JP5102062B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having, as a belt, a circumferential belt layer in which reinforcing elements such as cords and filaments extend along the tire equator, and particularly to a heavy-duty pneumatic tire.

In recent years, due to demands for higher speeds and lower floors of vehicles, mounted tires have become flatter, and accordingly, the amount of radial growth of the tread portion when applying standard internal pressure tends to increase further. This increase in the amount of radial growth in the tread portion amplifies stress concentration at the belt end portion and leads to a decrease in durability at that portion, and is a factor that particularly causes belt end separation early.
In other words, in a tire with a small aspect ratio, there is a problem in that the amount of diameter growth in the tread portion, particularly in the vicinity of the shoulder portion, when inner pressure is applied increases, so in the circumferential belt layer by reinforcing elements arranged in the tire circumferential direction. A technique for suppressing diameter growth is required.

Regarding the technology for suppressing the radial growth in the circumferential belt layer, Patent Document 1 discloses that a large number of cords or filaments cross each other across the tire equator at an inclination angle of 10 to 40 ° with respect to the tire equator around the carcass. The tire equator comprises a plurality of cords or filaments of reinforcing elements having at least two layers of slanted belts, and at least one layer of corrugated or zigzag shape located under the slanted belts. A structure having a circumferential belt layer with strips oriented along the axis is disclosed.
JP-A-2-208101

  However, when the flatness ratio is further reduced, specifically, when the flatness ratio, which is the ratio of the cross-sectional height to the cross-sectional width of the tire, is 0.70 or less, the width of the circumferential belt layer is not further increased. As a result, it is difficult to suppress the intended diameter growth. However, increasing the circumferential belt layer width leads to the following new problem.

  That is, when the circumferential belt layer width is widened, a tensile input (hereinafter referred to as a result of the belt layer extending in the circumferential direction due to bending of the circumferential end of the circumferential belt layer in the contact area and bending in the circumferential direction as the tire travels) , Tensile amplitude input) repeatedly acts strongly, and as a result, the cord is likely to undergo fatigue fracture at the end in the width direction of the circumferential belt layer.

  Thus, when the circumferential belt layer is widened, the most serious problem is fatigue breakage of the cord at the end in the width direction of the circumferential belt layer. This is because the tensile amplitude input acts on the cord at the end of the circumferential belt layer as the tire travels, and suppressing the tensile amplitude input is indispensable for solving this problem.

  In order to ensure wear resistance performance, it is necessary to dispose the inclined belt layer wider than the circumferential belt layer and to increase the in-plane shear rigidity of the tread portion.

In order to solve the above problem, the applicant company previously stated that "the width of the circumferential belt layer is 60% or more of the total width of the tire, and the width of at least one inclined belt layer is that of the circumferential belt layer. It is wider than the width, and further, in the circumferential belt layer, the elastic modulus of the cord arranged on the width direction end portion side is lower than the elastic modulus of the cord arranged on the inner side in the width direction of the cord. "Pneumatic tire" was developed and proposed in Japanese Patent Application No. 2006-349481.
This technique intends to improve the durability of the belt by suppressing the fatigue fracture of the cord by adjusting the elastic modulus in the width direction of the cord embedded in the circumferential belt layer. Furthermore, the width of the inclined belt layer is made wider than the width of the circumferential belt layer to increase the in-plane shear rigidity of the tread portion to ensure wear resistance.

In the pneumatic tire proposed in the above-mentioned Japanese Patent Application No. 2006-349481, when forming the end portion in the width direction of the circumferential belt layer by spiral winding of a rubber-coated strip having a low elastic modulus, There is a fear that the circumferential distribution of the number of laminated strips tends to be non-uniform, and the expected belt durability is not improved.
That is, the present invention relates to the improvement of the pneumatic tire proposed in the above-mentioned Japanese Patent Application No. 2006-349481, and the belt durability is further improved by preventing the above-mentioned problems. With the goal.

  The inventors of the present invention have intensively studied how to make the circumferential distribution of the number of laminated strips uniform when forming the circumferential end of the circumferential belt layer by spiral winding of the strip. It has been found that it is effective to devise a strip winding structure at the end in the width direction, and the present invention has been completed.

That is, the gist of the present invention is as follows.
(1) At least one layer in which a carcass straddling a toroidal shape between a pair of bead portions is used as a skeleton, and a large number of cords extending along the equatorial plane of the tire are coated with rubber on the radially outer side of the crown portion of the carcass And a belt in which at least two inclined belt layers in which a plurality of cords extending in a direction inclined with respect to the equatorial plane of the tire are covered with rubber are arranged in order, and the diameter of the belt A tire with a tread on the outside in the direction,
The width of the circumferential belt layer is 60% or more of the total width of the tire;
The width of at least one inclined belt layer is wider than the width of the circumferential belt layer;
When each circumferential belt layer is partitioned into a width direction center region and a width direction end region located outside the width direction center region, the elastic modulus of the cord disposed in the width direction end region is Lower than the elastic modulus of the cord arranged in the center area in the width direction,
The circumferential belt layer has at least a two-layer structure in the width direction end area, and the width direction end area is made of rubber with one or more cords from the inner end adjacent to the width direction central area. After winding the coated strip along the equatorial plane of the tire for a circumference of 80% or more and less than 100% of the circumference of the crown of the carcass, the width of the belt with respect to the remaining circumference of one circumference Winding from the inner side to the outer side while shifting by an amount of movement within the strip width, the first circumference is formed, and then the second circumference is wound along the equator plane of the tire. After winding along the equatorial plane of the tire for a circumference of ~ 90%, within the strip width from the outside in the width direction of the belt to the inside for the remaining 10-20% of the circumference Winding while shifting by the amount of movement A pneumatic tire is formed by forming a third circumference and then winding the fourth circumference along the equator plane of the tire.

(2) The pneumatic tire according to (1), wherein a moving amount of the first and third strips of the strip is a strip width.

(3) The pneumatic tire according to (1) or (2), wherein a width of the inclined belt layer is 65% or more of a total width of the tire.

(4) The low elastic modulus cord is an extensible metal cord having an initial elongation, and the high elastic modulus cord is a non-extensible metal cord molded in a linear shape, a wave shape or a zigzag shape. The pneumatic tire according to (1), (2) or (3), characterized in that

(5) The pneumatic tire according to any one of (1) to (4), wherein the low elastic modulus cord is an organic fiber cord, and the high elastic modulus cord is a metal cord.

(6) The elastic modulus of the low elastic cord and the high elastic cord at a tensile strain of 1.8% is in a range of 40 GPa to 100 GPa and 80 GPa to 210 GPa, respectively (1 The pneumatic tire according to any one of (5) to (5).

According to the present invention, by expanding the circumferential belt layer width, suppressing the remarkable tread diameter growth particularly in a tire having a small aspect ratio, and adjusting the elastic modulus of the cord embedded in the circumferential belt layer, In particular, it is possible to provide a tire with a small aspect ratio that suppresses fatigue breakage of the cord at the end portion of the circumferential belt layer and greatly improves the durability of the belt.
Further, since the inclined belt layer is arranged wider than the circumferential belt layer and the in-plane shear rigidity of the tread portion is increased, it is possible to ensure excellent wear resistance.

  Furthermore, by devising the winding of the strip according to the present invention, it is possible to provide a structure in which the widthwise end region of the circumferential belt layer is reliably laminated in the radial direction over a wide range, so that the stress applied to the cord is made uniform Thus, the durability of the belt can be further improved.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross section in the width direction of a tire according to the present invention. On the radially outer side of the crown portion of the carcass 1 straddling a toroidal shape between a pair of bead portions (not shown), at least one layer in which a large number of cords extending along the tire equator CL are covered with rubber, illustrated example The two circumferential belt layers 2a and 2b and a plurality of cords extending in a direction inclined with respect to the tire equator CL are covered with rubber, and at least two layers are arranged in a direction in which the cords cross each other between the layers. In the illustrated example, a belt 4 in which two inclined belt layers 3 a and 3 b are sequentially laminated is provided, and a tread 5 is arranged on the outer side in the radial direction of the belt 4.

The width BW ₂ of the circumferential belt layers 2a and 2b is preferably set to 60% or more of the total width TW of the tire, and more preferably set to 70% or more. This is because the region where the radial growth is large is up to a region of 60% to 70% of the total tire width TW, and therefore it is necessary to arrange a circumferential belt layer for suppressing the radial growth in that region. . The upper limit of the width BW ₂ of the circumferential belt layer 2a and 2b, the restrictions that fit into the prescribed size of the tire shape, preferably 90%.

Further, at least one inclined belt layer, in the illustrated example, the width BW _3a of the inclined belt layer 3a needs to be wider than the width BW ₂ of the circumferential belt layers 2a and 2b. This is because the in-plane shear rigidity of the tread portion necessary for tire wear performance and cornering performance is ensured.
The width BW _3b of the remaining inclined belt layer 3b is preferably wider than the circumferential belt layers 2a and 2b in order to improve the in-plane shear rigidity of the tread portion, and in particular to improve the wear performance of the tire. Further, in the example shown in FIG. 1, the width BW _3a of the inclined belt layer 3a is wider than the width BW _3b of the 3b, Thus, it is preferable to set different widths. This is because there is a concern that the separation resistance at the end of the belt layer is deteriorated because the rigidity is suddenly changed when the width is the same.

In addition, the width of the inclined belt layers 3a and 3b is preferably 65% or more of the total width TW of the tire. This is because the wear performance is maintained when the cords of the inclined belt layer 3a and the cords 3b intersect within a range of 65% or more of the total tire width TW. Moreover, it is preferable that the upper limit of the width | variety of inclination belt layer 3a, 3b shall be 90% from the restriction | limiting of accommodating a tire shape in a prescribed dimension.
If the cord of the inclined belt layer is inclined at 40 ° or more, preferably 50 ° or more with respect to the tire equator CL, both wear performance and durability performance can be achieved. Because, if the inclination angle of the cord of the inclined belt layer with respect to the tire equator CL is less than 40 °, the deformation of the inclined belt layer at the time of tire contact increases, resulting in an increased strain burden on the inclined belt layer and the circumferential belt interlayer rubber. This is because separation between the layers tends to occur.

  In the example shown in FIG. 1, the circumferential belt layers 2a and 2b have the same width, but may have different widths. In particular, when the strength of the central portion in the width direction of the circumferential belt layer is increased, only one layer may be arranged wider and the other layer may be made narrower.

Further, if the width of the circumferential belt layer is increased, the cord is likely to be fatigued at the outer end in the width direction of the circumferential belt layer, and it is difficult to obtain a sufficiently satisfactory tire life. This is because the amplitude input in the tensile direction acts on the cord at the end of the circumferential belt layer as the tire travels, and it is indispensable to suppress this tensile amplitude input to solve this problem. .
Therefore, in the present invention, the elastic modulus of the cord disposed on the outer side in the width direction is made lower than the elastic modulus of the cord disposed on the inner side in the width direction of the circumferential belt layer. The tensile amplitude input concentrated on the end of the circumferential belt layer is suppressed.

  That is, in a running tire, a tensile amplitude input acts on the end of the circumferential belt layer. This tensile amplitude input is caused by the cord being stretched in the circumferential direction on the ground contact surface on the tread end side of the tire, where the maximum tensile stress acts, and in the non-contact area of the tread end, the tensile stress at the time of filling with internal pressure acts. Because. In order to suppress the amplitude of the tensile stress, it is conceivable to reduce the burden on the tire (reduce the amount of bending of the tire), but this method cannot satisfy the riding comfort of the tire.

  That is, when the cord is stretched in the circumferential direction of the tire within the ground contact surface, if the elastic modulus of the cord at the end in the width direction of the circumferential belt layer corresponding to the ground contact surface is low, the tensile stress applied to the cord is low. Become. However, if the elastic modulus of all the cords in the circumferential belt layer is lowered, the amount of radial growth due to internal pressure filling becomes large, and it becomes difficult to maintain the tire shape. Therefore, in the width direction of the circumferential belt layer, the cord elastic modulus on the outer side in the width direction corresponding to the vicinity of the end portion is made lower than the elastic modulus of the cord on the inner side in the same width direction, so If the increase in the amount is made the same as much as possible, the stress amplitude at the end portion in the width direction of the circumferential belt layer on the ground contact surface is effectively suppressed, so that fatigue breakage of the cord can be suppressed.

  The elastic modulus of the cord arranged on the outer side in the width direction of the circumferential belt layer is 0.3 to 0.8 times the elastic modulus of the cord arranged on the inner side in the width direction of the cord. It is effective for suppressing the amplitude of the tensile stress.

Here, as shown in the plan development view of the circumferential belt layer in FIGS. 1B and 1C, each circumferential belt layer is placed outside the width direction central region 2 </ b> C and the width direction central region 2 </ b> C in the width direction. When the width direction end area 2E ₁ and 2E ₂ are partitioned, the elastic modulus of the cord 6 arranged in the width direction end area 2E ₁ and 2E ₂ is equal to that of the cord 7 arranged in the width direction central area 2C. Lower than elastic modulus.

That is, the cord arrangement shown as the circumferential belt layers 2a and 2b in FIG. 1 has an elastic modulus in comparison with the cord 7 arranged in the width direction end region 2E ₁ and 2E ₂ of the circumferential belt layer in the width direction central region 2C. A plurality of low cords (hereinafter referred to as “low elastic modulus cords”) 6 are arranged, and the low elastic modulus cord 6 has an elastic modulus higher than that of the low elastic modulus cord 6 in the center region 2C in the width direction inside the belt width direction. A plurality of high cords (hereinafter referred to as “high elastic modulus cords”) 7 are arranged.
Thus, as the circumferential belt layer according to the present invention, 1 to several tens of low elastic modulus cords 6 are arranged in the width direction end regions 2E ₁ and 2E ₂ , and the high elastic modulus cord 7 is arranged in the central region 2C in the width direction. Basically it is arranged.

The width t of each widthwise end portion area _2E 1, 2E ₂ is preferably from 5% to 20% of the width BW ₂ of the circumferential belt layer. This is because if the width t is less than 5% of the total width, a cord having a high elastic modulus exists in a region where the stress amplitude to the circumferential belt layer is large, so that there is still a high possibility of breakage. This is because it is difficult to suppress an increase in diameter growth.

Furthermore, the width direction end regions 2E ₁ and 2E ₂ of the circumferential belt layers 2a and 2b have at least a two-layer structure, and a strip S in which one or a plurality of cords are covered with rubber is formed on the carcass 1 It is wound around the crown and molded. This forming procedure will be described below with reference to FIG. 2, taking the width direction end region 2E ₁ as an example.
That is, as shown in FIG. 2 (a), 1 present or strip S coated with rubber plurality of codes, from the inner end IE adjacent widthwise central region 2C of the widthwise end portion area 2E ₁ of the belt From the inner side to the outer side in the width direction, after winding along the equator plane CL of the tire with respect to a peripheral length of 80% or more and less than 100% of the outer peripheral length L of the crown portion of the carcass 1, the remaining peripheral length of one peripheral length That is, the first circumference is formed by winding around a circumference of 20% or less of the circumference, while shifting from the inner side in the belt width direction to the outer side with a shift amount within the width SW of the strip S. In the illustrated example, after winding along the equator plane CL of the tire with respect to the circumferential length L of 90% of the crown portion outer circumferential length L of the carcass 1, the remaining 10% of the circumferential length of the belt is Winding is performed while shifting from the inner side to the outer side in the width direction by the amount of movement of the width SW of the strip S.

Thereafter, as shown in FIG. 2B, the second circumference is wound along the equator plane CL of the tire, and subsequently, as shown in FIG. 2C, 80% or more of the crown outer circumference length L of the carcass 1 is 100% or more. After winding along the equator plane CL of the tire for a circumference of less than 1%, the remaining circumference of the circumference, that is, a circumference of 20% or less of the circumference is inward from the outside in the width direction of the belt. In the meantime, the third circumference is formed by wrapping with a shift amount within the strip width SW. In the illustrated example, after winding along the equator plane CL of the tire with respect to the circumferential length L of 90% of the crown portion outer circumferential length L of the carcass 1, the remaining 10% of the circumferential length of the belt is Winding is performed while shifting from the inner side to the outer side in the width direction by the amount of movement of the width SW of the strip S.
Finally, as shown in FIG. 2 (d), the fourth circumference is wound along the equator plane CL of the tire and molded.

Thus, by forming the width direction end region 2E ₁ , 2E ₂ over two layers, in the width direction end region, the range of two layers is surely expanded in the radial direction. Stress applied to the rate code can be suppressed. That is, since most of the outer peripheral length L is wound along the equatorial plane CL of the tire, a large part of the outer circumferential length L can be formed in a laminated structure that overlaps in the radial direction, and there is a range in which two layers are reliably provided in the radial direction It expands.

  Here, after winding along the equatorial plane of the tire with respect to a circumferential length of 80% or more and less than 100% of the crown outer circumferential length L of the carcass 1, the remaining circumferential length of one round is within the strip width SW. The reason for shifting by the amount of movement is to enlarge the region wound along the equator plane of the tire as much as possible. Accordingly, it is preferable to shift the width S of the strip S by the amount of movement of the circumferential length of 0.1% of the outer circumferential length of the crown portion of the carcass 1.

  Further, the central region 2C in the width direction of the circumferential belt layers 2a and 2b is spirally wound around a crown portion of the carcass 1 with a plurality of strips of rubberized cloth of a high elastic modulus cord 7 or partially overlapped. It is preferable to form by so-called bandage winding.

Further, for the low elastic modulus cord 6, for example, a metal elastic cord, that is, a double-twisted 4 × 0.28 mm + 6 × 0.25 mm cord, so-called high elongation cord, is suitable. Is a wavy or zigzag shaped cord (see the structure of the circumferential belt layers 2a, 2b in FIGS. 1 (b) and 1 (c)), a so-called corrugated cord, or a metal non-stretch cord, i.e. layer A cord of twist (3 + 9 + 15) × 0.23 mm is suitable. In general, the elastic modulus of a high elongation cord at a tensile strain of 1.8% is smaller than that of a cord having a wave-like or zigzag-type molding, or a non-stretch cord made of metal.
Since it is known as an actual measurement that the tensile strain in the ground plane is about 1.8%, the cord elastic modulus defines the cord elastic modulus at this tensile strain of 1.8%.
Incidentally, the elastic modulus of the cord means that a tensile test is performed on a rubber-covered cord taken out by disassembling a pneumatic tire, and a stress-strain diagram is created from the result, and the strain in the diagram is 1 It is a value obtained by calculating the tangent slope (slope) at .8% and dividing the value by the cross-sectional area of the cord.

  Further, even when an organic fiber cord is used for the high elastic modulus cord 6 and a metal cord is used for the low elastic modulus cord 7, the above elastic modulus condition can be satisfied.

The elastic modulus of the high elastic modulus cord 6 is preferably in the range of 40 GPa or more and 100 GPa or less at a tensile strain of 1.8%. When the elastic modulus is lower than 40 GPa, the diameter growth due to filling with internal pressure may not be suppressed. When the elastic modulus is higher than 100 GPa, the cord breaks due to the input (stress amplitude) applied to the cord when rolling the tire, and the tire internal pressure is maintained. Can be difficult to do.
The elastic modulus of the low elastic modulus cord 7 is preferably in the range of 80 GPa or more and 210 GPa or less at a tensile strain of 1.8%. When the elastic modulus is lower than 80 GPa, the diameter growth due to the internal pressure filling may not be suppressed. When the elastic modulus is higher than 210 GPa, the cord easily breaks due to the input (stress amplitude) applied to the cord during rolling of the tire. Can be difficult to hold.

Construction vehicle tires having the belt structure shown in FIG. 1 (a) were prototyped with a size of 495 / 45R22.5 under the specifications shown in Table 1, and a durability test and a wear test were performed on each prototype tire.
Each of the prototype tires has two inclined belt layers, and the inventive tires 1 and 2 and the comparative example tires 2 to 4 are the width direction end regions 2E ₁ and 2E _{2 in} which the low elastic modulus cords are arranged. Further, a circumferential belt layer is provided from the center region 2C in the width direction in which the high elastic modulus cord is arranged, and the conventional tire and the comparative example tire 1 have a circumferential belt layer in which the high elastic modulus cord is arranged over the entire width.

  These prototype tires were assembled in a rim of size 17.00 × 22.5, the internal pressure was adjusted to 900 kPa, and the drum traveled at a distance of 30000 km under the conditions of load: 5800 kg and drum rotation speed: 60.0 km / h. After that, the tire was dissected and the fatigue strength of the cord in the circumferential belt layer was measured to evaluate the durability performance. The fatigue strength is expressed as an index with the strength of the conventional tire as new being 100, and the larger the value, the greater the fatigue strength, that is, the better the durability performance.

  At the same time, the amount of tread wear was measured and the remaining amount of tread was calculated (wear test). The tread remaining amount is represented by the reciprocal of an index with the tread remaining amount of the conventional tire as 100, and the larger the value, the smaller the wear amount, that is, the better the wear resistance performance.

The elastic modulus of the cord is the elastic modulus of the cord at a tensile strain of 1.8% when the cord is subjected to a tensile test using an Instron type tensile tester.
For the inclined belt layer, (1 + 6) × 0.32 mm layer-twisted cord was applied at a number of driven 24.5 pieces / 50 mm.
In the width direction end areas 2E ₁ and 2E ₂ of the circumferential belt layer, 4 × (1 × 0.28 mm + 6 × 0.25 mm) highly extensible cords are driven and a corrugated cord is applied at 20/50 mm. A wavy non-extended cord of (3 + 9 + 15) × 0.23 mm was applied to the central region 2C in the width direction at a driving number of 22.5 / 50 mm.

  From Table 1, it can be seen that the inventive tires 1 and 2 have improved durability and wear resistance because the laminated structure in the widthwise end region of the circumferential belt layer is appropriate.

(A) is sectional drawing of the width direction of the tire according to this invention, (b), (c) is a development view of a belt. It is a figure which shows the formation procedure of the width direction edge part area | region of a circumferential direction belt layer.

Explanation of symbols

1 carcass 2a, 2b circumferential belt layer 2C widthwise central region 2E _1, 2E ₁ widthwise end regions 3a, 3b slant belt layer 4 belt 5 a tread 6,7 code S strips CL tire equator

Claims (6)

At least one circumferential direction in which a carcass straddling a toroidal shape between a pair of bead portions is used as a skeleton, and a large number of cords extending along the equatorial plane of the tire are covered with rubber on the radially outer side of the crown portion of the carcass A belt in which a belt layer and at least two inclined belt layers in which a large number of cords extending in a direction inclined with respect to the equatorial plane of the tire are covered with rubber are arranged in order, on the radially outer side of the belt A tire with a tread,
The width of the circumferential belt layer is 60% or more of the total width of the tire;
The width of at least one inclined belt layer is wider than the width of the circumferential belt layer;
When each circumferential belt layer is partitioned into a width direction center region and a width direction end region located outside the width direction center region, the elastic modulus of the cord disposed in the width direction end region is Lower than the elastic modulus of the cord arranged in the center area in the width direction,
The circumferential belt layer has at least a two-layer structure in the width direction end area, and the width direction end area is made of rubber with one or more cords from the inner end adjacent to the width direction central area. After winding the coated strip along the equatorial plane of the tire for a circumference of 80% or more and less than 100% of the circumference of the crown of the carcass, the width of the belt with respect to the remaining circumference of one circumference Winding from the inner side to the outer side while shifting by an amount of movement within the strip width, the first circumference is formed, and then the second circumference is wound along the equator plane of the tire. After winding along the equatorial plane of the tire for a circumference of ~ 90%, within the strip width from the outside in the width direction of the belt to the inside for the remaining 10-20% of the circumference Winding while shifting by the amount of movement A pneumatic tire is formed by forming a third circumference and then winding the fourth circumference along the equator plane of the tire.   2. The pneumatic tire according to claim 1, wherein the moving amount of the first and third round strips is a strip width.   The pneumatic tire according to claim 1 or 2, wherein a width of the inclined belt layer is 65% or more of a total width of the tire.   The low elastic modulus cord is an extensible metal cord having an initial elongation, and the high elastic modulus cord is a non-extensible metal cord molded in a linear shape, a wave shape, or a zigzag shape. The pneumatic tire according to claim 1, 2, or 3.   The pneumatic tire according to any one of claims 1 to 4, wherein the low elastic modulus cord is an organic fiber cord, and the high elastic modulus cord is a metal cord.   The elastic modulus at a tensile strain of 1.8% of the low elastic modulus cord and the high elastic modulus cord is in a range of 40 GPa to 100 GPa and 80 GPa to 210 GPa, respectively. The pneumatic tire according to any one of the above.

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