JP6916067B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Patent Document 1 discloses a pneumatic tire in which the ice-snow road surface performance and the steering stability performance are improved by the groove shape of the tread portion of the tire. This pneumatic tire is intended to increase the edges by forming a zigzag center main groove, thereby improving ice and snow road surface performance and steering stability performance.

Patent No. 6118307

However, in the pneumatic tire disclosed in Patent Document 1, there is room for improvement in the groove shape of the tread portion in order to further improve the ice-snow road surface performance and the steering stability performance.

An object of the present invention is to improve the ice-snow road surface performance and steering stability performance of a pneumatic tire.

In one aspect of the present invention, a center main groove formed so as to extend in a zigzag manner in the tire circumferential direction in a central region of the tread portion in the tire width direction, and a ground end side of the tread portion with respect to the center main groove. A shoulder main groove formed so as to extend in the tire circumferential direction, a center rib defined by the center main groove and the shoulder main groove, and arranged in a central region of the tread portion in the tire width direction, and one end thereof. Is communicated with the center main groove, the other end is terminated in the center rib, the center notch has a step portion in a portion adjacent to the tread portion, and the shoulder main groove is zigzag in the tire circumferential direction. Extends in the tire width direction, one end communicates with the zigzag-shaped bending point of the shoulder main groove, and the other end ends outside the tire width direction from the ground contact end, in the tire circumferential direction. Provided is a pneumatic tire further comprising a plurality of shoulder lateral grooves arranged at intervals, and the center notch and the shoulder lateral grooves are provided at the same positions in the tire circumferential direction.

According to this configuration, since the center main groove is formed in a zigzag manner and the center notch is provided with a stepped portion, the number of edges can be increased. As a result, the icy and snowy road surface performance, that is, the traction performance and the braking performance on the icy and snowy road surface are improved, and the steering stability performance at the time of turning is also improved. Further, since the two-stage structure is formed by providing the step portion in the center notch, the deformation resistance of the center rib to the load on the center notch is increased. That is, the rigidity of the center rib is improved as compared with the case where the center notch is not provided with the stepped portion. By improving the rigidity of the center rib, the steering stability performance when going straight is improved. The above configuration is more effective when adopted for snow tires that require particularly high ice / snow road surface performance and steering stability performance. Further, by forming the shoulder main groove in a zigzag pattern, the edges can be increased. Further, when the center notch touches the ground, the inflection point of the shoulder main groove and the shoulder lateral groove also touch the ground, so that the number of edges that touch the ground at one time can be increased. As a result, the number of edges that come into contact with the ground at one time can be increased, so that the icy / snow road surface performance and the steering stability performance can be improved. Here, the inflection point of the shoulder main groove means a point where the direction in which the shoulder main groove extends changes in the tire width direction. Further, the fact that the center notch and the shoulder lateral groove are provided at the same position in the tire circumferential direction means that at least a part of the center notch and the shoulder lateral groove overlap in the tire circumferential direction.

The one end of the center notch may communicate with the zigzag inflection point of the center main groove.

According to this configuration, the edge forming the inflection point and the edge forming the stepped portion of the center notch can be collected in the vicinity of the inflection point of the center main groove. As a result, the number of edges that touch the ground at one time can be increased. Therefore, in the vicinity of the inflection point, the road surface can be scratched with more edges at one time, and the ice / snow road surface performance and steering stability performance can be improved. Here, the inflection point of the center main groove means a point where the direction in which the center main groove extends changes in the tire width direction.

The center notch is a cross section in the orthogonal direction with a first portion extending from the bottom wall defining the center main groove toward the surface of the tread portion in a cross-sectional view in a direction orthogonal to the direction in which the center notch extends. In view, one end is connected to the upper end of the first part and extends so as to expand the groove width of the center notch, and in the cross-sectional view in the orthogonal direction, one end is attached to the other end of the second part. The other end is provided with a third portion connected to the surface of the tread portion, the step portion is a connecting portion between the first portion and the second portion, and the center rib is the tread. A main edge connecting the surface of the portion and the third portion, and a sub-edge connecting the first portion and the second portion may be provided.

According to this configuration, the ground contact area of the center rib is determined not by the sub-edge but by the main edge located inside the sub-edge in the tire radial direction. That is, by adopting the edge of the two-stage structure, the ratio of the ground contact area to the volume of the center rib can be reduced. By reducing the contact area, the contact pressure of the center rib increases. Further, in the center notch, a step portion is provided so that the groove width increases from the groove bottom toward the surface of the tread portion. Therefore, the snow pillar formed in the center rib when traveling on a snowy road surface has a shape in which the base end portion is thicker than the tip portion. As a result, the shear force of the snow column is increased and the snow road surface performance is improved.

The pneumatic tire further includes a shoulder block defined by the shoulder main groove and two shoulder lateral grooves adjacent to each other in the tire circumferential direction, and inflection of the center main groove in the tire circumferential direction. When the center rib is divided into the center rib units for each point, one center rib unit may be provided for each of the two shoulder blocks.

According to this configuration, since one center rib unit is provided for each of the two shoulder blocks, the edge of the shoulder block can be made larger than the edge of the center rib. It is preferable that the edge of the shoulder block is large because it contributes to the steering stability performance at the time of turning. The rigidity of the center rib is preferably high in order to improve the steering stability performance when traveling straight. Therefore, in order to increase the edge of the shoulder block and maintain the rigidity of the center rib high, it is effective to provide one center rib unit for each of the two shoulder blocks. In particular, since one center rib unit is provided for each of the two shoulder blocks, the appearance is also well-controlled and aesthetically pleasing.

Further, according to this configuration, one center rib unit is provided for two shoulder blocks, that is, the zigzag swell cycle of the center main groove is the zigzag swell cycle of the shoulder main groove. Is twice as much. The center main groove and the shoulder main groove are also channels for draining water to the outside. In particular, since the center main groove is provided in the central portion of the tire, higher drainage performance is required than the shoulder main groove provided in the side portion. In the above configuration, both the center main groove and the shoulder main groove have a zigzag shape, but when the zigzag shape undulation cycle becomes smaller, the drainage channel undulates more, and thus the drainage performance deteriorates. In the above configuration, the center main groove is made larger than the shoulder main groove for the zigzag-shaped swell cycle, so that the swell of the center main groove is reduced and drainage from the center main groove is facilitated.

According to the present invention, in a pneumatic tire, the center main groove is formed in a zigzag shape and the center notch is provided with a stepped portion, so that the edge can be increased and the ice / snow road surface performance and steering stability performance are improved. Can be done.

The perspective view of the pneumatic tire which concerns on embodiment of this invention. The development view of the tread portion of the pneumatic tire of FIG. 1 and its periphery. A partially enlarged view of FIG. Enlarged view of the center rib. FIG. 4 is a cross-sectional view taken along the line VV of FIG. FIG. 4 is a cross-sectional view taken along the line VI-VI of FIG. Enlarged view of the shoulder block. FIG. 7 is a cross-sectional view taken along the line VIII-VIII of FIG. FIG. 7 is a cross-sectional view taken along the line IX-IX of FIG. FIG. 7 is a cross-sectional view taken along the line X-X, line X'-X', and X''-X'' in FIG. FIG. 7 is a cross-sectional view taken along the XI-XI line and the XI'-XI' line of FIG.

In the following description, the terms "upward to right" and "downward to the right" are used for the inclination of a structure having a longitudinal direction such as a groove formed in a tread portion and a sipe in a plan view or a tire radial direction view. In some cases.

The term "upward to the right" refers to a case where the longitudinal direction of the structure and the circumferential direction of the tire overlap by rotating the circumferential direction of the tire clockwise at a sharp angle around the intersection of the longitudinal direction of the structure and the circumferential direction of the tire. The term "upward to the right" is used when the longitudinal direction of the structure and the circumferential direction of the tire overlap by rotating the tire width direction at a sharp angle counterclockwise around the intersection of the longitudinal direction of the structure and the tire width direction. Say.

The term "downward to the right" refers to the case where the longitudinal direction of the structure and the circumferential direction of the tire overlap by rotating the circumferential direction of the tire in a sharp counterclockwise direction around the intersection of the longitudinal direction of the structure and the circumferential direction of the tire. .. In addition, the term "downward to the right" refers to the case where the longitudinal direction of the structure and the circumferential direction of the tire overlap by rotating the tire width direction clockwise at a sharp angle around the intersection of the longitudinal direction of the structure and the tire width direction. To tell.

In the following description, when the positive / negative sign of the angle formed by the groove formed in the tread portion and the structure having a longitudinal direction such as a sipe with respect to the tire circumferential direction or the tire width direction in the tire radial direction is "upward to the right". Is positive, and the case of "downward to the right" is negative.

(Outline of tread and its surroundings)
1 to 3 show the tread portion 2 of the rubber pneumatic tire (hereinafter referred to as a tire) 1 according to the embodiment of the present invention and its surroundings. This tire 1 is a snow tire.

In the figure, the tire circumferential direction is indicated by reference numeral TC, and the tire width direction is indicated by reference numeral TW. Further, the center line (equator line) of the tread portion 2 in the tire width direction is indicated by reference numeral CL. Further, the ground contact ends of both ends of the tread portion 2 in the tire width direction are indicated by reference numerals GE1 and GE2. In the following description, when it is not necessary to distinguish between the two grounding ends GE1 and GE2, one of them may be simply referred to as the grounding end GE.

In the present specification, the region of the outer circumference of the tire sandwiched between the two ground contact ends GE1 and GE2 is referred to as a tread portion 2. Further, a flat portion or a portion having a relatively small curvature, which is located outside the tread portion 2 in the tire width direction and is substantially orthogonal to the tire axial direction, is referred to as a side portion 3. Further, a portion curved with a relatively large curvature connecting the tread portion 2 and the side portion 3 is referred to as a shoulder portion 4.

A center main groove 5 extending in the tire circumferential direction is formed on the central region of the tread portion 2 in the tire width direction, more specifically, on the center line CL. The center main groove 5 is not linear but meandering or zigzag in the tire radial direction.

With reference to FIG. 2, the zigzag shape of the center main groove 5 is formed by alternately providing a long groove portion 5a inclined upward to the right and a short groove portion 5b inclined downward to the right. The long groove portion 5a is longer than the short groove portion 5b, and the inclination angle α1 of the long groove portion 5a from the tire circumferential direction is smaller than the inclination angle α2 of the short groove portion 5b from the tire circumferential direction. The tilt angle α1 can be set in the range of 1 degree or more and 20 degrees or less, and the tilt angle α2 can be set to a value larger than the tilt angle α1 of 5 degrees or more and 60 degrees or less.

Shoulder main grooves 6A and 6B extending in the tire circumferential direction are formed on the ground contact ends GE1 and GE2 sides of the center main groove 5 of the tread portion 2. The two shoulder main grooves 6A and 6B are adjacent to the center main groove 5 in the tire width direction, respectively. The shoulder main grooves 6A and 6B are not linear but meandering or zigzag in the tire radial direction. In the following description, when it is not necessary to distinguish between the two shoulder main grooves 6A and 6B, one of them may be simply referred to as the shoulder main groove 6.

With reference to FIG. 2, the zigzag shape of the shoulder main groove 6 is formed by alternately providing a long groove portion 6a inclined upward to the right and a short groove portion 6b inclined downward to the right. The long groove portion 6a is longer than the short groove portion 6b, and the inclination angle α3 of the long groove portion 6a from the tire circumferential direction is smaller than the inclination angle α4 of the short groove portion 6b from the tire circumferential direction. Tilt angle α3 can be set in the range of 30 degrees or less than 1 degree, the inclination angle α4 may be set to have a size value than the inclination angle α3 below 60 degrees 5 degrees. Further, the long groove portion 6a of the shoulder main groove 6 is shorter than the long groove portion 5a of the center main groove 5, and is about half the length in the present embodiment.

In the central region of the tread portion 2 in the tire width direction, a center rib 7A extending in the tire circumferential direction is defined by a center main groove 5 and a shoulder main groove 6A. Further, in the central region in the tire width direction, a center rib 7B extending in the tire circumferential direction is defined by a center main groove 5 and a shoulder main groove 6B. In the following description, when it is not necessary to distinguish between the two center ribs 7A and 7B, one of them may be simply referred to as the center rib 7.

In the two shoulder regions on both ends of the tread portion 2 in the tire width direction, that is, the two regions adjacent to the ground contact ends GE1 and GE2, a plurality of shoulder lateral grooves 8A and 8B arranged at intervals in the tire circumferential direction are provided. Each is provided.

The shoulder lateral groove 8A extends substantially in the tire width direction, one end communicating with the zigzag inflection point of the shoulder main groove 6A, and the other end extending beyond the ground contact end GE1 and the shoulder portion 4. The other end of the shoulder lateral groove 8A is located on the side portion 3. Here, the zigzag-shaped inflection point of the shoulder main groove 6 means a point where the direction in which the shoulder main groove 6 extends changes in the tire width direction. In other words, it means that the upward-sloping slope and the downward-sloping slope are interchanged.

Similarly, the shoulder lateral groove 8B extends substantially in the tire width direction, one end communicates with the shoulder main groove 6B, and the other end is located on the ground contact end GE2 and the side portion 3 outside the tire width direction from the shoulder portion 4. ..

In the following description, when it is not necessary to distinguish the shoulder lateral grooves 8A and 8B, one of them may be simply referred to as the shoulder lateral groove 8.

A plurality of shoulder blocks 9A defined by a shoulder main groove 6A and two shoulder lateral grooves 8A adjacent to each other in the tire circumferential direction are arranged in the tire circumferential direction in a portion of the tread portion 2 on the ground contact end GE1 side. ing.

The shoulder block 9A has an elongated shape in the tire width direction. The inner end of the shoulder block 9A in the tire width direction is located at the tread portion 2. The shoulder block 9A extends outward in the tire width direction beyond the ground contact end GE1 and the shoulder portion 4. The outer end of the shoulder block 9A in the tire width direction is located at the side portion 3.

Similarly, a plurality of shoulder blocks 9B defined by a shoulder main groove 6B and two shoulder lateral grooves 8B adjacent to each other in the tire circumferential direction are formed on the ground contact end GE2 side of the tread portion 2 in the tire circumferential direction. They are lined up in. The shoulder block 9B has an elongated shape in the tire width direction. The inner end of the shoulder block 9B in the tire width direction is located at the tread portion 2, and the outer end of the shoulder block 9B is located at the side portion 3.

In the following description, when it is not necessary to distinguish the shoulder blocks 9A and 9B, one of them may be simply referred to as the shoulder block 9.

The center rib 7 is provided with a plurality of center notches 11 at regular intervals in the tire circumferential direction. The center notch 11 is provided at the same position as the shoulder lateral groove 8 in the tire circumferential direction. Here, the same position means that at least a part of the center notch 11 and the shoulder lateral groove 8 overlaps in the tire circumferential direction. The center notch 11 is inclined upward to the right. One end (base end) of the center notch 11 is connected to the center main groove 5, and the other end (tip) is terminated in the center rib 7. The center notch 11 has a shape in which the tip is bent. As will be described in detail later, each of the pair of side walls 11d defining the center notch 11 has a step portion 11h, and two edges, that is, a main edge 11i and a sub edge 11j are formed (FIG. 5). See also). The step portion 11h may be provided only on one of the pair of side walls 11d.

The center rib 7 is provided with a plurality of side notches 12 at regular intervals in the tire circumferential direction. The side notch 12 is inclined upward to the right. One end (base end) of the side notch 12 is connected to the shoulder main groove 6, and the other end (tip) is terminated in the center rib 7. As will be described in detail later, the pair of side walls 12b defining the side notches 12 each have a stepped portion 12f, and two edges, that is, a main edge 12g and a sub edge 12h are formed (FIG. 6). See also). The step portion 12f may be provided only on one of the pair of side walls 12b.

Two straight sipes 13A and 13B are provided at a portion of the center rib 7 facing the center notch 11 in the tire width direction at intervals in the tire circumferential direction. One end (base end) of the straight sipe 13A and 13B is connected to the shoulder main groove 6, and the other end (tip) is terminated in the center rib 7. Both the straight sipe 13A and 13B are inclined downward to the right. Further, these straight sipe 13A and 13B extend substantially parallel to each other. The center rib 7 is provided with a straight sipe 13C that is inclined downward to the right at intervals in the tire circumferential direction with respect to the straight sipe 13B. One end (base end) of the straight sipe 13C is connected to the shoulder main groove 6, and the other end (tip) is terminated in the center rib 7.

Two straight sipes 14A and 14B are provided at a portion of the center rib 7 facing the side notch 12 in the tire width direction at intervals in the tire circumferential direction. One end (base end) of the straight sipe 14A and 14B is connected to the center main groove 5, and the other end (tip) is terminated in the center rib 7. Both the straight sipe 14A and 14B are inclined downward to the right. Further, these straight sipe 14A and 14B extend substantially parallel to each other. The center rib 7 is provided with a straight sipe 14C that is inclined downward to the right at intervals in the tire circumferential direction with respect to the straight sipe 14B. One end (base end) of the straight sipe 14C is connected to the shoulder main groove 6, and the other end (tip) is terminated in the center rib 7.

The center rib 7 is provided with three corrugated sipes 15A to 15C in a portion between one center notch 11 and the side notch 12 adjacent to the center notch 11 in the tire circumferential direction. All of these corrugated sipes 15A to 15C are inclined upward to the right. One end of the corrugated sipe 15A adjacent to the center notch 11 in the tire circumferential direction is connected to the center main groove 5, and the other end is terminated in the center rib 7. The corrugated sipe 15C adjacent to the side notch 12 in the tire circumferential direction has one end connected to the shoulder main groove 6 and the other end terminated in the center rib 7. Wavy sipes 15 B located between wave-shaped sipes 15A, 15 C has one end communicated with the center main groove 5 and the other end is communicated with the shoulder main groove 6.

As will be described in detail later, the pair of side walls 8d defining the shoulder lateral groove 8 has a step portion 8h, and the corner portion extending in the tire width direction of the shoulder block 9 has two edges, that is, a main edge 9a and a sub edge. It has 9b (see FIGS. 8 and 9). The step portion 8h may be provided only on one of the pair of side walls 8d.

A single intermittent sipe 21 extending in the tire width direction as a whole is provided at the central portion of the shoulder block 9 in the tire circumferential direction. One end of the intermittent sipe 21 is connected to the shoulder main groove 6, and the other end extends outward in the tire width direction beyond the ground contact end G. The other end of the intermittent sipe 21 is terminated at the boundary between the shoulder portion 4 and the side portion 3 (see FIG. 2). As will be described in detail later, the intermittent sipe 21 is provided with deep portions 21a, 21c, 21e and shallow portions 21b, 21d extending in different directions with respect to the tire width direction, and has a shape in the tire radial direction. Is generally zigzag.

The shoulder block 9 is provided with a pair of composite sipes 22 so as to be located on both sides of the intermittent sipes 21 in the tire circumferential direction. One end of the composite sipe 22 is connected to the shoulder main groove 6, and the other end is terminated in the shoulder block 9. The composite sipe 22 includes a straight sipe portion 22a on one end side and a corrugated sipe portion 22b on the other end side.

A pair of straight sipes 23 extending substantially in the tire width direction are provided on the outer portion of the shoulder block 9 in the tire width direction. One end of the straight sipe 23 is located at the shoulder portion 4, and the other end is located at the side portion 3. The pair of straight sipe 23s are arranged so as to sandwich the intermittent sipe 21 in the tire circumferential direction.

The side portion 3 is provided with a continuous projection portion 24.

(Details of center rib)
Hereinafter, the details of the center rib 7 will be described mainly with reference to FIG. As described above, the center rib 7 is provided with a center notch 11, a side notch 12, a straight sipe 13A to 13C, a straight sipe 14C, and a corrugated sipe 15A to 15C.

When the center rib 7 is divided into the center rib unit 7C (see the inside of the alternate long and short dash line frame in FIG. 2) for each inflection point of the center main groove 5 in the tire circumferential direction, one for every two shoulder blocks 9. A center rib unit 7C is provided.

The center notch 11 includes a main body portion 11a whose base end is connected to the center main groove 5, and a tip portion 11b that is bent with respect to the tip end of the main body portion 11a. Specifically, the main body portion 11a of the center notch 11 communicates with the zigzag-shaped inflection point of the center main groove 5. Here, the zigzag-shaped inflection point of the center main groove 5 means a point where the direction in which the center main groove 5 extends changes in the tire width direction. In other words, it means that the upward-sloping slope and the downward-sloping slope are interchanged. The width of the center notch 11 gradually decreases from the base end of the main body portion 11a toward the tip end of the tip end portion 11b. In the present embodiment, the angle θ1 of the main body portion 11a with respect to the tire circumferential direction is 73 degrees, and the angle θ2 of the tip portion 11b with respect to the tire circumferential direction is 30 degrees, which is smaller than the angle θ1. The angle θ1 can be set in the range of 30 degrees or more and 85 degrees or less, and the angle θ2 can be set to a value smaller than the angle θ1 of 0 degrees or more and 60 degrees or less.

With reference to FIG. 5, the center notch 11 is defined by a bottom wall 11c and a pair of side walls 11d facing each other. Each side wall 11d has a first portion 11e, a second portion 11f, and a third portion 11g. In the present embodiment, the first portion 11e, the second portion 11f, and the third portion 11g of the side wall 11d are all flat surfaces. The first portion 11e extends substantially in the tire radial direction from the bottom wall 11c toward the surface of the center rib 7 in a cross-sectional view in a direction orthogonal to the direction in which the center notch 11 extends. In the same cross-sectional view, the second portion 11f extends substantially in the tire circumferential direction so that one end is connected to the upper end of the first portion 11e and the width of the center notch 11 is widened. In the same cross-sectional view, the third portion 11g has a lower end connected to the other end of the second portion 11f and an upper end connected to the surface of the center rib 7.

In the cross-sectional view in the direction orthogonal to the direction in which the center notch 11 extends, the direction in which the side wall 11d extends suddenly changes at the connecting portion between the first portion 11e and the second portion 11f. That is, a step portion 11h is formed at the connecting portion between the first portion 11e and the second portion 11f. This connecting portion is a portion adjacent to the tread portion 2, and in the present embodiment, is a portion that is one paragraph from the surface of the tread portion 2. By providing the stepped portion 11h, the opening edge of the center notch 11 has two edges, that is, a main edge 11i on the surface side of the center rib 7, and a sub edge 11j on the inner side in the tire radial direction. The main edge 11i is formed at a connection point between the surface of the center rib 7 and the third portion 11g of the side wall 11d. The sub-edge 11j is formed at a connection point between the first portion 11e of the side wall 11d and the second portion 11f of the side wall 11d.

The width W1 of the step portion 11h (width of the second portion 11f of the side wall 11d) can be set in a range of 0.1 times or more and 1.0 times or less of the width W2 of the center notch 11 in the first portion 11e. The width W1 can be set in the range of 0.3 mm or more and 3 mm or less. The width W2 of the center notch 11 can be set in the range of 1.2 mm or more and 10 mm or less. Therefore, the width of the center notch 11 including the width W1 of the step portion 11h can be set in the range of 1.8 mm or more and 16 mm or less. Further, the depth position (height of the third portion 11g of the side wall 11d) DE1 from the surface of the center rib 7 of the step portion 11h is 0.05 times or more and 0.5 times or less of the depth DE2 of the center notch 11. Can be set in the range. The depth DE2 of the center notch 11 can be set in the range of 2 mm or more and 13 mm or less. In the present embodiment, in the cross-sectional view orthogonal to the direction of the center notch 11 extends, the angle γ1 second portion 11f of the side wall 11d with respect to the surface of the cell Ntaribu 7 is 0 degrees. This angle γ1 can be set in the range of −30 degrees or more and 30 degrees or less (the positive and negative signs of the angle γ1 are clockwise in FIG. 5).

The width of the side notch 12 gradually decreases from the proximal end to the distal end. In the present embodiment, the angle θ3 of the side notch 12 with respect to the tire circumferential direction is 70 degrees. The angle θ3 can be set in the range of 30 degrees or more and 85 degrees or less.

Referring to FIG. 6, the side notch 12 is defined by a bottom wall 12a and a pair of side walls 12b facing each other. Any of the side wall 12b also has a first portion 12c, the second portion 12d, and a third portion 12 e. In the present embodiment, the first portion 12c, the second portion 12d, and the third portion 12e of the side wall 12b are all flat surfaces. The first portion 12c extends substantially in the tire radial direction from the bottom wall 12a toward the surface of the center rib 7 in a cross-sectional view in a direction orthogonal to the direction in which the side notch 12 extends. In the same cross-sectional view, the second portion 12d extends substantially in the tire circumferential direction so that one end is connected to the upper end of the first portion 12c and the width of the side notch 12 is widened. In the same cross-sectional view, the third portion 12e has a lower end connected to the other end of the second portion 12d and an upper end connected to the surface of the center rib 7.

In the cross-sectional view in the direction orthogonal to the direction in which the side notch 12 extends, the direction in which the side wall 12b extends suddenly changes at the connecting portion between the first portion 12c and the second portion 12d. That is, a step portion 12f is formed at the connecting portion between the first portion 12c and the second portion 12d. By providing the stepped portion 12f, the opening edge of the side notch 12 has two edges, that is, a main edge 12g on the surface side of the center rib 7, and a sub edge 12h on the inner side in the tire radial direction. First, the main edge 12g is formed at a connection point between the surface of the center rib 7 and the third portion 12e of the side wall 12b. Further, the sub-edge 12h is formed at a connection portion between the first portion 12c of the side wall 12b and the second portion 12d of the side wall 12b.

The width W3 of the step portion 12f (width of the second portion 12d of the side wall 12b) W3 can be set in a range of 0.1 times or more and 1.0 times or less of the width W4 of the side notch 12 in the first portion 12c. The width W4 can be set in the range of 0.3 mm or more and 3 mm or less. The width W4 of the side notch 12 can be set in the range of 1.2 mm or more and 10 mm or less. Therefore, the width of the side notch 12 including the width W3 of the step portion 12f can be set in the range of 1.8 mm or more and 16 mm or less. Further, the depth position (height of the third portion 12e of the side wall 12b) DE3 from the surface of the side notch 12 of the step portion 12f is 0.05 times or more and 0.5 times or less of the depth DE4 of the side notch 12. Can be set in the range. The depth DE4 of the side notch 12 can be set in the range of 2 mm or more and 13 mm or less. In the present embodiment, the angle γ2 formed by the second portion 12d of the side wall 12b with respect to the surface of the side notch 12 is 0 degrees in the cross-sectional view in the direction orthogonal to the direction in which the side notch 12 extends. This angle γ2 can be set in the range of −30 degrees or more and 30 degrees or less (the positive and negative signs of the angle γ2 are clockwise in FIG. 6).

As described above, the center rib 7 is provided with two straight sipes 13A and 13B at a portion facing the center notch 11 in the tire width direction. Here, "opposing in the tire width direction" means that at least a part of these straight sipes 13A and 13B overlap in the tire circumferential direction with respect to the center notch 11. The center notch 11 is inclined upward to the right (the angle θ1 is 30 degrees or more and 85 degrees or less, and the angle θ2 is 0 degrees or more and 60 degrees or less), whereas the straight sipe 13A and 13B are inclined downward to the right. .. The angle θ4 of the straight sipe 13A and 13B with respect to the tire radial direction can be set in the range of −30 degrees or more and −85 degrees or less. As described above, the straight sipe 13A and 13B extend so as to form an angle θ4 with respect to the tire circumferential direction so that the positive and negative signs are different from the angles θ1 and θ2 of the center notch 11. Therefore, the virtual line indicating the direction in which the center notch 11 extends and the virtual line indicating the direction in which the straight lines 13A and 13B extend form a convex polygonal line in one direction (upward in FIG. 4) in the tire circumferential direction. ..

The tip of the center notch 11 and the tips of the straight sipes 13A and 13B facing the center notch 11 in the tire width direction and closest to the center main groove 5 are located in the central region of the center rib 7 in the tire width direction. Can be located. Specifically, these tips may be arranged in the range of the width CRW1 centered on the center in the width direction of the center rib 7 (indicated by the reference numeral CRC in FIG. 4). Here, the width CRW1 can be set in a range of 0.1 times or more and 0.4 times or less the width CRW0 (mean width) of the center rib 7.

The width of the straight sipe 13A and 13B can be set to 0.3 mm or more and 1.5 mm or less. Further, the depth of the straight sipe 13A and 13B can be set to 2 mm or more and 13 mm or less.

As described above, the center rib 7 is provided with two straight sipes 14A and 14B at a portion facing the side notch 12 in the tire width direction. Here, "opposing in the tire width direction" means that at least a part of these straight sipes 14A and 14B overlap in the tire circumferential direction with respect to the side notch 12. The side notch 12 is inclined upward to the right (the angle θ3 is 30 degrees or more and 85 degrees or less), whereas the straight sipe 14A and 14B are inclined downward to the right. The angle θ5 of the straight sipe 14A and 14B with respect to the tire radial direction can be set in the range of −30 degrees or more and −85 degrees or less. As described above, the straight sipe 14A and 14B extend so as to form an angle θ5 with respect to the tire circumferential direction so that the positive and negative signs are different from the angle θ3 of the side notch 12. Therefore, the virtual line indicating the direction in which the side notch 12 extends and the virtual line indicating the direction in which the straight lines 14A and 14B extend form a convex polygonal line in one direction (downward in FIG. 4) in the tire circumferential direction. ..

The tip of the side notch 12 and the tip of the straight sipe 14A, 14B facing the side notch 12 in the tire width direction, which is closest to the shoulder main groove 6, can be arranged within the range of the width CRW1 described above.

The width of the straight sipe 14A and 14B can be set to 0.3 mm or more and 1.5 mm or less. Further, the depth of the straight sipe 14A and 14B can be set to 2 mm or more and 13 mm or less.

(Details of shoulder lateral groove and shoulder block)
Hereinafter, the details of the shoulder lateral groove 8 and the shoulder block 9 will be described mainly with reference to FIG. 7. As described above, the shoulder block 9 is provided with one intermittent sipe 21, two composite sipe 22, and two straight sipe 23.

The shoulder lateral groove 8 includes an inner portion 8a connected to the shoulder main groove 6 and an outer portion 8b having one end connected to the inner portion 8a and extending outward in the tire width direction beyond the ground contact end GE. With reference to FIG. 2, the other end of the outer portion 8b is located at the boundary between the shoulder portion 4 and the side portion 3 as described above.

The shoulder lateral groove 8 extends in the tire width direction, but the inner portion 8a and the outer portion 8b have different inclinations with respect to the tire width direction. First, the inner portion 8a is inclined upward to the right, and the angle θ6 of the inner portion 8a with respect to the tire width direction can be set in the range of 2 degrees or more and 45 degrees or less. Next, the outer portion 8b is inclined downward to the right, and the angle θ7 of the outer portion 8b with respect to the tire width direction can be set in the range of -2 degrees or more and -20 degrees or less.

The dimension of the inner portion 8a of the shoulder lateral groove 8 in the tire width direction is shorter than the dimension of the outer portion 8b of the shoulder lateral groove 8 in the tire width direction. The length of the inner portion 8a can be set in the range of 0.1 times or more and 0.4 times or less the length of the outer portion 8b.

With reference to FIGS. 8 and 9, the width W5 of the inner portion 8a of the shoulder lateral groove 8 is set to be narrower than the width W6 of the outer portion 8b of the shoulder lateral groove 8. The width W5 of the inner portion 8a of the shoulder lateral groove 8 gradually decreases toward the shoulder main groove 6. In the present embodiment, the depth DE5 of the inner portion 8a of the shoulder lateral groove 8 and the depth DE6 of the outer portion 8b of the shoulder lateral groove 8 are set to be the same. The depth DE5 of the inner portion 8a may be set shallower than the depth DE6 of the outer portion 8b. The depths DE5 and DE6 of the shoulder lateral groove 8 can be set in the range of 2 mm or more and 13 mm or less.

Continuing with reference to FIGS. 8 and 9, the shoulder lateral groove 8 is defined by a bottom wall 8c and a pair of side walls 8d facing each other. Each side wall 8d has a first portion 8e, a second portion 8f, and a third portion 8g. In the present embodiment, the first portion 8e, the second portion 8f, and the third portion 8g of the side wall 8d are all flat surfaces. The first portion 8e extends substantially in the tire radial direction from the bottom wall 8c toward the surface of the shoulder block 9 in a cross-sectional view in a direction orthogonal to the direction in which the shoulder lateral groove 8 extends. In the same cross-sectional view, the second portion 8f extends substantially in the tire circumferential direction so that one end is connected to the upper end of the first portion 8e and the width of the shoulder lateral groove 8 is widened. In the same cross-sectional view, the third portion 8g has a lower end connected to the other end of the second portion 8f and an upper end connected to the surface of the shoulder block 9.

In the cross-sectional view in the direction orthogonal to the direction in which the shoulder lateral groove 8 extends, the direction in which the side wall 8d extends suddenly changes at the connecting portion between the first portion 8e and the second portion 8f. That is, a step portion 8h is formed at the connecting portion between the first portion 8e and the second portion 8f. As described above, the shoulder lateral groove 8 defines the shoulder block 9 together with the shoulder main groove 6. More specifically, the side wall 8d of the shoulder lateral groove 8 constitutes a corner portion extending in the tire width direction of the shoulder block 9 together with the surface of the tread portion 2. By providing the stepped portion 8h on the side wall 8d of the shoulder lateral groove 8, the corner portion extending in the tire width direction of the shoulder block 9 is composed of two steps of edges instead of a single edge. That is, the corner portion of the shoulder block 9 extending in the tire width direction has a main edge 9a on the surface side of the shoulder block 9 and a sub edge 9b on the inner side in the tire radial direction. The main edge 9a is formed at a connection point between the surface of the shoulder block 9 and the third portion 8g of the side wall 8d of the shoulder lateral groove 8. The sub-edge 9b is formed at a connection point between the first portion 8e and the side wall 8d of the side wall 8d of the shoulder lateral groove 8.

The width W7 of the step portion 8h (width of the second portion 8f of the side wall 8d) can be set in a range of 0.1 times or more and 1.0 times or less of the widths W5 and W6 of the shoulder lateral grooves 8 in the first portion 8e. Further, the depth position (height of the third portion 8 g of the side wall 8d) DE7 from the surface of the shoulder block 9 of the step portion 8h is 0.05 times or more and 0.5 times the depths DE5 and DE6 of the shoulder lateral grooves 8. It can be set in the following range. In the present embodiment, the angle γ3 formed by the second portion 8f of the side wall 8d with respect to the surface of the shoulder block 9 is 0 degrees in the cross-sectional view in the direction orthogonal to the direction in which the shoulder lateral groove 8 extends. This angle γ3 can be set in the range of -30 degrees or more and 30 degrees or less (the positive and negative signs of the angle γ3 are clockwise in FIGS. 8 and 9).

The intermittent sipe 21 extends substantially in a zigzag shape in the tire width direction from the shoulder main groove 6 to the boundary between the shoulder portion 4 and the side portion 3 (see also FIG. 2) in the tire radial direction. The intermittent sipe 21 includes two types of elements arranged alternately, that is, deep portions 21a, 21c, 21e and shallow portions 21b, 21d. These elements are arranged in the order of the deep portion 21a, the shallow portion 21b, the deep portion 21c, the shallow portion 21d, and the deep portion 21e from the shoulder main groove 6 toward the outside in the tire width direction. Specifically, one end of the deep portion 21a communicates with the shoulder main groove 6, and the other end communicates with one end of the shallow portion 21b. The other end of the shallow portion 21b communicates with one end of the deep portion 21c. The other end of the deep portion 21c communicates with one end of the shallow portion 21d. The other end of the shallow portion 21d communicates with one end of the deep portion 21e. The other end of the deep portion 21e is terminated in the shoulder block 9.

With reference to FIGS. 10 and 11, the intermittent sipe 21 is one continuous element from the deep portion 21a, which is an element connected to the shoulder main groove 6, to the deep portion 21e, which is an element farthest from the shoulder main groove 6. A shallow groove 21A is provided. In other words, the shallow groove 21A is provided in common to all the elements constituting the intermittent sipe 21, that is, the deep portions 21a, 21c, 21e and the shallow portions 21b, 21d. The shallow groove 21A is open on the surface of the shoulder block 9.

In the deep portions 21a, 21c, 21e, sipe main bodies 21f, 21g, 21h communicating with the shallow groove 21A are further provided. The upper ends of the sipe main body 21f, 21g, 21h communicate with the lower part of the shallow groove 21A. In this embodiment, the sipe main bodies 21f, 21g, and 21h are straight sipe.

The shallow portions 21b and 21d are not provided with a sipe body, and are composed only of the shallow groove 21A. Therefore, the sipe main bodies 21f, 21g, 21h of the deep portions 21a, 21c, 21e do not communicate with each other. In other words, the deep portion 21a and the deep portion 21c are spatially connected only by the shallow groove 21A constituting the shallow portion 21b interposed between them. Further, the deep portion 21c and the deep portion 21e are spatially connected only by the shallow groove 21A constituting the shallow portion 21d interposed between them.

Referring to FIG. 7, in the present embodiment, all the elements constituting the intermittent sipe 21, that is, the deep portions 21a, 21c, 21e and the shallow portions 21b, 21d are linear in the tire radial direction. Regarding the dimension in the tire width direction, that is, the length, the length L1 of the deep portion 21a and the length L2 of the deep portion 21c are substantially the same, and the length L3 of the deep portion 21e is from the lengths L1 and L2 of the deep portions 21a and 21c. Is long enough. The lengths L1, L2, and L3 of the deep portions 21a, 21c, and 21e can be set in a range of 0.1 times or more and 0.5 times or less of the total length L4 in the tire width direction of the shoulder block 9. The lengths L5 and L6 of the shallow portions 21b and 21d are sufficiently shorter than the lengths L1, L2 and L3 of the deep portions 21a, 21c and 21e. The lengths L5 and L6 of the shallow portions 21b and 21d can be set in a range of 0.1 times or more and 0.5 times or less the shortest of the lengths L1, L2 and L3 of the deep portions 21a, 21c and 21e.

The deep portion 21c is offset in the tire circumferential direction with respect to the deep portion 21a. Further, the deep portion 21e is offset in the tire circumferential direction with respect to the deep portion 21c. In this embodiment, the deep portion 21c is offset downward in FIG. 7 with respect to the deep portion 21a, and the deep portion 21e is offset downward in FIG. 7 with respect to the deep portion 21c. In the present embodiment, the angles θ8, θ9, and θ10 formed by the deep portions 21a, 21c, and 21e in the tire width direction are all 0 degrees. The angles θ8 to θ10 can be set in the range of −20 degrees or more and 20 degrees or less.

In the present embodiment, the shallow portions 21b and 21d are inclined downward to the right, and the angles θ11 and θ12 formed by these in the tire width direction are −30 degrees. When the deep portions 21a, 21c, 21e are offset-arranged in the manner as in this embodiment, the angles θ11 and θ12 can be set in the range of -2 degrees or more and -45 degrees or less. Further, unlike the present embodiment, when the deep portion 21c is offset upward in FIG. 7 with respect to the deep portion 21a and the deep portion 21e is offset upward in FIG. 7 with respect to the deep portion 21c, the shallow portions 21b and 21d are It will have an upward slope. In this case, the angles θ11 and θ12 can be set in the range of 2 degrees or more and 45 degrees or less. Therefore, the absolute values of the angles θ11 and θ12 can be set in the range of 2 degrees or more and 45 degrees or less.

With reference to FIGS. 10 and 11, the shallow groove 21A is defined by a pair of side walls 21i facing each other in the tire circumferential direction. Further, the sipe main body 21f, 21g, 21h is defined by a bottom wall 21j facing the opening of the shallow groove 21A in the tire radial direction and a pair of flat side walls 21k.

The side wall 21i defining the shallow groove 21A has a tapered shape in a cross-sectional view in a direction orthogonal to the direction in which the shallow groove 21A extends. Specifically, the side wall 21i is inclined with respect to the surface of the shoulder block 9 in this cross-sectional view. In the present embodiment, the right side wall 21i in FIGS. 10 and 11 has an inclination angle γ4 with respect to the surface of the shoulder block 9 of 45 degrees. The tilt angle γ4 can be set in the range of 5 degrees or more and 60 degrees or less. In FIGS. 10 and 11, the inclination angle of the left side wall 21i with respect to the surface of the shoulder block 9 is −45 degrees in this embodiment, and can be set in the range of −5 degrees or more and −60 degrees or less. That is, the absolute value of the inclination angle γ4 of the side wall 21i with respect to the shoulder block 9 can be set in the range of 5 degrees or more and 60 degrees or less.

The depth DE8 of the shallow groove 21A is 0.05 times or more 0 than the total depth DE9 of the deep portions 21a, 21c, 21e (the sum of the depth DE8 of the shallow groove 21A and the depth DE9 of the sipe main body 21f, 21g, 21h). It can be set in the range of .5 times or less. In the cross-sectional view in the direction orthogonal to the direction in which the shallow groove 21A extends, the maximum width of the shallow groove 21A, that is, the opening of the shallow groove 21A (which is also the opening of the deep portions 21a, 21c, 21e and the shallow portions 21b, 21d). The maximum width W8 can be set in a range of 1.2 times or more and 5 times or less of the width W9 of the sipe main bodies 21f, 21g, 21h.

The straight sipe portion 22a of the composite sipe 22 is provided at a portion corresponding to the tire circumferential direction with respect to the inner portion 8a (having a relatively narrow groove width W5) of the shoulder lateral groove 8. That is, a part of the straight sipe portion 22a overlaps the inner portion 8a in the tire width direction. Further, the corrugated sipe portion 22b of the composite sipe 22 is provided in a portion corresponding to the tire circumferential direction with respect to the outer portion 8b (having a relatively wide groove width W6) of the shoulder lateral groove 8. That is, the corrugated sipe portion 22b overlaps the outer portion 8b in the tire width direction.

In the composite sipe 22, the depths of the deep portions 21a, 21c, 21e of the intermittent sipe 21 and the portions corresponding to the tire circumferential direction (indicated by reference numerals 22c, 22e, 22g, respectively) are determined by the shallow portions 21b, 21d of the intermittent sipe 21 and the tire. It is set shallower than the depth of the portion corresponding to the circumferential direction (indicated by reference numerals 22d and 22f, respectively).

The action and effect of the tire 1 of the present embodiment will be described below.

According to the present embodiment, since the center main groove 5 is formed in a zigzag pattern and the center notch 11 is provided with a step portion 11h, the number of edges can be increased. As a result, the icy and snowy road surface performance, that is, the traction performance and the braking performance on the icy and snowy road surface are improved, and the steering stability performance at the time of turning is also improved. Further, since the two-stage structure is formed by providing the step portion 11h in the center notch 11, the deformation resistance of the center rib 7 to the load on the center notch 11 is increased. That is, the rigidity of the center rib 7 is improved as compared with the case where the center notch 11 is not provided with the step portion 11h. By improving the rigidity of the center rib 7, the steering stability performance when traveling straight is improved.

Further, according to the present embodiment, the edge forming the inflection point and the edge forming the stepped portion 11h of the center notch 11 can be collected in the vicinity of the inflection point of the center main groove 5. As a result, the number of edges that touch the ground at one time can be increased. Therefore, in the vicinity of the inflection point, the road surface can be scratched with more edges at one time, and the ice / snow road surface performance and steering stability performance can be improved.

Further, according to the present embodiment, the ground contact area of the center rib 7 is determined not by the sub-edge 11j but by the main edge 11i located inside the sub-edge 11j in the tire radial direction. That is, by adopting the edge of the two-stage structure, the ratio of the ground contact area to the volume of the center rib 7 can be reduced. By reducing the contact area, the contact pressure of the center rib 7 increases. Further, in the center notch 11, a step portion 11h is provided so that the groove width increases from the bottom wall 11c toward the surface of the tread portion 2. Therefore, the snow pillar formed in the center rib 7 when traveling on a snowy road surface has a shape in which the base end portion is thicker than the tip end portion. As a result, the shear force of the snow column is increased and the snow road surface performance is improved.

Further, according to the present embodiment, the edges can be increased by forming the shoulder main groove 6 in a zigzag pattern. Further, when the center notch 11 touches the ground, the inflection point of the shoulder main groove 6 and the shoulder lateral groove 8 also touch the ground, so that the number of edges that touch the ground at one time can be increased. As a result, the number of edges that come into contact with the ground at one time can be increased, so that the icy / snow road surface performance and the steering stability performance can be improved.

Further, according to the present embodiment, since one center rib unit 7C is provided for each of the two shoulder blocks 9, the edge of the shoulder block 9 can be made larger than the edge of the center rib 7. .. The number of edges of the shoulder block 9 is preferably large because it contributes to steering stability during turning. The rigidity of the center rib 7 is preferably high in order to improve the steering stability performance when traveling straight. Therefore, in order to increase the edge of the shoulder block 9 and maintain the rigidity of the center rib 7 high, it is effective to provide one center rib unit 7C for each of the two shoulder blocks 9. In particular, since one center rib unit 7C is provided for each of the two shoulder blocks 9, the appearance is also well-controlled and aesthetically pleasing.

Further, one center rib unit 7C is provided for each of the two shoulder blocks 9, that is, the zigzag-shaped waviness cycle of the center main groove 5 is twice the zigzag-shaped waviness cycle of the shoulder main groove 6. Is. The center main groove 5 and the shoulder main groove 6 are also flow paths for draining water to the outside. In particular, since the center main groove 5 is provided in the central portion of the tire, higher drainage performance is required than the shoulder main groove 6 provided in the side portion thereof. In the present embodiment, both the center main groove 5 and the shoulder main groove 6 have a zigzag shape, but when the cycle of the zigzag shape swell becomes smaller, the drainage channel becomes more undulating, so that the drainage performance is improved. descend. On the other hand, regarding the zigzag-shaped swell cycle, the center main groove 5 is made larger than the shoulder main groove 6 to reduce the swell of the center main groove 5 and facilitate drainage from the center main groove 5. ..

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention.

1 Tire 2 Tread part 3 Side part 4 Shoulder part 5 Center main groove
5a long groove
5b Short groove 6,6A, 6B Shoulder main groove
6a Long groove
6b Short groove part 7,7A , 7B Center rib 8,8A, 8B Shoulder lateral groove 8a Inner part 8b Outer part 8c Bottom wall 8d Side wall 8e First part 8f Second part 8g Third part 8h Step part 9,9A, 9B Shoulder block 9a Main edge 9b Secondary edge 9c, 9d Region 11 Center notch 11a Main body 11b Tip 11c Bottom wall 11d Side wall 11e First part 11f Second part 11g Third part 11h Stepped part 11i Main edge 11j Secondary edge 12 Side notch 12a Bottom Wall 12b Side wall 12c 1st part 12d 2nd part 12e 3rd part 12f Step part 12g Main edge 12h Secondary edge 13A, 13B, 13C Straight sipe 14A, 14B, 14C Straight sipe 15A, 15B, 15C Wave sipe 21 Intermittent sipe 21A Grooves 21a, 21c, 21e Deep 21b, 21d Shallow 21f, 21g, 21h Sipe body 21i Side wall 21j Bottom wall 21k Side wall 22 Composite sipe 22a Straight sipe 22b Corrugated sipe 22c-22g Part 23 Straight sipe 24

Claims (4)

In the central region of the tread portion in the tire width direction, a center main groove formed so as to extend in a zigzag manner in the tire circumferential direction,
A shoulder main groove formed so as to extend in the tire circumferential direction on the ground contact end side of the tread portion with respect to the center main groove.
A center rib defined by the center main groove and the shoulder main groove and arranged in the central region of the tread portion in the tire width direction,
One end communicates with the center main groove, the other end is terminated in the center rib, and a center notch having a step portion in a portion adjacent to the tread portion is provided .
The shoulder main groove extends in a zigzag direction in the tire circumferential direction.
Arranged at intervals in the tire circumferential direction, extending in the tire width direction, one end communicating with the zigzag inflection point of the shoulder main groove, and the other end ending outside the tire width direction from the ground contact end. With multiple shoulder lateral grooves,
A pneumatic tire in which the center notch and the shoulder lateral groove are provided at the same positions in the tire circumferential direction. The pneumatic tire according to claim 1, wherein one end of the center notch communicates with a zigzag inflection point of the center main groove. The center notch is
A first portion extending from the bottom wall defining the center main groove toward the surface of the tread portion in a cross-sectional view in a direction orthogonal to the direction in which the center notch extends.
In the cross-sectional view in the orthogonal direction, a second portion in which one end is connected to the upper end of the first portion and extends so as to expand the groove width of the center notch, and
In the cross-sectional view in the orthogonal direction, one end is provided with a third portion connected to the other end of the second portion and the other end is connected to the surface of the tread portion.
The stepped portion is a connecting portion between the first portion and the second portion.
The center rib
A main edge connecting the surface of the tread portion and the third portion,
The pneumatic tire according to claim 1 or 2, further comprising a sub-edge to which the first portion and the second portion are connected. A shoulder block defined by the shoulder main groove and two shoulder lateral grooves adjacent to each other in the tire circumferential direction is further provided.
When the center rib is divided into center rib units for each inflection point of the center main groove in the tire circumferential direction, one center rib unit is provided for two shoulder blocks. The pneumatic tire according to any one of claims 1 to 3.

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