JP2008155817A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily achieve improvement of both block tear resistance and uneven wear resistance in regard to second blocks 21. <P>SOLUTION: A pair of first circumferential direction main grooves 5 and a pair of second circumferential direction grooves 7 have predetermined groove depths, respectively. A spreading angle θ of a wall face 19a of each second lug groove 19 is set ≥10°and ≤15°. A ratio (m/f) of the maximum length m in the tire circumferential direction C to the maximum width f in the tire width direction W in each second block 21 is set ≥1.5 and ≤1.9. A cross section in the longitudinal direction in each tie bar 25 has an arcuate shape, and the maximum height of each tie bar 25 is set ≥20% and ≤30% of the predetermined groove depth. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heavy duty pneumatic tire having a block pattern on a tread, which is used in heavy duty vehicles such as trucks and buses.

  There exists what is shown in patent document 1 as a prior art of the heavy duty pneumatic tire which has the block pattern in the tread, and the structure of this prior art is as follows.

  That is, the tread is provided with a pair of first circumferential main grooves so as to sandwich the tire equator line, and each of the first first circumferential main grooves extends in the tire circumferential direction. Further, the tread is provided with a pair of second circumferential main grooves so as to sandwich the pair of first circumferential main grooves, and each of the second circumferential main grooves extends in the tire circumferential direction. Each extends.

  A plurality of center lug grooves are provided at equal intervals in the tire circumferential direction at the center of the tread, and each of the center lug grooves connects the pair of first circumferential main grooves to the tire. Each extends in the width direction. A plurality of center blocks are partitioned in the tire circumferential direction by the pair of first circumferential main grooves and the plurality of center lug grooves.

  A plurality of second lug grooves are provided at equal intervals in the tire circumferential direction on both the left and right sides of the center portion of the tread, and each of the second lug grooves is adjacent to the adjacent first circumferential main groove. The tire extends in the tire width direction so as to connect the second circumferential main grooves. A plurality of center blocks are partitioned in the tire circumferential direction by the adjacent first circumferential main groove, the second circumferential main groove, and the plurality of second lug grooves.

Further, a plurality of shoulder lug grooves are provided at equal intervals in the tire circumferential direction in the shoulder portion of the tread, and each of the shoulder lug grooves connects the tread edge and the second circumferential main groove. As described above, the tires extend in the tire width direction. A plurality of shoulder blocks are partitioned in the tire circumferential direction by the tread edge, the second circumferential main groove, and the plurality of shoulder lug grooves.
JP 2004-58792 A

  By the way, a heavy load acts on the heavy duty pneumatic tire in a normal use state, and the deformation amount of the blocks (the center block, the second block, the shoulder block) during rolling of the heavy duty pneumatic tire is It ’s a big one. Therefore, in the heavy-duty pneumatic tire, if the block is cut by a road surface projection or the like, block tear (block chipping) of the block is likely to occur, and it is difficult to improve block tear resistance. become. On the other hand, when the rigidity of the block in the tire circumferential direction is increased by increasing the size of the block in order to suppress the occurrence of block tear in the block, the length of the block in the tire circumferential direction becomes longer. Heel and toe wear easily occurs, making it difficult to improve uneven wear resistance. In order to suppress the occurrence of block tear in the block, there is a method using a tread rubber having extremely high cut resistance as a constituent material of the tread. However, heat resistance is lowered, which is not practical.

  That is, in the heavy duty pneumatic tire, there is a problem that it is not easy to achieve both improvement in block tear resistance and improvement in uneven wear resistance. In recent years, the above-mentioned problem is being improved by various improvements for the shoulder block, but the above-mentioned problem is not sufficiently improved for the second block.

  Therefore, an object of the present invention is to provide a heavy-duty pneumatic tire having a novel configuration that can sufficiently improve the above-described problems with respect to the second block.

  A first feature of the present invention (feature of the invention described in claim 1) is a heavy duty pneumatic tire having a block pattern on a tread, and is provided so as to sandwich a tire equator line between the tread, and in a tire circumferential direction. A pair of first circumferential main grooves each having a predetermined groove depth, and a pair of the first circumferential main grooves sandwiched between the treads and extending in the tire circumferential direction. A pair of second circumferential grooves, each extending and having a predetermined groove depth, and adjacent to each other in the first circumferential direction, provided adjacent to the tread at intervals along the tire circumferential direction. Adjacent to a plurality of second lug grooves that extend in the tire width direction so as to connect the groove and the second circumferential main groove, and have a wall surface spread angle of 10 degrees or more and 15 degrees or less, respectively. The first circumferential direction A groove, the second circumferential main groove, and the plurality of second lug grooves are partitioned along the tire circumferential direction, and the ratio of the maximum length in the tire circumferential direction to the maximum width in the tire width direction is 1. A plurality of second blocks that are 5 or more and 1.9 or less, and provided at the bottom of each of the second lug grooves, each of which has a circular cross section in the longitudinal direction, and each has a maximum height. And a tie bar connecting a pair of adjacent second blocks that is 20% or more and 30% or less of the predetermined groove depth.

  Here, the expansion angle of the wall surface of each of the second lug grooves is set to 10 degrees or more. When the expansion angle of the wall surface is less than 10 degrees, the length of the second block in the tire circumferential direction is increased. This is because the heel and toe wear of the second block cannot be sufficiently suppressed. On the other hand, the expansion angle of the wall surface of each of the second drag grooves is set to 15 degrees or less, when the expansion angle of the wall surface exceeds 15 degrees, the volume of the second drag groove is insufficient after the middle stage of tread wear, This is because traction performance and wet performance deteriorate.

  In addition, the ratio of the maximum length in the tire circumferential direction to the maximum width in the tire width direction in each of the second blocks is 1.5 or more, respectively. The ratio of the maximum length in the tire circumferential direction is less than 1.5. This is because the rigidity of the second block in the tire circumferential direction cannot be sufficiently increased. On the other hand, the ratio of the maximum length in the tire circumferential direction to the maximum width in the tire width direction in each of the second blocks is 1.9 or less, respectively, because the ratio of the maximum length in the tire circumferential direction is 1.9. This is because if it exceeds, the length of the second block in the tire circumferential direction becomes long, and the occurrence of heel and toe wear of the second block cannot be sufficiently suppressed.

  Furthermore, the reason why the maximum height of each tie bar is set to 20% or more of the predetermined groove depth is that when the maximum height is less than 20% of the predetermined groove depth, the second block is deformed. It is because the effect | action which suppresses is not fully exhibited. On the other hand, the maximum height of each of the tie bars is set to 30% or less of the predetermined groove depth when the maximum height exceeds 30% of the predetermined groove depth. This is because there is a concern that the volume of the second lug groove is insufficient and the traction performance and the wet performance are deteriorated.

  According to the first feature, the ratio of the maximum length in the tire circumferential direction to the maximum width in the tire width direction in each of the second blocks is 1.5 or more, and the maximum height of each of the tie bars is respectively Since it is 20% or more of the predetermined groove depth, the rigidity of the second block in the tire circumferential direction can be sufficiently increased, and the effect of suppressing the deformation of the second block by the tie bar is sufficiently exhibited. The Thereby, generation | occurrence | production of the block tear of the said 2nd block can fully be suppressed.

  Further, the divergence angle of the wall surface of each of the second lug grooves is 10 degrees or more, and the ratio of the maximum length in the tire circumferential direction to the maximum width in the tire width direction in each of the second blocks is 1.9. Since it is the following, generation | occurrence | production of the heel and toe wear of the said 2nd block can fully be suppressed.

  Further, the spread angle of the wall surface of each second lug groove is 15 degrees or less, and the maximum height of each tie bar is 30% or less of the predetermined groove depth. In this case, the volume of the second lug groove can be kept sufficiently, and the deterioration of the traction performance and the wet performance can be suppressed. In particular, since the cross section in the longitudinal direction of each tie bar has an arc shape, the tie bar can be gradually exposed to the tread surface after the middle stage of tread wear, and the traction performance and wet performance are drastically increased. Decline can be prevented.

  According to a second feature of the present invention (a feature of the invention described in claim 2), in addition to the first feature, chamfering is formed at at least one corner portion on the tread edge side in each of the second blocks. The chamfer drop amount in each of the second blocks is 0.5 mm or more and 1.5 mm or less, respectively.

  According to the first or second aspect of the present invention, the occurrence of block tear of the second block and the occurrence of heel and toe wear of the second block can be sufficiently suppressed. It is possible to easily achieve both improved block tear and improved uneven wear resistance. In particular, according to the second aspect of the present invention, since the occurrence of heel and toe wear of the second block can be effectively suppressed, the uneven wear resistance of the second block can be further improved.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  Here, FIG. 1 is a plan development view of a part of a tread in a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part of the embodiment of the present invention. 3 (a) is a view taken along line AA in FIG. 2, FIG. 3 (b) is a view taken along line BB in FIG. 2, and FIG. FIG. 3 is a view taken along the line CC in FIG. 2. In the drawings, “L” indicates the left direction, and “R” indicates the right direction.

  As shown in FIG. 1, a heavy-duty pneumatic tire 1 according to an embodiment of the present invention is used for heavy-duty vehicles such as trucks and buses, and has a tread 3 having a block pattern. And the specific structure of the tread 3 of the pneumatic tire 1 for heavy loads is as follows.

  That is, a pair of first circumferential main grooves 5 (a first circumferential main groove 5 on the left side and a first circumferential main groove 5 on the right side) sandwich the tire equator line S near the center of the tread 3. Each of the first circumferential main grooves 5 extends in the tire circumferential direction C. Further, a pair of second circumferential main grooves 7 (a second circumferential main groove 7 on the left side and a second circumferential main groove 7 on the right side) on the left and right shoulder portions of the tread 3 are a pair of first circumferential directions. The second circumferential main grooves extend in the tire circumferential direction C so as to sandwich the main groove 5. Here, each of the first circumferential main grooves 5 and each of the second circumferential main grooves 7 has a predetermined groove depth h1 (see FIG. 3B). Further, a circumferential narrow groove 9 is provided at the center of the tread 3 so as to overlap the tire equator line S. The circumferential narrow groove 9 extends in a zigzag shape in the tire circumferential direction C.

  Note that a plurality of protrusions 11 that prevent biting of stones or the like are provided at intervals in the tire circumferential direction C at the bottom of each first circumferential main groove 5.

  A plurality of center lug grooves 13 are provided at equal intervals along the tire circumferential direction C in the center of the tread 3, and each center lug groove 13 crosses the circumferential narrow groove 9 and is located on the left side. The first circumferential main groove 5 and the first circumferential main groove 5 on the right side extend in the tire width direction W so as to be lowered downward in plan view. A plurality of left center blocks 15 are partitioned along the tire circumferential direction C by the left first circumferential main groove 5, the circumferential narrow grooves 9, and the plurality of left center lug grooves 13. Similarly, a plurality of right center blocks 15 are partitioned along the tire circumferential direction C by the right first circumferential main groove 5, the circumferential narrow groove 9, and the plurality of right center lug grooves 13. Each center block 15 is provided with a sipe 17.

  A plurality of second lug grooves 19 (a plurality of left-side second lug grooves 19 and a plurality of right-side second lug grooves 19) are provided at equal intervals along the tire circumferential direction C on both the left and right sides of the central portion of the tread 3. Each left-side second lug groove 19 extends to the right in plan view in the tire width direction W so as to connect the second circumferential main groove 7 on the left side and the first circumferential main groove 5 on the left side. Each right-side second lug groove 19 extends to the right in plan view in the tire width direction W so as to connect the right-side second circumferential main groove 7 and the right-side first circumferential main groove 5. A plurality of left-side second blocks 21 are partitioned along the tire circumferential direction C by the left-side second circumferential main groove 7, the left-side first circumferential main groove 5, and the plurality of left-side second lug grooves 19. . Similarly, a plurality of right second blocks 21 are partitioned along the tire circumferential direction C by the right second circumferential main groove 7, the right first circumferential main groove 5, and the plurality of right second lug grooves 19. The Each second block 21 is provided with a sipe 23.

  As shown in FIG.1 and FIG.3 (c), the tie bar 25 which connects a pair of 2nd block 21 adjacent to the tire circumferential direction C is provided in the bottom part of each second lug groove | channel 19, respectively, The cross sections in the longitudinal direction of the second lug grooves 19 each have an arc shape having a single radius of curvature r.

  As shown in FIG. 1, a plurality of shoulder lug grooves 27 (a plurality of left-side shoulder lug grooves 27 and a plurality of right-side shoulder lug grooves 27) are provided along the tire circumferential direction C in the left and right shoulder portions of the tread 3. The left shoulder lug grooves 27 are provided at equal intervals, and extend in the tire width direction W so as to connect the left tread edge E and the left second circumferential main groove 7 respectively. Each right shoulder lug groove 27 extends in the tire width direction W so as to connect the right tread edge E to the right second circumferential main groove 7. A plurality of left shoulder blocks 29 are partitioned along the tire circumferential direction C by the left tread edge E, the left second circumferential main groove 7 and the plurality of left shoulder lug grooves 27. Similarly, a plurality of right shoulder blocks 29 are partitioned along the tire circumferential direction C by the right tread edge E, the right second circumferential main groove 7 and the plurality of right shoulder lug grooves 27. Each shoulder block 29 is provided with a sipe 31.

  Next, a more specific configuration of the second lug groove 19, the second block 21, and the tie bar 25, which are the main parts of the embodiment of the present invention, will be described.

  As shown in FIGS. 2 and 3A, the spread angle θ of the wall surface 19a of each second lug groove 19 is 10 degrees or more and 15 degrees or less, respectively. Here, the reason why the expansion angle θ of the wall surface 19a of each second lug groove 19 is 10 degrees or more is that when the expansion angle θ of the wall surface 19a is less than 10 degrees, the length of the second block 21 in the tire circumferential direction C is as follows. This is because the heel and toe wear of the second block 21 cannot be sufficiently suppressed. On the other hand, the expansion angle θ of the wall surface 19a of each second lug groove 19 is set to 15 degrees or less. When the expansion angle θ of the wall surface 19a exceeds 15 degrees, the volume of the second drag groove 19 after the middle stage of the tread wear is increased. This is because the traction performance and the wet performance are deteriorated due to the shortage.

  2, the ratio (m / f) of the maximum length m in the tire circumferential direction C to the maximum width f in the tire width direction W in each second block 21 is 1.5 or more and 1. 9 or less. Here, the ratio (m / f) of the maximum length m in the tire circumferential direction C to the maximum width f in the tire width direction W in each second block 21 is 1.5 or more, respectively. This is because the rigidity of the second block 21 in the tire circumferential direction C cannot be sufficiently increased when the ratio of length m (m / f) is less than 1.5. On the other hand, the ratio (m / f) of the maximum length m in the tire circumferential direction C to the maximum width in the tire width direction W in each second block 21 is 1.9 or less, respectively. If the ratio (m / f) exceeds 1.9, the length of the second block 21 in the tire circumferential direction C increases, and the occurrence of heel and toe wear of the second block 21 cannot be sufficiently suppressed. It is.

  Further, as shown in FIGS. 2 and 3 (b), chamfers 33 are respectively formed in the acute corner portion on the tread edge E side and the acute corner portion on the tire equator line S side in the second block 21. The drop amount e of the chamfer 33 in each second block 21 is 0.5 mm or more and 1.5 mm or less, respectively. Here, the drop amount e of the chamfer 33 in each of the second blocks 21 is set to 0.5 mm or more. If the drop amount e of the chamfer 33 is less than 0.5 mm, the stepped portion of the second block 21 or kicking out This is because it becomes difficult to slip the portion, and the occurrence of heel and toe wear of the second block 21 cannot be effectively suppressed. The reason why the drop amount e of the chamfer 33 in each second block 21 is 1.5 mm or less is that when the drop amount e of the chamfer 33 exceeds 1.5 mm, the volume of the second block 21 decreases greatly. This is because the occurrence of heel and toe wear of the second block 21 cannot be effectively suppressed. In addition to the acute angle portion on the tread edge E side and the acute angle portion on the tire equator line S side in the second block 21, the obtuse angle portion on the tread edge E side and the obtuse angle on the tire equator line S side. A chamfer 33 may be formed on the portion.

  Further, the maximum height j of each tie bar 25 is 20 which is a predetermined groove depth h of the first circumferential main groove 5 and the second circumferential main groove 7 (in other words, the height of the second block 21). % Or more and 30% or less. Here, the maximum height j of each tie bar 25 is set to 20% or more of the predetermined groove depth h. If the maximum height j is less than 20% of the predetermined groove depth h, the second block It is because the effect | action which suppresses a deformation | transformation of 21 is not fully exhibited. On the other hand, the maximum height j of each tie bar 25 is set to 30% or less of the predetermined groove depth h when the maximum height j exceeds 30% of the predetermined groove depth h. This is because the volume of the second lug groove 19 is insufficient thereafter, and there is a concern that the traction performance and the wet performance may deteriorate.

  Then, the effect | action and effect of embodiment of this invention are demonstrated.

  The ratio (m / f) of the maximum length m in the tire circumferential direction C to the maximum width f in the tire width direction W in each second block 21 is 1.5 or more, respectively, and the maximum height j of each tie bar 25 is Since each is 20% or more of the predetermined groove depth h, the rigidity of the second block 21 in the tire circumferential direction C can be sufficiently increased, and the effect of suppressing the deformation of the second block 21 by the tie bar 25 is sufficiently exerted. Is done. Thereby, generation | occurrence | production of the block tear (block missing) of the 2nd block 21 can fully be suppressed.

  Further, the spread angle θ of the wall surface 19a of each second lug groove 19 is 10 degrees or more, and the ratio of the maximum length m in the tire circumferential direction C to the maximum width f in the tire width direction W in each second block 21 ( m / f) is 1.9 or less, and the chamfer 33 drop amount in each second block 21 is 0.5 mm or more and 1.5 mm or less, so that the heel and toe of the second block 21 is The occurrence of wear can be sufficiently and effectively suppressed.

  Furthermore, since the spread angle θ of the wall surface 19a of each second lug groove 19 is 15 degrees or less and the maximum height j of each tie bar 25 is 30% or less of the predetermined groove depth h, tread wear Even in the middle period and thereafter, the volume of the second drag groove 19 can be kept sufficiently, and deterioration of the traction performance and the wet performance can be suppressed. In particular, since the cross section in the longitudinal direction of each tie bar 25 has an arc shape having a single radius of curvature r, the tie bar 25 can be gradually exposed on the surface of the tread 3 after the middle period of wear of the tread. A sudden drop in traction performance and wet performance can be prevented.

  As described above, according to the embodiment of the present invention, the occurrence of block tear of the second block 21 can be sufficiently suppressed, and the occurrence of heel and toe wear of the second block 21 can be sufficiently and effectively suppressed. Therefore, with respect to the second block 21, it is possible to easily achieve both improved block tear resistance and improved uneven wear resistance.

  In addition, this invention is not restricted to description of the above-mentioned embodiment, In addition, it can implement in a various aspect. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

  Examples of the present invention will be described.

  The heavy load pneumatic tire 1 according to the embodiment is manufactured as an invention, and the heavy load pneumatic tire (not shown) according to a comparative example is manufactured as a comparative product. Then, a field test was performed on the inventive product and the comparative product, and the block tear resistance and uneven wear resistance on the second block were evaluated based on the test results. Note that the heavy duty pneumatic tire according to the comparative example is a known pneumatic tire disclosed in Japanese Patent Application Laid-Open No. 2004-58792.

In the field test, 30% of the expressway (average speed 90km / h) and 30% of the general road (average speed 50km / h) with the invention and comparative products mounted on the drive shaft of the semi-trailer (2D + 2-axle trailer dump), respectively. ) At a rate of 70%, and when 30,000 km, the block tear resistance of the second block is evaluated by the number of block tears (block missing) in the second block, and the kick side (heel) in the second block is evaluated. Side wear) and the stepping side (toe side) level difference (heel toe level difference) is evaluated for uneven wear resistance with respect to the second block. Table 1 summarizes the test results of the block tear resistance and uneven wear resistance regarding the second block. In addition, with the comparative product as a control (100), a larger numerical value indicates higher block tear resistance and uneven wear resistance.

  That is, as shown in Table 1, the inventive product was able to obtain a higher block tear property than the comparative product while ensuring the same partial wear resistance as the comparative product for the second block.

It is a plane development view of a part of a tread in a pneumatic tire according to an embodiment of the present invention. It is an enlarged view of the principal part of embodiment of this invention. 3A is a view taken along the line AA in FIG. 2, FIG. 3B is a view taken along the line BB in FIG. 2, and FIG. FIG. 3 is a view taken along the line CC in FIG. 2.

Explanation of symbols

1 Pneumatic tire for heavy load 3 Tread 5 First circumferential main groove 7 Second circumferential main groove 19 Second lug groove 19a Wall surface 21 Second block 25 Tie bar

Claims (2)

In a heavy duty pneumatic tire with a block pattern on the tread,
A pair of first circumferential main grooves provided in the tread so as to sandwich the tire equator line, extending in the tire circumferential direction and having a predetermined groove depth;
A pair of second circumferential grooves provided in the tread so as to sandwich the pair of first circumferential main grooves, respectively extending in the tire circumferential direction and having the predetermined groove depth;
The tread is provided at intervals along the tire circumferential direction, and extends in the tire width direction so as to connect the adjacent first circumferential main groove and the second circumferential main groove. A plurality of second lug grooves each having a divergence angle of 10 degrees or more and 15 degrees or less;
The first circumferential main groove, the second circumferential main groove, and the plurality of second lug grooves that are adjacent to each other are partitioned along the tire circumferential direction, and the tire circumferential direction relative to the maximum width in the tire width direction is divided. A plurality of second blocks each having a maximum length ratio of 1.5 or more and 1.9 or less;
Provided at the bottom of each of the second drag grooves, the cross-section in the longitudinal direction has an arc shape, and the maximum height is 20% or more and 30% or less of the predetermined groove depth, respectively. A tie bar connecting a pair of adjacent second blocks;
A heavy-duty pneumatic tire characterized by comprising:   A chamfer is formed in at least one corner portion on the tread edge side in each second block, and the chamfer drop amount in each second block is 0.5 mm or more and 1.5 mm or less, respectively. The heavy duty pneumatic tire according to claim 1.

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