JP5595863B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy-duty pneumatic tire, and more particularly to a heavy-duty pneumatic tire having on-ice performance, on-snow performance, uneven wear resistance performance, and steering stability performance.

  Heavy duty pneumatic tires used for trucks and buses, especially for studless tires, in order to improve the performance on ice and snow on snow and snow, in order to improve the performance on snow and snow, by arranging many grooves and sipes, It is common to improve the drainage effect, the snow drainage effect, and the edge effect of receiving water and snow in the groove. On the other hand, if a large number of grooves and sipes are arranged, the rigidity of the block composed of the circumferential groove and the width direction groove is lowered, and uneven wear resistance performance and steering stability on the dry road surface are lowered. For this reason, it is a subject to arrange | position block shape, a sipe, and a groove | channel in the optimal combination, and to make compatible on-ice performance and on-snow performance, uneven wear-proof performance, and steering stability.

  Conventionally, a block is constituted by a circumferential main groove extending in the tire circumferential direction and a width direction groove extending in the tire width direction so as to intersect the circumferential main groove, and the sipe is formed on the tread surface of the block. 2. Description of the Related Art A heavy-duty pneumatic tire provided with a heavy-duty pneumatic tire that improves the running performance on snowy and snowy road surfaces and ensures block rigidity is known.

  For example, in the heavy duty pneumatic tire (pneumatic tire) described in Patent Document 1, four circumferential main grooves are formed, and three or more sipes along the width direction grooves are formed on the block. Yes. And the sipe of the tire circumferential direction both outer side is made into a closed sipe among the sipe, and the sipe located between closed sipe is formed as an open sipe. As a result, the edge component is increased to improve the running performance on the road surface on ice and snow. Moreover, the surface of the sipe is formed in a bent shape, the sipe depth is ½ or more of the circumferential main groove, and the sipe length is ½ or more of the block width. Thereby, the rigidity of the block is ensured.

  Further, for example, in the heavy duty pneumatic tire described in Patent Document 2, four circumferential main grooves are formed, and three or more sipes along the width direction grooves are formed in the block. Has been. At least one of the sipes is formed as a one-side open sipe that is connected to the circumferential main groove on one side. As a result, the edge component is increased to improve the running performance on the road surface on ice and snow. Moreover, the width direction grooves are offset in the circumferential direction for each block row. This ensures the durability and wear resistance of the block.

JP 2006-103464 A JP 2004-098926 A

  However, in the conventional heavy-duty pneumatic tire, the circumferential main groove has a large angle with respect to the tire circumferential direction (direction parallel to the tire equator line), and this angle is reversed at the intersection with the widthwise groove. The so-called zigzag shape is formed. For this reason, since the circumferential main groove has a large angle with respect to the rolling direction of the pneumatic tire, the drainage effect and the snow drainage effect in the circumferential main groove are reduced, and the performance on ice and the performance on snow. Will be hindered.

  The present invention has been made in view of the above, and an object thereof is to provide a heavy-duty pneumatic tire capable of achieving both on-ice performance and on-snow performance, uneven wear resistance performance, and steering stability. .

  In order to achieve the above object, in the heavy duty pneumatic tire according to the present invention, four or more land portions are provided at an angle of 5 degrees or less with respect to the tire circumferential direction and adjacent to the tire width direction. A circumferential main groove forming a row and three or more land portion rows near the tire equator line are divided in the tire circumferential direction to form a plurality of inland portions, and the adjacent circumferential main grooves are It is characterized in that it is provided with a secondary groove that is bent while being connected and a closed sipe that is provided with both ends closed on the tread surface of the inland portion.

  According to this heavy-duty pneumatic tire, by providing four or more circumferential main grooves of 5 degrees or less (substantially 0 degrees) with respect to the tire circumferential direction, water and snow between the tire tread and the road surface can be prevented. The drainage effect and snow drainage effect received in the groove can be improved. In addition, the land portion row formed by the circumferential main groove is divided in the tire circumferential direction by the sub groove to form the inland portion, and the edge effect is improved by providing a closed sipe on the tread surface of this inland portion it can. For this reason, the performance on ice and the performance on snow which are braking performance can be improved. In addition, a decrease in the rigidity of the inland portion is suppressed by the sub-grooves that are bent so as to connect adjacent circumferential main grooves and the closed sipes. For this reason, it is possible to suppress a decrease in uneven wear resistance performance and steering stability performance on a dry road surface.

  In the heavy-duty pneumatic tire according to the present invention, two crossings provided across the tire width direction in a mode in which the inland portion is divided in the tire circumferential direction to form three small land portions. A sipe is provided, and the closed sipe is provided in each of the small land portions.

  According to this heavy duty pneumatic tire, the edge effect can be improved by crossing sipes, and the performance on ice and the performance on snow can be further improved. Moreover, an edge effect can be obtained in each small land portion by providing the closed sipes on the treads of the divided small land portions.

  In the heavy-duty pneumatic tire according to the present invention, the inland portions adjacent in the tire circumferential direction are formed to have overlapping portions that overlap in the tire width direction.

  According to this heavy-duty pneumatic tire, the inland portions are reinforced mutually by the overlapping portions, and therefore, it is possible to suppress a decrease in uneven wear resistance.

  The heavy duty pneumatic tire according to the present invention is characterized in that the inland portions adjacent in the tire width direction are line-symmetrically related to a symmetry axis extending in the tire circumferential direction.

  According to this heavy duty pneumatic tire, there is no directionality in the rolling direction, and steering stability performance can be ensured.

  In the heavy duty pneumatic tire according to the present invention, the maximum width W in the tire width direction of the inland portion is 0.75 ≦ W / L ≦ 0 with respect to the maximum length L in the tire circumferential direction of the inland portion. .80 range.

  When the W / L is less than 0.75, the inland portion has a shape that is long in the tire circumferential direction, the rigidity in the tire width direction is reduced, and uneven wear resistance performance and steering stability performance are reduced. In addition, since the edge component and the groove component of the inland portion with respect to the tire circumferential direction within the contact surface to the road surface are reduced, the performance on ice and the performance on snow are reduced. On the other hand, when W / L exceeds 0.80, the inland portion has a shape that is long in the tire width direction, the rigidity in the tire circumferential direction is reduced, and the edge effect is reduced. Performance will be degraded. For this reason, it is preferable that the maximum width W in the tire width direction of the inland portion is set in a range of 0.75 ≦ W / L ≦ 0.80 with respect to the maximum length L in the tire circumferential direction of the inland portion. .

  In the heavy-duty pneumatic tire according to the present invention, the maximum groove width Wd of the portion extending in the tire width direction of the sub-groove is 0.10 relative to the maximum length L in the tire circumferential direction of the inland portion. ≦ Wd / L ≦ 0.15 is set.

  When Wd / L is less than 0.10, a sufficient snow column shear force cannot be secured, and the performance on snow is reduced. On the other hand, when Wd / L exceeds 0.15, the edge component and the groove component of the inland portion with respect to the tire circumferential direction within the contact surface with respect to the road surface are decreased, and thus the performance on ice and the performance on snow are deteriorated. For this reason, the maximum groove width Wd of the portion extending in the tire width direction of the sub-groove is set in a range of 0.10 ≦ Wd / L ≦ 0.15 with respect to the tire circumferential direction maximum length L of the inland portion. It is preferable that

  The heavy-duty pneumatic tire according to the present invention can achieve both on-ice performance and on-snow performance, uneven wear resistance performance and steering stability.

FIG. 1 is a plan view showing a part of a tread portion of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of a heavy duty pneumatic tire according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  In the following description, the tire radial direction means a direction orthogonal to the rotational axis of the pneumatic tire, the tire radial inner side is the side toward the rotational axis in the tire radial direction, and the tire radial outer side is in the tire radial direction. The side away from the rotation axis. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction is the side facing the tire equator plane in the tire width direction, and the outer side in the tire width direction is separated from the tire equator plane in the tire width direction. Say the side.

  1 is a plan view showing a part of a tread portion of a heavy duty pneumatic tire according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is an embodiment of the present invention. It is a graph which shows the result of the performance test of the pneumatic tire concerning.

  The heavy-duty pneumatic tire 1 has a tread portion 2 that is formed of an elastic rubber member and forms an outline of the pneumatic tire 1 on the outermost side in the tire radial direction. Further, the tread portion 2, that is, the tread surface 21 that comes into contact with the road surface when a vehicle (not shown) on which the pneumatic tire 1 is mounted travels, has four or more (this embodiment) extending in the tire circumferential direction. In the embodiment, four circumferential main grooves 3 are provided. In the tread portion 2, five or more (5 in the present embodiment) land portion rows 4 extending in the tire circumferential direction are formed by the circumferential main grooves 3.

  The three land portion rows 4 near the tire equator line C are provided with a plurality of sub-grooves 5 that divide the land portion row 4 in the tire circumferential direction. A land portion 41 is formed in the land portion row 4 by the sub-groove 5. As shown in FIG. 2, the secondary groove 5 is provided to bend in the middle while connecting the circumferential main grooves 3 adjacent in the tire width direction. Specifically, the sub-grooves 5 extend at an angle of 0 ° to 15 ° with respect to the tire width direction and have a width-direction groove 51 having one end opened in the circumferential main groove 3 and 0 with respect to the tire circumferential direction. It is comprised with the circumferential direction groove | channel 52 which connects the other end of each width direction groove | channel 51, extending at the angle of 10 degree | times or more, and is bent and provided in the substantially Z shape as a whole. Moreover, since the subgroove 5 is provided in the same shape in the tire circumferential direction, the inland portion 41 adjacent in the tire circumferential direction is formed in the same shape. 1 and 2 are provided with a bent connection between the width direction groove 51 and the circumferential groove 52, but the connection between the width direction groove 51 and the circumferential groove 52 is curved. Then, it may be bent substantially in an S shape. Moreover, although the inland part 41 shown in FIG. 1 is formed in the three land part row | line | columns 4 near the tire equator line C (between the circumferential direction main grooves 3), the tire width direction of the circumferential direction main groove 3 is shown. The outer land portion row 4 may be formed.

  Here, the circumferential main groove 3 is provided with an angle of 5 degrees or less (substantially 0 degrees) with respect to the tire circumferential direction. Specifically, the angle of 5 degrees or less is an angle with respect to the tire circumferential direction on the side surface in the tire width direction of the inland portion 41 formed by the auxiliary groove 5. And in this Embodiment, the circumferential direction main groove 3 is provided so that the angle of the tire width direction side surface of the inland part 41 adjacent along a tire circumferential direction may reverse alternately.

  The tread surface 21 of the inland portion 41 is provided with a closed sipe 6 whose both ends are closed without opening to the circumferential main groove 3 and the sub-groove 5. The closed sipe 6 has a groove depth shallower than that of the circumferential main groove 3, extends in the tire width direction, and is provided to meander in a wavy manner. The closed sipes 6 may be provided linearly in the tire width direction.

  In this heavy-duty pneumatic tire 1, by providing four or more circumferential main grooves 3 of 5 degrees or less (substantially 0 degrees) with respect to the tire circumferential direction, water or snow between the tread 21 and the road surface is prevented. The drainage effect and snow drainage effect received in the groove can be improved. Further, the land portion row 4 formed by the circumferential main groove 3 is divided in the tire circumferential direction by the sub groove 5 to form the inland portion 41, and the closed sipe 6 is provided on the tread 21 of the inland portion 41. As a result, the edge effect can be improved. For this reason, it is possible to improve on-ice performance and on-snow performance, which are braking performance on an icy road surface and a snowy road surface. Moreover, the rigidity of the inland portion 41 is improved by the sub-groove 5 bent in a substantially Z shape (or substantially S shape) so as to connect the adjacent circumferential main grooves 3 and the closed sipes 6. Reduction is suppressed. For this reason, it is possible to suppress a decrease in uneven wear resistance performance and steering stability performance on a dry road surface.

  Further, the heavy duty pneumatic tire 1 according to the present embodiment is provided with two linear crossing sipes 7 that traverse in the tire width direction in the inland portion 41. The transverse sipe 7 extends at an angle of 0 degrees or more and 15 degrees or less with respect to the tire width direction, and has a groove depth shallower than the circumferential main groove 3. The cross sipe 7 forms a small land portion 411 that is divided into three in the tire circumferential direction in the inland portion 41. The closed sipes 6 are provided on the treads of the small land portions 411.

  According to this configuration, the edge effect can be improved by the crossing sipe 7, and the performance on ice and the performance on snow can be further improved. Moreover, by providing the closed sipes 6 on the treads 21 of the divided small land portions 411, an edge effect can be obtained in each small land portion 411. In addition, the number of the small land portions 411 in which the inland portions 41 are divided by the crossing sipe 7 is preferably three in terms of suppressing a decrease in rigidity of the inland portions 41.

  In the heavy-duty pneumatic tire 1 according to the present embodiment, overlapping portions 41 </ b> A that overlap in the tire width direction are formed in the inland portions 41 that are adjacent in the tire circumferential direction with the sub-groove 5 interposed therebetween. This overlapping portion 41 </ b> A is formed by the sub-groove 5, and corresponds to the small land portions 411 on both sides in the tire circumferential direction formed by being divided by the transverse sipe 7 in the inland portion 41.

  According to this structure, since the inland part 41 is mutually reinforced by the overlapping part 41A, it is possible to suppress a decrease in uneven wear resistance.

  Further, in the heavy-duty pneumatic tire 1 according to the present embodiment, each inland portion 41 adjacent in the tire width direction with the circumferential main groove 3 interposed therebetween has a symmetrical axis (tire equator line) extending in the tire circumferential direction. And an axis that passes through the center of the circumferential main groove 3). This line-symmetric shape is formed by the sub-groove 5. In addition, the inland part 41 formed in line symmetry is formed with a phase shifted in the tire circumferential direction.

  According to this configuration, there is no directionality in the rolling direction, and steering stability performance can be ensured.

  Further, in the heavy duty pneumatic tire 1 according to the present embodiment, the maximum width W in the tire width direction of the inland portion 41 is 0.75 ≦ W / w with respect to the maximum length L in the tire circumferential direction of the inland portion 41. The range is set to L ≦ 0.80. That is, the ratio of the maximum width W in the tire width direction of the inland portion 41 to the maximum length L in the tire circumferential direction of the inland portion 41 is set in a range of 75 [%] to 80 [%].

  When the ratio of the maximum width W in the tire width direction of the inland portion 41 to the maximum length L in the tire circumferential direction of the inland portion 41 is less than 75%, the inland portion 41 is long in the tire circumferential direction. Thus, the rigidity in the tire width direction is reduced, and uneven wear resistance performance and steering stability performance are reduced. Moreover, since the edge component and the groove component of the inland portion 41 with respect to the tire circumferential direction within the contact surface to the road surface are reduced, the performance on ice and the performance on snow are reduced. On the other hand, if it exceeds 80%, the inland portion 41 has a shape that is long in the tire width direction, the rigidity in the tire circumferential direction is reduced, and the edge effect is reduced. It will decline. For this reason, the ratio of the tire width direction maximum width W of the inland portion 41 to the tire circumferential direction maximum length L of the inland portion 41 is set in a range of 75 [%] to 80 [%]. Is preferred.

  Further, in the heavy load pneumatic tire 1 according to the present embodiment, the maximum groove width Wd of the portion extending in the tire width direction of the auxiliary groove 5 with respect to the tire circumferential direction maximum length L of the inland portion 41 is: The range is set to 0.10 ≦ Wd / L ≦ 0.15. That is, the ratio of the maximum groove width Wd of the portion extending in the tire width direction of the auxiliary groove 5 to the maximum length L in the tire circumferential direction of the inland portion 41 is in the range of 10% to 15%. Is set.

  When the ratio of the maximum groove width Wd of the portion extending in the tire width direction of the sub-groove 5 to the maximum length L in the tire circumferential direction of the inland portion 41 is less than 10%, snow column shear force (snow And the snow resistance of the snow column formed in the sub-groove 5 cannot be sufficiently secured, and the performance on snow is reduced. On the other hand, if it exceeds 15 [%], the edge component and the groove component of the inland portion 41 with respect to the tire circumferential direction within the contact surface to the road surface will decrease, leading to deterioration in performance on ice and on snow. Therefore, the ratio of the maximum groove width Wd of the portion extending in the tire width direction of the sub-groove 5 to the maximum length L in the tire circumferential direction of the inland portion 41 is in the range of 10 [%] to 15 [%]. It is preferable that it is set to.

  In this example, performance tests were performed on a plurality of types of pneumatic tires with different conditions, on ice performance on ice, on snow on snow, steering stability on dry road, and uneven wear resistance ( (See FIG. 3).

  In this performance test, a heavy duty pneumatic tire having a tire size of 275 / 80R22.5 is used. This heavy-duty pneumatic tire was assembled on a regular rim defined by JATMA, applied with a pneumatic pressure of 900 [kPa] regulated by JATMA, and mounted on a 2-D4 GVW 25-ton truck. The load was in a loaded state.

  In the evaluation method, the braking distance from 40 [km / h] is measured on the road surface on ice. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases. In terms of performance on snow, a braking distance from a speed of 40 km / h on the road surface on snow is measured. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases. Further, in the uneven wear resistance performance, a comparison is made of the difference in wear amount between the maximum wear portion and the minimum wear portion in one block when traveling at 5000 [km]. Then, based on this comparison result, index evaluation is performed with the conventional example as a reference (100). This evaluation is preferable as the numerical value increases. Moreover, in the steering stability performance, feeling on a dry road surface is evaluated, and index evaluation is performed with the conventional example as a reference (100). This evaluation is preferable as the numerical value increases.

  In the conventional heavy-duty pneumatic tire, there are a mixture of a bent sub-groove and a bent non-bent straight tire, and W / L = 83 [%] and Wd / L = 9 [%]. Is set. The heavy duty pneumatic tire of the comparative example has three circumferential main grooves, and is set to W / L = 90 [%] and Wd / L = 12 [%]. The heavy duty pneumatic tires of Examples 1 to 12 are the number of circumferential main grooves, the angle of the circumferential main grooves with respect to the tire circumferential direction, the shape of the sub-groove, the transverse sipe and the closed sipe, and W / L. , Wd / L are optimized.

  As shown in the test results of FIG. 3, in the heavy-duty pneumatic tires of Examples 1 to 12, the performance on ice and the performance on snow are improved, and the deterioration of uneven wear resistance and steering stability performance is suppressed. I understand that.

  As described above, the heavy-duty pneumatic tire according to the present invention is suitable for achieving both on-ice performance and on-snow performance, uneven wear resistance performance and steering stability.

DESCRIPTION OF SYMBOLS 1 Heavy load pneumatic tire 2 Tread part 21 Tread surface 3 Circumferential main groove 4 Land part row 41 Middle land part 411 Small land part 41A Overlapping part 5 Sub groove 51 Width direction groove 52 Circumferential groove 6 Closed sipe 7 Transverse sipe C Tire Equatorial line W Maximum width in the tire width direction in the middle land Wd Maximum groove width in the secondary groove L Maximum length in the tire circumferential direction in the middle land area

Claims (4)

In heavy duty pneumatic tires that are studless tires,
4 or more extending in a straight line in the tire circumferential direction, and a circumferential main groove forming 5 or more land portion rows adjacent in the tire width direction;
All of the three or more land portions near the tire equator except for the outermost land portion row in the tire width direction are divided in the tire circumferential direction to form a plurality of inland portions, and the tire circumferential direction In each of the adjacent inland portions having overlapping portions that overlap in the tire width direction, the circumferential main grooves that are adjacent to each other extend at an angle of 0 degrees to 15 degrees with respect to the tire width direction. A plurality of sub-grooves constituted by a width direction groove having one end opened, and a circumferential groove extending at an angle of 0 degrees to 10 degrees with respect to the tire circumferential direction and connecting the other ends of the width direction grooves; ,
In a mode in which the inland portion is divided in the tire circumferential direction to form three small land portions, two are provided across the tire width direction at an angle of 0 degrees to 15 degrees with respect to the tire width direction. A transverse sipe extending and having a groove depth shallower than the circumferential main groove;
A closed sipe provided with both ends closed on the tread of each small land portion ,
The inland portion adjacent in the tire width direction between the circumferential main grooves is formed symmetrically with respect to an axis parallel to the tire equator line and passing through the center of the circumferential main groove, and in the tire circumferential direction. Of the three divided small land portions, one of the small land portions is formed with a phase shift in the tire circumferential direction by a distance in the tire circumferential direction, and the transverse sipe has one end thereof in the circumferential main direction. The inland portion that opens in the groove and faces the opening of one end of the width direction groove in the other inland portion adjacent in the tire width direction, and the transverse sipe forms the other end of the inland portion. A heavy duty pneumatic tire having an opening at the other end of the widthwise groove formed .   The closed sipe is disposed in the small land portion at two circumferential ends of the three small land portions divided in the tire circumferential direction, and five in the small land portion in the center. The heavy-duty pneumatic tire according to claim 1, wherein the closed sipe has at least two or more inflection points and has the longest length in the tire width direction although it is close to the transverse sipe. The maximum width W in the tire width direction of the inland portion is set in a range of 0.75 ≦ W / L ≦ 0.80 with respect to the maximum length L in the tire circumferential direction of the inland portion. The heavy-duty pneumatic tire according to claim 1 or 2 . The maximum groove width Wd of the portion extending in the tire width direction of the sub-groove is set in a range of 0.10 ≦ Wd / L ≦ 0.15 with respect to the maximum length L in the tire circumferential direction of the inland portion. The heavy-duty pneumatic tire according to any one of claims 1 to 3 , wherein the pneumatic tire is for heavy loads.

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