JP6539563B2

JP6539563B2 - tire

Info

Publication number: JP6539563B2
Application number: JP2015204950A
Authority: JP
Inventors: 智明伊藤
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 2015-10-16
Filing date: 2015-10-16
Publication date: 2019-07-03
Anticipated expiration: 2035-10-16
Also published as: JP2017074926A

Description

本発明は、スタッドが取付けられる取付穴をトレッドの表面側に備えたタイヤに関する。 The present invention relates to a tire provided with mounting holes on which the studs are mounted on the surface side of the tread.

スタッダブルタイヤ（スパイクタイヤと呼ばれる場合もある）は、図８に示すように、タイヤ金型５０から突出するように設けられたスタッド取付穴形成用突起５１を加硫前のタイヤ１Ａにおけるトレッド１４の表面１４ａ側からトレッド１４の内側に挿入した状態でタイヤ１Ａを加硫し（図８（ａ）；（ｂ）参照）、タイヤ１Ａを加硫した後にスタッド取付穴形成用突起５１をトレッド１４から脱型して形成された取付穴５２に図外のスタッドが打ち込まれることで、スタッドの一端側がタイヤのトレッド１４の表面１４ａから突出するようにスタッドが取付穴５２に取付けられて形成される。
タイヤ金型５０は、タイヤ周方向に沿って例えば９分割されたものが使用される。
また、スタッド取付穴形成用突起５１は、形成する取付穴５２に対応した形状に形成される。
取付穴５２は、トレッド１４の表面１４ａに開口する開口側部と底側部とを備え、開口側部は、トレッド１４の表面１４ａから穴底面に向けて径寸法が徐々に小さくなる逆円錐形状に形成された穴入口側部と、穴入口側部と底側部とを繋ぐ円筒状の穴中間側部とを備える。
スタッド取付穴形成用突起５１は、取付穴５２の底側部を形成するための先端側が取付穴５２の穴中間側部を形成するための中間部よりも大径に形成されているため、タイヤ金型５０を脱型する場合、スタッド取付穴形成用突起５１をトレッド１４から引き抜く際の引き抜き抵抗によって取付穴５２の内周面からトレッドゴムにクラック（亀裂）が生じる虞がある。特に、タイヤ金型５０のタイヤ周方向に沿った両端に近いスタッド取付穴形成用突起５１ほど、図８（ｃ）に示すように、脱型時において、スタッド取付穴形成用突起５１の脱型方向５５と脱型により形成されるスタッド取付穴５２の中心軸５６とのずれ角度θが大きくなるため、脱型し難くなり、トレッドゴムにクラックが生じやすくなる。
そこで、スタッド取付穴形成用突起５１の形状を脱型しやすい形状にすることが考えられる。
しかしながら、スタッド取付穴形成用突起５１を脱型しやすい形状にすればスタッド取付穴に取付けられたスタッドも抜けやすくなる可能性がある。
即ち、スタッダブルタイヤは、使用時においては、スタッドが抜け難いこと、即ち、耐スタッド抜け性能が高いことが望ましいが、タイヤの加硫の際には、スタッド取付穴形成用突起５１がトレッド１４から脱型しやすいようにして、脱型時にトレッドゴムにクラックを発生させないこと、即ち、脱型性能が高いことが望ましい。
しかしながら、耐スタッド抜け性能と脱型性能とは背反した性能であるため、これら性能を両立させることは困難であった。
従来、スタッドが取付けられる取付穴をトレッドの表面側に備えたタイヤにおいて、トレッドの表面に開口する開口側部と、底側部とを備え、開口側部と底側部との境界部分における取付穴の中心軸に沿った曲面の曲率半径が、底側部の内周面における取付穴の中心軸に沿った曲面の曲率半径よりも小さく形成されたタイヤが知られている（特許文献１等参照）。 As shown in FIG. 8, the studdable tire (sometimes called a spike tire) has a stud mounting hole forming projection 51 provided so as to protrude from the tire mold 50, and the tread 14 in the tire 1A before vulcanization. The tire 1A is vulcanized in a state of being inserted inside the tread 14 from the surface 14a side of the tire (see FIG. 8 (a); (b)), and after the tire 1A is vulcanized The stud is inserted into the mounting hole 52 so that one end of the stud projects from the surface 14a of the tread 14 of the tire by driving the stud (not shown) into the mounting hole 52 formed by removing the mold. .
The tire mold 50 is, for example, one divided into nine along the tire circumferential direction.
Further, the stud attachment hole forming protrusion 51 is formed in a shape corresponding to the attachment hole 52 to be formed.
The mounting hole 52 has an open side and a bottom side opening to the surface 14 a of the tread 14, and the open side is an inverted conical shape in which the radial dimension gradually decreases from the surface 14 a of the tread 14 to the hole bottom And a cylindrical hole middle side connecting the hole inlet side and the bottom side.
The stud mounting hole forming projection 51 is formed so that the tip end side for forming the bottom side portion of the mounting hole 52 is larger in diameter than the middle portion for forming the hole middle side portion of the mounting hole 52. When the mold 50 is removed, a crack may be generated in the tread rubber from the inner peripheral surface of the mounting hole 52 due to the drawing out resistance when the stud mounting hole forming projection 51 is drawn out from the tread 14. In particular, as shown in FIG. 8 (c), the projections 51 for forming the stud attachment holes closer to both ends of the tire mold 50 along the circumferential direction of the tire are removed as the projections 51 for forming the stud attachment holes. Since the shift angle θ between the direction 55 and the central axis 56 of the stud attachment hole 52 formed by mold removal increases, mold removal becomes difficult, and cracks easily occur in the tread rubber.
Therefore, it is conceivable to make the shape of the stud attachment hole forming protrusion 51 easy to be removed from the mold.
However, if the stud attachment hole forming protrusion 51 is shaped so as to be easily removed, the stud attached to the stud attachment hole may be easily removed.
That is, it is desirable that the studd tire is hard to come off of the stud during use, that is, it has high anti-stud performance, but when the tire is vulcanized, the projection 51 for forming the stud attachment hole is the tread 14 It is desirable that the tread rubber not be cracked during demolding, that is, that the demolding performance is high.
However, since the anti-stud performance and the anti-mold performance are contrary to each other, it has been difficult to achieve both of these performances.
Conventionally, in a tire provided with attachment holes to which studs are attached, the tire is provided with an open side opening to the surface of the tread and a bottom side, and attachment at the boundary between the open side and the bottom side A tire is known in which the radius of curvature of the curved surface along the central axis of the hole is smaller than the radius of curvature of the curved surface along the central axis of the mounting hole in the inner peripheral surface of the bottom side (Patent Document 1 etc. reference).

特開２０１０−７００５２号公報JP, 2010-70052, A

特許文献１に開示された取付穴は、開口側部と底側部との境界部分における取付穴の中心軸に沿った曲面の曲率半径が、底側部の内周面における取付穴の中心軸に沿った曲面の曲率半径よりも小さく形成されているため、脱型時において、スタッド取付穴形成用突起が曲率半径の小さい境界部分の曲面に引掛かり易くなり、スタッド取付穴形成用突起の脱型時における引き抜き抵抗が大きくなって、スタッド取付穴形成用突起が脱型しにくくなる。
本発明は、タイヤの加硫の際においてスタッド取付穴形成用突起がトレッドから脱型しやすく、また、取付穴に取付けられたスタッドが抜けにくい取付穴を備えたタイヤ、即ち、トレッドの表面側に、脱型性能と耐スタッド抜け性能とを両立できるスタッド取付用の取付穴を備えたタイヤを提供する。 In the mounting hole disclosed in Patent Document 1, the radius of curvature of the curved surface along the central axis of the mounting hole at the boundary between the opening side and the bottom side is the central axis of the mounting hole in the inner circumferential surface of the bottom side. Because it is smaller than the radius of curvature of the curved surface along the surface, during demolding, the stud attachment hole forming protrusion can be easily caught on the curved surface of the boundary with a small radius of curvature, and the stud attachment hole forming protrusion is removed The pullout resistance at the time of molding becomes large, and the projection for forming a stud mounting hole becomes difficult to be demolded.
The present invention is a tire provided with mounting holes in which projections for forming stud mounting holes are easily released from the tread during vulcanization of the tire, and the studs mounted in the mounting holes do not easily come out, ie, the surface side of the tread Further, the present invention provides a tire provided with a mounting hole for stud attachment which can achieve both of the demolding performance and the anti-stud performance.

本発明に係るタイヤは、スタッドが取付けられる取付穴をトレッドの表面側に備えたタイヤであって、取付穴は、取付穴の中心軸に沿った方向の一方側に設けられてトレッド表面に開口する開口側部と、取付穴の中心軸に沿った方向の他方側に設けられた底側部と、取付穴の中心軸に沿った方向における開口側部の底側部側端と底側部の開口側部側端との間の領域である境界領域部とを備え、境界領域部の内周面における取付穴の中心軸に沿った面が、開口側部の底側部側端より底側部に向けて徐々に拡径するとともに取付穴の中心軸に近づく方向に突出するように湾曲する曲面により形成され、底側部の内周面における取付穴の中心軸に沿った面が、取付穴の中心軸から離れる方向に突出するように湾曲する曲面により形成され、境界領域部の内周面における取付穴の中心軸に沿った曲面の曲率半径が、底側部の内周面における取付穴の中心軸に沿った方向での最大径の位置と底側部の開口側部側端の位置との間の曲面である開口側曲面の曲率半径よりも大きい構成としたので、脱型時において、スタッド取付穴形成用突起が境界領域部の内周面における取付穴の中心軸に沿った曲率半径の大きい曲面に引掛かり難くなるため、スタッド取付穴形成用突起の引き抜き抵抗を小さくできて、スタッド取付穴形成用突起が脱型しやすくなって、トレッドにクラックが発生することを抑えることができる一方で、底側部の内周面における取付穴の中心軸に沿った曲率半径の小さい曲面により、当該取付穴に取付けられたスタッドのフランジ部を拘束する拘束力が大きくなるため、スタッダブルタイヤの使用時においてはスタッドが取付穴から抜け難くなる。即ち、脱型性能と耐スタッド抜け性能とを両立できる取付穴を備えたタイヤを提供できる。
また、底側部の内周面の最大径の位置が、境界領域部と前記底側部との境界位置と取付穴の穴底面との間の中間位置よりも穴底面に近い位置に形成されたので、境界位置と最大径の位置とを繋ぐ取付穴の中心軸に沿った曲面の曲率半径を、穴底面と最大径の位置とを繋ぐ取付穴の中心軸に沿った曲面の曲率半径よりも大きくできるようになるため、境界位置と最大径の位置とを繋ぐ取付穴の中心軸に沿った曲率半径の大きい曲面からのスタッド取付穴形成用突起の引き抜き抵抗を小さくできて、スタッド取付穴形成用突起が脱型しやすくなって、トレッドにクラックが発生することを抑えることができる一方で、曲率半径の小さい曲面により、当該取付穴に取付けられたスタッドのフランジ部を拘束する拘束力が大きくなるため、スタッダブルタイヤの使用時においてはスタッドが取付穴から抜け難くなる。即ち、脱型性能と耐スタッド抜け性能とを両立できる取付穴を備えたタイヤを提供できる。
また、開口側曲面の曲率半径が、底側部の内周面における取付穴の中心軸に沿った方向での最大径の位置と取付穴の穴底面との間の曲面である穴底側曲面の曲率半径よりも大きい構成としたので、曲率半径の大きい開口側曲面からのスタッド取付穴形成用突起の引き抜き抵抗を小さくできて、スタッド取付穴形成用突起が脱型しやすくなって、トレッドにクラックが発生することを抑えることができる一方で、曲率半径の穴底側曲面により、当該取付穴に取付けられたスタッドのフランジ部を拘束する拘束力が大きくなるため、スタッダブルタイヤの使用時においてはスタッドが取付穴から抜け難くなる。
なお、上記発明の概要は、本発明の必要な特徴の全てを列挙したものではなく、特徴群を構成する個々の構成もまた発明となり得る。 The tire according to the present invention is a tire provided with mounting holes to which studs are attached on the surface side of the tread, and the mounting holes are provided on one side in the direction along the central axis of the mounting holes and open on the tread surface. Bottom side end and bottom side of the opening side in the direction along the central axis of the mounting hole, and the bottom side provided on the other side in the direction along the central axis of the mounting hole and a boundary area portion is a region between the open side end of the surface along the central axis of the mounting hole in the inner peripheral surface of the boundary region portion, the bottom side end of the open side It is formed by a curved surface that gradually expands toward the bottom side and curves to project in a direction approaching the central axis of the mounting hole, and the surface along the central axis of the mounting hole in the inner circumferential surface of the bottom side is , Formed by a curved surface that curves to project away from the central axis of the mounting hole, and the boundary area Open side inner radius of curvature along the central axis of the mounting holes in the circumferential surface, the maximum diameter position and the bottom side of a direction along the central axis of the mounting hole in the inner peripheral surface of the bottom side of Since the configuration is larger than the curvature radius of the opening-side curved surface that is the curved surface between the position of the side end, the projection for forming the stud mounting hole is the central axis of the mounting hole on the inner circumferential surface of the boundary region It is difficult to pull on a curved surface with a large radius of curvature along the surface, so the pull-out resistance of the stud attachment hole forming projection can be reduced, and the stud attachment hole forming projection can be easily removed and cracks occur in the tread. While the curved surface with a small radius of curvature along the central axis of the mounting hole in the inner peripheral surface of the bottom side increases the restraining force for restraining the flange portion of the stud mounted in the mounting hole. Because, Stud is easily released from the mounting hole in use of Burutaiya. That is, it is possible to provide a tire provided with a mounting hole capable of achieving both the demolding performance and the anti-stud performance.
In addition, the position of the largest diameter of the inner peripheral surface of the bottom side is formed closer to the bottom of the hole than the middle position between the boundary position between the boundary area and the bottom side and the bottom of the mounting hole. Therefore, the radius of curvature of the curved surface along the central axis of the mounting hole connecting the boundary position and the position of the largest diameter is from the radius of curvature of the curved surface along the central axis of the mounting hole connecting the bottom of the hole and the position of the largest diameter The stud attachment hole can be made smaller by pulling out the protrusion for forming the stud attachment hole from the curved surface with a large radius of curvature along the central axis of the attachment hole that connects the boundary position and the position of the largest diameter. While forming projections can be easily removed from the mold, it is possible to suppress the occurrence of cracks in the tread, while the curved surface having a small radius of curvature has a constraining force that restrains the flange portion of the stud attached to the mounting hole. Studdab to grow Stud is easily released from the mounting hole in use of the tire. That is, it is possible to provide a tire provided with a mounting hole capable of achieving both the demolding performance and the anti-stud performance.
In addition, a hole bottom curved surface which is a curved surface between the position of the largest diameter in the direction along the central axis of the mounting hole in the inner peripheral surface of the bottom side and the bottom surface of the mounting hole. Since the construction is larger than the radius of curvature of the surface, the pullout resistance of the projection for forming the stud mounting hole from the curved surface on the opening side with a large radius of curvature can be reduced, and the projection for forming the stud mounting hole is easily released. While it is possible to suppress the occurrence of cracks, the curved surface on the bottom of the hole's radius of curvature increases the restraining force for restraining the flange portion of the stud attached to the mounting hole, so when using the studded tire Makes it difficult for the stud to come out of the mounting hole.
The above summary of the invention does not enumerate all the necessary features of the present invention, and individual configurations constituting a feature group can also be the invention.

(ａ）は取付穴の平面図、（ｂ）は取付穴の縦断面図。(a) is a top view of a mounting hole, (b) is a longitudinal cross-sectional view of a mounting hole. (ａ）はスタッドの平面図、（ｂ）はスタッドの正面図。(a) is a top view of a stud, (b) is a front view of a stud. スタッダブルタイヤを示す断面図。Sectional drawing which shows a studdable tire. スタッドの取付方法を示す図。The figure which shows the attachment method of a stud. 実験結果を示す図表。Chart showing experimental results. 実験結果を示す図表。Chart showing experimental results. 実験結果を示す図表。Chart showing experimental results. タイヤ金型を脱型する際の状況を示す説明図。Explanatory drawing which shows the condition at the time of demolding of a tire mold.

以下、実施形態を通じて本発明を詳説するが、以下の実施形態は特許請求の範囲に係る発明を限定するものではなく、また実施形態の中で説明される特徴の組み合わせの全てが発明の解決手段に必須であるとは限らない。 Hereinafter, the present invention will be described in detail through the embodiments, but the following embodiments do not limit the invention according to the claims, and all the combinations of the features described in the embodiments are means for solving the invention. Not necessarily essential to

図１乃至図４を参照し、スタッダブルタイヤ（スパイクタイヤと呼ばれる場合もある）１０の構成を説明する。
図３に示すように、スタッダブルタイヤ１０は、トレッド１４の表面１４ａ側にスタッド２（スパイクピンと呼ばれる場合もある）を取り付けるための取付穴３が形成されたタイヤ１と、タイヤ１の取付穴３内に嵌め込まれて取付けられたスタッド２とを備えた構成である。 The configuration of a studdable tire (sometimes called a spike tire) 10 will be described with reference to FIGS. 1 to 4.
As shown in FIG. 3, the studdable tire 10 has a tire 1 in which a mounting hole 3 for mounting a stud 2 (sometimes called a spike pin) is formed on the surface 14 a side of the tread 14, and a mounting hole of the tire 1 And 3, a stud 2 fitted in and mounted within 3.

図３に示すように、タイヤ１は、ビード部１１、ビードコア１１Ｃ、カーカス層１２、ベルト層１３ａ，１３ｂ、トレッド１４、サイドトレッド１５、取付穴３を備える。 As shown in FIG. 3, the tire 1 includes a bead portion 11, a bead core 11 C, a carcass layer 12, belt layers 13 a and 13 b, a tread 14, a side tread 15, and a mounting hole 3.

カーカス層１２は、ビード部１１に配置された１対のビードコア１１Ｃにトロイド状をなして跨るように設けられた、当該タイヤ１の骨格を成す部材で、このカーカス層１２のクラウン部のタイヤ径方向外側に内側のベルト層１３ａ及び外側のベルト層１３ｂが配置されている。当該ベルト層１３ａ，１３ｂは、それぞれ、スチールコードもしくは有機繊維を撚ったコードを、タイヤの赤道方向に対して例えば２０°〜７０°の角度で交錯するように配置したもので、タイヤ径方向内側に配置されるベルト層１３ａのコードの延長方向とタイヤ径方向外側に配置されるベルト層１３ｂのコードの延長方向とは互いに交錯している。 The carcass layer 12 is a member forming a skeleton of the tire 1 and provided so as to straddle a pair of bead cores 11C disposed in the bead portion 11, and the tire diameter of the crown portion of the carcass layer 12 The inner belt layer 13a and the outer belt layer 13b are disposed outward in the direction. The belt layers 13a and 13b are arranged such that steel cords or cords obtained by twisting organic fibers are crossed at an angle of, for example, 20 ° to 70 ° with respect to the equator direction of the tire. The extension direction of the cords of the belt layer 13a disposed inside and the extension direction of the cords of the belt layer 13b disposed outside the tire radial direction cross each other.

トレッド１４はベルト層１３ａ，１３ｂのタイヤ径方向外側に配置されたゴム部材（トレッドゴム）である。トレッド１４の表面１４ａには、タイヤ周方向及びタイヤ巾方向に沿って傾斜し延長するように設けられた傾斜ラグ主溝１６が形成されており、これらの傾斜ラグ主溝１６により複数の陸部（ブロック）１７Ａ，１７Ｂ，１８が区画される。陸部１７Ａはタイヤセンター部に位置する中央陸部で、陸部１７Ｂは上記中央陸部１７Ａのタイヤ幅方向の両外側に位置する外側陸部、陸部１８は上記外側陸部１７Ｂのタイヤ幅方向の両外側に位置するショルダー側陸部である。
各陸部１７Ａ，１７Ｂ，１８の表面には、複数のサイプ１９が形成されている。
サイドトレッド１５は上記トレッド１４の端部からタイヤのサイド部に延長して上記カーカス層１２を覆うゴム部材である。
トレッド１４と外側のベルト層１３ｂとの間には、スタッド２下（タイヤ径方向内側）のゴムのへたりにより、スタッド２が陥没して外側のベルト層１３ｂに突き刺さるのを防止するためのベルト保護層１３ｃが設けられる。ベルト保護層１３ｃは、有機繊維等から成るコードを備えた構成である。
取付穴３は、例えば上記ショルダー側陸部１８と上記外側陸部１７Ｂとに設けられる。 The tread 14 is a rubber member (tread rubber) disposed on the outer side in the tire radial direction of the belt layers 13a and 13b. Inclined lug main grooves 16 are provided on the surface 14 a of the tread 14 so as to be inclined and extend along the tire circumferential direction and the tire width direction, and a plurality of land portions are formed by these inclined lug main grooves 16. (Block) 17A, 17B, 18 are divided. Land portion 17A is a central land portion located at the tire center portion, land portion 17B is an outer land portion located on both sides in the tire width direction of central land portion 17A, and land portion 18 is a tire width of outer land portion 17B. It is a shoulder side land part located on the both sides of the direction.
A plurality of sipes 19 are formed on the surface of each land portion 17A, 17B, 18.
The side tread 15 is a rubber member that extends from the end portion of the tread 14 to the side portion of the tire and covers the carcass layer 12.
A belt for preventing the stud 2 from being depressed and sticking to the outer belt layer 13b due to rubber sag under the stud 2 (inward in the tire radial direction) between the tread 14 and the outer belt layer 13b. A protective layer 13c is provided. The belt protective layer 13c is configured to have a cord made of an organic fiber or the like.
The mounting hole 3 is provided, for example, in the shoulder land portion 18 and the outer land portion 17B.

図２に示すように、スタッド２は、ボディ部２１と、ボディ部２１の中心軸に沿った方向の一端に設けられたピン部２２と、ボディ部２１の中心軸に沿った方向の他端に設けられたフランジ部２３とを備えて構成された、ボディ部２１の中心軸に沿った方向に長い円柱状部材である。
スタッド２は、ボディ部２１の中心軸とピン部２２の中心軸とフランジ部２３の中心軸とが、連続する一直線により形成され、当該連続する一直線がスタッド２の中心軸２Ｃ（以下、単に「中心軸２Ｃ」という）を形成する。 As shown in FIG. 2, the stud 2 has a body portion 21, a pin portion 22 provided at one end in a direction along the central axis of the body portion 21, and the other end in a direction along the central axis of the body portion 21. And a flange portion 23 provided on the upper surface of the body portion 21. The cylindrical portion is elongated in the direction along the central axis of the body portion 21.
In the stud 2, the central axis of the body portion 21, the central axis of the pin portion 22 and the central axis of the flange portion 23 are formed by a continuous straight line, and the continuous straight line is a central axis 2C of the stud 2 (hereinafter simply referred to as “ Form a central axis 2C.

ボディ部２１は、中心軸２Ｃに沿った方向の一端側に位置されるアッパー部２１Ａと、中心軸２Ｃに沿った方向の他端側に位置されるローアー部２１Ｂと、アッパー部２１Ａとローアー部２１Ｂとを繋ぐミドル部２１Ｃと、を備える。
アッパー部２１Ａは、中心軸２Ｃと直交する断面形状が中心軸２Ｃに沿った全長に亘って等しい円柱体に形成される。
ローアー部２１Ｂは、中心軸２Ｃと直交する断面形状が中心軸２Ｃに沿った全長に亘って等しい円柱体に形成される。
アッパー部２１Ａの断面径とローアー部２１Ｂの断面径との関係は、アッパー部２１Ａの断面径＞ローアー部２１Ｂの断面径である。
ミドル部２１Ｃは、中心軸２Ｃと直交する断面形状の径が、アッパー部２１Ａ側からローアー部２１Ｂ側に近づくに従って徐々に小さくなる逆円錐状柱体により形成される。
ボディ部２１の先端面２１ｔは、例えば、中心軸２Ｃと直交する平面、又は、中心軸２Ｃに沿った方向の一端に向けて突出するように湾曲する湾曲面、又は、中心軸２Ｃに沿った方向の他端に向けて窪むように湾曲する湾曲面に形成されている。 The body portion 21 includes an upper portion 21A positioned on one end side in the direction along the central axis 2C, a lower portion 21B positioned on the other end side in the direction along the central axis 2C, an upper portion 21A and a lower portion And a middle unit 21C that connects with the second unit 21B.
The upper portion 21A is formed in a cylindrical body in which the cross-sectional shape orthogonal to the central axis 2C is equal over the entire length along the central axis 2C.
The lower portion 21B is formed in a cylindrical body in which the cross-sectional shape orthogonal to the central axis 2C is equal over the entire length along the central axis 2C.
The relationship between the cross-sectional diameter of the upper portion 21A and the cross-sectional diameter of the lower portion 21B is that the cross-sectional diameter of the upper portion 21A> the cross-sectional diameter of the lower portion 21B.
The middle portion 21C is formed of an inverted conical cylindrical body in which the diameter of the cross-sectional shape orthogonal to the central axis 2C gradually decreases from the upper portion 21A side toward the lower portion 21B side.
The distal end surface 21t of the body portion 21 is, for example, a plane orthogonal to the central axis 2C, or a curved surface that curves to protrude toward one end in a direction along the central axis 2C, or It is formed in the curved surface which curves so that it may be depressed toward the other end of the direction.

ピン部２２は、中心軸２Ｃと直交する断面形状が中心軸２Ｃに沿った全長に亘って等しい円柱体に形成される。
ピン部２２の先端面２２ｔは、例えば、中心軸２Ｃと直交する平面、又は、中心軸２Ｃに沿った方向の一端に向けて突出するように湾曲する湾曲面、又は、中心軸２Ｃに沿った方向の他端に向けて窪むように湾曲する湾曲面に形成されている。 The pin portion 22 is formed in a cylindrical body whose cross-sectional shape orthogonal to the central axis 2C is equal over the entire length along the central axis 2C.
The tip end surface 22t of the pin portion 22 is, for example, a plane orthogonal to the central axis 2C, or a curved surface that curves to protrude toward one end in a direction along the central axis 2C, or along the central axis 2C It is formed in the curved surface which curves so that it may be depressed toward the other end of the direction.

フランジ部２３は、外周面２４が拡径した後に中心軸２Ｃに沿った方向の一端側から他端側に向けて縮径して他端面２５に繋がるように形成され、フランジ部２３の外周面２４の最大外周径位置２４Ｍが中心軸２Ｃに沿った方向であるフランジ部厚さ方向の厚さ寸法Ｔの１／２の位置よりもピン部２２側に位置するように構成されている。 The flange portion 23 is formed such that the diameter of the outer peripheral surface 24 is expanded and the diameter is reduced from one end side to the other end side in the direction along the central axis 2C to be connected to the other end surface 25. A position 24M of the largest outer diameter 24 is positioned closer to the pin portion 22 than a half of the thickness dimension T in the flange thickness direction, which is a direction along the central axis 2C.

図外の打込みマシンにより、図４に示すように、スタッド２がタイヤ１のトレッド１４の表面１４ａ側に形成された取付穴３にスタッド２の他端側であるフランジ部２３側から嵌め込まれる。
スタッド２の高さ寸法は取付穴３の深さ寸法よりも長く形成され、スタッド２の一端側であるピン部２２がトレッド１４の表面１４ａより突出するようにスタッド２がトレッド１４の表面１４ａ側に埋込まれてスタッダブルタイヤ１０が構成される。 The stud 2 is inserted into the mounting hole 3 formed on the surface 14 a side of the tread 14 of the tire 1 from the flange portion 23 side, which is the other end side of the stud 2, as shown in FIG.
The height dimension of the stud 2 is formed longer than the depth dimension of the mounting hole 3, and the stud 2 is on the surface 14 a side of the tread 14 so that the pin portion 22 which is one end side of the stud 2 protrudes from the surface 14 a of the tread 14 Embedded in the tire to form a studdable tire 10.

図１（ｂ）に示すように、取付穴３は、タイヤ１のトレッド１４の表面１４ａからタイヤ１の円の中心（タイヤ１の回転中心軸）に向けて延長する穴により形成される。
取付穴３の中心軸３Ｃと直交する平面と交わる取付穴３の内周面３６の断面形状は円形である（図１（ａ）参照）。 As shown in FIG. 1 (b), the mounting hole 3 is formed by a hole extending from the surface 14 a of the tread 14 of the tire 1 toward the center of the circle of the tire 1 (rotational center axis of the tire 1).
The cross-sectional shape of the inner peripheral surface 36 of the mounting hole 3 intersecting with the plane orthogonal to the central axis 3C of the mounting hole 3 is circular (see FIG. 1A).

取付穴３は、取付穴の中心軸に沿った方向の一方側に設けられてトレッド１４の表面１４ａに開口する開口側部３１と、取付穴の中心軸に沿った方向の他方側に設けられた底側部３２と、取付穴３の中心軸３Ｃに沿った方向における開口側部３１の底側部側端（境界位置３８）と底側部３２の開口側部側端（境界位置３７）との間の領域である境界領域部３３とを備える。
尚、取付穴３の中心軸３Ｃとは、スタッド２が取り付けられる穴のタイヤ半径方向又はタイヤ半径方向に傾斜して穴が延在する方向の穴の中心軸、つまり、タイヤ径方向に直交する穴の断面の形状における重心（実際には穴内は空間であるので断面形状における仮想の重心）を通る中心軸をいう。 The mounting hole 3 is provided on one side in the direction along the central axis of the mounting hole and is provided on the other side in the direction along the central axis of the mounting hole and an open side 31 opened in the surface 14 a of the tread 14 Bottom side 32 and the bottom side end (boundary position 38) of the open side 31 in the direction along the central axis 3C of the mounting hole 3 and the open side end (boundary position 37) of the bottom side 32 And a boundary region portion 33 which is a region between
The central axis 3C of the mounting hole 3 is the central axis of the hole in the direction in which the hole extends in the tire radial direction or the tire radial direction of the hole to which the stud 2 is attached, that is, orthogonal to the tire radial direction The central axis passing through the center of gravity in the shape of the cross section of the hole (the virtual center of gravity in the cross sectional shape because the inside of the hole is actually a space).

開口側部３１は、漏斗形状の穴により形成される。即ち、開口側部３１は、取付穴３の中心軸３Ｃ周りの内周面（内壁面）３６が、トレッド１４の表面１４ａから穴底面３５に向けて径寸法が徐々に小さくなるとともに取付穴３の中心軸１３に近づく方向に突出するように湾曲する逆円錐形状の曲面により形成された穴入口側部３１Ａと、穴入口側部３１Ａと境界領域部３３とを繋ぐ取付穴３の中心軸３Ｃ周りの円筒状の内周面３６により形成された穴中間側部３１Ｂとを備える。
底側部３２は、穴底側における取付穴３の中心軸３Ｃ周りの内周面３６と穴底面３５とで形成される。
境界領域部３３は、開口側部３１との境界位置３８となる開口側部３１の底側部側端と、底側部３２との境界位置３７となる底側部３２の開口側部側端と、の間に位置する取付穴３の中心軸３Ｃ周りの内周面３６により形成される。
取付穴３の穴底面３５は、取付穴３の底部の平面を形成する面であり、取付穴３の深さ方向の最深位置において中心軸３Ｃと直交する平面に形成されている。
また、内周面３６と穴底面３５との境界が曲面（穴底側曲面４１Ｂ）により形成されている。 The open side 31 is formed by a funnel-shaped hole. That is, in the opening side portion 31, the diameter of the inner circumferential surface (inner wall surface) 36 around the center axis 3 C of the mounting hole 3 gradually decreases from the surface 14 a of the tread 14 toward the hole bottom 35. Hole entrance side 31A formed by a curved surface of an inverted conical shape that is curved so as to project in the direction approaching the center axis 13 of the center axis of the mounting hole 3 connecting the hole entrance side 31A and the boundary region 33 And a hole middle side 31B formed by the surrounding cylindrical inner circumferential surface 36.
The bottom side portion 32 is formed by an inner circumferential surface 36 around the central axis 3C of the mounting hole 3 and a hole bottom surface 35 at the hole bottom side.
Boundary area portion 33 has a bottom side end of the open side 31 at the boundary position 38 between the open side 31, open side end of the bottom portion 32 at the boundary position 37 between the bottom side 32 And the inner circumferential surface 36 around the central axis 3C of the mounting hole 3 located between the two.
The bottom surface 35 of the mounting hole 3 is a surface forming a flat surface of the bottom of the mounting hole 3 and is formed in a plane perpendicular to the central axis 3C at the deepest position in the depth direction of the mounting hole 3.
Further, the boundary between the inner circumferential surface 36 and the hole bottom 35 is formed by a curved surface (hole bottom curved surface 41B).

穴入口側部３１Ａの開口３ｔの開口径、穴中間側部３１Ｂの断面径、境界領域部３３の断面径、底側部３２の断面径の大小関係は、穴入口側部３１Ａの開口３ｔの開口径＞底側部３２の断面径＞境界領域部３３の断面径＞穴中間側部３１Ｂの断面径である。 The relationship between the opening diameter of the opening 3t of the hole inlet side 31A, the cross-sectional diameter of the hole middle side 31B, the cross-sectional diameter of the boundary region 33, and the cross-sectional diameter of the bottom side 32 is the same as that of the opening 3t of the hole inlet side 31A. Opening diameter> section diameter of bottom side portion 32> section diameter of boundary region portion 33> section diameter of hole intermediate side portion 31B.

取付穴３は、取付穴３の形状に対応した図外のスタッド取付穴形成用突起を加硫前のタイヤにおけるトレッドの表面側からトレッドの内側に挿入した状態でタイヤを加硫し、タイヤを加硫した後に当該スタッド取付穴形成用突起をトレッドから脱型することにより形成される。 The mounting hole 3 vulcanizes the tire in a state in which projections for forming stud mounting holes, which are not shown, corresponding to the shape of the mounting holes 3 are inserted from the surface side of the tread to the inside of the tread before vulcanization. It is formed by removing the stud attachment hole forming projections from the tread after vulcanization.

境界領域部３３の内周面３６における取付穴３の中心軸３Ｃに沿った面は、開口側部３１の底側部側端（境界位置３８）より底側部３２に向けて徐々に拡径するとともに取付穴３の中心軸３Ｃに近づく方向に突出するように湾曲する曲面４０により形成される。
底側部３２の内周面３６における取付穴３の中心軸３Ｃに沿った面は、一端が境界領域部３３との境界位置３７となる底側部３２の開口側部側端と繋がり、他端が穴底面３５と繋がる曲面であって、中心軸３Ｃから離れる方向に突出するように湾曲する曲面４１により形成される。
即ち、境界領域部３３と底側部３２との境界位置３７は、境界領域部３３の内周面３６を形成する曲面４０と底側部３２の内周面３６を形成する曲面４１との境界により形成される。言い換えれば、境界位置３７は、境界領域部３３の曲面４０を形成する曲線と底側部３２の曲面４１を形成する曲線との変曲点の集合である取付穴３の中心軸３Ｃを中心とする円線により形成される。 The surface along the central axis 3C of the mounting hole 3 in the inner circumferential surface 36 of the boundary region portion 33 gradually increases in diameter toward the bottom side 32 from the bottom side end (boundary position 38) of the opening side 31 At the same time, it is formed by a curved surface 40 which is curved so as to protrude in a direction approaching the central axis 3C of the mounting hole 3.
The surface along the central axis 3C of the mounting hole 3 in the inner circumferential surface 36 of the bottom side 32 is connected to the open side end of the bottom side 32 whose one end is the boundary position 37 with the boundary region 33; The end is a curved surface connected to the hole bottom surface 35, and is formed by a curved surface 41 that curves so as to protrude in a direction away from the central axis 3C.
That is, the boundary position 37 between the boundary region 33 and the bottom side 32 is the boundary between the curved surface 40 forming the inner circumferential surface 36 of the boundary region 33 and the curved surface 41 forming the inner circumferential surface 36 of the bottom side 32. It is formed by In other words, boundary position 37 is centered on central axis 3C of mounting hole 3 which is a set of inflection points of a curve forming curved surface 40 of boundary region portion 33 and a curve forming curved surface 41 of bottom side portion 32. Formed by circular lines.

そして、取付穴３の中心軸３Ｃと直交する平面と交わる底側部３２の内周面３６における最大径Ｃの位置３６Ｍが、上述した境界位置３７と穴底面３５との間の中間位置３９よりも穴底面３５に近い位置に形成されている。
即ち、底側部３２の内周面３６を形成する曲面４１は、前記境界位置３７と前記最大径Ｃの位置３６Ｍとを繋ぐ開口側曲面４１Ａと、前記最大径Ｃの位置３６Ｍと底側部３２の穴底面３５とを繋ぐ穴底側曲面４１Ｂとで形成される。
つまり、最大径Ｃの位置３６Ｍは、開口側曲面４１Ａを形成する曲線と穴底側曲面４１Ｂを形成する曲線との変曲点の集合である取付穴３の中心軸３Ｃを中心とする円線により形成される。 The position 36M of the maximum diameter C in the inner peripheral surface 36 of the bottom side 32 intersecting the plane orthogonal to the central axis 3C of the mounting hole 3 is from the intermediate position 39 between the boundary position 37 and the hole bottom 35 described above. Is also formed at a position close to the bottom surface 35 of the hole.
That is, the curved surface 41 forming the inner circumferential surface 36 of the bottom side portion 32 has an opening-side curved surface 41A connecting the boundary position 37 and the position 36M of the maximum diameter C, the position 36M of the maximum diameter C and the bottom side It is formed by the hole bottom side curved surface 41B which connects the 32 hole bottoms 35.
That is, the position 36M of the maximum diameter C is a circle centered on the central axis 3C of the mounting hole 3 which is a set of inflection points of the curve forming the opening side curved surface 41A and the curve forming the hole bottom side curved surface 41B. It is formed by

さらに、境界領域部３３の内周面３６における取付穴３の中心軸３Ｃに沿った曲面４０の曲率半径Ｒ３は、底側部３２の内周面３６における取付穴３の中心軸３Ｃに沿った曲面４１の曲率半径Ｒ１；Ｒ２よりも大きくなるように形成されている。
尚、内周面や曲面の曲率半径とは、取付穴３の中心軸３Ｃに沿った方向の中心軸３Ｃを含む取付穴３の断面を、取付穴３の深さ方向に側面視した場合の側方側の面を形成する線分の曲率半径をいう。 Furthermore, the radius of curvature R3 of the curved surface 40 along the central axis 3C of the mounting hole 3 in the inner peripheral surface 36 of the boundary region 33 is along the central axis 3C of the mounting hole 3 in the inner peripheral surface 36 of the bottom side 32. The curvature radius R1 of the curved surface 41 is larger than R2.
The radius of curvature of the inner peripheral surface or the curved surface means that the cross section of the mounting hole 3 including the central axis 3C in the direction along the central axis 3C of the mounting hole 3 is viewed from the side in the depth direction of the mounting hole 3 The radius of curvature of the line segment that forms the side surface.

即ち、境界領域部３３の曲面４０の曲率半径Ｒ３と底側部３２の開口側曲面４１Ａの曲率半径Ｒ１との関係は、曲率半径Ｒ３＞曲率半径Ｒ１である。
言い換えれば、底側部３２の開口側曲面４１Ａの曲率が境界領域部３３の曲面４０の曲率よりも大きい（開口側曲面４１Ａの曲がり具合が曲面４０の曲がり具合よりもきつい）構成となっている。
また、底側部３２の開口側曲面４１Ａの曲率半径Ｒ１と底側部３２の穴底側曲面４１Ｂの曲率半径Ｒ２との関係は、曲率半径Ｒ１＞曲率半径Ｒ２である。
言い換えれば、穴底側曲面４１Ｂの曲率が開口側曲面４１Ａの曲率よりも大きい（穴底側曲面４１Ｂの曲がり具合が開口側曲面４１Ａの曲がり具合よりもきつい）構成となっている。 That is, the relationship between the curvature radius R3 of the curved surface 40 of the boundary region portion 33 and the curvature radius R1 of the opening-side curved surface 41A of the bottom side portion 32 is curvature radius R3> curvature radius R1.
In other words, the curvature of the opening-side curved surface 41A of the bottom side portion 32 is larger than the curvature of the curved surface 40 of the boundary region 33 (the curvature of the opening-side curved surface 41A is tighter than the curvature of the curved surface 40). .
Further, the relationship between the curvature radius R1 of the opening-side curved surface 41A of the bottom side portion 32 and the curvature radius R2 of the bottom surface 32B of the bottom side portion 32 is curvature radius R1> curvature radius R2.
In other words, the curvature of the hole bottom curved surface 41B is larger than the curvature of the opening curved surface 41A (the curvature of the hole bottom curved surface 41B is tighter than the curvature of the opening curved surface 41A).

即ち、取付穴３の内周面３６において、境界領域部３３の曲面４０の曲率半径Ｒ３と、底側部３２の開口側曲面４１Ａの曲率半径Ｒ１と、底側部３２の穴底側曲面４１Ｂの曲率半径Ｒ２との関係は、曲率半径Ｒ３＞曲率半径Ｒ１＞曲率半径Ｒ２である。
言い換えれば、穴底側曲面４１Ｂの曲率＞開口側曲面４１Ａの曲率＞境界領域部３３の曲面４０の曲率である。 That is, the curvature radius R3 of the curved surface 40 of the boundary region 33, the curvature radius R1 of the opening side curved surface 41A of the bottom side portion 32, and the hole bottom side curved surface 41B of the bottom side portion 32 on the inner peripheral surface 36 of the mounting hole 3 The relationship between the radius of curvature R2 and the radius of curvature R2 is: radius of curvature R3> radius of curvature R1> radius of curvature R2.
In other words, the curvature of the hole bottom curved surface 41B> the curvature of the opening curved surface 41A> the curvature of the curved surface 40 of the boundary region portion 33.

このように、境界領域部３３の曲面４０の曲率半径Ｒ３と底側部３２の開口側曲面４１Ａの曲率半径Ｒ１との関係を、曲率半径Ｒ３＞曲率半径Ｒ１に設定したことにより、脱型時において、スタッド取付穴形成用突起５１が境界領域部３３の曲率半径の大きい曲面４０に引掛かり難くなるため、スタッド取付穴形成用突起５１を開口側曲面４１Ａ及び曲面４０から引き抜く際の引き抜き抵抗を小さくできて、スタッド取付穴形成用突起５１が脱型しやすくなって、トレッド１４にクラックが発生することを抑えることができる。一方で、底側部３２の曲面４１が取付穴３の中心軸３Ｃに沿って中心軸３Ｃから離れる方向に突出するよう湾曲する曲面により形成されていることから、当該取付穴３に取付けられたスタッド２のフランジ部２３を底側部３２によって拘束する拘束力が大きくなるため、スタッダブルタイヤ１０の使用時においてはスタッド２が取付穴３から抜け難くなる。即ち、脱型性能と耐スタッド抜け性能とを両立できる取付穴３を備えたタイヤ１を提供できる。言い換えれば、脱型性能に優れたスタッド取付穴形成用突起を用いて形成された耐スタッド抜け性能に優れた取付穴３を備えたタイヤ１を得ることができる。 As described above, when the relationship between the radius of curvature R3 of the curved surface 40 of the boundary region portion 33 and the radius of curvature R1 of the opening-side curved surface 41A of the bottom side portion 32 is set as the radius of curvature R3> the radius of curvature R1, In this case, the projection 51 for forming the stud attachment hole is difficult to catch on the curved surface 40 having a large radius of curvature of the boundary area 33, and therefore the pullout resistance when the projection 51 for forming the stud attachment hole is drawn from the opening side curved surface 41A and the curved surface 40 This can be made smaller, and the stud attachment hole forming projections 51 can be easily removed, and the occurrence of cracks in the tread 14 can be suppressed. On the other hand, since the curved surface 41 of the bottom side portion 32 is formed by a curved surface that curves in a direction away from the central axis 3C along the central axis 3C of the mounting hole 3, it is attached to the mounting hole 3 Since the restraining force for restraining the flange portion 23 of the stud 2 by the bottom side portion 32 is increased, the stud 2 becomes difficult to come out of the mounting hole 3 when the studdable tire 10 is used. That is, it is possible to provide the tire 1 provided with the mounting hole 3 capable of achieving both the demolding performance and the anti-stud performance. In other words, it is possible to obtain the tire 1 provided with the mounting hole 3 excellent in the stud removal performance formed using the stud mounting hole forming protrusion excellent in the mold release performance.

境界領域部３３の曲面４０の曲率半径Ｒ３と開口側曲面４１Ａの曲率半径Ｒ１との比＝Ｒ３／Ｒ１の数値の範囲は、１．２≦Ｒ３／Ｒ１≦５、好ましくは、１．７≦Ｒ３／Ｒ１≦３とした。
境界領域部３３の曲面４０の曲率半径Ｒ３を小さくし過ぎて、Ｒ３／Ｒ１を１．２よりも小さくしてしまうと、スタッド取付穴形成用突起５１が境界領域部３３の曲面４０に引掛かり易くなって抜け難くなり、脱型性能が向上しない可能性があり、逆に、Ｒ３を大きくし過ぎて、Ｒ３／Ｒ１を５よりも大きくしてしまうと、スタッド２のフランジ部２３の外周面２４が境界領域部３３の曲面４０に引掛かり難くなって、耐スタッド抜け性能が向上しない可能性があるからである。
そこで、脱型性能が向上するように境界領域部３３の曲面４０の曲率半径Ｒ３を設定するとともに、当該曲率半径Ｒ３との関係において、Ｒ３／Ｒ１の数値の範囲を、１．２≦Ｒ３／Ｒ１≦５、好ましくは、１．７≦Ｒ３／Ｒ１≦３としたことで、脱型性能と耐スタッド抜け性能とを両立できる取付穴３を形成した。
即ち、Ｒ３／Ｒ１を１．２よりも小さくした場合、スタッド取付穴形成用突起５１の脱型性能が低下し、Ｒ３／Ｒ１を５よりも大きくした場合、耐スタッド抜け性能が低下する可能性があるため、Ｒ３／Ｒ１の数値の範囲を、１．２≦Ｒ３／Ｒ１≦５とした。そして、耐スタッド抜け性能とスタッド取付穴形成用突起５１の脱型性能とををより向上できる取付穴３とするため、Ｒ３／Ｒ１の数値の範囲を、１．７≦Ｒ３／Ｒ１≦３とした。 The ratio of the ratio R3 / R1 of the radius of curvature R3 of the curved surface 40 of the boundary region portion 33 to the radius of curvature R1 of the opening-side curved surface 41A is 1.2 ≦ R3 / R1 ≦ 5, preferably 1.7 ≦ It was set as R3 / R1 <= 3.
If the radius of curvature R3 of the curved surface 40 of the boundary region portion 33 is made too small and R3 / R1 is made smaller than 1.2, the projection 51 for forming a stud attachment hole is caught on the curved surface 40 of the boundary region portion 33. It becomes difficult to come off easily, and there is a possibility that the demolding performance will not improve. Conversely, if R3 / R1 is made larger than 5 by making R3 too large, the outer peripheral surface of the flange portion 23 of the stud 2 This is because there is a possibility that the anti-stud removal performance is not improved because it becomes difficult for the curved surface 24 of the boundary region portion 33 to get caught.
Therefore, the curvature radius R3 of the curved surface 40 of the boundary region 33 is set so as to improve the demolding performance, and the numerical range of R3 / R1 is 1.2 ≦ R3 / in relation to the curvature radius R3. By setting R1 ≦ 5, preferably 1.7 ≦ R3 / R1 ≦ 3, the mounting hole 3 is formed in which the mold release performance and the stud removal resistance performance can be compatible.
That is, when R3 / R1 is made smaller than 1.2, the demolding performance of the stud attachment hole forming protrusion 51 is lowered, and when R3 / R1 is made larger than 5, the possibility of lowering the anti-stud performance is lowered. Therefore, the numerical range of R3 / R1 is set to 1.2 ≦ R3 / R1 ≦ 5. And, in order to make the mounting hole 3 capable of further improving the anti-stud performance and the demolding performance of the protrusion 51 for forming a stud mounting hole, the numerical range of R3 / R1 is set to 1.7 ≦ R3 / R1 ≦ 3. did.

また、底側部３２の内周面３６の最大径Ｃの位置３６Ｍが、開口側部３１と底側部３２との境界位置３７と穴底面３５との間の中間位置３９よりも穴底面３５に近い位置に形成されているため、取付穴３の底側部３２における開口側部３１に近い側の内周面３６において前記境界位置３７と最大径Ｃの位置３６Ｍとを繋ぐように境界位置３７と最大径Ｃの位置３６Ｍとの間に位置する取付穴３の中心軸３Ｃに沿った開口側曲面４１Ａの曲率半径Ｒ１を、取付穴３の穴底面３５と最大径Ｃの位置３６Ｍとを繋ぐように穴底面３５と最大径Ｃの位置３６Ｍとの間に位置する取付穴３の中心軸３Ｃに沿った穴底側曲面４１Ｂの曲率半径Ｒ２よりも大きくできるようになる。このため、前記境界位置３７と最大径Ｃの位置３６Ｍとの間に位置する取付穴３の中心軸３Ｃに沿った曲率半径の大きい開口側曲面４１Ａからのスタッド取付穴形成用突起５１の引き抜き抵抗を小さくできて、スタッド取付穴形成用突起５１が脱型しやすくなって、トレッド１４にクラックが発生することを抑えることができる一方で、取付穴３の穴底面３５と最大径Ｃの位置３６Ｍとの間に位置する取付穴３の中心軸３Ｃに沿った曲率半径の小さい穴底側曲面４１Ｂにより、当該取付穴３に取付けられたスタッド２のフランジ部２３を拘束する拘束力が大きくなるため、スタッダブルタイヤ１０の使用時においてはスタッド２が取付穴３から抜け難くなる。即ち、脱型性能と耐スタッド抜け性能とを両立できる取付穴を備えたタイヤを提供できる。言い換えれば、脱型性能に優れたスタッド取付穴形成用突起を用いて形成された耐スタッド抜け性能に優れた取付穴３を備えたタイヤ１を得ることができる。 Further, the position 36 M of the maximum diameter C of the inner circumferential surface 36 of the bottom side 32 is lower than the hole bottom 35 than the middle position 39 between the boundary position 37 between the open side 31 and the bottom side 32 and the hole bottom 35. Of the bottom side 32 of the mounting hole 3 so as to connect the boundary position 37 and the position 36M of the largest diameter C on the inner circumferential surface 36 on the side close to the opening side 31 of the mounting hole 3 The curvature radius R1 of the opening-side curved surface 41A along the central axis 3C of the mounting hole 3 located between 37 and the position 36M of the maximum diameter C, the bottom 35 of the mounting hole 3 and the position 36M of the maximum diameter C The radius of curvature R2 of the hole bottom curved surface 41B along the central axis 3C of the mounting hole 3 located between the hole bottom surface 35 and the position 36M of the maximum diameter C can be made larger so as to connect. For this reason, the pullout resistance of the protrusion 51 for forming the stud attachment hole from the opening side curved surface 41A having a large radius of curvature along the central axis 3C of the attachment hole 3 located between the boundary position 37 and the position 36M of the maximum diameter C. Can be made smaller, and the projections 51 for forming the stud attachment holes can be easily removed, and generation of cracks in the tread 14 can be suppressed, while the bottom surface 35 of the attachment hole 3 and the position 36 M of the maximum diameter C And the bottom surface 41B having a small radius of curvature along the central axis 3C of the mounting hole 3 located between the two, and the restraining force for restraining the flange portion 23 of the stud 2 mounted in the mounting hole 3 is increased. When the studdable tire 10 is used, the stud 2 is difficult to come off the mounting hole 3. That is, it is possible to provide a tire provided with a mounting hole capable of achieving both the demolding performance and the anti-stud performance. In other words, it is possible to obtain the tire 1 provided with the mounting hole 3 excellent in the stud removal performance formed using the stud mounting hole forming protrusion excellent in the mold release performance.

尚、穴底面３５と前記境界位置３７との間の距離、即ち底側部３２の高さ寸法をｄとし、前記境界位置３７と最大径Ｃの位置３６Ｍとの間の距離をｄ１とし、穴底面３５と最大径Ｃの位置３６Ｍとの間の距離をｄ２とした場合、最大径Ｃの位置３６Ｍ＝ｄ２＝ｄ１／ｄの位置範囲を、０．５＜ｄ１／ｄ＜０．９、好ましくは、０．５＜ｄ１／ｄ＜０．７としたことで、脱型性能と耐スタッド抜け性能とを両立できる取付穴３を形成できる。 The distance between the hole bottom surface 35 and the boundary position 37, that is, the height dimension of the bottom side 32 is d, and the distance between the boundary position 37 and the position 36M of the largest diameter C is d1, and the hole is Assuming that the distance between the bottom surface 35 and the position 36M of the maximum diameter C is d2, the position range of the maximum diameter C 36M = d2 = d1 / d is preferably 0.5 <d1 / d <0.9, preferably By setting 0.5 <d1 / d <0.7, it is possible to form the mounting hole 3 that can achieve both the mold release performance and the anti-stud performance.

また、底側部３２の最大径Ｃと穴中間側部３１Ｂの径Ｂとの比＝Ｃ／Ｂの数値の範囲を、１．０≦Ｃ／Ｂ≦１．６としたので、脱型性能と耐スタッド抜け性能とを両立できる取付穴３を形成できる。Ｃ／Ｂが小さすぎると耐スタッド抜け性能が低下し、Ｃ／Ｂが大きすぎると脱型性能が低下する。Ｃ／Ｂが１．０よりも小さいと耐スタッド抜け性能が低下し、Ｃ／Ｂが１．６よりも大きいと脱型性能が低下したため、実施形態においては、Ｃ／Ｂを、１．０≦Ｃ／Ｂ≦１．６とした。 In addition, since the range of the ratio of the ratio of the maximum diameter C of the bottom side 32 to the diameter B of the hole middle side 31 B = C / B is 1.0 ≦ C / B ≦ 1.6, the mold release performance The mounting hole 3 can be formed to be compatible with the anti-stud performance. When C / B is too small, anti-stud performance decreases, and when C / B is too large, demolding performance decreases. If C / B is less than 1.0, anti-stud performance decreases, and if C / B is greater than 1.6, demolding performance decreases. Therefore, in the embodiment, C / B is 1.0, 1.0 or less. It was set as ≦ C / B ≦ 1.6.

さらに、開口側曲面４１Ａの曲率半径Ｒ１と穴底側曲面４１Ｂの曲率半径Ｒ２との比＝Ｒ１／Ｒ２の数値の範囲は、１．５≦Ｒ１／Ｒ２≦１００、好ましくは、２≦Ｒ１／Ｒ２≦１０とした。
穴底側曲面４１Ｂの曲率半径Ｒ２は、小さくても脱型性能に影響を与え難いが、曲率半径Ｒ２を小さくしすぎれば、穴底側曲面４１Ｂが鋭角な角部になってしまい、当該角部からクラックが発生しやすくなる。一方、穴底側曲面４１Ｂの曲率半径Ｒ２を大きくしすぎれば、スタッド２のフランジ部２３を拘束する拘束力が不足して耐スタッド抜け性能が低下する。
そこで、脱型性能が向上するように開口側曲面４１Ａの曲率半径Ｒ１を設定するとともに、当該曲率半径Ｒ１との関係において、Ｒ１／Ｒ２の数値の範囲を、１．５≦Ｒ１／Ｒ２≦１００、好ましくは、２≦Ｒ１／Ｒ２≦１０としたことで、脱型性能と耐スタッド抜け性能とを両立できる取付穴３を形成した。
即ち、Ｒ１／Ｒ２を１．５よりも小さくした場合、耐スタッド抜け性能が低下し、Ｒ１／Ｒ２を１００よりも大きくした場合、穴底側曲面４１Ｂが鋭角な角部になって当該角部からクラックが発生しやすくなるので、Ｒ１／Ｒ２の数値の範囲を、１．５≦Ｒ１／Ｒ２≦１００とした。そして、耐スタッド抜け性能の向上とクラックの発生をより抑制できる取付穴３とするため、Ｒ１／Ｒ２の数値の範囲を、２≦Ｒ１／Ｒ２≦１０とした。 Furthermore, the range of the numerical value of the ratio R1 / R2 of the ratio R1 / R2 of the radius of curvature R1 of the opening side curved surface 41A to the radius of curvature R2 of the hole bottom side curved surface 41B is 1.5 ≦ R1 / R2 ≦ 100, preferably 2 ≦ R1 / R2 ≦ 10.
Even if the curvature radius R2 of the hole bottom curved surface 41B is small, it is difficult to affect the demolding performance, but if the curvature radius R2 is too small, the hole bottom curved surface 41B becomes an acute corner, and the corner concerned Cracks are likely to occur from parts. On the other hand, if the radius of curvature R2 of the hole bottom curved surface 41B is too large, the restraining force for restraining the flange portion 23 of the stud 2 will be insufficient and the anti-stud performance will deteriorate.
Therefore, the curvature radius R1 of the opening-side curved surface 41A is set so as to improve the demolding performance, and the numerical range of R1 / R2 is 1.5 ≦ R1 / R2 ≦ 100 in relation to the curvature radius R1. Preferably, by setting 2 ≦ R1 / R2 ≦ 10, the mounting hole 3 in which the demolding performance and the anti-stud performance are compatible is formed.
That is, when R1 / R2 is smaller than 1.5, the anti-stud performance is lowered, and when R1 / R2 is larger than 100, the bottom surface 41B of the hole becomes a sharp corner and the corner is concerned Since cracks easily occur from this, the range of the numerical values of R1 / R2 is set to 1.5 ≦ R1 / R2 ≦ 100. And in order to set it as the attachment hole 3 which can suppress generation | occurrence | production of a crack by the improvement of a stud drop-off performance, the range of the numerical value of R1 / R2 was 2 <= R1 / R2 <= 10.

また、穴底面３５を中心軸３Ｃと直交する平面に形成したので、加硫前のトレッドに対するスタッド取付穴形成用突起の設置安定性が良くなり、取付穴３の成型精度が向上する。 Further, since the bottom surface 35 of the hole is formed in a plane orthogonal to the central axis 3C, the installation stability of the stud mounting hole forming protrusion with respect to the tread before vulcanization is improved, and the molding accuracy of the mounting hole 3 is improved.

トレッド１４は、ベルト層１３ａ，１３ｂのタイヤ径方向外側に設けられたベースゴム層１４Ｂと、当該ベースゴム層１４Ｂ上に積層されてトレッド１４の表面層を形成するトップゴム層１４Ｔとを備える。即ち、トレッド１４は、トレッド１４の表面層を形成するトップゴム層１４Ｔと、トップゴム層１４Ｔよりもタイヤ径方向内側に位置されてトップゴム層１４Ｔと隣接するベースゴム層１４Ｂとを備えた構成である。 The tread 14 includes a base rubber layer 14B provided on the tire radial direction outer side of the belt layers 13a and 13b, and a top rubber layer 14T that is laminated on the base rubber layer 14B to form a surface layer of the tread 14. That is, the tread 14 includes a top rubber layer 14T that forms the surface layer of the tread 14, and a base rubber layer 14B positioned on the inner side in the tire radial direction than the top rubber layer 14T and adjacent to the top rubber layer 14T. It is.

そして、ベースゴム層１４Ｂを形成するゴム（ベースゴム）の室温時の弾性率Ｍｎ１と加硫時の弾性率Ｍｎ２との比＝Ｍｎ２／Ｍｎ１を、トップゴム層１４Ｔを形成するゴム（トップゴム）の室温時の弾性率Ｍｎ３と加硫時の弾性率Ｍｎ４との比＝Ｍｎ４／Ｍｎ３よりも小さくした。つまり、評価値＝（Ｍｎ２／Ｍｎ１）／（Ｍｎ４／Ｍｎ３）が１よりも小さくなることで、ベースゴムの室温時の弾性率Ｍｎ１に比べてベースゴムの加硫時の弾性率Ｍｎ２が小さくなり、脱型性能が向上する。
即ち、ベースゴム層１４Ｂを形成するゴムを、トップゴム層１４Ｔを形成するゴムと比べて、室温時に硬く、加硫時に柔らかくなる特性を有したゴムにより形成した。
尚、室温時とは、１０℃〜４０℃のことをいい、ここでは２３℃である。当該温度は、氷雪路面での通常のタイヤの使用状態における温度のことであり、耐スタッド抜け性能に最も関係のある温度だからである。
また、加硫時とは、１００℃〜２００℃のことをいい、ここでは１００℃である。未加硫ゴムが加硫された直後の温度のことであり、脱型性能に最も関係のある温度だからである。 Then, the ratio of the elastic modulus Mn1 at room temperature of the rubber (base rubber) forming the base rubber layer 14B to the elastic modulus Mn2 at vulcanization = Mn2 / Mn1 and the rubber forming the top rubber layer 14T (top rubber) The ratio of the elastic modulus Mn3 at room temperature to the elastic modulus Mn4 at vulcanization was smaller than Mn4 / Mn3. That is, when the evaluation value = (Mn2 / Mn1) / (Mn4 / Mn3) becomes smaller than 1, the elastic modulus Mn2 at the time of vulcanization of the base rubber becomes smaller than the elastic modulus Mn1 at the room temperature of the base rubber. , Demolding performance is improved.
That is, the rubber forming the base rubber layer 14B is formed of a rubber which is harder at room temperature and softens at the time of vulcanization as compared with the rubber forming the top rubber layer 14T.
The room temperature means 10 ° C. to 40 ° C., which is 23 ° C. here. The said temperature is the temperature in the normal tire use condition on a snowy and snowy road surface, and is the temperature most related to the stud penetration resistance performance.
Moreover, at the time of vulcanization | cure means the thing of 100 degreeC-200 degreeC, and it is 100 degreeC here. It is the temperature immediately after the unvulcanized rubber is vulcanized and is the temperature most related to the demolding performance.

評価値＝ベースゴムの加硫時（１００℃）の弾性率／ベースゴムの室温時（２３℃）の弾性率／トップゴムの加硫時（１００℃）の弾性率／トップゴムの室温時（２３℃）の弾性率＝（Ｍｎ２／Ｍｎ１）／（Ｍｎ４／Ｍｎ３）の値が異なる複数のタイヤを作製し、これら複数のタイヤに取付穴３を形成した際の脱型（脱釜）性能、及び、これら複数のタイヤの取付穴３にスタッド２を取付けて作製した複数のスタッダブルタイヤの耐スタッド抜け性能を実験した。 Evaluation value = elastic modulus of base rubber at vulcanization (100 ° C.) / Elastic modulus of base rubber at room temperature (23 ° C.) / Elastic modulus of top rubber at vulcanization (100 ° C.) / Temper of top rubber at room temperature (100 ° C.) A plurality of tires having different values of modulus of elasticity = (Mn2 / Mn1) / (Mn4 / Mn3) at 23 ° C.), and mold release (de-hook) performance when the mounting holes 3 are formed in the plurality of tires, And, the stud removal resistance performance of a plurality of studdable tires manufactured by attaching the studs 2 to the mounting holes 3 of the plurality of tires was tested.

弾性率Ｍｎ１〜Ｍｎ４として、５０％モジュラス（Ｍ５０）を用いた場合の実験結果を図５（ａ）に示し、弾性率Ｍｎ１〜Ｍｎ４として、３００％モジュラス（Ｍ３００）を用いた場合の実験結果を図５（ｂ）に示し、弾性率Ｍｎ１〜Ｍｎ４として、タフネスＴＦを用いた場合の実験結果を図６（ａ）に示し、弾性率Ｍｎ１〜Ｍｎ４として、動的引張弾性率（ヤング率）Ｅ’を用いた場合の実験結果を図６（ｂ）に示し、弾性率Ｍｎ１〜Ｍｎ４として、破断時の引張強さＴＢを用いた場合の実験結果を図７（ａ）に示し、弾性率Ｍｎ１〜Ｍｎ４として、破断時の伸びＥＢを用いた場合の実験結果を図７（ｂ）に示す。 The experimental result in the case of using 50% modulus (M50) as elastic modulus Mn1 to Mn4 is shown in FIG. 5A, and the experimental result in the case of using 300% modulus (M300) as elastic modulus Mn1 to Mn4 is shown. The experimental results in the case of using toughness TF as elastic modulus Mn1 to Mn4 are shown in FIG. 5 (b), and dynamic tensile elastic modulus (Young's modulus) E is shown as elastic modulus Mn1 to Mn4. The experimental result in the case of using 'is shown in FIG. 6 (b), the experimental result in the case of using the tensile strength TB at break as elastic modulus Mn1 to Mn4 is shown in FIG. 7 (a). The experimental result at the time of using elongation EB at the time of fracture | rupture as -Mn4 is shown in FIG.7 (b).

尚、図５乃至図７における脱型性能及び耐スタッド抜け性能は、比較例２のタイヤの脱型性能及び耐スタッド抜け性能の評価結果を１００とした場合の相対評価となる指数を比較例１及び実施例１乃至実施例３のタイヤの各々で算出したものであり、指数が大きいほど、脱型性能、耐スタッド抜け性能が高いことを示す。 Incidentally, the demolding performance and the stud removal resistance performance in FIGS. 5 to 7 are the relative evaluation index when the evaluation result of the demolding performance and the stud removal resistance performance of the tire of Comparative Example 2 is 100, Comparative Example 1 And it calculated with each of the tire of Example 1 thru | or Example 3, and it shows that it is high in a mold release performance and stud removal resistance performance, so that an index is large.

実験結果から、評価値＝（Ｍｎ２／Ｍｎ１）／（Ｍｎ４／Ｍｎ３）が１よりも大きい比較例１のタイヤでは、脱型性能が比較例２のタイヤよりも悪化したのに対し、評価値＝（Ｍｎ２／Ｍｎ１）／（Ｍｎ４／Ｍｎ３）が１よりも小さい実施例１乃至実施例３のタイヤでは、脱型性能が比較例２のタイヤに比べて向上することが判明した。
尚、弾性率として５０％モジュラス（Ｍ５０）を用いて評価値＝（Ｍｎ２／Ｍｎ１）／（Ｍｎ４／Ｍｎ３）を評価することで、脱型性能を最も的確に制御できる。 From the experimental results, in the tire of Comparative Example 1 where the evaluation value = (Mn2 / Mn1) / (Mn4 / Mn3) is larger than 1, the demolding performance is worse than the tire of Comparative Example 2, but the evaluation value = It was found that the tires of Examples 1 to 3 in which (Mn2 / Mn1) / (Mn4 / Mn3) were smaller than 1 had improved demolding performance as compared with the tire of Comparative Example 2.
By evaluating the evaluation value = (Mn2 / Mn1) / (Mn4 / Mn3) using the 50% modulus (M50) as the elastic modulus, the demolding performance can be most accurately controlled.

また、動的引張弾性率Ｅ’は、上島製作所株式会社製スペクトロメーターを用いて、動歪１％、周波数５２Ｈｚの条件下で測定した。この動的引張弾性率Ｅ’の数値が大きい程、高弾性であることを示す。
さらに、５０％モジュラス（Ｍ５０）は、ＪＩＳＫ６２５１−２０１０に基づき、５０％の引張応力（５０％モジュラス）をＪＩＳＫ６２５０−６．１（試験室の標準温度）の２３℃で室温時の弾性率を測定し、ＪＩＳＫ６２５０−１１．２．２（その他の試験温度）から選択した１００℃で加硫時の弾性率を測定した。 The dynamic tensile modulus E ′ was measured under the condition of dynamic strain 1% and frequency 52 Hz using a spectrometer manufactured by Uejima Mfg. Co., Ltd. The larger the value of the dynamic tensile elastic modulus E ′, the higher the elasticity.
Furthermore, 50% modulus (M50) is based on JIS K6251-2010, and 50% tensile stress (50% modulus) elastic modulus at room temperature at 23 ° C. of JIS K 6250-6.1 (standard temperature of test room) The modulus of elasticity at the time of vulcanization was measured at 100 ° C. selected from JIS K 6250-11.2.2 (other test temperatures).

また、トップゴム層１４Ｔとベースゴム層１４Ｂとの境界面１４Ｘを、取付穴３の境界領域部３３と底側部３２との境界位置３７よりもトレッド１４の表面１４ａに近い位置に形成した。 The boundary surface 14X between the top rubber layer 14T and the base rubber layer 14B is formed closer to the surface 14a of the tread 14 than the boundary position 37 between the boundary region 33 of the mounting hole 3 and the bottom side portion 32.

具体的には、前記境界面１４Ｘの位置を、穴底面３５と前記境界位置３７との間の距離を距離ｄとした場合に、穴底面３５からトレッド１４の表面１４ａに向けて距離ｄだけ離れた位置Ｘ１と穴底面３５からトレッド１４の表面１４ａに向けて距離ｄの２倍だけ離れた位置Ｘ２との間に設けた。
即ち、取付穴３の中心軸３Ｃに沿った方向における前記境界面１４Ｘと前記境界位置３７との間の距離ｄ３は、取付穴３の底側部３２の中心軸３Ｃに沿った方向の高さ寸法（＝距離ｄ）よりも小さい構成とした。 Specifically, when the distance between the hole bottom surface 35 and the boundary position 37 is a distance d, the boundary surface 14X is separated from the hole bottom surface 35 by the distance d toward the surface 14 a of the tread 14 It is provided between the position X1 and a position X2 which is separated from the hole bottom 35 toward the surface 14a of the tread 14 by twice the distance d.
That is, the distance d3 between the boundary surface 14X and the boundary position 37 in the direction along the central axis 3C of the mounting hole 3 is the height along the central axis 3C of the bottom side 32 of the mounting hole 3 The configuration is smaller than the dimension (= distance d).

即ち、ベースゴム層１４Ｂを形成するゴムを、トップゴム層１４Ｔを形成するゴムと比べて、室温時に硬く、加硫時に柔らかくなる特性を有したゴムにより形成したので、室温時であるスタッダブルタイヤ１０の使用時の耐スタッド抜け性能が維持されるとともに、加硫時である脱型時の脱型性能が向上する。
また、スタッド２が取付穴３に取付けられたスタッダブルタイヤ１０の使用時において最も大きい歪がかかる部位は、取付穴３の境界領域部３３と底側部３２との境界位置３７である。実施形態においては、トップゴム層１４Ｔとベースゴム層１４Ｂとの境界面１４Ｘが、取付穴３の境界領域部３３と底側部３２との境界位置３７よりもトレッド１４の表面１４ａに近い位置に形成されている。即ち、境界面１４Ｘが、スタッダブルタイヤ１０の使用時において最も大きい歪がかかる境界位置３７に位置されず、当該境界面１４Ｘに大きな歪が発生しないようになるので、境界面１４Ｘでゴムが破壊されにくくなり、耐スタッド抜け性能が向上する。
また、脱型時において最も大きい歪がかかる部位は、取付穴３の境界領域部３３と底側部３２との境界位置３７から底側部３２の高さ寸法ｄだけ離れた位置Ｘ２よりも取付穴３の開口３ｔに近い位置であり、当該位置に、境界面１４Ｘが位置されず、脱型時に当該境界面１４Ｘに大きな歪が発生しないようになるので、境界面１４Ｘでゴムが破壊されにくくなり、脱型性能が向上する。 That is, since the rubber forming the base rubber layer 14B is formed of a rubber having the property of being harder at room temperature and softer at the time of vulcanization as compared with the rubber forming the top rubber layer 14T, the studded tire at room temperature The anti-stud performance at the time of use of No. 10 is maintained, and the demolding performance at the time of demolding at the time of vulcanization is improved.
In addition, the site to which the largest strain is applied in use of the studdable tire 10 in which the stud 2 is attached to the attachment hole 3 is the boundary position 37 between the boundary region 33 of the attachment hole 3 and the bottom side 32. In the embodiment, the boundary 14X between the top rubber layer 14T and the base rubber layer 14B is closer to the surface 14a of the tread 14 than the boundary 37 between the boundary region 33 of the mounting hole 3 and the bottom side 32. It is formed. That is, the boundary surface 14X is not positioned at the boundary position 37 where the largest strain is applied when the studdable tire 10 is used, and a large strain does not occur in the boundary surface 14X, so the rubber breaks at the boundary surface 14X. It becomes difficult to do it, and the stud removal performance improves.
In addition, the part that is subjected to the largest strain during demolding is attached at a position X2 that is separated from the boundary position 37 between the boundary region 33 of the mounting hole 3 and the bottom side 32 by the height dimension d of the bottom side 32 The boundary surface 14X is not located at the position where the opening 3t is close to the opening 3t of the hole 3 and a large strain does not occur in the boundary surface 14X at the time of demolding. And the demolding performance is improved.

以上の説明から明らかなように、本発明に係るタイヤ１の好ましい態様は、トレッド１４の表面１４ａ側に設けられたスタッド取付用の取付穴３が、トレッド１４の表面１４ａに開口する開口側部３１と境界領域部３３と底側部３２とを備え、境界領域部３３の内周面３６における取付穴３の中心軸３Ｃに沿った曲面４０の曲率半径Ｒ３は、底側部３２の内周面３６における取付穴３の中心軸３Ｃに沿った曲面４１の曲率半径Ｒ１よりも大きくなるように形成されており、底側部３２の最大径Ｃの位置３６Ｍが、境界領域部３３と底側部３２との境界位置３７と穴底面３５との間の中間位置３９よりも穴底面３５に近い位置に形成されており、内周面（内壁面）３６と穴底面３５との境界が曲面に形成され、境界位置３７と最大径Ｃの位置３６Ｍとを繋ぐ取付穴３の中心軸３Ｃに沿った開口側曲面４１Ａの曲率半径Ｒ１が、穴底面３５と最大径Ｃの位置３６Ｍとを繋ぐ取付穴３の中心軸３Ｃに沿った穴底側曲面４１Ｂの曲率半径Ｒ２よりも大きく形成されており、かつ、トレッド１４を構成するベースゴム層１４Ｂと当該ベースゴム層１４Ｂ上に積層されたトップゴム層１４Ｔとの境界面１４Ｘが、取付穴３の境界領域部３３と底側部３２との境界位置３７よりもトレッド１４の表面１４ａに近い位置に形成されていて、ベースゴム層１４Ｂを形成するゴムが、トップゴム層１４Ｔを形成するゴムと比べて、室温時に硬く、加硫時に柔らかくなる特性を有したゴムにより形成された構成である。 As is clear from the above description, in a preferred embodiment of the tire 1 according to the present invention, the mounting side 3 for stud attachment provided on the surface 14 a side of the tread 14 is an opening side portion opened in the surface 14 a of the tread 14 A radius of curvature R3 of the curved surface 40 along the central axis 3C of the mounting hole 3 in the inner circumferential surface 36 of the boundary region 33 is the inner circumference of the bottom side 32. It is formed to be larger than the radius of curvature R1 of the curved surface 41 along the central axis 3C of the mounting hole 3 in the surface 36, and the position 36M of the maximum diameter C of the bottom side 32 is the boundary region 33 and the bottom side. It is formed at a position closer to the hole bottom 35 than the intermediate position 39 between the boundary position 37 with the portion 32 and the hole bottom 35, and the boundary between the inner circumferential surface (inner wall surface) 36 and the hole bottom 35 is a curved surface. Boundary position 37 and position 3 of maximum diameter C The radius of curvature R1 of the opening side curved surface 41A along the central axis 3C of the mounting hole 3 connecting M and the hole bottom side along the central axis 3C of the mounting hole 3 connecting the hole bottom 35 and the position 36M of the largest diameter C The interface 14X between the base rubber layer 14B forming the tread 14 and the top rubber layer 14T stacked on the base rubber layer 14B, which is larger than the curvature radius R2 of the curved surface 41B, is a mounting hole 3 The rubber forming the base rubber layer 14B is formed at a position closer to the surface 14a of the tread 14 than the boundary position 37 between the boundary region portion 33 and the bottom side portion 32 and the rubber forming the top rubber layer 14T. In comparison, it is a structure formed of a rubber which is hard at room temperature and softens at the time of vulcanization.

尚、上記では、中心軸３Ｃと直交する平面と交わる内周面３６の断面形状が円形に形成された取付穴３を例にして説明したが、当該断面形状が円形以外の形状に形成された取付穴であってもよい。例えば、当該断面形状が、楕円形状、三角形状、四角形状、その他の形状に形成された取付穴であってもよく、特に限定されない。
また、取付穴３の中心軸３Ｃに沿った断面（取付穴３を取付穴３の中心軸３Ｃを含む平面で切断した断面）の形状は、中心軸３Ｃを中心とした左右で異なった形状であってもよい。
また、スタッドは、中心軸と直交する断面形状が、取付穴の断面形状に対応して形成されたスタッドを用いればよい。
また、トップゴム層も、ベースゴム層も、１種のゴムからなる１つの層でなく、複数種のゴムからなる層であってもかまわない。トップゴム層とベースゴム層との境界面での隣接するトップゴム層とベースゴム層との弾性率と位置の関係を満たせば本発明の構成は成立するからである。
また、境界領域部の曲面の曲率半径、開口側曲面の曲率半径、穴底側曲面の曲率半径は、１つの曲率半径である必要はない。即ち、上述した境界領域部の曲面、開口側曲面、穴底側曲面は、複数の曲率半径を有した曲面であってもよいし、一部（例えば途中や始点、終点等）に直線部分を含む曲面であってもよい。 In the above, the mounting hole 3 in which the cross-sectional shape of the inner circumferential surface 36 intersecting with the plane orthogonal to the central axis 3C is formed as a circle has been described as an example, but the cross-sectional shape is formed other than a circular shape. It may be a mounting hole. For example, the cross-sectional shape may be an attachment hole formed in an oval shape, a triangle shape, a square shape, or any other shape, and is not particularly limited.
Further, the shape of the cross section along the central axis 3C of the mounting hole 3 (the cross section obtained by cutting the mounting hole 3 in a plane including the central axis 3C of the mounting hole 3) is different in shape from left to right around the central axis 3C. It may be.
Further, the stud may be a stud whose cross-sectional shape orthogonal to the central axis corresponds to the cross-sectional shape of the mounting hole.
Moreover, neither the top rubber layer nor the base rubber layer may be a layer made of a plurality of types of rubber, not a single layer made of one type of rubber. If the relationship between the elastic modulus and the position between the adjacent top rubber layer and base rubber layer at the interface between the top rubber layer and the base rubber layer is satisfied, the configuration of the present invention is established.
Further, the curvature radius of the curved surface of the boundary region portion, the curvature radius of the opening-side curved surface, and the curvature radius of the hole bottom-side curved surface do not have to be one curvature radius. That is, the curved surface of the boundary area, the curved surface on the opening side, and the curved surface on the bottom of the hole may be a curved surface having a plurality of radiuses of curvature, or some straight portions (e.g. It may be a curved surface.

１タイヤ、２スタッド、３取付穴、３Ｃ中心軸、３ｔ開口、
１４トレッド、１４ａトレッドの表面、３１開口側部、３２底側部、
３３境界領域部、３５穴底面、３６内周面、３６Ｍ最大径の位置、
３７境界位置（底側部の開口側部側端）、３８境界位置（開口側部の底側部側端）、
４１Ａ開口側曲面、４１Ｂ穴底側曲面、Ｃ最大径。 1 tire, 2 studs, 3 mounting holes, 3C central axis, 3t opening,
14 tread, 14a tread surface, 31 opening side, 32 bottom side,
33 boundary area, 35 hole bottom, 36 inner circumferential surface, 36M maximum diameter position,
37 boundary position ( open side end on the bottom side), 38 boundary position (bottom side end on the open side),
41A open side curved surface, 41B hole bottom curved surface, C maximum diameter.

Claims

A tire provided with mounting holes for mounting studs on the surface side of the tread,
The mounting hole is provided on one side in the direction along the central axis of the mounting hole and opens on the tread surface, and the bottom side provided on the other side in the direction along the central axis of the mounting hole A boundary region portion which is a region between the bottom side end of the opening side and the opening side end of the bottom side in the direction along the central axis of the mounting hole ;
Plane along the center axis of the mounting hole in the inner peripheral surface of the front Symbol boundary area portion, the central axis of the mounting holes with gradually increased in diameter toward the bottom side than the bottom side end of the open side It is formed by a curved surface that curves to project in the approaching direction,
The surface of the inner peripheral surface of the bottom side along the central axis of the mounting hole is formed by a curved surface that curves so as to protrude in a direction away from the central axis of the mounting hole,
The radius of curvature of the curved surface along the central axis of the mounting hole in the inner peripheral surface of the boundary region portion is the position of the maximum diameter in the direction along the central axis of the mounting hole in the inner peripheral surface of the bottom side and the bottom A tire characterized by being larger than a curvature radius of an opening side curved surface which is a curved surface between the position of the opening side end of the side.

The position of the largest diameter of the inner peripheral surface of the bottom side is formed closer to the bottom of the hole than the middle position between the boundary between the boundary area and the bottom and the bottom of the mounting hole. The tire according to claim 1, characterized in that:

A hole bottom curved surface, which is a curved surface between the position of the largest diameter in the direction along the central axis of the mounting hole in the inner peripheral surface of the bottom side and the bottom surface of the mounting hole. The tire according to claim 1 or 2, characterized in that the radius of curvature of the tire is larger than the radius of curvature of the tire.