JP2011162020A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having block groups demarcated by grooves and enhancing the steering stability on a dry road surface without degrading the on-ice performance. <P>SOLUTION: A tread rubber 8 has a cap-and-base structure consisting of a cap rubber 9 located on the outer circumferential side and a base rubber 10 located on the inner circumferential side. A block group is provided at least on a part of a tread surface 7, in which a plurality of polygonal blocks 13 demarcated by linearly extending grooves, having corners more than those of a pentagon, and independent from each other are densely arranged. The block number density S per unit actual grounding area of the block group given by Formula 1 is within a range of 0.003-0.04 pieces/mm<SP>2</SP>, where P(mm) is the reference pitch length of the polygonal block in the block group, W(mm) is the width of the block group, a (pieces) is the number of blocks demarcated by the reference pitch length P and the width W and present in the reference area of the block group, and N(%) is the negative ratio in the reference area. The rubber hardness of the base rubber 10 is larger than the rubber hardness of the cap rubber. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which block rigidity of a block defined by a groove is increased.

  In a conventional pneumatic tire, for example, as described in Patent Document 1, three main grooves extending linearly in the tread circumferential direction are provided in a tread portion, and a block is formed by a plurality of sub grooves between the main grooves. In general, it is widely practiced to form a polygonal shape to improve driving performance, braking performance and turning performance with respect to the road surface.

  However, in general, such a tire has a risk that the rigidity of the tread tread block is lowered and the collapse of the block is increased, which impairs the handling stability of the dry road surface.

Japanese Patent Laid-Open No. 2003-154813

  Accordingly, the present invention is to provide a pneumatic tire having improved driving stability on a dry road surface without deteriorating performance on ice, particularly in a pneumatic tire provided with a group of blocks partitioned by grooves.

で与えられる、ブロック群の単位実接地面積当たりのブロック個数密度Ｓが０．００３〜０．０４個／ｍｍ^２の範囲内であり、ベースゴムのゴム硬度が、キャップゴムのゴム硬度より大きいことを特徴とするものである。 A pneumatic tire according to the present invention includes a tread portion, a pair of sidewall portions, a pair of bead portions, and a carcass made of at least one carcass ply extending in a toroid shape between bead cores in each bead portion, A tread rubber disposed radially outward of the carcass, and the tread rubber has a cap-and-base structure including a cap rubber positioned on the outer peripheral side and a base rubber positioned on the inner peripheral side. In addition, at least a part of a block group in which a plurality of polygonal blocks independent of each other and having a number of pentagons or more, which are partitioned by a linearly extending groove, are arranged together is provided. When the reference pitch length of the polygon block in the block group is P (mm) and the width of the block group is W (mm), the reference pitch length Is defined by the width is W, the number of blocks existing in a reference zone of the block group a (number), the negative ratio in the reference zone and N (%) and,

The block number density S per unit actual ground contact area of the block group is in the range of 0.003 to 0.04 piece / mm ² , and the rubber hardness of the base rubber is larger than the rubber hardness of the cap rubber. It is characterized by.

Here, the “reference pitch length of the block” refers to the minimum unit of the repeated pattern of the block in one block row constituting the block group. For example, the pattern is defined by one block and a groove defining the block. If a repetitive pattern is specified, the reference pitch length of the block is the sum of the tread circumferential length of one block and the tread circumferential length of one groove adjacent to the tread circumferential direction of this block. To do.
Note that “the number of blocks a in the reference area of the block group” is the number of blocks remaining in the reference area with respect to the surface area of the block, when the block exists inside and outside the reference area and cannot be counted as one. For example, in the case of a block straddling the inside and outside of the reference area and having only half of the reference area, it is counted as 1/2.

“Block group width W” refers to the tread width direction length of the block group formed by densely arranging the blocks. For example, when the block group exists in the entire tread, it refers to the tread ground contact width, and it surrounds the tread tread surface. When a groove or the like is provided and the block group does not exist in the entire tread, the width of the block group in the land portion partitioned by the circumferential groove or the like is used.
“Actual contact area” of a block group refers to the total surface area of all blocks in the reference area of the block group, that is, the reference area defined by the product of the reference pitch length P and the width W. The area obtained by subtracting the area of the groove that divides each block from the area of.

More preferably, in such a tire, the cap rubber is made of a foamed rubber layer, and the cap rubber has a JIS A hardness of 25 to 50.
Here, the rubber hardness is a hardness measured under a room temperature condition of 25 ° C. using a type A tester in a durometer hardness test according to JIS K6253.

Preferably, the maximum thickness of the base rubber is 5% or more of the maximum height of the polygonal block.
Here, “maximum thickness of base rubber” and “maximum height of block” are industrial standards effective in the region where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK In Europe, ETRTO (European Tire and Rim Technical Organization) STANDARDDS MANUAL, in the US TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK, etc. It shall be measured in a state filled with the maximum air pressure specified accordingly.

  By the way, it is preferable to arrange the polygonal blocks in a zigzag shape in the tread circumferential direction.

In the pneumatic tire of the present invention, the block number density S (units / mm ² ) per unit actual contact area of the block group G is formed in the range of 0.003 to 0.04 units / mm ^2. Compared with the density of tires of s = 0.002 pieces / mm ² or less, the tire of the present invention has an increased density S, ensuring excellent grounding performance and edge effect, and efficient removal of water film by blocks By realizing the above, it is possible to achieve both the block rigidity and the edge effect at a higher level, and it is possible to dramatically improve the performance on ice. In addition, the deformation between the blocks is absorbed by the groove between the blocks, and the deformation of the block makes the deformation of the block uniform with respect to the input, ensuring excellent grounding properties, and the tire rotation direction between the stepping part and the kicking part of the block The wear energy generated in the ground contact surface can be reduced. As a result, both wear resistance and rolling resistance can be achieved at a high level.

  That is, when S is less than 0.003, the surface area of the block is increased, and there is a possibility that the grounding property of the tread surface cannot be improved. On the other hand, when S exceeds 0.04, Even when the sipe is disposed, it is difficult to achieve a desired block rigidity.

  Further, by making the rubber hardness of the base rubber larger than the rubber hardness of the cap rubber, it is possible to reinforce the inner rigidity in the tire radial direction, and to reduce the collapse of the block bottom. As a result, the block rigidity is increased, and the steering stability on the dry road surface and the wet road surface can be improved.

  In the pneumatic tire of the present invention, the above-described configuration can achieve both on-ice performance and dry steering stability performance.

It is a tire width direction sectional view in the state where a tire was assembled to an application rim and specified air pressure was filled, showing an embodiment of a pneumatic tire. It is a partial development view of a tread pattern showing one embodiment of a pneumatic tire of the present invention.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a meridian cross-sectional view of a tire, showing an embodiment of a pneumatic tire assembled to an application rim.

  In the figure, 1 is a tread portion, 2 is a pair of sidewall portions extending radially inward continuously to the respective side portions of the tread portion 1, and 3 is a radially inward direction of the sidewall portion 2. The consecutive bead parts are shown in FIG.

  Here, for example, around the pair of bead cores 4 embedded in the bead part 3, each side part is wound up and moored, for example, on the outer peripheral side of the crown region of the carcass 5 made of one carcass ply, 2 or more of rubber-coated belt layers, in the drawing, two inclined belt layers 6 and a tread rubber 8 forming a tread tread surface 7. Is disposed.

  The tread rubber 8 is arranged in a so-called cap-and-base structure including a cap rubber 9 positioned on the outer peripheral side and a base rubber 10 positioned on the inner peripheral side.

FIG. 2 is a partial development view of a tread pattern showing an embodiment of the pneumatic tire of the present invention.
The tread tread surface 7 includes a plurality of horizontally long straight thick grooves 11 extending in the tread width direction, and four slants extending from the ends of the thick grooves 11 within a range of 10 to 80 ° with respect to the tread circumferential direction. A linear narrow groove 12 extending in the direction is provided.
In the figure, a block 13 having an octagonal outline is defined by four thick grooves 11 and four narrow grooves 12, and a block group G is formed by concentrating these blocks 13. , Present on the entire tread surface 7.
Here, the respective blocks 13 are arranged in a staggered manner in the tread circumferential direction.

  Here, each of the thick grooves 11 has, for example, a groove width BGL of 1.2 to 10 mm, a groove depth of 2 to 11 mm, and a groove extension length of 1.2 to 10 mm. For example, the groove width BGO can be set to 0.1 to 1.2 mm, the groove depth can be set to 1 to 10 mm, and the extended length of the groove can be set to 1 to 15 mm.

  By disposing such a thick groove 11, water can be retained in the thick groove 11 at the time of ground contact, and the steering stability of the wet road surface can be improved. By disposing such a narrow groove 12, it is possible to reduce the decrease in block rigidity and improve the grounding performance of the block 13 as compared with the case where the thick groove is not divided from the narrow groove.

Further, the tread circumferential length BL of the block 13 is 5 to 25 mm, the tread width direction length BW is 5 to 25 mm, the surface area is 25 to 330 mm ² , and the distance BGW between adjacent blocks in the tread width direction is 2. It can be set to a range of 5 to 10 mm.

として表される、ブロック群Ｇの単位実接地面積当たりのブロック個数密度Ｓ（個／ｍｍ^２）、すなわち接地面積（溝分を除いた）中の単位面積（ｍｍ）当たり小ブロックが配置された部分のブロック個数は、０．００３〜０．０４個／ｍｍ^２、好ましくは０．００３〜０．０３５個／ｍｍ^２の範囲で形成し、ベースゴム１０のゴム硬度を、キャップゴム９のゴム硬度より大きくする。 In this tire, the reference pitch length of the block 13 in the block group G is P (mm), and the width (mm) of the block group G is the entire tread tread surface 7 in the figure. The number of blocks 13 existing in the reference area Z (area shown by hatching in the figure) of the block group G, which is divided by the width TW, the reference pitch length P, and the width TW, is a (number). When the negative rate of N is N (%)

The block number density S (units / mm ² ) per unit actual ground contact area of the block group G, that is, represented by as follows: small blocks are arranged per unit area (mm) in the ground contact area (excluding the groove) The number of blocks in the portion is 0.003 to 0.04 piece / mm ² , preferably 0.003 to 0.035 piece / mm ² , and the rubber hardness of the base rubber 10 is the rubber of the cap rubber 9. Make it larger than the hardness.

By the way, the negative rate N of the block group G is preferably 5% to 50%, and by setting this range, the steering stability can be improved.
That is, when the negative rate N is less than 5%, the groove area is too small and the drainage performance is insufficient, and the size of each block may be too large, making it difficult to achieve the required edge effect. On the other hand, if it exceeds 50%, the ground contact area becomes too small, and the steering stability tends to decrease.

  In such a tire, the blocks are densely arranged while securing a sufficient groove area in the block group G, so that the total edge length and edge direction of each block 13 (edges in different directions) Number) and an excellent edge effect can be exhibited. In addition, since the size of the block 13 is reduced, the contact performance of each block can be improved, so that braking performance and steering stability on a road surface having a low friction coefficient μ such as an ice surface and a wet road surface can be obtained. Can be improved. In addition, by reducing the size of each block 13, the distance from the central area of the block 13 to the peripheral edge of the block can be reduced, and the water film removal effect by the block 13 can be improved.

In such a pneumatic tire, preferably, the polygon block 13 having a number of pentagons or more is arranged in a zigzag shape in the tread circumferential direction, so that the dense arrangement of the blocks 13 can be easily realized. When rolling, under the formation of a larger number of blocks 13, each edge can be made to act sequentially to exert a more excellent edge effect, and between the blocks 13 adjacent in the tread width direction to the road surface. Since the grounding timing can be shifted, pattern noise can be reduced.
Further, the blocks 13 can be arranged in a zigzag shape in the tread circumferential direction, and the block number density D can be set high so that the adjacent blocks can be supported by each other when a high load is applied to the block 13. According to this, it becomes possible to further increase the rigidity of the block 13 and further improve the wear resistance.

  In the case where the block group G is arranged on the entire tread surface, the performance of the icy road surface can be particularly improved. For example, the block group G is arranged on a part of the tread surface so as to be compatible with other performances. You can also.

Preferably, the cap rubber 9 is a foamed rubber layer, and the cap rubber 9 has a JIS A hardness in the range of 25-50.
With such a configuration, it is possible to improve the handling stability of the dry road surface without lowering the block rigidity of the polygonal block 13, and to improve the braking performance on ice using the low hardness rubber of foamed rubber.
Then, the JIS A hardness of the base rubber 10 can be made larger than 25. Preferably, it is set as the range of 30-70.

And preferably, the maximum thickness of the base rubber is 5% or more of the maximum height of the polygonal block, more preferably in the range of 5 to 95%.
By setting it within this range, it is possible to improve the performance on ice by applying a low hardness rubber to the tread tread surface 7 in particular, and to achieve both the performance on ice and the dry steering stability performance.

  The rubber composition used for the pneumatic tire of the present invention contains at least one diene rubber selected from the group consisting of natural rubber (NR), polyisoprene rubber (IR) and polybutadiene rubber (BR), and is necessary. Depending on the case, other synthetic rubbers may be included. Examples of other synthetic rubbers include styrene-butadiene copolymer rubber (SBR), ethylene-propylene-diene rubber (EPDM), butadiene-isoprene copolymer rubber, and styrene-isoprene. Examples include copolymer rubber, styrene-isoprene-butadiene rubber, chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR), and the like. These rubber matrices may be used alone or in a blend of two or more.

  This rubber composition is preferably sulfur crosslinkable, and sulfur is suitably used as a vulcanizing agent.

The reinforcing filler of the rubber composition is preferably carbon black and / or an inorganic filler, and the inorganic filler is preferably silica.
When carbon black is blended in the rubber composition, it is preferably blended in the cap rubber 9 at 25 to 65% by weight and in the base rubber 10 at 50 to 80% by weight.

When silica is blended in the rubber composition, it is preferable that 1 to 20% by mass of a silane coupling agent is blended with respect to the silica.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-methyldimethoxysilylpropyl) tetrasulfide, and bis (3-triethoxy Silylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (3-methyldimethoxysilylpropyl) disulfide, bis (3-triethoxysilylethyl) disulfide, Bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-methyldimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylene) Le) trisulfide and,
During _{^{R 1 x R 2 y R 3}} z Si-R 4 -S-CO-R 5 [ wherein, ^{R 1 is, R 6 O-, R 6 C} (= O) O-, R 6 R 7 C = NO ^{-, R 6 R 7 NO-,} R 6 R 7 N- and - a (OSiR ⁶ R ⁷⁾ _n is selected from (OSiR ⁵ R ⁶ R ⁷⁾ and the number of carbon atoms is 1 to 18 (where, ^{R 6} and R ⁷ is independently selected from an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, and an aryl group, and has 1 to 18 carbon atoms and n is 0 to 10); R ² is Selected from hydrogen or an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group, a cycloalkenyl group and an aryl group; R ³ represents a — [O (R ⁸ O) _m ] _0.5 — group (provided that , R ⁸ is and is selected from an alkylene group and cycloalkylene group Prime is 1 to 18, m is an 1 to 4); be x + y + 2z = 3,0 ≦ x ≦ 3,0 ≦ y ≦ 2,0 ≦ z ≦ 1; R 4 is an alkylene group, Is selected from a cycloalkylene group, a cycloalkylalkylene group, an alkenylene group, an arylene group and an aralkylene group, and has 1 to 18 carbon atoms; R ⁵ is an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an aryl group And an aralkyl group and having 1 to 18 carbon atoms]
And sulfur-containing alkoxysilane compounds.

  Further, the rubber composition used in the tire of the present invention includes, in addition to the reinforcing filler, a compounding agent usually used in the rubber industry, for example, an antioxidant such as an antioxidant or an ozone degradation inhibitor. , Crosslinking agent, vulcanization accelerator, vulcanization retarder, chelating agent, tackifier, processing aid, wax, oil, stearic acid, softener, coupling agent, vulcanization accelerator, vulcanizing agent In addition, one or two or more of a process oil, a scorch inhibitor, zinc oxide, stearic acid, a thermosetting resin, a thermoplastic resin, and the like can be added as necessary. Depending on the intended use of the rubber composition, these rubber chemicals can each be used in amounts normally used in the rubber industry. It can select suitably in the range which does not injure the objective of this invention, and can mix | blend within the range of a normal compounding quantity. As these compounding agents, commercially available products can be suitably used.

  The vulcanization accelerator that can be used in the present invention is not particularly limited, and examples thereof include M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), and CZ (N-cyclohexyl-2-benzothiazyl). And guanidine vulcanization accelerators such as DPG (diphenylguanidine) and the like.

  Furthermore, examples of the antioxidant include 3C (N-isopropyl-N′-phenyl-p-phenylenediamine, 6C [N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine], AW (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline), high-temperature condensate of diphenylamine and acetone, and the like.

  Examples of the plasticizer include phthalic acid derivatives such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di- (2-ethylhexyl) phthalate, and di-n-octyl phthalate.

  Examples of the foaming agent that can be used in the rubber composition used in the tire of the present invention include azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, p, p'- Oxybisbenzenesulfonyl hydrazide (OBSH), ammonium bicarbonate generating carbon dioxide, sodium bicarbonate, ammonium carbonate, nitrososulfonylazo compound generating nitrogen, N, N′-dimethyl-N, N′-dinitrosophthalamide , Toluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, p, p′-oxybisbenzenesulfonyl semicarbazide and the like. Among these foaming agents, azodicarbonamide (ADCA) and dinitrosopentamethylenetetramine (DPT) are preferable from the viewpoint of production processability. Moreover, these foaming agents may be used individually by 1 type, and may use 2 or more types together.

  The rubber composition used in the pneumatic tire of the present invention is obtained by kneading using a kneading machine such as a Banbury mixer, a roll, an internal mixer or the like according to a desired formulation, and after extrusion molding, tire molding After being molded on a machine by a normal method to form a green tire, vulcanization is performed to form a tread rubber for the tire.

Next, a tire having a structure as shown in FIGS. 1 and 2 and having a size of 195 / 65R15 was manufactured as a prototype, and the specifications shown in Tables 1 and 2 and the specifications shown in Table 3 were used. Example tires 1 to 3 and Comparative Example tires 1 to 3 in which the tires were changed were measured for steering stability on dry road surfaces, steering stability on wet road surfaces, and wear resistance.
In addition, since the comparative example tire does not require modification about structures other than the tread portion, it was assumed to be in conformity with the example tire.

1) Polybutadiene rubber: Ube Industries UBEPOL BR (registered trademark) 150L
2) Carbon black: ISAF {N2SA (m ² / g) = 115 (m ² / g)}, manufactured by Asahi Carbon Co., Ltd., trade name “Asahi # 80” 190 m ² / g)
3) Silica: Tosoh Silica, trade name “Nipsil AQ” (BET specific surface area = 190 m ² / g)
4) Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, manufactured by Degussa, trade name “Si69”
6) Anti-aging agent IPPD: N-isopropyl-N′-phenyl-P-phenylenediamine 7) Vulcanization accelerator MBTS: Dibenzothiazyl disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller DM”
8) Vulcanization accelerator CBS: N-cyclohexyl-2-benzothiazylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller CZ”

[Operation stability on ice surface]
Each of Example Tires 1 to 3 and Comparative Example Tires 1 to 3 is assembled on a rim of size 6J × 15, and the internal pressure is 210 kPa, and four test tires are mounted on a 1600 cc class passenger car. After running 200 km on a general asphalt road, the tire was locked from 40 km / hr on a -1 ° C. ice / snow road surface, and the braking distance until stopping was measured. Table 4 shows the evaluation results.
In addition, it represents as an index with the braking distance of the comparative example tire 1 being 100, and the larger the index, the better the performance on the icy and snowy road surface.

[Operation stability on dry road surface]
Each of Example Tires 1 to 3 and Comparative Example Tires 1 to 3 is assembled to a rim of size 6J × 15, mounted on a vehicle with an internal pressure of 210 kPa, and run on various test modes of asphalt in various driving modes. This was done by comprehensively evaluating the braking performance, acceleration performance, straight travel performance and cornering performance of the test driver. The evaluation results are shown in Table 4.
In addition, the index value in a table | surface was calculated | required as a control using the value of the comparative example tire 1, and it shows that the steering stability of a dry road surface is excellent, so that an index is large.

[Abrasion resistance]
Each of Example Tires 1 to 3 and Comparative Example Tires 1 to 3 is mounted on a rim having a rim size of 6 J × 15, the internal pressure is 210 kPa, the load mass is 4.4 kN, the average speed is 40 km / h, and the actual road is 20000 km. It traveled, the amount of remaining grooves was evaluated, and the result is shown in Table 4.
In addition, the value in a table | surface was calculated | required on the basis of the value of the comparative example tire 1, and shows that abrasion resistance is excellent, so that an index | exponent is large.

  From the results of Table 4, the Example tires 1 to 3 were able to improve the handling stability of the dry road surface, the handling stability of the wet road surface, and the wear resistance compared to the comparative example tires 1 to 3.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass 6 Inclined belt layer 7 Tread tread 8 Tread rubber 9 Cap rubber 10 Base rubber 11 Thick groove 12 Narrow groove 13 Block G Block group

Claims (4)

A tread portion, a pair of sidewall portions, a pair of bead portions, a carcass made of at least one carcass ply extending in a toroidal shape between bead cores in each bead portion, and a radially outer side of the carcass. With the tread rubber set,
The tread rubber is a cap-and-base structure consisting of a cap rubber located on the outer peripheral side and a base rubber located on the inner peripheral side,
At least a part of a block group in which a plurality of polygonal blocks each having a pentagonal number or more and separated from each other are arranged densely on each other is provided on the tread tread surface by a linearly extending groove. In pneumatic tires,
The reference area of the block group defined by the reference pitch length P and the width W, where P (mm) is the reference pitch length of the polygon block in the block group and W (mm) is the width of the block group The number of blocks existing in a is a (piece), the negative rate in the reference area is N (%),

The block number density S per unit actual ground contact area of the block group is within a range of 0.003 to 0.04 / mm ² ,
A pneumatic tire characterized in that the rubber hardness of the base rubber is larger than that of the cap rubber.   The pneumatic tire according to claim 1, wherein the cap rubber is formed of a foam rubber layer, and the cap rubber has a JIS A hardness in a range of 25 to 50.   The pneumatic tire according to claim 1 or 2, wherein a maximum thickness of the base rubber is 5% or more of a maximum height of the polygonal block.   The pneumatic tire according to any one of claims 1 to 3, wherein the polygonal blocks are arranged in a zigzag shape in the tread circumferential direction.

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