JP3613754B2

JP3613754B2 - Machine tool spindle equipment

Info

Publication number: JP3613754B2
Application number: JP12534199A
Authority: JP
Inventors: 直弘池田
Original assignee: Niigata Machine Techno Co Ltd
Current assignee: Niigata Machine Techno Co Ltd
Priority date: 1999-04-30
Filing date: 1999-04-30
Publication date: 2005-01-26
Anticipated expiration: 2019-04-30
Also published as: JP2000317754A

Description

【０００１】
【発明の属する技術分野】
本発明は、ハウジングに主軸をアンギュラ玉軸受等のころがり軸受を介して回転自在に支持した工作機械の主軸装置に関する。
【０００２】
【従来の技術】
工作機械の主軸装置として、図７に示すものが知られている。
この主軸装置は、ハウジング１内に、主軸２が、前後２組（図７では左側を前とする。）のころがり軸受３，４で回転自在に支持され、主軸２を回転させる電動モータ６がころがり軸受３，４の間に設けられたものであって、ハウジング１と後側のころがり軸受４との間に、可動スリーブ部材７を、ころがり軸受４の外輪に嵌着するとともにスライドボールベアリング８によって主軸２の軸方向に移動自在に嵌挿し、予圧ばね９で後側に付勢してころがり軸受に予圧をかける構造となっている。
なお、ハウジング１は、その後端にボルト１１で着脱自在に一体に固定された後部部材（リヤハウジング）１ａを有し、可動スリーブ部材７はその後部部材１ａに嵌挿されている。スライドボールベアリング８は、発熱体であるモータ６等の温度変化によりころがり軸受３，４間の大きな熱膨張を逃がし、ガタツキを防止するために用いられる。
【０００３】
また、図８と図９に示す工作機械の主軸装置も知られている（特開平１０−２２５８０２号公報）。
この主軸装置は、ハウジング１（後部部材１ａ）の内周面と可動スリーブ部材７の外周面との間に、油流入空間Ｓａと流通隙間ｇ及び油流出空間Ｓｂとを３個宛周方向に交互に形成し、油循環装置１３で作動油を油流入空間Ｓａから流通隙間ｇを通じて油流出空間Ｓｂに流すことにより、可動スリーブ部材７を作動油の圧力で中心に浮かせて支持する構造となっている。なお、他の構造は図７の主軸装置と同一であるので、同一の部材等に同一の符号を付してその説明を省略する。
【０００４】
【発明が解決しようとする課題】
図７に示す上記前者の主軸装置は、スライドボールベアリング８に、ガタツキ防止のために予圧が与えられ、また径方向の大きな熱膨張力や切削反力が働くため、可動スリーブ部材７やハウジング１の後部部材１ａにボールの圧痕が生じ、その圧痕により可動スリーブ部材７の動きが鈍くなってころがり軸受３，４が焼き付くおそれがある。
【０００５】
また、図８と図９に示す後者の静圧軸受方式の主軸装置の場合は、作動油圧力の非常に大きい油循環装置１３が必要であり、しかも加圧に伴う作動油の温度上昇を抑えるためには、大型の油循環装置１３に見合う冷却能力を持つ大型の温度制御装置１４が必要で、製造費のみならず運転費が割高になる。また、油流入空間Ｓａと流通隙間ｇ及び油流出空間Ｓｂを交互に３個（或いは４個以上）宛形成しなければならないので、内部構造が複雑になり、この点でもコスト高になる問題点がある。
【０００６】
また、図７の主軸装置からスライドボールベアリング８を省き、後部部材１ａと可動スリーブ部材７の間に小さな隙間を設定して滑り案内にした主軸装置も一般に使用されているが、隙間が切削時のビレの原因となる他、径方向の荷重や主軸の自重による摩擦力で軸の熱膨張を円滑に逃せない場合にはころがり軸受の焼付けにもつながる。
【０００７】
本発明は、重切削に耐える大きな支持剛性と負荷容量を得ることができる工作機械の主軸装置を提供することを目的とする。
本発明の他の目的は、軸受予圧の安定化を図ることができる工作機械の主軸装置を提供することである。
【０００８】
【課題を解決するための手段】
上記の少なくとも１つの目的を達成するために、請求項１記載の発明は、ハウジング内に、主軸がころがり軸受で回転自在に支持され、上記ハウジングところがり軸受との間に、可動スリーブ部材がころがり軸受の外輪に嵌着して主軸の軸方向に移動自在に嵌挿され、上記ハウジングと可動スリーブ部材との間に、主軸の軸方向に屈撓自在とされた板ばねが、環状とされて主軸を中心に配設され、その外端部をハウジングに固定するとともに、内端部を可動スリーブ部材に固定して設けられた工作機械の主軸装置において、板ばねの外端部が油圧クランプ機構によってハウジングに着脱自在とされた構成とした。
【０００９】
この手段では、板ばねは、例えば主軸が熱膨張した時に、主軸の軸方向に撓わんでハウジングに対して可動スリーブ部材を軸方向に移動させ、また、ハウジングに対する可動スリーブ部材の径方向の動きを強い剛性で阻止する。このため、主軸の熱膨張が吸収され、またハウジングに対する可動スリーブ部材の径方向のガタツキが抑止される。
板ばねの形状及び構造は任意であり、例えば、環状の１枚物、或いは矩形状の複数のばね板を環状に配した物などとすることができる。また、板ばねは１個とは限らず、２個以上設けることができる。
【００１１】
また、この手段では、熱的条件の変化等により、板ばねに歪みが生じたような場合、油圧クランプ機構を作動させてハウジングに対する板ばね外端部の固定を解くことにより、歪みを逃がす。板ばねの固定解除は、通常、主軸が回転を停止し、主軸に負荷が掛かっていない条件下で行う。
【００１２】
請求項１記載の工作機械の主軸装置において、ハウジングと可動スリーブ部材との間にスライドボールベアリングを装入することができる（請求項２）。
この場合は、可動スリーブ部材の軸方向移動を円滑にするスライドボールベアリングの小さな負荷容量を板ばねが補う。
【００１３】
請求項１記載の工作機械の主軸装置において、水平に配置されたハウジングの内周面のほぼ下半分と、これに対向する可動スリーブ部材の外周面のほぼ下半分との間に、作動油により可動スリーブ部材に浮力を付加する油圧室を、油供給孔に連絡して形成し、該油圧室上部のハウジングの内周面と可動スリーブ部材の外周面との間に、作動油の流出に抵抗をかける絞り隙間を、油排出孔に連絡して形成することができる（請求項３）。
この構成では、作動油を油供給孔から油圧室に供給すると、絞り隙間の流出抵抗によって油圧室の作動油圧力が高まり、可動スリーブ部材に浮力を作用させる。このため、ハウジングに加わる可動スリーブ部材の下方向荷重が軽減され、ハウジングと可動スリーブ部材間の軸方向の摩擦抵抗が低下する。
【００１４】
請求項１ないし３のいずれか１つに記載の工作機械の主軸装置において、可動スリーブ部材に予圧手段を付設することができる（請求項４）。
この構成では軸受予圧の安定化が図られる。
予圧手段には、ばね等を用いた定圧予圧手段や油圧等を利用した定位置予圧手段等があるが、それらを単独で使用することも、また併用することもできる。
【００１５】
【発明の実施の形態】
発明の実施の形態を添付図面を参照して説明する。
図１ないし図４は本発明に係る工作機械の主軸装置の実施の形態を示す。なお、主軸装置の基本的な構造は、図７の主軸装置と同じであるので、同一の部材等に同一の符号を付してその説明を省略する。
【００１６】
ハウジング１の後部部材１ａと可動スリーブ部材７との間には、円環状の板ばね２１，２２が主軸２を中心にして設けられている。板ばね２１，２２は、その外端部２１ａ，２２ａをハウジング１と後部部材１ａとの間、及び後部部材１ａと該後部部材１ａにボルト２３で着脱自在に一体に取り付けられたカバー部材１ｂとの間にそれぞれシム２４を介して挟まれてハウジング１に固定され、また内端部２１ｂ，２２ｂを可動スリーブ部材７と該可動スリーブ部材７にボルト２５で着脱自在に一体に取り付けられた軸受押え７ａとの間、及び可動スリーブ部材７と該可動スリーブ部材７にボルト２６で着脱自在に一体に取り付けられたばね押え７ｂとの間にそれぞれ挟まれて可動スリーブ部材７に固定されて設けられており、主軸２の軸方向に屈撓自在とされている
【００１７】
そして、板ばね２２には３個又は４個以上の透孔２２ｃ（図２では１個しか示されていない。）が環状に等間隔で形成され、各透孔２２ｃに予圧ばね９が挿通されている。シム２４は、組込み時に板ばね２１，２２が平らになるよう調整するために使用する。
【００１８】
水平状態のハウジング１の後部部材１ａの内周面のほぼ下半分と、これに対向する可動スリーブ部材７の外周面のほぼ下半分との間に、油圧室Ｏａが油供給孔１ｃに連絡して形成されるとともに、ハウジング１の後部部材１ａの内周面のほぼ上半分と、これに対向する可動スリーブ部材７の外周面のほぼ上半分との間に、排油室Ｏｂが油排出孔１ｄに連絡して形成され、また、油圧室Ｏａと排油室Ｏｂの間に、油圧室Ｏａから排油室Ｏｂに流れる作動油の流出に抵抗をかけて排油室Ｏｂと油圧室Ｏａに圧力差を生じさせる絞り隙間ｔ，ｔが形成されている。
【００１９】
また、油圧室Ｏａと絞り隙間ｔ及び排油室Ｏｂの両側部には、軸受隙間ｃが後部部材１ａと可動スリーブ部材７の全内外周面にわたって形成されている。そして、後部部材１ａにはリング状のシール部材２７が装着され、軸受隙間ｃを液密にしている。ボルト１１，２３，２５，２６はいずれも図に１個しか示されていないが、複数環状に配設されている。
【００２０】
油供給孔１ｃと油排出孔１ｄは、ハウジング１の後部部材１ａに穿設されており、油供給孔１ｃには供給管２８によってポンプ付オイルクーラ２９が接続され、また油排出孔１ｄには、流量センサ３０を有する排油管３１が接続されている。供給管２８は電磁流量調整弁３２を持ち、供給管２８の分岐管３３には電磁リリーフ弁３４が設けられている。ポンプ付オイルクーラ２９は、油ポンプとオイルクーラとを分離した構造であっても、また場合によっては油ポンプのみであってもよい。
【００２１】
電磁流量調整弁３２は、ポンプ付オイルクーラ２９から供給管２８を通って油圧室Ｏａに供給される作動油（冷却油）の流量を調整するものである。また、電磁リリーフ弁３４は、次式（１）によって表わされる浮力Ｆが、絞り隙間ｔと軸受隙間ｃの大きさδ１，δ２の変動によって大きくなり過ぎないように作動油の供給圧力に上限を設けるために使用する。
Ｆ ≒Ｗ１ ×Ｗ２ ×（ＰＡ −ＰＢ） ……（１）
但し、
Ｗ１；油圧室Ｏａの鉛直方向の投影幅
Ｗ２；油圧室Ｏａの前後幅
ＰＡ；油圧室Ｏａの作動油圧力
ＰＢ；排油室Ｏｂの作動油圧力
【００２２】
ここで、軸受隙間ｃの大きさδ１は、後部部材１ａと可動スリーブ部材７間の温度差が最大となった場合でも支障を生じない大きさとされ、絞り隙間ｔの大きさδ２よりも小さくされている。前後幅Ｗ３を油圧室Ｏａ及び排油室Ｏｂの前後幅Ｗ２よりも小さくされた絞り隙間ｔの部分の軸受隙間ｃも絞りとして機能し、作動油の流れに抵抗をかけるが、後部部材１ａと可動スリーブ部材７間の負荷容量やそれらの嵌め合いを決定することが主体であり、作動油の流れを制御する割合は小さくされている。
【００２３】
次に、上記の構成とされた工作機械の主軸装置の作用を説明する。
リリーフ弁３４を、浮力Ｆが可動スリーブ部材７を含めた主軸２の自重ところがり軸受４に加わる支持荷重以下となるように設定してポンプ付オイルクーラ２９を作動させ、作動油を油圧室Ｏａに供給しながらモータ６で主軸２を回転させて作業を開始する。
【００２４】
ポンプ付オイルクーラ２９から油圧室Ｏａに供給された作動油は、絞り隙間ｔを通って排油室Ｏｂに流れ、後部部材１ａと可動スリーブ部材７を冷却してそれらの温度差を低下させるが、この際、絞り隙間ｔの働きによって油圧室Ｏａと排油室Ｏｂの間に圧力差が生じ、可動スリーブ部材７に浮力Ｆが作用するので、後部部材１ａに対する可動スリーブ部材７の軸方向の摩擦抵抗が小さくなる。
また、板ばね２１，２２は、可動スリーブ部材７を、その径方向の変位を強い剛性で阻止するとともに、可動スリーブ部材７の軸方向の移動を屈撓性により自由にしてハウジング１に支持している。
【００２５】
したがって、モータ６の発熱等によって主軸２が熱膨張した場合、可動スリーブ部材７は主軸２と一緒に軸方向に円滑に移動して熱膨張に起因する支障を防ぐ。また、可動スリーブ部材７が上記のように軸方向に円滑に移動するので、予圧ばね９によって主軸軸受であるころがり軸受３，４に設計通りの適正な予圧が付加される。
【００２６】
上記において、可動スリーブ部材７の熱膨張が大きくて軸受隙間ｃ（δ１）が無くなり、可動スリーブ部材７の外周面が後部部材１ａの内周面に接触した場合には、作動油の流量が減少する。この油量減少を流量センサ３０で検知して警報を出し、モータ６を停止させるような措置がとられる。
【００２７】
また、作動油の温度が下がり、過冷却になると、ころがり軸受４の外輪側が冷やされて従来構造では予圧上昇・変動につながるが、本主軸装置においては、温度低下により作動油の絶対粘度μが大きくなることから、絞り隙間ｔ（δ２）で作動油流量Ｑが下式（２）により絞られるため、過冷却が自動的に防止される。
Ｑ＝δ２^３・Ｗ３・（ＰＡ −ＰＢ）／（１２μ・Ｌ） ……（２）
但し、
Ｌ；絞り隙間ｔの長さ
【００２８】
図５は本発明の第２の実施の形態を示す。
この工作機械の主軸装置は、板ばね２１，２２の外端部２１ａ，２２ａを、シリンダＣｙａ，Ｃｙｂに装入されたピストンＰｉａ，Ｐｉｂによってハウジング１側に着脱自在に固定する構造となっている。シリンダＣｙａはハウジング１と後部部材１ａに形成され、他のシリンダＣｙｂは後部部材１ａとカバー部材１ｂに形成されている。シリンダＣｙａとピストンＰｉａ、及びシリンダＣｙｂとピストンＰｉｂはそれぞれ油圧クランプ機構を構成している。シリンダＣｙａ，Ｃｙｂはそれぞれ油通路１ｅ，１ｆを介して油供給源（図示せず）に連絡されている。
他の構造は、図１ないし図４の工作機械の主軸装置と同じである。
【００２９】
この主軸装置においては、熱的な条件の変化により板ばね２１，２２に歪みが生じたような場合、板ばね２１，２２の外端部２１ａ，２２ａのピストンＰｉａ，Ｐｉｂによる固定を解き、再びピストンＰｉａ，Ｐｉｂで固定し直すことにより、歪みを除去する。油圧クランプ機構による固定解除の外部指令は、主軸回転が停止し、主軸２に負荷が掛っていない条件下で行う。
【００３０】
図６は、本発明の第３の実施の形態を示す。
この主軸装置は、図１ないし図４の主軸装置から、油圧室Ｏａと排油室Ｏｂ及び絞り隙間ｔ並びに供給管２８等を省き、後部部材１ａと可動スリーブ部材７の隙間Ｏｃにスライドボールベアリング８を装入した構造となっている。
もちろん、スライドボールベアリング８が装入された隙間Ｏｃに冷却油を循環させ可動スリーブ部材７の熱膨張でスライドボールベアリング８の予圧を増大させない方法を取ることにより、主軸軸受の冷却を行うことが好ましいことは言うまでもない。
他の構造は図１ないし図４の主軸装置と同一である。
【００３１】
この主軸装置の場合は、単独では小さいスライドボールベアリング８の負荷容量を、剛性と負荷容量の大きい板ばね２１，２２が補う。
したがって、この主軸装置においては、第１及び第２実施形態の主軸装置に準じた効果が得られる上、既存の工作機械の主軸装置を改良することが比較的容易になる。
【００３２】
なお、後部部材１ａの線膨張係数を可動スリーブ部材７の線膨張係数よりも大きくすることが好ましい。例を上げると、可動スリーブ部材７を鋼材とした場合に、後部部材１ａを鋼材よりも線膨張係数の大きいアルミ材や黄銅などにする。ところで、発熱はころがり軸受４から起こって可動スリーブ部材７に伝わるため、温度は可動スリーブ部材７の方が後部部材１ａよりも常に高くなる。したがって、例えば、後部部材１ａと可動スリーブ部材７とが同材質の場合、温度上昇に伴い軸受隙間δ１が小さくなるので、軸受隙間δ１を大きく取らざるを得ないのが現状であるが、上記のように構成すると、後部部材１ａよりも発熱源であるころがり軸受４に近い可動スリーブ部材７の温度が上昇する方向で温度差がついても、軸受隙間δ１の減少が軽減されるので、予め軸受隙間δ１を小さく設定できる。
アルミ材は、鋼材に比べて表面の硬度不足や強度面（ヤング率、耐力、引張強さ）が劣るが、作動油による半浮上によって接触面圧を下げ摩耗や変形を防ぐことができる。
【００３３】
軸受隙間δ１は、後部部材１ａと可動スリーブ部材７が使用温度範囲の最低の同一温度となった条件下でゼロとならないように設定する。これによって、使用温度範囲で両者が同一温度なら線膨張係数の差から必ず軸受隙間を確保できる。
ころがり軸受４の発熱で内側の可動スリーブ部材７が膨張し、軸受隙間δ１が小さくなると、作動油流量が減少してその温度が高くなる。この熱は線膨張係数の大きい後部部材１ａに伝わり内径が大きくなることで軸受隙間δ１が増加する。両部品が接触した場合、熱が更に伝わりやすくなり隙間増加方向に移行することになる。
【００３４】
後部部材１ａに温度センサを設置することで設定温度範囲外になったら注意を促す方法がとれ、流量センサの信号から実際に警報を発振するか否かを判定することができる。
【００３５】
予圧には、ばね、油圧、空圧を用いた定圧予圧と油圧シリンダ等を用いた予圧切換装置により定位置予圧を取る方法が一般に使用されているが、本主軸装置においては、予圧ばね９の他に、定位置予圧を可能にする油圧シリンダを設けることができることは勿論、定位置予圧のみとすることも、場合によっては予圧の全くない主軸装置に適用することも可能である。また、予圧構造は、図のものに限らず任意である。
【００３６】
また、図の主軸装置は、モータ６がハウジング１内に設けられたモータ内蔵型となっているが、モータ内蔵型でない主軸装置に適用することもできる。また、図６の主軸装置からスライドボールベアリング８を省くことができる。油圧室Ｏａを２個以上としたり、絞り隙間ｔを油排出孔１ｄに直接連絡して排油室Ｏｂを無くすることも可能である。
【００３７】
【発明の効果】
以上説明したように、請求項１記載の発明によれば、重切削に耐える大きな支持剛性と負荷容量を得ることができる。したがって熱的変化の影響を極力抑えて主軸を低速域から高速域にわたってガタツキなく円滑に回転させ、加工等を精度よく行うことができる。
【００３９】
また、組立構造が簡単になり、コストを低減することができる。熱的条件の変化等によって板ばねに歪みが発生してもこれを簡単に除去することができ、いつも正常な状態に保つことができる。
【００４０】
請求項１記載の工作機械の主軸装置において、ハウジングと可動スリーブ部材との間にスライドボールベアリングを装入した場合、請求項１記載の工作機械の主軸装置において、水平に配置されたハウジングの内周面のほぼ下半分と、これに対向する可動スリーブ部材の外周面のほぼ下半分との間に、作動油により可動スリーブ部材に浮力を付加する油圧室を、油供給孔に連絡して形成し、該油圧室上部のハウジングの内周面と可動スリーブ部材の外周面との間に、作動油の流出に抵抗をかける絞り隙間を、油排出孔に連絡して形成した場合は、いずれも可動スリーブ部材の軸方向の摩擦抵抗が低下し、それだけ可動スリーブ部材が軸方向に円滑に移動するようになる。
【００４１】
請求項１ないし３のいずれか１つに記載の工作機械の主軸装置において、可動スリーブ部材に予圧手段を付設した構成では、軸受予圧の安定化が図られ、主軸の回転が一層円滑になる。
【図面の簡単な説明】
【図１】本発明に係る工作機械の主軸装置の実施の形態を示す垂直断面図である。
【図２】図１の主軸装置の水平断面図である。
【図３】油圧室と絞り隙間及び排油室の関係を示す図である。
【図４】油圧室と絞り隙間等の関係を示す断面図である。
【図５】本発明の第２の実施の形態を示す断面図である。
【図６】本発明の第３の実施の形態を示す断面図である。
【図７】従来の工作機械の主軸装置の断面図である。
【図８】従来の他の主軸装置の断面図である。
【図９】図８の主軸装置の（ＩＸ−ＩＸ）部分の断面図である。
【符号の説明】
１ハウジング１ａ後部部材（リヤハウジング）
２主軸４ころがり軸受
７可動スリーブ部材８スライドボールベアリング
９予圧ばね（予圧手段）２１，２２板ばね
２１ａ，２２ａ外端部２１ｂ，２２ｂ内端部
Ｃｙａ，ＣｙｂシリンダＰｉａ，Ｐｉｂピストン
Ｏａ油圧室Ｏｂ排油室
Ｏｃ隙間ｔ絞り隙間
ｃ軸受隙間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spindle device of a machine tool in which a spindle is rotatably supported by a housing via a rolling bearing such as an angular ball bearing.
[0002]
[Prior art]
As a spindle device of a machine tool, the one shown in FIG. 7 is known.
In the main shaft device, a main shaft 2 is rotatably supported by two sets of front and rear rolling bearings 3 and 4 (the left side in FIG. 7 is the front) in a housing 1, and an electric motor 6 that rotates the main shaft 2 is provided. The movable sleeve member 7 is provided between the rolling bearings 3 and 4, and is fitted between the housing 1 and the rolling roller bearing 4 on the rear side to the outer ring of the rolling bearing 4, and the slide ball bearing 8. Thus, the main shaft 2 is movably inserted in the axial direction, and the preload spring 9 is urged rearward to apply preload to the rolling bearing.
The housing 1 has a rear member (rear housing) 1a that is detachably fixed integrally with a bolt 11 at the rear end, and the movable sleeve member 7 is fitted into the rear member 1a. The slide ball bearing 8 is used to release large thermal expansion between the rolling bearings 3 and 4 due to a temperature change of the motor 6 or the like that is a heating element, and to prevent rattling.
[0003]
A spindle device for a machine tool shown in FIGS. 8 and 9 is also known (Japanese Patent Laid-Open No. 10-225802).
This spindle device includes three oil inflow spaces Sa, flow gaps g, and oil outflow spaces Sb in the circumferential direction between the inner peripheral surface of the housing 1 (rear member 1a) and the outer peripheral surface of the movable sleeve member 7. The movable sleeve member 7 is floated and supported at the center by the pressure of the hydraulic oil by alternately forming and flowing the hydraulic oil from the oil inlet space Sa to the oil outlet space Sb through the circulation gap g by the oil circulation device 13. ing. Since the other structure is the same as that of the spindle apparatus of FIG. 7, the same reference numerals are assigned to the same members and the description thereof is omitted.
[0004]
[Problems to be solved by the invention]
In the former main spindle device shown in FIG. 7, a preload is applied to the slide ball bearing 8 in order to prevent rattling, and a large thermal expansion force and cutting reaction force in the radial direction act, so that the movable sleeve member 7 and the housing 1 A ball impression is generated on the rear member 1a, and the movement of the movable sleeve member 7 becomes dull due to the impression, and the rolling bearings 3 and 4 may be seized.
[0005]
Further, in the case of the latter hydrostatic bearing type spindle device shown in FIGS. 8 and 9, an oil circulation device 13 having a very high hydraulic oil pressure is required, and the temperature rise of hydraulic oil accompanying pressurization is suppressed. For this purpose, a large temperature control device 14 having a cooling capacity commensurate with the large oil circulation device 13 is required, and not only the manufacturing cost but also the operation cost is expensive. In addition, since the oil inflow space Sa, the flow gap g, and the oil outflow space Sb must be alternately formed for three (or four or more), the internal structure becomes complicated, which also increases the cost. There is.
[0006]
In addition, a spindle device in which the slide ball bearing 8 is omitted from the spindle device of FIG. 7 and a small gap is set between the rear member 1a and the movable sleeve member 7 to provide a sliding guide is generally used. In addition to the cause of cracking, rolling bearings can be seized when the thermal expansion of the shaft cannot be smoothly released due to the radial load or the frictional force due to the weight of the main shaft.
[0007]
An object of the present invention is to provide a spindle device of a machine tool capable of obtaining a large support rigidity and load capacity that can withstand heavy cutting.
Another object of the present invention is to provide a spindle device for a machine tool capable of stabilizing the bearing preload.
[0008]
[Means for Solving the Problems]
In order to achieve the above at least one object, an invention according to claim 1, in a housing, the main shaft is rotatably supported by a rolling bearing, between the bearing rolling the upper Symbol housing, the movable sleeve member inserted by fitting the rolling bearing outer ring fitted movably in the axial direction of the main shaft, between the housing and the movable sleeve member, a leaf spring which is freely flexed in the axial direction of the main axis, is an annular In the spindle device of a machine tool provided with the outer end fixed to the housing and the inner end fixed to the movable sleeve member, the outer end of the leaf spring is a hydraulic clamp. The mechanism is configured to be detachable from the housing .
[0009]
In this means, for example, when the main shaft is thermally expanded, the leaf spring is bent in the axial direction of the main shaft to move the movable sleeve member in the axial direction relative to the housing, and the radial movement of the movable sleeve member relative to the housing is performed. Is prevented with strong rigidity. For this reason, thermal expansion of the main shaft is absorbed, and rattling of the movable sleeve member with respect to the housing in the radial direction is suppressed.
The shape and structure of the leaf springs are arbitrary. For example, the leaf spring may be a single annular member or a plurality of rectangular spring plates arranged annularly. Further, the number of leaf springs is not limited to one, and two or more leaf springs can be provided.
[0011]
Also, with this means , when the leaf spring is distorted due to a change in thermal conditions, the strain is released by operating the hydraulic clamp mechanism to unlock the outer end of the leaf spring from the housing. The release of the leaf spring is normally performed under the condition that the main shaft stops rotating and no load is applied to the main shaft.
[0012]
In the main spindle device of a machine tool according to claim 1 Symbol placement can be loaded slide ball bearings between the housing and the movable sleeve member (claim 2).
In this case, the leaf spring supplements the small load capacity of the slide ball bearing that facilitates the axial movement of the movable sleeve member.
[0013]
Oite the spindle equipment of a machine tool according to claim 1, between a substantially lower half of the inner peripheral surface of the housing that is arranged horizontally, approximately the lower half of the outer peripheral surface of the movable sleeve member opposed thereto, A hydraulic chamber that adds buoyancy to the movable sleeve member by the hydraulic oil is formed in communication with the oil supply hole, and the hydraulic oil is formed between the inner peripheral surface of the housing and the outer peripheral surface of the movable sleeve member. A throttle gap that resists outflow can be formed in communication with the oil discharge hole (claim 3) .
In this configuration, when hydraulic oil is supplied from the oil supply hole to the hydraulic chamber, the hydraulic oil pressure in the hydraulic chamber is increased by the outflow resistance of the throttle gap, and buoyancy is applied to the movable sleeve member. For this reason, the downward load of the movable sleeve member applied to the housing is reduced, and the axial frictional resistance between the housing and the movable sleeve member is reduced.
[0014]
In the spindle device for a machine tool according to any one of claims 1 to 3 , preload means can be attached to the movable sleeve member (claim 4 ).
With this configuration, the bearing preload is stabilized.
The preloading means includes a constant pressure preloading means using a spring and the like, a fixed position preloading means using a hydraulic pressure, etc., and these can be used alone or in combination.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the accompanying drawings.
1 to 4 show an embodiment of a spindle device of a machine tool according to the present invention. Since the basic structure of the spindle device is the same as that of the spindle device of FIG. 7, the same reference numerals are assigned to the same members and the description thereof is omitted.
[0016]
Between the rear member 1 a of the housing 1 and the movable sleeve member 7, annular leaf springs 21 and 22 are provided around the main shaft 2. The leaf springs 21 and 22 have outer end portions 21a and 22a between the housing 1 and the rear member 1a, and a rear member 1a and a cover member 1b that is detachably attached to the rear member 1a with bolts 23 integrally. The bearing retainer is fixed to the housing 1 with the shim 24 interposed therebetween, and the inner ends 21b and 22b are detachably and integrally attached to the movable sleeve member 7 and the movable sleeve member 7 with bolts 25. 7a and between the movable sleeve member 7 and a spring retainer 7b which is integrally attached to the movable sleeve member 7 with a bolt 26 so as to be detachable, and is fixed to the movable sleeve member 7. The main shaft 2 can be bent in the axial direction.
The leaf spring 22 is formed with three or four or more through holes 22c (only one is shown in FIG. 2) in an annular shape at equal intervals, and the preload spring 9 is inserted into each through hole 22c. ing. The shim 24 is used to adjust the leaf springs 21 and 22 to be flat when assembled.
[0018]
The hydraulic chamber Oa communicates with the oil supply hole 1c between the substantially lower half of the inner peripheral surface of the rear member 1a of the horizontal housing 1 and the substantially lower half of the outer peripheral surface of the movable sleeve member 7 opposed thereto. The oil discharge chamber Ob is formed between the substantially upper half of the inner peripheral surface of the rear member 1a of the housing 1 and the substantially upper half of the outer peripheral surface of the movable sleeve member 7 facing the oil discharge hole. 1d, and between the hydraulic chamber Oa and the oil discharge chamber Ob, resists the outflow of the hydraulic oil flowing from the oil pressure chamber Oa to the oil discharge chamber Ob, so that the oil discharge chamber Ob and the oil pressure chamber Oa Throttle gaps t and t that cause a pressure difference are formed.
[0019]
Further, bearing gaps c are formed over the entire inner and outer peripheral surfaces of the rear member 1a and the movable sleeve member 7 on both sides of the hydraulic chamber Oa, the throttle gap t, and the oil discharge chamber Ob. A ring-shaped seal member 27 is attached to the rear member 1a to make the bearing gap c liquid-tight. Although only one bolt 11, 23, 25, 26 is shown in the figure, a plurality of bolts are arranged in a ring shape.
[0020]
An oil supply hole 1c and an oil discharge hole 1d are formed in the rear member 1a of the housing 1. An oil cooler 29 with a pump is connected to the oil supply hole 1c by a supply pipe 28, and the oil discharge hole 1d is also connected to the oil discharge hole 1d. An oil drain pipe 31 having a flow sensor 30 is connected. The supply pipe 28 has an electromagnetic flow rate adjustment valve 32, and a branch pipe 33 of the supply pipe 28 is provided with an electromagnetic relief valve 34. The oil cooler with pump 29 may have a structure in which the oil pump and the oil cooler are separated, or may be only an oil pump depending on the case.
[0021]
The electromagnetic flow rate adjusting valve 32 adjusts the flow rate of the working oil (cooling oil) supplied from the oil cooler 29 with pump through the supply pipe 28 to the hydraulic chamber Oa. Further, the electromagnetic relief valve 34 limits the supply pressure of hydraulic oil so that the buoyancy F expressed by the following equation (1) does not become too large due to fluctuations in the sizes δ1 and δ2 of the throttle clearance t and the bearing clearance c. Used to provide.
F ≒ W1 x W2 x (PA-PB) (1)
However,
W1; vertical projection width W2 of the hydraulic chamber Oa; front-rear width PA of the hydraulic chamber Oa; hydraulic oil pressure PB of the hydraulic chamber Oa; hydraulic oil pressure of the oil discharge chamber Ob
Here, the size δ1 of the bearing gap c is set to a size that does not cause a problem even when the temperature difference between the rear member 1a and the movable sleeve member 7 becomes maximum, and is smaller than the size δ2 of the aperture gap t. ing. The bearing gap c in the portion of the throttle gap t in which the front-rear width W3 is made smaller than the front-rear width W2 of the hydraulic chamber Oa and the oil discharge chamber Ob also functions as a throttle and resists the flow of hydraulic oil. Mainly, the load capacity between the movable sleeve members 7 and their fitting are determined, and the ratio of controlling the flow of hydraulic oil is reduced.
[0023]
Next, the operation of the spindle device of the machine tool configured as described above will be described.
The relief valve 34 is set so that the buoyancy F is equal to or less than the supporting load applied to the own weight rolling bearing 4 of the main shaft 2 including the movable sleeve member 7 to operate the oil cooler 29 with a pump, and the hydraulic oil is supplied to the hydraulic chamber Oa. The main shaft 2 is rotated by the motor 6 while being supplied to the motor.
[0024]
The hydraulic oil supplied from the oil cooler 29 with pump to the hydraulic chamber Oa flows into the oil discharge chamber Ob through the throttle gap t, and cools the rear member 1a and the movable sleeve member 7 to reduce the temperature difference therebetween. At this time, a pressure difference is generated between the hydraulic chamber Oa and the oil discharge chamber Ob by the action of the throttle gap t, and the buoyancy F acts on the movable sleeve member 7, so that the axial direction of the movable sleeve member 7 with respect to the rear member 1a is increased. Frictional resistance is reduced.
Further, the leaf springs 21 and 22 support the movable sleeve member 7 in the housing 1 while preventing displacement in the radial direction with strong rigidity and making the movement of the movable sleeve member 7 in the axial direction free by flexibility. ing.
[0025]
Therefore, when the main shaft 2 is thermally expanded due to heat generated by the motor 6 or the like, the movable sleeve member 7 smoothly moves in the axial direction together with the main shaft 2 to prevent troubles caused by the thermal expansion. Further, since the movable sleeve member 7 moves smoothly in the axial direction as described above, an appropriate preload as designed is applied to the rolling bearings 3 and 4 which are main shaft bearings by the preload spring 9.
[0026]
In the above, when the thermal expansion of the movable sleeve member 7 is large and the bearing gap c (δ1) is eliminated and the outer peripheral surface of the movable sleeve member 7 comes into contact with the inner peripheral surface of the rear member 1a, the flow rate of the hydraulic oil decreases. To do. Measures are taken to detect this oil reduction by the flow sensor 30 and to give an alarm and stop the motor 6.
[0027]
In addition, when the temperature of the hydraulic oil is lowered and overcooled, the outer ring side of the rolling bearing 4 is cooled, leading to an increase in preload and fluctuations in the conventional structure. Since the hydraulic oil flow rate Q is throttled by the following formula (2) at the throttle gap t (δ2), the supercooling is automatically prevented.
Q = δ2 ³ · W3 · (PA −PB) / (12 μ · L) (2)
However,
L: Length of the aperture gap t [0028]
FIG. 5 shows a second embodiment of the present invention.
The spindle device of this machine tool has a structure in which outer end portions 21a and 22a of leaf springs 21 and 22 are detachably fixed to the housing 1 side by pistons Pia and Pib inserted in cylinders Cya and Cyb. . The cylinder Cya is formed on the housing 1 and the rear member 1a, and the other cylinder Cyb is formed on the rear member 1a and the cover member 1b. The cylinder Cya and the piston Pia, and the cylinder Cyb and the piston Pib each constitute a hydraulic clamping mechanism. The cylinders Cya and Cyb are connected to an oil supply source (not shown) via oil passages 1e and 1f, respectively.
Other structures are the same as those of the spindle device of the machine tool shown in FIGS.
[0029]
In this spindle device, when the leaf springs 21 and 22 are distorted due to a change in thermal conditions, the outer ends 21a and 22a of the leaf springs 21 and 22 are unfixed by the pistons Pia and Pib, and again. The distortion is removed by re-fixing with the pistons Pia and Pib. The external command for releasing the fixing by the hydraulic clamp mechanism is performed under the condition that the spindle rotation is stopped and no load is applied to the spindle 2.
[0030]
FIG. 6 shows a third embodiment of the present invention.
The main spindle apparatus omits the hydraulic chamber Oa, the oil discharge chamber Ob, the throttle gap t, the supply pipe 28, and the like from the main spindle apparatus shown in FIGS. 1 to 4, and slide ball bearings in the gap Oc between the rear member 1a and the movable sleeve member 7. 8 is inserted.
Of course, the spindle bearing can be cooled by circulating the cooling oil through the clearance Oc in which the slide ball bearing 8 is inserted and preventing the thermal expansion of the movable sleeve member 7 from increasing the preload of the slide ball bearing 8. Needless to say, it is preferable.
Other structures are the same as those of the spindle device shown in FIGS.
[0031]
In the case of this spindle device, the leaf springs 21 and 22 having large rigidity and load capacity supplement the load capacity of the slide ball bearing 8 which is small by itself.
Therefore, in this spindle device, an effect according to the spindle device of the first and second embodiments can be obtained, and it is relatively easy to improve the spindle device of an existing machine tool.
[0032]
The linear expansion coefficient of the rear member 1a is preferably larger than the linear expansion coefficient of the movable sleeve member 7. For example, when the movable sleeve member 7 is made of steel, the rear member 1a is made of aluminum or brass having a larger linear expansion coefficient than steel. By the way, since heat is generated from the rolling bearing 4 and transmitted to the movable sleeve member 7, the temperature of the movable sleeve member 7 is always higher than that of the rear member 1a. Therefore, for example, when the rear member 1a and the movable sleeve member 7 are made of the same material, the bearing gap δ1 becomes smaller as the temperature rises. With this configuration, even if there is a temperature difference in the direction in which the temperature of the movable sleeve member 7 that is closer to the rolling bearing 4 that is the heat generation source than the rear member 1a rises, the reduction in the bearing gap δ1 is reduced. δ1 can be set small.
Aluminum materials have poor surface hardness and inferior strength (Young's modulus, proof stress, tensile strength) compared to steel materials, but they can reduce contact surface pressure and prevent wear and deformation by semi-floating with hydraulic oil.
[0033]
The bearing clearance δ1 is set so that it does not become zero under the condition that the rear member 1a and the movable sleeve member 7 are at the same minimum temperature in the operating temperature range. As a result, if the temperature is the same in the operating temperature range, a bearing clearance can always be secured from the difference in linear expansion coefficient.
When the inner movable sleeve member 7 expands due to the heat generated by the rolling bearing 4 and the bearing gap δ1 becomes smaller, the flow rate of the hydraulic oil decreases and the temperature rises. This heat is transmitted to the rear member 1a having a large coefficient of linear expansion, and the inner diameter increases, thereby increasing the bearing clearance δ1. When both parts come into contact with each other, heat is more easily transferred and the gap is shifted in the increasing direction.
[0034]
When a temperature sensor is installed on the rear member 1a, a method of calling attention is taken when the temperature falls outside the set temperature range, and it can be determined whether or not an alarm is actually oscillated from the signal of the flow sensor.
[0035]
As the preload, a constant pressure preload using a spring, hydraulic pressure, pneumatic pressure, and a preload switching device using a hydraulic cylinder or the like are generally used. However, in the main spindle device, the preload spring 9 includes In addition, it is possible to provide a hydraulic cylinder that enables a fixed position preload, as well as a fixed position preload only, or in some cases, it can be applied to a spindle device having no preload. Further, the preload structure is not limited to that shown in the figure, and is arbitrary.
[0036]
Moreover, although the spindle apparatus of the figure is a motor built-in type in which the motor 6 is provided in the housing 1, it can be applied to a spindle apparatus that is not a motor built-in type. Further, the slide ball bearing 8 can be omitted from the spindle device of FIG. It is possible to eliminate the oil discharge chamber Ob by providing two or more hydraulic chambers Oa or by directly connecting the throttle gap t to the oil discharge hole 1d.
[0037]
【The invention's effect】
As described above, according to the first aspect of the invention, it is possible to obtain a large support rigidity and load capacity that can withstand heavy cutting. Therefore, the influence of the thermal change can be suppressed as much as possible, and the spindle can be smoothly rotated without rattling from the low speed range to the high speed range, so that the machining can be performed with high accuracy.
[0039]
Further, the assembly structure is simplified and the cost can be reduced. Even if the leaf spring is distorted due to a change in the thermal condition, it can be easily removed and always kept in a normal state.
[0040]
The spindle device of machine tool according to claim 1, wherein, when charged with slide ball bearings between the housing and the movable sleeve member, Oite the spindle equipment of a machine tool according to claim 1, which is disposed horizontally A hydraulic chamber that adds buoyancy to the movable sleeve member by hydraulic oil is connected to the oil supply hole between the lower half of the inner peripheral surface of the housing and the lower half of the outer peripheral surface of the movable sleeve member facing the housing. When a throttle gap is formed between the inner peripheral surface of the housing above the hydraulic chamber and the outer peripheral surface of the movable sleeve member in contact with the oil discharge hole to resist outflow of hydraulic oil. In either case, the frictional resistance in the axial direction of the movable sleeve member decreases, and the movable sleeve member moves smoothly in the axial direction accordingly.
[0041]
In the main spindle device for a machine tool according to any one of claims 1 to 3 , the preload means is attached to the movable sleeve member, the bearing preload is stabilized, and the rotation of the main spindle becomes smoother.
[Brief description of the drawings]
FIG. 1 is a vertical sectional view showing an embodiment of a spindle device of a machine tool according to the present invention.
FIG. 2 is a horizontal sectional view of the spindle device of FIG. 1;
FIG. 3 is a diagram illustrating a relationship between a hydraulic chamber, a throttle gap, and an oil discharge chamber.
FIG. 4 is a cross-sectional view showing a relationship between a hydraulic chamber and a throttle gap.
FIG. 5 is a cross-sectional view showing a second embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a third embodiment of the present invention.
FIG. 7 is a sectional view of a spindle device of a conventional machine tool.
FIG. 8 is a cross-sectional view of another conventional spindle device.
9 is a cross-sectional view of the (IX-IX) portion of the spindle device of FIG. 8. FIG.
[Explanation of symbols]
1 Housing 1a Rear member (rear housing)
2 Spindle 4 Rolling bearing 7 Movable sleeve member 8 Slide ball bearing 9 Preload spring (preload means) 21, 22 Leaf spring 21a, 22a Outer end 21b, 22b Inner end Cya, Cyb Cylinder Pia, Pib Piston Oa Hydraulic chamber Ob Exhaust Oil chamber Oc clearance t Throttle clearance c Bearing clearance

Claims

A main shaft is rotatably supported by a rolling bearing in the housing, and a movable sleeve member is fitted to the outer ring of the rolling bearing so as to be movable in the axial direction of the main shaft between the housing and the rolling bearing. A leaf spring, which is bendable in the axial direction of the main shaft, is disposed between the housing and the movable sleeve member in an annular shape around the main shaft, and its outer end is fixed to the housing. In the spindle device of the machine tool provided with the end fixed to the movable sleeve member,
A spindle device for a machine tool, wherein an outer end portion of a leaf spring is detachably attached to a housing by a hydraulic clamp mechanism.

2. The spindle device for a machine tool according to claim 1, wherein a slide ball bearing is inserted between the housing and the movable sleeve member.

A hydraulic chamber for adding buoyancy to the movable sleeve member with hydraulic fluid between a substantially lower half of the inner peripheral surface of the horizontally disposed housing and a substantially lower half of the outer peripheral surface of the movable sleeve member facing the housing, Formed in communication with the oil supply hole,
A throttle gap that resists the outflow of hydraulic fluid is formed between the inner peripheral surface of the upper housing of the hydraulic chamber and the outer peripheral surface of the movable sleeve member so as to communicate with the oil discharge hole. Item 1. A spindle device for a machine tool according to Item 1.

The spindle device of machine tool according to any one of claims 1, characterized in that the preloading means movable sleeve member annexed 3.