JP2013100063A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the uneven wear resistance of a shoulder area of a tread while securing wet performance.SOLUTION: In the tread 2 of a pneumatic tire 1, shoulder blocks 17, 18 are sectioned and formed by peripheral direction grooves 3 to 6 and a plurality of lateral grooves 14, 15 extending from the peripheral direction grooves 3 to 6 to the outside in the tire width direction. Protruded portions 30, 31 for connecting the shoulder blocks 17, 18 adjacent to each other in the tire peripheral direction are protruded from groove bottoms of the lateral grooves 14, 15. Each of the protruded portions 30, 31 has three top surfaces 33a, 33b and 33c which have tire radial direction distances from tread surfaces 17a, 18a of the adjacent shoulder blocks 17, 18 which are different from each other. The three top surfaces 33a, 33b and 33c are disposed so that the further the top surfaces are located at the outside in the tire width direction, the shorter the tire radial direction distance from the tread surfaces 17a, 18a becomes.

Description

  The present invention relates to a pneumatic tire including a plurality of land portions (shoulder blocks) arranged along a tire circumferential direction in a shoulder region of a tread portion, and by connecting the shoulder blocks adjacent to each other in the tire circumferential direction. It is intended to suppress uneven wear by increasing the rigidity of the block.

  Pneumatic tires, especially pneumatic tires with high loads, suffer from uneven wear (heel and toe wear) due to insufficient rigidity of the shoulder block located in the shoulder area of the tread. There is. Various proposals have been made for such problems, and one of them is a shoulder adjacent to the tire circumferential direction by providing a raised portion (also referred to as a tie bar) at the bottom of the lug groove defining the shoulder block. A technique is known in which the blocks are connected to each other, thereby increasing the rigidity of the shoulder blocks, that is, suppressing the shear deformation of the shoulder blocks to suppress the uneven wear (see Patent Document 1).

JP 2000-225813 A

  However, according to the conventional technology described above, the shoulder block can increase the rigidity of the shoulder block and suppress uneven wear, but the cross-sectional shape of the raised portion is a simple rectangle and the height of the top surface (in other words, If the shoulder block wears as the tire is used, the top surface of the raised portion and the shoulder block's tread come together at a certain point in time. In other words, the edge of the shoulder block (the edge extending in the tire width direction, hereinafter also referred to as the “width direction edge”) is reduced, and the wet performance rapidly deteriorates at the above time point. There is.

  Therefore, the present invention suppresses a sudden decrease in wet performance in the process of wearing the shoulder block while partially connecting the shoulder blocks adjacent to each other in the tire circumferential direction to suppress uneven wear in the shoulder block. It is an object of the present invention to provide a pneumatic tire that can exhibit stable wet performance over a long period of time.

  The present invention has been made to solve the above problems, and a pneumatic tire according to the present invention includes a tread portion, a circumferential groove extending in the tire circumferential direction, and an outer side in the tire width direction extending from the circumferential groove. A plurality of lateral grooves that are partitioned by a plurality of lateral grooves and terminate at the position of the tread end in the tire width direction, or include a plurality of shoulder blocks extending outward in the tire width direction beyond the tread end, and adjacent to each other in the tire circumferential direction. In the pneumatic tire formed by connecting shoulder blocks by a raised portion raised from the groove bottom of the lateral groove, each of the raised portions has three top surfaces whose distances in the tire radial direction from the treads of adjacent shoulder blocks are different from each other. The three top surfaces are arranged so that the distance from the tread surface to the tire radial direction decreases as the top surface is located on the outer side in the tire width direction. And it is characterized in that it is. The “tread end” here means that the pneumatic tire is mounted on a standard rim specified in JATMA YEAR BOOK (Japan Automobile Tire Association Standard) and the maximum load in the size and ply rating applicable to JATMA YEAR BOOK. Fills 100% of the air pressure (maximum air pressure) corresponding to the capacity (internal pressure-load capacity correspondence table) as the internal pressure, and indicates the outermost ground contact portion in the tire width direction with the maximum load capacity loaded. In addition, when a TRA standard and an ETRTO standard are applied in the use place or manufacturing place of a tire, it follows each standard. In addition, the distance from the tread of the shoulder block to the top surface of the raised portion is determined by the no-load state in which the tire is mounted on the standard rim, the maximum air pressure is filled, and the tire is not grounded (hereinafter referred to as “internal pressure filling / no-load state”). ")"). The tread of the shoulder block may be flat, uneven, or curved.If it is not flat, the shoulder block tread in the tire radial direction is the most An intermediate position between the inner position and the outermost position is used as a reference when measuring the distance from the tread of the shoulder block. In addition, when the unevenness on the tread of the shoulder block is caused by a manufacturing error, the difference between the innermost position in the tire radial direction and the outermost position on the tread of the shoulder block is about 2 mm at the maximum. It is.

  In such a pneumatic tire, the shoulder blocks adjacent to each other in the tire circumferential direction are connected by the raised portions, whereby the rigidity of the shoulder blocks can be increased and the uneven wear resistance can be improved. At this time, the raised portion has three top surfaces whose distances in the tire radial direction from the tread surface of the adjacent shoulder block are different from each other. Edge component that extends in the width direction (width direction edge component) that functions when starting and stopping on running on wet road surfaces (including wet road surfaces and icy and snowy road surfaces) by exposing the top surface stepwise on the shoulder block tread. Can be secured over a long period of time. In particular, since the three top surfaces are arranged such that the distance from the tread surface to the tire radial direction becomes smaller as the top surface located on the outer side in the tire width direction, the bulging portion is the tire as the wear of the shoulder block progresses. It is exposed from the top surface on the outer side in the width direction, and the inner top surface is gradually exposed. As a result, the edge component in the width direction is left in the region in the tire width direction inside of the shoulder block where the contact pressure is relatively large, and the wet performance can be ensured. On the other hand, among the three vertices of the raised portion, the top surface on the outermost radial direction is arranged on the outer side in the width direction, so that the rigidity in the vicinity of the ground contact end where uneven wear is more likely to occur is increased. The effect of suppressing wear can be enhanced.

  In the pneumatic tire of the present invention, of the three top surfaces of the raised portion, the innermost top surface in the tire width direction has a distance in the tire radial direction from the tread surface adjacent to the raised portion. The other two top surfaces have a distance in the tire radial direction from the tread surface smaller than the half length. According to this, sufficient rigidity is ensured on the shoulder side of the shoulder block, and the widthwise edge component due to the lateral groove is maintained until the end of wear of the shoulder block to obtain a desired wet performance. Can do. The “groove depth of the circumferential groove” referred to herein refers to the length in the tire radial direction between the groove bottom of the circumferential groove and the shoulder surface of the adjacent shoulder block in the internal pressure filling / no-load state.

  Moreover, in the pneumatic tire of the present invention, the length in the tire width direction of the top surface on the outermost side in the tire width direction among the three top surfaces of the raised portions is the shoulder block adjacent to the raised portions, It is preferable that the width is not more than half of the length in the width direction of the edge adjacent to the lateral groove. According to this, a desired groove and a width direction edge component can be secured in the process of wear.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the pneumatic tire which prevented the sudden fall of wet performance, improving the uneven wear-proof performance of a shoulder block.

(A) is an expanded view which shows a part of tread part as an example of the pneumatic tire according to this invention, (b) is sectional drawing along the AA shown to (a). (A) is sectional drawing in the cross section similar to FIG.1 (b) which shows the cross-sectional shape of the protruding part to which abrasion advanced as an example of the general pneumatic tire in a prior art, (b), It is sectional drawing in the cross section similar to FIG.1 (b) which shows the cross section of the protruding part to which abrasion advanced as an example of the pneumatic tire according to this invention. (A) is sectional drawing in the cross section similar to FIG.1 (b) which shows the cross section of the protruding part of the pneumatic tire of a prior art example, (b) is a cross section of the protruding part of the pneumatic tire of a comparative example. It is sectional drawing in the cross section similar to FIG.1 (b) shown. (A) is sectional drawing in the cross section similar to FIG.1 (b) which shows the cross section of the protruding part of the pneumatic tire of Example 1, (b) is the protruding part of the pneumatic tire of Example 2. FIG. It is sectional drawing in the cross section similar to FIG.1 (b) which shows a cross section, (c) is sectional drawing in the cross section similar to FIG.1 (b) which shows the cross section of the protruding part of the pneumatic tire of Example 3. is there.

  Hereinafter, embodiments of the present invention will be described in detail. Although the pneumatic tire in the present embodiment is not shown in the drawings, as a basic structure, a pair of bead portions to be attached to the rim, a pair of sidewall portions continuous from the bead portion to the tire radial direction, and these A carcass composed of at least one carcass ply extending between the bead cores embedded in the bead part and extending in a toroid shape between these parts, and a crown of the carcass A belt comprising at least one belt ply disposed on the outer side of the tire in the radial direction of the tire.

  The pneumatic tire 1 includes a plurality of (four in this case) circumferential grooves 3 to 6 extending in the tire circumferential direction on the tread surface, and is divided into five land portion rows 8 to 12. Yes. The two land portion rows 8 and 12 located on the outermost side in the tire width direction are divided into a plurality of shoulder blocks 17 divided into a block shape by a plurality of lateral grooves 14 and 15 extending outward in the tire width direction from the circumferential grooves 3 and 6. , 18. The land portion rows 9 to 11 in the central region of the tread portion sandwiched between the land portion rows 8 and 12 are configured by rib-like land portions 21 to 23. A plurality of sipes 25 extending zigzag in the tire width direction are provided on the treads of the rib-like land portions 21 to 23 and the shoulder blocks 17 and 18 constituting the land portion rows 8 to 12. In addition, there is no limitation in the shape of the land part which comprises the land part row | line | columns 9-11, You may comprise the land part row | line | columns 9-11 with a block-shaped land part. In the present embodiment, the circumferential grooves 3 to 6 are formed in a zigzag shape. However, the present invention is not limited to this, and the circumferential grooves 3 to 6 may extend linearly or in a wave shape. In the present embodiment, the lateral grooves 14 and 15 are also bent and extended in the middle, but may be extended linearly or zigzag.

  Further, in the lateral grooves 14 and 15, raised portions 30 and 31 that are connected to the shoulder blocks 17 and 18 that protrude from the groove bottom and are adjacent to each other in the tire circumferential direction are provided. Here, the raised portions 30 and 31 are illustrated as extending over the entire length (the length in the tire width direction) of the lateral grooves 14 and 15, but the raised portions 30 and 31 are in the length direction of the lateral grooves 14 and 15. It may extend partially. And in this embodiment, as shown in the cross-sectional view of FIG. 1 (b), the raised portions 30, 31 are formed in a stepped shape so that the height of the top surface becomes higher toward the outer side in the tire width direction, Three top surfaces 33a, 33b, and 33c are provided from the inner side to the outer side in the tire width direction. The length of the three top surfaces 33a, 33b, 33c in the tire width direction is, for example, the length of the width direction edge (shoulder block width) of the adjacent shoulder block is W, and the length of 33a is 2 mm or more, W / 5 mm Hereinafter, the length of 33b is preferably in the range of W / 4 mm or more and W / 2 mm or less, and the length of 33c is preferably in the range of W / 3 mm or more and W / 2 mm or less. Further, the height of the three top surfaces 33a, 33b, 33c in the tire radial direction (the tire radial direction distance from the top surface to the groove bottom 27) is, for example, the groove depth (the tread surface 17a) of the adjacent circumferential grooves 3, 6. , 18a to the groove bottom 27 in the tire radial direction) is D, the height of 33a is 3 mm or more and D / 3 mm or less, and the height of 33b is D / 3 mm or more, 2 × D / 3 mm or less, 33c Is preferably in a range of 2 × D / 3 mm or more and D−1 mm or less.

  When the tire having the above-described configuration is mounted on a vehicle and subjected to load rolling, the shoulder blocks 17 and 18 have increased rigidity by connecting the shoulder blocks 17 and 18 adjacent in the circumferential direction by the raised portions 30 and 31. Thus, deformation can be suppressed and wear can be prevented from progressing locally. In particular, since the highest top surface of the three top surfaces 33a, 33b, and 33c of the raised portions 30 and 31 is disposed on the outer side in the width direction where the wear easily proceeds, the rigidity on the outer side in the width direction is further increased. Thus, uneven wear can be more effectively suppressed. At the same time, by placing the lower top surface of the raised portions 30 and 31 on the inner side in the width direction, even when the wear has progressed, on the inner side in the width direction where the contact pressure is large, the start when running on a wet road surface, The widthwise edge component of the shoulder block effective for stopping can be secured, and the desired wet performance can be maintained over a long period of time. Further, by forming the raised portions 30 and 31 in a stepped manner, the top surface of the raised portions 30 and 31 is exposed stepwise on the tread surface of the shoulder block, thereby preventing a sudden decrease in wet performance. it can.

  This will be explained with reference to the drawings. FIG. 2 (a) shows that a tire having a raised portion 31 ′ having a conventional general rectangular cross section in a lateral groove causes wear of the shoulder block 18 ′ to progress due to use. FIG. 2B is a cross-sectional view showing a state in which the portion 31 ′ is exposed on the tread surface 18a ′ of the shoulder block 18 ′, and FIG. 2B shows the state of the raised portion when wear similarly proceeds in the tire of the embodiment. It is sectional drawing shown. In the conventional raised portion, as shown in FIG. 2 (a), when the wear of the shoulder block 18 'progresses, all the raised portions are exposed to the tread at a certain point in time, and the edge component in the width direction becomes smaller. In addition, the wet performance is greatly reduced compared to that before the wear. On the other hand, as shown in FIG. 2 (b), the tire according to the present embodiment can ensure the width direction edge component because the top surface 33a on the inner side in the width direction remains even if the wear of the shoulder block 18 progresses. A sudden drop in wet performance can be avoided.

  By the way, when the circumferential grooves 3 and 6 extend at an angle α with respect to the circumferential direction as shown in FIG. 1A, the angle α is within a range of 10 ° to 30 °. Is preferred. The angle with respect to the circumferential direction of the circumferential grooves 3 and 6 as used herein refers to a straight line connecting inflection points adjacent in the circumferential direction in a trajectory following the edge of the land portion adjacent to the circumferential groove. The angle made with respect to. As a result, the edge component in the width direction can be given to the edge portions of the shoulder blocks 17 and 18 adjacent to the circumferential grooves 3 and 6, and the wet performance can be further improved. When the angle α exceeds 30 °, the shape of the corners of the shoulder blocks 17 and 18 becomes thin, so that the rigidity is lowered, which causes uneven wear and block baldness.

  Moreover, it is preferable that the groove widths of the circumferential grooves 3 and 6 are in a range of 7 to 15 mm. If the groove width is less than 7 mm, drainage performance during wet road running deteriorates. The uneven wear resistance performance decreases as the contact pressure increases due to the decrease in the contact area.

  Moreover, it is preferable that the groove width of the lateral grooves 14 and 15 is in the range of 4 to 8 mm. If the width is less than 4 mm, the width direction edge component does not function, and start and stop performance during wet road running deteriorates. Exceeding may cause a decrease in uneven wear resistance due to an increase in contact pressure due to a decrease in the contact area between the tire tread and the road surface.

  Moreover, the tire radial direction distance d1 from the treads 17a and 18a of the shoulder blocks 17 and 18 is the groove depth of the adjacent circumferential grooves 3 and 6 on the innermost top surface 33a of the raised portions 30 and 31 in the tire width direction. It is preferably larger than half of D (the tire radial direction distance from the treads 17a, 18a to the groove bottom 27). Further, the top surface 33a on the innermost side in the tire width direction of the raised portions 30 and 31 is more preferably configured such that the tire radial direction distance d1 ′ from the groove bottom 27 of the circumferential grooves 3 and 6 is 3 mm or more and the groove bottom 27 or less of the tire radial direction distance d2 ′ from 27 to the intermediate top surface 33b. According to this, at least the top surface 33a is not exposed to the tread surface until the wear of the shoulder block progresses to the end of the wear life, so that the edge component in the width direction can be secured.

  It is preferable that the tire radial direction distance from the treads 17a and 18a of the shoulder blocks 17 and 18 is 1 to 3 mm in the tire width direction outermost top surface 33c of the raised portions 30 and 31. This is because if the distance is less than 1 mm, the road surface and the top surface 33c are in contact with each other at the time of ground contact, and the lateral groove is partially blocked, so that the width direction edge component cannot be secured. This is because the desired uneven wear resistance may not be obtained because it cannot be ensured. Further, the distance d2 ′ in the tire radial direction from the groove bottom 27 of the circumferential grooves 3 and 6 to the intermediate top surface 33b is ½ or more of the groove depth D of the circumferential grooves 3 and 6 and 2/3. The following is preferable, and if it is less than 1/2, there is a risk that the desired uneven wear resistance performance may not be obtained due to deterioration in the rigidity balance of the raised portion, and if it exceeds 2/3, the edge component due to the groove is sufficient. The desired wet performance may not be obtained.

  Further, the tire width direction length of the outermost top surface 33c in the tire width direction of the raised portions 30 and 31 is 1/3 or more of the length (shoulder block width) W of the width direction edge of the adjacent shoulder block, 1 / It is preferable that it is 2 or less. If the length in the tire width direction of the top surface 33c is less than 1/3 of the shoulder block width W, sufficient rigidity may not be obtained, and a desired uneven wear resistance performance may not be ensured. When exposed on the tread, more than half of the edge component may be lost, and wet performance may not be ensured. Further, it is preferable that the position in the width direction of the outermost top surface 33c is located on the outer side in the width direction than the center position in the width direction of the adjacent shoulder block. Stiffness can be imparted by concentrating in the vicinity of the end, and uneven wear can be more effectively suppressed.

  Further, the length in the tire width direction of the top surface 33a on the innermost side in the tire width direction of the raised portions 30 and 31 is 2 mm or more, and 1/5 or less of the length W of the adjacent shoulder block in the width direction. Preferably, if it is less than 2 mm, the desired wet performance at the time of wear cannot be obtained, and if it exceeds 1/5 of the width W of the adjacent shoulder block in the width direction, the rigidity of the land portion decreases, and uneven wear resistance There is a risk that it may not be possible.

  The length in the tire width direction from the groove bottom 27 of the circumferential grooves 3 and 6 to the intermediate top surface 33b is not less than ¼ and not more than ½ of the length W of the edge in the width direction of the adjacent shoulder block. Preferably, if it is less than 1/4, the desired wet performance at the time of wear cannot be obtained, and if it exceeds 1/2, the rigidity of the land portion decreases, and uneven wear resistance may not be obtained.

  While the present invention has been described based on the illustrated examples, the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the claims. For example, in the above embodiment, as shown in FIG. 1A, the lengths in the width direction of the three top surfaces 33a, 33b, and 33c are equal to each other. Depending on the function required, such as setting the radially innermost top surface 33a to be long, and setting the radial outermost top surface 33c to be long when emphasizing the effect of suppressing uneven wear, What is necessary is just to set suitably. Similarly, if the height of the intermediate top surface 33b is increased, the rigidity is increased, which is advantageous for uneven wear resistance performance, and if the intermediate top surface 33b is set low, it is advantageous for sustainability of wet performance. . In the present embodiment, the top surfaces 33a, 33b, and 33c of the raised portions 30 and 31 are flat, but may be curved surfaces.

  Next, tires according to the present invention were prototyped and performance evaluations regarding uneven wear resistance performance and wet performance were performed, which will be described below. The tires of the conventional example, the comparative example, and the example all have a size of 295 / 75R22.5.

  The tires of the conventional example, the comparative example, and the example are the same in that the raised portions are provided in all the lateral grooves sandwiched between the shoulder blocks, but the shape of the raised portions is different for each tire. In addition, all the volumes of the raised portions are equal. In the tire of Example 1, according to the present invention, the shape of the raised portion is the shape shown in FIG. 4A, and the intermediate top surface 33b of the raised portion in the tire width direction is the groove depth D of the circumferential groove 6. The innermost top surface 33a is lower than that and the outermost top surface 33c is higher than that. Furthermore, the width direction length of the outermost top surface 33c is smaller than half of the shoulder block width W.

  In the tire of Example 2, the shape of the raised portion according to the present invention is the shape shown in FIG. 4B, and the height of the top surface 33 b of the raised portion 31 in the tire width direction is the groove depth of the circumferential groove 6. It differs from the tire of Example 1 in that it is higher than half the height D.

  In the tire of Example 3, the shape of the raised portion according to the present invention is the shape shown in FIG. 4C, and the length in the tire width direction of the outermost top surface 33c of the raised portion 31 is the shoulder block. It differs from the tire of Example 1 in that it is longer than half of the width W.

  The tire of the conventional example differs from the tire of Example 1 in that the height of the top surface of the raised portion is constant as shown in FIG. As shown in FIG. 3 (b), the tire of the comparative example has three top surfaces, but the three top surfaces are located closer to the top surface located on the outer side in the tire width direction from the tread surface of the shoulder block. This is different from the tire of Example 1 in that the distance is increased.

  In the uneven wear resistance test, each of the above test tires was assembled to a rim (8.25 × 22.5), and under the action of a tire internal pressure of 650 kPa and a load load of 1900 kg per tire, the speed was 60 km / h. After running for 000 km, the amount of heel-and-toe wear difference (height difference between the shoulder block kicking end and stepping end height) was measured and evaluated. Table 1 shows the difference in level in the conventional example as 100. The larger this value, the better the uneven wear resistance performance.

  In the wet performance test, each of the above test tires was assembled to a rim (8.25 × 22.5), and under an action of a tire internal pressure of 650 kPa and a load load of 1900 kg per tire on an asphalt road surface having an average water depth of about 2 mm. The vehicle was suddenly started from the stop state, and the evaluation was performed by measuring the time required to complete the 100m run. Depending on the degree of progress of wear, the new time is 0% wear, 50% wear and 100% wear are measured respectively. It shows with. It shows that wet performance is excellent, so that this value is large.

  From the evaluation results in Table 1, it can be seen that all of the tires of Examples 1 to 3 and the comparative example have improved uneven wear resistance and wet performance during wear as compared with the conventional example. Moreover, since the uneven wear resistance performance and wet performance during wear of the example are superior to the comparative example, the effect of suppressing uneven wear is high by arranging the volume of the bulging portion outside the tire width direction. In addition, it can be seen that desired wet performance can be obtained for a long period of time by securing the width direction edge component to the wear life inside the tire width direction inner side where the contact pressure is relatively high.

  Further, when the height of the top surface 33b in the tire width direction is higher than the case where the height of the top surface 33b in the tire width direction is half the depth of the circumferential groove, the uneven wear resistance is excellent. I understand that. It can also be seen that the wet performance during wear is superior when the tire width direction length of the outermost top surface in the tire width direction is shorter than half the shoulder block width.

  Thus, according to the present invention, it has become possible to provide a pneumatic tire that improves the uneven wear resistance performance of the shoulder block while preventing a sudden drop in wet performance during wear. In particular, the present invention can be more effectively applied to heavy-duty tires used for trucks and buses, where uneven wear in the shoulder region is likely to be a problem.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3-6 Circumferential groove 8-12 Land part row | line | column 14,15 Cross groove 17,18 Shoulder block 21-23 Rib-like land part 25 Sipe 30,31 Raised part 33a, 33b, 33c Top surface

Claims (3)

The tread portion is defined by a circumferential groove extending in the tire circumferential direction and a plurality of lateral grooves extending outward from the circumferential groove in the tire width direction, and ends at a tread end position in the tire width direction, or In a pneumatic tire comprising a plurality of shoulder blocks extending outward in the tire width direction beyond the tread end, and connecting the shoulder blocks adjacent to each other in the tire circumferential direction by a raised portion raised from the groove bottom of the lateral groove,
Each of the raised portions has three top surfaces that are different from each other in the tire radial direction from the tread surface of the adjacent shoulder block, and the three top surfaces are closer to the top surface located on the outer side in the tire width direction. A pneumatic tire characterized by being arranged so that a distance in a tire radial direction from the tire is reduced.   Of the three top surfaces of the raised portion, the innermost top surface in the tire width direction is a groove in the circumferential groove in which the distance in the tire radial direction from the tread surface defines a shoulder block adjacent to the raised portion. 2. The pneumatic tire according to claim 1, wherein the other two top surfaces have a distance in the tire radial direction from the tread surface that is smaller than the half length.   The length in the tire width direction of the top surface on the outermost side in the tire width direction among the three top surfaces of the raised portion is not more than half of the length in the tire width direction of the shoulder block adjacent to the raised portion. Item 3. The pneumatic tire according to Item 1 or 2.

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