JP6023424B2 - Studded tires - Google Patents

Description

  The present invention relates to a studded tire in which a stud embedding hole for embedding a stud in a tire tread is formed.

2. Description of the Related Art Conventionally, a studded tire in which a stud made of metal (also called a spike) is driven into a land portion of a tread is known as a winter tire. FIG. 10A is a view showing an example of the stud 8, and the stud 8 is provided on the columnar body portion 8a and the bottom side of the body portion 8a (the side opposite to the tire tread surface side), and the diameter of the body portion 8a. A flange portion 8b for preventing slippage having a larger diameter, and a tip 8c protruding in the stud axial direction from the tire tread side end portion of the body portion 8a.
On the other hand, as shown in FIG. 10 (b), a stud 9 is formed in the block 5 which is a land portion of the tread, and the stud 8 is formed by blocking the tip 8c and the uppermost portion of the body portion 8a. 5 is driven into the stud-embedding hole 9 so as to protrude from the surface of 5.
The stud-embedding hole 9 has a cylindrical shaft portion 9a having a diameter Dp smaller than the diameter Pd of the body portion 8a of the stud 8, and a diameter Df smaller than the diameter Fd of the flange portion 8b of the stud 8. A head portion 9b provided on the inner side in the tire radial direction of the shaft portion 9a, and the stud 8 is studded by fastening the body portion 8a and the flange portion 8b of the stud 8 with rubber around the shaft portion 9a and the head portion 9b. Hold in the hole 9 for burying.
When a vehicle equipped with such a studded tire travels on a snowy icy road, the tip of the stud 8 bites into the road surface, and the frictional force between the road surface and the tire increases. can do.

By the way, when a vehicle equipped with a studded tire travels on an icy road surface, a large external force acts on the stud and the stud may come off, so-called stud removal may occur.
Therefore, a stud pin slit having a depth of 3 to 7.5 mm is provided around the hole for embedding the stud so as to surround the hole for embedding the stud so that the stud moves integrally with the surrounding rubber. Thus, there has been proposed a method for reducing the external force applied to the stud and improving the resistance to pulling out the stud (for example, see Patent Document 1).
In addition, the block in which the stud is embedded is provided with a recess that opens to the groove side at one end and extends to the vicinity of the stud hole at the other end, and guides and eliminates ice fragments generated when the stud and ice are scratched. Thus, a method has been proposed in which the gripping force of the stud is ensured and the resistance to pulling out the stud is improved by increasing the pull-out resistance of the stud (for example, see Patent Document 2).

JP 2008-230259 A Special table 2011-521844 gazette

However, in the cited document 1, the stud is easy to move integrally with the surrounding rubber, but conversely, the amount of collapse of the block when the braking / driving force is applied increases, so that the steering stability performance decreases. In addition, the amount of falling of the stud is increased, and as a result, the stud is easily pulled out, so that the resistance to pulling out the stud is not improved so much.
Further, in the cited document 2, the fixing force of the stud to ice is increased, but the block surface is partitioned by the concave portion, so that the amount of collapse of the block is increased as in the cited document 1, and the steering stability performance is lowered. There was a problem such as.

  The present invention has been made in view of the conventional problems, and provides a studable tire excellent in anti-stud pullout resistance and steering stability performance on an icy road, in which the amount of stud collapse during braking / driving is reduced. For the purpose.

The present invention has a columnar body portion and a flange portion in a land portion of a tire tread, and embeds a stud having the same shape as viewed from the tire circumferential direction when viewed from the tire width direction. A stud-embedded tire in which a stud-embedded hole is formed, wherein the stud-embedded hole has a columnar shaft portion corresponding to the body portion of the stud, and a head portion corresponding to the flange portion of the stud, When the shape of the head part when viewed from the tire radial direction is a cross section of the tire width direction and the tire circumferential direction, the tire width direction has a long dimension, the tire circumferential direction has a short dimension, parallel to the central axis in the tire radial direction of the shaft portion, the central axis of the shaft portion when viewed from the tire radial direction, with respect to the center of the head portion, the depression at the time of forward rotation of the tire Or characterized in that it shifted to kick out side.
Thus, by providing anisotropy to the shape of the head portion of the stud embedding hole, the tire circumferential direction that acts on the flange portion of the stud as compared to the conventional isotropic stud embedding hole The tightening force can be increased. Therefore, the amount of the stud falling during braking / driving can be reduced, and both the resistance to pulling out the stud and the steering stability performance on the icy road can be improved.
Also, the central axis of the shaft portion is parallel to the tire radial direction, the central axis of the shaft portion when viewed from the tire radial direction, with respect to the center of the head portion, the depression at the time of forward rotation of the tire The drive performance or braking performance can be further improved by setting the central axis of the shaft portion to the stepping side or the kicking side depending on the target performance of the vehicle. it can.
That is, when starting or driving, the stud falls to the stepping side of the block, so in addition to adding anisotropy to the shape of the head part, a hole for embedding the stud is made so that the central axis of the shaft part is on the stepping side. If it is formed, the amount of stud falling to the block stepping side can be reduced, and it will fall to the block kicking side during braking. Therefore, if the central axis of the shaft is on the kicking side, the stud block kicking The amount of falling to the exit side can be reduced.
In the present invention, the shape of the head portion when viewed from the tire radial direction is an ellipse whose major axis direction is parallel to the tire width direction, or a track shape in which the linear portion is orthogonal to the tire circumferential direction, or It is a polygon that is inscribed or circumscribed to the ellipse and that is symmetrical with respect to the major axis and minor axis of the ellipse.
As a result, the tightening force acting on the stud flange portion increases from the tire width direction toward the tire circumferential direction and becomes maximum in the tire circumferential direction, so that the stud flange portion has the shape of the head portion of the stud embedding hole. Anisotropy that increases the tightening force in the tire circumferential direction acting on the tire can be reliably imparted.
The term “parallel to the tire width direction” as used in the present application does not mean perfectly parallel mathematically, but is about 30 ° due to a deviation of several degrees or a pattern, that is, due to the convenience of other grooves and sipes. This difference shall be allowed.

In the present invention, the length of the short axis of the ellipse is Dx, the length of the long axis is Dy, the distance between the central axis of the shaft portion and the stepped end of the head portion is Rf, and the shaft portion Rk and Rk satisfy the following conditional expression, where Rk is the distance between the central axis of the head and the end of the head portion on the kicking side and Ds is the diameter of the shaft portion: To do.
(Ds / 2) <Rf <(Dy / 2) and (Ds / 2) <Rk <(Dy / 2)
However, Dx = Rf + Rk
As a result, it is possible to avoid a situation in which the distance between the center axis of the flange portion of the stud and the center axis of the head portion of the hole for embedding the stud becomes large, and the stud does not enter the depth of the hole. Can be improved with certainty.
In the stud embedding hole of the present invention, since Ds <Dx <Dy, when the central axis of the shaft portion is at the center of the ellipse (Rf = Rk), the above condition is naturally satisfied. .

The invention of the present application is characterized in that the shape of the stud embedded in the stud embedding hole when viewed from the tire circumferential direction is the same as the shape when viewed from the tire width direction.
As a result, for example, a stud having a normal isotropic shape and structure in which the flange portion is a disk shape coaxial with the body portion can be used. Can be reduced. In addition, if the stud does not have anisotropy, the effect of the invention can be achieved without worrying about the angle at which the stud is driven, compared to the case where the stud itself has anisotropy. Can be obtained.

  The summary of the invention does not list all necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

It is a figure which shows an example of the tread pattern of the studable tire which concerns on Embodiment 1 of this invention. It is a figure which shows the hole for stud embedding concerning this Embodiment 1. FIG. It is a figure which shows the relationship between the hole for stud embedding, and a stud. It is a figure for demonstrating the motion of the stud at the time of braking / driving. It is a figure which shows the hole for stud embedding concerning this Embodiment 2. FIG. It is a figure which shows the hole for stud embedding concerning this Embodiment 3. FIG. It is a figure which shows the other shape of the hole for stud embedding. It is a table | surface which shows the result of an actual vehicle test. It is a figure which shows the shape of the hole for stud embedding used for the actual vehicle test. It is a figure which shows an example of the hole for the conventional stud and stud embedding.

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

Embodiment 1 FIG.
FIGS. 1 and 2 are views showing the first embodiment, FIG. 1 is a view showing a tread pattern of a studded tire 1 according to the present invention, and FIG. 2 is a view showing a hole 10 for embedding a stud.
The stackable tire 1 includes a circumferential groove 2 formed in a tire tread, a lug groove 3 formed so as to intersect the circumferential groove 2, and a plurality of blocks partitioned by the circumferential groove 2 and the lug groove 3 4-6. The block 4 is a central block constituting the central block row 4L disposed along the tire circumferential direction in the tire center portion including the center line indicated by CL in the same figure, and the block 5 is in the tire width direction than the central block row 4L. The outer block, block 6, constituting the outer block row 5L located on the outer side is a shoulder block located on the tire shoulder portion.
A plurality of sipes 7 are formed on the tread surface side of each of the blocks 4 to 6, and stud embedding holes for embedding studs 8 in regions where the sipes 7 are not formed in the substantially central portion of the outer block 5. (Hereinafter referred to as a stud hole) 10 is formed.

As shown in FIGS. 2A and 2B, the stud hole 10 includes a shaft portion 11 located on the tread surface side of the outer block 5 and a head portion 12 located on the inner side in the tire radial direction of the shaft portion 11. .
The shaft portion 11 is a cylindrical gap having a diameter Ds.
The head part 12 is an elliptical gap whose major axis direction is parallel to the tire width direction when viewed from the tire radial direction, and the shaft part 11 and the head part 12 are inside the tire radial direction of the shaft part 11. It communicates with the end of the.
Here, when the length of the minor axis of the ellipse is Dx and the length of the major axis is Dy, the magnitudes of Ds, Dx, and Dy are Ds <Dx <Dy.
Further, the central axis of the shaft portion 11 is parallel to the tire radial direction, and the central axis of the shaft portion 11 coincides with the central axis of the head portion 12 (an axis parallel to the central axis of the shaft portion 11 passing through the center of the ellipse). ing.

3A and 3B are views showing the relationship between the stud hole 10 and the stud 8.
As shown in FIG. 3A, when viewed in a cross section perpendicular to the tire circumferential direction, the length Fd of the flange portion 8b of the stud 8 and the maximum hole diameter of the head portion 12 of the stud hole 10 in the tire width direction. The relationship with the shaft length Dy is the same as the relationship between the diameter Fd of the flange portion 8b of the conventional stud 8 and the diameter Df of the head portion 9b of the stud hole 9, and (Dy / Fd) = (Df / Fd) 0.3 to 0.5.
On the other hand, as shown in FIG. 3B, when viewed in a cross section perpendicular to the tire width direction, the short axis length Dx which is the maximum hole diameter in the tire width direction of the head portion 12 of the stud hole 10 is the long axis. Therefore, (Dx / Fd) <(Df / Fd). In other words, since the stud hole 10 of the first embodiment is provided with anisotropy in the shape of the head portion 12, the stud hole 10 has a shape relative to the flange portion 8b of the stud 8 as compared with the conventional isotropic stud hole 9. The tightening force in the tire circumferential direction is large.
The relationship between the diameter Pd of the body portion 8a of the stud 8 and the diameter Ds of the shaft portion 11 of the stud hole 10 is the same as the diameter Pd of the body portion 8a of the conventional stud 8 and the diameter Dp of the shaft portion 9a of the stud hole 9. (Ds / Pd) = (Dp / Pd) = 0.3 to 0.5. In FIG. 3 and FIGS. 5, 6, and 10 shown below, the stud holes are drawn larger in order to make the drawings easier to see.

Next, the movement of the stud 8 during starting / driving and braking will be described.
It is generally said that the stud comes off when starting and driving, and when a large driving force is applied to the tire. At this time, as shown in FIG. 4A, the stud portion 8b receives a force fb in the direction opposite to the vehicle traveling direction from the road surface, and the body portion 8a receives a force fa in the vehicle traveling direction from the road surface. As a result, the stud 8 falls down so as to rotate in the direction indicated by the arrow in FIG. That is, the stud 8 falls in the direction opposite to the vehicle traveling direction (the stepping side of the outer block 5). When this amount of tilting increases, the driving performance decreases, and furthermore, the stud 8 is easily pulled out from the outer block 5.
On the other hand, as shown in FIG. 4B, at the time of braking, the flange portion 8b receives a force f′b in the vehicle traveling direction, which is the direction in which the tire slides from the road surface, and the body portion 8a is opposite to the vehicle traveling direction from the road surface. Since the direction force f′a is received, the stud 8 falls in the vehicle traveling direction (the kicking side of the outer block 5), and as a result, not the edge of the body portion 8a but the side surface comes into contact with the ground and the braking performance decreases. To do.

In Embodiment 1, the stud hole 10 is provided with anisotropy that reduces the maximum hole diameter in the tire circumferential direction of the head portion 12, so that the tightening force in the tire circumferential direction on the flange portion 8 b of the stud 8 is increased. Therefore, even if the force fb opposite to the vehicle traveling direction or the vehicle traveling direction f′b acts, the falling of the stud 8 can be suppressed. Further, if the amount of collapse is small, the loss of braking / driving force due to the movement of the stud 8 is also reduced. Therefore, the stud pull-out resistance can be improved without reducing the braking / driving performance.
Further, in this example, only the shape of the stud hole 10 is changed, and unnecessary slits and grooves are not provided on the surface of the outer block 5 on which the stud hole 10 is provided. The slip-out property can be improved.
In addition, since the stud 8 used in the first embodiment is the same as the conventional stud in which the flange portion 8b is a disk shape coaxial with the body portion 8a, a new stud is designed in accordance with the shape change of the stud hole 10. There is an advantage that there is no need to do. Further, since the conventional stud 8 can be used without being processed, the cost can be reduced.

Embodiment 2. FIG.
In the first embodiment, the case where the shaft portion 11 of the stud hole 10 and the central axis of the head portion 12 coincide with each other has been described. However, as shown in FIGS. While maintaining the diameter Ds of the head portion 12, the length Dx of the ellipse minor axis of the head portion 12, and the length Dy of the major axis the same as in the first embodiment, the central axis of the shaft portion 11 is set to the outer block 5. By shifting to the step-in side, the stud pull-out resistance and driving performance can be further improved.
Specifically, the distance between the central axis of the shaft portion 11 and the end portion on the stepping side of the head portion 12 is Rf, and the distance between the central axis of the shaft portion 11 and the end portion on the kicking side of the head portion 12 is Rk. Rf <Rk (Rf + Rk = Dx).
As a result, it is possible to further increase the tightening force on the stepping side with respect to the flange portion 8 b of the stud 8, so that the amount of the stud 8 that falls when starting and driving is further smaller than that of the first embodiment. Accordingly, the pull-out resistance of the stud 8 is further improved, and the loss of driving force due to the movement of the stud 8 is reduced, so that the driving performance is also improved.

  If the distance Rk between the central axis of the shaft portion 11 and the end portion on the kicking side of the head portion 12 is too small, the center axis of the flange portion 8b of the stud 8 and the central axis of the head portion 12 of the stud hole 10 Since the distance becomes large and the stud cannot be inserted into the hole, it is easy for the stud to fall out, or the driving performance is improved but the braking performance may be lowered. Therefore, Rf is set to (Ds / 2 ) <Rf <(Dy / 2). Thereby, driving performance can be further improved while improving pull-out resistance.

Embodiment 3 FIG.
In the second embodiment, the case where the center axis of the shaft portion 11 is shifted to the stepping side of the outer block 5 has been described. Conversely, the center axis of the shaft portion 11 is shifted to the kicking side of the outer block 5. By doing so, it is possible to further improve the braking performance when traveling on an icy road.
One effective means for improving the braking performance is a method of scratching ice with the edge of a hard pin (chip 8c) without grounding the stud body (body portion 8a). Therefore, as shown in FIGS. 6A and 6B, if Rk <Rf, the tightening force on the kicking side with respect to the flange portion 8b of the stud 8 can be increased. It becomes smaller than the first embodiment. Therefore, since the stud 8 mainly scratches ice at the pin edge, the braking performance is improved.
However, since the tightening force on the stepping side with respect to the flange portion 8b is reduced, the pull-out resistance and the driving performance are improved as compared with the first embodiment, although they are improved as compared with the prior art.
Even in the third embodiment, if the distance Rf between the central axis of the shaft portion 11 of the stud hole 10 and the stepped-side end portion of the head portion 12 is too small, the tightening force to the shaft portion 11 increases. As a result, there is a risk that the stud will not be inserted into the hole, and as a result, there is a possibility that the stud will be easily pulled out, or that the braking performance may be improved but the driving performance may be reduced. It is preferable to set in the range of (Ds / 2) <Rk <(Dy / 2). Thereby, the braking performance can be further improved while improving the pull-out resistance.

In the first to third embodiments, the studded tire having a block pattern has been described. However, the present invention is also applicable to a tire having another tread pattern such as a rib pattern.
Further, the formation location of the stud hole 10 is not limited to the outer block 5, but may be provided in the central block 4 or the shoulder block 6, or in blocks of a plurality of block rows such as the outer block 5 and the shoulder block 6. Each may be provided.
Further, the stud holes 10 do not have to be provided in all the blocks of the block row, and may be provided in every other block or in plural.

In the first to third embodiments, the shape of the head portion 12 of the stud hole 10 when viewed from the tire radial direction is an ellipse whose major axis direction is parallel to the tire width direction. ) As shown in FIG. 7B or a polygon circumscribing the ellipse as shown in FIG. At this time, the polygon is preferably symmetrical with respect to the major axis and the minor axis of the ellipse. Further, the extending direction of the step side 12f and the extending direction of the kicking side 12k may both be parallel to the tire width direction (orthogonal to the tire circumferential direction), or may intersect the tire width direction. Also good.
Alternatively, the shape of the stud hole 10 is changed to a straight line portion composed of two sides 12p and 12q orthogonal to the tire circumferential direction as shown in FIGS. 7C and 7D, and two arc portions positioned in the tire width direction. 12r may be used as a track.
Further, as shown in FIGS. 7 (a) and 7 (c), the center axis of the shaft portion 11 and the center axis of the flange portion 12 are made to coincide with each other, or as shown in FIGS. 7 (b) and 7 (d), the shaft portion. Whether or not the center axis 11 is shifted in the tire circumferential direction may be determined as appropriate according to the target performance of the tire.
In any case, when comparing the shape of the head portion of the stud hole when viewed from the tire radial direction with respect to the cross section of the tire width direction and the tire circumferential direction, the dimension in the tire width direction is long and the dimension in the tire circumferential direction is By making the stud hole short enough to give the stud hole anisotropy that increases the tightening force in the tire circumferential direction, the amount of stud collapse during braking / driving can be reduced, and the stud pull-out resistance And the stability of handling on an icy road can be improved.

[Example]
Studable tires (Examples 1 to 6) in which isotropic studs are embedded in the anisotropic stud holes of the present invention are prepared, and each tire is mounted on a test vehicle and driving performance and braking performance are obtained. The results of examining the durability performance are shown in the table of FIG.
For comparison, a conventional studable tire (conventional example) in which an isotropic stud hole is embedded in an isotropic stud hole and the head portion is isotropic but the central axis of the shaft portion A similar test was also performed on a studded tire (comparative example) in which the head portion deviates from the center of the head portion toward the kicking side.
The tire size of the studded tire used for the test is 195 / 65R15, and the tire internal pressure is 230 kPa.
In the table of FIG. 8, the dimension of the stud hole is represented by an index with the value of the diameter Df of the stud hole of the conventional example being 100. Ri is the distance between the central axis of the shaft portion and the block equator side end portion of the head portion, Ro is the distance between the central axis of the shaft portion and the block anti-equatorial side end portion of the head portion. = Ro.

The shape of the head portion of the conventional example is a disk shape whose center axis is coaxial with the center axis of the shaft portion as shown in Type A of FIG.
The shape of the head part of Examples 1 and 4 is an elliptical plate shape in which the central axis is located on the step-in side with respect to the central axis of the shaft part as shown in Type B of FIG. It is longer than the ellipse of Example 1.
The shape of the head part in Examples 2 and 5 is an elliptical plate shape in which the central axis is located on the kicking side from the central axis of the shaft part as shown in Type C of FIG. Is longer than the ellipse of the second embodiment.
The shape of the head part of Examples 3 and 6 is an elliptical plate shape whose center axis is coaxial with the center axis of the shaft part as shown in Type D of FIG. 9, and the ellipse of Example 6 is the same as that of Example 3. Longer than an ellipse.
The shape of the head portion of the comparative example is a disk shape whose center axis is located on the kicking side with respect to the center axis of the shaft portion as shown in Type E of FIG.
In any tire, the shape of the shaft portion is cylindrical.
The tires used in the tests all have a cylindrical shaft portion and satisfy the relationship of (Ds / 2) <Rf, Rk <(Dy / 2).
In addition, although tires in which Rf and Rk do not satisfy the conditional expression (Ds / 2) <Rf <(Dy / 2) and (Ds / 2) <Rk <(Dy / 2) are also produced, The test was not conducted because there were many studs that were not fully inserted.

The driving performance was evaluated by measuring the time required for the test vehicle to accelerate from a stopped state until the vehicle speed reached 20 km / hr on the icy road surface, and the length of the arrival time was indexed. The drive performance index in the table is an index with the arrival time of the conventional example as 100, and the smaller the numerical value, the shorter the arrival time and the better the drive performance.
The braking performance was evaluated by measuring the braking distance from a test vehicle running at a constant speed of 20 km / hr on an icy road surface until it suddenly brakes and stopping, and indexing the length of the braking distance. The braking performance index in the table is represented by an index with the braking distance of the conventional example as 100. The smaller the numerical value, the shorter the braking distance and the better the braking performance.
Durability performance was evaluated by a removal rate which is a value obtained by dividing the number of studs removed after running the test vehicle for 10,000 km by the number of studs before running. The stud pull-out index in the table is expressed as an index with the pull-out ratio of the conventional example as 100, and the smaller the value, the lower the pull-out ratio and the better the durability performance (stud pull-out resistance).

As shown in the table of FIG. 8, in the tire of Example 3, both the driving performance and the braking performance are superior to the conventional example, and the stud pull-out index is small, so that the durability is also improved compared to the conventional example. I understand that.
In the tire of Example 1, the driving performance is further improved as compared with the tire of Example 3, and the braking performance is inferior to that of Example 3 but is improved over the conventional example.
In the tire of Example 2, the driving performance is further improved as compared with the tire of Example 3, and the braking performance and durability performance are inferior to those of the tire of Example 3, but improved compared to the conventional example.
In addition, as can be seen by comparing the tire of Example 1 and the tire of Example 4, the tire of Example 2 and the tire of Example 5, the tire of Example 3 and the tire of Example 6, (Dx / Dy ) Decreases, that is, when the anisotropy increases, the driving performance and the braking performance increase, and the durability performance also improves.

On the other hand, as in the comparative example, even when the central axis is positioned on the kicking side with respect to the central axis of the shaft portion, the driving performance is improved, but the braking performance is lower than the conventional one.
Therefore, it was confirmed that both the anti-stud pull-out resistance and the steering stability performance on the icy road can be improved by adding anisotropy that increases the circumferential tightening force to the shape of the head portion of the stud hole. It was.
In addition, if anisotropy is given to the shape of the head part of the stud hole and the central axis of the shaft part is set to the stepping side, the driving performance can be further improved, and the central axis of the shaft part is set to the kicking side. It has also been confirmed that the braking performance can be further improved if this is done.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the embodiment. It is apparent from the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  Thus, according to the present invention, the amount of stud collapse during braking / driving can be reduced, so that it is possible to provide a studded tire that is excellent in stud pull-out resistance and steering stability performance on an icy road.

1 studded tire, 2 circumferential grooves, 3 lug grooves, 4 central block,
5 outer blocks, 6 shoulder blocks, 7 sipes, 8 studs,
8a body part, 8b flange part, 8c tip,
10 Stud embedding hole (Stud hole), 11 Shaft part, 12 Head part,
CL Center line.

Claims (3)

For stud embedding to embed a stud in the land portion of the tire tread that has a columnar body portion and a flange portion, and the shape when viewed from the tire circumferential direction is the same as the shape when viewed from the tire width direction A studded tire in which a hole is formed,
The stud burying hole has a columnar shaft portion corresponding to the body portion of the stud, and a head portion corresponding to the flange portion of the stud ,
The shape of the head part when viewed from the tire radial direction is
When comparing the cross section of the tire width direction and the tire circumferential direction,
The tire width direction has long dimensions, the tire circumferential direction has short dimensions,
The central axis of the shaft portion is parallel to the tire radial direction,
A studded tire characterized in that a central axis of the shaft portion when viewed from the tire radial direction is deviated from a center of the head portion to a stepping-in side or a kicking-out side during normal rotation of the tire. .   The shape of the head part when viewed from the tire radial direction is
An ellipse whose major axis is parallel to the tire width direction,
Alternatively, a track shape in which the straight portion is orthogonal to the tire circumferential direction,
The studded tire according to claim 1, wherein the tire is a polygon that is inscribed or circumscribed to the ellipse and that is symmetrical with respect to a major axis and a minor axis of the ellipse. The length of the ellipse short axis is Dx, the length of the long axis is Dy, the distance between the central axis of the shaft portion and the end of the stepped side of the head portion is Rf, the central axis of the shaft portion and the head 3. The Rf and the Rk satisfy the following conditional expression, where Rk is a distance from an end portion on the kicking side of the portion and Ds is a diameter of the shaft portion. Studded tires.
(Ds / 2) <Rf <(Dy / 2) and (Ds / 2) <Rk <(Dy / 2)
However, Dx = Rf + Rk

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