Pneumatic tire and stud pin

1. A pneumatic tire with a designated tire rotation direction, the pneumatic tire comprising a tread portion with a stud pin mounted in the tread portion;

the stud pin comprising:

a tip comprising an end surface having a line symmetrical shape, the end surface being configured to come into contact with a road surface, and

a body portion configured to secure the tip thereto;

the end surface of the tip configured to come into contact with a road surface comprising:

an axis of symmetry which defines the line symmetrical shape;

a centroid of a shape of the end surface offset to a first side in an axial direction of the axis of symmetry from a center position of a range on the axis the end surface covers in the axial direction;

a first most distal end portion being located on the axis of symmetry of the end surface farthest from the centroid on the first side;

a second most distal end portion being located on the axis of symmetry of the end surface farthest from the centroid on a second side opposite the first side; and

a recessed portion recessed inward of the end surface and recessed toward the axis of symmetry of the end surface, the recessed portion being provided on a periphery of the end surface running between the first most distal end portion and the second most distal end portion; wherein

the stud pin is mounted such that the second side, as opposed to the first side, corresponds to a leading side in a tire rotation direction,

two protruding portions are on each side of the axis of symmetry protruding away from the axis of symmetry, and

the recessed portion is disposed between the two protruding portions and is closer to the axis of symmetry than the two protruding portions on each side of the axis of symmetry.

2. A stud pin for mounting in a tread portion of a pneumatic tire, the stud pin comprising:

a tip comprising an end surface configured to come into contact with a road surface, and

a body portion configured to secure the tip thereto;

an end surface of the tip configured to come into contact with a road surface comprising:

an axis of symmetry which defines a line symmetrical shape of the end surface;

a centroid of a shape of the end surface offset to a first side in an axial direction of the axis of symmetry from a center position of a range on the axis the end surface covers in the axial direction;

a first most distal end portion being located on the axis of symmetry of the end surface farthest from the centroid on the first side;

a second most distal end portion being located on the axis of symmetry of the end surface farthest from the centroid on a second side opposite the first side; and

a recessed portion recessed inward of the end surface and recessed toward the axis of symmetry of the end surface, the recessed portion being provided on a periphery of the end surface running between the first most distal end portion and the second most distal end portion; wherein

two protruding portions are on each side of the axis of symmetry protruding away from the axis of symmetry, and

the recessed portion is disposed between the two protruding portions and is closer to the axis of symmetry than the two protruding portions on each side of the axis of symmetry.

3. The stud pin according to claim 2 , wherein a second length of the periphery of the end surface on the second side with respect to a bottom of the recessed portion is less than a first length of the periphery of the end surface on the first side with respect to the bottom of the recessed portion.

4. The stud pin according to claim 2 , wherein a first maximum width in a direction orthogonal to the axial direction of a portion of the end surface on the first side with respect to the bottom of the recessed portion is greater than a second maximum width in the direction orthogonal to the axial direction of a portion of the end surface on the second side with respect to the bottom of the recessed portion.

5. The stud pin according to claim 2 , wherein a first area of the portion of the end surface on the first side with respect to the bottom of the recessed portion is greater than a second area of the portion of the end surface on the second side with respect to the bottom of the recessed portion.

6. The stud pin according to claim 2 , wherein a position in the axial direction of the bottom of the recessed portion is located on the second side of the centroid.

7. The stud pin according to claim 2 , wherein

a periphery shape of the end surface on the first side with respect to the bottom of the recessed portion comprises a first orthogonal line segment orthogonal to the axial direction; and

a periphery shape of the end surface on the second side with respect to the bottom of the recessed portion comprises a second orthogonal line segment orthogonal to the axial direction with a length less than that of the first orthogonal line segment, or does not comprise the second orthogonal line segment.

8. The stud pin according to claim 2 , wherein a first periphery shape of the end surface on the first side with respect to the bottom of the recessed portion has a shape partially identical to an enlarged shape that is enlarged, by a predetermined scale factor, from second periphery shape of the end surface on the second side with respect to the bottom of the recessed portion.

9. The stud pin according to claim 8 , wherein the first periphery shape or the enlarged shape is a perfect circle, an ellipse, or a portion of a polygon.

10. The stud pin according to claim 2 , wherein a distance L 1 from a position in the axial direction of the bottom of the recessed portion to the first most distal end portion and a distance L 2 from a position in the axial direction of the bottom of the recessed portion to the second most distal end portion have a ratio L 1 /L 2 ranging from 1.0 to 5.0.

11. The stud pin according to claim 2 , wherein

the body portion comprises an upper end surface having a line symmetrical shape provided such that the tip projects therefrom; and

the upper end surface comprises:

an upper end surface axis of symmetry which defines the line symmetrical shape, an upper end surface centroid of a shape of the upper end surface offset to the first side from a center position of a range the upper end surface covers in an axial direction of the upper end surface axis of symmetry,

a third most distal end portion being located on the upper end surface axis of symmetry farthest from the upper end surface centroid on the first side;

a fourth most distal end portion being located on the upper end surface axis of symmetry farthest from the upper end surface centroid on the second side; and

an upper end surface recessed portion recessed inward of the upper end surface, the upper end surface recessed portion being provided on a periphery of the upper end surface running between the third most distal end portion and the fourth most distal end portion of the periphery of the upper end surface.

12. The stud pin according to claim 3 , wherein a first maximum width in a direction orthogonal to the axial direction of a portion of the end surface on the first side with respect to the bottom of the recessed portion is greater than a second maximum width in the direction orthogonal to the axial direction of a portion of the end surface on the second side with respect to the bottom of the recessed portion.

13. The stud pin according to claim 12 , wherein a first area of the portion of the end surface on the first side with respect to the bottom of the recessed portion is greater than a second area of the portion of the end surface on the second side with respect to the bottom of the recessed portion.

14. The pneumatic tire according to claim 1 , wherein the recessed portion is provided on each outer lateral side of the end surface, the lateral sides extending between the first most distal end portion on the first side and the second most distal end portion on the second side.

15. The pneumatic tire according to claim 1 , wherein a width of a portion sandwiched between the pair of recessed portions in the end surface in a lateral direction perpendicular to the axial direction increases from the recessed portion on each lateral side toward the first side.

16. The stud pin according to claim 2 , wherein the recessed portion is provided on each outer lateral side of the end surface, the lateral sides extending between the first most distal end portion on the first side and the second most distal end portion on the second side.

17. The stud pin according to claim 2 , wherein a width of a portion sandwiched between the pair of recessed portions in the end surface in a lateral direction perpendicular to the axial direction increases from the recessed portion on each lateral side toward the first side.

18. The pneumatic tire according to claim 1 , wherein both sides of the recessed portion are provided on the same side with respect to the axis of symmetry.

19. The pneumatic tire according to claim 1 ,

wherein the first and second most distal end portions are included in the end surface of the tip, and

wherein no portion of the end surface extends further in the axial direction on the first side than the first most distal end portion of the end surface, and no portion of the end surface extends further in the axial direction on the second side than the second most distal end portion of the end surface.

20. The stud pin according to claim 2 , wherein both sides of the recessed portion are provided on the same side with respect to the axis of symmetry.

21. The stud pin according to claim 2 ,

wherein the first and second most distal end portions are included in the end surface of the tip, and

wherein no portion of the end surface extends further in the axial direction on the first side than the first most distal end portion of the end surface, and no portion of the end surface extends further in the axial direction on the second side than the second most distal end portion of the end surface.

22. A pneumatic tire with a designated tire rotation direction, the pneumatic tire comprising a tread portion with a stud pin mounted in the tread portion;

the stud pin comprising:

a tip comprising an end surface having a line symmetrical shape, the end surface being configured to come into contact with a road surface, and

a body portion configured to secure the tip thereto;

the end surface of the tip configured to come into contact with a road surface comprising:

an axis of symmetry which defines the line symmetrical shape;

a centroid of a shape of the end surface offset to a first side in an axial direction of the axis of symmetry from a center position of a range on the axis the end surface covers in the axial direction;

a first most distal end portion being located on the axis of symmetry of the end surface farthest from the centroid on the first side;

a second most distal end portion being located on the axis of symmetry of the end surface farthest from the centroid on a second side opposite the first side; and

a recessed portion recessed inward of the end surface and recessed toward the axis of symmetry of the end surface, the recessed portion being provided on a periphery of the end surface running between the first most distal end portion and the second most distal end portion; wherein

the stud pin is mounted such that the second side, as opposed to the first side, corresponds to a leading side in a tire rotation direction,

the end surface is asymmetrical with respect to any line other than the axis of symmetry, and

the stud pin has sidewalls which are straight and parallel to the axis of symmetry.

23. A stud pin for mounting in a tread portion of a pneumatic tire, the stud pin comprising:

a tip comprising an end surface configured to come into contact with a road surface, and

a body portion configured to secure the tip thereto;

an end surface of the tip configured to come into contact with a road surface comprising:

an axis of symmetry which defines a line symmetrical shape of the end surface;

a centroid of a shape of the end surface offset to a first side in an axial direction of the axis of symmetry from a center position of a range on the axis the end surface covers in the axial direction;

a first most distal end portion being located on the axis of symmetry of the end surface farthest from the centroid on the first side;

a second most distal end portion being located on the axis of symmetry of the end surface farthest from the centroid on a second side opposite the first side; and

a recessed portion recessed inward of the end surface and recessed toward the axis of symmetry of the end surface, the recessed portion being provided on a periphery of the end surface running between the first most distal end portion and the second most distal end portion; wherein

the end surface is asymmetrical with respect to any line other than the axis of symmetry, and

the stud pin has sidewalls which are straight and parallel to the axis of symmetry.