JP2012081898A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of exhibiting excellent hydroplaning performance and braking performance while reducing rolling resistance.SOLUTION: The pneumatic tire has a main groove 1 extending along a tire circumferential direction CD and a lateral groove 2 that extends intersecting the main groove 1 at a tread surface. A main groove expanded width part 11 formed by expanding a groove width at a groove bottom side is formed at a main groove wall face facing the main groove 1. A lateral groove expanded width part 21 formed by expanding the groove width at the groove bottom side is formed at a lateral groove wall face facing the lateral groove 2. The main groove expanded width part 11 and the lateral groove expanded width part 21 intersect with each other through a corner expanded width part 31 with a circular arc shape in a plan view at the intersecting part 5 of the main groove 1 and the lateral groove 2.

Description

  The present invention relates to a pneumatic tire having a tread surface provided with a main groove extending along the tire circumferential direction and a lateral groove extending so as to intersect the main groove.

  In general, a tread surface of a pneumatic tire is provided with a main groove extending along the tire circumferential direction and a lateral groove extending so as to intersect the main groove, and land portions divided by these are provided as blocks and ribs. When running on a road surface where water has accumulated (hereinafter referred to as a wet road surface), the main grooves and lateral grooves function as drainage channels, discharging water intervening between the tread surface and the road surface, and suppressing the occurrence of hydroplaning. . As a method for improving hydroplaning performance (hereinafter, hydro performance), a method of increasing the groove volume by increasing the groove width of the main groove or the lateral groove is generally used.

  However, when the groove widths of the main groove and the lateral groove are increased, the ground contact area is reduced accordingly, so that the braking performance on the dry road surface tends to be lowered. In contrast, in the tire described in Patent Document 1 below, a chamfer is formed on the surface side edge portion of the groove wall surface facing the lateral groove, and a hollow portion formed by expanding the groove width on the groove bottom side on the groove wall surface is formed. By forming it, it is possible to improve the hydro performance while suppressing the reduction of the contact area. However, in the tire, although the groove volume of the lateral grooves is increased, there is still room for further improving drainage efficiency.

  On the other hand, in order to improve the braking performance on the dry road surface, it is effective to improve the non-uniformity of the contact pressure, but the tire described in the above document does not suggest a solution for that. Regarding the non-uniformity of the contact pressure, according to the knowledge of the present inventors, in the region along the edge of the land portion, that is, the region along the surface side edge of the groove wall surface in the main groove or the lateral groove, the contact pressure is It has been found that the contact pressure tends to increase, particularly in the corner portion of the land, and the contact pressure becomes relatively low in the inner region of the land.

  Moreover, in the tire described in the following Patent Document 2 according to the present application, a recess formed by expanding the groove width on the groove bottom side is formed on the groove wall surface. According to the study by the present inventors, when the tire is in contact with the ground, the strain concentrates on the groove bottom side portion of the land portion, and the strain tends to concentrate particularly on the corner portion of the land portion. Has been found to be effective in reducing Therefore, according to the tire, although the rolling resistance can be reduced, it does not deal with the distortion concentrated on the corner portion of the land portion. It was found that there was still room for improvement in performance and braking performance.

JP 2003-159910 A JP 2010-158929 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire capable of exhibiting excellent hydroplaning performance and braking performance while reducing rolling resistance.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire provided with a main groove extending along a tire circumferential direction and a lateral groove extending across the main groove on the tread surface, and faces the main groove. A main groove widening portion is formed on the main groove wall surface to increase the groove width on the groove bottom side, and a horizontal groove widening portion is formed on the horizontal groove wall surface facing the horizontal groove to expand the groove width on the groove bottom side, At the intersection of the main groove and the lateral groove, the main groove widened portion and the lateral groove widened portion intersect via a corner widened portion having an arc shape in plan view.

  According to this pneumatic tire, the main groove widening portion and the lateral groove widening portion are formed on the main groove wall surface facing the main groove and the horizontal groove wall surface facing the horizontal groove, respectively, by expanding the groove width on the groove bottom side. The strain concentrated on the bottom side of the land can be alleviated. Moreover, at the intersection of the main groove and the horizontal groove, the main groove widened portion and the horizontal groove widened portion intersect with each other via the arc-shaped corner widened portion, so that the amount of widening at the corner widened portion is the main groove widened portion or the horizontal groove widened portion. It is possible to effectively reduce the rolling resistance by effectively relieving the distortion that tends to be concentrated at the corners of the land.

  In addition, by forming the main groove widening portion on the main groove wall surface and forming the horizontal groove widening portion on the horizontal groove wall surface, the groove volume of the main groove and the horizontal groove is increased, and they intersect via the arc-shaped corner widening portion. Thus, while further increasing the groove volume, it is possible to promote the smooth flow of water from the main groove to the lateral groove, thereby improving the hydro performance. Nevertheless, it is possible to suppress the increase of the contact pressure in the area along the edge of the land part, and in particular, in the corner part of the land part, the increase of the contact pressure is effectively suppressed by the corner widening part. The braking performance on the dry road surface can be improved.

  In this invention, it is preferable that the curvature radius in the planar view of the said corner widening part exists in the range of 1-5 mm. By making this radius of curvature 1 mm or more, the corner widened portion is formed with a gentle curve, and it becomes easy to secure the amount of widening of the corner widened portion, which contributes to reducing rolling resistance and improving hydro performance and braking performance. sell. Further, by setting the radius of curvature to 5 mm or less, it is possible to prevent the corner widening portion from being excessively widened and to effectively improve the braking performance on the dry road surface.

  In the present invention, the depth from the surface side edge of the main groove wall surface to the main groove widened portion is 50% or more of the groove depth of the main groove, and from the surface side edge of the horizontal groove wall surface to the horizontal groove The depth to the widened portion is preferably 50% or more of the groove depth of the lateral groove. If the wet road surface is shallow and does not reach half of the groove depth, the hydroplaning phenomenon is less likely to occur. Therefore, according to the above configuration, the main groove widening section and the lateral groove widening section are more than necessary. Therefore, it is possible to effectively improve the braking performance on the dry road surface.

  In the present invention, a block divided by the main groove and the horizontal groove is provided, and the main groove widened portion and the horizontal groove are provided at each of the corner portions of the block located at the intersection of the main groove and the horizontal groove. It is preferable that the corner widened portion interposed between the widened portion and the widened portion is formed. According to such a configuration, it is possible to suppress an increase in the contact pressure in a region along the periphery of the block that is a land portion, and also in each corner portion of the block, the increase in the contact pressure can be suppressed by the corner widening portion. The braking performance on the dry road surface can be improved.

  In the present invention, the main groove wall surface in which the main groove widened portion is formed faces the shoulder main groove located on the outermost side in the tire width direction from the outer side in the tire width direction, and the horizontal groove in which the horizontal groove widened portion is formed. It is preferable that the wall face the shoulder lateral groove extending outward in the tire width direction from the shoulder main groove. In the shoulder land portion provided on the outer side in the tire width direction of the shoulder main groove, the tendency of the contact pressure to be non-uniform is particularly remarkable. Thus, the braking performance on the dry road surface can be effectively improved.

  In the present invention, it is preferable that the depth from the surface side edge portion of the lateral groove wall surface facing the shoulder lateral groove to the lateral groove widened portion decreases toward the outer side in the tire width direction. Thereby, since a lateral groove widening part becomes large toward a grounding end, drainage can be improved and hydro performance can be improved. In addition, when braking on a dry road surface, the contact pressure of the shoulder land portion, particularly the contact pressure on the contact end side, becomes high. The braking performance on the road surface can be improved more effectively.

The top view which shows an example of the tread surface of the pneumatic tire which concerns on this invention Side view of the block as seen from the tire circumferential direction Side view of the block as seen from the tire width direction Enlarged view of the main part of the block Side view showing block modification The figure which shows the shape of the main groove in the comparative example 1

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The tread surface Tr shown in FIG. 1 is provided with a plurality of (three in the present embodiment) main grooves 1 extending along the tire circumferential direction CD, and lateral grooves 2 extending so as to intersect the main grooves 1. ing. The tread surface Tr is provided with a plurality of blocks 4 divided by the main groove 1 and the lateral groove 2. The block 4 has a polygonal shape (rectangular shape in the present embodiment) in a plan view along the tire radial direction, and the groove bottom side portion has a rounded shape as indicated by a broken line. .

  The side view of the block 4 shown in FIGS. 2 and 3 corresponds to the A and B arrow views of FIG. 1, respectively. 2 to 4, the main groove wall surface 10 facing the main groove 1 is formed with a main groove widening portion 11 formed by increasing the groove width on the groove bottom side. The main groove widening portion 11 is formed by denting the groove bottom side of the main groove wall surface 10 into a groove shape, and extends in the extending direction of the main groove 1 by the widening amount indicated by X1. The widening amount X1 is a distance to the back end of the main groove widening portion 11 with reference to the virtual extension line L10 of the main groove wall surface 10, and is set to be substantially constant in this embodiment.

  As shown in an enlarged view in FIGS. 2 to 4, the lateral groove wall surface 20 facing the lateral groove 2 is formed with a lateral groove widening portion 21 formed by expanding the groove width on the groove bottom side. The lateral groove widening portion 21 is formed by recessing the groove bottom side of the lateral groove wall surface 20 into a groove shape, and extends in the extending direction of the lateral groove 2 by a widening amount indicated by X2. The widening amount X2 is a distance to the back end of the lateral groove widened portion 21 with reference to the virtual extension line L20 of the lateral groove wall surface 20, and is set to be substantially constant in this embodiment.

  A corner portion 4 a of the block 4 is located at an intersection 5 between the main groove 1 and the lateral groove 2. The block 4 has four corner portions 4a, and a corner widening portion 31 is formed in each of them. As shown in FIGS. 1 and 4, at the intersection 5, the main groove widened portion 11 and the lateral groove widened portion 21 intersect via a corner widened portion 31 that has an arc shape in plan view. As a result, a groove-shaped recess is formed around the block 4, and the groove bottom side portion (root portion) of the block 4 is made slightly thinner. The intersection 5 is not limited to a cross shape, and may be a T-shape.

  As described above, in the corner portion 4a, the corner widened portion 31 is formed by expanding the groove width on the groove bottom side by a larger amount than the main groove widened portion 11 and the lateral groove widened portion 21, and the main groove widened portion. 11 and the lateral groove widened portion 21 are connected smoothly. On the other hand, the surface shape of the corner portion 4a in plan view is angular, and the angle θ1 (see FIG. 1) is exemplified by 60 to 100 °. Thus, by making the surface of the corner portion 4a square, a ground contact area is effectively secured, which is beneficial for improving the braking performance.

  In this pneumatic tire, as described above, the groove width on the groove bottom side of both the main groove wall surface 10 and the lateral groove wall surface 20 is widened, so that the strain concentrated on the groove bottom side portion of the block 4 is well reduced. it can. Moreover, in the corner portion 4 a of the block 4, the corner widened portion 31 having an arc shape widens the groove width on the groove bottom side by a larger amount than the main groove widened portion 11 and the lateral groove widened portion 21. The distortion that tends to concentrate on the portion 4a can be effectively relieved, and the rolling resistance can be accurately reduced.

  The main groove widening portion 11 and the horizontal groove widening portion 21 not only increase the groove volume of the main groove 1 and the horizontal groove 2 but also increase the groove volume further by the arc-shaped corner widening portion 31 having a large amount of widening. Hydro performance can be improved by promoting smooth flow of water from the groove 1 to the lateral groove 2. Nevertheless, the increase in the contact pressure in the region along the edge of the block 4 can be suppressed, and particularly in the corner portion 4a, the increase in the contact pressure can be effectively suppressed by the corner widening portion 31. The braking performance on the dry road surface can be improved.

  1 to 4 show a state of a new article, and when wear progresses from here, the groove depths of the main groove 1 and the transverse groove 2 are reduced accordingly. Normally, as the groove depth decreases, the groove volume of the main groove 1 and the lateral groove 2 is greatly reduced. In this tire, the main groove widening portion 11 is formed on the main groove wall surface 10 to form the lateral groove. Since the lateral groove widened portion 21 is formed on the wall surface 20, it is easy to secure a groove volume even after wear, and excellent hydro performance can be exhibited in that respect.

  In the present embodiment, as shown in FIG. 2, since the connection portion between the back end of the main groove widening portion 11 and the groove bottom of the main groove 1 is formed with an arcuate surface, it concentrates on the groove bottom side portion of the block 4. It is possible to effectively relieve the tendency of distortion. The radius of curvature R1 of the arcuate surface is set to 2 to 5 mm, for example, and the lateral groove widened portion 21 can be similarly configured. In the main groove widening portion 11 and the lateral groove widening portion 2, since the radius of curvature of the arcuate surface can be set large, the rigidity at the groove bottom side portion of the block 4 can be improved and distortion can be reduced. In the corner widened portion 31, the radius of curvature of the arc-shaped surface can be made larger than that of the main groove widened portion 11, so that distortion that tends to concentrate on the corner portion 4 a can be effectively reduced. In addition, an inclined surface may be employed instead of the arcuate surface, or the back end of the main groove widening portion 11 may rise from the groove bottom at a substantially right angle.

  As described above, the corner widening portion 31 has a larger amount of widening than the main groove widening portion 11 and the lateral groove widening portion 21. Specifically, the widening amount X31 shown in FIG. 4 is larger than the widening amount X1, and the widening amount X32 is larger than the widening amount X2. The widening amount X31 is a distance from the imaginary extension line L10 of the main groove wall surface 10 to the back end of the corner widening portion 31 at the connection location with the lateral groove widening portion 21. The widening amount X32 is a distance from the imaginary extension line L20 of the lateral groove wall surface 20 to the back end of the corner widening portion 31 at the connection location with the main groove widening portion 11.

  The widening amounts X1 and X2 are preferably 0.5 mm or more, thereby reducing the distortion at the groove bottom side portion of the block 4, the effect of increasing the groove volume of the main groove 1 or the lateral groove 2, and the block It becomes easy to ensure the effect which suppresses the raise of the ground pressure in the area | region along 4 edges. Further, the widening amounts X1 and X2 are preferably 2 mm or less, whereby the rigidity of the block 4 can be easily maintained moderately, and adverse effects on braking performance and the like can be suppressed. The widening amount X1 is preferably larger than the widening amount X2 according to the required groove volume.

  The radius of curvature R3 in plan view of the corner widened portion 31 is preferably in the range of 1 to 5 mm. As a result, the corner widened portion 31 can be formed with a gentle curve, and the widening amounts X31 and X32 can be easily secured. As a result, the rolling resistance can be reduced, and the hydro performance and the braking performance can be improved. Moreover, it is possible to prevent the corner widening portion 31 from being excessively widened and to effectively improve the braking performance on the dry road surface. As the opening angle θ2 (see FIG. 1) of the corner widened portion 31, an angle θ1 ± 10 ° is exemplified, and an asymmetry may be given by making the angle different from the angle θ1.

  The depth D10 from the surface side edge portion 10a of the main groove wall surface 10 to the main groove widened portion 11 is 50% or more of the groove depth D1 of the main groove 1, and the horizontal groove width from the surface side edge portion 20a of the horizontal groove wall surface 20 is increased. The depth D20 to the portion 21 is preferably 50% or more of the groove depth D2 of the lateral groove 2. Thereby, the improvement effect with respect to the braking performance on a dry road surface can be made effective, without forming the main groove widening part 11 and the horizontal groove widening part 21 larger than necessary. From the viewpoint of securing the size of the main groove widening portion 11 and the lateral groove widening portion 21, it is preferable that the depth D10 is 50% or less of the groove depth D1, and the depth D20 is 40% or less of the groove depth D2.

  Since the groove depth D2 of the horizontal groove 2 can be set to be equal to or less than the groove depth D1 of the main groove 1, a configuration in which the horizontal groove 2 is shallower than the main groove 1 is also conceivable. Desirably, the depth D10 and the depth D20 are set equal to each other so that the main groove widened portion 11 and the lateral groove widened portion 21 communicate smoothly. Further, when the depth D10 and the depth D20 are different, it is preferable that the main groove widened portion 11 and the lateral groove widened portion 21 are smoothly communicated by gradually changing them in the vicinity of the corner portion 4a.

  In the present embodiment, a corner widening portion 31 interposed between the main groove widening portion 11 and the lateral groove widening portion 21 is formed in each corner portion 4 a of the block 4, and the widening portion is provided around the block 4. Extends in a loop. For this reason, an increase in the contact pressure in the region along the periphery of the block 4 can be suppressed, and further, in each corner portion 4a, an increase in the contact pressure can be suppressed by the corner widening portion 31. The braking performance on the dry road surface can be improved.

  In the shoulder block 4o (an example of a shoulder land portion) provided on the outer side in the tire width direction of the shoulder main groove 1o located on the outermost side in the tire width direction WD, the tendency that the contact pressure becomes non-uniform is particularly remarkable. In the present embodiment, the main groove wall surface 10 on which the main groove widened portion 11 is formed faces the shoulder main groove 1o from the outer side in the tire width direction, and the lateral groove wall surface 20 on which the horizontal groove widened portion 21 is formed extends from the shoulder main groove 1o. Since it faces the shoulder lateral groove 2o extending to the outer side in the tire width direction, the contact pressure can be made uniform and the braking performance on the dry road surface can be effectively improved.

  FIG. 5 is a side view of a block 4 (shoulder block 4o) according to a modification of the present invention as seen from the tire circumferential direction CD. In this example, the depth D20 from the surface side edge 20a of the lateral groove wall surface 20 facing the shoulder lateral groove 2o to the lateral groove widened portion 21 decreases toward the outer side in the tire width direction (right side in FIG. 5). As a result, the lateral groove widened portion 21 becomes larger toward the ground contact end E, so that drainage can be improved and hydro performance can be improved. In addition, when braking on a dry road surface, the ground pressure of the shoulder block 4o, particularly the ground pressure at the grounding end side, increases, so that a uniform effect of the ground pressure is accurately expressed, and braking performance on the dry road surface is improved. It can be improved effectively.

  In the present embodiment, an example in which the structure in which the widened portion as described above is formed is applied to all the land portions in the tread surface is shown, but in the present invention, a part of the land portion in the tread surface is applied. You may apply only to it. In the example of FIG. 5, a so-called square shoulder with a square shoulder edge is used, but a round shoulder with a rounded shoulder edge may be used instead.

  In the present invention, the tread pattern formed on the tread surface is not particularly limited, and for example, a rib may be included. In that case, the main groove widening portion as described above is formed on the main groove wall surface facing the main groove separating the ribs, and the horizontal groove widening portion as described above is formed on the horizontal groove wall surface facing the horizontal groove formed on the rib, A corner widening portion as described above may be formed between them. The main groove may be inclined with respect to the tire circumferential direction or may extend in a zigzag shape, and the lateral groove may be inclined with respect to the tire width direction or may be extended with bending.

  The pneumatic tire of the present invention is a mold used in vulcanization molding, with modifications to the extent that a protrusion corresponding to the above widened portion is provided on the protrusion for forming a main groove or a lateral groove on the tread surface. Can be manufactured in the same manner as the conventional tire manufacturing process. Of course, it is also possible to manufacture the pneumatic tire of the present invention by a different method.

  The pneumatic tire of the present invention can be configured in the same manner as a normal pneumatic tire except that the main groove widened portion, the lateral groove widened portion and the corner widened portion as described above are formed on the tread surface, and a conventionally known material, Any shape, structure, manufacturing method, etc. can be employed in the present invention.

  Hereinafter, the rolling resistance, hydro performance, and braking performance will be evaluated in order to specifically show the configuration and effects of the present invention. These performances are evaluated as described in (1) to (3) below, and the tire size used for the evaluation is 215 / 60R16.

(1) Rolling resistance Rolling resistance was measured with a drum running tester (drum diameter: 1.7 m), and the result of Comparative Example 1 was evaluated with an index of 100. The smaller the value, the smaller the rolling resistance and the better.

(2) Hydro performance The tire was rotated on a wet road surface having a water depth of 8 mm, the speed at which the hydroplaning phenomenon occurred was measured, and the result of Comparative Example 1 was evaluated with an index of 100. The larger the value, the higher the speed and the better the hydro performance.

(3) Braking performance A tire is mounted on an actual vehicle and travels on a dry road surface. A braking distance is measured when the traveling speed is reduced from 100 km / h to 0 km / h. The result was evaluated with an index of 100. The larger the value, the shorter the braking distance and the better the braking performance.

Comparative Example 1
In the tread surface shown in FIG. 1, the main groove widened portion, the lateral groove widened portion, and the corner widened portion are not formed as Comparative Example 1. FIG. 6 shows the shape of the main groove 1 ′ in Comparative Example 1. Even in a lateral groove (not shown), such a U-shape is formed, and the block 4 ′ is provided in a simple prism shape. The groove width W1 ′ of the main groove 1 ′ (the distance between the surface side edges of the main groove wall surface) is 7 mm, the groove depth D1 ′ is 8 mm, and the radius of curvature R1 ′ of the arcuate surface is 3.5 mm.

Comparative Example 2
Except that the corner widened portion is angular in plan view at the intersection of the main groove and the lateral groove, and the back ends of the main groove widened portion and the lateral groove widened portion intersect at right angles with Example 1 described later. The same configuration was designated as Comparative Example 2.

Example 1
In the tread surface shown in FIG. 1, all blocks were provided with the main groove widened portion, the lateral groove widened portion, and the corner widened portion shown in FIGS. The groove width of the main groove (the distance between the surface side edges of the wall surface of the main groove) is 6.5 mm, the groove depth D1 is 8 mm, the radius of curvature R3 of the corner widened portion is 2 mm, and the widening amounts X1 and X2 are 0.5 mm. The radius of curvature R1 of the arcuate surface is 4 mm, and the depth D20 / groove depth D2 is uniformly 60%.

Example 2
Example 2 was the same as Example 1 except that the depth D20 of the shoulder block was decreased toward the outer side in the tire width direction. Depth D20 / groove depth D2 was 50% on the outer side in the tire width direction (grounding end side) and 70% on the inner side in the tire width direction. The evaluation results are shown in Table 1.

  From Table 1, it can be seen that Examples 1 and 2 are superior to Comparative Examples 1 and 2 in any of rolling resistance, hydro performance, and braking performance. Moreover, in Example 2, the hydro performance and the braking performance are further improved by devising the shape of the lateral groove widened portion in the shoulder block.

1 main groove 1o shoulder main groove 2 horizontal groove 2o shoulder horizontal groove 4 block (an example of land)
4a Corner portion 5 Intersection 10 Main groove wall surface 10a Surface side edge portion 11 Main groove widened portion 20 Horizontal groove wall surface 20a Surface side edge portion 21 Horizontal groove widened portion 31 Corner widened portion

Claims (6)

In a pneumatic tire provided with a main groove extending along the tire circumferential direction and a lateral groove extending across the main groove on the tread surface,
The main groove wall surface facing the main groove is formed with a main groove widening portion that widens the groove width on the groove bottom side, and the lateral groove widening surface is formed by expanding the groove width on the groove bottom side on the horizontal groove wall surface facing the horizontal groove. The air is characterized in that the main groove widened portion and the horizontal groove widened portion intersect with each other through a corner widened portion having an arc shape in plan view at an intersection of the main groove and the horizontal groove. Enter tire.   The pneumatic tire according to claim 1, wherein a radius of curvature of the corner widened portion in a plan view is in a range of 1 to 5 mm.   The depth from the surface side edge of the main groove wall surface to the main groove widened portion is 50% or more of the groove depth of the main groove, and from the surface side edge of the horizontal groove wall surface to the horizontal groove widened portion. The pneumatic tire according to claim 1 or 2, wherein the depth is 50% or more of the groove depth of the lateral groove.   A block divided by the main groove and the horizontal groove is provided, and each of the corner portions of the block located at the intersection of the main groove and the horizontal groove includes the main groove widened portion and the horizontal groove widened portion. The pneumatic tire according to claim 1, wherein the corner widened portion interposed therebetween is formed.   The main groove wall surface on which the main groove widened portion is formed faces the shoulder main groove located on the outermost side in the tire width direction from the tire width direction outer side, and the horizontal groove wall surface on which the horizontal groove widened portion is formed is The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire faces a shoulder lateral groove extending outward from the shoulder main groove in the tire width direction.   The pneumatic tire according to claim 5, wherein a depth from a surface side edge portion of the lateral groove wall surface facing the shoulder lateral groove to the lateral groove widened portion decreases toward the outer side in the tire width direction.

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