WO2018008732A1

WO2018008732A1 - Tire

Info

Publication number: WO2018008732A1
Application number: PCT/JP2017/024870
Authority: WO
Inventors: 耕平長谷川
Original assignee: 株式会社ブリヂストン
Priority date: 2016-07-06
Filing date: 2017-07-06
Publication date: 2018-01-11
Also published as: JP2018002055A

Abstract

Provided is a tire having a main groove that is disposed in a tread section so as to extend in a zigzag in the tire circumferential direction, wherein: the main groove is configured to have a main groove portion which connects between bent parts adjacent to each other in the tire circumferential direction, and one side of the main groove portion has a width greater than the other side thereof; and the ratio of the width of main groove portion on the other side with respect to the width of the main groove portion on the one side is set to fall within a range of 0.5-0.75.

Description

tire

The present invention relates to a tire, and more particularly, to a tire capable of improving stone biting performance while preventing uneven wear in a tread portion.

Conventionally, in a tire, it is known that traction performance and braking performance are improved by forming a main groove extending in the tire circumferential direction in a zigzag shape.

JP 2001-315507 A

However, when the main groove is formed in a zigzag shape, there is a problem that stone biting is likely to occur at the bent portion as compared with the straight portion. For example, as shown in FIG. 10 (a), a stone G caught in a straight portion of a groove is sandwiched between opposing groove walls m1; m2, and supported at two points as indicated by arrows in the figure. Therefore, it is easy to move along the extending direction of the groove M, and the stone is easily removed by contact with the road surface during traveling. On the other hand, the bent portion as shown in FIG. 10B is sandwiched between the groove wall m1; m1 bent in a concave shape and the corner portion V formed by the groove wall m2; m2 bent in a convex shape. Since it is supported at three points as indicated by the middle arrow, the holding force is large and the stones are not easily removed from the groove as compared with the above-described two-point support. As a measure to reduce stone biting, for example, it is conceivable to reduce the groove depth of the main groove, widen the groove width, or set the angle of the groove wall to be large. There is a problem that uneven wear tends to occur.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a tire that can improve stone-resisting performance in a tread portion of the tire.

As a configuration of a tire for solving the above-described problem, a tire having a main groove extending in a zigzag shape in a tire circumferential direction in a tread portion, and connecting bent portions adjacent to each other in the tire circumferential direction of the main groove. One groove width of the main groove portion is set wider than the other groove width, and the groove width ratio of the other main groove portion to the groove width of the one main groove portion is 0.5 to 0.75. It was set as the structure set to this range.
According to this configuration, the stone biting performance can be improved. That is, since the groove wall of the other main groove portion facing one main groove portion having a wider groove width in the bent portion approaches one main groove portion, the main stone biting holding force is changed from three-point support to two-point support, Since the stone that has been bitten can be easily removed from the groove, the stone biting performance can be improved.

It is a top view which shows one Embodiment of a tread pattern. It is an enlarged view of a tread part. It is a figure which shows the relationship between the

linear parts

11 and 12 in a shoulder groove. It is the elements on larger scale of a shoulder groove. 5A and 5B are cross-sectional views of the shoulder groove. FIG. 5 is a view as seen from the direction of the arrow uu in FIG. 4. It is the table | surface which put together the test conditions for evaluating stone biting performance, and an evaluation result. It is the figure which put together the suitable range of the angle and area in the triangle A, the angle b1 of the triangle B, and the area Sb. FIG. 9A to FIG. 9C are diagrams showing a mechanism for removing stones. 10 (a) and 10 (b) are diagrams showing a conventional stone biting state.

Hereinafter, the present invention will be described in detail through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included in the invention. It is not necessarily essential to the solution, but includes a configuration that is selectively adopted.

FIG. 1 is a plan view showing a tread pattern according to the present embodiment. FIG. 2 is an enlarged view of the tread portion. Note that the tread pattern of this embodiment does not change the grounding pattern even if the relationship between the vehicle body side and the vehicle body outside is changed when assembling the tire (the setting of the rotation direction is not necessary when the tire is mounted on the vehicle). Designed to be)

As shown in FIGS. 1 and 2, the tread portion 1 includes a plurality of main grooves 2 to 4 extending in the tire circumferential direction, and a width direction groove 5 and a narrow groove 6 extending in the tire width direction. The main grooves 2 to 4 are so-called main grooves, and have a tread wear indicator (not shown) at the groove bottom.
The

main grooves

2 and 3 are respectively provided on the outer side in the tire width direction, extend in a zigzag shape along the tire circumferential direction, and divide the tread portion 1 into left and right

shoulder land portions

30A and 30B and a center land portion 31. The center land portion 31 is provided between the

main grooves

2 and 3, and is further divided into left and right

center land portions

31A and 31B by a main groove 4 extending in a zigzag shape along the tire circumferential direction.

The term “zigzag extending in the tire circumferential direction” means that the straight portion of the groove inclined with respect to the tire circumferential direction extends in the tire circumferential direction while turning back so that the inclination directions are alternate. In addition, although the linear part of a groove | channel is linear in many cases, it does not necessarily need to be limited to linear form and includes what is formed in curved shape.

The center land portions 31 </ b> A and 31 </ b> B are periodically provided with a width direction groove 5 extending in the tire width direction and communicating with the

main grooves

2 and 4 and the

main grooves

3 and 4 along the tire circumferential direction. Thus, the

center land portions

31A and 31B are formed by a plurality of block rows that are continuous in the tire circumferential direction. That is, a so-called block pattern is formed on the tread portion 1.
The left and right

shoulder land portions

30A and 30B are periodically provided with narrow grooves 6 extending in the tire width direction along the tire circumferential direction.

Hereinafter, the configuration of each of the grooves 2 to 6 will be described. In the following description, the

main grooves

2 and 3 are referred to as shoulder grooves, the main groove 4 is referred to as a center groove, and the width direction groove 5 is referred to as a lug groove. In addition, the groove width is a length dimension that opens to the ground contact surface 1a when it is new, measured in a direction orthogonal to the extending direction of the groove.
The center groove 4 is provided in the center in the tire width direction (hereinafter referred to as a tire center) CL. The center groove 4 includes a straight portion 7 and a straight portion 8 whose extending directions are inclined in opposite directions with respect to the tire circumferential direction, and a bent portion 15 in which the extending direction of the straight portion 7 and the straight portion 8 changes. The The

straight portions

7 and 8 constituting the center groove 4 have the same groove widths w7 and w8, groove lengths L7 and L8, and angles extending with respect to the tire circumferential direction (hereinafter referred to as groove swing angles) α7 and α8. Is set. By forming such a center groove 4, left and right symmetry is obtained in the tread pattern when the main groove is formed on the tire center CL in a zigzag shape.

The groove widths w7 and w8 of the

straight portions

7 and 8 are set in a range of 15 mm to 25 mm, for example. The groove lengths L7 and L8 are defined by the groove center lines 7z and 8z as shown in FIG. Further, the groove length L7 is the distance from one intersection point where the groove center line 7z and the

groove center lines

8z, 8z of the adjacent

straight portions

8, 8 intersect, and the groove length L8 is the groove length L8. This is the distance from one intersection to the other intersection where the center line 8z and the

groove center lines

7, 7 of the adjacent

straight portions

7, 7 intersect. Further, the groove swing angles α7 and α8 refer to the acute angle side among the angles at which the groove center lines 7z and 8z intersect the tire circumferential direction. Further, the groove swing width fw4 of the center groove 4 is set in a range of 5 mm to 20 mm. The groove swing width fw4 refers to the length in the tire width direction from one intersection where the groove center lines 7z, 8z of the adjacent

straight portions

7, 8 intersect each other to the other intersection. By setting the groove swing width fw4 within this range, it is possible to prevent a reduction in braking force and occurrence of uneven wear.

The center groove 4 includes a plurality of protrusions 19 that protrude toward the tire surface side on the groove bottom 4c. The protrusions 19 are formed intermittently at predetermined intervals along the extending direction of the center groove 4. The protrusion 19 is formed such that the height from the groove bottom of the center groove 4 is in the range of 10% to 30% of the groove depth of the center groove 4, for example, a stone or the like trying to fit into the center groove 4 Prevent biting of foreign objects.

The

shoulder grooves

2 and 3 are respectively provided at positions that are symmetrical from the outside in the tire width direction. In the present embodiment, the

shoulder grooves

2 and 3 have the same configuration. The shoulder groove 3 is formed so that the shape of the shoulder groove 2 is reversed, and the symmetry of the

shoulder grooves

2 and 3 in the ground contact pattern is set. In the following description, the configuration of the groove will be described using the shoulder groove 2.

The shoulder groove 2 is composed of

straight portions

11 and 12 whose extending direction is inclined in the opposite direction with respect to the tire circumferential direction, and a bent portion 14, and is formed to extend in a zigzag shape in the tire circumferential direction.
The

straight portions

11 and 12 in the shoulder groove 2 are set so that the groove width w12 of the other straight portion 12 is wider than the groove width w11 of the one straight portion 11. Specifically, the groove width ratio (groove width w11 / groove width w12) between the groove width w11 of the linear portion 11 and the groove width w12 of the linear portion 12 is set in the range of 0.5 to 0.75. If the groove width ratio is smaller than 0.5, the contact pressure of the portion where the straight portion 11 and the stone are in contact increases and the stone is in a three-point support state. If it is greater than 0.75, the straight portion 12 and the stone As a result, the contact pressure at the point where the stones come into contact increases, and the stone is in a three-point support state, so that the stone biting performance cannot be improved.
The groove widths w11 and w12 are set in the range of 10 mm to 25 mm, respectively.

By setting the groove width ratio in this way, for example, the stone biting performance at the bent portion 14 can be improved as compared with the case where the groove width ratio is the same as that of the center groove 4.

The groove lengths L11, L12 of the

straight portions

11, 12 are the groove swing angles α11, α12 intersecting the tire circumferential direction and the length in the tire width direction between the adjacent

bent portions

14, 14. Set by fw2. The groove swing angles α11 and α12 are set in the range of 25 ° to 45 °, and the groove swing width fw2 is set in the range of 7 mm to 30 mm.

The groove length L11 is a distance from one intersection point where the groove center line 11z of the straight line portion 11 and the

groove center lines

12z, 12z of the

straight line portions

12 and 12 adjacent to the straight line portion 11 to the other intersection point, the groove length The length L12 is a distance from one intersection to the other intersection where the groove center line 12z of the straight portion 12 and the

groove center lines

11z and 11z of the straight portion 11 adjacent to the straight portion 12 intersect. Further, the groove swing angles α11 and α12 refer to the acute angle side of the angle at which the groove center line 11z of the straight portion 11 and the groove center line 12z of the straight portion 12 intersect with the tire circumferential direction. Further, the groove swing width fw2 is the length in the tire width direction from one intersection point where the

groove center lines

11z, 12z of the adjacent

straight portions

11, 12 intersect to the other intersection point.

Further, for the groove lengths L11 and L12, the groove swing angles α11 and 12 and the groove swing width fw2 are set within the above range so that the groove length L12 is 85% to 115% with respect to the groove length L11. Set it. Thereby, the edge effect in the shoulder groove 2 can be obtained effectively, and the uneven wear resistance performance can be improved while ensuring the driving force and the braking force.

The lug groove 5 is formed so as to communicate the bent portion 14 located on the tire center CL side of the shoulder groove 2 and the bent portion 15 located on the shoulder groove 2 side of the center groove 4. The lug groove 5 extends in the tire width direction toward the center groove 4 at an angle larger than the groove swing angle α12 of the linear portion 12, and the extension direction is changed in the tire circumferential direction opposite to the center groove 4 on the way. It is formed so as to communicate.
The lug groove 5 is formed with a groove width w5 in the range of 5 mm to 10 mm. Further, the lug groove 5 is set such that the groove depth h5 from the tire surface is 0.2 to 0.6 times (h5 / h2) the groove depth h2 of the shoulder groove 2.

By providing the lug grooves 5 in this manner, the corners facing the straight portions 12 having a wide groove width can be provided in the block 20 defined by the

lug grooves

5 and 5 adjacent in the tire circumferential direction. Then, when the block 20 swings due to contact with the road surface, the stones biting into the bent portion 14 are pushed out to the straight portion 12 by the corner portion and are easily discharged from the shoulder groove 2.
In addition, the ground contact area of the block 20 can be increased by connecting the bent portion 15 of the adjacent center groove 4 and the bent portion 14 of the shoulder groove 2 by the lug groove 5, so that the block rigidity of the block 20 is increased. Can do.

Further, by setting the groove swing angles α11 and α12 of the

straight portions

11 and 12 constituting the shoulder groove 2 in the range of 25 ° to 45 ° and the groove swing width fw2 in the range of 7 mm to 30 mm, the block 20 is defined. Since the pitch length in the tire circumferential direction between the formed

lug grooves

5 and 5 is optimized, a decrease in braking force and an occurrence of uneven wear due to an excessive increase in the edge component while preventing a decrease in the rigidity of the block 20 Can be prevented. The groove swing width fw2 of the shoulder groove 2 is desirably 1.1 to 3.0 times the groove swing width fw4 of the center groove 4. When the groove swing width fw4 is smaller than 1.1 times, the traction performance is lowered, and when it is larger than 3.0 times, the partial wear property is deteriorated.

FIG. 3 is a diagram illustrating the relationship between the

straight portions

11 and 12 in the shoulder groove 2. As shown in the figure, the straight portion 11 and the straight portion 12 in the shoulder groove 2 are preferably formed so as to satisfy the following relationship.
The stone bites at the

bent portions

14 and 14 include the

groove walls

12a and 12b that define the straight portion 12 having a wide groove width, and the groove wall 11a or the groove wall 11b of the straight portion 11 that faces the extending direction of the straight portion 12. It is caused by being sandwiched between the three surfaces. Therefore, the triangle A and the triangle B assuming the state where the stone bites are generated in the

bent portions

14 and 14 are set to the

bent portions

14 and 14 positioned at both ends of the linear portion 12.

Hereinafter, a method for setting the triangle A and the triangle B will be described.
First, a center line 12z is set in the straight line portion 12. Next, the intersection with the groove wall 11a of the linear part 11 where the center line 12z intersects is set as A1. Next, the groove wall 11a where the intersection A1 is set is extended, and the intersection with the groove wall 12a of the linear portion 12 is set as A2. Next, the intersection of the groove wall 11b of the straight part 11 and the groove wall 12b of the straight part 12 is set as a point A3. And the triangle A is set to one bending part 14 by connecting the intersections A1, A2, and A3 with straight lines. The intersections A1, A2, and A3 may be referred to as vertices A1, A2, and A3.
Next, a triangle B is set at the other bent portion 14. The intersection of the groove walls 11b of the straight line part 11 where the center line 12z intersects is set as B1. Next, the groove wall 11a and the groove wall 12a of the linear part 12 are extended, and the intersection where these intersect is set as B2. Next, the intersection of the groove wall 12b and the groove wall 5b of the lug groove 5 is set as B3. And the triangle B is set to the other bending part 14 by connecting intersection B1, B2, B3 with a straight line. The intersection points B1, B2, and B3 may be referred to as vertices B1, B2, and B3.

As described above, in the triangle A and the triangle B set in the shoulder groove 2, the angle a1 of the vertex A1 of the triangle A is set in the range of 90 ° to 130 °, and the angle b1 of the vertex B1 is set in the range of 65 ° to 105 °. It is preferable. More preferably, the angle a1 of the vertex A1 of the triangle A is set to be larger than the angle b1 of the vertex B1 of the triangle B while satisfying the numerical range. In this way, by setting the vertices A1 and B1 of the triangles A and B, the stone biting performance can be improved.

Furthermore, the angle at which the straight portion 11 and the straight portion 12 intersect, the groove width w11, and the groove so that the area Sa of the triangle A is in the range of 60 mm ² to 90 mm ² and the area Sb of the triangle B is in the range of 85 mm ² to 115 mm ^2. It is preferable to set the width w12. Further, by increasing the area of the triangle B positioned on the center side than the triangle A positioned on the shoulder side, the bite stones can be easily removed from the shoulder groove 2, and the stone resistance in the region where the contact pressure is high in the tire. The biting performance can be improved.

The groove width w11 of the straight portion 11 and the groove width w12 of the straight portion 12 in the shoulder groove 2 or the groove swing angle α12 of the straight portion 11 relative to the straight portion 12 and the straight portion 12 of the straight portion 12 with respect to the straight portion 11 are satisfied. By setting the mutual relationship between the groove swing angle α11 and the position of the lug groove 5 opening in the shoulder groove 2 and the groove width w5, the stones caught in the bent portion 14 are effectively removed during traveling. It becomes possible.

FIG. 4 is a partially enlarged view of the bent portion 14 in the shoulder groove 20. 5A is a cross-sectional view of the straight portion 11 in the shoulder groove 2 and FIG. 5B is a cross-sectional view of the straight portion 12 in the shoulder groove 2.
In addition, predetermined inclination angles (hereinafter referred to as groove wall angles) β and γ are set in the

groove walls

2 a and 2 b forming the shoulder groove 2. The groove wall angles β and γ are the acute angles of the angles of the

groove walls

2a and 2b with respect to the normal direction of the ground contact surface 1a on the tread surface. A groove wall angle β is set to a predetermined angle in the groove wall 2a located on the outer side in the tire width direction. The groove wall angle β12 of the straight portion 12 is preferably set in the range of 8 ° to 15 °, and the groove wall angle β11 of the straight portion 11 is preferably set in the range of 8 ° to 15 °.

Further, the groove wall angle γ is set to be different depending on the position on the groove wall 2b located on the tire center CL side. Specifically, in the groove wall 2b, different groove wall angles γ11 and γ12 are set for the

straight portions

11 and 12, respectively. The groove wall angles γ11 and γ12 are set as follows. In the block 20, a point X is set at a corner portion protruding to the shoulder land portion 30 </ b> A side, that is, a corner portion corresponding to the bent portion 14 located on the outer side in the tire width direction of the shoulder groove 2 (the intersection point X is a figure). 3). Next, among the distance in the width direction from the point X to the boundary JA and JB between the pair of

lug grooves

5A and 5B that define the block 20 and the shoulder groove 2, the groove wall on the side where the distance in the width direction is long The groove wall angle is set smaller than the groove wall on the short side in the width direction.
The groove wall angle γ12 of the straight portion 12 is set to 20 ° to 30 °, the groove wall angle γ11 of the straight portion 11 is set to a range of 8 ° to 15 °, and γ12 is set to be twice or more of γ11. Thus, in the shoulder groove 2, the groove wall angle (γ12) on the inner side in the width direction of the straight portion 12 is set to be larger than the groove wall angle (γ11) on the outer side in the width direction and the groove wall angles (β11, β12) of the straight portion 11. By setting it large, and preferably by setting it twice or more, stones in the shoulder groove 2 can be easily removed, and the stone biting performance is improved. More preferably, by making β11 larger than γ11 and γ12 larger than β12, it is possible to optimize the reaction force against the stone, and it is possible to further improve the stone biting performance.
In the present embodiment, the boundary JA is a position where the extension of the groove wall 11b forming the straight portion 11 and the extension of the groove wall 5a of the lug groove 5A intersect (intersection B in FIG. 3), the boundary JB. Is the position where the extension of the groove wall 12b forming the straight portion 12 and the extension of the groove wall 5b of the lug groove 5B intersect on the tread surface.

As shown in FIG. 4, in this embodiment, the width direction distance k2 from the point X to the boundary JA set in the block 20 is longer than the width direction distance k1 to the boundary JB, so the point X reaches the boundary JA. An angle larger than the groove wall angle γ11 of the groove wall 11b extending from the point X to the boundary JB is set to the groove wall angle γ12 of the groove wall 12b. In this case, the groove wall angle γ11 of the groove wall 11b is in the range of 8 ° to 15 °, and the groove wall angle γ12 of the groove wall 12b is in the range of 20 ° to 30 °, so that the groove wall angle ratio (γ12 / γ11) is Set to a range of 2.0 times or more. Thus, by setting different groove wall angles γ11 and γ12 to the groove wall 2b of the shoulder groove 2 that defines the block 20, the stone biting performance on the shoulder portion side of the center land portion 31A can be improved.

As shown in FIGS. 4 and 6, the block 20 is preferably provided with a groove 22 having one end opening in the shoulder groove 2 and the other end terminating in the block 20. The groove 22 opens at the center in the extending direction of the linear portion 11 constituting the shoulder groove 2 and extends along the lug groove 5.
As shown in FIG. 6, the groove 22 is formed, for example, in the range where the groove width w22 is 1 mm to 3 mm and the groove depth h22 is 2 mm to 5 mm. Preferably, in the groove 22, the relationship between the groove width w22 and the groove depth h22 is set such that the dimension of the groove depth h22 is larger than the dimension of the groove width w22 within the above range.

Thus, by providing the groove 20 that opens to the shoulder groove 2 in the block 20, it is possible to change the movable range of the block 20 during traveling. That is, since a new tire has a deep groove depth, it is difficult for the stone caught in the bent portion 14 to come off. Therefore, by providing the groove 22 having a groove depth that does not affect the rigidity of the block 20, the vicinity of the surface of the block 20 can be easily moved by friction with the road surface. Thereby, the stone bitten by the bent portion 14 on the tire center CL side of the shoulder groove 2 is such that the edge portion of the block 20 (the boundary JB portion shown in the above description) is indicated by an arrow x in FIG. By greatly moving in the direction of the wide straight portion 12 of the shoulder groove 2, the shoulder groove 2 is pushed out in the direction of the straight portion 12 and excluded from the shoulder groove 2. Therefore, the stone biting performance can be further improved.

The narrow groove 6 is provided corresponding to the groove 22 provided in the block 20. The narrow groove 6 is formed so that one end opens into the main groove 2 and the other end terminates in the shoulder land portion 30A. Specifically, the narrow groove 6 opens into the shoulder groove 2 so that one end side extends the groove 22, and extends in a bow shape so that the inclination angle gradually decreases with respect to the tire width direction.
The narrow groove 6 is formed, for example, in the range where the groove width w6 is 1 mm to 3 mm and the groove depth h6 is 2 mm to 5 mm.

[Example]
FIG. 7 is a table summarizing test conditions and evaluation results for evaluating the stone biting performance. In the performance evaluation test, tires corresponding to the conditions shown in the same table were prepared and evaluated by counting the number of stones caught in the actual tire grooves after traveling 10,000 km on the gravel road test road at 60 km / h. did. The tire size of the test tire is 13R22.5.
The case where the areas Sa and Sb of the triangles A and B shown in FIG. 3 are constant and the angles a1 and b1 of the triangles A and B are changed to evaluate the stone resistance performance will be described. In addition, relative evaluation was performed on the basis of the conventional example. That is, when the reference index is 100, the performance is better as the index is larger than 100, and the performance is lowered as the standard index is smaller than 100. When the areas Sa and Sb of the triangles A and B are constant and the angles a1 and b1 are changed, as shown in the first to fifth embodiments, the angle a1 is in the range of 90 ° to 130 °, and the angle b1 is 65. It can be seen that the stone biting performance is excellent when the angle is in the range of ° to 105 °. For example, as shown in Comparative Examples 1 and 2, it can be seen that as the angle a1 is smaller than 90 ° and the angle b1 is smaller than 65 °, the stone biting performance decreases. Further, as shown in Comparative Examples 3 and 4, it can be seen that the stone-resisting performance decreases as the angle a1 is larger than 130 ° and the angle b1 is larger than 105 °.
Further, when the angles a1 and b1 are constant and the areas Sa and Sb are changed, the area Sa is in the range of 60 mm ² to 90 mm ² and the area Sb is 85 mm ² to 85 mm as shown in the sixth to ninth embodiments. It turns out that it is excellent in stone biting performance by setting it as the range of 110 mm < ² >.
For example, as shown in Comparative Example 5, it can be seen that when the area Sa is smaller than 60 mm ² and the area Sb is smaller than 85 mm ² , the stone biting performance is lowered. In addition, as shown in Comparative Example 6, it can be seen that when the area Sa is larger than 90 mm ² and the area Sb is larger than 115 mm ² , the stone biting performance is lowered.

FIG. 8 is a diagram summarizing the setting ranges of the angle a1 and the area Sa of the triangle A and the angle b1 and the area Sb of the triangle B. As shown in the figure, for the triangle A, the groove widths w11 and w12 and the groove swing are set such that the angle a1 and the area Sa are included in the rectangular area Ea, and the triangle B is included in the rectangular area Eb. Angles α11 and α12 and groove lengths L11 and L12 may be set.

FIG. 9A to FIG. 9C are diagrams showing a mechanism by which stones caught in the bent portion 14 in which the triangle A is set are removed. In addition, G in the same figure is the stone which was bitten. FIG. 9A shows a state where the stone is bitten when the angle a1 at the vertex A1 is 90 ° or less. In this case, the stone G deforms the groove wall 11a, the groove wall 12a, and the top V where the groove wall 11b and the groove wall 12b are continuous as shown by the broken line, and as shown by the arrow in the figure, the force F1 , F2, F3. Since the force F3 counteracts the resultant force of the forces F1 and F2 so as to be in equilibrium with the stone G, the stone G is firmly held at the bent portion 14 and is not easily removed.
On the other hand, as shown in FIG. 9 (b), when the angle a1 at the vertex A1 is in the range of 90 ° to 130 °, the following is the state of stone biting. In this case, the stone G is held by forces F1, F2, and F3 as shown by the arrows in the figure by deforming the groove wall 11a, the groove wall 12a, and the groove wall 12b as indicated by broken lines. Since the forces F2 and F3 face each other, an equilibrium state is formed. However, since the force F1 acts in the crossing direction of the forces F2 and F3, the stone G acts in the extending direction of the linear portion 12 by the force F1. . Accordingly, the stone G is pushed out from the bent portion 14 toward the straight portion 12 and is removed from the circumferential groove 2. Therefore, by adjusting the area Sa of the triangle A and the angle a1 of the vertex A1 facing the straight line portion 12 having a wide groove width within the above range, the stone G supported at three points in the bent portion 14 is changed to the straight line portion 12. By adopting two-point extrusion, it can be excluded from the circumferential groove 2.
Further, as shown in FIG. 9C, when the angle a1 at the vertex A1 exceeds 130 °, the stone biting state at the following time is shown. In this case, the stone G is held by forces F1, F2, and F3 as shown by the arrows in the figure by deforming the groove wall 11a, the groove wall 12a, and the groove wall 12b as indicated by broken lines. Since the force F2 acts in the extending direction of the straight portion 11 and the force F3 acts in the direction of the intersecting portion between the groove wall 11a and the groove wall 12a, the stone G is pressed toward the groove wall 11a. On the other hand, although the force F1 acts in the extending direction of the straight portion 12, it is in a balanced state with the resultant force of the force F2 and the force F3.
Needless to say, the stone G is removed by the same mechanism for the triangle B set in the other bent portion 14.

In the above embodiment, the center groove 4 has been described as being formed in a zigzag shape along the tire circumferential direction, but may be formed so as to extend linearly along the tire circumferential direction. You may form like the

shoulder grooves

2 and 3.
Further, the number of the

shoulder grooves

2 and 3 having the above-described configuration formed in the tread portion is not limited to two, and more may be provided.

The tire according to an embodiment of the present invention can be described as follows. That is, a tire having a main groove extending in a zigzag shape in a tire circumferential direction in a tread portion, wherein one groove width of a main groove portion connecting bent portions adjacent to each other in the tire circumferential direction of the main groove is the other The tire is configured to be wider than the groove width of the one main groove portion, and the ratio of the groove width of the other main groove portion to the groove width of the one main groove portion is set in the range of 0.5 to 0.75. .
According to this configuration, the stone biting performance can be improved. That is, since the groove wall of the other main groove portion facing one main groove portion having a wider groove width in the bent portion approaches one main groove portion, the main stone biting holding force is changed from three-point support to two-point support, Since the stone that has been bitten can be easily removed from the groove, the stone biting performance can be improved.
As another configuration of the tire, the groove width of one and the other main groove portions is set in a range of 5 mm to 30 mm.
Further, since the main groove is provided on both the left and right shoulder sides of the tread portion, it is possible to improve the stone biting performance of the tire.
Further, provided periodically along the tire circumferential direction, and provided with a width direction groove extending in the tire width direction, the width direction groove opens to a bent portion located on the tire center side of the main groove, The stone biting performance can be further improved.

1 tread, 2, 3 shoulder groove (main groove),
4 center grooves (main grooves), 5 lug grooves, 6 narrow grooves, 22 grooves.

Claims

A tire having a tread portion having a main groove extending zigzag in the tire circumferential direction,
One groove width of the main groove portion connecting the bent portions adjacent to each other in the tire circumferential direction of the main groove is set wider than the other groove width, and the groove width of the one main groove portion is A tire characterized in that a groove width ratio of the other main groove portion is set in a range of 0.5 to 0.75.
The tire according to claim 1, wherein the width of one and the other of the main groove portions is set in a range of 5 mm to 30 mm.
The tire according to claim 1 or 2, wherein the main groove is provided on both the left and right shoulder sides of the tread portion.
Provided periodically along the tire circumferential direction, provided with a width direction groove extending in the tire width direction,
The tire according to claim 3, wherein the widthwise groove opens in a bent portion located on a tire center side of the main groove.