JP4471531B2

JP4471531B2 - Material gripping device and automatic lathe

Info

Publication number: JP4471531B2
Application number: JP2001146834A
Authority: JP
Inventors: 武岡部; 修鷲峰; 邦彦小久保
Original assignee: Citizen Holdings Co Ltd; Citizen Watch Co Ltd
Current assignee: Citizen Holdings Co Ltd; Citizen Watch Co Ltd
Priority date: 2001-05-16
Filing date: 2001-05-16
Publication date: 2010-06-02
Anticipated expiration: 2021-05-16
Also published as: JP2002337082A

Description

【０００１】
【発明の属する技術分野】
本発明は、工作機械に装備できる素材把持装置に関する。さらに本発明は、素材把持装置を備えた自動旋盤に関する。
【０００２】
【従来の技術】
工作機械において、加工工程中に被加工素材を固定的に保持するために、開閉動作可能な把持部を有するチャックと、チャックの把持部を開閉動作させる作動機構と、作動機構を駆動する駆動部とを有する素材把持装置を装備したものは知られている。例えば、ＮＣ旋盤等の自動旋削加工を実施可能な工作機械（本明細書で自動旋盤と総称する）では、中空の筒状本体に弾性変形可能なすり割り構造の把持部を形成してなるチャック（一般にコレットチャックと称する）を、中空の主軸の内部先端領域に同心状に設置するとともに、チャックの把持部を弾性変形させるように作動する作動機構を主軸に併設して備える素材把持装置が周知である。この構成によれば、主軸の後方から主軸内部に軸線方向へ送給される棒状の被加工素材が、作動機構の作動によりチャックを介して主軸に固定的に保持される。
【０００３】
従来、この種の素材把持装置では、駆動部として一般に、油圧又は空気シリンダ装置や回転電動機が採用されている。例えば自動旋盤の主軸に組み込まれる素材把持装置においては、作動機構が、主軸の軸線方向に移動可能な作動部材を備えて構成されるとともに、駆動部であるシリンダ装置の直動出力又は電動機の回転出力が、レバー組立体、送りねじ装置等の動力伝達機構を介して作動部材に伝達される構成が一般的である（例えば特開平７−３２８８１９号公報参照）。この構成では、駆動部の駆動により作動部材が主軸に沿って軸線方向へ移動し、それにより、チャックの把持部がその内径寸法を縮小する（すなわち縮径する）ように弾性変形して被加工素材を把持する。
【０００４】
【発明が解決しようとする課題】
上記した従来の素材把持装置において、駆動部としてシリンダ装置を採用した場合は、素材把持装置の全体寸法を削減することが困難であるだけでなく、被加工素材の外径寸法や剛性の変化に即時対応してチャックの把持力を自動調整することが困難である課題を有する。また、シリンダ装置自体に生じ得る圧力損失により、チャックの作動効率が低くなる傾向がある。
【０００５】
他方、駆動部として回転電動機（通常はサーボモータ）を採用した場合は、電動機出力軸の回転制御により、チャックの把持力を比較的容易に自動調整できる利点がある。しかし、送りねじ装置等の動力伝達機構を必然的に使用するために、素材把持装置の全体寸法を削減することはやはり困難である。しかも、送りねじ装置自体、滑りや捩れ等による伝達損失を生じ得るので、チャックの作動効率を効果的に改善することは困難である。
【０００６】
本発明の目的は、チャックを有する素材把持装置において、チャックの把持力を比較的容易に自動調整できる駆動部を備え、しかも装置の全体寸法を可及的に削減できるとともに、チャックの作動効率を著しく向上させることができる素材把持装置を提供することにある。
本発明の他の目的は、そのような素材把持装置を備えた高機能の自動旋盤を提供することにある。
【０００７】
【課題を解決するための手段】
上記目的を達成するために、請求項１に記載の発明は、中心軸線を有する筒状本体及び筒状本体に設けられる開閉動作可能な把持部を有するチャックと、チャックに対して筒状本体の軸線方向へ移動することによりチャックの把持部を開閉動作させる作動部材と、推力により作動部材を軸線方向へ移動させるリニアモータとを具備する素材把持装置において、リニアモータと作動部材との間に設置され、リニアモータの推力を増大させて作動部材に伝達する推力伝達装置を具備し、推力伝達装置は、リニアモータの可動子に連結され、リニアモータの駆動により可動子と共に軸線方向へ移動する直動部材と、直動部材に係合する第１端と作動部材に係合する第２端とを有し、直動部材の軸線方向移動に連動して支軸旋回するとともに、梃子の作用により推力を作動部材に伝達するレバー部材とを備えることを特徴とする素材把持装置を提供する。
【００１１】
請求項２に記載の発明は、請求項１に記載の素材把持装置において、直動部材は、レバー部材の第１端に摺動可能に係合する係合面を有し、係合面が、チャックの把持部に素材を把持している間に推力伝達装置を介してリニアモータに加わる負荷を軽減する負荷軽減領域を有する素材把持装置を提供する。
【００１３】
請求項３に記載の発明は、請求項１又は２に記載の素材把持装置において、作動部材は、チャックの筒状本体に共軸に配置される筒状体からなり、リニアモータは、作動部材の少なくとも一部分を囲繞するように配置される筒状の可動子を有する素材把持装置を提供する。
【００１４】
請求項４に記載の発明は、請求項１〜３のいずれか１項に記載の素材把持装置において、リニアモータの推力を制御することによりチャックの把持力を調整する推力制御機構をさらに具備する素材把持装置を提供する。
【００１５】
請求項５に記載の発明は、請求項１〜３のいずれか１項に記載の素材把持装置において、リニアモータの可動子の位置を制御することによりチャックの把持力を調整する位置制御機構をさらに具備する素材把持装置を提供する。
【００１６】
請求項６に記載の発明は、請求項１〜５のいずれか１項に記載の素材把持装置を主軸に組み込んだことを特徴とする自動旋盤を提供する。
【００１７】
【発明の実施の形態】
以下、添付図面を参照して、本発明の実施の形態を詳細に説明する。図面において、同一又は類似の構成要素には共通の参照符号を付す。
図１は、本発明の実施の形態による素材把持装置１０を、自動旋盤の主軸１２に組み込んだ状態で示す。図２及び図３はそれぞれ、主軸１２に組み込まれた素材把持装置１０の主要部を拡大して示す。素材把持装置１０は、主軸１２の軸線方向貫通穴１２ａの内側先端領域に同心状に設置されるチャック１４と、チャック１４の後述する把持部を開閉動作させて棒状の被加工素材Ｗ（図２：以下、棒材Ｗと称する）を固定的に把持させる作動機構１６と、作動機構１６を駆動する駆動部１８とを備える。
【００１８】
主軸１２は、軸受装置２０を介して自動旋盤の主軸台２２に回転可能に搭載される。図示実施形態では、主軸台２２に、主軸１２を回転駆動する回転駆動装置２４としてビルトイン型ＡＣサーボモータが内蔵されている。主軸１２は中空筒状の構造を有し、その後端から貫通穴１２ａの内部に軸線方向へ送給される棒材Ｗを所定位置でチャック１４に把持した状態で、回転駆動装置２４により回転駆動される。なお、主軸１２の回転駆動装置は、図示構成に限定されず、主軸台２２の外部に併設されるＡＣサーボモータ（図示せず）の出力軸を、ベルト／プーリ等の動力伝達機構（図示せず）を介して主軸１２に連結する構成であってもよい。
【００１９】
図２に拡大して示すように、チャック１４は、棒材Ｗを内部に受容可能な中空の筒状本体２６と、筒状本体２６の軸線方向前端（図で左端）領域に設けられる把持部２８とを備えて構成される。把持部２８は、筒状本体２６の中心軸線２６ａを基準として内径寸法を弾性的に変更可能なすり割り構造を有する。すなわち、把持部２８は、筒状本体２６の前端領域で軸線方向へ所定長さに渡って刻設された複数のスリット３０を備える。それらスリット３０は、筒状本体２６の中心軸線２６ａに関し放射状に形成されて周方向へ等間隔に配置され、隣合うスリット３０の間に、径方向へ変位可能な縦割片３２をそれぞれ形成する。各縦割片３２は、その基端を支点として、筒状本体２６の径方向へ板ばね状に弾性変形できるようになっている。
【００２０】
把持部２８に設けられた複数の縦割片３２は、弓形の曲面をそれぞれの内面に有し、それら内面が互いに協働して、把持部２８の実質的円筒状の棒材把持面３４を構成する。把持部２８は、複数の縦割片３２に一様に径方向内方への外力を加えて弾性的に撓ませ、棒材把持面３４を把持対象の棒材Ｗに密接するまで縮径することにより、棒材Ｗを強固に固定的に把持する。把持部２８への径方向圧力が解除されると、各縦割片３２が弾性的に復元して棒材把持面３４が拡径し、棒材Ｗが把持部２８から解放される。把持部２８の各縦割片３２には、その外面に、径方向内方への外力を受けるためのテーパ面３６が形成される。それらテーパ面３６は、互いに協働して、把持部２８の軸線方向前端へ向かって徐々に拡径して延びる円錐台状の圧力受け面を構成する。また、各縦割片３２のテーパ面３６は、把持部２８の前端面から軸線方向後方へ幾分離れた位置に形成され、それにより各テーパ面３６の大径端に隣接して、中心軸線２６ａに略直交して延びる肩面３８が形成される。
【００２１】
素材把持装置１０の作動機構１６は、主軸１２の貫通穴１２ａ内に軸線方向摺動可能に同心に収容される作動部材４０を備える。作動部材４０は、棒材Ｗを受容可能な長尺の中空筒状体であり、その軸線方向貫通穴４０ａの内側前端領域に、チャック１４を軸線方向摺動可能に同心に収容できる。作動部材４０の貫通穴４０ａの軸線方向前端領域には、チャック１４の把持部２８に設けた全てのテーパ面３６に係合可能な円錐台状の作用面４２が形成される。作用面４２は、作動部材４０の前端面から軸線方向後方へ徐々に縮径して延び、その小径端で、作動部材４０の円筒状内周面に接続される。作用面４２の小径端の内径寸法は、チャック１４の把持部２８のテーパ面３６が構成する圧力受け面の小径端の外径寸法に実質的に等しくなっており、それにより作用面４２は、全てのテーパ面３６に面接触式に当接される加圧面を構成する。
【００２２】
作動部材４０の円筒状内周面には、作用面４２から軸線方向後方へ所定距離だけ離れた位置に、径方向へ延びる環状の支持面４４が形成され、作用面４２と支持面４４との間の領域に、チャック１４及び弾性部材４６が軸線方向へ整列して同心状に収容される。弾性部材４６は、例えば圧縮コイルばねからなり、チャック１４の軸線方向後端面と作動部材４０の支持面４４との間に弾性的に撓んだ状態で介在して、チャック１４を作動部材４０の支持面４４から離れる方向（すなわち主軸１２の軸線方向前方）に付勢する。
【００２３】
主軸１２の先端には、チャック１４の把持部２８に設けた全ての肩面３８に係合可能な係止面４８を内側に備えるキャップ５０が、脱着可能に取り付けられる。作動部材４０の軸線方向前端領域にチャック１４及び弾性部材４６を適正に収容した状態で、キャップ５０を主軸１２の先端に取り付けると、その係止面４８がチャック１４の全肩面３８に係合し、弾性部材４６の付勢に抗してチャック１４を作動部材４０から脱落しないように保持する。なお、チャック１４を交換する際には、キャップ５０を主軸１２から取り外してチャック１４を作動部材４０から抜き取ればよい。
【００２４】
図３に拡大して示すように、作動部材４０の軸線方向後端面４０ｂは、駆動部１８からの駆動力を受ける駆動力受け面を構成する。主軸１２の軸線方向後端近傍には、主軸１２の筒状壁を貫通する複数の開口部５２が、好ましくは周方向へ等間隔に設けられ、それら開口部５２の中に、作動部材４０の軸線方向後端面４０ｂが位置するようになっている。後述するように作動部材４０は、主軸１２の貫通穴１２ａ内で駆動部１８の駆動力を受けて、主軸１２の軸線方向すなわちチャック１４の筒状本体２６（図２）の軸線方向に移動し、それによりチャック１４の把持部２８（図２）を弾性的に縮径させる。なお図示実施形態では、作動部材４０は、支持面４４（図２）の近傍及び後端面４０ｂの近傍でそれぞれ分割された３部品構造を有するが、これに限定されず、例えば全体に一体の構造を有することもできる。
【００２５】
素材把持装置１０の駆動部１８には、リニアモータ５４が装備される。リニアモータ５４は、円筒型リニアモータ（例えばリニアステップモータ）からなり、主軸１２及び作動部材４０の軸線方向後端領域を同心状に囲繞して配置される円筒状の可動子５６と、主軸台２２のハウジング５８の内面に固定的に設置され、空隙を介して可動子５６に対向する固定子６０とを備える。図示実施形態では、リニアモータ５４は、固定子６０を一次側とし、かつ可動子５６を二次側として構成されているが、その逆の構成とすることもできる。後述するようにリニアモータ５４は、その推力を作動部材４０に伝達して、作動部材４０を主軸１２の軸線方向すなわちチャック１４の筒状本体２６の軸線方向に移動させるように作用する。
【００２６】
素材把持装置１０はさらに、リニアモータ５４と作動部材４０との間に設置され、リニアモータ５４の推力を増大させて作動部材４０に伝達する推力伝達装置６２を備える。推力伝達装置６２は、リニアモータ５４の可動子５６に連結され、可動子５６と一体的に主軸１２の軸線方向へ移動可能な直動部材６４と、直動部材６４の軸線方向移動に連動して支軸旋回する複数のレバー部材６６（以下、レバー６６と略称する。）とを備えて構成される。
【００２７】
推力伝達装置６２の直動部材６４は、リニアモータ５４の可動子５６の内側に同心状に配置される筒状体であり、その内周面６４ａを、主軸１２の筒状壁の外周面１２ｂに摺動可能に接触させて、主軸１２の軸線方向後端領域で主軸１２に同心に取り付けられる。直動部材６４はさらに、それ自体の軸線方向一端で径方向外方へ突出するフランジ部分６８と、フランジ部分６８に隣接して形成され、それ自体の軸線方向他端へ向かって徐々に縮径して延びる略円錐状の外周面すなわち係合面７０とを備える。直動部材６４は、そのフランジ部分６８で、リニアモータ５４の可動子５６を直接に支持する筒状の支持部材７２に固定的に連結される。また直動部材６４は、主軸１２に適正に取り付けられた状態で、その係合面７０が、主軸１２の軸線方向後端へ向かって徐々に縮径するように配置される。
【００２８】
推力伝達装置６２の複数のレバー６６は、直動部材６４の軸線方向後方位置で、主軸１２の外周面１２ｂに沿って好ましくは周方向へ等間隔に配置される。各レバー６６は、直動部材６４に係合する第１端６６ａと、作動部材４０に係合する第２端６６ｂとを備え、第１端６６ａと第２端６６ｂとの間の中間点で、主軸１２の軸線方向後端領域に設置されたレバーホルダ７４に、支軸７６を介して回動可能に支持される。レバー６６は、第１端６６ａと支軸７６との間の距離が、第２端６６ｂと支軸７６との間の距離よりも十分に大きく、支軸７６を支点として梃子の作用を発揮できるようになっている。
【００２９】
各レバー６６は、レバーホルダ７４を介して主軸１２に適正に取り付けられた状態で、その第１端６６ａが、直動部材６４の係合面７０に摺動式に係合可能な位置に配置される。またこの状態で、各レバー６６の第２端６６ｂは、主軸１２の後端領域に形成された対応の開口部５２に受容されて、開口部５２内に位置する作動部材４０の軸線方向後端面４０ｂに摺動可能に係合する。このとき、前述したように、作動部材４０の軸線方向前端領域にチャック１４及び弾性部材４６を適正に収容した状態でキャップ５０を主軸１２の先端に取り付けると、弾性部材４６の付勢力下で、チャック１４の肩面３８がキャップ５０の係止面４８に当接され、それと同時に、弾性部材４６の反作用力下で、作動部材４０の軸線方向後端面４０ｂが各レバー６６の第２端６６ｂに当接される。それにより、各レバー６６は、その第１端６６ａが主軸１２の外周面１２ｂに接近する方向へ付勢され、またレバーホルダ７４は、複数のレバー６６を介して、主軸１２の軸線方向後端に向かって付勢される。
【００３０】
図４に示すように、レバーホルダ７４は、それ自体に設けたガイドピン７８が、主軸１２の筒状壁に設けたガイド穴８０に係合することにより、主軸１２の外周面１２ｂ上に、軸線方向へ摺動可能に設置される。レバーホルダ７４の軸線方向後方には、主軸１２の筒状壁の軸線方向後端領域に螺着される調節ナット８２が設置される。調節ナット８２は、作動部材４０及び複数のレバー６６を介してレバーホルダ７４に負荷される弾性部材４６の付勢力に抗して、レバーホルダ７４を主軸１２上の所定位置に保持する。また、このように弾性部材４６の付勢力がレバーホルダ７４に負荷されている状態で、調節ナット８２を主軸１２に締め込んだり緩めたりすることにより、主軸１２上でのレバーホルダ７４及び複数のレバー６６の軸線方向位置を調節することができる。
【００３１】
直動部材６４は、後述するようにリニアモータ５４の駆動により主軸１２の外周面１２ｂ上で軸線方向へ摺動し、それに伴い、その係合面７０上に、各レバー６６の第１端６６ａを摺動式に乗り上げさせることにより、複数のレバー６６をそれぞれの支軸７６の周りで同期して回転させる。ここで、図５（ａ）に拡大して示すように、直動部材６４の係合面７０は、その内周面６４ａ（すなわち主軸１２の外周面１２ｂ）との成す角度が段階的に増加するように、主軸１２の軸線方向後端へ向かって徐々に縮径している。図示実施形態では、係合面７０は、フランジ部分６８に最も近接して、内周面６４ａに対し略平行に延びる第１領域７０ａと、第１領域７０ａの後方に隣接して、内周面６４ａに対し約５°の角度を成して延びる第２領域７０ｂと、第２領域７０ｂの後方に隣接して、内周面６４ａに対し約１０°の角度を成して延びる第３領域７０ｃと、第３領域７０ｃの後方に隣接して、内周面６４ａに対し約２５°の角度を成して延びる第４領域７０ｄとを備えて構成される。このような構成により、直動部材６４の係合面７０は、特にその第１及び第２領域７０ａ、７０ｂが、後述するように、棒材把持中に推力伝達装置６２を介してリニアモータ５４に加わる負荷を軽減するように作用できる。
【００３２】
上記構成を有する素材把持装置１０の作動形態を、以下に説明する。
まず、駆動部１８を構成するリニアモータ５４の初期設定により作動部材４０をチャック開位置に配置し、チャック１４の把持部２８を開状態に置く。この状態で、図１及び図３に示すように、リニアモータ５４の可動子５６は、推力伝達装置６２の直動部材６４と共に、直線往復動作ストロークの前端（図で左端）位置に配置される。また、直動部材６４の係合面７０は、複数のレバー６６の第１端６６ａから軸線方向前方へ僅かに離れた位置に配置され、したがって各レバー６６の第１端６６ａは、弾性部材４６の付勢力下で主軸１２の外周面１２ｂに当接される（図５（ａ））。そして、作動部材４０の作用面４２は、チャック１４の把持部２８のテーパ面３６を実質的に加圧しない位置に置かれる（図１及び図２）。この開状態の間に、主軸１２の後端からその内部に長尺の棒材Ｗを挿入し、作動部材４０の貫通穴４０ａに通してチャック１４に送給する。
【００３３】
棒材Ｗの所要の加工長さ部分が、チャック１４の軸線方向前端面から突出した時点で、棒材Ｗの送給を停止する。そこで、リニアモータ５４を起動して、その可動子５６を直動部材６４と共に、主軸１２の軸線方向後方へ移動させる。それに伴い、レバーホルダ７４に支持された複数のレバー６６が、弾性部材４６の付勢に抗して、それらの第１端６６ａで直動部材６４の係合面７０に漸進的に乗り上げ、それにより支軸７６を中心に同期して回転する。このように複数のレバー６６が同期して回転すると、それらレバー６６は、梃子の作用下でリニアモータ５４の推力を増大して作動部材４０に伝達し、それぞれの第２端６６ｂで作動部材４０の軸線方向後端面４０ｂを押圧する。それにより作動部材４０は、弾性部材４６の付勢に抗して、主軸１２の貫通穴１２ａ内を軸線方向前方に向けて移動する。
【００３４】
その後、可動子５６及び直動部材６４が、直線往復動作ストロークの後端（図で右端）位置に到達した時点で、作動部材４０はチャック閉位置に配置され、チャック１４の把持部２８が閉状態に置かれる（図４）。この状態で、作動部材４０の作用面４２は、チャック１４の把持部２８の全テーパ面３６に押し付けられ、それにより把持部２８の全縦割片３２が一様に径方向内方へ撓んで棒材把持面３４を縮径させ、棒材Ｗを把持部２８に強固に固定的に把持する。また、このチャック閉位置で、各レバー６６の第１端６６ａは、弾性部材４６の付勢力下で、直動部材６４の係合面７０の第１領域７０ａ（図５（ｂ））又は第２領域７０ｂ（図５（ｃ））に当接される。
【００３５】
ここで、各レバー６６の第１端６６ａが直動部材６４の係合面７０の第１領域７０ａに当接されている状態（図５（ｂ））では、作動部材４０及びレバー６６を介して直動部材６６に加えられる棒材把持力の反力及び弾性部材４６の付勢力は、レバー６６の第１端６６ａを、主軸１２の外周面１２ｂに平行な係合面第１領域７０ａに押し付けるように作用するので、直動部材６４を主軸１２の軸線方向前方に付勢する分力を実質的に生じない。したがってこの状態では、リニアモータ５４に加わる負荷が実質的に零となり、結果としてリニアモータ５４の励磁を休止することができる。
【００３６】
他方、各レバー６６の第１端６６ａが直動部材６４の係合面７０の第２領域７０ｂに当接されている状態（図５（ｃ））では、作動部材４０及びレバー６６を介して直動部材６４に加えられる棒材把持力の反力及び弾性部材４６の付勢力は、レバー６６の第１端６６ａを、主軸１２の外周面１２ｂに対して傾斜する係合面第２領域７０ｂに押し付けるように作用するので、直動部材６４を軸線方向前方に付勢する分力すなわちリニアモータ５４に加わる負荷が生じる。しかし、主軸外周面１２ｂに対する第２領域７０ｂの傾斜角度が約５°と小さいので、リニアモータ５４に加わる負荷は比較的小さく、結果としてリニアモータ５４の小さな推力で、チャック１４を閉状態に保持できる。このように、直動部材６４の係合面７０の第１及び第２領域７０ａ、７０ｂは、チャック１４の把持部２８に棒材Ｗを把持している間に推力伝達装置６２を介してリニアモータ５４に加わる負荷を軽減する負荷軽減領域として機能する。
【００３７】
上記した閉状態から、リニアモータ５４を起動して、その可動子５６を直動部材６４と共に主軸１２の軸線方向前方へ移動させると、複数のレバー６６が、弾性部材４６の付勢力下で、それらの第１端６６ａを直動部材６４の係合面７０に沿って摺動させ、それにより、第１端６６ａを主軸外周面１２ｂに接近させる方向へ、支軸７６を中心に同期して回転する。それに伴い、作動部材４０は、弾性部材４６の付勢力により、主軸１２の貫通穴１２ａ内を軸線方向後方に向けて移動する。その結果、作動部材４０の作用面４２がチャック１４の把持部２８の全テーパ面３６に加えていた圧力が解除されて、把持部２８の棒材把持面３４が拡径し、棒材Ｗがチャック１４から解放される。
【００３８】
このように、上記構成を有する素材把持装置１０によれば、作動機構１６の作動部材４０を駆動する駆動部１８にリニアモータ５４を装備したので、駆動部としてシリンダ装置を採用した従来の素材把持装置の構成に比べ、素材把持装置１０の全体寸法を削減することが容易であるとともに、シリンダ装置の圧力損失の除外により、チャック１４の作動効率を著しく向上させることができる。しかも、リニアモータ５４の出力軸（図示実施形態では支持部材７２）の直動制御（後述する）により、棒材Ｗの外径寸法や剛性の変化に即時対応して、チャック１４の把持力を比較的容易に自動調整できる利点がある。また、駆動部として回転電動機を採用した従来の素材把持装置に比べても、送りねじ装置の排除により動力伝達機構を簡略化できるので、素材把持装置１０の全体寸法を削減することが容易であるとともに、送りねじ装置の伝達損失の除外により、チャックの作動効率を効果的に改善することができる。したがって、素材把持装置１０を主軸１２に組み込んだ自動旋盤においては、小型化及び高機能化が促進される。
【００３９】
特に、素材把持装置１０では、円筒型のリニアモータ５４を採用したので、固定子６０に対する可動子５６の回転方向の位置合わせを考慮する必要がない。したがって、主軸１２に摺動可能に接触する直動部材６４に連結されている可動子５６は、主軸１２と共に回転することができ、可動子５６と直動部材６４との間に軸受を介在させる必要がなくなるので、装置の小型化及び構造の簡略化がさらに促進される。また、円筒型リニアモータ５４自体の特性として、磁気吸引力が相殺されて推力に影響を及ぼさないので、主軸回転中の磁気吸引力に起因する偏心を確実に防止できる利点がある。
【００４０】
上記した素材把持装置１０は、チャック１４の把持力を自動調整するための一手段として、リニアモータ５４の推力を制御することにより出力軸の直動制御を実施する推力制御機構８４をさらに備えることができる。素材把持装置１０では、駆動部１８に装備したリニアモータ５４の推力が、推力伝達装置６２及び作動機構１６を介してチャック１４に伝達されてチャック１４の把持力に変換されるので、チャック１４の把持力はリニアモータ５４の推力に比例することになる。
【００４１】
図６に示すように、推力制御機構８４は、リニアモータ５４の動作中の実際の推力を測定する推力測定部８６と、要求される把持力を生成するためのリニアモータ５４の推力目標値を予め設定する推力設定部８８と、推力設定部８８によって設定された推力目標値を記憶する推力記憶部９０と、推力測定部８６で測定した実際の推力が推力記憶部９０に記憶した推力目標値に達したか否かを判定する判定部９２と、チャック開位置における直動部材６４の位置（図５（ａ））を記憶する開位置記憶部９４と、推力測定部８６、判定部９２及び閉位置記憶部９４から受け取った情報を演算処理してリニアモータ５４の動作を制御する制御部９６と、制御部９６での処理結果等を表示する表示部９８とを備えて構成される。
【００４２】
制御部９６は、例えば自動旋盤に搭載される数値制御（ＮＣ）装置のＣＰＵから構成でき、同ＮＣ装置の記憶部に予め記憶した図７に示すタイミングチャートに従って、リニアモータ５４の動作を制御することができる。この場合、推力設定部８８は、ＮＣ装置の入力部から構成でき、リニアモータ５４の推力目標値をオペレータがキー入力することができる。また表示部９８は、ＮＣ装置の表示部から構成でき、直動部材６４と複数のレバー６６との相対位置関係やリニアモータ５４の推力等を表示できる。
【００４３】
次に、推力制御機構８４によるチャック１４の動作制御及び把持力調整手順の一例を説明する。
まず、チャック１４が棒材Ｗを把持しないチャック開位置において、推力伝達装置６２の直動部材６４と複数のレバー６６との相対位置関係を、調節ナット８２を操作することにより調節する。このとき、図５（ａ）に示すように、直動部材６４と各レバー６６とが軸線方向へ僅かに離れるように配置してもよいが、この場合、慣性等により直動部材６４が主軸１２上で容易に回転するので、主軸１２の外周面１２ｂ及び直動部材６４の内周面６４ａが経時磨耗することが懸念される。そこで、チャック開位置では、各レバー６６の第１端６６ａが直動部材６４の係合面７０の第４領域７０ｄに僅かに乗り上げた状態にすることが好ましい。このチャック開位置における直動部材６４の位置は、例えばＮＣ装置の入力部を介して入力したパルス数データによりリニアモータ５４に指令され、また、開位置記憶部９４に記憶される。以後、チャック閉位置からチャック開位置に移行させるときには、制御部９６は開位置記憶部９４に記憶された直動部材６４の開位置データを読み出して、リニアモータ５４を動作制御する。
【００４４】
推力設定部８８では、リニアモータ５４の推力目標値として、所定寸法の棒材Ｗに対して適正なチャック把持力が得られる適正推力値Ｑ１と、適正推力値Ｑ１より僅かに大きい最大推力値Ｑ２と、適正推力値Ｑ１より小さく、チャック１４を閉じた後にその棒材把持状態を保持するための保持推力値Ｑ３とを予め設定し、これら推力値Ｑ１、Ｑ２、Ｑ３（図７）を推力記憶部９０に記憶する。制御部９６は、図７に示すように、チャック閉操作のＯＮ信号に基づき、リニアモータ５４を起動して、可動子５６及び直動部材６４を指定速度Ｖ１で、上記したチャック開位置からチャック閉方向（図３の右方向）に移動させる。それに伴い、前述したように、複数のレバー６６がそれらの第１端６６ａで直動部材６４の係合面７０に漸進的に乗り上げて同期回転するとともに、第２端６６ｂで作動部材４０を押圧して主軸１２の軸線方向前方に移動させる。この間、負荷の増加に対応して、リニアモータ５４の推力は漸増する。
【００４５】
作動部材４０の移動によりチャック１４は閉状態に移行する。このときリニアモータ５４を、その推力が適正推力値Ｑ１を超えて最大推力値Ｑ２に達するまで、速度Ｖ１で作動させる。そして、リニアモータ５４の推力が最大推力値Ｑ２に達した時点で、リニアモータ５４を一旦停止して、作動部材４０の前方移動を終了させる。この状態で、推力伝達装置６２の複数のレバー６６は、それらの第１端６６ａで直動部材６４の係合面７０の第２領域７０ｂに当接されている。
【００４６】
その直後に制御部９６は、リニアモータ５４を、その可動子５６が逆方向（図３の左方向）へ速度Ｖ２で僅かに移動するように動作させる。それにより、作動部材４０を実質的に移動させることなく、推力伝達装置６２からチャック１４に至る間に溜まった応力を解除するとともに、リニアモータ５４の推力を若干減少させる。そして、リニアモータ５４の推力が適正推力値Ｑ１まで減少した時点で、リニアモータ５４を停止する。このようにして、チャック１４の閉動作が完了する。
【００４７】
チャック１４が閉じた後、リニアモータ５４が適正推力値Ｑ１を発生し続けていると、必要以上に大きな負荷がリニアモータ５４に加わって過熱してしまう懸念がある。そこで、チャック１４の閉動作の完了後、リニアモータ５４の推力を、チャック１４の棒材把持状態を保持するに十分な保持推力値Ｑ３まで減少させる。したがって、リニアモータ５４が保持推力値Ｑ３を生じている状態で、チャック１４に把持された棒材Ｗに加工が施される。なお、チャック閉状態で、複数のレバー６６の第１端６６ａが直動部材６４の係合面７０の第１領域７０ａに当接されている場合は、保持推力値Ｑ３は実質的に零でよい。
【００４８】
このように、推力制御機構８４によれば、推力設定部８８で予め設定される推力値Ｑ１、Ｑ２、Ｑ３を適宜選択することにより、チャック閉状態での直動部材６４と複数のレバー６６との相対位置及び作動部材４０の軸線方向位置を調整し、以ってチャック１４の把持力を変更することができる。したがって、加工工程の途中であっても、棒材Ｗの外径寸法や剛性の変化に即時対応して、チャック１４の把持力を適宜自動調整することができる。
【００４９】
上記した素材把持装置１０は、チャック１４の把持力を自動調整するための他の手段として、リニアモータ５４の可動子５６の位置を制御することにより出力軸の直動制御を実施する位置制御機構１００をさらに備えることもできる。素材把持装置１０において、駆動部１８に装備されるリニアモータ５４がサーボモータである場合は、フィードバック制御用の位置検出器が備えられるので、この位置検出器を用いて位置制御機構１００を構成することができる。
【００５０】
図３及び図４に示すように、位置制御機構１００は、主軸台２２のハウジング５８の軸線方向後端領域に設置される少なくとも１つの非接触センサ１０２と、リニアモータ５４の可動子５６を支持する支持部材７２に固定されて軸線方向後方に延設され、非接触センサ１０２の感知部１０２ａに対向可能に配置される延長部材１０４とを備える。非接触センサ１０２及び延長部材１０４は、リニアモータ５４がサーボモータからなる場合、フィードバック制御用の位置検出器を構成できる。この場合、例えば自動旋盤に搭載されたＮＣ装置の制御部に、非接触センサ１０２の検出信号が送られる。
【００５１】
非接触センサ１０２は、例えば渦電流変位計やレーザ変位計から構成できる。延長部材１０４は、主軸１２の軸線方向後方へ向けて徐々に縮径する円錐台状の外周面１０４ａを有し、外周面１０４ａと非接触センサ１０２の感知部１０２ａとの間に可変ギャップを形成する。リニアモータ５４の可動子５６が推力伝達装置６２の前述した直線往復動作ストロークの前端位置にあるときに、非接触センサ１０２の感知部１０２ａと延長部材１０４の外周面１０４ａとの間のギャップは最大になり、このとき直動部材６４及び作動部材４０がチャック開位置に置かれる（図３）。また、リニアモータ５４の可動子５６が推力伝達装置６２の前述した直線往復動作ストロークの後端位置にあるときに、非接触センサ１０２の感知部１０２ａと延長部材１０４の外周面１０４ａとの間のギャップは最小になり、このとき直動部材６４及び作動部材４０がチャック閉位置に置かれる（図４）。直動部材６４及び作動部材４０がチャック開位置とチャック閉位置との間を移動する間に、非接触センサ１０２の感知部１０２ａと延長部材１０４の外周面１０４ａとの間のギャップは連続的に変化し、非接触センサ１０２はギャップ寸法に対応した信号を連続的に出力する。
【００５２】
このように、位置制御機構１００によれば、非接触センサ１０２が出力する信号に基づいて、リニアモータ５４の可動子５６の位置を適宜選択することにより、チャック閉状態での直動部材６４と複数のレバー６６との相対位置及び作動部材４０の軸線方向位置を調整し、以ってチャック１４の把持力を変更することができる。したがって、加工工程の途中であっても、棒材Ｗの外径寸法や剛性の変化に即時対応して、チャック１４の把持力を適宜自動調整することができる。なお、位置制御機構１００における非接触センサ１０２の使用は、リニアモータ５４の可動子５６及び延長部材１０４が主軸１２とともに回転することを許容するためのものである。したがって、延長部材１０４の軸線方向位置を接触式に感知する接触センサを、例えば軸受を介してハウジング５８に取り付けることによっても、位置制御機構を構成することができる。
【００５３】
図８は、本発明の他の実施形態による素材把持装置１１０を示す。素材把持装置１１０は、駆動部１１２の構成以外は、上記した素材把持装置１０と実質的同一の構成を有するので、対応の構成要素には共通する参照符号を付してその説明を省略する。
【００５４】
素材把持装置１１０の駆動部１１２には、リニアモータ１１４が装備される。リニアモータ１１４は、扁平型リニアモータ（例えばリニアステップモータ）からなり、主軸１２及び作動部材４０の軸線方向後端領域に略平行に離間して配置される平板状の可動子１１６と、主軸台２２のハウジング５８の内面に固定的に設置され、空隙を介して可動子１１６に対向する平板状の固定子１１８とを備える。図示実施形態では、リニアモータ１１４は、固定子１１８を一次側とし、かつ可動子１１６を二次側として構成されているが、その逆の構成とすることもできる。
【００５５】
リニアモータ１１４の可動子１１６は、支持部材１２０に固定的に支持され、支持部材１２０が軸受１２２を介して、推力伝達装置６２の直動部材６４に回動自在に連結される。したがって直動部材６４は、可動子１１６と一体的に主軸１２の軸線方向へ移動できる一方で、可動子１１６に対して主軸１２と共に回転できる。
【００５６】
上記構成を有する素材把持装置１１０によっても、前述した素材把持装置１０と同様に、素材把持装置１１０の全体寸法を削減することが容易であるとともに、チャック１４の作動効率を著しく向上させることができる。また、推力制御機構８４や位置制御機構１００を組み込むことにより、前述したようにリニアモータ１１４の出力軸（図示実施形態では支持部材１２０）を直動制御して、チャック１４の把持力を容易に自動調整できる。
【００５７】
図９は、本発明のさらに他の実施形態による素材把持装置１３０を示す。素材把持装置１３０は、作動機構１３２及び駆動部１３４の構成以外は、上記した素材把持装置１０と実質的同一の構成を有するので、対応の構成要素には共通する参照符号を付してその説明を省略する。
【００５８】
素材把持装置１３０の作動機構１３２は、主軸１２の貫通穴１２ａの軸線方向前端領域に、軸線方向摺動可能に同心に収容される作動部材１３６を備える。作動部材１３６は、前述した素材把持装置１０の作動部材４０における支持面４４の近傍で分割された前端側要素に対応するものであり、その軸線方向貫通穴１３６ａ内に、チャック１４を軸線方向摺動可能に同心に収容できる。作動部材１３６の貫通穴１３６ａの軸線方向前端領域には、チャック１４の把持部２８に設けた全テーパ面３６に係合可能な円錐台状の作用面４２が形成される。
【００５９】
駆動部１３４には、リニアモータ１３８が装備される。リニアモータ１３８は、円筒型リニアモータ（例えばリニアステップモータ）からなり、主軸１２の軸線方向中間領域を同心状に囲繞して配置される円筒状の可動子１４０と、主軸台２２のハウジング５８の内面に固定的に設置され、空隙を介して可動子１４０に対向する固定子１４２とを備える。図示実施形態では、リニアモータ１３８は、固定子１４２を一次側とし、かつ可動子１４０を二次側として構成されているが、その逆の構成とすることもできる。
【００６０】
素材把持装置１３０では、素材把持装置１０に装備された推力伝達装置６２が省略されている。その代わりに、リニアモータ１３８の可動子１４０は、支持部材１４４に固定的に支持されるとともに、支持部材１４４の軸線方向前端に設置された複数の作動爪１４６に固定的に連結される。支持部材１４４は、リニアモータ１３８の可動子１４０の内側に同心状に配置される筒状体であり、その内周面１４４ａを、主軸１２の筒状壁の外周面１２ｂに摺動可能に接触させて、主軸１２の軸線方向中間領域で主軸１２に同心に取り付けられる。複数の作動爪１４６は、支持部材１４４の軸線方向前端面に、好ましくは周方向等間隔配置で固定される。各作動爪１４６は、支持部材１４４の内周面１４４ａよりも径方向内側に突出して支持部材１４４の軸線方向へ延びる押圧部分１４６ａを有する。
【００６１】
主軸１２の軸線方向中間領域には、主軸１２の筒状壁を貫通する複数の開口部１４８が、好ましくは周方向へ等間隔に設けられる。複数の作動爪１４６は、それらの押圧部分１４６ａが、主軸１２の対応の開口部１４８を通って主軸１２の貫通穴１２ａ内に挿入される。この状態で、それら作動爪１４６の押圧部分１４６ａは、それぞれの軸線方向先端が作動部材１３６の軸線方向後端面に係合するとともに、それぞれの径方向端面１４６ｂが主軸１２内で被加工素材を挿通可能な距離だけ互いに離隔される。このようにして、複数の作動爪１４６は、リニアモータ１３８の可動子１４０と一体的に主軸１２の軸線方向へ移動して、リニアモータ１３８の推力を作動部材１３６に直接に伝えることができる。
【００６２】
上記構成を有する素材把持装置１３０によれば、前述した素材把持装置１０に比べて、推力伝達装置６２を省略した分、素材把持装置１３０の全体寸法をさらに削減することができる。しかも、推力伝達装置６２における伝達損失を除外できるので、チャック１４の作動効率が一層向上する。また、推力制御機構８４や位置制御機構１００を組み込むことにより、前述したようにリニアモータ１３８の出力軸（図示実施形態では支持部材１４４）を直動制御すれば、チャック１４の把持力の一層微妙な調整を容易に実施できる。ただしこの構成は、リニアモータ１３８の推力を拡大して作動部材１３６に伝達することができないので、時計部品等の小径素材、中空素材、外面の傷を嫌う素材のような、比較的小さな把持力が要求される用途に有効に利用できる。
【００６３】
図１０は、本発明のさらに他の実施形態による素材把持装置１５０を示す。素材把持装置１５０は、作動機構１５２及び推力伝達装置１５４の構成以外は、前述した素材把持装置１０と実質的同一の構成を有するので、対応の構成要素には共通する参照符号を付してその説明を省略する。
【００６４】
素材把持装置１５０は、上記した各素材把持装置１０、１１０、１３０と異なり、作動機構１５２が、チャック１４に固定的に連結される作動部材１５６を備えるとともに、推力伝達装置１５４が、リニアモータ５４の推力を作動部材１５６に伝達して、作動部材１５６をチャック１４と一体的に、主軸１２の軸線方向後方へ移動させることにより、チャック１４を開状態から閉状態に移行させるように構成される。したがって、主軸１２の軸線方向前端領域には、チャック１４の把持部外周の全テーパ面３６に係合可能なテーパ状の作用面１５８が形成される。推力伝達装置１５４の直動部材６４及び複数のレバー６６は、前述した推力伝達装置６２における相対配置と逆の相対配置で、主軸１２の軸線方向後端領域に設置される。被加工素材を把持する際には、リニアモータ５４の駆動により、作動部材１５６をチャック１４と共に主軸１２内へ引き込む方向へ移動させて、チャック１４のテーパ面３６を主軸１２先端の作用面１５８に押し付けることにより、所望の把持力を得る。このような構成においても、前述した素材把持装置１０の作用効果と同様の作用効果が奏されることは理解されよう。
【００６５】
【発明の効果】
以上の説明から明らかなように、本発明によれば、チャックを有する素材把持装置において、チャックの把持力を比較的容易に自動調整できる駆動部を備え、しかも装置の全体寸法を可及的に削減するとともに、チャックの作動効率を著しく向上させることが可能になる。したがって、この素材把持装置を自動旋盤に組み込めば、小型で高機能の自動旋盤が提供される。
【図面の簡単な説明】
【図１】本発明の一実施形態による素材把持装置を、自動旋盤の主軸台に組み込んだ状態で示す断面図である。
【図２】図１の素材把持装置のチャック及びその周辺部分を拡大して示す断面図である。
【図３】図１の素材把持装置の駆動部及びその周辺部分を拡大して示す断面図で、チャック開状態を示す。
【図４】図３に対応する断面図で、チャック閉状態を示す。
【図５】図１の素材把持装置の推力伝達装置の動作を説明する部分拡大断面図で、（ａ）チャック開位置、（ｂ）チャック閉位置、及び（ｃ）他のチャック閉位置をそれぞれ示す。
【図６】図１の素材把持装置に装備できる推力制御機構の構成を示すブロック図である。
【図７】図６の推力制御機構によるチャック閉動作制御のための駆動部の動作の一例を示す図である。
【図８】本発明の他の実施形態による素材把持装置を、自動旋盤の主軸台に組み込んだ状態で示す概略断面図である。
【図９】本発明のさらに他の実施形態による素材把持装置を、自動旋盤の主軸台に組み込んだ状態で示す概略断面図である。
【図１０】本発明のさらに他の実施形態による素材把持装置を、自動旋盤の主軸台に組み込んだ状態で示す概略断面図である。
【符号の説明】
１０、１１０、１３０、１５０…素材把持装置
１２…主軸
１４…チャック
１６、１３２、１５２…作動機構
１８、１１２、１３４…駆動部
４０、１３６、１５６…作動部材
４６…弾性部材
５４、１１４、１３８…リニアモータ
５６、１１６、１４０…可動子
６０、１１８、１４２…固定子
６２、１５４…推力伝達装置
６４…直動部材
６６…レバー
７０…係合面
７２、１２０、１４４…支持部材
８４…推力制御機構
１００…位置制御機構
１４６…作動爪[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a material gripping apparatus that can be installed in a machine tool. The present invention further relates to an automatic lathe provided with a material gripping device.
[0002]
[Prior art]
In a machine tool, a chuck having a gripping portion that can be opened and closed, an operating mechanism that opens and closes the gripping portion of the chuck, and a drive unit that drives the operating mechanism in order to hold a workpiece material during a machining process. Those equipped with a material gripping device having the following are known. For example, in a machine tool capable of performing automatic turning such as an NC lathe (generally referred to as an automatic lathe in the present specification), a chuck formed by forming a gripping portion having a slit structure capable of elastic deformation on a hollow cylindrical main body 2. Description of the Related Art A material gripping device is known in which a (generally referred to as a collet chuck) is concentrically disposed in an inner tip region of a hollow main shaft and an operation mechanism that operates to elastically deform a gripping portion of the chuck is provided along with the main shaft. It is. According to this configuration, the rod-shaped workpiece material fed in the axial direction from the rear of the main shaft into the main shaft is fixedly held on the main shaft via the chuck by the operation of the operation mechanism.
[0003]
Conventionally, in this type of material gripping device, a hydraulic or pneumatic cylinder device or a rotary electric motor is generally employed as a drive unit. For example, in a material gripping device incorporated in a main spindle of an automatic lathe, the operating mechanism is configured to include an operating member that can move in the axial direction of the main shaft, and the linear motion output of a cylinder device that is a drive unit or the rotation of an electric motor Generally, the output is transmitted to the operating member via a power transmission mechanism such as a lever assembly or a feed screw device (see, for example, JP-A-7-328819). In this configuration, the actuating member is moved in the axial direction along the main axis by driving the drive unit, whereby the gripping portion of the chuck is elastically deformed so that the inner diameter dimension thereof is reduced (that is, the diameter is reduced). Grab the material.
[0004]
[Problems to be solved by the invention]
In the conventional material gripping device described above, when a cylinder device is adopted as the drive unit, it is difficult not only to reduce the overall size of the material gripping device but also to changes in the outer diameter size and rigidity of the workpiece material. There is a problem that it is difficult to automatically adjust the gripping force of the chuck in an immediate manner. In addition, due to pressure loss that can occur in the cylinder device itself, the chuck operating efficiency tends to be low.
[0005]
On the other hand, when a rotary electric motor (usually a servo motor) is employed as the drive unit, there is an advantage that the gripping force of the chuck can be automatically adjusted relatively easily by controlling the rotation of the motor output shaft. However, since a power transmission mechanism such as a feed screw device is inevitably used, it is still difficult to reduce the overall size of the material gripping device. Moreover, since the feed screw device itself can cause transmission loss due to slipping, twisting, etc., it is difficult to effectively improve the operation efficiency of the chuck.
[0006]
An object of the present invention is to provide a material gripping device having a chuck with a drive unit that can relatively easily and automatically adjust the gripping force of the chuck, further reducing the overall size of the device as much as possible, and improving the operation efficiency of the chuck. An object of the present invention is to provide a material gripping device that can be remarkably improved.
Another object of the present invention is to provide a high-function automatic lathe equipped with such a material gripping device.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 A cylindrical body having a central axis and provided on the cylindrical body A chuck having a gripper capable of opening and closing; By moving in the axial direction of the cylindrical body relative to the chuck Actuating to open and close the chuck grip Element When, By thrust Operation Element The Linear motor that moves in the axial direction In a material gripping device comprising , Near motor Installed between the actuator and the actuating member, and includes a thrust transmission device that increases the thrust of the linear motor and transmits it to the actuating member. The thrust transmitting device is connected to the mover of the linear motor and is movable by driving the linear motor. A linear motion member that moves in the axial direction together with the child, a first end that engages with the linear motion member, and a second end that engages with the actuating member, and a support shaft that is linked to the axial movement of the linear motion member. And a lever member that turns and transmits thrust to the operating member by the action of the lever. A material gripping device is provided.
[0011]
Claim 2 The invention described in claim 1 In the material gripping device according to claim 1, the linear motion member has an engaging surface that is slidably engaged with the first end of the lever member, and the engaging surface grips the material on the gripping portion of the chuck. Provided is a material gripping device having a load reduction region that reduces a load applied to a linear motor via a thrust transmission device.
[0013]
Claim 3 The invention described in claim 1 Or 2 In the material gripping apparatus according to claim 1, the actuating member is formed of a cylindrical body disposed coaxially with the cylindrical main body of the chuck, and the linear motor is disposed in a cylindrical shape so as to surround at least a part of the actuating member. of A material gripping device having a mover is provided.
[0014]
Claim 4 The invention described in claim 1 3 The material gripping apparatus according to any one of the above, further includes a thrust control mechanism that adjusts the gripping force of the chuck by controlling the thrust of the linear motor.
[0015]
Claim 5 The invention described in claim 1 3 The material gripping device according to any one of the above, further includes a position control mechanism that adjusts the gripping force of the chuck by controlling the position of the mover of the linear motor.
[0016]
Contract Claim 6 The invention described in claim 1 5 An automatic lathe characterized in that the material gripping device according to any one of the above is incorporated into a main shaft.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the drawings, the same or similar components are denoted by common reference numerals.
FIG. 1 shows a material gripping device 10 according to an embodiment of the present invention in a state where it is incorporated in a spindle 12 of an automatic lathe. 2 and 3 each show an enlarged main part of the material gripping device 10 incorporated in the main shaft 12. The material gripping device 10 opens and closes a chuck 14 installed concentrically at the inner tip region of the axial through hole 12a of the main shaft 12 and a gripping portion described later of the chuck 14 to open and close a rod-shaped workpiece material W (FIG. 2). : Hereinafter referred to as a bar W) is provided with an actuation mechanism 16 for fixedly gripping, and a drive unit 18 for driving the actuation mechanism 16.
[0018]
The spindle 12 is rotatably mounted on a spindle stock 22 of an automatic lathe via a bearing device 20. In the illustrated embodiment, a built-in type AC servo motor is incorporated in the head stock 22 as a rotational drive device 24 that rotationally drives the main shaft 12. The main shaft 12 has a hollow cylindrical structure, and is rotationally driven by a rotation driving device 24 in a state where the bar W fed in the axial direction from the rear end thereof into the through hole 12a is held by the chuck 14 at a predetermined position. Is done. The rotation driving device of the main shaft 12 is not limited to the illustrated configuration, and an output shaft of an AC servo motor (not shown) provided outside the head stock 22 is used as a power transmission mechanism (not shown) such as a belt / pulley. The main shaft 12 may be connected to the main shaft 12.
[0019]
As shown in an enlarged view in FIG. 2, the chuck 14 includes a hollow cylindrical main body 26 that can receive the bar W therein, and a gripping portion that is provided in an axial front end (left end in the drawing) region of the cylindrical main body 26. 28. The grip portion 28 has a slit structure that can elastically change the inner diameter dimension with the central axis 26 a of the cylindrical body 26 as a reference. That is, the grip portion 28 includes a plurality of slits 30 that are engraved over a predetermined length in the axial direction in the front end region of the cylindrical body 26. The slits 30 are radially formed with respect to the central axis 26 a of the cylindrical body 26 and are arranged at equal intervals in the circumferential direction, and vertically split pieces 32 that can be displaced in the radial direction are formed between adjacent slits 30. . Each of the vertically split pieces 32 can be elastically deformed in a leaf spring shape in the radial direction of the cylindrical main body 26 with the base end as a fulcrum.
[0020]
The plurality of vertically divided pieces 32 provided in the grip portion 28 have arcuate curved surfaces on their inner surfaces, and the inner surfaces cooperate with each other to form a substantially cylindrical bar grip surface 34 of the grip portion 28. Constitute. The gripping portion 28 applies a radially inward external force uniformly to the plurality of vertically split pieces 32 to bend elastically, and reduce the diameter of the bar gripping surface 34 until it is in close contact with the bar W to be gripped. As a result, the bar W is firmly and securely held. When the radial pressure on the gripping portion 28 is released, each vertical split piece 32 is elastically restored, the bar gripping surface 34 is expanded, and the bar W is released from the gripping portion 28. Each vertically split piece 32 of the gripping portion 28 is formed with a tapered surface 36 on its outer surface for receiving an external force radially inward. The tapered surfaces 36 cooperate with each other to form a truncated cone-shaped pressure receiving surface that gradually extends in diameter toward the front end in the axial direction of the grip portion 28. Further, the taper surface 36 of each vertical split piece 32 is formed at a position separated from the front end surface of the grip portion 28 in the axial direction rearward, so that the central axis line is adjacent to the large diameter end of each taper surface 36. A shoulder surface 38 is formed extending substantially orthogonal to 26a.
[0021]
The operating mechanism 16 of the material gripping apparatus 10 includes an operating member 40 that is concentrically accommodated in the through hole 12a of the main shaft 12 so as to be slidable in the axial direction. The actuating member 40 is a long hollow cylindrical body that can receive the bar W, and the chuck 14 can be concentrically accommodated in the inner front end region of the axial through hole 40a so as to be slidable in the axial direction. A frustoconical action surface 42 that can be engaged with all the tapered surfaces 36 provided on the gripping portion 28 of the chuck 14 is formed in the front end region in the axial direction of the through hole 40 a of the operating member 40. The action surface 42 extends from the front end surface of the actuating member 40 with a gradually reduced diameter toward the rear in the axial direction, and is connected to the cylindrical inner peripheral surface of the actuating member 40 at the small diameter end. The inner diameter dimension of the small-diameter end of the working surface 42 is substantially equal to the outer diameter dimension of the small-diameter end of the pressure receiving surface formed by the tapered surface 36 of the grip portion 28 of the chuck 14. A pressurizing surface that is brought into contact with all the tapered surfaces 36 in a surface contact manner is formed.
[0022]
An annular support surface 44 extending in the radial direction is formed on the cylindrical inner peripheral surface of the actuating member 40 at a position away from the action surface 42 in the axial direction rearward by a predetermined distance, and the action surface 42 and the support surface 44 are separated from each other. The chuck 14 and the elastic member 46 are accommodated concentrically aligned in the axial direction in a region therebetween. The elastic member 46 is formed of a compression coil spring, for example, and is interposed between the rear end surface in the axial direction of the chuck 14 and the support surface 44 of the operating member 40 in an elastically bent state, so that the chuck 14 is disposed on the operating member 40. Biasing is performed in a direction away from the support surface 44 (that is, forward in the axial direction of the main shaft 12).
[0023]
At the tip of the main shaft 12, a cap 50 having an engaging surface 48 that can be engaged with all the shoulder surfaces 38 provided on the gripping portion 28 of the chuck 14 is detachably attached. When the cap 50 is attached to the distal end of the main shaft 12 in a state where the chuck 14 and the elastic member 46 are properly accommodated in the axial front end region of the operating member 40, the locking surface 48 engages with the entire shoulder surface 38 of the chuck 14. Then, the chuck 14 is held so as not to fall off the operating member 40 against the urging of the elastic member 46. When replacing the chuck 14, the cap 50 may be removed from the main shaft 12 and the chuck 14 may be extracted from the operating member 40.
[0024]
As shown in an enlarged view in FIG. 3, the axial rear end surface 40 b of the operating member 40 constitutes a driving force receiving surface that receives the driving force from the driving unit 18. In the vicinity of the rear end of the main shaft 12 in the axial direction, a plurality of openings 52 penetrating through the cylindrical wall of the main shaft 12 are preferably provided at equal intervals in the circumferential direction. An axial rear end surface 40b is positioned. As will be described later, the actuating member 40 receives the driving force of the driving unit 18 in the through hole 12a of the main shaft 12, and moves in the axial direction of the main shaft 12, that is, the axial direction of the cylindrical body 26 of the chuck 14 (FIG. 2). Thereby, the gripping portion 28 (FIG. 2) of the chuck 14 is elastically reduced in diameter. In the illustrated embodiment, the operating member 40 has a three-part structure divided in the vicinity of the support surface 44 (FIG. 2) and in the vicinity of the rear end surface 40b, but is not limited to this. Can also be included.
[0025]
The drive unit 18 of the material gripping apparatus 10 is equipped with a linear motor 54. The linear motor 54 includes a cylindrical linear motor (for example, a linear step motor), a cylindrical movable element 56 that is disposed concentrically surrounding the main shaft 12 and the rear end region in the axial direction of the operating member 40, and a main shaft base. And a stator 60 which is fixedly installed on the inner surface of the housing 58 and faces the mover 56 through a gap. In the illustrated embodiment, the linear motor 54 is configured with the stator 60 as the primary side and the mover 56 as the secondary side, but may be configured in the opposite manner. As will be described later, the linear motor 54 transmits the thrust to the operating member 40 and acts to move the operating member 40 in the axial direction of the main shaft 12, that is, in the axial direction of the cylindrical body 26 of the chuck 14.
[0026]
The material gripping device 10 is further provided with a thrust transmission device 62 that is installed between the linear motor 54 and the operating member 40 and increases the thrust of the linear motor 54 and transmits it to the operating member 40. The thrust transmission device 62 is coupled to the mover 56 of the linear motor 54, and is linked to the linear movement member 64 that can move integrally with the movable element 56 in the axial direction of the main shaft 12 and the axial movement of the linear movement member 64. A plurality of lever members 66 pivoting on the spindle (Hereafter, abbreviated as lever 66.) And is configured.
[0027]
The linear motion member 64 of the thrust transmission device 62 is a cylindrical body arranged concentrically on the inner side of the mover 56 of the linear motor 54, and its inner peripheral surface 64 a is used as the outer peripheral surface 12 b of the cylindrical wall of the main shaft 12. Are slidably contacted with each other and are concentrically attached to the main shaft 12 in the rear end region in the axial direction of the main shaft 12. The linear motion member 64 is further formed with a flange portion 68 projecting radially outward at one axial end of the linear motion member 64, and adjacent to the flange portion 68. The diameter of the linear motion member 64 gradually decreases toward the other axial end. A substantially conical outer peripheral surface extending, that is, an engagement surface 70. The linear motion member 64 is fixedly connected to a cylindrical support member 72 that directly supports the mover 56 of the linear motor 54 at its flange portion 68. Further, the linear motion member 64 is disposed so that its engagement surface 70 gradually decreases in diameter toward the rear end in the axial direction of the main shaft 12 in a state where it is properly attached to the main shaft 12.
[0028]
The plurality of levers 66 of the thrust transmission device 62 are arranged at equal intervals in the circumferential direction along the outer peripheral surface 12b of the main shaft 12 at the rearward position in the axial direction of the linear motion member 64. Each lever 66 includes a first end 66a that engages with the linear motion member 64 and a second end 66b that engages with the actuating member 40, and an intermediate point between the first end 66a and the second end 66b. The lever holder 74 installed in the rear end region in the axial direction of the main shaft 12 is rotatably supported via a support shaft 76. In the lever 66, the distance between the first end 66a and the support shaft 76 is sufficiently larger than the distance between the second end 66b and the support shaft 76, and the lever 66 can exert the function of the lever with the support shaft 76 as a fulcrum. It is like that.
[0029]
Each lever 66 is disposed at a position where the first end 66a can be slidably engaged with the engaging surface 70 of the linear motion member 64 in a state where the lever 66 is properly attached to the main shaft 12 via the lever holder 74. Is done. In this state, the second end 66 b of each lever 66 is received in a corresponding opening 52 formed in the rear end region of the main shaft 12, and the axial rear end face of the operating member 40 located in the opening 52. 40b is slidably engaged. At this time, as described above, when the cap 50 is attached to the front end of the main shaft 12 in a state where the chuck 14 and the elastic member 46 are properly accommodated in the axial direction front end region of the operating member 40, under the biasing force of the elastic member 46, The shoulder surface 38 of the chuck 14 is brought into contact with the locking surface 48 of the cap 50, and at the same time, the axial rear end surface 40 b of the operating member 40 is brought into contact with the second end 66 b of each lever 66 under the reaction force of the elastic member 46. Abutted. Thereby, each lever 66 is urged in a direction in which the first end 66 a approaches the outer peripheral surface 12 b of the main shaft 12, and the lever holder 74 is connected to the rear end in the axial direction of the main shaft 12 via the plurality of levers 66. It is urged toward.
[0030]
As shown in FIG. 4, the lever holder 74 has a guide pin 78 provided on the lever holder 74 engaged with a guide hole 80 provided on the cylindrical wall of the main shaft 12. Installed to be slidable in the axial direction. On the rear side in the axial direction of the lever holder 74, an adjusting nut 82 is installed that is screwed into the rear end region in the axial direction of the cylindrical wall of the main shaft 12. The adjustment nut 82 holds the lever holder 74 at a predetermined position on the main shaft 12 against the urging force of the elastic member 46 loaded on the lever holder 74 via the operating member 40 and the plurality of levers 66. Further, in this state where the biasing force of the elastic member 46 is loaded on the lever holder 74, the adjustment nut 82 is tightened or loosened on the main shaft 12, so that the lever holder 74 on the main shaft 12 and a plurality of The axial position of the lever 66 can be adjusted.
[0031]
As will be described later, the linear motion member 64 slides in the axial direction on the outer peripheral surface 12b of the main shaft 12 by driving the linear motor 54, and accordingly, on the engagement surface 70, the first end 66a of each lever 66 is slid. The plurality of levers 66 are rotated around the respective support shafts 76 in synchronization with each other. Here, as shown in an enlarged view in FIG. 5A, the angle formed between the engaging surface 70 of the linear motion member 64 and the inner peripheral surface 64a (that is, the outer peripheral surface 12b of the main shaft 12) increases stepwise. Thus, the diameter of the main shaft 12 is gradually reduced toward the rear end in the axial direction. In the illustrated embodiment, the engagement surface 70 is closest to the flange portion 68 and extends substantially parallel to the inner peripheral surface 64a, and adjacent to the rear of the first region 70a, the inner peripheral surface. A second region 70b extending at an angle of about 5 ° with respect to 64a, and a third region 70c adjacent to the rear of the second region 70b and extending at an angle of about 10 ° with respect to the inner peripheral surface 64a. And a fourth region 70d adjacent to the rear of the third region 70c and extending at an angle of about 25 ° with respect to the inner peripheral surface 64a. With such a configuration, the engaging surface 70 of the linear motion member 64 has the first and second regions 70a and 70b in particular, as will be described later, through the linear motor 54 via the thrust transmission device 62 during gripping of the bar. It can act to reduce the load applied to the.
[0032]
The operation mode of the material gripping apparatus 10 having the above configuration will be described below.
First, the operating member 40 is arranged at the chuck open position by the initial setting of the linear motor 54 constituting the drive unit 18, and the gripping unit 28 of the chuck 14 is placed in the open state. In this state, as shown in FIGS. 1 and 3, the mover 56 of the linear motor 54 is disposed at the front end (left end in the drawing) position of the linear reciprocating operation stroke together with the linear motion member 64 of the thrust transmission device 62. . Further, the engaging surface 70 of the linear movement member 64 is disposed at a position slightly away from the first ends 66a of the plurality of levers 66 in the axial direction, and therefore the first ends 66a of the respective levers 66 are elastic members 46. It is contact | abutted to the outer peripheral surface 12b of the main axis | shaft 12 under the urging | biasing force of (FIG. 5 (a)). Then, the working surface 42 of the operating member 40 is placed at a position where the tapered surface 36 of the gripping portion 28 of the chuck 14 is not substantially pressed (FIGS. 1 and 2). During this open state, a long bar W is inserted into the inside from the rear end of the main shaft 12, and is fed to the chuck 14 through the through hole 40 a of the operating member 40.
[0033]
When the required processing length of the bar W protrudes from the front end surface in the axial direction of the chuck 14, the feeding of the bar W is stopped. Therefore, the linear motor 54 is activated to move the movable element 56 together with the linear motion member 64 to the rear in the axial direction of the main shaft 12. Along with this, the plurality of levers 66 supported by the lever holder 74 gradually ride on the engaging surface 70 of the linear motion member 64 at their first ends 66a against the biasing of the elastic member 46. Thus, the shaft rotates in synchronization with the support shaft. When the plurality of levers 66 rotate synchronously in this manner, the levers 66 increase the thrust of the linear motor 54 under the action of the lever and transmit it to the operating member 40, and the operating member 40 at each second end 66b. The axial direction rear end face 40b is pressed. As a result, the operating member 40 moves forward in the axial direction in the through hole 12a of the main shaft 12 against the bias of the elastic member 46.
[0034]
Thereafter, when the movable element 56 and the linearly moving member 64 reach the rear end (right end in the figure) position of the linear reciprocating stroke, the operating member 40 is disposed at the chuck closed position, and the gripping portion 28 of the chuck 14 is closed. It is put in a state (FIG. 4). In this state, the working surface 42 of the actuating member 40 is pressed against the entire tapered surface 36 of the gripping portion 28 of the chuck 14, whereby all the vertical split pieces 32 of the gripping portion 28 are uniformly bent radially inward. The diameter of the bar holding surface 34 is reduced, and the bar W is firmly and securely held by the holding portion 28. Further, at the chuck closed position, the first end 66a of each lever 66 is subjected to the first region 70a (FIG. 5 (b)) of the engagement surface 70 of the linear motion member 64 or the first 2 abuts on the region 70b (FIG. 5C).
[0035]
Here, when the first end 66 a of each lever 66 is in contact with the first region 70 a of the engaging surface 70 of the linear motion member 64 (FIG. 5B), the operating member 40 and the lever 66 are interposed. The reaction force of the bar gripping force applied to the linear motion member 66 and the biasing force of the elastic member 46 cause the first end 66a of the lever 66 to move to the engagement surface first region 70a parallel to the outer peripheral surface 12b of the main shaft 12. Since it acts so as to press, a component force that urges the linear motion member 64 forward in the axial direction of the main shaft 12 is not substantially generated. Therefore, in this state, the load applied to the linear motor 54 becomes substantially zero, and as a result, the excitation of the linear motor 54 can be stopped.
[0036]
On the other hand, when the first end 66a of each lever 66 is in contact with the second region 70b of the engaging surface 70 of the linear motion member 64 (FIG. 5C), the operating member 40 and the lever 66 are interposed. Linear motion member 6 4 The reaction force of the bar gripping force and the biasing force of the elastic member 46 are applied to the first end 66a of the lever 66 against the engaging surface second region 70b inclined with respect to the outer peripheral surface 12b of the main shaft 12. Therefore, a component force that biases the linear motion member 64 forward in the axial direction, that is, a load applied to the linear motor 54 is generated. However, since the inclination angle of the second region 70b with respect to the outer peripheral surface 12b of the main shaft is as small as about 5 °, the load applied to the linear motor 54 is relatively small. As a result, the chuck 14 is held in the closed state with a small thrust of the linear motor 54. it can. Thus, the first and second regions 70a and 70b of the engaging surface 70 of the linear motion member 64 are linearly connected via the thrust transmission device 62 while the bar W is gripped by the gripping portion 28 of the chuck 14. It functions as a load reduction area that reduces the load applied to the motor 54.
[0037]
When the linear motor 54 is started from the closed state and the movable element 56 is moved together with the linear motion member 64 forward in the axial direction of the main shaft 12, the plurality of levers 66 are under the urging force of the elastic member 46. The first end 66a is slid along the engagement surface 70 of the linear motion member 64, and thereby the first end 66a is synchronized with the spindle 76 in the direction of approaching the main shaft outer peripheral surface 12b. Rotate. Accordingly, the actuating member 40 moves in the axial direction rearward in the through hole 12a of the main shaft 12 by the biasing force of the elastic member 46. As a result, the pressure applied to the entire tapered surface 36 of the gripping portion 28 of the chuck 14 by the action surface 42 of the operating member 40 is released, the diameter of the bar gripping surface 34 of the gripping portion 28 is increased, and the bar W Released from the chuck 14.
[0038]
As described above, according to the material gripping device 10 having the above-described configuration, the linear motor 54 is provided in the drive unit 18 that drives the operating member 40 of the operating mechanism 16, so that the conventional material gripping using a cylinder device as the drive unit is provided. Compared to the configuration of the apparatus, it is easy to reduce the overall size of the material gripping apparatus 10, and the operating efficiency of the chuck 14 can be significantly improved by eliminating the pressure loss of the cylinder apparatus. Moreover, the linear movement control of the output shaft of the linear motor 54 (the support member 72 in the illustrated embodiment) (to be described later) immediately responds to changes in the outer diameter size and rigidity of the bar W, and the gripping force of the chuck 14 is increased. There is an advantage that it can be adjusted automatically relatively easily. In addition, since the power transmission mechanism can be simplified by eliminating the feed screw device, it is easy to reduce the overall size of the material gripping device 10 as compared with a conventional material gripping device that employs a rotary electric motor as the drive unit. In addition, the operation efficiency of the chuck can be effectively improved by eliminating the transmission loss of the feed screw device. Therefore, in an automatic lathe in which the material gripping device 10 is incorporated in the main shaft 12, downsizing and higher functionality are promoted.
[0039]
In particular, since the material gripping apparatus 10 employs the cylindrical linear motor 54, it is not necessary to consider the alignment of the movable element 56 with respect to the stator 60 in the rotational direction. Therefore, the movable element 56 connected to the linearly moving member 64 slidably contacting the main shaft 12 can rotate together with the main shaft 12, and a bearing is interposed between the movable element 56 and the linearly moving member 64. Since it is not necessary, further miniaturization of the device and simplification of the structure are further promoted. Further, as a characteristic of the cylindrical linear motor 54 itself, since the magnetic attraction force is canceled and the thrust is not affected, there is an advantage that the eccentricity due to the magnetic attraction force during rotation of the spindle can be surely prevented.
[0040]
The material gripping device 10 described above further includes a thrust control mechanism 84 that performs linear motion control of the output shaft by controlling the thrust of the linear motor 54 as one means for automatically adjusting the gripping force of the chuck 14. Can do. In the material gripping device 10, the thrust of the linear motor 54 provided in the drive unit 18 is transmitted to the chuck 14 via the thrust transmission device 62 and the operation mechanism 16 and converted into the gripping force of the chuck 14. The gripping force is proportional to the thrust of the linear motor 54.
[0041]
As shown in FIG. 6, the thrust control mechanism 84 includes a thrust measurement unit 86 that measures the actual thrust during operation of the linear motor 54, and a thrust target value of the linear motor 54 that generates the required gripping force. A thrust setting unit 88 that is set in advance, a thrust storage unit 90 that stores a thrust target value set by the thrust setting unit 88, and a thrust target value in which the actual thrust measured by the thrust measurement unit 86 is stored in the thrust storage unit 90 A determination unit 92 that determines whether or not the position has reached, an open position storage unit 94 that stores the position of the linear motion member 64 at the chuck open position (FIG. 5A), a thrust measurement unit 86, a determination unit 92, and A control unit 96 that performs arithmetic processing on information received from the closed position storage unit 94 to control the operation of the linear motor 54 and a display unit 98 that displays processing results in the control unit 96 and the like are configured.
[0042]
The control unit 96 can be constituted by a CPU of a numerical control (NC) device mounted on an automatic lathe, for example, and controls the operation of the linear motor 54 in accordance with the timing chart shown in FIG. 7 stored in advance in the storage unit of the NC device. be able to. In this case, the thrust setting unit 88 can be configured by an input unit of the NC device, and an operator can input a thrust target value of the linear motor 54 by key input. The display unit 98 can be constituted by a display unit of the NC device, and can display the relative positional relationship between the linear motion member 64 and the plurality of levers 66, the thrust of the linear motor 54, and the like.
[0043]
Next, an example of the operation control and gripping force adjustment procedure of the chuck 14 by the thrust control mechanism 84 will be described.
First, in the chuck open position where the chuck 14 does not grip the bar W, the relative positional relationship between the linear motion member 64 of the thrust transmission device 62 and the plurality of levers 66 is adjusted by operating the adjustment nut 82. At this time, as shown in FIG. 5A, the linear motion member 64 and each lever 66 may be arranged so as to be slightly separated in the axial direction. In this case, the linear motion member 64 is driven by the inertia or the like. Therefore, the outer peripheral surface 12b of the main shaft 12 and the inner peripheral surface 64a of the linear motion member 64 may be worn over time. Therefore, in the chuck open position, it is preferable that the first end 66a of each lever 66 slightly rides on the fourth region 70d of the engaging surface 70 of the linear motion member 64. The position of the linear motion member 64 at the chuck open position is instructed to the linear motor 54 by pulse number data input via the input unit of the NC device, for example, and is stored in the open position storage unit 94. Thereafter, when shifting from the chuck closed position to the chuck open position, the control unit 96 reads the open position data of the linear motion member 64 stored in the open position storage unit 94 and controls the operation of the linear motor 54.
[0044]
In the thrust setting unit 88, as a thrust target value of the linear motor 54, an appropriate thrust value Q1 that provides an appropriate chuck gripping force with respect to the rod W having a predetermined dimension, and a maximum thrust value Q2 that is slightly larger than the appropriate thrust value Q1. And a holding thrust value Q3 that is smaller than the appropriate thrust value Q1 and holds the bar holding state after the chuck 14 is closed, and these thrust values Q1, Q2, and Q3 (FIG. 7) are stored in the thrust. Store in the unit 90. As shown in FIG. 7, the control unit 96 activates the linear motor 54 based on the ON signal of the chuck closing operation, and moves the mover 56 and the linear motion member 64 from the above-described chuck opening position at the specified speed V1. Move in the closing direction (right direction in FIG. 3). Accordingly, as described above, the plurality of levers 66 gradually ride on the engaging surface 70 of the linear motion member 64 at their first ends 66a and rotate synchronously, and press the operating member 40 at the second end 66b. Thus, the main shaft 12 is moved forward in the axial direction. During this time, the thrust of the linear motor 54 gradually increases corresponding to the increase in load.
[0045]
The chuck 14 shifts to the closed state by the movement of the operating member 40. At this time, the linear motor 54 is operated at the speed V1 until the thrust exceeds the appropriate thrust value Q1 and reaches the maximum thrust value Q2. When the thrust of the linear motor 54 reaches the maximum thrust value Q2, the linear motor 54 is temporarily stopped and the forward movement of the operating member 40 is ended. In this state, the plurality of levers 66 of the thrust transmission device 62 are in contact with the second region 70b of the engaging surface 70 of the linear motion member 64 at their first ends 66a.
[0046]
Immediately thereafter, the control unit 96 operates the linear motor 54 so that the movable element 56 slightly moves in the reverse direction (left direction in FIG. 3) at the speed V2. Accordingly, the stress accumulated during the period from the thrust transmission device 62 to the chuck 14 is released without substantially moving the operating member 40, and the thrust of the linear motor 54 is slightly reduced. Then, when the thrust of the linear motor 54 decreases to the appropriate thrust value Q1, the linear motor 54 is stopped. In this way, the closing operation of the chuck 14 is completed.
[0047]
If the linear motor 54 continues to generate the appropriate thrust value Q1 after the chuck 14 is closed, there is a concern that an unnecessarily large load is applied to the linear motor 54 and overheats. Therefore, after the closing operation of the chuck 14 is completed, the thrust of the linear motor 54 is reduced to a holding thrust value Q3 sufficient to hold the chuck 14 in the state of gripping the bar. Accordingly, the bar W gripped by the chuck 14 is processed while the linear motor 54 generates the holding thrust value Q3. If the first ends 66a of the plurality of levers 66 are in contact with the first region 70a of the engaging surface 70 of the linear motion member 64 in the chuck closed state, the holding thrust value Q3 is substantially zero. Good.
[0048]
As described above, according to the thrust control mechanism 84, by appropriately selecting the thrust values Q1, Q2, and Q3 set in advance by the thrust setting unit 88, the linear motion member 64 and the plurality of levers 66 in the chuck closed state are provided. The gripping force of the chuck 14 can be changed by adjusting the relative position and the axial position of the actuating member 40. Therefore, even in the middle of the processing step, the gripping force of the chuck 14 can be automatically adjusted appropriately in response to changes in the outer diameter size and rigidity of the bar W.
[0049]
The material gripping device 10 described above is a position control mechanism that performs linear motion control of the output shaft by controlling the position of the mover 56 of the linear motor 54 as another means for automatically adjusting the gripping force of the chuck 14. 100 may be further provided. In the material gripping apparatus 10, when the linear motor 54 provided in the drive unit 18 is a servo motor, a position detector for feedback control is provided, and thus the position control mechanism 100 is configured using this position detector. be able to.
[0050]
As shown in FIGS. 3 and 4, the position control mechanism 100 supports at least one non-contact sensor 102 installed in the axial rear end region of the housing 58 of the headstock 22 and the mover 56 of the linear motor 54. And an extending member 104 that is fixed to the supporting member 72 and extends rearward in the axial direction, and is disposed so as to face the sensing portion 102a of the non-contact sensor 102. The non-contact sensor 102 and the extension member 104 can constitute a position detector for feedback control when the linear motor 54 is a servo motor. In this case, for example, the detection signal of the non-contact sensor 102 is sent to the control unit of the NC device mounted on the automatic lathe.
[0051]
The non-contact sensor 102 can be composed of, for example, an eddy current displacement meter or a laser displacement meter. The extension member 104 has a frustoconical outer peripheral surface 104 a that gradually decreases in diameter toward the rear in the axial direction of the main shaft 12, and forms a variable gap between the outer peripheral surface 104 a and the sensing portion 102 a of the non-contact sensor 102. To do. When the mover 56 of the linear motor 54 is at the front end position of the above-described linear reciprocating stroke of the thrust transmission device 62, the gap between the sensing portion 102a of the non-contact sensor 102 and the outer peripheral surface 104a of the extension member 104 is maximum. At this time, the linear motion member 64 and the actuating member 40 are placed in the chuck open position (FIG. 3). Further, when the mover 56 of the linear motor 54 is at the rear end position of the above-described linear reciprocating operation stroke of the thrust transmission device 62, it is between the sensing portion 102a of the non-contact sensor 102 and the outer peripheral surface 104a of the extension member 104. The gap is minimized, at which time the linear motion member 64 and the actuating member 40 are placed in the chuck closed position (FIG. 4). While the linear motion member 64 and the actuating member 40 move between the chuck open position and the chuck close position, the gap between the sensing portion 102a of the non-contact sensor 102 and the outer peripheral surface 104a of the extension member 104 is continuously increased. The non-contact sensor 102 continuously outputs a signal corresponding to the gap size.
[0052]
As described above, according to the position control mechanism 100, the position of the movable element 56 of the linear motor 54 is appropriately selected based on the signal output from the non-contact sensor 102. The gripping force of the chuck 14 can be changed by adjusting the relative position with the plurality of levers 66 and the axial position of the operating member 40. Therefore, even in the middle of the processing step, the gripping force of the chuck 14 can be automatically adjusted appropriately in response to changes in the outer diameter size and rigidity of the bar W. The use of the non-contact sensor 102 in the position control mechanism 100 is to allow the mover 56 and the extension member 104 of the linear motor 54 to rotate together with the main shaft 12. Therefore, the position control mechanism can also be configured by attaching a contact sensor that senses the axial position of the extending member 104 to the housing 58 via a bearing, for example.
[0053]
FIG. 8 shows a material gripping device 110 according to another embodiment of the present invention. Since the material gripping device 110 has substantially the same configuration as that of the material gripping device 10 described above except for the configuration of the drive unit 112, the corresponding constituent elements are denoted by the same reference numerals, and description thereof is omitted.
[0054]
The drive unit 112 of the material gripping device 110 is equipped with a linear motor 114. The linear motor 114 is a flat type linear motor (for example, a linear step motor), and has a plate-like movable element 116 that is spaced apart from the main shaft 12 and the rear end region in the axial direction of the operating member 40 in a substantially parallel manner. And a flat plate-like stator 118 which is fixedly installed on the inner surface of the housing 58 and faces the mover 116 through a gap. In the illustrated embodiment, the linear motor 114 is configured with the stator 118 as the primary side and the mover 116 as the secondary side, but may be configured in the opposite manner.
[0055]
The mover 116 of the linear motor 114 is fixedly supported by the support member 120, and the support member 120 is rotatably connected to the linear motion member 64 of the thrust transmission device 62 via the bearing 122. Accordingly, the linear motion member 64 can move in the axial direction of the main shaft 12 integrally with the mover 116, and can rotate with the main shaft 12 with respect to the mover 116.
[0056]
Also with the material gripping device 110 having the above-described configuration, the overall size of the material gripping device 110 can be easily reduced and the operation efficiency of the chuck 14 can be remarkably improved, as with the material gripping device 10 described above. . Further, by incorporating the thrust control mechanism 84 and the position control mechanism 100, the output shaft of the linear motor 114 (the support member 120 in the illustrated embodiment) is linearly controlled as described above, and the gripping force of the chuck 14 is easily achieved. Can be adjusted automatically.
[0057]
FIG. 9 shows a material gripping device 130 according to still another embodiment of the present invention. The material gripping device 130 has substantially the same configuration as that of the material gripping device 10 described above except for the configuration of the operating mechanism 132 and the drive unit 134. Is omitted.
[0058]
The actuation mechanism 132 of the material gripping device 130 includes an actuation member 136 that is concentrically accommodated in the axial front end region of the through hole 12a of the main shaft 12 so as to be slidable in the axial direction. The actuating member 136 corresponds to the front end side element divided in the vicinity of the support surface 44 in the actuating member 40 of the material gripping device 10 described above, and the chuck 14 is slid in the axial direction in the axial through hole 136a. It can be moved concentrically. A frustoconical action surface 42 that can be engaged with the entire tapered surface 36 provided in the grip portion 28 of the chuck 14 is formed in the front end region in the axial direction of the through hole 136 a of the operation member 136.
[0059]
The drive unit 134 is equipped with a linear motor 138. The linear motor 138 includes a cylindrical linear motor (for example, a linear step motor). The linear motor 138 includes a cylindrical movable element 140 that is disposed concentrically around an intermediate region in the axial direction of the main shaft 12, and a housing 58 of the main shaft base 22. And a stator 142 that is fixedly installed on the inner surface and faces the mover 140 through a gap. In the illustrated embodiment, the linear motor 138 is configured with the stator 142 as the primary side and the mover 140 as the secondary side, but may be configured in the opposite manner.
[0060]
In the material gripping device 130, the thrust transmission device 62 provided in the material gripping device 10 is omitted. Instead, the mover 140 of the linear motor 138 is fixedly supported by the support member 144 and fixedly connected to a plurality of operating claws 146 installed at the front end in the axial direction of the support member 144. The support member 144 is a cylindrical body disposed concentrically on the inner side of the mover 140 of the linear motor 138, and its inner peripheral surface 144 a is slidably in contact with the outer peripheral surface 12 b of the cylindrical wall of the main shaft 12. Thus, it is concentrically attached to the main shaft 12 in the intermediate region in the axial direction of the main shaft 12. The plurality of operating claws 146 are fixed to the front end surface in the axial direction of the support member 144, preferably at equal intervals in the circumferential direction. Each operating claw 146 has a pressing portion 146 a that protrudes radially inward from the inner peripheral surface 144 a of the support member 144 and extends in the axial direction of the support member 144.
[0061]
In the intermediate region in the axial direction of the main shaft 12, a plurality of openings 148 penetrating the cylindrical wall of the main shaft 12 are preferably provided at equal intervals in the circumferential direction. The plurality of operating claws 146 have their pressing portions 146 a inserted into the through holes 12 a of the main shaft 12 through the corresponding openings 148 of the main shaft 12. In this state, the pressing portions 146a of the operating claws 146 have their respective axial ends engaged with the axial rear end surface of the operating member 136, and the respective radial end surfaces 146b are inserted through the workpiece in the main shaft 12. They are separated from each other by a possible distance. In this way, the plurality of operating claws 146 can move in the axial direction of the main shaft 12 integrally with the mover 140 of the linear motor 138 and transmit the thrust of the linear motor 138 directly to the operating member 136.
[0062]
According to the material gripping device 130 having the above-described configuration, the overall size of the material gripping device 130 can be further reduced as compared with the material gripping device 10 described above, because the thrust transmission device 62 is omitted. In addition, since the transmission loss in the thrust transmission device 62 can be excluded, the operation efficiency of the chuck 14 is further improved. Further, by incorporating the thrust control mechanism 84 and the position control mechanism 100, if the output shaft of the linear motor 138 (the support member 144 in the illustrated embodiment) is linearly controlled as described above, the gripping force of the chuck 14 is further subtle. Can be easily adjusted. However, since this configuration cannot increase the thrust of the linear motor 138 and transmit it to the actuating member 136, a relatively small gripping force such as a small-diameter material such as a watch part, a hollow material, or a material that dislikes scratches on the outer surface. Can be used effectively for applications that require
[0063]
FIG. 10 shows a material gripping apparatus 150 according to still another embodiment of the present invention. The material gripping device 150 has substantially the same configuration as that of the material gripping device 10 described above except for the configuration of the operation mechanism 152 and the thrust transmission device 154. Description is omitted.
[0064]
Unlike the above-described material gripping devices 10, 110, and 130, the material gripping device 150 includes an operating member 156 that is fixedly connected to the chuck 14, and a thrust transmission device 154 that is a linear motor 54. The thrust 14 is transmitted to the actuating member 156, and the actuating member 156 is moved integrally with the chuck 14 to the rear in the axial direction of the main shaft 12, so that the chuck 14 is shifted from the open state to the closed state. . Accordingly, a tapered working surface 158 that can engage with the entire tapered surface 36 on the outer periphery of the gripping portion of the chuck 14 is formed in the front end region in the axial direction of the main shaft 12. The linear motion member 64 and the plurality of levers 66 of the thrust transmission device 154 are installed in the rear end region in the axial direction of the main shaft 12 in a relative arrangement opposite to the relative arrangement in the thrust transmission device 62 described above. When gripping the workpiece material, the linear motor 54 is driven to move the actuating member 156 together with the chuck 14 in the direction of pulling it into the main shaft 12, so that the taper surface 36 of the chuck 14 becomes the working surface 158 at the tip of the main shaft 12. A desired gripping force is obtained by pressing. It will be understood that even in such a configuration, the same function and effect as those of the material gripping device 10 described above can be obtained.
[0065]
【The invention's effect】
As is apparent from the above description, according to the present invention, the material gripping device having a chuck is provided with a drive unit that can relatively easily and automatically adjust the gripping force of the chuck, and further, the overall dimensions of the device can be made as much as possible. It is possible to significantly reduce the operating efficiency of the chuck as well as to reduce the number. Therefore, if this material gripping device is incorporated in an automatic lathe, a small and highly functional automatic lathe is provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a material gripping device according to an embodiment of the present invention in a state where it is incorporated in a head stock of an automatic lathe.
2 is an enlarged cross-sectional view of the chuck and its peripheral portion of the material gripping apparatus of FIG.
3 is an enlarged cross-sectional view showing a drive unit and its peripheral portion of the material gripping apparatus of FIG. 1, showing a chuck open state.
4 is a cross-sectional view corresponding to FIG. 3, showing a chuck closed state.
5 is a partially enlarged cross-sectional view for explaining the operation of the thrust transmission device of the material gripping device of FIG. 1, wherein (a) chuck opening position, (b) chuck closing position, and (c) other chuck closing positions are respectively shown. Show.
6 is a block diagram showing a configuration of a thrust control mechanism that can be installed in the material gripping apparatus of FIG. 1;
7 is a diagram illustrating an example of the operation of a drive unit for chuck closing operation control by the thrust control mechanism of FIG. 6;
FIG. 8 is a schematic cross-sectional view showing a material gripping device according to another embodiment of the present invention in a state where it is incorporated in a head stock of an automatic lathe.
FIG. 9 is a schematic cross-sectional view showing a material gripping device according to still another embodiment of the present invention in a state where it is incorporated in a head stock of an automatic lathe.
FIG. 10 is a schematic cross-sectional view showing a material gripping device according to still another embodiment of the present invention in a state where it is incorporated in a head stock of an automatic lathe.
[Explanation of symbols]
10, 110, 130, 150 ... material gripping device
12 ... Spindle
14 ... Chuck
16, 132, 152 ... Actuating mechanism
18, 112, 134 ... drive unit
40, 136, 156 ... Actuating members
46. Elastic member
54, 114, 138 ... linear motor
56, 116, 140 ... mover
60, 118, 142 ... Stator
62, 154 ... thrust transmission device
64 ... Linear motion member
66 ... Lever
70 ... engagement surface
72, 120, 144 ... support member
84: Thrust control mechanism
100: Position control mechanism
146 ... Actuation claw

Claims

A chuck having a cylindrical main body having a central axis and a gripping portion that can be opened and closed provided on the cylindrical main body, and moving the gripping portion of the chuck in the axial direction of the cylindrical main body with respect to the chuck In a material gripping apparatus comprising an operating member that opens and closes and a linear motor that moves the operating member in the axial direction by thrust,
A thrust transmission device installed between the linear motor and the actuating member to increase the thrust of the linear motor and transmit the thrust to the actuating member;
The thrust transmission device is:
A linear motion member connected to the mover of the linear motor and moving in the axial direction together with the mover by driving the linear motor;
A first end that engages with the linearly moving member and a second end that engages with the actuating member, and pivots in conjunction with the axial movement of the linearly moving member; A lever member that transmits thrust to the actuating member;
A material gripping device characterized by this.

The linear motion member has an engagement surface that is slidably engaged with the first end of the lever member, and the engagement surface holds the material on the grip portion of the chuck. The material gripping device according to claim 1, further comprising a load reduction region that reduces a load applied to the linear motor via the thrust transmission device.

The actuating member is formed of a cylindrical body disposed coaxially with the cylindrical main body of the chuck, and the linear motor is disposed so as to surround at least a part of the operating member. The material gripping device according to claim 1, comprising:

The material gripping apparatus according to claim 1, further comprising a thrust control mechanism that adjusts a gripping force of the chuck by controlling the thrust of the linear motor.

The material gripping apparatus according to any one of claims 1 to 3, further comprising a position control mechanism that adjusts a gripping force of the chuck by controlling a position of the mover of the linear motor.

An automatic lathe characterized by incorporating the material gripping device according to any one of claims 1 to 5 into a main shaft .