JP2009241882A - Heavy-duty pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make on-ice performance and on-snow performance and uneven wearing-resistance performance and driving stability compatible. <P>SOLUTION: The heavy-duty pneumatic tire is provided with: four or more circumferential main grooves 3 provided while forming an angle of 5° or less relative to a tire circumferential direction and forming five or more land part rows 4 adjacent in a tire width direction; a thin groove 5 forming an angle of 8° or less relative to a tire circumferential direction having shallower groove depth than the circumferential main groove 8 in the form that the three or more land part rows 4 close to a tire equator line C are divided in a tire width direction to form a thin land part row 41; a plurality of sub-grooves 6 provided so as to connect the adjacent circumferential main groove 3 and the thin groove 5 in the form that the thin land part row 41 is divided in the tire circumferential direction to form an intermediate land part 411; and an opening-closure sipe 7 provided on a step surface 21 of the intermediate land part 411 so as to close both ends. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 studless tires.In order to improve on-ice performance on snow and snow, and on snow, the number of grooves and sipes are arranged to increase the distance between the tread and the road. 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, a small block is formed by dividing the center of the block into two in the tire width direction by a circumferential sipe. And by the phase shift of a predetermined range of small blocks, the concentration rate of edge components is increased, and intermittent and peaky tangential force is obtained by repeating the dense and sparse edge components in the tire circumferential direction. In addition, heel and toe uneven wear is suppressed to a low level.

JP 2007-118704 A

  However, in the conventional heavy duty pneumatic tire, the block is divided by the circumferential sipe, so that the block rigidity can be secured, but on the other hand, since there are few grooves that make the drainage effect and snow removal effect, the performance on ice and on the snow The performance is not enough.

  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. In a mode in which a circumferential main groove forming a row and three or more land portion rows near the tire equator line are divided in the tire width direction to form a fine land portion row, 8 degrees or less with respect to the tire circumferential direction In the form of a narrow groove provided with a groove depth shallower than the circumferential main groove, and an inland portion obtained by dividing the narrow land portion row in the tire circumferential direction, the adjacent circumferential direction A plurality of sub grooves provided by connecting the main groove and the narrow groove, and a closed sipe 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 tread and the road surface are grooved. The drainage effect and snow drainage effect that can be received inside can be improved. Furthermore, the drainage effect which drains the water and snow between a tread surface and a road surface in a groove | channel and the snow drainage effect can be improved by the narrow groove which divides the land part row | line | column formed of the circumferential direction main groove. Furthermore, the edge effect is improved by forming the inland part by dividing the narrow land part row formed by the narrow groove in the tire circumferential direction by the secondary groove and providing a closed sipe on the tread surface of this inland part. it can. 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. In addition, the above-described closed sipes can suppress a decrease in the rigidity of the inland region. 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, the inland portion is divided in the tire circumferential direction to form two small land portions, and includes a transverse sipe provided across the tire width direction. In addition, the closed sipes are provided in 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 land portion rows 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 0.70 ≦ W / L ≦ 0 with respect to the maximum length L in the tire circumferential direction of the inland portion. .80 range.

  When W / L is less than 0.70, 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 and steering stability performance are reduced. Moreover, 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 deteriorated. 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 0.70 ≦ 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 in the tire circumferential direction of the sub-groove is 0.20 ≦ Wd / L ≦ with respect to the tire circumferential maximum length L of the inland portion. It is characterized by being set in the range of 0.25.

  If Wd / L is less than 0.20, a sufficient snow column shear force cannot be secured, and the on-snow performance decreases. On the other hand, if Wd / L exceeds 0.25, the edge component and the groove component of the inland portion 411 with respect to the tire circumferential direction within the contact surface 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 in the tire circumferential direction of the secondary groove is set in a range of 0.20 ≦ Wd / L ≦ 0.25 with respect to the maximum tire circumferential length L in the inland region. preferable.

  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.

  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 narrow grooves 5 that divide the land portion row 4 at the center in the tire width direction. In the land portion row 4, a narrow land portion row 41 is formed by the narrow groove 5. The narrow groove 5 has a groove depth shallower than that of the circumferential main groove 3, and the groove width is set in a range of 0.5 [mm] or more and 5 [mm] or less.

  Further, the narrow land portion row 41 is provided with a plurality of linear sub-grooves 6 that divide the narrow land portion row 41 in the tire circumferential direction. The sub-groove 6 extends at an angle of 0 ° to 15 ° with respect to the tire width direction, and is provided to connect the circumferential main groove 3 and the narrow groove 5. In the narrow land portion row 41, the inland portion 411 is formed by the sub-groove 6.

  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 411 formed by the auxiliary groove 6. 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 411 adjacent along a tire circumferential direction may reverse alternately.

  The narrow groove 5 is provided with an angle α of 8 degrees or less with respect to the tire circumferential direction. Specifically, the angle α of 8 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 411 formed by the auxiliary groove 6. And in this Embodiment, the tire width direction side surface bent so that the center of the tire circumferential direction of the inland part 411 may protrude toward the edge part side of the auxiliary groove 6 may be opposed to the edge part of the auxiliary groove 6. The angle is 8 degrees or less. And in the two narrow land part row | line | columns 41 divided | segmented by the narrow groove 5 in one land part row | line | column 4, the angle of the tire width direction side surface of the inland part 411 adjacent along a tire circumferential direction is reversed alternately. Is provided with a narrow groove 5.

  The tread surface 21 of the inland portion 411 is provided with a closed sipe 7 whose both ends are closed without opening to the circumferential main groove 3 and the narrow groove 5. The closed sipe 7 has a groove depth shallower than that of the circumferential main groove 3, extends in the tire width direction, and is provided in a wavy manner. The closed sipes 7 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. Furthermore, the narrow groove 5 that divides the land portion row 4 formed by the circumferential main groove 3 can improve the drainage effect and the snow drainage effect of receiving water and snow between the tread surface 21 and the road surface in the groove. Furthermore, the narrow land portion row 41 formed by the narrow grooves 5 is divided in the tire circumferential direction by the sub-grooves 6 to form the inland portions 411, and the closed sipes 7 are provided on the treads 21 of the inland portions 411. 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. In addition, the closed sipe 7 suppresses a decrease in rigidity of the inland portion 411. 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 a linear crossing sipe 8 that crosses in the tire width direction in the inland portion 411. The transverse sipe 8 extends at an angle of not less than 0 degrees and not more than 15 degrees with respect to the tire width direction, and has a groove depth shallower than that of the circumferential main groove 3. The cross sipe 8 forms a small land portion 4111 that is divided into two in the tire circumferential direction in the inland portion 411. The closed sipes 7 are provided on the treads of the small land portions 4111.

  According to such a configuration, the edge effect can be improved by the crossing sipe 8, and the performance on ice and the performance on snow can be further improved. Moreover, by providing the closed sipes 7 on the treads 21 of the divided small land portions 4111, an edge effect can be obtained in each small land portion 4111. Note that the number of small land portions 4111 in which the inland portions 411 are divided by the crossing sipe 8 is preferably the above two in terms of suppressing a decrease in rigidity of the inland portions 411.

  Further, in the heavy-duty pneumatic tire 1 according to the present embodiment, each land portion row 4 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 narrow grooves 5 and the sub-grooves 6. In addition, the land part row | line | column 4 currently formed symmetrically is formed in the tire circumferential direction with a phase shift.

  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 411 is 0.70 ≦ W / with respect to the maximum length L in the tire circumferential direction of the inland portion 411. 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 411 to the maximum length L in the tire circumferential direction of the inland portion 411 is set in a range of 70 [%] to 80 [%].

  When the ratio of the maximum width W in the tire width direction of the inland portion 411 to the maximum length L in the tire circumferential direction of the inland portion 411 is less than 70%, the inland portion 411 has a shape that 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. In addition, since the edge component and the groove component of the inland portion 411 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 it exceeds 80 [%], the inland portion 411 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 411 to the tire circumferential direction maximum length L of the inland portion 411 is set in a range of 70 [%] to 80 [%]. Is preferred.

  In the heavy duty pneumatic tire 1 according to the present embodiment, the maximum groove width Wd in the tire circumferential direction of the auxiliary groove 6 is 0.20 ≦ Wd with respect to the maximum tire circumferential length L of the inland portion 411. /L≦0.25 is set. That is, the ratio of the maximum groove width Wd in the tire circumferential direction of the sub-groove 6 to the maximum circumferential length L in the inland portion 411 is set in a range of 20 [%] to 25 [%].

  When the ratio of the maximum groove width Wd in the tire circumferential direction of the secondary groove 6 to the maximum tire circumferential length L in the inland region 411 is less than 20%, Sufficient shear resistance of a snow column formed in the groove 6 cannot be ensured, and the performance on snow is reduced. On the other hand, if it exceeds 25 [%], the edge component and the groove component of the inland portion 411 with respect to the tire circumferential direction within the contact surface to the road surface will decrease, leading to a decrease in performance on ice and on snow. For this reason, the ratio of the maximum groove width Wd in the tire circumferential direction of the auxiliary groove 6 to the maximum length L in the tire circumferential direction of the inland portion 411 is set in a range of 20 [%] to 25 [%]. It is preferable.

  In the present embodiment, performance tests on the performance on ice on the road surface, the performance on the snow surface on the snow, the steering stability performance on the dry road surface, and the uneven wear resistance performance were performed for a plurality of types of pneumatic tires with different conditions. (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 more preferable as the numerical value is larger. 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 more preferable as the numerical value is larger. 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 more preferable as the numerical value is larger. 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 more preferable as the numerical value is larger.

  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.

It is a top view which shows a part of tread part of the pneumatic tire for heavy loads concerning embodiment of this invention. It is a partially expanded view in FIG. It is a graph which shows the result of the performance test of the pneumatic tire concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heavy load pneumatic tire 2 Tread part 21 Tread surface 3 Circumferential main groove 4 Land part row 41 Narrow land part row 411 Middle land part 4111 Small land part 5 Narrow groove 6 Sub groove 7 Closed sipe 8 Crossing sipe α Angle of narrow groove C tire equator line W maximum width in the tire width direction in the inland area Wd maximum groove width in the secondary groove L maximum length in the tire circumferential direction in the inland area

Claims (5)

4 or more are provided at an angle of 5 degrees or less with respect to the tire circumferential direction, and a circumferential main groove that forms 5 or more land portion rows adjacent in the tire width direction;
In an aspect in which three or more land portion rows near the tire equator line are divided in the tire width direction to form narrow land portions, an angle of 8 degrees or less with respect to the tire circumferential direction is formed, and the circumferential main A narrow groove with a groove depth shallower than the groove;
A plurality of sub-grooves provided by connecting the circumferential main grooves and the narrow grooves adjacent to each other in a manner of forming a middle land portion obtained by dividing the narrow land portion row in the tire circumferential direction;
A heavy duty pneumatic tire comprising: a closed sipe provided with both ends closed on the tread of the inland portion.   The inland portion is divided in the tire circumferential direction to form two small land portions, and provided with a transverse sipe provided across the tire width direction, and the closed sipe is provided in each small land portion. The heavy-duty pneumatic tire according to claim 1.   The heavy-duty pneumatic tire according to claim 1 or 2, wherein the land portion rows adjacent in the tire width direction are line-symmetrically related to a symmetry axis extending in the tire circumferential direction.   The maximum width W in the tire width direction of the inland portion is set in a range of 0.70 ≦ 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 any one of claims 1 to 3.   The maximum groove width Wd in the tire circumferential direction of the sub-groove is set in a range of 0.20 ≦ Wd / L ≦ 0.25 with respect to the tire circumferential maximum length L of the inland portion. The heavy-duty pneumatic tire according to any one of claims 1 to 4.

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