JP6728892B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire.

In a general tire, if the pressure at the time of contact with the ground is high, it causes uneven wear, so it is necessary to moderate the contact pressure appropriately.

Conventionally, for example, Patent Document 1 describes a pneumatic tire for the purpose of improving the steering stability on snow after the occurrence of wear due to running without impairing the dry steering stability. This pneumatic tire has, on the tread surface of the tread portion, a block divided by a plurality of main grooves extending in the circumferential direction and lateral grooves intersecting with the main groove, and the block has a sipe, and the block is A pair of small blocks having a pair of acute-angled block corners facing each other in the circumferential direction and defined by the pair of acute-angled block corners and two sipes, and sandwiched between these small blocks, And a central block larger than the small blocks.

JP, 2003-182315, A

By inserting fine grooves or slits such as sipes, the rigidity of blocks and ribs is weakened, and burns and chips may occur.

The present invention has been made in view of the above, and is a pneumatic tire capable of improving uneven wear resistance while maintaining durability by relaxing the ground contact pressure while maintaining block rigidity. The purpose is to provide.

In order to solve the above-mentioned problems and to achieve the object, a pneumatic tire according to an aspect of the present invention has two tires extending along the tire circumferential direction on the tread surface of a tread portion and arranged in the tire width direction. Direction grooves and a plurality of tires extending side by side in the tire circumferential direction on the tread surface and arranged side by side in the tire circumferential direction so that both ends communicate with each of the circumferential grooves and block between the circumferential grooves. -Shaped widthwise section that defines a land portion, and two tread surfaces of the land portion that extend along the tire circumferential direction and are provided side by side in the tire widthwise direction so that both ends communicate with each widthwise groove. And a narrow groove that divides the land portion defined by each of the circumferential grooves and each of the widthwise grooves into a plurality of small land portions in the tire width direction, and two of the land portions are provided. The narrow groove is formed such that the groove width is smaller than the circumferential groove, and a bent portion is formed in the middle, and the bent portion is arranged on the inner side in the tire width direction which is opposed to each other with respect to a virtual straight line connecting both ends. Further, the bending points of the bending portions are arranged so as to be displaced from each other in the tire circumferential direction.

According to this pneumatic tire, each land portion defined by the circumferential groove and the widthwise groove is divided into a plurality of small land portions by the two narrow grooves, thereby reducing the rigidity. As a result, the ground pressure at the time of grounding the tread portion is relieved. Furthermore, each thin groove is formed to have a bent portion and is bent to extend the length thereof, so that the ground pressure is further relieved by further lowering the rigidity. Therefore, the uneven wear resistance performance can be improved. Moreover, according to this pneumatic tire, by disposing the bent portion on the inner side in the tire width direction where the two narrow grooves are opposed to each other than the virtual straight line connecting both ends of the narrow groove, the lateral small land portion can be obtained. The decrease in the area of the tread surface is suppressed, and the decrease in rigidity is prevented. Further, by disposing the bending points of the two narrow grooves so as to be displaced from each other in the tire circumferential direction, it is possible to prevent the central small land portion from being locally thin, and prevent the rigidity from decreasing. Therefore, it is possible to suppress the occurrence of baldness and chipping in the land portion. As a result, according to this pneumatic tire, uneven wear resistance can be improved while suppressing occurrence of burr and chipping and maintaining durability.

In the pneumatic tire according to an aspect of the present invention, it is preferable that the narrow groove has a bending angle of the bending portion in a range of 90° or more and 160° or less.

According to this pneumatic tire, when the bending angle of the bent portion is 90° or more, the bending becomes an acute angle or more, so that the blush/chip is less likely to occur, and the durability is largely maintained. On the other hand, when the bending angle of the bent portion is 160° or less, the effect of extending the length of the narrow groove to reduce the rigidity is great.

Further, in the pneumatic tire according to one aspect of the present invention, a deviation width Lc in the tire circumferential direction between the bending points of the two narrow grooves is equal to a tire circumference of the land portion in which the narrow grooves are formed. It is preferable that 0.1≦Lc/L with respect to the directional dimension L.

According to this pneumatic tire, by setting 0.1≦Lc/L, it is possible to further suppress local thinning of the central small land portion between the two narrow grooves, and further prevent lowering of rigidity. It has a large effect of maintaining durability performance.

Further, in the pneumatic tire according to one aspect of the present invention, the widthwise grooves are formed so as to extend obliquely with respect to the tire widthwise direction, and the angle with respect to the tire widthwise direction is 5° or more and 50° or less. It is preferably in the range of.

According to this pneumatic tire, when the angle of the widthwise groove is 5° or more, the effect of extending the length of the widthwise groove to reduce the rigidity is great. When the angle of the widthwise groove is 50° or less, sharpening of the angle is suppressed, so that it is less likely to cause burr and chip, and the effect of maintaining durability is large.

In the pneumatic tire according to an aspect of the present invention, when the groove depth of the circumferential groove is Ha, the groove depth of the widthwise groove is Hb, and the groove depth of the narrow groove is Hc, Ha is It is preferable that the relationships of >Hb and Ha>Hc are satisfied.

According to this pneumatic tire, the rigidity in the tire circumferential direction of the land portion is reduced by making the groove depth Hb of the widthwise groove and the groove depth Hc of the narrow groove smaller than the groove depth Ha of the circumferential groove. Therefore, the effect of maintaining durability is great.

Further, in the pneumatic tire according to one aspect of the present invention, when the groove depth of the widthwise groove is Hb and the groove depth of the narrow groove is Hc, Hb is 1 mm or more and 5 mm or less, and Hc is 1 mm. It is preferably 5 mm or less.

According to this pneumatic tire, since the groove depth Hb of the widthwise groove and the groove depth Hc of the narrow groove are set to 1 mm or more and 5 mm or less, the rigidity reduction of the land portion is suppressed, and thus the durability is maintained. Great effect.

Further, in the pneumatic tire according to one aspect of the present invention, the widthwise groove is formed to extend so as to be inclined with respect to the tire width direction, and the land portion that forms an acute angle with respect to the tire circumferential direction. It is preferable that chamfers are formed at the corners of.

According to this pneumatic tire, by providing the chamfer, it is difficult to cause burr and chip, and the effect of maintaining durability is great.

In the pneumatic tire according to one aspect of the present invention, the tread surface further includes a sipe formed so that one end communicates with the circumferential groove and the other end terminates in the land portion, and the groove width of the sipe. Is Wd, the groove depth is Hd, the groove length is Ld, the tire width direction dimension of the land portion is We, and the groove depth of the circumferential groove is Ha. 0.3 mm≦Wd≦2. It is preferable that the relations of 0 mm, 0.3≦Hd/Ha≦1.0, and 0.03≦Ld/We≦0.2 are satisfied.

According to this pneumatic tire, since the rigidity of the land portion is reduced by the sipes and the ground contact pressure is relieved, the effect of improving the uneven wear resistance is great.

According to the present invention, it is possible to improve the uneven wear resistance performance while maintaining the durability performance.

FIG. 1 is a plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged view of the tread portion of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is an enlarged view of a tread portion of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is an enlarged view of a tread portion of another example of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is an enlarged cross-sectional view of the tread portion of the pneumatic tire according to the embodiment of the present invention. FIG. 6 is an enlarged cross-sectional view of the tread portion of the pneumatic tire according to the embodiment of the present invention. FIG. 7 is a chart showing the results of performance tests of pneumatic tires according to the examples of the present invention. FIG. 8 is a table showing the results of performance tests of pneumatic tires according to the examples of the present invention.

Embodiments of the present invention will be described below in detail with reference to the drawings. The present invention is not limited to this embodiment. Further, the constituent elements of this embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, a plurality of modified examples described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

FIG. 1 is a plan view of a tread portion of a pneumatic tire according to this embodiment. FIG. 2 is an enlarged view of the tread portion of the pneumatic tire according to this embodiment. FIG. 3 is an enlarged view of a tread portion of another example of the pneumatic tire according to this embodiment. FIG. 4 is an enlarged view of a tread portion of another example of the pneumatic tire according to this embodiment. FIG. 5 is an enlarged cross-sectional view of the tread portion of the pneumatic tire according to this embodiment. FIG. 6 is an enlarged cross-sectional view of the tread portion of the pneumatic tire according to this embodiment.

In the following description, the tire circumferential direction means a circumferential direction with a rotation axis (not shown) of the pneumatic tire 1 as a central axis. Further, the tire width direction means a direction parallel to the rotation axis, the tire width direction inner side is a side facing the tire equatorial plane (not shown) in the tire width direction, and the tire width direction outer side is in the tire width direction. The side away from the equatorial plane of the tire. The tire radial direction refers to a direction orthogonal to the rotation axis, the tire radial inside refers to the side facing the rotation axis in the tire radial direction, and the tire radial outside refers to the side away from the rotation axis in the tire radial direction. The tire equatorial plane is a plane that is orthogonal to the rotation axis and that passes through the center of the tire width of the pneumatic tire 1.

The pneumatic tire 1 of the present embodiment has a tread portion 2 as shown in FIG. The tread portion 2 is made of a rubber material and is exposed at the outermost side of the pneumatic tire 1 in the tire radial direction, and the surface thereof serves as the tread surface 2A and serves as the contour of the pneumatic tire 1.

The tread portion 2 is provided with a plurality of circumferential grooves 3 extending in the tire circumferential direction on the tread surface 2A (a total of seven circumferential grooves are shown in FIG. 1 in the present embodiment) in the tire width direction. The circumferential groove 3 has, for example, a groove width of 8 mm or more and 15 mm or less (Wa in FIG. 2 and FIG. 5) and a groove depth of 10 mm or more and 28 mm or less (dimension from the opening position of the tread surface 2A to the groove bottom: FIG. 5 and Ha) in FIG.

Further, in the tread portion 2, ribs extending in the tire circumferential direction are defined by the circumferential grooves 3 adjacent to each other on the tread surface 2A. Further, the tread portion 2 is provided with a plurality of width direction grooves 4 which are arranged in the tire circumferential direction on the tread surface 2A and which intersect the tire circumferential direction and extend in the tire width direction. Both ends of the widthwise groove 4 communicate with the circumferential groove 3. Therefore, each rib defined by the circumferential groove 3 is divided by the widthwise groove 4, and the block-shaped land portion 5 is defined between the circumferential grooves 3. The widthwise groove 4 has, for example, a groove width of 1 mm or more and 4 mm or less (Wb in FIG. 2) and a groove depth of 1 mm or more and 5 mm or less (dimension from the opening position of the tread surface 2A to the groove bottom: Hb in FIG. 6). I mean one.

Further, the tread portion 2 is the tread surface 2A, and in each land portion 5 defined by the circumferential groove 3 and the widthwise groove 4, the narrow groove 6 extending in the tire circumferential direction is arranged in the tire width direction. Two are provided side by side independently without crossing. Both ends of each narrow groove 6 communicate with the widthwise groove 4. Therefore, each land portion 5 defined by the circumferential groove 3 and the widthwise groove 4 is divided into a plurality in the tire width direction by each narrow groove 6, and within one land portion 5, the widthwise groove 4 and each A central land portion 5A defined by the narrow groove 6 and two lateral land portions 5B defined by the circumferential groove 3, the widthwise groove 4 and the thin groove 6 are formed. The narrow groove 6 has, for example, a groove width of 1 mm or more and 4 mm or less (Wc in FIGS. 2 and 5) and a groove depth of 1 mm or more and 5 mm or less (dimension from the opening position of the tread surface 2A to the groove bottom: FIG. 5). Hc).

The two narrow grooves 6 in the land portion 5 are formed so that the groove width Wc is smaller than the groove width Wa of the circumferential groove 3. A bent portion 6A is formed in the middle of each of the narrow grooves 6. The bent portion 6A is arranged on the inner side in the tire width direction of the two narrow grooves 6 that face each other in the tire width direction with respect to the virtual straight line A that connects both ends of the narrow groove 6. Further, these narrow grooves 6 are arranged such that the bending points 6Aa of the bending portions 6A are displaced from each other in the tire circumferential direction.

As shown in FIG. 2, when the bending portion 6A is formed by one bending in one thin groove 6, as shown in FIG. 2, the bending point 6Aa of the thin groove 6 is two thin lines in the tire width direction in the one bending. It is a bending point on the inner side in the tire width direction where the grooves 6 face each other.

Further, as shown in FIG. 3, when the bending portion 6A is formed by a plurality of bends in one thin groove 6, the bending point 6Aa of the narrow groove 6 is 2 in the tire width direction in the plurality of bends. The bending point is the innermost side in the tire width direction where the two narrow grooves 6 face each other (the inner side in the tire width direction where the two narrow grooves 6 face each other with respect to the reference straight line B).

Further, the bending point 6Aa of the narrow groove 6 is, as shown in FIG. 4, a case where the bent portion 6A is formed by a plurality of bends in one narrow groove 6, and in the tire width direction in the plurality of bends. When there are a plurality of innermost bending points in the tire width direction in which the two narrow grooves 6 are opposed to each other, the center point of a reference straight line C connecting the plurality of innermost bending points at both ends in the tire circumferential direction is set. .. Therefore, in this case, the bending point 6Aa includes that it does not coincide with the bending point as shown in FIG.

According to the pneumatic tire 1 of this embodiment having such a configuration, each land portion 5 defined by the circumferential groove 3 and the widthwise groove 4 is divided into the central small land portion 5A by the two narrow grooves 6. By being formed by being divided into two lateral land portions 5B, the contact pressure when the tread portion 2 comes into contact with the ground is relaxed due to low rigidity. Further, each thin groove 6 is formed to have a bent portion 6A and is bent to extend the length thereof, so that the ground pressure is further alleviated by further lowering the rigidity. Therefore, the uneven wear resistance performance can be improved.

Moreover, according to the pneumatic tire 1 of the present embodiment, the bent portion 6A should be arranged on the inner side in the tire width direction where the two narrow grooves 6 face each other than the virtual straight line A connecting the both ends of the narrow groove 6. Thus, the reduction of the area of the lateral land portion 5B on the tread surface 2A is suppressed, and the reduction in rigidity is prevented. Further, by disposing the bending points 6Aa of the two narrow grooves 6 so as to be displaced from each other in the tire circumferential direction, it is possible to prevent the central land portion 5A from being locally thin, and prevent the rigidity from decreasing. Therefore, it is possible to suppress the occurrence of baldness and chipping of the land portion 5.

As a result, according to the pneumatic tire 1 of the present embodiment, uneven wear resistance can be improved while suppressing the occurrence of burr and chipping and maintaining durability.

Further, in the pneumatic tire 1 of the present embodiment, the narrow groove 6 preferably has a bending angle α of the bending portion 6A of 90° or more and 160° or less. As shown in FIGS. 2 to 4, the bending angle α is an angle on the smaller side in bending the bending portion 6A.

According to this pneumatic tire 1, if the bending angle α of the bending portion 6A is 90° or more, the bending becomes an acute angle or more, so that the blush/chip is unlikely to occur and the durability is largely maintained. On the other hand, when the bending angle α of the bent portion 6A is 160° or less, the effect of extending the length of the narrow groove 6 to reduce the rigidity is great.

Further, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 2, the deviation width Lc in the tire circumferential direction between the bending points 6Aa of the two narrow grooves 6 is the land on which the narrow grooves 6 are formed. It is preferable that 0.1≦Lc/L with respect to the tire circumferential dimension L of the portion 5. The maximum value of the deviation width Lc is in the range below the virtual straight line A.

According to this pneumatic tire, by setting 0.1≦Lc/L, the central land portion 5A between the two narrow grooves 6 is further suppressed from being locally thin, and the rigidity is further prevented from decreasing. It is possible to maintain durability performance.

Further, in the pneumatic tire 1 of the present embodiment, the widthwise grooves 4 are formed so as to extend obliquely with respect to the tire width direction, and the angle β with respect to the tire width direction is 5° or more and 50° or less. It is preferably in the range.

According to the pneumatic tire 1, if the angle β of the widthwise groove 4 with respect to the tire widthwise direction is 5° or more, the effect of extending the length of the widthwise groove 4 to reduce the rigidity is great. When the angle β of the widthwise grooves 4 with respect to the tire width direction is 50° or less, sharpening of the angle is suppressed, so that burr and chipping are less likely to occur, and durability is largely maintained.

In the pneumatic tire 1 of the present embodiment, the widthwise grooves 4 are provided in the ribs defined by the adjacent circumferential grooves 3 so as to be inclined in the same direction with respect to the tire widthwise direction. Moreover, in the pneumatic tire 1 of the present embodiment, the widthwise grooves 4 are also provided in the adjacent ribs so as to be inclined in the same direction with respect to the tire width direction. With this configuration, the shape of each land portion 5 is made uniform, which contributes to the improvement of uneven wear resistance.

Further, in the pneumatic tire 1 of the present embodiment, when the groove depth of the circumferential groove 3 is Ha, the groove depth of the widthwise groove 4 is Hb, and the groove depth of the narrow groove 6 is Hc, Ha>Hb , Ha>Hc.

According to this pneumatic tire 1, the groove depth Hb of the widthwise groove 4 and the groove depth Hc of the narrow groove 6 are made smaller than the groove depth Ha of the circumferential groove 3 so that the tire of the land portion 5 is formed. Since the decrease in rigidity in the circumferential direction is suppressed, the effect of maintaining durability is great.

Further, in the pneumatic tire 1 of the present embodiment, when the groove depth of the widthwise groove 4 is Hb and the groove depth of the narrow groove 6 is Hc, Hb is 1 mm or more and 5 mm or less, and Hc is 1 mm or more and 5 mm. The following is preferable.

According to this pneumatic tire 1, since the groove depth Hb of the widthwise groove 4 and the groove depth Hc of the narrow groove 6 are set to 1 mm or more and 5 mm or less, the rigidity of the land portion 5 is suppressed from decreasing. The effect of maintaining sex is great.

Further, in the pneumatic tire 1 of the present embodiment, the widthwise grooves 4 are formed to extend so as to be inclined with respect to the tire width direction, and the corners of the land portion 5 that form an acute angle with respect to the tire circumferential direction. It is preferable that a chamfer 4A is formed on the portion.

According to the pneumatic tire 1, by providing the chamfer 4A, it is difficult for the battering and chipping to occur, and the effect of maintaining durability is large.

Further, in the pneumatic tire 1 of the present embodiment, as shown in FIGS. 2 to 5, one end of the tread surface 2</b>A communicates with the circumferential groove 3 and the other end of the tread surface 2</b>A does not intersect the fine groove 6 and the inside of the land portion 5 is not crossed. It is preferable to further include a sipe 7 formed by terminating at. The sipe 7 has a groove width of Wd, a groove depth of Hd, a groove length of Ld, a tire width direction dimension of the land portion 5 of We, and a groove depth of the circumferential groove 3 of Ha. 3 mm≦Wd≦2.0 mm, 0.3≦Hd/Ha≦1.0, 0.03≦Ld/We≦0.2.

According to the pneumatic tire 1, the sipe 7 reduces the rigidity of the land portion 5 and relieves the ground contact pressure, so that the uneven wear resistance is greatly improved.

In this example, a plurality of types of test tires under different conditions were subjected to performance tests regarding uneven wear resistance and durability (see FIGS. 7 and 8).

In this performance test, a pneumatic tire of tire size 445/50R22.5 (pneumatic tire for heavy load) was mounted on a regular rim, filled with regular internal pressure, and mounted on a trailer shaft of a test vehicle (2-D/D vehicle). I put it on.

Here, the regular rim is a “standard rim” defined by JATMA, a “Design Rim” defined by TRA, or a “Measuring Rim” defined by ETRTO. The normal internal pressure is the maximum value specified in JATMA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "INFLATION PRESSURES" specified in ETRTO.

In the performance test regarding uneven wear resistance performance, the area and depth of uneven wear occurring in the land portion are measured after the test vehicle has traveled 100,000 miles (about 160,000 km). Then, based on this measurement result, index evaluation is performed using the conventional example as a reference (100). The larger the numerical value in this evaluation, the better the uneven wear resistance and the better.

In a performance test relating to durability performance, the number of mottles and chips that have occurred on land is measured after the test vehicle has traveled 100,000 miles (about 160,000 km). Then, based on this measurement result, index evaluation is performed using the conventional example as a reference (100). The larger the value of this evaluation, the smaller the number of baldness and chips, and the better the durability performance, which is preferable.

The pneumatic tire of the conventional example shown in FIG. 7 does not have a narrow groove. The pneumatic tire of each comparative example shown in FIG. 7 has fine grooves, but the form of the fine grooves is different from the definition of this embodiment. On the other hand, in the pneumatic tires of the respective examples shown in FIGS. 7 and 8, the form of the narrow groove is within the specified range.

As shown in the test results of FIGS. 7 and 8, it is understood that the pneumatic tires of Examples 1 to 12 have improved uneven wear resistance while maintaining durability.

1 Pneumatic tire 2 Tread portion 2A Tread surface 3 Circumferential groove 4 Width groove 4A Chamfer 5 Land portion 5A Central land area 5B Side land area 6 Narrow groove 6A Bent portion 6Aa Bend point 7 Sipe A Virtual straight line

Claims (9)

At least two or more circumferential grooves extending along the tire circumferential direction on the tread surface of the tread portion and aligned in the tire width direction;
On the tread surface, a plurality of tires are provided so as to extend transversely with respect to the tire circumferential direction and are arranged side by side in the tire circumferential direction, and both ends communicate with any two circumferential grooves adjacent to each other in the tire width direction. A widthwise groove that forms a block-shaped land portion between the direction grooves,
Any two of the two adjacent to each other in the tire width direction, the two extending in the tire circumferential direction on the tread surface of the land portion, being provided side by side in the tire width direction, having both ends communicating with each of the width direction grooves. A narrow groove that divides the land portion defined by the circumferential groove and each of the widthwise grooves into a plurality of small land portions in the tire width direction,
Equipped with
The two narrow grooves in the land portion have a groove width smaller than that of the circumferential groove, and a bent portion is formed in the middle, and the two narrow grooves in the tire width direction are opposed to each other than a virtual straight line connecting both ends. A pneumatic tire in which the bent portion is arranged on the inner side, and the bending points of the bent portions are displaced from each other in the tire circumferential direction. The pneumatic tire according to claim 1, wherein the widthwise groove and the narrow groove are provided between all two circumferential grooves adjacent to each other in the tire width direction. The narrow groove, the bent angle of the bent portion is in a range of 160 ° or less 90 ° or more, the pneumatic tire according to claim 1 or 2. A deviation Lc in the tire circumferential direction between the bending points of the two narrow grooves is 0.1≦Lc/L with respect to a tire circumferential dimension L of the land portion where the narrow grooves are formed. The pneumatic tire according to any one of claims 1 to 3 . The width direction groove is formed to extend inclined with respect to the tire width direction, an angle range of 5 ° to 50 ° with respect to the tire width direction, one of the claims 1-4 1 Pneumatic tire described in 3. When the groove depth of the circumferential groove is Ha, the groove depth of the widthwise groove is Hb, and the groove depth of the narrow groove is Hc, the relationship of Ha>Hb, Ha>Hc is satisfied. The pneumatic tire according to any one of items 1 to 5 . The groove depth of the widthwise grooves Hb, when the groove depth of the narrow grooves was set to Hc, Hb is at 1mm 5mm or more or less, Hc is 1mm 5mm or more or less, any one of claims 1 to 6 The pneumatic tire described in 1. The widthwise groove is formed to extend obliquely with respect to the tire widthwise direction, and a chamfer is formed at a corner portion of the land portion that forms an acute angle with respect to the tire circumferential direction. The pneumatic tire according to any one of 1 to 7 . The tread surface further comprises a sipe formed so that one end communicates with the circumferential groove and the other end terminates in the land portion,
When the groove width of the sipe is Wd, the groove depth is Hd, the groove length is Ld, the tire widthwise dimension of the land portion is We, and the groove depth of the circumferential groove is Ha, 0.3 mm Pneumatic according to any one of claims 1 to 8 , which satisfies the relations of ≤Wd≤2.0 mm, 0.3≤Hd/Ha≤1.0, and 0.03≤Ld/We≤0.2. tire.

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