 to the shoulder region 9, the groove width W2 (shown in FIG. 1) of the shoulder main groove 5 is, for example, 1.0% to 5.0% of the tread width TW. %, More preferably 1.5 to 4.0%.

  As a more preferable aspect, in this embodiment, the groove width W2 of the shoulder main groove 5 is formed larger than the groove width W1 of the crown main groove 4. According to this aspect, the middle block 16 is disposed close to the crown block 15 side (tire equator C side). For this reason, the load acting on the center portion of the tread is distributed in a balanced manner between the crown block 15 and the middle block 16, and concentration on the crown block 15 can be prevented. Therefore, early wear (center wear) of the crown block 15 can be suppressed. In order to exhibit the above-described action more effectively, the ratio W2 / W1 between the groove width W2 of the shoulder main groove 5 and the groove width W1 of the crown main groove 4 is, for example, in the range of 1.1 to 3.0. Is desirable.

  In order to further improve the above-mentioned center wear resistance while ensuring sufficient drainage, the distance W9 (shown in FIG. 2) from the tire equator C to the zigzag amplitude center line G of the shoulder main groove 5 is tread. The range of 50% to 75% of the half width is desirable. When the distance W9 is less than 50% of the tread half width, the area occupied by the crown block 15 and the middle block 16 is insufficient, the contact pressure acting on these blocks increases, and the center wear resistance may be reduced. On the contrary, when the distance W9 is larger than 75% of the tread half width, the area occupied by the crown block 15 and the middle block 16 becomes excessively large, and there is a possibility that draining to the outside in the tire axial direction becomes difficult.

  In the crown region 7, a plurality of crown lateral grooves 11 are provided. Each crown lateral groove 11 communicates with the inner top portions 4a, 4a of the pair of crown main grooves 4 extending linearly. Thus, a plurality of crown blocks 15 in which the tread surface S forms a substantially hexagonal shape are sectioned in the crown region 7.

  Since such a crown block 15 has a high rigidity at the center of the block and also tends to have a large internal angle at each apex of the tread surface S, it has an excellent rigidity balance. Therefore, the crown block 15 is restrained from being deformed little from the start to the end of the contact and exhibits a good rolling resistance. In addition, when the crown block 15 is brought into contact with the ground, the sliding of each part with respect to the road surface is made uniform. Thereby, the occurrence of uneven wear such as heel and toe wear is suppressed in the crown block 15.

  Further, in each crown block 15, the length of each side (six sides) of the tread surface S is in a range of 0.8 to 1.3 times that of all other sides. Such a tread surface S of the crown block 15 approaches a regular hexagon, and the rigidity balance is further enhanced. For this reason, even when the tire of the present embodiment is used as, for example, a drive wheel, the slip generated between the tread surface S of the crown block 15 and the road surface is made uniform, thereby suppressing the occurrence of uneven wear. In the present embodiment, the six sides of the tread surface S of the crown block 15 have three pairs of opposing sides facing each other. In each pair, the two sides are parallel to each other and have the same length.

  As shown in FIG. 2, the crown lateral groove 11 is inclined with respect to the tire axial direction. The inclination angle β1 of the crown lateral groove 11 is desirably 40 degrees or less, for example. When the inclination angle β1 is larger than 40 degrees, the rigidity of the end portion of the crown block 15 in the tire circumferential direction is lowered, and there is a possibility that uneven wear occurs. On the other hand, when the inclination angle β1 is excessively small, impact noise generated when the crown block 15 contacts the ground increases, and drainage performance may deteriorate. From such a viewpoint, it is desirable that the inclination angle β1 of the crown lateral groove 11 is determined in the range of, for example, 10 to 20 degrees. In order to ensure the drainability of the crown region 7, the groove width W <b> 3 of the crown lateral groove 11 is preferably determined in the range of 5.0 to 10.0 mm.

  The maximum width W7 of the crown block 15 is preferably in the range of 20% to 35% of the tread width TW, for example. Further, in order to increase the rigidity of the crown block 15 in the tire circumferential direction, the tread surface S of the crown block 15 is preferably not a perfect regular hexagon, but a substantially hexagonal shape that is vertically long in the tire circumferential direction.

  FIG. 3 shows a partially enlarged view of the vicinity of the crown block 15 of FIG. As shown in FIG. 3, the crown block 15 of the present embodiment is provided with a shallow crown groove 20 that completely crosses the tread surface S thereof. Such a shallow crown groove 20 divides the tread surface S of the crown block 15 into two parts, but for each “side” of the substantially hexagonal tread surface S, for convenience, except for the shallow crown groove 20, It is determined based on the contour shape of the tread S divided by the crown main groove 4 and the crown lateral groove 11.

  The crown shallow groove 20 has a smaller groove width and smaller groove depth than the crown lateral groove 11. The groove width and groove depth of the shallow crown groove 20 are, for example, 50% or less, preferably 30% or less, of the groove width and groove depth of the crown lateral groove 11, respectively. Such a shallow crown groove 20 provides a space in which the block can be deformed at the time of ground contact while suppressing a decrease in rigidity of the crown block 15, and further improves the uneven wear resistance performance of the crown block 15. Moreover, the crown shallow groove 20 is useful for enhancing the drainage of the crown region 7.

  For example, the shallow crown groove 20 of the present embodiment extends in a zigzag shape so as to bisect the tread surface S of the crown block 15 in the tire circumferential direction. In a preferred embodiment, the shallow crown groove 20 includes a central portion 20a inclined in the direction opposite to the crown lateral groove 11, and a pair of end portions 20b and 20b bent with respect to the central portion 20a. The shallow crown groove 20 extends between the first inclined portions 4 c and 4 c of the crown main grooves 4 and 4.

  The central portion 20 a of the crown shallow groove 20 has the largest length in the crown shallow groove 20. The central portion 20a of the crown shallow groove 20 can divide the tread surface S of the crown block 15 into two block pieces substantially evenly, and can further improve the wear resistance of the crown block 15. When a large tire circumferential force or tire axial force is applied to the tread surface S of the crown block 15, the crown shallow groove 20 closes the groove and brings the block pieces into contact with each other, for example. It is possible to increase the apparent rigidity.

  In a preferred embodiment, the pair of end portions 20 b of the shallow crown groove 20 further includes a widened portion 20 c in which the groove width increases toward the outside of the crown block 15. The portions other than the widened portion 20c of the shallow crown groove 20, that is, the central portion 20a and the end portion 20b extend with a constant groove width. The widened portion 20 c is useful for further improving the drainage performance in the crown region 7.

  As shown in FIG. 1, the middle region 8 is provided with a plurality of middle lateral grooves 12. For example, each middle lateral groove 12 communicates with the outer top 4b of the crown main groove 4 and the inner top 5a of the shoulder main groove 5 in a straight line. As a result, the middle region 8 is divided into a plurality of middle blocks 16 in which the tread surface S has a substantially hexagonal shape. Each middle lateral groove 12 is inclined in the opposite direction to the crown lateral groove 11, for example. Thereby, the edge effect is exhibited with a good balance.

  The middle block 16 in which the tread surface S is formed in a substantially hexagonal shape, like the crown block 15, is suppressed from heel and toe wear, and thus has high uneven wear resistance. Each middle block 16 also preferably has a length of each side (six sides) of the tread S in a range of 0.8 to 1.3 times, for example, with respect to all other sides. Such a tread surface S of the middle block 16 also improves the rigidity balance of the middle block 16 and exhibits excellent uneven wear resistance. In the present embodiment, the six sides of the tread S of the middle block 16 have three pairs of opposing sides facing each other. In each pair, the two sides are parallel to each other and have the same length.

  As shown in FIG. 2, the maximum width W8 of the middle block 16 in the tire axial direction is preferably smaller than the maximum width W7 of the crown block 15 in the tire axial direction, for example. The middle block 16 having a relatively small maximum width in this way helps to ensure drainage from the tire equator C side to the tire axial direction outer side while reducing the load borne by the crown block 15. Similarly, in order to increase the rigidity of the middle block 16 in the tire circumferential direction, the tread surface S of the middle block 16 is preferably not a perfect regular hexagon but a substantially hexagonal shape that is vertically long in the tire circumferential direction.

  The groove width W4 of the middle lateral groove 12 can be determined in the same range as the crown lateral groove 11. As a particularly preferable aspect, the middle lateral groove 12 of the present embodiment has a groove width W4 that is larger than the groove width W3 of the crown lateral groove 11. As a result, drainage performance in the middle region is improved, while in the crown region 7, the high pattern rigidity of the crown region 7 is obtained by the small crown lateral groove 11, and as a result, the uneven wear resistance performance of the crown block 15 is improved.

  In order to express the above action more effectively, the ratio W4 / W3 of the groove width W4 of the middle lateral groove 12 and the groove width W3 of the crown lateral groove 11 is, for example, in the range of 1.1 to 3.0, more preferably The range of 1.5 to 2.5 is desirable.

  When the tire turns, the middle block 16 tends to have a greater lateral force than the crown block 15. Therefore, it is desirable that the inclination angle β2 of the middle lateral groove 12 is set, for example, in the range of 10 to 20 degrees, and in particular, an angle smaller than the inclination angle β1 of the crown lateral groove 11. As a result, the side of the tread surface S of the middle block 16 facing the middle lateral groove 12 is closer to the tire axial direction, and the uneven wear resistance performance at both end portions of the middle block 16 in the tire circumferential direction can be further enhanced.

  FIG. 4 shows a partially enlarged view of the middle block 16 of FIG. As shown in FIG. 4, a middle shallow groove 21 that completely crosses the tread surface S is also provided in the middle block 16 of the present embodiment. In such an embodiment, the tread surface S of the middle block 16 is divided into two by the middle shallow groove 21, but each side of the substantially hexagonal tread surface S of the middle block 16 is excluded from the middle shallow groove 21. Thus, it is determined based on the contour shape of the tread surface S defined by the crown main groove 4, the shoulder main groove 5, and the middle lateral groove 12.

  The middle shallow groove 21 has a smaller groove width and smaller groove depth than the middle lateral groove 12. The groove width and groove depth of the middle shallow groove 21 are, for example, 50% or less, preferably 30% or less of the groove width and groove depth of the middle lateral groove 12, respectively. The middle shallow groove 21 as described above provides a space in which the block at the time of ground contact can be deformed while suppressing a decrease in rigidity of the middle block 16, and further improves the wear resistance of the middle block 16. Further, the middle shallow groove 21 is useful for enhancing the drainage of the middle region 8.

  The middle shallow groove 21 of the present embodiment extends in a zigzag shape, for example, so as to bisect the tread surface S of the middle block 16 in the tire circumferential direction. In a preferred embodiment, the middle shallow groove 21 includes a central portion 21a inclined in the direction opposite to the middle lateral groove 12, and a pair of end portions 21b and 21b bent with respect to the central portion 21a. The middle shallow groove 21 communicates between the crown main groove 4 and the shoulder main groove 5.

  The middle portion 21 a of the middle shallow groove 21 has the largest length in the middle shallow groove 21. The middle portion 21a of the middle shallow groove 21 can divide the middle block 16 into two block pieces in a well-balanced manner, and can further improve the wear resistance of the middle block 16. Further, when a large tire circumferential force or tire axial force is applied to the tread surface S of the middle block 16, the middle shallow groove 21 closes the groove and brings the block pieces into contact with each other, for example. It is possible to increase the apparent rigidity.

  In a preferred embodiment, the pair of end portions 21 b of the middle shallow groove 21 further includes a widened portion 21 c in which the groove width increases toward the outside of the middle block 16. Portions other than the widened portion 21c of the middle shallow groove 21, that is, the central portion 21a and the end portion 21b extend with a constant groove width. Such a widened portion 21 c is useful for further enhancing the drainage performance in the middle region 8.

  FIG. 5 shows an enlarged view in which the middle block 16 is further enlarged. As shown in FIG. 5, the widened portion 21 c of the middle shallow groove 21 has one groove edge and the other groove edge, and the inner angle γ formed by these is preferably 30 to 110 degrees. . Thereby, effective drainage and the rigidity of the middle block 16 can be improved with good balance.

  It is desirable that the widened portion 21c of the middle shallow groove 21 is located at a substantially central portion of the side of the tread surface S of the middle block 16 in which the middle shallow groove 21 is provided. Such a widened portion 21c helps to suppress the rigidity of the middle block 16 in a more balanced manner. In particular, on the tread S of the middle block 16, the length L1 from the end points 16b, 16b on both sides of the one side 16a where the widened portion 21c is located to the center point 16c of the maximum opening width L3 of the widened portion 21c is, for example, the side 16a The range of 0.3 to 0.7 times the length L2 is desirable.

  The maximum opening width L3 of the widened portion 21c is preferably in the range of 0.2 to 0.5 times the length L2 of the side 16a of the tread surface S provided with the widened portion 21c. If the maximum opening width L3 of the widened portion 21c is less than 0.2 times the length L2, the drainage performance may not be sufficiently improved. Conversely, if the maximum opening width L3 is larger than 0.5 times the length L2, the rigidity balance of the middle block 16 may be deteriorated.

  In order to exhibit the above-described effects more effectively, the shortest length L4 from the end J on the block center side of the widened portion 21c to the side 16a of the tread surface S of the middle block 16 where the widened portion 21c is located is, for example, It is desirable that it is in the range of 0.05 to 0.2 times the width L5 of the middle block in the direction perpendicular to 16a.

  As shown in FIGS. 1 and 2, the shoulder region 9 is provided with a plurality of shoulder lateral grooves 13. Each shoulder lateral groove 13 extends, for example, from the outer top portion 5b of the shoulder main groove 5 to the tread end Te on the outer side in the tire axial direction. Thus, a plurality of shoulder blocks 17 are sectioned in the shoulder region 9.

  The inclination angle β3 of each shoulder lateral groove 13 with respect to the tire axial direction is preferably in the range of 0 to 20 degrees, for example. Particularly preferably, the inclination angle β3 of the shoulder lateral groove 13 is set to be smaller than the inclination angle β2 of the middle lateral groove 12. As a result, the rigidity of both end portions of the shoulder block 17 in the tire circumferential direction can be increased, and consequently uneven wear such as heel and toe wear can be suppressed.

  FIG. 6 shows a partially enlarged view of the shoulder block 17 of FIG. As shown in FIG. 6, a shoulder shallow groove 22 that completely crosses the tread surface S is also provided in the shoulder block 17 of the present embodiment. The shoulder shallow groove 22 of the present embodiment includes a central portion 22a and a pair of end portions 22b and 22b bent from both sides of the central portion 22a, and extends in a zigzag shape in the tire axial direction. Further, only the end portion 22b on the tread end Te side includes the widened portion 22c in which the groove width increases toward the outer side in the tire axial direction of the shoulder block 17.

  The groove width and the groove depth of the shoulder shallow groove 22 are, for example, 50% or less, preferably 30% or less of the groove width and groove depth of the shoulder lateral groove 13, for example. Such a shallow shoulder groove 22 facilitates an appropriate deformation of the shoulder block 17 at the time of ground contact to reduce wear energy, and helps to further improve the drainage of the shoulder region 9.

  As shown in FIGS. 1 and 2, the area S3 of the tread surface S of the shoulder block 17 is preferably smaller than the area S1 of the tread surface S of the crown block 15 in order to prevent center wear more effectively.

In order to exhibit the above-described effects more effectively, the area S3 of the tread surface S of the shoulder block 17 includes the area S1 of the tread surface S of the crown block 15, the area S2 of the tread surface S of the middle block 16, and the following formula: It is desirable to be satisfied.
S3 <S1 / 2 + S2

  That is, the sum of ½ of the area S2 of the tread surface S of one middle block 16 and the area S1 of the tread surface S of one crown block 15 is set larger than the area S3 of the tread surface S of one shoulder block 17. It is desirable to be done. Thereby, on each side of the tire equator C, the load acting on the center portion of the tread is sufficiently supported by the crown block 15 and the middle block 16, and the contact pressure acting on them can be reduced.

  From the same viewpoint, it is desirable that the land ratio of the shoulder region 9 is smaller than the land ratio of the crown region 7. Here, the land ratio means the ratio of the total area of the tread surface of each block to the total area of the virtual ground plane that fills all the lateral grooves in each region. Note that when the boundaries between the regions 7 and 9 are determined, the groove edges of the main grooves are virtually extended at the intersections of the main grooves and the lateral grooves as shown in FIG.

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

Tires (size: 11R22.5) having the basic pattern shown in FIG. 1 and based on the specifications of Table 1 were prototyped and their performance was tested.
The test method is as follows.

<Center wear resistance>
Under the following conditions, the tire of Example 1 was mounted on one of the rear wheels of the test vehicle, each sample tire was mounted on the other, and each tire was run until the wear reached 50%. The heights of the crown block, middle block, and shoulder block of the tire were measured at three locations on the tire circumference. Based on the average of the measured values, the height of the crown block was compared with the height of the shoulder block. The evaluation shows that the closer the value is to 1, the higher the height of the crown block and the height of the shoulder block, and the better the center wear resistance.
Rims: 22.5 × 8.25
Internal pressure: 720kPa

<Uneven wear resistance>
After the test, the height of the crown block and the middle block was compared with the height of the shoulder block, and the presence or absence of early wear of the shoulder block was confirmed. The evaluation is indicated as “Yes” when the early wear is confirmed in the shoulder block, and as “None” when the early wear is not confirmed.

<Wet performance>
The test vehicle in which each sample tire was mounted on all wheels was run on a wet asphalt road surface having a 5 mm water film, and the time was measured while passing 10 m from the moment the clutch was connected. The evaluation is the reciprocal of the measured value, and is indicated by an index with Example 1 as 100. The larger the value, the better the wet performance.

  As shown in Table 1, it was confirmed that the tires of each example can improve uneven wear resistance.

2 Tread portion 3 Main groove 4 Crown main groove 11 Crown lateral groove 15 Crown block C Tire equator S Tread

Claims (8)

A heavy load pneumatic tire in which a plurality of blocks are divided by providing a plurality of main grooves continuously extending in the tire circumferential direction and a plurality of lateral grooves communicating between the main grooves in the tread portion. Because
The main groove includes a pair of crown main grooves extending zigzag on both sides of the tire equator,
The lateral groove includes a plurality of crown lateral grooves that divide a crown block having a substantially hexagonal shape between the crown main grooves,
In each crown block, the length of each side of the tread surface is in a range of 0.8 to 1.3 times as much as all other sides ,
Each crown block is provided with a crown shallow groove that completely crosses the tread surface,
The crown shallow groove has a smaller groove width and smaller groove depth than the crown lateral groove,
The crown shallow groove includes a central portion inclined in the opposite direction to the crown lateral groove, and a pair of end portions that are bent with respect to the central portion . The main groove includes a shoulder main groove extending zigzag on the outer side in the tire axial direction of each crown main groove,
2. The heavy duty pneumatic tire according to claim 1, wherein a width of the crown main groove is smaller than a width of the shoulder main groove. The lateral groove includes a plurality of shoulder lateral grooves that divide a shoulder block between the shoulder main groove and the tread end,
The heavy duty pneumatic tire according to claim 2, wherein an area of a tread of the crown block is larger than an area of a tread of the shoulder block.   4. The heavy duty pneumatic tire according to claim 3, wherein a land ratio of a crown region between the crown main grooves is larger than a land ratio of a shoulder region between the shoulder main groove and the tread end. The lateral groove includes a plurality of middle lateral grooves that divide a middle block having a substantially hexagonal shape between the crown main groove and the shoulder main groove,
5. The heavy load according to claim 2, wherein the length of each side of the tread surface in each middle block is in a range of 0.8 to 1.3 times that of all other sides. Pneumatic tire. The heavy-duty pneumatic tire according to claim 1, wherein the crown shallow groove extends so as to bisect the tread surface of the crown block in the tire circumferential direction. 6. The heavy duty pneumatic tire according to claim 1, wherein both ends of the shallow crown groove are connected not to corners of the tread but to opposite sides. The heavy load pneumatic tire according to any one of claims 1 to 7, wherein the pair of end portions of the shallow crown groove further includes a widened portion whose groove width increases toward the outside of the crown block.

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