TECHNICAL FIELD

The present technology relates to a stud pin mounted in a tire and a studded tire.

BACKGROUND ART

In the related art, studded tires for use on icy and snowy roads include stud pins installed in a tread portion and provide grip on icy road surface.

Typically, a stud pin is embedded in a pin inserting hole (hereinafter, also referred to as simply “hole”) provided in the tread portion. When a stud pin is embedded in a hole, the hole expands in diameter. By inserting the stud pin into the hole in this state, the stud pin is firmly fastened in the hole and the tread portion and mounted in the tread portion. As a result, the stud pin is prevented from falling out from the hole due to receiving breaking or accelerating forces or lateral forces from the road surface when the studded tire rolls.

When the stud pin falls out from the studded tire, the stud pin falls out while rotating in the hole. Thus, to prevent the stud pin from falling out, it is preferable that the stud pin does not rotate in the hole. As such, in many technologies, the profile shape of an upper flange or a lower flange of the stud pin has been given a non-arc shape.

For example, a known stud pin includes a lower flange with a profile shape that includes protrusion portions projecting in an arc shape in opposite directions and curved portions recessed in an arc shape in an orthogonal direction orthogonal to the projection direction of the protrusion portions, wherein the stud pin is anisotropic in that the length of the profile shape in the projection direction of the protrusion portion is longer than the length of the profile shape in the orthogonal direction (see International Patent Publication No. WO 2014/027145).

The stud pin described above includes a lower flange with a profile shape that is a non-arc anisotropic shape. Thus, the stud pin does not easily fall out from the pin inserting hole. Typically, when the stud pin receives shear force from the icy road surface, the stud pin inclines so as to fall against the pin inserting hole in which it is installed. This reduces the fastening force on the stud pin from the hole. In this way, the stud pin can easily rotate about the center axis in the pin installing hole. Additionally, when the stud pin receives a large shear force from an icy road surface and the fastening force of the pin inserting hole is reduced, the stud pin rotates about the center axis. As a result, the resistance of the pin inserting hole and the tread portion holding the stud pin in the pin inserting hole against the shear force received from an icy road surface is decreased, and the stud pin is more likely to fall out from the pin inserting hole.

The stud pin described above including an upper flange or a lower flange with a non-arc shaped profile shape can suppress the stud pin from falling out but cannot sufficiently suppress the rotation of the stud pin which is the initial cause of the falling out. It is conceivable that by suppressing the rotation of the stud pin, the stud pin falling out can be further suppressed.

SUMMARY

The present technology provides a stud pin that does not easily fall out from a pin inserting hole of a studded tire and is capable of suppressing the rotation of a stud pin which is the initial cause of the stud pin falling out and a studded tire installed with the stud pin.

One aspect of the present technology is a stud pin installable in a tire. The stud pin includes a tip including an end surface that comes into contact with a road surface; a body portion that supports the tip so that the tip projects from an end surface on one side of the body portion; and a lower flange connected to an end of the body portion on an opposite side to the end surface.

A profile shape of the lower flange as viewed from an arrangement direction of the tip, the body portion, and the lower flange, is an anisotropic shape in which, of imaginary rectangles circumscribing the flange profile shape, a first smallest rectangle with the shortest side of its four sides being smallest and/or a second smallest rectangle with the longest side of its four sides being smallest includes short sides and long sides of different lengths.

The profile shape includes four or more first protrusion portions that project toward a longitudinal direction parallel with the long sides and two second protrusion portions that project toward a lateral direction parallel with the short sides.

Preferably, the first protrusion portion is constituted by two pairs thereof;

the profile shape comprises two first recess portions curved toward a centroid of the profile shape and disposed between each of the pairs of first protrusion portions; and

the profile shape further comprises four second recess portions curved toward the centroid, disposed between each of the second protrusion portions and one of the first protrusion portions, and smoothly connect to one of the first protrusion portions.

Preferably, a recess depth of the first recess portions is equal to or greater than a recess depth of the second recess portions.

Preferably, the two first recess portions are formed with a line symmetrical shape with respect to a first imaginary straight line parallel with the lateral direction that extends through the centroid and/or formed with a line symmetrical shape with respect to a second imaginary straight line parallel with the longitudinal direction that extends through the centroid.

Preferably, the four second recess portions are formed with a line symmetrical shape with respect to a first imaginary straight line parallel with the lateral direction that extends through the centroid and/or formed with a line symmetrical shape with respect to a second imaginary straight line parallel with the longitudinal direction that extends through the centroid.

Preferably, the two second protrusion portions comprise two linear portions parallel with the longitudinal direction; and

the linear portions are portions projecting the most in the lateral direction.

Preferably, the two linear portions are formed with a line symmetrical shape with respect to a first imaginary straight line parallel with the lateral direction that extends through the centroid and/or formed with a line symmetrical shape with respect to a second imaginary straight line parallel with the longitudinal direction that extends through the centroid.

Preferably, the two second protrusion portions comprise two linear portions parallel with the longitudinal direction;

the linear portions are portions projecting the most in the lateral direction; and

both ends of each of the two linear portions connect with two second recess portions of the four second recess portion.

Another aspect of the present technology is a studded tire installed with a stud pin, comprising a tread portion installed with the stud pin described above with the longitudinal direction facing a tire circumferential direction.

Another aspect of the present technology is a studded tire installed with a stud pin, comprising a tread portion installed with the stud pin described above with the lateral direction facing a tire circumferential direction.

According to the stud pin and the studded tire described above, the stud pin does not easily fall out from a pin inserting hole of a studded tire, and the rotation of a stud pin which is the initial cause of the stud pin falling out can be suppressed.

