JP2004215703A - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball for increasing a flying distance without a slice or a hook by reducing a spin amount in a shot for which the flying distance is given priority for such as a driver shot, and improving controllability by increasing the spin amount in a shot for which the controllability is given priority for such as an approach shot. <P>SOLUTION: As for the golf ball, a back spin amount S<SB>W#1</SB>at the time of being hit with a driver is ≤2,900rpm, the back spin amount S<SB>SW</SB>at the time of being hit with a sand wedge is ≥6,500rpm, and S<SB>SW</SB>/S<SB>W#1</SB>is ≥2.35. For the golf ball, the primary natural frequency fc of a torsional vibration mode is 1,800-2,800Hz, the thickness of a cover is 0.2-1.3mm, and the Shore D hardness of the cover is 20-60. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３１】
本発明にかかるゴルフボールのソリッドコアは、特に限定はないが、２層以上の複合層特に３層〜７層とすることが好ましい。複数層の場合はコア表面に近い層ほど複素弾性率の値を大きくするほうが好ましい。ｆｃを大きくすることができるからである。
【００３２】
また、ソリッドコアの材質として、特に限定はないが、ゴムおよび／または樹脂が挙げられる。ゴムの場合は、基材ゴム、共架橋剤および架橋開始剤を主体とするゴム組成物を加熱プレス成形して得られる。基材ゴムは、反発に有利なシス結合が４０％以上、好ましくは７０％以上、より好ましくは９０％以上であるポリブタジエンを用いる。その他に、天然ゴム、スチレンブタジエンゴム、イソプレンゴムまたはエチレンプロピレンゴムなどをブレンドすることも可能である。
【００３３】
共架橋剤は、炭素数３個〜８個のα，β−不飽和カルボン酸またはその金属塩を用いることができる。アクリル酸、メタクリル酸の金属塩が好ましい。金属塩として亜鉛塩、マグネシウム塩、カルシウム塩、アルミニウム塩またはナトリウム塩などが挙げられ、亜鉛塩が好ましい。また、共架橋剤は基材ゴム１００質量部に対して２０質量部〜５０質量部用いることができる。
【００３４】
架橋開始剤である有機過酸化物としては、ジクミルパーオキサイド、１，１−ビス（ｔ−ブチルパーオキシ）−３，５−トリメチルシクロヘキサン、２，５−ジメチル−２，５−（ｔ−ブチルパーオキシ）ヘキサン、ジ−ｔ−ブチルパーオキサイドなどが挙げられ、ジクミルパーオキサイドが好ましい。また、架橋開始剤は基材ゴム１００質量部に対して０．２質量部〜５質量部用いることができ、好ましくは０．３質量部〜３質量部である。
【００３５】
また、上記ゴム組成物に、ジフェニルジスルフィド、ジペンタクロロジフェニルジスルフィドなどの有機硫黄化合物を添加して反発性を高めることができる。
また、上記ゴム組成物に、酸化亜鉛、硫酸バリウム、クレーなどの無機充填剤、老化防止剤、色粉などを配合することもできる。上記材料を配合したものをロール、ニーダー、バンバリなどを用いてミキシングして調製したゴム組成物を球状の金型によって加圧加熱して加硫する。加硫条件は、適宜設定することができるが、通常は１３０℃〜２００℃で１０分間〜６０分間、好ましくは１５０℃〜１７５℃で１０分間〜４０分間である。
【００３６】
また、ソリッドコアに用いる樹脂としては、アイオノマー樹脂、またはオレフィン系、スチレン系、エステル系、アミド系もしくはウレタン系の各種熱可塑性エラストマーまたはウレタン系もしくはウレア系の熱硬化性樹脂などが挙げられる。ｆｃを高くし反発弾性、耐久性を向上させる観点から、アイオノマー樹脂、エステル系熱可塑性エラストマー、アミド系熱可塑性エラストマー、ウレタン系熱可塑性エラストマーが好ましい。さらに、ｆｃを高くするために、有機短繊維、たとえばナイロン繊維、アクリル繊維、ポリエステル繊維またはアラミド繊維などを配合してもよい。
【００３７】
ソリッドコアの表面硬度は、ショアＤ硬度で６０〜８０が好ましく、６５〜７５がさらに好ましい。ショアＤ硬度が６０より小さいとｆｃが小さくなり、８０より大きいと打撃時に硬い感じがしてフィーリングが悪くなる。ソリッドコアの直径は３７．９ｍｍ〜４２．４ｍｍが好ましい。また、ソリッドコアに初荷重９８Ｎから終荷重１２７５Ｎ負荷したときの変形量は２．２０ｍｍ〜３．５０ｍｍが好ましく、２．３０ｍｍ〜３．３０ｍｍがより好ましい。かかる変形量が２．２０ｍｍ未満であると打球感が硬く、３．５０ｍｍを超えると反発性能が低下し打球感が重たくなる。
【００３８】
本発明にかかるゴルフボールのカバーの材質として、特に限定はないが、アイオノマー樹脂、またはオレフィン系、スチレン系、エステル系、アミド系もしくはウレタン系の各種熱可塑性エラストマーまたはウレタン系もしくはウレア系の熱硬化性樹脂などが挙げられる。耐久性が良好で薄いカバーが成型できる観点から、熱硬化性ウレタン樹脂が好ましい。
【００３９】
熱硬化性ウレタン樹脂は、イソシアネート基末端ウレタンプレポリマーと硬化剤であるポリアミン化合物またはポリオール化合物を含有する。プレポリマーのイソシアネート基または硬化剤は特に限定されない。必要に応じて、オレイン酸、ラウリル酸などの脂肪族カルボン酸、トリエチルアミンなどの３級アミン、ジラルリルジチンラウリレートなどのスズ系の触媒、酸化チタンなどの顔料、硫酸バリウムなどの充填剤、老化防止剤、紫外線吸収剤、光安定剤、蛍光増白剤などの添加剤を配合することができる。
【００４０】
カバーの厚みは、０．２ｍｍ〜１．３ｍｍ、好ましくは０．３ｍｍ〜０．７ｍｍである。カバー厚みが０．２ｍｍ未満であるとカバーが薄くなりすぎて成型が困難になるとともに引裂強度が低下し耐久性が悪くなり、１．３ｍｍを超えるとｆｃが小さくなる。
【００４１】
カバーのショアＤ硬度は、２０〜６０、好ましくは３０〜４５である。ショアＤ硬度が２０より小さいとｆｃが小さくまた反発性能が低下し、６０より大きいとアプローチショットにおけるバックスピン量が小さくなりコントロール性が悪くなる。
【００４２】
上記ソリッドコアに上記カバーを被覆したゴルフボールは、初荷重９８Ｎから終荷重１２７５Ｎ負荷したときの変形量は、好ましくは２．２０ｍｍ〜３．５０ｍｍ、より好ましくは２．３０ｍｍ〜３．３０ｍｍ、さらに好ましくは２．６０ｍｍ〜３．１０ｍｍである。かかる変形量が２．２０ｍｍ未満であると打球感が硬くなり、３．５０ｍｍを超えると反発性能が低下し飛距離が小さくなり好ましくない。
【００４３】
なお、ゴルフボールの表面に必要に応じてディンプルを形成したり、ペイント、マーキングを施すこともできる。
【００４４】
【実施例】
以下、実施例１〜１３および比較例１〜１０に基づいて本発明を具体的に説明する。
【００４５】
（１）ソリッドコアの作製
表２に示す配合組成のゴム組成物（配合Ａ〜Ｆの組成物）または樹脂組成物（配合Ｇ〜Ｊの組成物）を用いて、表３または表４の構成を有する直径３９．０ｍｍ〜４２．０ｍｍの球状ソリッドコアを得た。配合Ａ〜Ｆについては１６０℃で３０分間加熱圧縮することにより成型し、配合Ｇ〜Ｊについては２４０℃で射出成形することにより成型した。
【００４６】
（２）ボールの作製
表２の配合Ｇ、Ｋ〜Ｍの樹脂組成物を上記ソリッドコアに被覆し、表３または表４の構成を有するゴルフボールを得た。配合Ｇについては２４０℃で射出成形することにより成型した。また、配合Ｋ〜Ｍについては、以下のようにして成型した。まず、表２に記載の配合材料を混合、攪拌して粘ちょうな液体のカバー用組成物を得た。このカバー用組成物をソリッドコアを保持した半球状の金型に速やかに注入し、次いでこれを反転して、カバー用組成物を注入した別の半球状金型と合わせて硬化を行なうことにより成型した。
【００４７】
成型後、得られたゴルフボールを取出し、バリ取りをした後、表面に白色ペイントとクリアペイントを施して、直径４２．８ｍｍ、質量４５．２ｇ〜４５．７ｇのゴルフボールを得た。
【００４８】
【表２】

【００４９】
ここで、表２の配合材料の詳細については以下の通りである。
ＢＲ１８：ＪＳＲ社製ハイシス−１，４−ポリブタジエン（シス成分９６％以上）、アクリル酸亜鉛：日本蒸留社製ＺＮＤＡ−９０Ｓ、酸化亜鉛：東邦亜鉛社製銀嶺Ｒ、ジクミルパーオキサイド：日本油脂社製パークミルＤ、ジフェニルジスルフィド：住友精化製、ハイミラン１６０５：三井デュポンポリケミカル社製Ｎａ中和タイプアイオノマー、ハイミラン１７０６：三井デュポンポリケミカル社製Ｚｎ中和タイプアイオノマー、ハイミラン１８５５：三井デュポンポリケミカル社製Ｚｎ中和タイプアイオノマー、サーリン８１４０：デュポン社製Ｎａ中和タイプアイオノマー、サーリン９１２０：デュポン社製Ｚｎ中和タイプアイオノマー、アジプレンＬＦ８００Ａ：ユニロイヤル社製ＴＤＩ−ＰＴＭＧ系プレポリマー（ＮＣＯ含量＝２．９質量％、遊離ＴＤＩ≦０．１質量％）、アジプレンＬＦ９００Ａ：ユニロイヤル社製ＴＤＩ−ＰＴＭＧ系プレポリマー（ＮＣＯ含量＝３．８質量％、遊離ＴＤＩ≦０．１質量％）、アジプレンＬＦ６５０Ｄ：ユニロイヤル社製ＴＤＩ−ＰＴＭＧ系プレポリマー（ＮＣＯ含量＝７．７質量％、遊離ＴＤＩ≦０．１質量％）、ロンザキュアＭ−ＣＤＥＡ：ロンザ社製２，２’−ジクロロメタン−３，３’，５，５’−テトラメチル−４，４’−ジアミノジフェニルメタン、オレイン酸：和光純薬社製試薬１級、酸化チタン：和光純薬社製試薬。
【００５０】
（３）試験方法
（イ）圧縮変形量：初荷重９８Ｎから終荷重１２７５Ｎの荷重をかけたときのゴルフボールの圧縮変形量（ｍｍ）を測定した。
（ロ）Ｗ＃１飛距離：スイングロボットにチタン製１番ウッドクラブ（Ｗ＃１；住友ゴム工業社製ＸＸＩＯ ＴＷＩＮ ＡＸ−ＳＯＬＥ Ｗ＃１（ロフト角：１０°、ライ角：５６°、クラブ長さ：４５インチ、シャフト：カーボンシャフト（ＸＸＩＯ ＭＰ２００ カーボンシャフト Ｓ）、ヘッド素材：チタン合金））を装着し、ヘッド速度４５ｍ／ｓで打撃した際のゴルフボールの打撃地点から停止地点までの距離（ｍ）を測定した。
（ハ）バックスピン量（Ｓ_Ｗ＃１またはＳ_ＳＷ）：スイングロボットにチタン製１番ウッドクラブ（Ｗ＃１；住友ゴム工業社製ＸＸＩＯ ＴＷＩＮ ＡＸ−ＳＯＬＥＷ＃１（ロフト角：１０°、ライ角：５６°、クラブ長さ：４５インチ、シャフト：カーボンシャフト（ＸＸＩＯ ＭＰ２００ カーボンシャフト Ｓ）、ヘッド素材：チタン合金））またはサンドウエッジ（ＳＷ；住友ゴム工業社製スリクソンＩ−２０１（ロフト角：５７°、ライ角：６３°、クラブ長さ：３５．５インチ、シャフト：カーボンシャフト（ツアーブラックＶ２３ Ｓ）、ヘッド素材：軟鉄））を装着し、所定のヘッド速度（Ｗ＃１については４５ｍ／ｓ、ＳＷについては２１ｍ／ｓ）で打撃したゴルフボールを連続写真撮影することによりバックスピン量（ｒｐｍ）を求めた。
（ニ）縦たわみ方向の一次固有振動数ｆｎ：上記の図２に示す方法にしたがって測定した。
（ホ）ねじり振動モードの一次固有振動数ｆｃ：上記の図３に示す方法にしたがって測定した。
実施例１〜１３についての諸特性値を表３に、比較例１〜１０についての諸特性値を表４にまとめる。
【００５１】
【表３】

【００５２】
【表４】

【００５３】
実施例１〜１３については、ｆｃ、ｆｎ、ｆｃ／ｆｎ、カバー厚み、カバーショアＤ硬度などを所定の範囲内に設計することにより、いずれの場合もＳ_Ｗ＃１、Ｓ_ＳＷ、およびＳ_ＳＷ／Ｓ_Ｗ＃１が特許請求の範囲内にあるゴルフボールが得られる。
これに対して、比較例１、５ではｆｃが小さいため、比較例９ではｆｃ／ｆｎが小さいため、比較例１、４ではカバー厚みが厚すぎていずれもＳ_Ｗ＃１が大きくなり飛距離が小さい。また、比較例７ではカバー厚みが薄すぎてＳ_ＳＷが小さくコントロール性が悪く、比較例３、１０はカバーのショアＤ硬度が大きくｆｎが大きいためＳ_ＳＷが小さくコントロール性が悪い。
【００５４】
今回開示された実施の形態および実施例はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。
【００５５】
【発明の効果】
上記のように、本発明においては、ｆｃ、ｆｎ、ｆｃ／ｆｎ、カバー厚み、カバーショアＤ硬度などを所定の範囲内に設計し、Ｓ_Ｗ＃１、Ｓ_ＳＷ、およびＳ_ＳＷ／Ｓ_Ｗ＃１を所定の範囲内に調製することにより、ショットの目的に応じてスピン量の調整が可能なゴルフボールを提供すること、すなわち、ドライバーショットなどの飛距離を優先するショットにおいてスピン量が小さくすることによりスライスやフックがなく飛距離が大きく、アプローチチョットなどのコントロール性を優先するショットにおいてスピン量を大きくすることによりコントロール性が向上したゴルフボールを提供することができる。
【図面の簡単な説明】
【図１】（Ａ）はゴルフボールがクラブに打撃される際の概略側面図である。（Ｂ）はゴルフボールがクラブに打撃される際の接触力と時間との関係を示す図である。
【図２】ｆｎを測定する装置の概略図である。
【図３】ｆｃを測定する装置の概略図である。
【図４】（Ａ）はボール固定冶具の斜視図である。（Ｂ）はボール固定冶具の側面図である。
【符号の説明】
１，１１ レーザードップラー速度計、２，１２ マニピュレーター、３，１３ ＦＦＴアナライザー、４，１４ レーザー照射部、５，１５ パワーアンプ、６，１６ 加振機アンプ、７，１７ 加振機、７ａ，１７ａ 取付け台、１７ｂ 支持部、８ ボール固定冶具、８ａ 基底部、８ｂ フランジ部、９，１９
加速度ピックアップ、１０，２０ 反射テープ。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a golf ball having a small spin amount for a driver shot and an increased flight distance, and a large spin amount for an approach shot and increased controllability.
[0002]
[Prior art]
The spin amount of a golf ball is an important property that governs the flight distance performance and control performance. In shots that give priority to the flight distance such as driver shots, if the spin amount is large, the side spin will be large, so slicing and hooking will be applied, it will not fly in the direction intended by the golfer, it will be a trajectory that blows up and the flight distance will be small .
Therefore, in the above shot, the smaller the spin amount, the better. On the other hand, in shots that prioritize controllability such as approach chot from the side of the green, if the spin amount is small, the ball will roll a long distance after falling, making it difficult to stop the ball at the intended location. The larger is better.
[0003]
As a technique related to a golf ball having a small spin rate in a shot giving priority to a flight distance, a golf ball including a core having a reel compression ratio of at least 0.076 and a cover having a Shore D hardness of at least 65 has been proposed (for example, See Patent Document 1.). According to this technique, a golf ball having a small spin amount is obtained by making the core relatively soft and the cover relatively hard, but at the same time, the spin amount in a shot in which control is given priority is reduced, and controllability is reduced.
[0004]
In addition, as a technique relating to a golf ball having a small spin amount in a shot in which the flight distance is prioritized, a ratio fc / fn of a primary natural frequency fc of the torsional vibration mode to a primary natural frequency fn of the longitudinal bending direction is 2.22. Golf balls satisfying ≦ (fc / fn) ≦ 2.45 have been proposed (for example, see Patent Document 2). Although this technique can reduce the spin rate on a driver shot, the spin rate on an approach shot is also reduced due to the use of a highly elastic material for the cover and a relatively thick wall, resulting in reduced controllability.
[0005]
On the other hand, as a technique relating to a golf ball having a large spin amount in a shot giving priority to controllability, a ratio fc / fn of a primary natural frequency fc of the torsional vibration mode to a primary natural frequency fn of the longitudinal bending direction is 2.45. A golf ball satisfying <(fc / fn) ≦ 2.65 has been proposed (for example, see Patent Document 3).
Although this technique can increase the spin rate on approach shots, the spin rate on driver shots also increases and the flight distance decreases because the complex elastic modulus of Gabber is set to be greater than the complex elastic modulus of the core.
[0006]
As a technique for adjusting the spin amount, many combinations of many factors such as hardness, rigidity distribution, thickness, and specific gravity of each layer of a multi-piece golf ball have been proposed. When the spin amount is reduced, the spin amount in the approach shot also decreases, and when the spin amount in the approach shot is increased, the spin amount in the driver shot increases, and the spin amount cannot be adjusted according to the purpose of the shot.
[0007]
[Patent Document 1]
JP-A-06-312032
[0008]
[Patent Document 2]
JP 2002-263216 A
[0009]
[Patent Document 3]
JP-A-2002-263217
[0010]
[Problems to be solved by the invention]
The present invention provides a golf ball capable of adjusting the spin amount according to the purpose of a shot, that is, by reducing the spin amount in a shot such as a driver shot in which flying distance is prioritized, the golf ball can fly without slicing or hooking. It is an object of the present invention to provide a golf ball with a large distance and a high controllability by increasing the spin amount in a shot in which controllability such as approach chot is prioritized.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the golf ball according to the present invention has a backspin amount S when hit with the first wood. _{W # 1} Is 2900 rpm or less, the backspin amount S when hit with a sand wedge _SW Is not less than 6500 rpm and S _SW / S _{W # 1} Is 2.35 or more. Where S _{W # 1} Is 2850 rpm or less, _SW Is not less than 6700 rpm and S _SW / S _{W # 1} Is preferably 2.40 or more.
[0012]
Further, the golf ball according to the present invention is a golf ball having a solid core and a cover covering the solid core, wherein the primary natural frequency fc of the golf ball in a torsional vibration mode is 1800 Hz to 2800 Hz, and the thickness of the cover is Is 0.2 mm to 1.3 mm, and the Shore D hardness of the cover is 20 to 60. Here, the ratio fc / fc between the primary natural frequency fc of the torsional vibration mode and the primary natural frequency fn of the longitudinal bending direction is 1.9 to 2.5, and the primary natural frequency fc of the torsional vibration mode is Preferably, the frequency is 2,000 Hz to 2,600 Hz, the thickness of the cover is 0.3 mm to 0.7 mm, or the Shore D hardness of the cover is 30 to 45. Further, it is preferable that the solid core is composed of two or more layers, and that the outermost layer of the solid core has a Shore D hardness greater than that of the cover.
[0013]
Further, the golf ball according to the present invention is a golf ball having a solid core and a cover covering the solid core, wherein the primary natural frequency fc of the golf ball in a torsional vibration mode is 1800 Hz to 2800 Hz, and the thickness of the cover is Is 0.2 mm to 1.3 mm, the cover has a Shore D hardness of 20 to 60, and the ratio fc / fn of the primary natural frequency fc in the torsional vibration mode to the primary natural frequency fn in the longitudinal bending direction is 1.9 to 1.9. 2.5, the amount of deformation when the golf ball is loaded with an initial load of 98 N to a final load of 1275 N is 2.6 mm to 3.1 mm, or the primary natural frequency fc of the torsional vibration mode is 2000 Hz to 2600 Hz, The primary natural frequency fn in the vertical deflection direction is 900 Hz to 1100 Hz and the ratio fc / fn between fc and fn is 2.1 to 2.4. Rukoto is preferable.
[0014]
Further, in the golf ball described above, it is preferable that the primary natural frequency fn in the vertical deflection direction is 800 Hz to 1200 Hz.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The golf ball according to the present invention has the backspin amount S when hit with the first wood. _{W # 1} Is 2900 rpm or less, the backspin amount S when hit with a sand wedge _SW Is not less than 6500 rpm and S _SW / S _{W # 1} Is 2.35 or more.
Where S _{W # 1} Is 2850 rpm or less, S _SW Is not less than 6700 rpm and S _SW / S _{W # 1} Is preferably 2.40 or more. Furthermore, S _{W # 1} Is less than 2800 rpm, S _SW Is 6750 rpm or more, and S _SW / S _{W # 1} Is more preferably 2.45 or more. S _{W # 1} The smaller the distance, the greater the flight distance on driver shots, _SW Is smaller, the controllability in the approach shot is improved. Also, S _SW / S _{W # 1} The larger the value, the larger the adjustment range of the spin amount according to the purpose of the shot.
[0016]
The behavior of a golf ball when hit with a relatively large force such as a driver shot will be described with reference to FIG. FIG. 1A shows a schematic side view when a golf ball is hit by a club, and FIG. 1B shows the relationship between contact force (Ft) and time at that time. First, the golf ball is twisted on the contact surface with the club face, and a force (Ft) is applied in a direction of applying a back spin to the golf ball. However, this force peaks at some point and then decreases and reverses, and a force is applied in the direction of applying top spin to the golf ball. Further, the force decreases after the peak, and when the force becomes zero, the golf ball leaves the club face and is released into the air.
Here, as the natural frequency in the torsional direction (the natural frequency fc in the torsional vibration mode) increases, the rotation direction of the golf ball reverses at an earlier timing during the contact, and the impulse (Rb) acting on the top spin side increases. Therefore, the backspin amount decreases.
[0017]
Therefore, in order to reduce the amount of back spin in a driver shot, it is necessary to apply a large amount of top spin-side force to the golf ball while the golf ball is in contact with the club face. For that purpose, there are methods of increasing the contact time and shortening the time until the force is reversed from the back spin side to the top spin side.
[0018]
On the other hand, when the golf ball is hit with a relatively small force, such as an approach shot, the golf ball separates from the club face before the reversal from the back spin side to the top spin side occurs. fc has no relation to the back spin amount of the approach shot.
[0019]
The backspin amount of the approach shot is greatly affected by the Shore D hardness of the cover located on the outermost layer of the ball. That is, when the Shore D hardness is low, the frictional force between the golf ball and the club face increases, and the force of applying the backspin from the club to the ball can be efficiently transmitted to the ball, so that the backspin amount increases. Therefore, in order to increase the backspin amount in the approach shot, it is preferable to decrease the Shore D hardness of the cover.
[0020]
In view of the above, the golf ball according to the present invention is a golf ball having a solid core and a cover covering the solid core, wherein the primary natural frequency fc of the torsional vibration mode of the golf ball is 1800 Hz to 2800 Hz, The cover has a thickness of 0.2 mm to 1.3 mm, and the cover has a Shore D hardness of 20 to 60.
[0021]
In driver shots, the higher the natural frequency of the torsional vibration mode, the more quickly the golf ball rotates in the direction of rotation during contact between the golf ball and the club face, and the larger the impulse acting on the top spin side, the greater the backspin amount. Becomes smaller. If fc is less than 1800 Hz, the time until reversal becomes longer and the amount of back spin increases, and if fc is greater than 2800 Hz, the torsional rigidity becomes too large and the feel at the time of impact is deteriorated.
[0022]
In approach shots, the smaller the Shore D hardness of the cover is, the better the back spin amount is. However, when the Shore D hardness of the cover is reduced, the rigidity of the golf ball in the twisting direction is reduced, and fc is reduced.
When the Shore D hardness of the cover is set to 20 to 60 at a cover thickness of 1.3 mm to 2.5 mm, fc decreases to 1000 Hz to 1700 Hz. If the cover has a Shore D hardness of 60 to 80 with the same cover thickness, the fc becomes 1700 Hz to 2500 Hz, but the backspin amount in the approach shot decreases. Therefore, the thickness of the cover was set to 0.2 mm to 1.3 mm, and the shore D of the cover was set to 20 to 60.
[0023]
Further, the golf ball according to the present invention is a golf ball having a solid core and a cover covering the solid core, wherein the primary natural vibration fc of the golf ball in a torsional vibration mode is 1800 Hz to 2800 Hz, and the vertical length of the golf ball is The primary natural frequency fn in the bending direction is 800 Hz to 1200 Hz, the thickness of the cover is 0.2 mm to 1.3 mm, and the Shore D hardness of the cover is 20 to 60. Further, it is preferable that the ratio fc / fn of the primary natural frequency fc of the torsional vibration mode of the golf ball to the primary natural frequency fn of the longitudinal deflection direction is 1.9 to 2.5.
[0024]
As described above, the larger the fc is, the faster the rotation direction of the golf ball is reversed from the backspin side to the topspin side at the earlier timing during the contact between the golf ball and the club in the driver shot, and the impulse acting on the topspin side is increased. , The backspin amount becomes smaller. From such a viewpoint, fc is 1800 Hz to 2800 Hz, and preferably 2,000 Hz to 2600 Hz. If fc is less than 1800 Hz, the time until reversal becomes longer and the amount of backspin increases, and if fc is greater than 2800 Hz, the torsional rigidity becomes too large and the ball feels hard when hit, resulting in poor feeling.
[0025]
On the other hand, the contact time can be prolonged by reducing the rigidity in the vertical direction and reducing fn.
From such a viewpoint, fn is 800 Hz to 1200 Hz, and preferably 900 Hz to 1100 Hz. If fn is less than 800 Hz, the contact time becomes longer and the backspin amount becomes smaller, but the feel is heavy at the time of hitting and the feeling is poor. Ring gets worse.
[0026]
Further, if the rigidity of the ball is merely reduced to reduce fn, fc is reduced and the backspin amount is not reduced. If the rigidity of the ball is merely increased to increase fc, fn is increased and the backspin is increased. The amount does not decrease. To optimize these balances, fc / fn is between 1.9 and 2.5, preferably between 2.1 and 2.4.
[0027]
Here, a method of measuring the primary natural frequency fn and the primary natural frequency fc of the torsional vibration mode, which are physical constants specific to the present invention, in the longitudinal deflection direction will be described below. First, a method of measuring the primary natural frequency fn in the vertical deflection direction will be described with reference to FIG.
(1) The golf ball G is polished on the support 17b of the mount 17a of the vibrator 17 so that the golf ball becomes a flat circle having a diameter of 10 mm, and this portion is fixed with an instant adhesive.
(2) The acceleration pickup 19 is mounted below the mounting table 17a of the vibrator 17.
(3) The golf ball G is vibrated by the vibrator, and the laser irradiation unit 14, the manipulator 12, and the laser Doppler velocimeter 11 transmit the vibration velocity V of the golf ball via the reflection tape 20 arranged on the upper surface of the golf ball. Is measured. This uses the principle of a known laser Doppler vibrometer. The reflective tape used was a Scotchlite reflective tape manufactured by Sumitomo 3M Limited, and a tape of about 5 mm square was attached to the ball with the reflective surface facing the laser irradiation side.
(4) The voltage signal output from the acceleration pickup 19 is amplified by the power amplifier 15 and then input to the FFT analyzer 13. On the other hand, the measured velocity V is taken into the FFT analyzer 13 from the laser Doppler velocity meter 11.
(5) From the acceleration A and the velocity V measured by the FFT analyzer 13, a frequency transfer function G (s) is obtained by the following equation.
G (s) = Fourier transform of output velocity V / Fourier transform of input acceleration A
(6) From the frequency transfer function G (s), the largest peak value among the peaks in the frequency range of 400 Hz to 4000 Hz is read as the frequency of the maximum value. In FIG. 2, the shaker amplifier 16 controls the amplitude of the vibration of the shaker 17 and has a function of amplifying the voltage signal output from the FFT analyzer 13.
[0028]
Next, a method of measuring the primary natural frequency fc in the torsional vibration mode will be described with reference to FIG.
(A) The golf ball G is disposed on the mounting table 7a via the ball fixing jig 8. Then, the golf ball is fixed to the flange portion 8b of the ball fixing jig 8, and is fixed away from the base portion 8a of the ball fixing jig. In order to fix the golf ball G to the flange portion 8b, the golf ball is polished so as to have a flat circular shape with a diameter of 10 mm, an instant adhesive is attached to this portion, and the golf ball G is fixed to the flange portion 8b. The golf ball is positioned so that the extension line through which the razor line R passes through the golf ball is located at the point p of the base portion 8a.
[0029]
Here, the material and dimensions of the ball fixing jig 8 are as follows.
The material of the ball fixing jig 8 is stainless steel (SUS), and the weight is 379.5 g. As shown in FIG. 4A showing a perspective view and FIG. 4B showing a side view, the ball fixing jig 8 includes a vertical flange portion 8b and a base portion 8a. The dimensions of each part are as follows.
Base dimensions
L: 93.9 mm L1: 68.9 mm L2: 36.37 mm W: 25 mm H2: 15 mm
Vertical dimension
H: 47.35 mm H1: 22.35 mm FL: 15 mm
(B) The acceleration pickup 9 is mounted below the mounting table 7a of the vibrator 7.
(C) The golf ball G is vibrated by the vibrator 7, and the vibration speed of the golf ball is measured by the laser irradiator 4, the manipulator 2 and the laser Doppler velocimeter 1 via the reflection tape 10 arranged on the upper surface of the golf ball. Measure V '. This uses the principle of a known laser Doppler vibrometer. The reflective tape used was a Scotchlite reflective tape manufactured by Sumitomo 3M Limited, and a tape of about 5 mm square was attached to the ball with the reflective surface facing the laser irradiation side.
(D) The voltage signal output from the acceleration pickup 9 is amplified by the power amplifier 5 and then input to the FFT analyzer 3. On the other hand, the measured velocity V ′ is taken into the FFT analyzer 3 from the laser Doppler velocimeter 1.
(E) From the acceleration A 'and the velocity V' measured by the FFT analyzer, a frequency transfer function G '(s) is obtained by the following equation.
G ′ (s) = Fourier transform of output velocity V ′ / Fourier transform of input acceleration A ′
Here, the largest peak value among the peaks in the frequency range of 400 Hz to 4000 Hz is read from the frequency transfer function as the frequency of the maximum value. Table 1 shows the specifications of various measuring instruments used for the measurement of fn and fc.
[0030]
[Table 1]

[0031]
Although the solid core of the golf ball according to the present invention is not particularly limited, it is preferable to have two or more composite layers, particularly three to seven layers. In the case of a plurality of layers, it is preferable that the closer to the core surface, the larger the value of the complex modulus. This is because fc can be increased.
[0032]
The material of the solid core is not particularly limited, but includes rubber and / or resin. In the case of rubber, a rubber composition mainly comprising a base rubber, a co-crosslinking agent and a crosslinking initiator is obtained by hot press molding. As the base rubber, a polybutadiene having a cis bond advantageous for repulsion of 40% or more, preferably 70% or more, more preferably 90% or more is used. In addition, it is also possible to blend natural rubber, styrene butadiene rubber, isoprene rubber or ethylene propylene rubber.
[0033]
As the co-crosslinking agent, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof can be used. Metal salts of acrylic acid and methacrylic acid are preferred. Examples of the metal salt include a zinc salt, a magnesium salt, a calcium salt, an aluminum salt and a sodium salt, and a zinc salt is preferable. The co-crosslinking agent can be used in an amount of 20 parts by mass to 50 parts by mass based on 100 parts by mass of the base rubber.
[0034]
Examples of the organic peroxide which is a crosslinking initiator include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, and 2,5-dimethyl-2,5- (t- (Butylperoxy) hexane, di-t-butyl peroxide and the like, with dicumyl peroxide being preferred. The crosslinking initiator can be used in an amount of 0.2 to 5 parts by mass, preferably 0.3 to 3 parts by mass, based on 100 parts by mass of the base rubber.
[0035]
Further, an organic sulfur compound such as diphenyl disulfide and dipentachlorodiphenyl disulfide can be added to the rubber composition to increase the resilience.
Further, an inorganic filler such as zinc oxide, barium sulfate, and clay, an antioxidant, a color powder, and the like may be added to the rubber composition. A rubber composition prepared by mixing the above materials with a roll, kneader, Banbury or the like is vulcanized by applying pressure and heat to a spherical mold. The vulcanization conditions can be appropriately set, but are usually from 130 ° C to 200 ° C for 10 minutes to 60 minutes, preferably from 150 ° C to 175 ° C for 10 minutes to 40 minutes.
[0036]
Examples of the resin used for the solid core include an ionomer resin, olefin-based, styrene-based, ester-based, amide-based or urethane-based thermoplastic elastomers, and urethane- or urea-based thermosetting resins. From the viewpoint of increasing fc and improving rebound resilience and durability, ionomer resins, ester-based thermoplastic elastomers, amide-based thermoplastic elastomers, and urethane-based thermoplastic elastomers are preferred. Further, in order to increase fc, organic short fibers such as nylon fibers, acrylic fibers, polyester fibers or aramid fibers may be blended.
[0037]
The surface hardness of the solid core is preferably 60 to 80 in Shore D hardness, and more preferably 65 to 75. If the Shore D hardness is smaller than 60, fc becomes smaller, and if it is larger than 80, the golf ball feels hard at the time of hitting and has a poor feeling. The diameter of the solid core is preferably 37.9 mm to 42.4 mm. Further, the amount of deformation when an initial load of 98 N to a final load of 1275 N is applied to the solid core is preferably 2.20 mm to 3.50 mm, more preferably 2.30 mm to 3.30 mm. If the deformation amount is less than 2.20 mm, the shot feeling is hard, and if it exceeds 3.50 mm, the resilience performance is reduced and the shot feeling becomes heavy.
[0038]
The material of the cover of the golf ball according to the present invention is not particularly limited, but may be an ionomer resin, or an olefin-based, styrene-based, ester-based, amide-based or urethane-based thermoplastic elastomer or a urethane-based or urea-based thermosetting resin. Resins. A thermosetting urethane resin is preferable from the viewpoint of forming a thin cover having good durability.
[0039]
The thermosetting urethane resin contains an isocyanate group-terminated urethane prepolymer and a polyamine compound or a polyol compound as a curing agent. The isocyanate group or curing agent of the prepolymer is not particularly limited. If necessary, oleic acid, aliphatic carboxylic acids such as lauric acid, tertiary amines such as triethylamine, tin-based catalysts such as dilarylditin laurate, pigments such as titanium oxide, fillers such as barium sulfate, Additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, and a fluorescent whitening agent can be added.
[0040]
The cover has a thickness of 0.2 mm to 1.3 mm, preferably 0.3 mm to 0.7 mm. When the cover thickness is less than 0.2 mm, the cover becomes too thin to make molding difficult, and the tear strength is lowered to deteriorate the durability. When the cover thickness is more than 1.3 mm, fc becomes small.
[0041]
The Shore D hardness of the cover is 20-60, preferably 30-45. If the Shore D hardness is less than 20, the fc is small and the resilience performance is reduced. If the Shore D hardness is more than 60, the backspin amount in approach shots is small and controllability is poor.
[0042]
In the golf ball in which the solid core is covered with the cover, the amount of deformation when an initial load of 98 N is applied to a final load of 1275 N is preferably 2.20 mm to 3.50 mm, more preferably 2.30 mm to 3.30 mm, and furthermore Preferably it is 2.60 mm to 3.10 mm. If the deformation amount is less than 2.20 mm, the shot feeling becomes hard, and if it exceeds 3.50 mm, the resilience performance is reduced and the flight distance is undesirably reduced.
[0043]
In addition, dimples can be formed on the surface of the golf ball, and paint and marking can be applied as necessary.
[0044]
【Example】
Hereinafter, the present invention will be specifically described based on Examples 1 to 13 and Comparative Examples 1 to 10.
[0045]
(1) Production of solid core
Using a rubber composition (compositions A to F) or a resin composition (compositions G to J) having the composition shown in Table 2, a diameter of 39.0 mm or more having the composition shown in Table 3 or Table 4 was used. A 42.0 mm spherical solid core was obtained. Formulations A to F were molded by heating and compression at 160 ° C. for 30 minutes, and Formulations G to J were molded by injection molding at 240 ° C.
[0046]
(2) Production of ball
The solid core was coated with the resin composition of Formulations G and KM of Table 2 to obtain a golf ball having the configuration of Table 3 or Table 4. Formulation G was molded by injection molding at 240 ° C. In addition, moldings K to M were molded as follows. First, the compounding materials shown in Table 2 were mixed and stirred to obtain a viscous liquid cover composition. This cover composition is quickly injected into a hemispherical mold holding a solid core, then inverted, and cured together with another hemispherical mold into which the cover composition has been injected. Molded.
[0047]
After molding, the obtained golf ball was taken out, deburred, and then subjected to white paint and clear paint on the surface to obtain a golf ball having a diameter of 42.8 mm and a mass of 45.2 g to 45.7 g.
[0048]
[Table 2]

[0049]
Here, the details of the compounding materials in Table 2 are as follows.
BR18: High cis-1,4-polybutadiene (cis component 96% or more) manufactured by JSR, zinc acrylate: ZNDA-90S manufactured by Nippon Distillery, zinc oxide: Ginrei R manufactured by Toho Zinc, dicumyl peroxide: Nippon Yushi Parkmill D, diphenyl disulfide: Sumitomo Seika Chemical Co., Ltd., Himilan 1605: Na neutralization type ionomer manufactured by Mitsui Dupont Polychemicals Co., Ltd., Himilan 1706: Zn neutralization type ionomer manufactured by Mitsui Dupont Polychemicals Co., Ltd., Himilan 1855: Mitsui Dupont Polychemicals Co., Ltd. Surin 8140: Na neutralized type ionomer manufactured by DuPont, Surlyn 9120: Zn neutralized type ionomer manufactured by DuPont, Adiprene LF800A: TDI-PTMG prepolymer (NCO content = 0.9% by mass, free TDI ≦ 0.1% by mass), adiprene LF900A: TDI-PTMG prepolymer (NCO content = 3.8% by mass, free TDI ≦ 0.1% by mass) manufactured by Uniroyal Corporation, adiprene LF650D : TDI-PTMG prepolymer manufactured by Uniroyal (NCO content = 7.7% by mass, free TDI ≦ 0.1% by mass), LonzaCure M-CDEA: 2,2′-dichloromethane-3,3 ′ manufactured by Lonza , 5,5'-Tetramethyl-4,4'-diaminodiphenylmethane, oleic acid: reagent class 1 manufactured by Wako Pure Chemical Industries, titanium oxide: reagent manufactured by Wako Pure Chemical Industries, Ltd.
[0050]
(3) Test method
(A) Amount of compressive deformation: The amount of compressive deformation (mm) of a golf ball when a load from an initial load of 98N to a final load of 1275N was applied was measured.
(B) W # 1 flight distance: No. 1 wood club made of titanium (W # 1; XXIO TWIN AX-SOLE W # 1 manufactured by Sumitomo Rubber Industries, Ltd. (loft angle: 10 °, lie angle: 56 °, club) Length: 45 inches, Shaft: Carbon shaft (XXIO MP200 carbon shaft S), Head material: Titanium alloy)), and distance from the impact point to the stop point of the golf ball when hit at a head speed of 45 m / s (m) ) Was measured.
(C) Back spin amount (S _{W # 1} Or S _SW ): No. 1 wood club made of titanium (W # 1; XXIO TWIN AX-SOLEW # 1 manufactured by Sumitomo Rubber Industries, Ltd.) (loft angle: 10 °, lie angle: 56 °, club length: 45 inches, shaft: Carbon shaft (XXIO MP200 carbon shaft S), head material: titanium alloy) or sand wedge (SW; Srixon I-201 manufactured by Sumitomo Rubber Industries, Ltd. (loft angle: 57 °, lie angle: 63 °, club length: 35.5) Inch, shaft: carbon shaft (Tour Black V23 S), head material: soft iron)), and a continuous golf ball hit at a predetermined head speed (45 m / s for W # 1 and 21 m / s for SW) The backspin amount (rpm) was determined by taking a photograph.
(D) Primary natural frequency fn in the longitudinal deflection direction: measured according to the method shown in FIG.
(E) Primary natural frequency fc in torsional vibration mode: measured in accordance with the method shown in FIG.
Table 3 summarizes various characteristic values of Examples 1 to 13 and Table 4 summarizes various characteristic values of Comparative Examples 1 to 10.
[0051]
[Table 3]

[0052]
[Table 4]

[0053]
In Examples 1 to 13, in all cases, fc, fn, fc / fn, cover thickness, cover shore D hardness, etc. were designed within predetermined ranges, and thus S _{W # 1} , S _SW , And S _SW / S _{W # 1} Is within the scope of the claims.
On the other hand, since fc is small in Comparative Examples 1 and 5, and fc / fn is small in Comparative Example 9, the cover thickness is too large in Comparative Examples 1 and 4 and S _{W # 1} And the flight distance is short. In Comparative Example 7, the cover thickness was too small and S _SW In Comparative Examples 3 and 10, the cover had a large Shore D hardness and a large fn. _SW But small and poor controllability.
[0054]
The embodiments and examples disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0055]
【The invention's effect】
As described above, in the present invention, fc, fn, fc / fn, cover thickness, cover shore D hardness and the like are designed within predetermined ranges, and S _{W # 1} , S _SW , And S _SW / S _{W # 1} By providing the golf ball within a predetermined range, it is possible to provide a golf ball capable of adjusting the spin amount according to the purpose of the shot, that is, to reduce the spin amount in a shot such as a driver shot that gives priority to the flight distance Accordingly, a golf ball having a great flight distance without slices or hooks, and having an increased spin amount in a shot in which controllability such as approach chot is prioritized can be provided.
[Brief description of the drawings]
FIG. 1A is a schematic side view when a golf ball is hit with a club. (B) is a diagram showing a relationship between contact force and time when a golf ball is hit by a club.
FIG. 2 is a schematic diagram of an apparatus for measuring fn.
FIG. 3 is a schematic diagram of an apparatus for measuring fc.
FIG. 4A is a perspective view of a ball fixing jig. (B) is a side view of the ball fixing jig.
[Explanation of symbols]
1,11 laser Doppler velocimeter, 2,12 manipulator, 3,13 FFT analyzer, 4,14 laser irradiation part, 5,15 power amplifier, 6,16 shaker amplifier, 7,17 shaker, 7a, 17a Mounting stand, 17b support, 8 ball fixing jig, 8a base, 8b flange, 9, 19
Acceleration pickup, 10,20 reflective tape.

Claims (11)

The back spin amount _{SW # 1} when hit with the first wood is 2900 rpm or less, the back spin amount _SW when hit with a sand wedge is 6500 rpm or more, and S _SW / S _{W # 1} is 2.35. A golf ball characterized by the above. The back spin amount _{SW # 1} when hit with the first wood is 2850 rpm or less, the back spin amount _SW when hit with a sand wedge is 6700 rpm or more, and S _SW / S _{W # 1} is 2.40. A golf ball characterized by the above. A golf ball having a solid core and a cover covering the solid core, wherein the primary natural frequency fc of the golf ball in a torsional vibration mode is 1800 Hz to 2800 Hz, and the thickness of the cover is 0.2 mm to 1.3 mm. A golf ball having a cover having a Shore D hardness of 20 to 60. 4. The golf ball according to claim 3, wherein a ratio fc / fn of the primary natural frequency fc of the torsional vibration mode to the primary natural frequency fn of the longitudinal bending direction is 1.9 to 2.5. 5. The golf ball according to claim 3, wherein the primary natural frequency fc of the torsional vibration mode is 2,000 Hz to 2,600 Hz. The golf ball according to claim 3, wherein the cover has a thickness of 0.3 mm to 0.7 mm. The golf ball according to claim 3, wherein the cover has a Shore D hardness of 30 to 45. 4. The golf ball according to claim 3, wherein the solid core is composed of two or more layers, and the outermost layer of the solid core has a Shore D hardness greater than the Shore D hardness of the cover. The golf ball according to claim 3, wherein the primary natural frequency fn in the longitudinal deflection direction is 800 Hz to 1200 Hz. The golf ball according to claim 3, wherein an amount of deformation of the golf ball when an initial load of 98 N to a final load of 1275 N is applied is 2.20 mm to 3.50 mm. 5. The primary natural frequency fc of the torsional vibration mode is 2000 Hz to 2600 Hz, the primary natural frequency fn of the longitudinal bending direction is 900 Hz to 1100 Hz, and the ratio fc / fn between fc and fn is 2.1 to 2.4. Golf ball.

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