JP6916068B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Patent Document 1 discloses a snow tire in which a plurality of corrugated sipes are formed on a shoulder block provided near a ground contact end of a tread portion.

Patent No. 4442709

Conventional pneumatic tires, including the snow tire disclosed in Patent Document 1, have room for improvement from the viewpoint of improving the rigidity of the shoulder block while ensuring steering stability on icy and snowy road surfaces.

An object of the present invention is to improve the rigidity of a shoulder block while ensuring steering stability on an ice-snow road surface in a pneumatic tire.

One aspect of the present invention is a center main groove formed so as to extend in the tire circumferential direction in a central region of the tread portion in the tire width direction, and the tire on the ground contact end side of the tread portion with respect to the center main groove. A shoulder main groove formed so as to extend in the circumferential direction and a tread portion formed in the tire width direction, one end communicating with the shoulder main groove and the other end outside the tire width direction from the ground contact end. A shoulder block defined by a plurality of shoulder lateral grooves arranged at intervals in the tire circumferential direction, the shoulder main groove, and two shoulder lateral grooves adjacent to each other in the tire circumferential direction. The shoulder block is provided with an intermittent sipe, the intermittent sipe extending along the tire width direction, one end communicating with the shoulder main groove, and the other end located in the shoulder block. The first deep portion including the shallow groove and the first sipe main body in which the lower portion and the upper end of the shallow groove communicate with each other and the first deep portion along the tire width direction are different from each other in the tire width direction. A first shallow portion extending at an angle, one end communicating with the first deep portion, the other end located in the shoulder block, and the shallow groove formed by the shallow groove common to the first deep portion. Along the tire width direction, the first shallow portion and the first shallow portion extend at a different angle with respect to the tire width direction, and are offset in the tire circumferential direction with respect to the first deep portion, and one end thereof is said. The other end of the shoulder block communicates with the first shallow portion, and the shallow groove common to the first deep portion and the first shallow portion communicates with the lower portion and the upper end of the shallow groove. Provided is a pneumatic tire comprising a second deep portion comprising a second sipe body to be provided.

The intermittent sipe provided on the shoulder block includes a first deep portion and a second deep portion offset in the tire circumferential direction, and the first deep portion and the second deep portion are different from each other in the tire width direction. It is connected by a first shallow portion that extends at an angle. That is, the first deep portion, the second deep portion, and the first shallow portion are arranged in a polygonal line. The intermittent sipe has these three elements: a first deep part, a second deep part, and a first shallow part, so that the shoulder block has a plurality of edges that are different in position and orientation. As a result, steering stability on icy and snowy road surfaces, especially when turning, is improved.

The first and second deep portions having both the shallow groove and the sipe body are connected by a first shallow portion composed of the shallow groove. In other words, the first deep portion and the second deep portion communicate with each other only on the surface side of the tread portion in the first shallow portion. With this configuration, the decrease in the rigidity of the shoulder block in the portion where the intermittent sipe is provided is suppressed to the minimum. That is, even though the shoulder block is provided with intermittent sipes, the uniformity of the rigidity of the shoulder block and the required rigidity of the shoulder block as a whole are maintained. As a result, the contact pressure acting on the shoulder block can be made uniform, particularly when a load in the front-rear direction in the tire circumferential direction is applied to the shoulder block. By making the ground pressure uniform, uneven wear of the shoulder block can be suppressed or prevented. In addition, ensuring the required rigidity of the shoulder block as a whole also improves steering stability on icy and snowy road surfaces.

As described above, according to the pneumatic tire according to one aspect of the present invention, it is possible to improve the rigidity of the shoulder block while ensuring the steering stability on an ice-snow road surface.

The pair of side walls defining the shallow groove may form a tapered shape in a cross-sectional view in a direction orthogonal to the direction in which the shallow groove extends.

The pneumatic tire further includes an additional sipe provided on the shoulder block adjacent to the intermittent sipe in the tire circumferential direction, and the additional sipe is the first deep portion of the intermittent sipe and the tire circumferential direction. A first portion facing the tire, a second portion facing the first shallow portion of the intermittent sipe in the tire circumferential direction, and a third portion of the intermittent sipe facing the second deep portion in the tire circumferential direction. The first depth of the first and third portions may be shallower than the second depth of the second portion.

By providing an additional sipe in addition to the intermittent sipe, the total length of the edge of the shoulder block is further increased. As a result, steering stability on icy and snowy road surfaces, especially when turning, is improved.

In the tire width direction, the depth of the intermittent sipe is relatively deep in the shoulder block, that is, the portion where the first and second deep portions are provided, the depth of the additional sipe is relatively shallow (of the additional sipe). 1st and 3rd parts). Further, in the shoulder block where the depth of the intermittent sipe is relatively shallow, that is, in the portion where the first shallow portion is provided, the depth of the additional sipe is relatively deep (the second portion of the additional sipe). .. By setting the depth of the intermittent sipe and the additional sipe, the rigidity distribution of the shoulder block in the tire width direction is made uniform. As a result, the contact pressure acting on the shoulder block is made uniform, and the uneven wear resistance of the shoulder block is ensured, particularly when a load in the front-rear direction in the tire circumferential direction is applied.

The intermittent sipe extends along the tire width direction at an angle different from that of the second deep portion in the tire width direction, one end communicating with the second deep portion and the other end being the shoulder block. A second shallow portion located inside and formed by the first deep portion, the first shallow portion, and the shallow groove common to the second deep portion, and the said along the tire width direction. The second shallow portion extends at a different angle with respect to the tire width direction, and is offset in the tire circumferential direction with respect to the first deep portion and the second deep portion, and one end thereof is the second . The shallow groove that communicates with the shallow portion and ends in the shoulder block and is common to the first deep portion, the first shallow portion, the second deep portion, and the second shallow portion. And a third deep portion including a third sipe body with which the lower and upper ends of the shallow groove communicate with each other.

The first deep portion, the second deep portion, and the third deep portion extend at an angle of −20 degrees or more and 20 degrees or less with respect to the tire width direction, and the first shallow portion and the third deep portion. The absolute value of the angle formed by the shallow portion of 2 with respect to the tire width direction may be 2 degrees or more and 45 degrees or less.

The depth of the shallow groove may be 0.05 times or more and 0.5 times or less the depth of the first deep portion, the second deep portion, and the third deep portion.

According to the pneumatic tire of the present invention, it is possible to achieve both steering stability on an ice-snow road surface and improvement in rigidity of the shoulder block.

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'. FIG. 7 is a cross-sectional view taken along the XI-XI line and the XI'-XI' line of FIG. Enlarged view of the alternative center rib. Enlarged view of the alternative center rib.

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 GE 1 and GE 2 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.

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.

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.

A plurality of shoulder lateral grooves 8A and 8B arranged at intervals in the tire circumferential direction in two shoulder regions on both ends of the tread portion 2 in the tire width direction, that is, two regions adjacent to the ground contact ends GE 1 and GE 2, respectively. Are provided respectively.

The shoulder lateral groove 8A extends substantially in the tire width direction, one end communicating with 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.

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 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 GE. 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 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.

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. 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. 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 times or less 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, the angle γ1 formed by the second portion 11f of the side wall 11d with respect to the surface of the center rib 7 is 0 degrees in the cross-sectional view in the direction orthogonal to the direction in which the center notch 11 extends. 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 1 2 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. There is. The angle θ4 of the straight sipe 13A and 13B with respect to the tire radial direction can be set in the range of −85 degrees or more and −30 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 −85 degrees or more and −30 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. Then, the outer portion 8b is inclined right downward, the angle θ7 with respect to the tire width direction of the outer side portion 8 b can be set in the range below -2 degrees -20 degrees.

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 groove 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 21f is provided. In other words, the shallow groove 21f is 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 21f 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 21f are further provided. The upper ends of the sipe main body 21f, 21g, 21h communicate with the lower part of the shallow groove 21f. In this embodiment, the sipe body 21 is a linear sipe.

The shallow portions 21b and 21d are not provided with a sipe main body, and are composed only of the shallow groove 21f. 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 21f 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 21f 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 −45 degrees or more and −2 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 21f 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 21f in the tire radial direction, and a pair of flat side walls 21k.

The side wall 21i defining the shallow groove 21f has a tapered shape in a cross-sectional view in a direction orthogonal to the direction in which the shallow groove 21f 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 −60 degrees or more and −5 degrees or less. That is, the absolute value of the inclination angle γ4 of the side wall 21e 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 21f 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 21f 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 a cross-sectional view in a direction orthogonal to the direction in which the shallow groove 21f extends, the maximum width of the shallow groove 21f, that is, the opening of the shallow groove 21f (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 main features of the tire 1 of the present embodiment include the following.

The intermittent sipe 21 provided on the shoulder block 9 includes deep portions 21a, 21c, 21e offset in the tire circumferential direction, and the deep portions 21a and the deep portions 21c extend at different angles with respect to the tire width direction. It is connected by a shallow portion 21b. Further, the deep portion 21c and the deep portion 21e are connected by a shallow portion 21d extending at an angle different from these in the tire width direction. The intermittent sipe 21 has these six elements, namely the deep portions 21a, 21c, 21e and the shallow portions 21b, 21d, so that the shoulder block 9 has a plurality of edges having different positions and orientations. As a result, steering stability on icy and snowy road surfaces, especially when turning, is improved.

The deep portions 21a, 21c, 21e having both the shallow groove 21e and the sipe main body 21f, 21g, 21h are connected by the shallow portions 21b, 21d composed of only the shallow groove 21e. In other words, the deep portions 21a, 21c, 21e communicate with each other only on the surface side of the shoulder block 9 in the shallow portions 21b, 21d. With this configuration, the decrease in the rigidity of the shoulder block in the portion where the intermittent sipe 21 is provided is suppressed to the minimum. In other words, even though the shoulder block 9 is provided with the intermittent sipe 21, the uniformity of the rigidity of the shoulder block 9 and the required rigidity of the shoulder block 9 as a whole are maintained. As a result, the contact pressure acting on the shoulder block 9 can be made uniform, particularly when a load in the front-rear direction in the tire circumferential direction is applied to the shoulder block 9. By making the ground pressure uniform, uneven wear of the shoulder block 9 can be suppressed or prevented. Further, by ensuring the necessary rigidity of the shoulder block 9 as a whole, good steering stability on an icy and snowy road surface is ensured.

As described above, according to the tire 1 according to the present embodiment, it is possible to improve the rigidity of the shoulder block 9 while ensuring the steering stability on the icy and snowy road surface.

By providing the shoulder block 9 with the composite sipe 22 in addition to the intermittent sipe 21, the total length of the edges of the shoulder block 9 is further increased. As a result, steering stability on icy and snowy road surfaces, especially when turning, is improved.

As described above, in the composite sipe 22, the depths of the deep portions 21a, 21c, 21e of the intermittent sipe 21 and the portions 22c, 22e, 22g corresponding to the tire circumferential direction are set to the depths of the shallow portions 21b, 21d of the intermittent sipe 21 and the tire circumference. part fraction 2 2d corresponding to the direction, is set shallower than the depth of 22 g. That is, in the portion of the intermittent sipe 21 where the deep portions 21a, 21c, 21e are provided, the depth of the composite sipe 22 is relatively shallow, and in the portion where the shallow portions 21b, 21d are provided, the composite sipe 22 The depth is relatively deep. By setting the depths of the intermittent sipe 21 and the composite sipe 22, the rigidity distribution of the shoulder block 9 in the tire width direction is made uniform. As a result, the contact pressure acting on the shoulder block 9 is made uniform, and the uneven wear resistance of the shoulder block 9 is ensured, particularly when a load in the front-rear direction in the tire circumferential direction is applied.

Other features of the tire of this embodiment include:

The tread portion 2 has a combination of a sipe having at least a partially corrugated shape (corrugated sipe 15A, 15B, 15C and a composite sipe 22) and a shoulder lateral groove 8 having a stepped portion 8h. In particular, the shoulder block 9 is provided with a composite sipe 22 having a corrugated sipe portion 22b. Further, the side wall 8d of the shoulder lateral groove 8 defining the shoulder block 9 has a stepped portion 8h on the surface side of the shoulder block 9. With this configuration, the corner portion of the shoulder block 9 extending in the tire width direction has two edges, that is, a main edge 9a and a sub edge 9b. By having the composite sipe 22 having the corrugated sipe portion 22b, the main edge 9a, and the sub edge 9b, the total length of the edges extending along the tire width direction included in the shoulder block 9 becomes long. 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.

The corner portion of the shoulder block 9 extending in the tire width direction is not a single edge but is composed of two steps, that is, a main edge 9a and a sub edge 9b. Due to this two-stage structure, the deformation resistance of the corner portion of the shoulder block 9 against a load is increased. That is, the rigidity of the shoulder block 9 is improved. By improving the rigidity of the shoulder block 9, the steering stability on an ice-snow road surface, particularly the steering stability when turning is improved.

The ground contact area of the shoulder block 9 is determined not by the sub-edge 9b but by the main edge 9a located inside the sub-edge 9b 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 shoulder block 9 can be reduced. By reducing the contact area, the contact pressure of the shoulder block 9 increases, and the ice and snow road surface performance is improved.

Since the side wall 8d of the shoulder lateral groove 8 has a stepped portion 8h on the surface side of the shoulder block 9, the snow pillar formed in the shoulder lateral groove 8 on the 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.

Referring to FIG. 7, the shoulder block 9 is relatively relative to the inner portion 8a of the shoulder lateral groove 8 (having a relatively narrow width W5) in the region corresponding to the tire width direction (indicated by reference numeral 9c in FIG. 7). It has a wide width W10. In this region 9c, the rigidity of the shoulder block 9 is relatively high, and the surface rigidity of the shoulder block 9 is relatively low. Here, the "rigidity of the shoulder block" means not only the surface of the shoulder block 9 but also the deformation resistance as a volume body. Further, the “surface rigidity of the shoulder block” means the deformation resistance of the surface of the shoulder block 9. In the inner portion 8a of the shoulder lateral groove 8 in which the rigidity of the shoulder block 9 itself and the surface rigidity have such a relationship, the effect of maintaining the surface rigidity of the shoulder block 9 is higher than the effect of maintaining the rigidity of the shoulder block 9, which is a composite. The straight sipe portion 22a of the sipe 22 is arranged.

The shoulder block 9 has a relatively narrow width W11 in a region (indicated by reference numeral 9d in FIG. 7) corresponding to the outer portion 8b (having a relatively wide width W6) of the shoulder lateral groove 8 in the tire width direction. In this region 9d, the rigidity of the shoulder block 9 is relatively low, and the surface rigidity of the shoulder block 9 is relatively high. In the outer portion 8b of the shoulder lateral groove 8 in which the rigidity of the shoulder block 9 itself and the surface rigidity have such a relationship, the effect of maintaining the rigidity of the shoulder block 9 is higher than the effect of maintaining the surface rigidity of the shoulder block 9, which is a composite. The waveform sipe portion 22 b of the sipe 22 is arranged.

As described above, in the inner portion 8a of the shoulder lateral groove 8 having a relatively narrow width W5 (the shoulder block 9 has a relatively wide width W10), the straight sipe portion 22a of the composite sipe 22 is arranged on the shoulder block 9. However, in the outer portion 8b of the shoulder lateral groove 8 having a relatively wide width W6 (the shoulder block 9 has a relatively narrow width W11), the corrugated sipe portion 22b of the composite sipe 22 is arranged in the shoulder block 9. .. With this configuration, the required surface rigidity can be obtained on the CL side (shoulder main groove 6 side) in the center of the tire width direction of the shoulder block 9, so that good ground contact of the shoulder block 9 and good icy and snow road surface performance are ensured. NS. Further, since the required block rigidity can be obtained for the entire shoulder block 9 including the grounding end GE side of the shoulder block 9, good steering stability on an icy and snowy road surface is ensured.

The center rib 7 is provided with a center notch 11 and straight sipes 13A and 13B at a portion facing the center notch 11 in the tire width direction. Further, a side notch 12 and straight sipes 14A and 14B at a portion facing the side notch 12 in the tire width direction are provided on the center rib 7. By having the center notch 11, the side notch 12, and the straight sipe 13A, 13B, 14A, 14B, the center rib 7 is provided with a large number of edges. 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.

The portion of the center rib 7 with respect to the center notch 11 and the tire width direction has a narrower dimension in the tire width direction, that is, a width than the other portions. The required rigidity of the center rib 7 is maintained by providing the straight sipe 13A and 13B in the narrow portion instead of another notch. Further, the width of the side notch 12 of the center rib 7 and the portion with respect to the tire width direction is narrow. The required rigidity of the center rib 7 is maintained by providing straight sipe 14A and 14B in the narrow portion instead of another notch. As a result, good steering stability on icy and snowy road surfaces can be obtained. Further, by providing straight sipes 13A, 13B, 14A, 14B instead of notches in the narrow portion of the center rib 7 facing the center notch 11 and the side notch 12 in the tire width direction, the rigidity distribution of the center rib 7 is uniform. Has been made. As a result, the uneven wear resistance of the center rib 7 is ensured.

The angles θ4 of the straight lines 13A and 13B with respect to the tire circumferential direction have different positive and negative signs from the angles θ1 and θ2 of the center notch 11 with respect to the tire circumferential direction. 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 an upwardly convex polygonal line in FIG. Further, the angle θ5 of the straight lines 14A and 14B with respect to the tire circumferential direction has a positive / negative sign different from the angle θ3 of the side notch 12 with respect to the tire circumferential direction. 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 downwardly convex polygonal line in FIG. The rigid arrangement of the center notch 11 and the straight sipe 13A and 13B in a polygonal line, and the side notch 12 and the linear sipe 14A and 14B in a polygonal arrangement improves the rigidity of the center rib 7 in the tire circumferential direction. Here, the "rigidity of the rib" means not only the surface of the rib but also the deformation resistance as a volume body. By improving the rigidity of the center rib 7 in the tire circumferential direction, the steering stability on an ice-snow road surface is improved.

Further, the total length of the edge of the center rib 7 becomes long due to the polygonal arrangement of the center notch 11 and the straight sipe 13A and 13B and the polygonal arrangement of the side notch 12 and the straight sipe 14A and 14B. As a result, the ice and snow road surface performance is improved.

The polygonal line formed by 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 is convex upward in FIG. On the other hand, the polygonal line formed by 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 is convex downward in FIG. Since the former convex direction and the latter convex direction are opposite to each other, the rigidity of the center rib 7 is increased against a load acting on the center rib 7 from any direction in the tire circumferential direction. improves. As a result, steering stability on icy and snowy road surfaces is further improved.

The straight sipe 13A and 13B, which are examples of sipe having no inflection point, are provided so as to face the center notch 11 in the tire width direction. Further, the straight sipe 14A and 14B, which are similarly examples of the sipe having no inflection point, are provided so as to face the side notch 12 in the tire width direction. Here, the "inflection point" of the sipe means a point in which the direction in which the sipe extends changes in the tire radial direction. For example, if some part of the sipe extends in one direction around the tire and the part of the sipe adjacent to this part extends in the opposite direction of the tire circumference, the connection between these two parts is an inflection point. Is.

In general, when comparing a rib provided with a sipe having no inflection point and a rib provided with a sipe having an inflection point (for example, a corrugated sipe), the surface rigidity of the former rib is higher than the surface rigidity of the latter rib. Is also expensive. Here, "the surface rigidity of the rib" means the deformation resistance of the surface of the rib. A straight sipe that does not have an inflection point that is advantageous in terms of surface rigidity, not a sipe that has an inflection point in a portion that faces the center notch 11 in the tire width direction and a portion that faces the side notch 12 in the tire width direction. 13A, 13B, 14A, 14B are provided. This configuration ensures good ground contact of these parts and good icy and snow road surface performance.

As shown in FIG. 12, instead of the straight sipe 13A, 13B, 14A, 14B, the arc sipe 113A, 113B, 114A, 114B, which is another example of the sipe having no inflection point, is provided on the center rib 7. You may.

As shown in FIG. 13, corrugated sipes 213A, 213B, 214A, 214B may be provided on the center rib 7 instead of the straight sipes 13A, 13B, 14A, 14B. Even in this case, the required rigidity of the center rib is maintained by providing a sipe instead of another notch in the narrow portion facing the center notch 11 and the side notch 12 in the tire width direction, and the center rib 7 The rigidity distribution can be made uniform.

1 Tire 2 Tread part 3 Side part 4 Shoulder part 5 Center main groove 6,6A, 6B Shoulder main groove 7,7A, 7B Center rib 8,8A, 8B Shoulder lateral groove 8a Inner part 8b Outer part 8c Bottom wall 8d Side wall 8e No. 1st part 8f 2nd part 8g 3rd part 8h Stepped part 9,9A, 9B Shoulder block 9a Main edge 9b Sub-edge 9c, 9d Area 11 Center notch 11a Main body 11b Tip 11c Bottom wall 11d Side wall 11e 1st part 11f 1st 2 part 11g 3rd part 11h Step part 11i Main edge 11j Sub 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 Sub edge 13A, 13B, 13C Straight line Sipe 14A, 14B, 14C Straight sipe 15A, 15B, 15C Wave sipe 21 Intermittent sipe 21a, 21c, 21e Deep 21b, 21d Shallow 21f Shallow groove 21f, 21g, 21h Sipe body 21i Side wall 21j Bottom wall 21k Side wall 22 Straight sipe part 22b Wave sipe part 22c-22g Part 23 Straight sipe 24 Continuous protrusions 113A, 113B, 114A, 114B Arc sipe 213A, 213B, 214A, 214B Wave sipe

Claims (6)

A center main groove formed so as to extend in the tire circumferential direction in the central region of the tread portion in the tire width 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.
It is formed in the tread portion, extends in the tire width direction, one end communicates with the shoulder main groove, and the other end ends outside the tire width direction from the ground contact end, and is arranged at intervals in the tire circumferential direction. Multiple shoulder treads and
A shoulder block defined by the shoulder main groove and two shoulder lateral grooves adjacent to each other in the tire circumferential direction.
It is equipped with an intermittent sipe provided on the shoulder block.
The intermittent sipe
A first sipe that extends along the tire width direction, one end communicating with the shoulder main groove, the other end located within the shoulder block, and the shallow groove communicating with the lower and upper ends of the shallow groove. The first deep part with the body and
Along the tire width direction, the first deep portion extends at a different angle from the tire width direction, one end communicates with the first deep portion, and the other end is located in the shoulder block. A first shallow portion formed by the shallow groove common to the first deep portion, and
Along the tire width direction, the first shallow portion and the first shallow portion extend at a different angle with respect to the tire width direction, and are offset in the tire circumferential direction with respect to the first deep portion, and one end thereof is said. The other end of the shoulder block communicates with the first shallow portion, and the shallow groove common to the first deep portion and the first shallow portion communicates with the lower portion and the upper end of the shallow groove. Pneumatic tire with a second depth with a second sipe body. The pneumatic tire according to claim 1, wherein the pair of side walls defining the shallow groove form a tapered shape in a cross-sectional view in a direction orthogonal to the direction in which the shallow groove extends. The shoulder block is further provided with an additional sipe provided adjacent to the intermittent sipe in the tire circumferential direction.
The additional sipe includes a first portion of the intermittent sipe facing the first deep portion in the tire circumferential direction, a first shallow portion of the intermittent sipe facing the tire circumferential direction, and a second portion facing the tire circumferential direction. The second deep portion of the intermittent sipe and a third portion facing the tire circumferential direction are provided.
The pneumatic tire according to claim 1 or 2, wherein the first depth of the first and third portions is shallower than the second depth of the second portion. The intermittent sipe
Along the tire width direction, the second deep portion extends at a different angle from the tire width direction, one end communicates with the second deep portion, and the other end is located in the shoulder block. And the first deep portion, the first shallow portion, and the second shallow portion formed by the shallow groove common to the second deep portion, and
Along the tire width direction, the second shallow portion extends at a different angle with respect to the tire width direction, and is offset in the tire circumferential direction with respect to the first deep portion and the second deep portion. One end communicates with the second shallow portion and the other end ends in the shoulder block, and the first deep portion, the first shallow portion, the second deep portion, and the second deep portion. 6. Pneumatic tires. The first deep portion, the second deep portion, and the third deep portion extend at an angle of −20 degrees or more and 20 degrees or less with respect to the tire width direction.
The pneumatic tire according to claim 4, wherein the absolute value of the angle formed by the first shallow portion and the second shallow portion with respect to the tire width direction is 2 degrees or more and 45 degrees or less. Claim 4 or claim 5 that the depth of the shallow groove is 0.05 times or more and 0.5 times or less the depth of the first deep portion, the second deep portion, and the third deep portion. Pneumatic tires described in.

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