JP5841572B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy duty tire in which a plurality of blocks are formed in a tread portion.

  Conventionally, a heavy duty tire has been proposed in which a number of blocks are formed in the tread portion by four main grooves extending in the tire circumferential direction and a plurality of lateral grooves extending from the main groove in the tire axial direction (for example, See Patent Document 1 below). Such a tire is provided with a shallow bottom portion in which the groove bottom is raised in order to prevent the stone from being bitten into the lateral groove.

JP 2005-7919 A

  However, the blocks are formed in substantially the same size, and the difference in deformation of each block at the time of grounding is small. For this reason, for example, when a stone is caught in a main groove extending in the tire circumferential direction, there is a tendency that the stone is difficult to be removed by subsequent running.

  The present invention has been made in view of the actual situation as described above, and can increase the difference in deformation of adjacent blocks at the time of ground contact, thereby easily removing stones and the like that have been bitten, and improving the stone biting performance. The main purpose is to provide a heavy duty tire.

The present invention provides a pair of crown main grooves extending continuously in the tire circumferential direction on both sides of the tire equator on the tread portion, and a pair of shoulder mains extending continuously in the tire circumferential direction on the outer side in the tire axial direction of the crown main grooves. A heavy duty tire comprising a plurality of crown lateral grooves that connect between the pair of crown main grooves, and a plurality of middle lateral grooves that connect between the crown main grooves and the shoulder main grooves. By being provided, the tread portion is divided by a crown land portion including a crown block divided by the pair of crown main grooves and the crown transverse groove, and by the crown main groove, the shoulder main groove, and the middle transverse groove. A middle land portion including a middle block, and a shoulder land portion divided by the shoulder main groove and the tread end, and the crown The groove has a first zigzag piece inclined at an angle of 15 to 30 degrees with respect to the tire circumferential direction and a second zigzag piece inclined at an angle of 15 to 30 degrees with respect to the tire circumferential direction and opposite to the first zigzag piece. By alternately arranging the zigzag pieces, it has a plurality of crown inner tops that are convex toward the tire equator side, and a plurality of crown outer tops that are convex outward in the tire axial direction, The crown inner groove of one crown main groove extends from the crown inner top of the other crown main groove to the crown inner top, and is inclined in the same direction at an angle of 45 to 75 degrees with respect to the tire circumferential direction. A first middle lateral groove whose inner end in the tire axial direction is connected to the crown outer top portion of the crown main groove and is inclined in the same direction as the crown lateral groove, and an inner end in the tire axial direction is the crown The connected to said crown outer top and the first middle lateral grooves of the groove and a second middle lateral grooves are inclined in opposite directions are alternately disposed, the middle block and the area S1 of the tread of the crown block the value of the ratio of the tread area S2 (S2 / S1) is characterized scope der Rukoto of 1.3 to 1.8.

  In the heavy load tire according to the present invention, the shoulder main groove has a first zigzag piece inclined at an angle of 15 to 30 degrees with respect to the tire circumferential direction, and an angle of 15 to 30 degrees with respect to the tire circumferential direction. By alternately arranging the first zigzag piece and the second zigzag piece that is inclined in the opposite direction, the shoulder zigzag pitch of the shoulder main groove has a plurality of shoulder inner top portions that are convex on the tire equator side. The zigzag pitch of the crown main groove is the same, and the outer end of the middle lateral groove in the tire axial direction is preferably connected to the shoulder inner top portion.

  In the heavy duty tire according to the present invention, it is desirable that the shoulder land portion is not provided with a lateral groove.

  The heavy duty tire according to the present invention preferably has a flatness ratio of 75% or less and a tread width of 375 mm or more.

  In the heavy duty tire according to the present invention, it is preferable that the crown block has a substantially octagonal tread surface by chamfering a corner portion where the crown main groove and the crown lateral groove intersect.

In the heavy duty tire according to the present invention, each crown lateral groove extends from the crown inner top of one crown main groove to the crown inner top of the other crown main groove, and at an angle of 45 to 75 degrees with respect to the tire circumferential direction. Inclined in the same direction. On the other hand, the middle lateral groove includes a first middle lateral groove whose inner end in the tire axial direction is connected to the crown outer top portion of the crown main groove and is inclined in the same direction as the crown lateral groove, and an inner end in the tire axial direction is the crown. Second middle lateral grooves connected to the crown outer top of the main groove and inclined in the direction opposite to the first middle lateral groove are alternately provided. As a result, the middle block is divided larger than the crown block. Therefore, the crown block having relatively low rigidity deforms more greatly than the middle block having high rigidity at the time of grounding. Due to the deformation of the two unbalanced blocks, for example, different movements are imparted to one side and the other side of the stones etc. that are bitten in the crown main groove, and the stones etc. can be easily removed, and the tire resistance is improved. Stone biting performance is improved.

It is an expanded view of the tread part of the tire for heavy loads of one embodiment of the present invention. It is the elements on larger scale near the crown block of FIG. It is the elements on larger scale near the middle block of FIG. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is CC sectional drawing of FIG.

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

  As shown in FIG. 1, the tire 1 according to this embodiment includes a pair of crown main grooves 3 and 3 that extend continuously on the tread portion 2 on both sides of the tire equator C in the tire circumferential direction. A pair of shoulder main grooves 4, 4 extending continuously in the tire circumferential direction on the outer side in the tire axial direction, a plurality of crown lateral grooves 5 connecting between the pair of crown main grooves 3, 3, the crown main groove 3, and the shoulder main A plurality of middle lateral grooves 6 that are connected to the grooves are provided.

  The tread portion 2 is divided by a crown land portion 8 including a crown block 7 divided by a pair of crown main grooves 3 and 3 and a crown transverse groove 5, and by a crown main groove 3, a shoulder main groove 4 and a middle transverse groove 6. A middle land portion 10 including the middle block 9 and a shoulder land portion 11 divided by the shoulder main groove 4 and the tread end Te are formed.

  The “tread end” is the outermost end in the tire axial direction of the contact surface when the normal tire 1 is loaded with a normal load and contacted with a flat surface at a camber angle of 0 °. In this specification, when there is no notice in particular, the dimension of each part of the tire 1 is a value in a normal state.

  The “normal state” is a state in which the tire 1 is assembled on a normal rim (not shown) and filled with a normal internal pressure and is not loaded. In this specification, when there is no notice in particular, the dimension of each part of the tire 1 is a value in a normal state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire 1 is based. For example, “Standard Rim” for JATMA and “Design Rim” for TRA. "If it is ETRTO, it is" Measuring Rim ".

  The “regular internal pressure” is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire 1 is based. For example, “maximum air pressure” for JATMA, and table for TRA. The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  The “regular load” is a load determined by each standard for each tire in a standard system including a standard on which the tire 1 is based. For example, “maximum load capacity” for JATMA, and “TRA” for TRA. The maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", "LOAD CAPACITY" for ETRTO.

  In the tire 1 of the present embodiment, for example, the tread width TW between the tread ends Te is preferably 375 mm or more. Such a tire 1 has a large contact surface, and can suppress the occurrence of slip even when a large lateral load is applied during turning, for example. Further, in the tire 1 of the present embodiment, for example, it is desirable that the flatness indicating the ratio of the cross-sectional height to the cross-sectional width of the tire 1 as a percentage is 75% or less. In such a tire 1, the movement of the contact surface of the tread portion 2 with respect to the mounted rim is reduced, which is useful for improving the braking performance and turning performance of the tire 1.

  The crown main groove 3 and the shoulder main groove 4 extend in a zigzag shape. The zigzag crown main groove 3 and shoulder main groove 4 have a higher edge component in the tire axial direction than, for example, a linear main groove, and improve the traction performance of the tire 1.

  The crown main groove 3 and the shoulder main groove 4 of the present embodiment are arranged, for example, at equal intervals in the tire axial direction. It is desirable that the crown main groove 3 and the shoulder main groove 4 are provided with the same zigzag pitch, zigzag amplitude, and arrangement phase, for example.

  FIG. 2 shows a partially enlarged view in which the vicinity of the crown block 7 in FIG. 1 is enlarged. As shown in FIG. 2, the crown main groove 3 is formed by alternately arranging the first zigzag pieces 3 </ b> A and the second zigzag pieces 3 </ b> B. The first zigzag piece 3A is inclined at an angle of 15 to 30 degrees with respect to the tire circumferential direction. The second zigzag piece 3B also has an angle of 15 to 30 degrees with respect to the tire circumferential direction, but is inclined in the opposite direction to the first zigzag piece 3A. Thereby, the crown main groove 3 has a plurality of crown inner top portions 3C that are convex toward the tire equator C side, and a plurality of crown outer top portions 3D that are convex outward in the tire axial direction.

  The crown main groove 3 of the present embodiment is provided with a plurality of protrusions 3E that protrude from the groove bottom 3S. The protrusion 3E is provided in a rectangular block shape, for example. The protrusion 3 </ b> E suppresses the entry of stones or the like into the crown main groove 3 and improves the stone biting performance of the tire 1.

  FIG. 3 shows a partially enlarged view in which the vicinity of the middle block in FIG. 1 is enlarged. As shown in FIG. 3, the shoulder main groove 4 is formed by alternately arranging the first zigzag pieces 4 </ b> A and the second zigzag pieces 4 </ b> B. The first zigzag piece 4A is inclined at an angle of 15 to 30 degrees with respect to the tire circumferential direction. The second zigzag piece 4B also has an angle of 15 to 30 degrees with respect to the tire circumferential direction, but is inclined in the opposite direction to the first zigzag piece 4A. As a result, the shoulder main groove 4 has a plurality of shoulder inner top portions 4C that are convex toward the tire equator C side and a plurality of shoulder outer top portions 4D that are convex outward in the tire axial direction.

  For example, the shoulder outer top portion 4D is formed in a straight line along the tire circumferential direction. According to such a configuration of the shoulder outer top portion 4D, occurrence of cracks starting from the shoulder outer top portion 4D is suppressed.

  The shoulder main groove 4 of the present embodiment is provided with a plurality of protrusions 4E that protrude from the groove bottom 4S, like the crown main groove 3. The protrusion 4E is also in the shape of a rectangular block, which suppresses the entry of stones or the like into the shoulder main groove 4 and improves the stone-resisting performance of the tire 1.

As shown in FIG. 2, the crown lateral groove 5 extends from the crown inner top portion 3 </ b> C of one crown main groove 3 to the crown inner top portion 3 </ b> C of the other crown main groove 3. The crown main grooves 3 and 3 of the present embodiment have the same zigzag arrangement phase, and the crown inner top portions 3C of the pair of crown main grooves 3 are displaced in the tire circumferential direction. Thereby, the crown lateral groove 5 is inclined at an angle of 45 to 75 degrees with respect to the tire circumferential direction.

  The crown block 7 is divided by the crown main groove 3 and the crown lateral groove 5. The crown block 7 of the present embodiment is divided into a zigzag pair of crown main grooves 3 and a pair of crown transverse grooves 5, and is formed in a hexagonal shape having sides facing each other in parallel.

  FIG. 4 shows an AA cross section of FIG. As shown in FIG. 2 or 4, in a preferred embodiment, the tread surface 7 </ b> S of the crown block 7 has a corner portion 15 where the crown main groove 3 and the crown lateral groove 5 intersect with each other, for example, in a chamfered shape. The corner portion 15 has the smallest inner angle and is sharp. For this reason, the corner portion 15 is less rigid than the other vertices of the crown block 7 and may cause cracks. The tread surface 7S of the present embodiment is formed in a substantially octagonal shape by the corner portion 15 being formed in a chamfered shape. Such a polygonal tread surface 7S increases the directionality in which the edge component of the crown block 7 can be exhibited, and helps to suppress the occurrence of cracks in the corner portion 15.

  As shown in FIG. 3, the middle lateral groove 6 includes a first middle lateral groove 6A and a second middle lateral groove 6B. These first middle lateral grooves 6A and second middle lateral grooves 6B are provided alternately in the tire circumferential direction.

  The first middle lateral groove 6 </ b> A is inclined in the same direction as the crown lateral groove 5, and the inner end 6 i in the tire axial direction is connected to the crown outer top portion 3 </ b> D of the crown main groove 3. The outer end of the first middle lateral groove 6 </ b> A is connected to the shoulder inner top portion 4 </ b> C of the shoulder main groove 4. The second middle lateral groove 6B is inclined in the opposite direction to the first middle lateral groove 6A, and the inner end 6i in the tire axial direction is connected to the crown outer top 3D of the crown main groove 3. The outer end of the second middle lateral groove 6B is connected to the shoulder inner top portion 4C of the shoulder main groove 4.

  Due to the crown main groove 3, the shoulder main groove 4, and the middle lateral groove 6, the middle block 9 includes a first block 9A and a second block 9B that is axisymmetric about the axis in the tire circumferential direction on the first block 9A. . These first blocks 9A and second blocks 9B are alternately arranged in the tire circumferential direction.

  The first block 9 </ b> A has a block wall surface 9 </ b> Ai on the inner side in the tire axial direction that protrudes toward the tire equator C side, and is formed by one zigzag pitch of the crown main groove 3. The block wall surface 9Ao on the outer side in the tire axial direction of the first block 9A is recessed toward the tire equator C side and is formed by two zigzag pitches of the shoulder main groove 4.

  On the contrary, the second block 9B has a block wall surface 9Bi on the inner side in the tire axial direction that is recessed toward the tread end Te, and is formed with two zigzag pitches of the crown main groove 3. The block wall surface 9Bo on the outer side in the tire axial direction of the second block 9B is convex at the tread end Te, and is formed by one zigzag pitch of the shoulder main groove 4.

  With respect to the first block 9A and the second block 9B, the block wall surface 7A of the crown block 7 is formed by one zigzag pitch of the crown main groove 3. Therefore, in the tire 1 of the present embodiment, the middle block 9 is divided into sizes having a tread surface that is approximately 1.5 times the crown block 7. For this reason, the crown block 7 is deformed more greatly than the middle block 9 at the time of grounding based on the difference in rigidity between the two blocks. Due to the deformation of the two unbalanced blocks, for example, different movements are imparted to one side and the other side of the stone biting into the crown main groove 3. Therefore, the stone in the main groove is easily removed, and the stone biting performance of the tire 1 is improved.

  For example, the area S2 of the tread surface 9S of the middle block 9 is changed by changing the angle of the first middle lateral groove 6A and the second middle lateral groove 6B with respect to the tire axial direction (in other words, the zigzag pitch of the shoulder main groove 4). Can do.

  The ratio (S2 / S1) of the area S1 of the tread surface 7S of the crown block 7 and the area S2 of the tread surface 9S of the middle block 9 is preferably in the range of 1.3 to 1.8, for example. When the value of the ratio (S2 / S1) is less than 1.3, there is a possibility that a sufficient difference in deformation between the crown block 7 and the middle block 9 does not occur, and it is not possible to remove the biting stone or the like. On the contrary, when the value of the ratio (S2 / S1) is larger than 1.8, if the crown block 7 is excessively small, the rigidity of the crown block 7 is lowered, and the edge effect may not be sufficiently exhibited. If the block 9 is excessively large, the edge component in the tire axial direction of the middle land portion 10 may be insufficient.

  FIG. 5 is a sectional view taken along line BB in FIG. As shown in FIG. 2 or 5, the crown transverse groove 5 of the present embodiment desirably includes a shallow bottom portion 5 </ b> A that protrudes from the groove bottom 5 </ b> S at the center in the longitudinal direction. The shallow bottom portion 5A is provided in a block shape that connects between the adjacent crown blocks 7 and 7. The shallow bottom portion 5 </ b> A increases the rigidity of the crown land portion 8, suppresses the entry of stones and the like into the crown lateral groove 5, and improves the stone resistance performance of the tire 1.

  6 is a cross-sectional view taken along the line CC of FIG. As shown in FIG. 3 or FIG. 6, the middle lateral groove 6 of the present embodiment desirably includes a shallow bottom portion 6 </ b> E protruding from the groove bottom 6 </ b> S at the center in the longitudinal direction. The shallow bottom portion 6E is provided in a block shape that connects between the adjacent middle blocks 9 and 9. The shallow bottom portion 6 </ b> E increases the rigidity of the middle land portion 10, suppresses the entry of stones or the like into the middle lateral groove 6, and improves the stone resistance performance of the tire 1.

  As shown in FIG. 1, the shoulder land portion 11 of the present embodiment is not provided with a lateral groove and is formed as a rib continuous in the tire circumferential direction. Such a shoulder land portion 11 has extremely high rigidity, and the steering stability performance of the tire 1 is greatly improved. In addition, when the rigidity of the shoulder land portion 11 is extremely high, the middle block 9 adjacent to the shoulder land portion 11 may be unevenly worn at an early stage. However, since the middle block 9 of this embodiment is formed relatively large and has higher rigidity than the crown block 7, the occurrence of uneven wear is suppressed.

  In the tread portion 2 of the present embodiment, for example, a shoulder outer lateral groove 16 that is continuous from the tread end Te to the outer side in the tire axial direction of the shoulder land portion 11 is provided. The shoulder outer lateral groove 16 serves to adjust the rigidity of the shoulder land portion 11 and prevent uneven wear on the shoulder land portion 11.

  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.

Test tires having the basic pattern shown in FIG. 1 and based on the specifications in Table 1 were prototyped and their performance was tested.
Each test method is as follows.

<Stone-resistant performance>
Each sample tire was incorporated into an 11.75 × 22.5 rim with an internal pressure of 830 kPa and mounted on the trailer shaft of the truck. The test truck was confirmed to have a number of stones on the tire after traveling 50000 km so that the traveling ratio on the paved road and rough terrain was approximately equal. The evaluation is the reciprocal of the number of stone bites, and is indicated by an index with Comparative Example 1 being 100. The larger the value, the better.

<Uneven wear resistance>
After running the test track for 10,000 km, the height of each block from the bottom of the crown main groove or middle main groove was confirmed. The evaluation is the confirmed block height, and is indicated by an index with Comparative Example 1 as 100. The larger the value, the better.

  As shown in Table 1, it was confirmed that the tires of the examples had improved stone biting resistance and uneven wear resistance.

DESCRIPTION OF SYMBOLS 1 Heavy duty tire 2 Tread part 3 Crown main groove 4 Shoulder main groove 5 Crown horizontal groove 6 Middle horizontal groove 7 Crown block 9 Middle block C Tire equator

Claims (5)

The tread includes a pair of crown main grooves extending continuously in the tire circumferential direction on both sides of the tire equator, and a pair of shoulder main grooves extending continuously in the tire circumferential direction on the outer side in the tire axial direction of the crown main grooves. A heavy duty tire,
By providing a plurality of crown transverse grooves that connect between the pair of crown main grooves and a plurality of middle transverse grooves that connect between the crown main grooves and the shoulder main grooves, A crown land portion including a crown block divided by a pair of crown main grooves and the crown transverse groove, a middle land portion including a middle block divided by the crown main groove, the shoulder main groove and the middle transverse groove, and the shoulder The shoulder land section divided by the main groove and the tread end is formed,
The crown main groove is inclined in the direction opposite to the first zigzag piece at an angle of 15 to 30 degrees with respect to the tire circumferential direction and the first zigzag piece at an angle of 15 to 30 degrees with respect to the tire circumferential direction. The second zigzag pieces to be alternately arranged have a plurality of crown inner top portions that are convex toward the tire equator side, and a plurality of crown outer top portions that are convex outward in the tire axial direction,
Each crown transverse groove extends from the crown inner top of one crown main groove to the crown inner top of the other crown main groove, and is inclined in the same direction at an angle of 45 to 75 degrees with respect to the tire circumferential direction. And
The middle lateral groove includes a first middle lateral groove whose inner end in the tire axial direction is connected to the crown outer top of the crown main groove and is inclined in the same direction as the crown lateral groove, and an inner end in the tire axial direction is the Second middle lateral grooves connected to the crown outer top portion of the crown main groove and inclined in the direction opposite to the first middle lateral grooves are alternately provided ,
The value of the ratio (S2 / S1) of the area S2 of the tread of the the area S1 middle block tread of the crown block, heavy duty tire characterized by a range der Rukoto of 1.3 to 1.8.
The shoulder main groove is inclined in the direction opposite to the first zigzag piece at an angle of 15 to 30 degrees with respect to the tire circumferential direction and the first zigzag piece at an angle of 15 to 30 degrees with respect to the tire circumferential direction. The second zigzag pieces to be arranged alternately have a plurality of shoulder inner tops that are convex on the tire equator side,
2. The heavy load according to claim 1, wherein a zigzag pitch of the shoulder main groove is the same as a zigzag pitch of the crown main groove, and an outer end of the middle lateral groove in a tire axial direction is connected to the shoulder inner top portion. tire.   The heavy duty tire according to claim 1, wherein the shoulder land portion is not provided with a lateral groove.   The heavy duty tire according to any one of claims 1 to 3, wherein the flatness is 75% or less and the tread width is 375 mm or more.   The heavy load tire according to any one of claims 1 to 4, wherein the crown block has a substantially octagonal tread surface by chamfering a corner portion where the crown main groove and the crown lateral groove intersect.

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