JP2016182925A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire excellent in steering stability and durability.SOLUTION: A carcass ply 44 of a tire 12 comprises a main part 52, a wound-up part 54 and a folded part 56. The main part 52 is hung across a pair of beads 18. The wound-up part 54 is formed by folding the carcass ply 44 around the beads 18 from inside to outside in a shaft direction thereof. The wound-up part 54 extends outward in a radial direction. The folded part 56 is formed by being folded inward in the radial direction from an outer end 54a in the radial direction of the wound-up part 54. The folded part 56 extends inward in the radial direction. A ratio (H1/H) of a height H1 of the outer end in the radial direction of the wound-up part to a height H of the tire is equal to 0.5 or more and 0.9 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  FIG. 3 shows a conventional pneumatic tire 2. The tire 2 includes a reinforcing layer 10 that extends between the bead 4 and the winding portion 8 of the carcass ply 6. The reinforcing layer 10 is composed of a steel cord as a reinforcing cord and a topping rubber. This reinforcing layer 10 improves the rigidity of the tire 2. This reinforcing layer 10 contributes to the improvement of the lateral rigidity of the tire 2. This reinforcing layer 10 contributes to the improvement of the steering stability of the tire 2.

  Japanese Patent Application Laid-Open No. 2012-179944 discloses a tire including an organic fiber reinforcing layer and a metal reinforcing layer. The organic fiber reinforcing layer is made of an organic fiber cord as a reinforcing cord and a topping rubber. The metal reinforcing layer is made of a metal cord as a reinforcing cord and a topping rubber. The organic fiber reinforcing layer and the metal reinforcing layer extend along the sidewall. The organic fiber reinforcing layer and the metal reinforcing layer contribute to the improvement of steering stability of the tire, like the reinforcing layer 10 of the tire 2.

JP 2012-179944 A

  The reinforcing layer 6 having the reinforcing cord tends to cause peeling. The tire 2 tends to be inferior in durability. Similarly, the tire disclosed in Japanese Patent Application Laid-Open No. 2012-179944 also includes a reinforcing layer having a reinforcing cord and is likely to be inferior in durability.

  An object of the present invention is to provide a tire having excellent steering stability and excellent durability.

  The pneumatic tire according to the present invention includes a tread, a pair of sidewalls, a pair of beads, and a carcass. The tread forms a tread surface that contacts the road surface. Each sidewall extends radially inward from the end of the tread. Each bead is located radially inside the sidewall. The carcass is stretched between one bead and the other bead along the inside of the tread and the sidewall. The carcass includes a carcass ply. The carcass ply is composed of a cord and a topping rubber. The carcass ply includes a main portion, a winding portion, and a turn-up portion. This main part is spanned between a pair of beads. The winding portion is formed by folding the carcass ply around the bead from the inner side to the outer side in the axial direction. The winding portion extends outward in the radial direction. The folded portion is formed by being folded radially inward from the radially outer end of the winding portion. The folded portion extends inward in the radial direction. The ratio (H1 / H) of the height H1 of the outer end in the radial direction of the wind-up portion to the tire height H is 0.5 or more and 0.9 or less.

  Preferably, the bead includes a core and an apex extending radially outward from the core. The radially inner end of the folded portion is located radially inward from the radially outer end of the apex.

  Preferably, the tire includes a rubber reinforcing layer made of a crosslinked rubber. This rubber reinforcing layer is laminated between the wound-up portion and the folded portion. The rubber reinforcing layer extends along the folded portion from the radially outer end to the inner end of the folded portion.

  Preferably, the radially inner end of the rubber reinforcing layer is located at the same position in the radial direction as the radially inner end of the folded portion. Alternatively, the radially inner end of the rubber reinforcing layer is positioned more inside than the radially inner end of the folded portion. The length L from the radially inner end of the folded portion to the radially inner end of the reinforcing layer is 0 or more and 10 mm or less.

  Preferably, the tire includes an inner liner that forms an inner surface thereof. The thickness of the rubber reinforcing layer is denoted by Tr, and the thickness from the inner surface of the inner liner to the outer surface of the sidewall at a radial position where the thickness Tr is measured is denoted by Ts. At this time, the ratio of the thickness Tr to the thickness Ts (Tr / Ts) exceeds 0 and is 0.4 or less.

  In this tire, the carcass has a folded portion. This folded portion contributes to improvement of the rigidity of the sidewall. This tire is excellent in handling stability. This folded portion is a part of the carcass ply and is unlikely to be a starting point of peeling. In this tire, a decrease in durability is suppressed as compared with a tire including a conventional reinforcing layer.

FIG. 1 is a cross-sectional view illustrating a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a pneumatic tire according to another embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a conventional pneumatic tire.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view showing a tire 12 according to an embodiment of the present invention. In FIG. 1, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The alternate long and short dash line CL represents the equator plane. A straight line BL represents a bead base line. The bead base line is a straight line extending in the axial direction of the tire 12 through a bead diameter position defined by a standard on which the tire 12 is based.

  The tire 12 includes a tread 14, a sidewall 16, a bead 18, a carcass 20, a belt 22, a band 24, an inner liner 26, a chafer 28, and a reinforcing layer 30 as a rubber reinforcing layer. The tire 12 is a tubeless type pneumatic tire. The tire 12 is attached to a four-wheeled vehicle.

  The tread 14 has a shape protruding outward in the radial direction. The tread 14 forms a tread surface 32 that contacts the road surface. The tread 14 includes a base layer 34 positioned on the inner side and a cap layer 36 positioned on the outer side of the base layer 34 in the radial direction. The cap layer 36 forms the tread surface 32. A groove 38 is formed in the tread surface 32. A tread pattern is formed on the tread surface 32 by the groove 38.

  The base layer 34 and the cap layer 36 are each made of a crosslinked rubber. The crosslinked rubbers of the base layer 34 and the cap layer 36 are different from each other. The base layer 34 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 34 is natural rubber. The cap layer 36 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  The sidewall 16 extends substantially inward in the radial direction from the end of the tread 14. The sidewall 16 is made of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 16 absorbs an impact from the road surface by bending. Further, the sidewall 16 prevents the carcass 20 from being damaged.

  The bead 18 extends from the sidewall 16 substantially inward in the radial direction. The bead 18 includes a core 40 and an apex 42 that extends radially outward from the core 40. The apex 42 is tapered outward in the radial direction. The apex 42 is made of a highly hard crosslinked rubber. The core 40 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel.

  The carcass 20 extends along the inner surfaces of the tread 14 and the sidewall 16. The carcass 20 is bridged between one bead 18 in the axial direction and the other bead 18. The carcass 20 includes a carcass ply 44. Although not shown, the carcass ply 44 is made of a cord and a topping rubber. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 22 is located between the carcass 20 and the tread 14. The belt 22 includes an inner layer 46 and an outer layer 48. An outer layer 48 is laminated on the outer side in the radial direction of the inner layer 46. Although not shown, the inner layer 46 and the outer layer 48 are made of a cord and a topping rubber. The material of this cord is steel or organic fiber. Specific examples of the organic fiber include aramid fiber, nylon fiber, polyester fiber, rayon fiber, and polyethylene naphthalate fiber. The axial width of the belt 22 is preferably not less than 0.7 times the maximum width of the tire 12.

  The band 24 is located outside the belt 22 in the radial direction. The width of the band 24 is larger than the width of the belt 22. The band 24 extends from one end 24a in the axial direction to the other end 24a (not shown). This band 24 is a so-called full band. The band 24 is laminated on the outer side in the radial direction of the belt 22 on the equator plane.

  Although not shown, the band 24 is composed of a cord and a topping rubber. The cord is wound in a spiral. The band 24 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less, further 2 ° or less. Since the belt 22 is restrained by this cord, lifting of the belt 22 is suppressed. The cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. In the tire 12, the belt 22 and the band 24 constitute a reinforcing layer.

  The inner liner 26 is joined to the inner peripheral surface of the carcass 20. The inner liner 26 is made of a crosslinked rubber. The inner liner 26 is made of rubber having excellent air shielding properties. The inner liner 26 forms the inner surface 50 of the tire 2. The inner surface 50 is the inner surface of the tire 12. When the tire 12 is incorporated into the rim and filled with air, the inner liner 26 maintains the internal pressure.

  The chafer 28 is located in the vicinity of the bead 18. When the tire 12 is incorporated into the rim, the chafer 28 contacts the rim. By this contact, the vicinity of the bead 18 is protected.

  In the tire 2, the carcass ply 44 includes a main portion 52, a pair of winding portions 54, and a pair of folded portions 56. The main portion 52 is bridged between the pair of beads 18. The carcass ply 44 is folded around the core 40 from the axial inner side to the outer side. By this folding, a winding portion 54 that extends continuously from the end of the main portion 52 is formed. The winding portion 54 extends outward in the radial direction along the core 40 and the apec 42. The winding portion 54 is folded back from the inner side in the axial direction to the outer side at the radially outer end. By this folding, a folded portion 56 extending continuously from the outer end of the winding portion 54 is formed. The folded portion 56 extends radially inward from the outer end of the winding portion 54. The folded portion 56 extends along the winding portion 54.

  The reinforcing layer 30 is laminated between the winding part 54 and the folded part 56 in the axial direction. The carcass ply 44 is folded back at the radially outer end 30 a of the reinforcing layer 30 to form an outer end 54 a and a folded portion 56 of the winding portion 54. The outer end 54 a is also the outer end of the folded portion 56. The reinforcing layer 30 is made of a crosslinked rubber. The reinforcing layer 30 does not include a reinforcing cord such as a metal cord or an organic fiber cord.

The tire 12 having a large complex elastic modulus Er ^* of the crosslinked rubber of the reinforcing layer 30 is excellent in rigidity. On the other hand, if the complex elastic modulus Er ^* is too large, the durability of the tire 12 is lowered. This complex elastic modulus Er ^* is made larger than the complex elastic modulus Es ^* of the crosslinked rubber of the sidewall 16. The complex elastic modulus Es ^* of the sidewall 16 is set to 4 MPa or more and 7 MPa or less, for example. This complex elastic modulus Er ^* is made smaller than the complex elastic modulus Ee ^* of the crosslinked rubber of the apex 42. The complex elastic modulus Ee ^* of the apex 42 is, for example, not less than 20 MPa and not more than 60 MPa.

  A double arrow H in FIG. 1 represents the height of the tire 12. This height H is measured as the distance from the bead base line to the tread surface 32 in the equator plane. A double-headed arrow H1 represents the height of the radially outer end 54a of the winding portion 54. This height H1 is measured as a distance from the bead base line to the outer end 54a. The height H and the height H1 are measured as a linear distance in the radial direction.

  A double arrow L in FIG. 1 represents the distance from the radially inner end 56 a of the folded portion 56 to the radially inner end 30 b of the reinforcing layer 30. This distance L represents the length of the reinforcing layer 30 from the position of the inner end 56a to the inner end 30b. This length L is measured along the reinforcing layer 30.

  A double arrow Tr in FIG. 1 represents the thickness of the reinforcing layer 30. A double arrow Ts represents the thickness of the sidewall portion 58. This thickness Ts is the thickness of the tire 12 from the inner surface 50 to the outer surface 60 of the tire 12. The thickness Ts includes the thickness of the sidewall 16, the carcass 20, the reinforcing layer 30, and the inner liner 26. This thickness Ts may further include the thickness of the apex 42. The thickness Ts is measured at a position where the thickness Tr is measured. The thickness Ts is measured in the direction in which the thickness Tr of the reinforcing layer 30 is measured.

  In the tire 12, the folded portion 56 is formed by being folded at the outer end 54 a of the winding portion 54. The folded portion 56 extends radially inward from the outer end 54a. The folded portion 56 is laminated on the outside of the winding portion 54 in the axial direction. The folded portion 56 contributes to improving the rigidity of the sidewall portion 58. In the tire 12, the steering stability is improved.

  The folded portion 58 is a part of the carcass ply 44. The folded portion 58 is formed integrally with the main portion 54 and the winding portion 56. The folded portion 58 is unlikely to be damaged such as peeling. The tire 12 is suppressed in durability while improving the rigidity of the sidewall portion 58.

  By increasing the height H1 of the outer end 54a of the winding portion 54, the rigidity of the sidewall portion 58 can be improved. From the viewpoint of improving the rigidity, the ratio of the height of the outer end 54a to the height H of the tire 12 (H1 / H) is preferably 0.5 or more, and more preferably 0.6 or more. On the other hand, a decrease in the durability of the tire 12 can be suppressed by reducing the height H1. From this viewpoint of durability, the ratio (H1 / H) is preferably 0.9 or less, and more preferably 0.8 or less.

  The folded portion 56 extends radially inward from the radially outer end 42 a of the apex 42. The inner end 56a is located on the radially inner side of the outer end 42a. The apex 42 and the folded portion 56 overlap each other when viewed in the axial direction. Due to this overlap, it is possible to prevent the rigidity from changing greatly inside the inner end 56a. This overlap contributes to the improvement of the rigidity of the sidewall portion 58 and the improvement of the durability.

  In the tire 12, the reinforcing layer 30 is laminated between the winding part 54 and the folded part 56. The reinforcing layer 30 extends along the folded portion from the outer end of the folded portion 56 to the lower end 54a. This reinforcing layer 30 contributes to the improvement of the rigidity of the sidewall portion 58. This reinforcing layer 30 contributes to improvement in steering stability.

  The carcass ply 44 is folded back at the outer end 30 a of the reinforcing layer 30. It is relieved that the bending radius of the folding of the carcass ply 44 is reduced by folding the reinforcing layer 30 therebetween. The folding of the carcass ply 44 is suppressed from being the starting point of damage to the carcass ply 44. The reinforcing layer 30 contributes to improving the durability of the tire 12.

  From the viewpoint of suppressing an increase in the rigidity difference at the sidewall portion 58, it is preferable that the apex 42 and the reinforcing layer 30 overlap each other when viewed in the axial direction. It is preferable that the inner end 30 b of the reinforcing layer 30 is positioned radially inward from the inner end 56 a of the folded portion 56. By configuring in this way, an increase in the radial rigidity difference at the sidewall portion 58 is suppressed. From the viewpoint of suppressing an increase in the rigidity difference, the inner end 30b is preferably set at the same position in the radial direction as the inner end 56a. More preferably, as shown in FIG. 1, the inner end 30b is positioned radially inward from the inner end 56a.

  From this viewpoint, the length L of the reinforcing layer 30 from the inner end 56a of the folded portion 56 to the inner end 30b of the reinforcing layer 30 is preferably 0 or more, more preferably 2 mm or more, and particularly preferably 4 mm. That's it. On the other hand, the mass of the tire 12 is increased by increasing the length L. An increase in mass increases heat storage. Increasing mass reduces durability and increases rolling resistance. From this viewpoint, the length L is preferably 10 mm or less, more preferably 8 mm or less, and particularly preferably 6 mm or less.

  The rigidity of the sidewall portion 58 can be improved by increasing the thickness of the reinforcing layer 30. From this viewpoint, the ratio of the thickness Tr to the thickness Ts (Tr / Ts) is preferably more than 0, more preferably 0.1 or more, and particularly preferably 0.2 or more. On the other hand, heat storage is suppressed by making this thickness Tr thin. The durability can be improved by reducing the thickness Tr. From this viewpoint, the ratio (Tr / Ts) is preferably 0.4 or less, and more preferably 0.3 or less.

  FIG. 2 shows a pneumatic tire 62 according to another embodiment of the present invention. The tire 62 has the same configuration as that of the tire 12 except that the reinforcing layer 30 is not provided. The folded portion 56 of the carcass ply 44 is stacked on the winding portion 54. Other configurations are the same as those of the tire 12, and the description thereof is omitted. In FIG. 2, the same components as those of the tire 12 are denoted by the same reference numerals.

  In the present invention, the rigidity of the sidewall portion 58 is improved by providing the folded portion 56. The folded portion 58 is a part of the carcass ply 44. The folded portion 58 is formed integrally with the main portion 54 and the winding portion 56. The folded portion 58 is joined to a winding portion 56 made of the same material in the axial direction. The folded portion 58 is unlikely to be damaged such as peeling. The tire 62 is excellent in durability.

In the present invention, the complex elastic modulus Er ^* , the complex elastic modulus Es ^*, and the complex elastic modulus Ee ^* are measured according to the following measurement conditions in accordance with the provisions of “JIS K 6394” (made by Iwamoto Seisakusho). Product name “VESF-3”). In this measurement, a plate-shaped test piece (length = 45 mm, width = 4 mm, thickness = 2 mm) is formed from the rubber composition to be measured. This test piece is used for measurement.
Initial strain: 10%
Amplitude: ± 2.0%
Frequency: 10Hz
Deformation mode: Tensile
Measurement temperature: 70 ° C

  In the present invention, unless otherwise specified, the dimensions and angles of the respective members of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Test 1]
[Example 1]
A tire having the structure shown in FIG. 1 was obtained. The tire size was “265 / 35R18”. The ratio (H1 / H) of the height H1 of the outer end of the folded portion to the height H of the tire and the thickness Tr of the reinforcing layer are as shown in Table 1. This thickness Tr was measured at the position where the thickness Ts of the sidewall portion was the smallest in the range where the reinforcing layer was located. In this tire, the thickness Tr was measured in the vicinity of the position where the main portion of the carcass ply is at the outermost side in the axial direction.

[Comparative Example 1]
A tire having the structure shown in FIG. 3 was obtained. The carcass ply of this tire does not have a folded portion. This tire was provided with a reinforcing layer made of a steel cord and a topping rubber between the bead and the carcass winding portion in the axial direction.

[Comparative Example 2]
A tire was obtained in the same manner as in Comparative Example 1 except that the cord of the reinforcing layer was an organic fiber cord.

[Example 2]
A tire was obtained in the same manner as in Example 1 except that the thickness Tr of the reinforcing layer was changed as shown in Table 1.

[Example 3]
A tire having the structure shown in FIG. 2 was obtained. This tire was the same as Example 1 except that no reinforcing layer was provided.

[Example 4-7]
A tire was obtained in the same manner as in Example 3 except that the ratio (H1 / H) was set as shown in Table 2.

[Steering stability]
A tire was incorporated into a regular rim, and air was filled into the tire so as to achieve a regular internal pressure. This tire was mounted on a passenger car. The driver was allowed to drive this passenger car to evaluate the handling stability. This evaluation is a sensory evaluation of the driver. The results are shown in Tables 1 and 2 below as an index with the tire of Comparative Example 1 as 100. The evaluation result is preferably as the numerical value is larger.

[durability]
A tire was incorporated into a regular rim, and the tire was filled with air to adjust the internal pressure to 120 kPa. This tire was mounted on a drum-type running test machine, and a vertical load of 7.0 kN was applied to the tire. This tire was run on the drum at a speed of 200 km / h. The distance traveled until the tire broke was measured. The results are shown in Tables 1 and 2 below as an index with the tire of Comparative Example 1 as 100. The evaluation result is preferably as the numerical value is larger.

[Test 2]
[Example 8-10]
A tire having the structure shown in FIG. 1 was obtained. The tire size was “265 / 35R18”. The length L of the reinforcing layer from the inner end of the folded portion to the inner end of the reinforcing layer was 10 mm. The ratio of the thickness Ts from the inner surface of the inner liner to the outer surface of the sidewall and the thickness Tr of the reinforcing layer (Tr / Ts) was set as shown in Table 3 to obtain a tire. The thickness Tr and the thickness Ts were measured at the position where the thickness Ts of the sidewall portion was the thinnest in the range where the reinforcing layer was located, as in Test 1.

[Example 11-13]
A tire was obtained in the same manner as in Example 8, except that the length L of the reinforcing layer from the inner end of the folded portion to the inner end of the reinforcing layer was as shown in Table 3.

[Maneuvering stability and durability]
In the same manner as in Test 1, steering stability and durability were evaluated. The results are shown in Table 3 below as an index with the tire of Comparative Example 1 of Test 1 as 100. The evaluation result is preferably as the numerical value is larger.

  As shown in Tables 1 to 3, the tires of the examples are superior in handling stability and durability compared to the tires of the comparative examples. From this evaluation result, the superiority of the present invention is clear.

  The tire according to the present invention can be mounted on various vehicles such as a four-wheeled vehicle and a two-wheeled vehicle.

DESCRIPTION OF SYMBOLS 12, 62 ... Tire 14 ... Tread 16 ... Side wall 18 ... Bead 20 ... Carcass 30 ... Reinforcement layer 40 ... Core 42 ... Apex 44 ... Carcass Ply 50 ... Inner surface 52 ... Main part 54 ... Winding part 56 ... Folding part 58 ... Side wall part 60 ... Outer surface

Claims (5)

It has a tread, a pair of sidewalls, a pair of beads and a carcass,
The tread forms a tread surface that contacts the road surface,
Each sidewall extends radially inward from the end of the tread,
Each bead is located radially inside the sidewall,
The carcass is stretched between one bead and the other bead along the inside of the tread and the sidewall,
The carcass includes a carcass ply, and the carcass ply includes a cord and a topping rubber.
This carcass ply has a main part, a winding part, and a folded part,
This main part is spanned between a pair of beads,
This winding part is formed by folding the carcass ply around the bead from the inner side to the outer side in the axial direction, and this winding part extends radially outward.
The folded portion is formed by being folded radially inward from the radially outer end of the winding portion, and the folded portion extends radially inward.
A pneumatic tire in which a ratio (H1 / H) of a height H1 of a radially outer end of a rolled-up portion to a tire height H is 0.5 or more and 0.9 or less. The bead includes a core and an apex extending radially outward from the core;
2. The tire according to claim 1, wherein an inner end in the radial direction of the folded portion is located radially inward from an outer end in the radial direction of the apex. It has a rubber reinforcing layer made of crosslinked rubber,
This rubber reinforcement layer is laminated between the winding part and the folded part,
The tire according to claim 1 or 2, wherein the rubber reinforcing layer extends along the folded portion from the outer end to the inner end of the folded portion. The radially inner end of the rubber reinforcing layer is located at the same position in the radial direction as the radially inner end of the folded portion or inside the radially inner end of the folded portion,
The tire according to claim 3, wherein a length L from the radially inner end of the folded portion to the radially inner end of the reinforcing layer is 0 or more and 10 mm or less. It has an inner liner that forms the inner surface,
When the thickness of the rubber reinforcing layer is Tr, and the thickness from the inner surface of the inner liner to the outer surface of the sidewall is Ts at a radial position where the thickness Tr is measured,
The tire according to claim 3 or 4, wherein a ratio of the thickness Tr to the thickness Ts (Tr / Ts) exceeds 0 and is 0.4 or less.

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