JP2013129409A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wear performance while ensuring performances on snow and ice.SOLUTION: A pneumatic tire includes in a tread 16: a rib row 12 segmented by circumferential grooves 18 extending in a tire circumferential direction and formed in a staggered pattern in the tire circumferential direction; and a sipe 14 in the rib row 12. The sipe has: a deep bottom 24 which extends in a tire width direction and in which the deepest portion continues; and shallow bottoms which are formed shallowly more than the deep bottom in the both sides in the tire width direction of the deep bottom and are open respectively to the circumferential grooves 18 interposing the rib row 12; wherein the widths An, Bn of the shallow bottoms in the tire width direction are set to be larger in a mount part 12P, which is convex, and set to be smaller in a valley part 12C, which is concave, in the tire width direction in the edges 12L, 12R at both sides of the rib row 12 in the tire width direction.

Description

  The present invention relates to a pneumatic tire.

  In the tread rib row, sipes opened in circumferential grooves sandwiching the rib row are respectively formed, and at both ends in the tire width direction of the sipe, bottom raised portions shallower than the central portion of the sipe are provided. A pneumatic tire is disclosed (see Patent Document 1).

JP 2001-163015 A

  The width and depth of the bottom raised portion in the conventional sipe described above are set in consideration of the performance on snow and ice, the running performance on the dry road, and the wear performance. Among these, in order to improve the performance of snow and ice, it is effective to improve the opening of the sipe and the edge effect, so the width of the bottom raised portion is set small and the depth is set large. In order to improve the running performance on the dry road surface, it is effective to improve the block rigidity, so that the width of the bottom raised portion is set large and the depth is set small.

  However, when the rib rows are formed in a zigzag manner, the maximum point of the circumferential rigidity of the rib rows in the tire width direction changes periodically in the tire width direction. Further, when a tire circumferential force is applied to the edge of the zigzag rib row, a force is generated in a direction perpendicular to the edge direction, and a shear force having an angle with respect to the tire width direction is generated at the end of the sipe. When sipe is provided in the zigzag rib row, it is necessary to consider the influence of the amplitude at which the maximum point of the tire circumferential rigidity changes and the shear force generated at the end of the sipe.

  In view of the above facts, the present invention aims to improve wear performance while ensuring on-ice performance.

  In the invention of claim 1, the tread is partitioned by a circumferential groove extending in the tire circumferential direction, the rib row is formed in a zigzag shape in the tire circumferential direction, and the rib row extends in the tire width direction, and the deepest portion continues. A tire having a deep bottom portion and a shallow bottom portion that is formed shallower than the deep bottom portion on both sides in the tire width direction of the deep bottom portion and opens to the circumferential grooves sandwiching the rib rows, respectively, and the tire width of the shallow bottom portion A sipe that is set so that a width in the direction is large at a peak portion that is convex in the tire width direction and is smaller than the peak portion in a concave valley portion among the edges on both sides in the tire width direction of the rib row. ,have.

  In the pneumatic tire according to claim 1, a sipe having a deep bottom portion and shallow bottom portions on both sides in the tire width direction is formed in a zigzag rib row, and the width of the shallow bottom portion in the tire width direction is a rib. Among the edges on both sides of the row, it is set so that it is larger at the peak that is convex in the tire width direction and smaller than the peak at the valley that is concave, so even if the rib row is zigzag The amplitude at which the maximum point of the tire circumferential rigidity of the rib row changes is suppressed. Accordingly, when a force in the tire circumferential direction is applied to the rib row, a shear force having an angle with respect to the tire width direction is hardly generated at the end portion of the sipe, and the occurrence of uneven wear is suppressed. At the same time, the generation of the edge effect is ensured by the edge length of the sipe in the rib row and the ease of opening, so the performance on snow and ice is also secured. Thus, according to the pneumatic tire of claim 1, the wear performance can be improved while ensuring the performance on snow and ice.

  According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, with respect to a center line extending in the tire circumferential direction through the tire width direction center of the rib row, the tire circumferential direction maximum stiffness point of the rib row is defined. The amplitude at a position in the tire circumferential direction whose center periodically changes with zigzag of the rib row is an, and the absolute value of the width difference in the tire width direction of the shallow bottom portion on both sides at the position is 2bn. Then, 1 / 2an <bn <2an.

  Here, the reason why the lower limit is set to 1/2 an is that if it is less than this, it is difficult to suppress the generation of shearing force at the end of the sipe. Moreover, the upper limit was set to 2an because if it exceeds this, the width of the shallow bottom portion in the tire width direction may become too small.

  In the pneumatic tire according to claim 2, since the difference in the width in the tire width direction of the shallow bottom portions on both sides of the sipe is appropriately set, the occurrence of uneven wear can be further suppressed.

  According to a third aspect of the present invention, the tread is partitioned by a circumferential groove extending in the tire circumferential direction, the rib row is formed in a zigzag shape in the tire circumferential direction, the rib row extends in the tire width direction, and the deepest portion continues. A tire having a deep bottom portion and a shallow bottom portion that is formed shallower than the deep bottom portion on both sides in the tire width direction of the deep bottom portion and opens to the circumferential grooves sandwiching the rib rows, respectively, and the tire width of the shallow bottom portion The width of the direction is larger than the boundary between the crest and the trough at the crest and the trough that are convex in the tire width direction among the edges on both sides of the rib row in the tire width direction. And a sipe set to.

  In the pneumatic tire according to claim 3, a sipe having a deep bottom portion and shallow bottom portions on both sides in the tire width direction is formed in a zigzag rib row, and the width of the shallow bottom portion in the tire width direction is a rib. Among the edges on both sides of the row, it is set so that it is large at the peak and valley and is minimal at the boundary between the peak and valley, so the total width of the sipe is reduced due to the small width of the rib row. Even in such a case, it is possible to secure a larger width in the tire width direction at the shallow bottom portions on both sides, thereby suppressing the occurrence of uneven wear.

  According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, when the zigzag period of the rib row is T, the edges on both sides of the rib row in the tire width direction are provided. Has a phase difference of 1 / 4T to 3 / 4T in the tire circumferential direction.

  Here, the lower limit of the phase difference is set to 1 / 4T and the upper limit is set to 3 / 4T. When the phase difference is small, the difference in shearing force generated near the shallow bottoms on both sides of the sipe needs to be improved. It is because it is not the level to do.

  In the pneumatic tire according to the fourth aspect, even when the phase difference between the edges on both sides of the rib row is relatively large, the occurrence of uneven wear can be suppressed.

  Here, the reason why the lower limit is set to 0.3 is that if it is less than this, the width of the deep bottom portion becomes too small when the total width of the sipe is large. Further, the upper limit is set to 0.8 because, if the upper limit is exceeded, the width in the tire width direction of the shallow bottom portion on both sides of the sipe becomes too small when the entire width of the sipe is small.

  The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein a ratio of the width of the deep bottom portion to the entire width of the sipe is 0.3 to 0.8. .

  In the pneumatic tire according to claim 5, since the ratio of the width of the deep bottom portion to the entire width of the sipe is appropriately set, performance on snow and ice is ensured by the deep bottom portion, and block rigidity is secured at the shallow bottom portion. be able to.

  As described above, according to the pneumatic tire of the first aspect of the present invention, an excellent effect that the wear performance can be improved while ensuring the performance on snow and ice is obtained.

  According to the pneumatic tire of the second aspect, it is possible to obtain an excellent effect that the occurrence of uneven wear can be further suppressed.

  According to the pneumatic tire of the third aspect, even when the entire width of the sipe is reduced because the width of the rib row is small, the width in the tire width direction of the shallow bottom portions on both sides is ensured to be larger. The excellent effect that generation | occurrence | production of abrasion can be suppressed is acquired.

  According to the pneumatic tire of the fourth aspect, it is possible to obtain an excellent effect that the occurrence of uneven wear can be suppressed even when the phase difference between the edges on both sides of the rib row is relatively large.

  According to the pneumatic tire of the fifth aspect, it is possible to obtain an excellent effect that the performance on snow and ice can be secured by the deep bottom portion and the block rigidity can be secured by the shallow bottom portion.

It is an expansion development view showing an example of a tread rib in a pneumatic tire. It is a 2-2 arrow expanded sectional view in Drawing 1 showing a sipe. FIG. 3 is an enlarged sectional view taken along arrow 3-3 in FIG. FIG. 5 is an enlarged development view showing a modification of tread ribs in a pneumatic tire.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In FIG. 1, a pneumatic tire 10 according to this embodiment includes a rib row 12 and a sipe 14.

  The rib row 12 is defined in the tread 16 by a circumferential groove 18 extending in the tire circumferential direction, and is formed in a zigzag shape in the tire circumferential direction. In the illustrated example, the circumferential groove 18 is also formed in a zigzag shape in the tire circumferential direction, and the edge of the land portion row 20 (block row or rib row) adjacent in the tire width direction across the circumferential groove 18. 22 also has a zigzag shape. In addition, about the edge 22 of this land part row | line | column 20, it is not restricted to zigzag shape, For example, it may be linear form in a tire peripheral direction.

  Assuming that the zigzag period of the rib row 12 is T, the edges 12L and 12R on both sides in the tire width direction of the rib row 12 have a phase difference D of 1 / 4T to 3 / 4T in the tire circumferential direction. Due to the presence of the phase difference D, the width of the rib row 12 periodically changes in the tire circumferential direction. The phase difference D is a design that is necessary for ensuring the snow-ice handling stability performance and the tire noise performance.

  Here, the lower limit of the phase difference D is set to 1 / 4T, and the upper limit is set to 3 / 4T. When the phase difference D is small, the shear force generated in the vicinity of the shallow bottom portions 26 on both sides of the sipe 14 to be described later. This is because the difference is not at a level that requires improvement. Note that the period T is not limited to a fixed one, and a plurality of kinds of periods T may be appropriately combined to give pitch variations to the zigzag shape to reduce noise.

  2 and 3, the sipe 14 extends in the tire width direction in the rib row 12, and has a deep bottom portion 24 where the deepest portion continues and shallower than the deep bottom portion 24 on both sides of the deep bottom portion 24 in the tire width direction. In addition, it has a shallow bottom portion 26 respectively opened in the circumferential groove 18 sandwiching the rib row 12. As shown in FIG. 1, the total width Wn (FIGS. 2 and 3) of the sipe 14 is also periodically changed as the width of the rib row 12 is periodically changed. This full width (Wn) can also be referred to as the “full length”. The deep bottom portion 24 is formed shallower than the circumferential groove 18.

  In each sipe 14, the widths An and Bn of the shallow bottom portions 26 on both sides in the tire width direction are large at the peaks 12P protruding in the tire width direction among the edges 12L and 12R on both sides of the rib row 12 in the tire width direction. The trough 12C is set to be smaller than the peak 12P. The width (An, Bn) of the shallow bottom portion 26 in the tire width direction can also be referred to as “length”.

  As shown by the thin line L in FIG. 1, the center of the tire circumferential direction maximum stiffness point of the rib row 12 is based on the center line CL passing through the center of the rib row 12 in the tire width direction and extending in the tire circumferential direction. It changes periodically with 12 zigzags. Due to this periodic change, the thin line L becomes a sine wave. Note that the shear force generated in the rib row 12 during acceleration and deceleration, and the maximum point of opening and falling of the sipe 14 at that time are also sine waves having the same cycle.

  Taking the center line CL as a reference, the amplitude of the thin line L at a certain position in the tire circumferential direction is an. This amplitude an can be obtained by analysis, for example. In FIG. 1, since it is assumed that the width of the shallow bottom portions 26 on both sides in each sipe 14 is equal, that is, An = Bn, the shape of the thin line L is the maximum of the amplitude an of the thin line L in each period T. The value is symmetric with respect to the center line CL. In the case of An ≠ Bn, the rigidity at both ends of the sipe 14 is not uniform, and therefore the maximum value of the amplitude an of the thin line L in each period T is asymmetric with respect to the center line CL.

  If the amplitude an of the thin line L at a certain position in the tire circumferential direction is used, and the absolute value of the difference between the widths An and Bn in the tire width direction of the shallow bottom portions 26 on both sides at this position is 2bn, 1 / 2an <bn <2an It is. This bn is called an adjustment width. Here, the reason why the lower limit is set to ½ an is that if it is less than this, it becomes difficult to suppress the generation of the shearing force at the end of the sipe 14. The reason why the upper limit is set to 2an is that when the upper limit is exceeded, the widths An and Bn of the shallow bottom portion 26 may become too small. At the position where the thin line L intersects the center line CL, An = Bn.

  The method for obtaining the widths An and Bn of the shallow bottom portion 26 will be described. First, regarding the width of the shallow bottom portion 26, provisional widths A0 and B0 having an appropriate ratio with respect to the total width Wn of the sipe 14 are set. As an example, a ratio in which A0 / Wn and B0 / W0 are 0.2 to 0.7, respectively, is appropriate. The widths A0 and B0 are, for example, constant at each position in the tire circumferential direction. A0 = B0 may be set.

  In FIG. 1, a line connecting the position of the width A0 in order from the left end (edge 12L side) of the sipe 14 in the tire circumferential direction is a two-dot chain line L1, and the right end (edge 12R) side end of the sipe 14 A line connecting the positions of the width B0 to the tire circumferential direction in turn is a two-dot chain line L2.

  The provisional widths A0 and B0 plus the adjustment width bn described above become the widths An and Bn of the shallow bottom portion 26. The adjustment width bn is added at the peak portion 12P where the amplitude an of the thin line L exists, and the adjustment width bn is drawn at the valley portion 12C on the opposite side. Therefore, at the position of the section line 2-2 in FIG. 1, since the left side is the valley 12C and the right side is the peak 12P, An = A0−bn for the left width An, and Bn for the right width Bn. = B0 + bn. However, if A0 ≦ bn, the width An of the shallow bottom portion 26 cannot be secured, so the temporary width A0 is set to satisfy the relationship of A0> bn. Desirably, A0−bn ≧ 1.5 mm is set.

  In the region where the left side is the peak 12P and the right side is the valley 12C, An = A0 + bn and Bn = B0-bn. However, if B0 ≦ bn, the width Bn of the shallow bottom portion 26 cannot be secured, so the provisional width B0 is set to satisfy the relationship B0> bn. Preferably, B0−bn ≧ 1.5 mm is set.

  At the position of the 3-3 cross section line that is the boundary portion 12B between the mountain portion 12P and the valley portion 12C, the thin line L intersects the center line CL and an = 0, so An = A0 and Bn = B0. .

  In FIG. 1, a position corresponding to the width An from the end portion on the left side (edge 12L side) of the sipe 14 is obtained including a tire circumferential position where the sipe 14 is not provided, and a line connected in order in the tire circumferential direction. It is a thin line A. Further, the position of the width Bn from the end on the right side (edge 12R) side of the sipe 14 is obtained including the tire circumferential direction position where the sipe 14 is not provided, and the line connected in order in the tire circumferential direction is the thin line B. In other words, the position where the thin lines A and B intersect with the sipe 14 is the boundary between the shallow bottom portion 26 and the deep bottom portion 24 in the sipe 14.

  Note that the two-dot chain lines L1 and L2 and the thin lines A, B, and L in the drawings are imaginary lines described for explaining the present embodiment, and none of them appear as shapes in the rib row 12. However, the two-dot chain lines L1 and L2 can be obtained by appropriately setting the provisional widths A0 and B0. For the thin line L, when the widths An and Bn of the shallow bottom portions 26 on both sides in each sipe 14 are equal (An = Bn), the sipe 14 is not provided at the midpoint of the rib row 12 in the tire width direction. It can be obtained by obtaining the tire circumferential direction position and connecting them in the tire circumferential direction in order.

  It is desirable that the ratio of the width of the deep bottom portion 24 to the total width Wn of the sipe 14 is 0.3 to 0.8. That is, [Wn− (An + Bn)] / Wn = 0.3 to 0.8. Here, the reason why the lower limit is set to 0.3 is that if the total width Wn of the sipe 14 is large, the width of the deep bottom portion 24 becomes too small. The reason why the upper limit is set to 0.8 is that when the upper limit is exceeded, the width of the shallow bottom portions 26 on both sides of the sipe 14 becomes too small when the total width Wn of the sipe 14 is small.

  2 and 3, the depth D1 of the shallow bottom portion 26 and the depth D2 of the deep bottom portion 24 are appropriately set in consideration of the performance on snow and ice, the running performance on the dry road surface, and the wear performance.

(Modification)
As shown in FIG. 4, with respect to the width An and Bn in the tire width direction of the shallow bottom portion 26 of the sipe 14, of the edges 12 </ b> L and 12 </ b> R on both sides of the rib row 12 in the tire width direction, You may set so that it may become larger than the boundary part 12B of this mountain part 12P and this trough part 12C in a tire peripheral direction by 12P and trough part 12C used as a concave. Even if the total width Wn (see FIGS. 2 and 3) of the sipe 14 is reduced due to the small width of the rib row 12 depending on the tire size or the like, the widths An and Bn of the shallow bottom portions 26 on both sides are secured more. This is because the occurrence of uneven wear can be suppressed. Here, the sizes of the widths An and Bn are compared between the sipes 14 formed in the tire circumferential direction.

(Function)
This embodiment is configured as described above, and the operation thereof will be described below. In FIG. 1, in the pneumatic tire 10 according to the present embodiment, a sipe 14 having a deep bottom portion 24 and shallow bottom portions 26 on both sides in the tire width direction is formed in a zigzag rib row 12. Since the widths An and Bn of the ribs 12 are set so as to be large at the peak portion 12P protruding in the tire width direction and to be small at the concave valley portion 12C among the edges 12L and 12R on both sides of the rib row 12. Even if the rib row 12 has a zigzag shape, the amplitude at which the maximum point of the rigidity in the tire circumferential direction of the rib row 12 changes is suppressed. That is, the amplitude an of the thin line L is suppressed more than that shown in the figure. In addition, the thin line L shown in the figure is when the widths An and Bn of the shallow bottom portions 26 on both sides of each sipe 14 are equal, as described above.

  Accordingly, when a force in the tire circumferential direction is applied to the rib row 12, a shearing force having an angle with respect to the tire width direction is hardly generated at the end of the sipe 14, and occurrence of uneven wear is suppressed. At the same time, the generation of the edge effect is ensured by the edge length of the sipe 14 in the rib row 12 and the ease of opening, so the performance on snow and ice is also secured. Thus, according to the pneumatic tire 10, the wear performance can be improved while ensuring the performance on snow and ice.

  Further, by appropriately setting the difference between the widths An and Bn of the shallow bottom portions 26 on both sides of the sipe 14, it is possible to further suppress the occurrence of uneven wear. When designing the tread 16, the thin lines A and B (FIG. 1) corresponding to the shape of the rib row 12 are obtained, and the intersection of each sipe 14 and the thin lines A and B in the tire circumferential direction is obtained. The widths An and Bn of the shallow bottom portion 26 in each sipe 14 can be easily obtained.

  Furthermore, by appropriately setting the range of the phase difference D between the edges 12L and 12R on both sides of the rib row 12, even when the phase difference D is relatively large, occurrence of uneven wear can be suppressed.

  In addition, by appropriately setting the ratio of the width of the deep bottom portion 24 to the total width Wn of the sipe 14, the deep bottom portion 24 can ensure the performance on snow and ice, and the shallow bottom portion 26 can ensure the block rigidity.

(Other embodiments)
In the above embodiment, the adjustment width bn is ½an <bn <2an, but the range of the adjustment width bn is not limited to this. The phase difference D for the edges 12L and 12R on both sides in the tire width direction of the rib row 12 is in the range of 1 / 4T to 3 / 4T with respect to the zigzag period T. Not limited to. Furthermore, although the ratio of the width of the deep bottom portion 24 to the total width Wn of the sipe 14 is 0.3 to 0.8, the ratio of the width is not limited to this.

(Test example)
About the tire which concerns on a comparative example and an Example, evaluation with a real vehicle was performed about the acceleration performance on snow and ice, the deceleration performance on snow and ice, and the wear performance. The tire size is 195 / 65R15.

  In the tire according to the comparative example, the width of the shallow bottom portion 26 of each sipe 14 in the tire circumferential direction is set to An = A0, Bn = B0, and An = Bn. In other words, in the tire according to the comparative example, the width of the shallow bottom portion 26 is constant as indicated by the two-dot chain lines L1 and L2 in FIG. On the other hand, in the tire according to the example, the width of the shallow bottom portion 26 is changed as shown by the thin lines A and B in FIG.

  The results are as shown in Table 1. In Table 1, the acceleration performance on snow and ice and the deceleration performance on snow and ice are shown as indexes with a comparative example as 100. From this result, heel & toe wear (uneven wear) occurred in the rib row in the comparative example, while in the example, the same performance as the comparative example was ensured for the acceleration performance on snow and ice and the deceleration performance on snow and ice. It can be seen that the occurrence of heel & toe wear (uneven wear) in the rib row can be suppressed.

10 Pneumatic tire 12 Rib row 12C Valley 12L Edge 12P Mountain 12R Edge 14 Sipe 16 Tread 18 Circumferential groove 24 Deep bottom 26 Shallow bottom an Amplitude An width bn Adjustment width Bn width D Phase difference T Period Wn Full width

Claims (5)

Ribs arranged on the tread by circumferential grooves extending in the tire circumferential direction and formed in a zigzag shape in the tire circumferential direction;
A deep bottom portion extending in the tire width direction in the rib row and continuing the deepest portion, and formed shallower than the deep bottom portion on both sides of the deep bottom portion in the tire width direction, and opened in the circumferential groove sandwiching the rib row, respectively. The width of the shallow bottom portion in the tire width direction is large at the peak portion protruding in the tire width direction among the edges on both sides of the rib row in the tire width direction, and at the trough portion that is concave. A sipe set to be smaller than the peak,
Pneumatic tire having   The tire circumferential direction in which the center of the tire circumferential stiffness maximum point of the rib row periodically changes with the zigzag of the rib row with reference to a center line extending in the tire circumferential direction through the tire width direction center of the rib row The air according to claim 1, wherein an amplitude at a certain position is an, and an absolute value of a difference in width in the tire width direction of the shallow bottom portion on both sides at the position is 2 bn. Enter tire. Ribs arranged on the tread by circumferential grooves extending in the tire circumferential direction and formed in a zigzag shape in the tire circumferential direction;
A deep bottom portion extending in the tire width direction in the rib row and continuing the deepest portion, and formed shallower than the deep bottom portion on both sides of the deep bottom portion in the tire width direction, and opened in the circumferential groove sandwiching the rib row, respectively. The width of the shallow bottom portion in the tire width direction is a peak portion that is convex in the tire width direction and a trough portion that is concave in the tire width direction on both edges of the rib row. A sipe set to be larger than the boundary between the mountain and the valley,
Pneumatic tire having If the zigzag period of the rib row is T,
The pneumatic tire according to any one of claims 1 to 3, wherein the edges on both sides of the rib row in the tire width direction have a phase difference of 1 / 4T to 3 / 4T in the tire circumferential direction.   The pneumatic tire according to any one of claims 1 to 4, wherein a ratio of a width of the deep bottom portion to a total width of the sipe is 0.3 to 0.8.

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