Stud pin, and pneumatic tire
A stud pin includes a tip including a tip end surface configured to come into contact with a road surface and a trunk portion that supports the tip and extends in one direction. The trunk portion includes an upper flange disposed at a first end of the trunk portion, the tip being fixed to the upper flange, and a lower flange disposed at a position to a side opposite the upper flange of the trunk portion. An upper end surface of the upper flange from which the tip protrudes includes a recessed surface, the recessed surface including a smooth inclined surface recessing in a curved manner or a linear manner toward the lower flange with advancement toward a protruding base portion of the tip.
1. A stud pin embeddable in a pin embedding hole provided in a tread portion of a pneumatic tire, the stud pin comprising:
a tip including a tip end surface configured to come into contact with a road surface; and
a trunk portion that supports the tip and extends in one direction,
the trunk portion including:
an upper flange disposed at a first end of the trunk portion, the tip being fixed to the upper flange; and
a lower flange disposed at a position to a side opposite the upper flange of the trunk portion; wherein
an upper end surface of the upper flange from which the tip protrudes includes a recessed surface, the recessed surface including a smooth inclined surface recessing in a curved manner or a linear manner toward the lower flange with advancement toward a protruding base portion of the tip, and
a ratio W 2 /W 1 of a distance W 2 with respect to a distance W 1 is 0.3 to 0.5,
where the distance W 1 is a distance along a straight line orthogonal to and passing through a central axis of the tip that extends in an extending direction of the trunk portion from an edge of the upper flange to a position at the protruding base portion of the tip, and
the distance W 2 is a distance along the straight line from a position where the recessed surface begins to recess to a position at the protruding base portion of the tip.
2. The stud pin according to claim 1 , wherein an inclination angle of the inclined surface with respect to an orthogonal plane orthogonal to an extending direction of the trunk portion decreases with advancement toward the protruding base portion of the tip.
3. The stud pin according to claim 2 , wherein the upper end surface includes a flat surface orthogonal to an extending direction of the trunk portion, and the recessed surface is surrounded by the flat surface.
4. The stud pin according to claim 3 , wherein a depth at a most recessed position of the recessed surface is from 0.3 mm to 2.0 mm, both inclusive.
5. The stud pin according to claim 4 , wherein
in a cross section of the upper flange and the tip taken along a plane parallel to and including a central axis of the tip that extends in an extending direction of the trunk portion, the cross section being represented in an X-Y coordinate system where the extending direction toward the tip end surface is defined as a y direction, a direction orthogonal to the extending direction extending outward from the stud pin is defined as an x direction, and a position of the protruding base portion of the tip is defined as an origin point of the X-Y coordinate system,
an inclination angle with respect to an x direction at a discretionary position D on a curved or a straight line corresponding to the inclined surface is larger than an inclination angle with respect to the x direction at a same position in the x direction as the position D on a parabola, the parabola passing on the origin point and having a focus point at a point on the tip end surface that is located at a same position in the x direction as the origin point.
6. A pneumatic tire comprising:
a tread portion provided with pin embedding holes; and
stud pins according to the stud pin of claim 5 installed in the pin embedding holes.
7. The stud pin according to claim 1 , wherein the upper end surface includes a flat surface orthogonal to an extending direction of the trunk portion, and the recessed surface is surrounded by the flat surface.
8. The stud pin according to claim 1 , wherein a depth at a most recessed position of the recessed surface is from 0.3 mm to 2.0 mm, both inclusive.
9. The stud pin according to claim 1 , wherein
in a cross section of the upper flange and the tip taken along a plane parallel to and including a central axis of the tip that extends in an extending direction of the trunk portion, the cross section being represented in an X-Y coordinate system where the extending direction toward the tip end surface is defined as a y direction, a direction orthogonal to the extending direction extending outward from the stud pin is defined as an x direction, and a position of the protruding base portion of the tip is defined as an origin point of the X-Y coordinate system,
an inclination angle with respect to an x direction at a discretionary position D on a curved or a straight line corresponding to the inclined surface is larger than an inclination angle with respect to the x direction at a same position in the x direction as the position D on a parabola, the parabola passing on the origin point and having a focus point at a point on the tip end surface that is located at a same position in the x direction as the origin point.
10. A pneumatic tire comprising:
a tread portion provided with pin embedding holes; and
stud pins according to the stud pin of claim 1 installed in the pin embedding holes.