Patent Publication Number: US-11396211-B2

Title: Stud pin and studded tire

Description:
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 an upper flange or a lower flange with a profile shape that has an anisotropic non-arc shape, so 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. Furthermore, when the stud pin receives a large shear force from an icy road surface, the fastening force provided by the pin inserting hole is reduced, and the stud pin rotates about the center axis. When the stud pin rotates, 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. 
     SUMMARY 
     The stud pin including the upper flange or the lower flange with a non-arc shape profile shape can suppress the stud pin falling out, but it is not sufficient to suppress the rotation of the stud pin, which is an initial cause of the stud pin falling out. It is conceived that, by suppressing the rotation of the stud pin, it is possible to further suppress the stud pin falling out. 
     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 flange 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 a shortest side of its four sides being smallest and/or a second smallest rectangle with a longest side of its four sides being smallest comprise short sides and long sides of different lengths. A body profile shape of the body portion as viewed from the arrangement direction has an anisotropic shape in which a length of the body profile shape in a longitudinal direction parallel with the long sides is different from a length of the body profile shape in a lateral direction parallel with the short sides. 
     The flange profile shape includes four or more first flange protrusion portions F 1  projecting toward the longitudinal direction and two second flange protrusion portions F 2  projecting toward the lateral direction. The body profile shape includes four or more first body protrusion portions B 1  projecting toward the lateral direction and two second body protrusion portions B 2  projecting toward the longitudinal direction. 
     Preferably, the first flange protrusion portions F 1  are constituted by two pairs thereof; and the flange profile shape comprises two first flange recess portions F 3  and four second flange recess portions F 4 , the two first flange recess portions F 3  being curved toward a centroid of the flange profile shape and disposed between each of the pairs of the first flange protrusion portions F 1 , the four second flange recess portions F 4  being curved toward the centroid, disposed between each of the second flange protrusion portions F 2  and one of the first flange protrusion portions F 1 , and smoothly connect to one of the first flange protrusion portions F 1 . 
     Preferably, a recess depth of the first flange recess portions F 3  is equal to or greater than a recess depth of the second flange recess portions F 4 . 
     Preferably, the two second flange protrusion portions F 2  comprise two linear portions parallel with the longitudinal direction; and the linear portions are portions projecting the most in the lateral direction. 
     Preferably, the first body protrusion portions B 1  are constituted by two pairs thereof; the body profile shape comprises two first body recess portions B 3  curved toward a centroid of the body profile shape and disposed between each of the pairs of the first body protrusion portions B 1 ; and the first body recess portions B 3  are disposed facing the linear portions at a position on the body profile shape centroid side of the linear portions in a plan view of the lower flange and the body portion from the arrangement direction. 
     Preferably, the second body protrusion portions B 2  are disposed facing the first flange recess portions F 3  at a position on the body profile shape centroid side of the first flange recess portions F 3  in a plan view of the lower flange and the body portion from the arrangement direction. 
     Preferably, the second body protrusion portions B 2  are curved away from the centroid of the body profile shape in a plan view of the lower flange and the body portion in the arrangement direction; and a radius of curvature of the second body protrusion portions B 2  at a position where the second body protrusion portions B 2  are closest to the first flange recess portions F 3  is greater than a radius of curvature of the first flange recess portions F 3  at a position where the first flange recess portion F 3  is closest to the second body protrusion portions B 2 . 
     Another embodiment of the present technology is a studded tire installed with a stud pin, comprising a tread portion installed with the stud pin with the longitudinal direction or 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. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a tire cross-sectional view illustrating an example of a cross section of a tire of a present embodiment. 
         FIG. 2  is a perspective view of the tire of the present embodiment. 
         FIG. 3  is a developed plan view illustrating a portion of an example of a tread pattern of the studded tire of the present embodiment, developed on a plane. 
         FIG. 4A  is a perspective view of a stud pin of the present embodiment.  FIG. 4B  is a plan view of the stud pin of the present embodiment. 
         FIG. 5  is a diagram illustrating the profile shape of the lower flange according to an embodiment. 
         FIGS. 6A and 6B  are diagrams illustrating the orientation of the stud pin installed in the tire. 
     
    
    
     DETAILED DESCRIPTION 
     Overall Description of Tire 
     Hereinafter, a studded tire of the present embodiment is described.  FIG. 1  is a tire cross-sectional view illustrating an example of a cross section of a studded tire (hereinafter also referred to as “tire”)  10  of the present embodiment.  FIG. 2  is a perspective view of the tire  10 . 
     The tire  10  is a tire with stud pins embedded in a tread portion (the stud pins are not illustrated in  FIGS. 1 and 2 ). 
     The tire  10  is, for example, a tire for a passenger vehicle. A tire for a passenger vehicle refers to a tire specified in Chapter A of the JATMA Year Book 2012 (standards of The Japan Automobile Tyre Manufacturers Association, Inc.). The tire can also be a small truck tire specified in Chapter B or a truck tire or bus tire specified in Chapter C. 
     Values of the dimensions of various pattern elements are described in detail below as example values for a tire for a passenger vehicle. However, the studded tire is not limited to these example values. 
     “Tire circumferential direction C” described below (see  FIG. 2 ) refers to the direction the tread surface rotates when the tire  10  rotates about a tire rotation axis Axis (see  FIG. 2 ). “Tire radial direction R” refers to the direction that extends radially orthogonal to the tire rotation axis Axis. “Outward in the tire radial direction” refers to the direction away from the tire rotation axis Axis in the tire radial direction R. “Tire lateral direction W” refers to the direction parallel with the tire rotation axis Axis. “Outward in the tire lateral direction” refers to the direction away from a tire equator line CL (see  FIG. 3 ) of the tire  10 . 
     Tire Structure 
     The tire  10  includes a carcass ply  12 , a belt  14 , and bead cores  16  as framework members. The tire  10  also mainly includes a tread rubber  18 , side rubbers  20 , bead filler rubbers  22 , rim cushion rubbers  24 , and an innerliner rubber  26  around the framework members. 
     The carcass ply  12  includes carcass ply members  12   a ,  12   b  that are formed from organic fibers covered with rubber and that are wound between the pair of bead cores  16  of an annular shape so as to be formed into a toroidal shape. In the tire  10  illustrated in  FIG. 1 , the carcass ply  12  is made of the carcass ply members  12   a  and  12   b , but may also be made of a single carcass ply member. The belt  14  is provided outward of the carcass ply  12  in the tire radial direction and is constituted of two belt members  14   a ,  14   b . The belt  14  is a member formed from steel cords covered with rubber, the steel cords being arranged inclined at a predetermined angle, for example, 20 to 30 degrees, with respect to the tire circumferential direction C. The width in the tire lateral direction of the belt member  14   a  that is a lower layer is greater than the width of the belt member  14   b  that is the upper layer. The steel cords of the two layers of the belt members  14   a  and  14   b  are inclined from the tire circumferential direction C toward the tire lateral direction W in mutually different directions. As such, the belt members  14   a ,  14   b  are crossing layers serving to suppress expansion of the carcass ply  12  due to the pressure of the air in the tire. 
     The tread rubber  18  is disposed outward of the belt  14  in the tire radial direction. Both end portions of the tread rubber  18  are connected to the side rubbers  20  to form sidewall portions. The tread rubber  18  is made of two layers of rubber, namely an upper layer tread rubber  18   a  provided on the outer side in the tire radial direction and a lower layer tread rubber  18   b  provided on the inner side in the tire radial direction. The rim cushion rubbers  24  are provided at the ends of the side rubbers  20  on the inner side in the tire radial direction, and come into contact with the rim on which the tire  10  is mounted. The bead filler rubbers  22  are provided outward of the bead cores  16  in the tire radial direction so as to be interposed between a portion of the carcass ply  12  before where it is wound around the bead cores  16  and a portion of the carcass ply  12  after where it is wound around the bead cores  16 . The innerliner rubber  26  is provided on the inner surface of the tire  10  facing a tire cavity region that is filled with air and is surrounded by the tire  10  and the rim. 
     In addition, the tire  10  includes a belt cover layer  28  formed from organic fiber covered with rubber that covers the belt  14  from the outer side in the tire radial direction of the belt  14 . 
     The tire  10  has such a tire structure, but the tire structure of the present embodiment is not limited to the tire structure illustrated in  FIG. 1 . 
     Tread Pattern 
       FIG. 3  is a developed plan view illustrating a portion of an example of the tread pattern, namely a tread pattern  30 , of the tire  10  developed on a plane. In  FIG. 3 , the stud pins installed in the tread portion are omitted from the illustration. As illustrated in  FIG. 3 , the tire  10  has a designated rotation direction X indicating a one-way direction along the tire circumferential direction C. Orientation information of the rotation direction X is illustrated by an information display portion including numbers, symbols, and the like (e.g., an arrow symbol) on the sidewall surface of the tire  10 . The stud pins (see  FIG. 4A ) are installed in a plurality of pin inserting holes  29  illustrated in  FIG. 3 . 
     The tread pattern  30  includes an inclined groove  32 , a circumferential direction communicating groove  34 , a projecting groove  36 , and a sipe  38 . 
     A plurality of the inclined groove  32  are formed at predetermined intervals in the tire circumferential direction (vertical direction in  FIG. 3 ). 
     The inclined groove  32  extends in a direction opposite (the up direction in  FIG. 3 ) the tire rotation direction X (the down direction in  FIG. 3 ) and outward in the tire lateral direction. The inclined groove  32  has a starting end at a position near the tire equator line CL on one side of the tire equator line CL in the tire lateral direction W, crosses the tire equator line CL and advances toward the other side in the tire lateral direction W, and ends at a pattern end PE. 
     The groove width of the inclined groove  32  gradually increases from the starting end near the tire equator line CL. The inclination with respect to the tire lateral direction W of the inclined groove  32  is the smallest in a region near the tire equator line CL including the starting end and, after crossing the tire equator line CL, bends so as that the inclination angle with respect to the tire lateral direction W increases, and advances outward in the tire lateral direction in a direction opposite the tire rotation direction X. Furthermore, the inclination angle gradually decreases with advancement outward in the tire lateral direction. The inclined grooves  32  configured as described above are provided on both sides of the tire equator line CL. 
     The inclined grooves  32  provided on one side of the tire equator line CL of the tread portion are offset with respect to the tire circumferential direction C from the inclined grooves  32  provided on the other side. The starting ends of the inclined grooves  32  on one side do not connect with the inclined grooves  32  provided on the other side. 
     Of the plurality of inclined grooves  32  provided in the tire circumferential direction C, the inclined grooves  32  that are adjacent are in communication via the circumferential direction communicating groove  34 . More specifically, the circumferential direction communicating groove  34  extends in the tire circumferential direction C from a position partway along one of the inclined grooves  32 , crosses a second inclined groove  32  that is adjacent to the first inclined groove  32  in the tire circumferential direction C, and advances to a third inclined groove  32  that is adjacent to the second inclined groove  32 . That is, the circumferential direction communicating groove  34  starts at one of the inclined grooves  32  (first inclined groove  32 ), extends along the tire circumferential direction C from the first inclined groove  32  at which the circumferential direction communicating groove  34  starts, and terminates at a second inclined groove  32 . In this way, the circumferential direction communicating groove  34  is provided so as to connect three of the inclined grooves  32  that are adjacent along the tire circumferential direction C. The circumferential direction communicating groove  34  is inclined with respect to the tire circumferential direction C so as to approach the tire equator line CL with advancement in the direction opposite to the tire rotation direction X. 
     The projecting groove  36  projects in a direction toward the tire equator line CL from the circumferential direction communicating groove  34 , and is provided so as to terminate prior to reaching the tire equator line CL. 
     Land portions of the tread portion are separated into a center region and shoulder regions by the inclined grooves  32  and the circumferential direction communicating grooves  34 . A plurality of the sipes  38  connected to the inclined grooves  32  and the circumferential direction communicating grooves  34  is provided in the center region and both of the shoulder regions of the tread portion. 
     Furthermore, the plurality of the pin inserting holes  29  is provided in the center region and both of the shoulder regions of the tread portion. 
     The inclined groove  32 , the circumferential direction communicating groove  34 , and the projecting groove  36  have a groove depth of, for example, from 8.5 mm to 10.5 mm, and a maximum groove width of 12 mm. The tread pattern illustrated in  FIG. 3  is an example, and the tread pattern of the tire in which the stud pins of the present embodiment are installed in is not limited to the embodiment illustrated in  FIG. 3 . 
     Stud Pin 
       FIG. 4A  is a perspective view of a stud pin  50  of the present embodiment.  FIG. 4B  is a plan view of the stud pin  50  of the present embodiment. 
     The stud pin  50  includes a tip  52 , a body portion  54 , and a lower flange  56 . The body portion  54  includes an upper flange  58  and a shank portion  60 . When installed in the pin inserting holes  29  of the tire  10 , the body portion  54  and the lower flange  56  are embedded in the tread rubber  18  (see  FIG. 1 ) and are in contact with the tread rubber  18 . 
     The tip  52  includes a tip end surface that comes into contact with a road surface. The tip  52  is formed from tungsten carbide or a similar hard metal. According to an embodiment, the tip  52  may be formed from a cermet material. The tip  52  is fixed in a hole provided in an upper end surface  54   a  of the body portion  54 . The tip  52  of the stud pin  50  is configured to protrude from the tread surface when the stud pin  50  is installed in the tire  10 . 
     The tip  52  projects from the upper end surface  54   a  of the body portion  54  in a columnar shape, and the end surface thereof is a concave decagon formed by two regular hexagons joined together on one side, as illustrated in  FIG. 4B . According to an embodiment, the tip  52  projects in a columnar shape and the end surface thereof may be an arc shape, an elliptical shape, a polygonal shape (convex polygonal shape), a concave polygonal shape, or a shape thereof with a portion changed to a straight line, a curved line with a concave curve, or a wave-like shape with undulations. 
     The body portion  54  is a portion that supports the tip  52  with the tip  52  projecting from the upper end surface  54   a  on one side. The body portion  54  extends in the direction opposite to the projection direction of the tip  52 . The extension direction of the body portion  54  is also the direction in which the tip  52 , the body portion  54 , and the lower flange  56  are arranged, and this direction is referred to as the H-direction. 
     The upper flange  58  of the body portion  54  is configured so that, when embedded in the tread portion of the tire  10 , the tip  52  protrudes from the tread surface. The tip  52  is fixed on upper end surface  54   a  of the body portion  54 . 
     The lower flange  56  is configured to come into contact with a bottom of the pin inserting hole  29 , when embedded in the tread portion of the tire  10 . The lower flange  56  is connected to the end of the shank portion  60  on the opposite side of the upper end surface  54   a  of the body portion  54 . 
     The shank portion  60  is the portion that connects the upper flange  58  and the lower flange  56 . The cross section of the shank portion  60  in the direction orthogonal to the H-direction is thinner than the cross sections of the upper flange  58  and the lower flange  56 . 
     The material of the body portion  54  and the lower flange  56  is not particularly limited but is preferably different from the material of the tip  52 . According to an embodiment, the body portion  54  and the lower flange  56  are formed from aluminum alloy or the like in order to reduce the weight of the stud pin  50 . 
     A flange profile shape  62  of the lower flange  56  is an anisotropic shape when the lower flange  56  is viewed from the H-direction. Here, as illustrated in  FIG. 4B , the anisotropic shape is a shape in which, of imaginary rectangles circumscribing the flange profile shape  62  and inclined in various directions, a first smallest rectangle with the shortest side of it 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. In  FIG. 4B , a first smallest rectangle  100  is illustrated. In this example, the first smallest rectangle  100  includes a side  100   a  corresponding to the shortest of the shortest sides. The first smallest rectangle  100  also corresponds to the second smallest rectangle. In other words, the second smallest rectangle includes a side  100   b  corresponding to the shortest of the longest sides. The side  100   a  of the sides of the first smallest rectangle  100 , which is also the second smallest rectangle, is a short side, and the side  100   b  is a long side. Accordingly, the flange profile shape  62  of the lower flange  56  is an anisotropic shape. 
     The flange profile shape  62  of the lower flange  56  with such an anisotropic shape includes four first flange protrusion portions F 1  that project in the longitudinal direction L parallel with the long side (side  100   b ) and two second flange protrusion portions F 2  that project in the lateral direction S parallel with the short side (side  100   a ). Hereinafter, the side  100   b  is referred to as “long side  100   b ”, and the side  100   a  is referred to as “short side  100   a”.    
     Here, “first flange protrusion portion F 1 ” means the portion formed in a protruding shape protruding in the longitudinal direction L located in a region separated in the longitudinal direction L a distance equal to or greater than half of the distance from a straight line parallel with the lateral direction S that goes through the center of the first smallest rectangle  100  (the intersection point of two diagonal lines) to the short side  100   a  from the parallel straight line. “Protruding shape” refers to the shape of a portion that approaches the parallel straight line (a straight line parallel with the lateral direction S that extends through the center of the first smallest rectangle  100 ) as it extends outward on both sides to the outer circumference of the flange profile shape  62  from a point on the flange profile shape  62 . 
     “Second flange protrusion portion F 2 ” is the portion formed in a protruding shape protruding in the lateral direction S located in a region separated in the lateral direction S, a distance equal to or greater than half of the distance from a straight line parallel with the longitudinal direction L that goes through the center of the first smallest rectangle  100  (the intersection point of two diagonal lines) to the long side  100   b  from the parallel straight line. “Protruding shape” refers to the shape of a portion that approaches the parallel straight line (a straight line parallel with the longitudinal direction L that extends through the center of the first smallest rectangle  100 ) as it extends outward on both sides to the outer circumference of the flange profile shape  62  from a point on the flange profile shape  62 . 
     In the present embodiment, the flange profile shape  62  of the lower flange  56  includes the four first flange protrusion portions F 1  and the two second flange protrusion portions F 2 . Two of the first flange protrusion portions F 1  face a first direction of the longitudinal direction L, and the other two first flange protrusion portions F 1  face a second direction opposite to the first direction. One of the second flange protrusion portions F 2  faces a third direction of the lateral direction S, and the other second flange protrusion portion F 2  faces a fourth direction opposite to the third direction. The number of the first flange protrusion portions F 1  facing the first direction of the longitudinal direction L is the same as the number of first flange protrusion portions F 1  facing the second direction. According to an embodiment, preferably, three of the first flange protrusion portions F 1  face the first direction of the longitudinal direction L and the other first flange protrusion portion F 1  faces the second direction opposite to the first direction, and one of the second flange protrusion portions F 2  faces a third direction of the lateral direction S and the other second flange protrusion portion F 2  faces a fourth direction opposite to the third direction. 
     Additionally, according to an embodiment, the flange profile shape  62  of the lower flange  56  preferably includes five, six, or seven first flange protrusion portions F 1  and two second flange protrusion portions F 2 . In this embodiment, the number of the first flange protrusion portions F 1  facing the first direction of the longitudinal direction L may be the same as or different to the number of first flange protrusion portions F 1  facing the second direction. 
     Furthermore, according to the present embodiment, a body profile shape  64  of the upper flange  58  when viewed in the H-direction is also an anisotropic shape in which the length of the body profile shape  64  in the longitudinal direction L and the length of the body profile shape  64  in the lateral direction S are different. Furthermore, the body profile shape  64  includes four or more first body protrusion portions B 1  that project in the lateral direction S and two second body protrusion portions B 2  that project in the longitudinal direction L. 
     Here, “first body protrusion portion B 1 ” means the portion formed in a protruding shape protruding in the lateral direction S located in a region separated in the lateral direction S, a distance equal to or greater than half of the distance from a straight line parallel with the longitudinal direction L that goes through the centroid of the body profile shape  64  to a position of the body profile shape  64  furthest separated from this straight line. “Protruding shape” refers to the shape of a portion that approaches the parallel straight line (a straight line parallel with the longitudinal direction L that extends through the centroid of the body profile shape  64 ) as it extends outward on both sides to the outer circumference of the body profile shape  64  from a point on the body profile shape  64 . 
     Here, “second body protrusion portion B 2 ” is the portion formed in a protruding shape protruding in the longitudinal direction L located in a region separated in the longitudinal direction L, a distance equal to or greater than half of the distance from a straight line parallel with the lateral direction S that goes through the centroid of the body profile shape  64  to a position of the body profile shape  64  furthest separated from this straight line. “Protruding shape” refers to the shape of a portion that approaches the parallel straight line (a straight line parallel with the lateral direction S that extends through the centroid of the body profile shape  64 ) as it extends outward on both sides to the outer circumference of the body profile shape  64  from a point on the body profile shape  64 . 
     In the present embodiment, the body profile shape  64  of the upper flange  58  includes the four first body protrusion portions B 1  and the two second body protrusion portions B 2 . Two of the first body protrusion portions B 1  face a first direction of the lateral direction S, and the other two first body protrusion portions B 1  face a second direction opposite to the first direction. One of the second body protrusion portions B 2  faces a third direction of the longitudinal direction L, and the other second body protrusion portion B 2  faces a fourth direction opposite to the third direction. The number of the first body protrusion portions B 1  facing the first direction of the lateral direction S is the same as the number of first body protrusion portions B 1  facing the second direction. According to an embodiment, preferably, three of the first body protrusion portions B 1  face the first direction of the lateral direction S and the other first body protrusion portion B 1  faces the second direction opposite to the first direction, and one of the second body protrusion portions B 2  faces a third direction of the lateral direction S and the other second body protrusion portion B 2  faces a fourth direction opposite to the third direction. 
     Additionally, according to an embodiment, the profile shape  64  of the upper flange  58  preferably includes five, six, or seven first body protrusion portions B 1  and two second body protrusion portions B 2 . In this embodiment, the number of the first body protrusion portions B 1  facing the first direction of the lateral direction S may be the same as or different to the number of first body protrusion portions B 1  facing the second direction. 
     In the present embodiment, the stud pin  50  includes four first body protrusion portions B 1  projecting in the lateral direction S and four first flange protrusion portions F 1  projecting in the longitudinal direction L, and rotation of the stud pin  50 , which is an initial cause of the stud pin falling out from the pin inserting hole  29 , is suppressed. Also, the stud pin  50  includes two second body protrusion portions B 2  projecting in the longitudinal direction L and two second flange protrusion portions F 2  projecting in the lateral direction S, and the stud pin  50  has high holding force that prevents the stud pin from inclining and moving out from the pin inserting hole  29  when the stud pin receives a shear force from an icy road surface. Thus, the stud pin  50  does not easily fall out from the pin inserting hole  29 . In other words, pin drop resistance is greatly improved. 
     Specifically, the flange profile shape  62  includes the large second flange protrusion portion F 2  along the longitudinal direction L, and the body profile shape  64  includes the large second body protrusion portion B 2  along the lateral direction S. This further increases the holding strength to prevent the movement of the stud pin  50  that receives shear force from an icy road surface to incline and fall out from the pin inserting hole  29 . As a result, the stud pin  50  does not easily fall out from the pin inserting hole  29 . 
     Also, prior to the stud pin  50  falling out from the pin inserting hole  29 , as described above, the stud pin  50  rotates in the pin inserting hole  29 . When the stud pin  50  rotates, the resistance of the pin inserting hole  29  and the tread rubber  18  holding the stud pin  50  in the pin inserting hole  29  against the shear force received from an icy road surface is decreased, and the stud pin  50  is more likely to fall out from the pin inserting hole  29 . However, the body profile shape  64  of the stud pin  50  includes four of the first body protrusion portions B 1 , and the flange profile shape  62  includes four of the first flange protrusion portions F 1 , forming undulations in the upper flange  58  and the lower flange  56 . Thus, the stud pin  50  is fastened and fixed in the pin inserting hole  29  with the tread rubber  18  deformed corresponding to these undulations. Thus, the stud pin  50  inclines only slightly in a collapsing direction when the stud pin  50  receives a shear force from an icy road surface. Accordingly, a gap is not easily formed between the stud pin  50  and the pin inserting holes  29  due to the stud pin  50  inclining. As a result, the body portion  54  and the lower flange  56  can be tightly fastened by the tread rubber  18  (the inner wall surface of the pin inserting hole  29 ), and the rotation of the stud pin  50  in the pin inserting holes  29  which is an initial cause of the stud pin  50  falling out can be suppressed. Thus, the stud pin  50  of the present embodiment can suppress the stud pin  50  from falling out better than known stud pins including a lower flange with a profile shape that has a non-arc shape. 
     Furthermore, even when the stud pin  50  receives shear force from an icy road surface, a gap between the stud pin  50  and the pin inserting hole  29  is not easily formed, and the stud pin  50  is not easily moved out of position in the pin inserting hole  29  (does not come loose). As a result, the stud pin  50  does not easily fall out from the pin inserting hole  29 , the shear force between the stud pin  50  and an icy road surface is efficiently transferred to the belt  14 , to the entire studded tire  10 , and to the vehicle mounted with the studded tire  10 . Thus, the braking and driving properties and controllability on icy road surfaces is improved. 
       FIG. 5  is a diagram illustrating the flange profile shape  62  and the body profile shape  64  according to an embodiment. 
     According to an embodiment, as illustrated in  FIG. 5 , the first flange protrusion portion F 1  is constituted by two pairs of first flange protrusion portions F 1 . In other words, when in the plan view of the paper of  FIG. 5 , two first flange protrusion portions F 1  projecting leftward in the longitudinal direction L are defined as one pair, and two first flange protrusion portions F 1  projecting rightward in the longitudinal direction L are defined as the other pair. The flange profile shape  62  of the lower flange  56  preferably includes two first flange recess portions F 3  that are curved toward a centroid G of the flange profile shape  62  and are disposed between each pair of the first flange protrusion portions F 1 . Here, the flange profile shape  62  preferably includes four second flange recess portions F 4  that are curved toward the centroid G, are disposed between each of the second flange protrusion portions F 2  and one of the first flange protrusion portions F 1 , and smoothly connect to one of the first flange protrusion portions F 1 . 
     The flange profile shape  62  includes the first flange recess portions F 3 . Thus, when the lower flange  56  comes into contact with the inner wall surface of the pin inserting holes  29 , the area of the contact surface in the lateral direction S is increased. This improves the holding strength preventing the movement of the stud pin  50  to fall out of the pin inserting hole  29 . As a result, the stud pin  50  can be suppressed from falling out from the pin inserting hole  29 . 
     Additionally, the flange profile shape  62  includes the second flange recess portion F 4  at four sections, forming four recesses around the circumference of the flange profile shape  62 . As a result, the installing fingers of a stud pin installation device used in installing the stud pin  50  into the pin inserting hole  29  can more easily grip the lower flange  56  of the stud pin  50 . In other words, when the installing fingers grip the lower flange  56  with an anisotropic shape, the stud pin  50  is gripped such that the anisotropic shape takes a suitable orientation and can be installed in the pin inserting hole  29 . This improves pin installation properties. 
     According to an embodiment, as illustrated in  FIG. 5 , the recess depth of the first flange recess portions F 3  is preferably the same as the recess depth of the second flange recess portions F 4  or greater than the recess depth of the second flange recess portions F 4 . Here, “recess depth” refers to the distance from a straight line connecting two of the first flange recess portions F 3  on either side of the first flange recess portion F 3  or the second flange recess portion F 4  or a straight line connecting one of the first flange protrusion portions F 1  to one of the second flange protrusion portions F 2  to a point locate farthest from the first flange recess portion F 3  or the second flange recess portion F 4 . With a shape in which the recess depth is defined as such, the area of the contact surface in the lateral direction S where the lower flange  56  comes into contact with the inner wall surface of the pin inserting hole  29  can be increased, and the recess on the side in the lateral direction S can be enlarged. This allows the rotation of the stud pin  50  to be further suppressed. Furthermore, holding strength to prevent the stud pin  50  from falling out from the pin inserting hole  29  is increased. 
     According to an embodiment, the curved shape of the first flange recess portions F 3  and the curved shape of the second flange recess portions F 4  are preferably arc shapes with a set radius of curvature. In the case of the curved shape of the first flange recess portions F 3  and the curved shape of the second flange recess portions F 4  being formed with a single radius of curvature, the radius of curvature of the first flange recess portions F 3  is preferably equal to or less than the radius of curvature of the second flange recess portions F 4 . For example, to improve the holding strength described above, the radius of curvature of the first flange recess portions F 3  is preferably equal to or less than 50% of the radius of curvature of the second flange recess portions F 4 . 
     According to an embodiment, as illustrated in  FIG. 5 , the two second flange protrusion portions F 2  include two linear portions F 5  parallel with the longitudinal direction L. The linear portions F 5  are preferably the portions projecting the most in the lateral direction S. With such a configuration, the installing fingers of a stud pin installation device used in installing the stud pin  50  into the pin inserting hole  29  can more easily grip the lower flange  56  of the stud pin  50 . For example, in the case of the linear portions F 5  being at the gripping position of the installing fingers, if the gripping position of the installing fingers strays from the predetermined position along the linear portions F 5 , the range of the linear portions F 5  which the installing fingers can grip is large allowing the stud pin  50  to be stability gripped. As a result, the number of times the stud pin  50  is incorrectly installed in the pin inserting holes  29  is reduced. 
     According to an embodiment, as illustrated in  FIG. 5 , the second body protrusion portions B 2  of the body profile shape  64  are preferably disposed facing the first flange recess portion F 3  at a position on the centroid G side of the first flange recess portion F 3 , when the lower flange  56  and the body portion  54  are viewed from the H-direction. Here, “the second body protrusion portion B 2  being disposed facing the first flange recess portion F 3 ” refers to the projecting end position of the second body protrusion portion B 2  furthest separated from the centroid G being on a line segment connecting a recessed bottom position of the first flange recess portion F 3  closest to the centroid G and the centroid G. By providing the first flange recess portion F 3 , the contact area between the stud pin  50  and the inner wall surface of the pin inserting hole  29  is increased. Moreover, since the body portion  54  is provided with the second body protrusion portion B 2  facing the first flange recess portion F 3 , forming undulations in the H-direction, the holding force that prevents the stud pin  50  from moving out from the pin inserting hole  29  is increased. 
     According to an embodiment, as illustrated in  FIG. 5 , a first body recess portion B 3  is preferably disposed between a pair of the first body protrusion portions B 1  of the body profile shape  64 , when the lower flange  56  and the body portion  54  are viewed from the H-direction. The first body recess portion B 3  is preferably disposed facing the second flange protrusion portion F 2  at a position on the centroid G side of the second flange protrusion portion F 2 . Here, “the first body recess portion B 3  being disposed facing the second flange protrusion portion F 2 ” refers to the position on the linear portion F 5  closest to the centroid G being on a line connecting a recessed bottom position of the first body recess portion B 3  closest to the centroid G and the centroid G. 
     In this way, with the first body recess portion B 3  being disposed facing the second flange protrusion portion F 2 , the large second flange protrusion portion F 2  of the lower flange  56  is exposed outward. Thus, the tread rubber member at and near the pin inserting hole  29  can come into contact with the first body recess portion B 3 , and this contact area can be increased. This allows the stud pin  50  to be tightly fastened by the inner wall surface of the pin inserting hole  29 . As a result, the holding strength to prevent the stud pin  50  from falling out from the pin inserting hole is improved. As a result, the stud pin  50  can be suppressed from falling out from the pin inserting hole  29 . 
     According to an embodiment, as illustrated in  FIG. 5 , the second body protrusion portions B 2  are curved away from the centroid G, when the lower flange  56  and the body portion  54  are viewed from the H-direction. Here, the radius of curvature of the second body protrusion portion B 2  at the position where the second body protrusion portion B 2  is the closest to the first flange recess portion F 3  is preferably greater than the radius of curvature of the first flange recess portion F 3  at the position where the first flange recess portion F 3  is closest to the second body protrusion portion B 2 . 
     With the radius of curvature of the second body protrusion portion B 2  being greater than the radius of curvature of the first flange recess portion F 3 , the contact area with the inner wall surface of the pin inserting hole  29  with which the lower flange  56  and the upper flange  58  come in contact is increased, and large undulations are formed in the H-direction. As a result, the stud pin  50  is firmly tightened by the inner wall surface of the pin inserting hole  29 . As a result, the holding strength to prevent the stud pin  50  from falling out from the pin inserting hole is improved. The radius of curvature of the second body protrusion portion B 2  is preferably two-times or greater than the radius of curvature of the first flange recess portion F 3 . 
     According to an embodiment, as illustrated in  FIG. 5 , the two first flange recess portions F 3  are preferably formed with a line symmetrical shape about a first imaginary straight line parallel with the lateral direction S and extending through a centroid G and/or formed with a line symmetrical shape about a second imaginary straight line parallel with the longitudinal direction L and extending through the centroid G. In this way, when the stud pin  50  is installed in the pin inserting hole  29 , the installing fingers can easily grip the stud pin  50  with a target orientation. 
     According to an embodiment, as illustrated in  FIG. 5 , the four second flange recess portions F 4  are preferably formed with a line symmetrical shape about a first imaginary straight line parallel with the lateral direction S and extending through the centroid G and/or formed with a line symmetrical shape about a second imaginary straight line parallel with the longitudinal direction L and extending through the centroid G. In this way, when the stud pin  50  is installed in the pin inserting hole  29 , the installing fingers can easily grip the stud pin  50  with a target orientation. 
     According to an embodiment, as illustrated in  FIG. 5 , in the case of the flange profile shape  62  including two of the linear portions F 5 , the two linear portions F 5  are preferably formed with a line symmetrical shape about a first imaginary straight line parallel with the lateral direction S and extending through the centroid G and/or formed with a line symmetrical shape about a second imaginary straight line parallel with the longitudinal direction L and extending through the centroid G. In this way, when the stud pin  50  is installed in the pin inserting hole  29 , the installing fingers can easily grip the stud pin  50  with a target orientation. 
     According to an embodiment, as illustrated in  FIG. 5 , the two second flange protrusion portions F 2  include two linear portions F 5  parallel with the longitudinal direction L. The linear portions F 5  are preferably the portions projecting the most in the lateral direction S. Also, both ends of the two linear portions F 5  preferably connect with two of the second flange recess portions F 4  of the four second flange recess portions F 4 . In other words, one second flange protrusion portion F 2  is preferably formed by one of the linear portions F 5  and two of the second flange recess portions F 4 . In this way, with the lower flange  56  including the second flange protrusion portion F 2  projecting greatly in the lateral direction S, the holding strength to prevent the stud pin  50  from falling out from the pin inserting hole  29  is increased. 
     The stud pin  50  including the flange profile shape  62  and the body profile shape  64  with an anisotropic shape is installed in a tire.  FIGS. 6A and 6B  are diagrams illustrating the orientation of the stud pin  50  installed in the tire. 
       FIG. 6A  illustrates an example in which the stud pin is installed in the pin inserting hole  29  with the longitudinal direction L of the lower flange  56  facing the tire lateral direction W and the lateral direction S being aligned with the arrangement direction facing the tire circumferential direction C.  FIG. 6B  illustrates an example in which the stud pin is installed in the pin inserting hole  29  with the lateral direction S of the lower flange  56  facing the tire lateral direction W and the longitudinal direction L being aligned with the arrangement orientation of the stud pin  50  facing the tire circumferential direction C. 
     As illustrated in  FIG. 6A , when the stud pin  50  is disposed with the lateral direction S corresponding to the tire circumferential direction C, the stud pin  50  that receives a lateral force as sheer force inclines, collapsing in the pin inserting hole  29 . However, the stud pin  50  is tightly fastened by the tread rubber  18  deformed corresponding to the undulations formed by the four first flange protrusion portions F 1  of the lower flange  56  at the inner wall surface of the pin inserting hole  29 . Thus, a gap is not easily formed (does not come loose) between the stud pin  50  and the pin inserting hole  29  due to the stud pin  50  inclining in the tire lateral direction W. Accordingly, the stud pin  50  does not easily rotate in the pin inserting hole  29  and is suppressed from falling out from the pin inserting hole  29 . Also, the lateral force is efficiently transferred from the stud pin  50  to the belt  14  via the tread rubber  18 , improving the response of the studded tire to lateral forces. Additionally, the second flange recess portion F 4  is the portion facing an inclined direction with respect to the tire lateral direction W. Thus, even when turning with braking/driving engaged, when the orientation of the lateral force received by the stud pin  50  is inclined, the inner wall surface of the pin inserting hole  29  fastens around the protrusion portions (the first flange protrusion portions F 1  and the second flange protrusion portions F 2 ) on either side of the second flange recess portion F 4  and the second flange recess portion F 4 . This improves the response of the studded tire to lateral forces. As described above, the pin drop resistance when turning and controllability on snowy and icy road surfaces are improved. Furthermore, the flange profile shape  62  of the lower flange  56  includes the large second flange protrusion portion F 2  facing the tire circumferential direction C. This increases the holding strength to prevent the movement of the stud pin  50  to incline and fall out from the pin inserting hole when the stud pin  50  receives a large breaking or accelerating force when breaking or driving. As a result, braking and driving properties on icy road surfaces is improved, as well as pin drop resistance when breaking or driving. Furthermore, the stud pin  50  functions with the lateral direction S of the body profile shape  64 , the four first body protrusion portions B 1  facing the tire circumferential direction C, the longitudinal direction L, and the two second body protrusion portions B 2  facing the tire lateral direction W supplementing the function of the longitudinal direction L of the flange profile shape  62 , the four first flange protrusion portions F 1  facing the tire lateral direction W, the lateral direction S, and the two second flange protrusion portions F 2  facing the tire circumferential direction C. Thus, when a shear force such as a breaking or accelerating force or a lateral force is received by the stud pin  50 , rotation of the stud pin, which is an initial cause of falling out is suppressed, and the holding force that prevents the stud pin  50  from inclining and moving out from the pin inserting hole is increased. 
     As illustrated in  FIG. 6B , when the stud pin  50  is disposed with the longitudinal direction L corresponding to the tire circumferential direction C, the stud pin  50  that receives braking force and driving force as sheer force inclines, collapsing in the pin inserting hole  29 . However, the stud pin  50  is tightly fastened by the tread rubber  18  deformed corresponding to the undulations formed by the four first flange protrusion portions F 1  of the lower flange  56  at the inner wall surface of the pin inserting hole  29 . Thus, a gap is not easily formed (does not come loose) between the stud pin  50  and the pin inserting hole  29  due to the stud pin  50  inclining in the tire circumferential direction from the icy road surface. Accordingly, the stud pin  50  does not easily rotate in the pin inserting hole  29  and is suppressed from falling out from the pin inserting hole  29 . Also, the breaking or accelerating force is efficiently transferred from the stud pin  50  to the belt  14  via the tread rubber  18 , improving the response of the studded tire to breaking or accelerating forces. In other words, the braking ability on ice is improved. Additionally, the second flange recess portion F 4  is the portion facing an inclined direction with respect to the tire lateral direction W. Thus, even when breaking or accelerating with a slip angle, if the orientation of the breaking or accelerating force received by the stud pin  50  is inclined, the inner wall surface of the pin inserting hole  29  tightly fastens around the protrusion portions (the first flange protrusion portions F 1  and the second flange protrusion portions F 2 ) on either side of the second flange recess portion F 4  and the second flange recess portion F 4 . This improves the response of the studded tire to breaking and accelerating. As described above, the pin drop resistance when breaking or accelerating and braking and driving properties on snowy and icy road surfaces are improved. Furthermore, the flange profile shape  62  of the lower flange  56  includes the large second flange protrusion portion F 2  facing the tire tire lateral direction W. This increases the holding strength to prevent the movement of the stud pin  50  to incline and fall out from the pin inserting hole when the stud pin  50  receives a large lateral force when turning. As a result, controllability on icy road surfaces is improved, as well as pin drop resistance when turning. Furthermore, the stud pin  50  functions with the lateral direction S of the body profile shape  64 , the four first body protrusion portions B 1  facing the tire lateral direction W, the longitudinal direction L, and the two second body protrusion portions B 2  facing the tire circumferential direction C supplementing the function of the longitudinal direction L of the flange profile shape  62 , the four first flange protrusion portions F 1  facing the tire circumferential direction C, the lateral direction S, and the two second flange protrusion portions F 2  facing the tire lateral direction W. Thus, when a shear force such as a breaking or accelerating force or a lateral force is received by the stud pin  50 , rotation of the stud pin, which is an initial cause of falling out is suppressed, and the holding force that prevents the stud pin  50  from inclining and moving out from the pin inserting hole is increased. 
     According to an embodiment, the orientation of the stud pin  50  installed in an inner region near the tire equator line CL of the tread portion is preferably set as the orientation illustrated in  FIG. 6A  or  FIG. 6B , and the orientation of the stud pin  50  installed in an outer region outward from the inner region in the tire lateral direction is preferably set as the orientation illustrated in the other  FIG. 6A  or  FIG. 6B . The degree of the effect on braking and driving properties and controllability depends on the position on the tread portion in the tire lateral direction. Thus, to efficiently improve braking and driving properties and controllability, the orientation of the stud pin  50  illustrated in  FIG. 6A  or  FIG. 6B  is preferably selectively selected depending on the position in the tire lateral direction where the stud pin  50  is installed. 
     Examples, Conventional Example, and Comparative Examples 
     Stud pins including lower flanges with different profile shapes were manufactured. The manufactured stud pins were embedded in tires  10  with the configuration illustrated in  FIGS. 1 to 3  to manufacture studded tire. These studded tires were mounted to a passenger vehicle test vehicle, and the stud pins were evaluated. 
     The size of each manufactured tire was 205155R16. The passenger vehicle used was a front-wheel drive sedan with an engine displacement of 2000 cc. The internal pressure condition of the tires was 230 (kPa) for both the front wheels and rear wheels. The load condition of the tires was a 450 kg load on the front wheels and a 300 kg load on the rear wheels. The evaluation items for the stud pins are as follows. 
     Pin Drop Resistance 
     The proportion (%) of the number of stud pins remaining in the tread rubber to the total number of installed stud pins was obtained after a test vehicle had travelled 15000 km on a dry road surface including asphalt road surfaces or concrete road surfaces. A proportion of 95% or greater is evaluated as there being no practical problem with regard to pin drop. 
     Braking Ability on Ice 
     The test vehicle was driven on an icy road surface, and the travel distance taken upon engaging braking for the test vehicle to go from a speed of 30 km/h to 5 km/h was measured as the braking distance. The reciprocal of the braking distance of the Conventional Example was assigned as a reference (index value of 100) and the reciprocals of the braking distances of the Examples are expressed as index values. Larger index values indicate shorter braking distance and superior braking ability on ice. 
     Controllability on Ice 
     Two evaluator drivers drove the test vehicle on an icy road surface of a conditioned closed course and performed a subjective evaluation of controllability. The two scores were averaged and expressed as index values with the score of the Conventional Example being assigned as the reference (index value of 100). Larger index values indicate superior controllability on ice. 
     Tables 1 and 2 show the various parameters and evaluation results of the Conventional Example, Comparative Examples, and Examples. 
     “Shape of first and second smallest rectangle circumscribing profile shape” in Tables 1 and 2 refers to the shape of either the first or second smallest rectangle illustrated in  FIG. 4B . For the Conventional Example, “circle” refers to the profile shape of the lower flange and not the shape of the first and second smallest rectangle. For Comparative Examples 3 and 4 and the Examples, the ratio of the length of the short side to the length of the long side of the “rectangle” is 1:1.13. 
     In the “protrusion number (first flange protrusion portion F 1 , second flange protrusion portion F 2 )” in Tables 1 and 2, in the case of the number of first flange protrusion portions F 1  being even, the number protruding in the direction on both sides in the longitudinal direction was the same. The number of the second flange protrusion portions F 2  is even, and the number protruding in either direction of the lateral direction S is the same. When the number of the first flange protrusion portions F 1  is three, the number protruding in the direction on both sides of the longitudinal direction was 2 and 1, and when the number of first flange protrusion portions F 1  is 5, the number protruding in the direction on both sides in the longitudinal direction was 3 and 2. 
     In “Recess depth of first flange recess portion F 3 &gt; or = or &lt; recess depth of second flange recess portion F 4 ” in Tables 1 and 2, “F 3 =F 4 ” indicates that the recess depths are equal, “F 3 &gt;F 4 ” indicates that the recess depth of the first flange recess portion F 3  is greater than the recess depth of the second flange recess portion F 4 , and “F 3 &lt;F 4 ” indicates that the recess depth of the second flange recess portion F 4  is greater than the recess depth of the first flange recess portion F 3 ″. 
     In “body profile shape of upper flange” in Tables 1 and 2, “circle” means that the body profile shape as viewed from the H-direction is circular, and “ FIG. 4B ” means that the body profile shape is the body profile shape  64  illustrated in  FIG. 4B . 
     Here, in Comparative Examples 1 and 4 in which the number of first flange protrusion portions F 1  is two, no first flange recess portions F 3  are provided. In this case, the recess depth of the second flange recess portion F 4  is defined as the recess depth of the second flange recess portion F 4  in Comparative Examples 2, 3. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Conventional 
                 Comparative 
                 Comparative 
                 Comparative 
                 Comparative 
               
               
                   
                 Example 
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 4 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Shape of first and 
                 Circle 
                 Square 
                 Square 
                 Rectangle 
                 Rectangle 
               
               
                 second smallest 
               
               
                 rectangle 
               
               
                 circumscribing profile 
               
               
                 shape 
               
               
                 Protrusion number 
                 — 
                 2, 2 
                 4, 2 
                 3, 2 
                 2, 4 
               
               
                 (first flange protrusion 
               
               
                 portion F1, second 
               
               
                 flange protrusion 
               
               
                 portion F2) 
               
               
                 Recess depth of first 
                 — 
                 — 
                 F3 = F4 
                 F3 = F4 
                 — 
               
               
                 flange recess portion 
               
               
                 F3 &gt; or = or &lt; 
               
               
                 recess depth of second 
               
               
                 flange recess portion F4 
               
               
                 Linear portion F5 
                 — 
                 Yes 
                 Yes 
                 Yes 
                 Yes 
               
               
                 Body profile shape of 
                 Circle 
                 FIG. 4B 
                 FIG. 4B 
                 FIG. 4B 
                 FIG. 4B 
               
               
                 upper flange 
               
               
                 Pin drop resistance (%) 
                 55 
                 90 
                 92 
                 94 
                 94 
               
               
                 Braking ability on ice 
                 100 
                 102 
                 103 
                 104 
                 102 
               
               
                 Controllability on ice 
                 100 
                 101 
                 102 
                 102 
                 102 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 4 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Shape of first and second smallest 
                 Rectangle 
                 Rectangle 
                 Rectangle 
                 Rectangle 
               
               
                 rectangle circumscribing profile 
               
               
                 shape 
               
               
                 Protrusion number (first flange 
                 4, 2 
                 5, 2 
                 4, 2 
                 4, 2 
               
               
                 protrusion portion F1, second 
               
               
                 flange protrusion portion F2) 
               
               
                 Recess depth of first flange recess 
                 F3 = F4 
                 F3 = F4 
                 F3 &gt; F4 
                 F3 &gt; F4 
               
               
                 portion F3 &gt; or = or &lt; 
               
               
                 recess depth of second flange 
               
               
                 recess portion F4 
               
               
                 Linear portion F5 
                 Yes 
                 Yes 
                 Yes 
                 No 
               
               
                   
                   
                   
                   
                 (convex arc shape) 
               
               
                 Body profile shape of upper 
                 FIG. 4B 
                 FIG. 4B 
                 FIG. 4B 
                 FIG. 4B 
               
               
                 flange 
               
               
                 Pin drop resistance (%) 
                 97 
                 98 
                 100 
                 100 
               
               
                 Braking ability on ice 
                 106 
                 108 
                 108 
                 106 
               
               
                 Controllability on ice 
                 104 
                 105 
                 105 
                 104 
               
               
                   
               
            
           
         
       
     
     As seen from comparing the Conventional Example, Comparative Examples 1 to 4, and Examples 1 to 4, a configuration in which the flange profile shape  62  has an anisotropic shape with the first smallest rectangle or the second smallest rectangle circumscribing the flange profile shape  62  being a rectangle, the body profile shape  64  has an anisotropic shape with the length of the body profile shape  64  in the lateral direction S of the rectangle being different from the length of the body profile shape  64  in the longitudinal direction L, the profile shape  62  includes four or more first flange protrusion portions F 1  projecting toward the longitudinal direction L and two second flange protrusion portions F 2  projecting toward the lateral direction S, and the body profile shape  64  includes four or more first body protrusion portions B 1  projecting toward the lateral direction S and two second body protrusion portions B 2  projecting toward the longitudinal direction L has improved pin drop resistance compared to the Conventional Example and Comparative Examples 1 to 4. Furthermore, braking ability on ice and controllability on ice is improved compared to the Conventional Example and Comparative Examples 1 to 4. 
     As seen from comparing Examples 2 and 3, a configuration in which the recess depth of the first flange recess portion F 3  and the recess depth of the second flange recess portion F 4  being equal poses no problems in terms of the evaluation result, however a configuration in which the recess depth of the first flange recess portion F 3  is greater than the recess depth of the second flange recess portion F 4  has improved pin drop resistance. 
     A stud pin and a studded tire according to an embodiment of the present technology have been described above. However, it should be understood that the present technology is not limited to the above embodiments and examples, and may be improved or modified in various ways so long as these improvements or modifications remain within the scope of the present technology.