JP3632225B2 - Grinding equipment - Google Patents

Description

【００１９】
この式（１）にて算出される工作物径の平均値Ａｄｗ（ｔ）は、工作物１回転中に測定された工作物径ｄｗの平均値である。なお、Ｎは工作物１回転当たりの工作物径測定回数であり、工作物Ｗの回転速度と前記サンプリング周期Δｔから決定される。
続いてステップ１０３同様にステップ１０４にて、ステップ１０２で入力された砥石位置ｄｘ（ｔ）および後述する第１バッファ３２ａ（図３参照）内に記憶保持されている砥石位置ｄｘ（ｔ−Δｔ），ｄｘ（ｔ−２ＮΔｔ），．．．，ｄｘ（ｔ−（Ｎ−１）Δｔ）から次式より砥石位置の平均値Ａｄｘ（ｔ）が算出される。
【００２０】
【数２】

【００２１】
ステップ１０５にて、前記入力された工作物径ｄｗおよび砥石位置ｄｘがメモリ３２内に設けられた第１バッファ３２ａに、前記算出された工作物径の平均値Ａｄｗおよび砥石位置の平均値Ａｄｘが第２バッファ３２ｂにそれぞれ格納される。
第１バッファ３２ａは図３に示すように、工作物１回転当たりの測定回数Ｎ個分の工作物径ｄｗおよび砥石位置ｄｘが格納される領域が設けられており、容量を越えたバッファ内の測定値（工作物径ｄｗおよび砥石位置ｄｘ）は古いものから削除され、常に１回前の測定値から工作物１回転分の測定値（ｄｗ（ｔ−Δｔ）からｄｗ（ｔ−ＮΔｔ）およびｄｘ（ｔ−Δｔ）からｄｘ（ｔ−ＮΔｔ））が保持されるようになっている。例えば、サンプリング周期Δｔが１０ｍｓで、工作物Ｗの回転数が２００／ｍｉｎとすると、工作物１回転あたりの測定回数Ｎは３０となり、３０個の測定値ｄｗ，ｄｘがそれぞれ保持される。
【００２２】
第２バッファ３２ｂは図４に示すように、工作物１回転当たりの測定回数Ｎ個分の工作物径の平均値Ａｄｗおよび砥石位置の平均値Ａｄｘが格納される領域が設けられており、第１バッファ３２ａ同様に容量を越えたバッファ内の測定値（工作物径の平均値Ａｄｗおよび砥石位置の平均値Ａｄｘ）は古いものから削除され、常に１回前の算出値から工作物１回転分の算出値（Ａｄｗ（ｔ−Δｔ）からＡｄｗ（ｔ−ＮΔｔ）およびＡｄｘ（ｔ−Δｔ）からＡｄｘ（ｔ−ＮΔｔ））が保持されるようになっている。
【００２３】
ステップ１０６にて工作物径ｄｗおよび砥石位置ｄｘがそれぞれ２Ｎ回以上測定されたか否かの判別がなされる。これは、第２バッファ３２ｂ内の工作物径の平均値Ａｄｗおよび砥石位置の平均値Ａｄｘの値が、測定値（工作物径ｄｗおよび砥石位置ｄｘ）のみから算出された値ですべて満たされたか否かの判別を行っている。すなわち、定寸装置２４による測定が始まってから工作物Ｗが１回転するまでは、第１バッファ３２ａ内の値は測定値ｄｗ，ｄｘで満たされないため、工作物Ｗが測定開始から２回転するまでは平均値Ａｄｗ，Ａｄｘの値は誤った値が算出される。そして、ステップ１０６で、測定回数が２Ｎ以上と判断される、すなわち、工作物Ｗが測定開始から２回転した場合にはステップ１０７に移行し、測定回数が２Ｎに満たない場合にはステップ１０１からステップ１０５を繰り返す。
【００２４】
ステップ１０７に移行すると、平均化工作物径ＤＷが次式にて算出される。
【００２５】
【数３】

【００２６】
この平均化工作物径ＤＷは、式（１）にて算出した工作物径の平均値Ａｄｗに時間的な補正をした値ある。すなわち、図６に示すように、算出した工作物径の平均値Ａｄｗ（ｔ）は工作物径の測定値ｄｗ（ｔ）に対してほぼ半回転分の時間差（Ｎ−１）Δｔ／２を有している。そこで、工作物Ｗの１回転中の工作物径ｄｗの変化を線形と仮定し、前回の工作物径の平均値Ａｄｗ（ｔ−ＮΔｔ）と今回の工作物径の平均値Ａｄｗ（ｔ）とから工作物径の変位の傾き（Ａｄｗ（ｔ）−Ａｄｗ（ｔ−ＮΔｔ））／ＮΔｔを算出し、この工作物径の変位の傾きに時間差（Ｎ−１）Δｔ／２を乗して工作物径の変位量を求めて今回の工作物径の平均値Ａｄｗ（ｔ）に加えて補正している。以上の演算により算出された平均化工作物径ＤＷ（ｔ）は時刻ｔにおける工作物径の測定値ｄｗからトルク変動に起因する周期的な変動やノイズによるバラツキを除去された値になる。そして、この平均化工作物径ＤＷ（ｔ）を時刻ｔでの工作物径として以下のステップを実行する。なお、図示はしないが測定を開始して一番最初に算出された平均化工作物径ＤＷは初期工作物径Ｄ０としてメモリに記憶保持される。
ステップ１０８にて、平均化砥石位置ＤＸ（ｔ）が平均化工作物径ＤＷと同様に次式にて算出される。
【００２７】
【数４】

【００２８】
そして、工作物径ＤＷと同様に、平均化砥石位置ＤＸ（ｔ）を時刻ｔでの砥石位置として以下のステップを実行する。ただし、後述するステップ１１３等で砥石位置ｄｘは変化量を算出しないので、ステップ１０４、ステップ１０８等を行わず、砥石位置の測定値ｄｘをそのまま使用してもよい。
ステップ１０９にて工作物径ｄｗおよび砥石位置ｄｘがそれぞれ３Ｎ回以上測定されたか否かの判別がなされる。これは、後述する第３バッファ３２ｃ内に平均化工作物径ＤＷおよび平均化砥石位置ＤＸの値がすべて満たされたか否かの判別を行っている。すなわち、定寸装置２４による測定が始まってから工作物Ｗが３回転すると第３バッファ３２ｃ内に平均化工作物径ＤＷおよび平均化砥石位置ＤＸが満たされる。そして、ステップ１０９で、測定回数が３Ｎ以上と判断される、すなわち、工作物Ｗが測定開始から３回転した場合にはステップ１１０に移行し、測定回数が２Ｎに満たない場合にはステップ１１５に移行する。
【００２９】
ステップ１１５に移行すると、前記式（３）および式（４）で算出された平均化工作物径ＤＷおよび平均化砥石位置ＤＸがメモリ３２内に設けられた第３バッファ３２ｃに記憶され、ステップ１０１に戻る。なお、この第３バッファ３２ｃは図５に示すように、第１第２バッファ３２ａ、３２ｂ同様、Ｎ個の平均化工作物径ＤＷおよび平均化砥石位置ＤＷが格納される領域が設けられており、容量を越えたバッファ内の算出値ＤＷ，ＤＸは古いものから削除され、常に１回前の算出値からＮ分の算出値（ＤＷ（ｔ−Δｔ）からＤＷ（ｔ−ＮΔｔ）およびＤＸ（ｔ−Δｔ）からＤＸ（ｔ−ＮΔｔ））が保持されるようになっている。
【００３０】
一方、ステップ１１０に移行すると、砥石位置ＤＸと工作物径ＤＷの差である研削残量ＤＲが次式で算出される。
【００３１】
【数５】

【００３２】
次にステップ１１１にて、定寸装置２４の異常判断の処理が行われる。この定寸装置異常判断処理を図７および図８のフローチャートにて詳細に説明する。
図７のステップ１５１にて前記式（５）にて算出された研削残量ＤＲが正か負、すなわち切り込みが有るか無いかの判別がなされる。切り込みが有る（ＤＲ＞０）と判断された場合はステップ１５２に移行し、切り込みが無い（ＤＲ＜０）と判断された場合には図８のステップ１７１に移行する。
【００３３】
切り込みが有ると判断された場合、ステップ１５２に移行するとスパークアウト等により砥石台１３が切り込みを停止しているかの判断がなされる。切り込みが停止されている場合は、後述するステップ１１２に移行し、切り込みが停止されていない場合にはステップ１５３に移行する。
ステップ１５３にて、現在の工作物径ＤＷ（ｔ）と工作物径最小値ＭｉｎＤＷの大小が比較され、現在の工作物径ＤＷ（ｔ）が最小値であるか、すなわち、工作物径ＤＷが減少しているか否かの判別がなされる。なお、工作物径最小値ＭｉｎＤＷは後述するステップ１５５にて工作物径ＤＷ（ｔ）が代入され、ステップ１５３が初めて実行される場合には以前の図略のステップで工作物径最小値ＭｉｎＤＷに上述した初期工作物径ＤＷ０が代入されている。
【００３４】
ステップ１５３で、現在の工作物径ＤＷ（ｔ）が最小値と判別されると（ＤＷ（ｔ）＜ＭｉｎＤＷ）、ステップ１５４に移行して所定の時間をカウントするカウンタＴＣ１をリセットし、ステップ１５５にて工作物径最小値ＭｉｎＤＷを現在の工作物径ＤＷ（ｔ）で更新して、後続のステップ１１２に移行する。
一方、ステップ１５３で、現在の工作物径ＤＷ（ｔ）が最小でない、すなわち工作物径ＤＷが減少しない場合には、ステップ１５６に移行してカウンタＴＣ１をカウントアップする。そして、ステップ１５７にて、カウンタＴＣ１があらかじめ設定された所定時間ＭａｘＴＣ１内の場合には図２のステップ１１２に移行し、カウンタＴＣ１が所定時間ＭａｘＴＣ１を越えた場合、すなわち、切り込みが有ると判断したのに工作物径ＤＷが所定時間減少しない場合には定寸装置２４の異常と判断して、ステップ１５８に移行して研削加工を中止し異常終了とする（後述する異常状態１の場合）。
【００３５】
また、ステップ１５１にて切り込み無し（ＤＲ＜０）と判断されると図８のステップ１７１に移行し、次式にて工作物１回転当たりの工作物径の変化量ＤＷ１を算出する。
【００３６】
【数６】

【００３７】
なお、この工作物１回転当たりの工作物径の変化量ＤＷ１は前記第３バッファ３２ｃ内に保持されている１回転前の工作物径ＤＷ（ｔ−ＮΔｔ）と現在の工作物径ＤＷ（ｔ）の差である。
ステップ１７２にて、上記式（６）にて算出した工作物１回転当たりの工作物径の変化量ＤＷ１があらかじめ設定された変化量の許容値ＭａｘＤＷ１と比較され、工作物１回転当たりの工作物径の変化量ＤＷ１が変化量の許容値ＭａｘＤＷ１内の場合は後続のステップ１７３に移行し、変化量の最大値ＭａｘＤＷ１を越えた場合、すなわち切り込みが無いと判断したのにの工作物１回転当たりの切り込み量が許容値を越えた場合には定寸装置２４の異常と判断して、ステップ１７８に移行して研削加工を中止し異常終了とする（後述する異常状態３（その１）の場合）。
【００３８】
ステップ１７３に移行すると、次式により工作物径測定開始からの工作物径の変化量ＤＷ２が算出される。
【００３９】
【数７】

【００４０】
なお、この工作物径測定開始からの工作物径の変化量ＤＷ２は、前記初期工作物径ＤＷ０と現在の工作物径ＤＷ（ｔ）の差である。
ステップ１７４にて、上記式（７）にて算出した工作物径測定開始からの工作物径の変化量ＤＷ２があらかじめ設定された変化量の許容値ＭａｘＤＷ２と比較される。工作物径測定開始からの工作物径の変化量ＤＷ２が変化量の最大値ＭａｘＤＷ２内の場合にはステップ１７４に移行し、工作物径測定開始からの工作物径の変化量ＤＷ２が減少量の許容値ＭａｘＤＷ２を越えた場合、すなわち切り込みが無いと判断したのに工作物径の測定を開始してからの切り込み量が許容値を越えた場合には定寸装置２４の異常と判断して、ステップ１７８に移行して研削加工を中止し異常終了とする（後述する異常状態３（その２）の場合）。
【００４１】
ステップ１７５に移行すると、工作物径ＤＷが減少しているかの判断がなされる。すなわち、現在の工作物径ＤＷ（ｔ）および第３バッファ３２ｃ内の１回前に算出した工作物径ＤＷ（ｔ−Δｔ）との大小が比較される。
ステップ１７５において、現在の工作物径ＤＷ（ｔ）が１回前に測定した工作物径ＤＷ（ｔ−Δｔ）よりも小さいと判別されると（ＤＷ（ｔ）＜ＤＷ（ｔ−Δｔ））、ステップ１７６に移行する。一方、現在の工作物径ＤＷ（ｔ）が１回前に測定した工作物径ＤＷ（ｔ−Δｔ）よりも同等もしくは大きいと判別されると（ＤＷ（ｔ）＞＝ＤＷ（ｔ−Δｔ））、ステップ１７６に移行して所定の時間をカウントするカウンタＴＣ２をリセットし、後続のステップ１１２に移行する。
【００４２】
ステップ１７６に移行すると、カウンタＴＣ２をカウントアップし、ステップ１７７にて、カウンタＴＣ２があらかじめ設定された所定時間ＭａｘＴＣ２内の場合には後続のステップ１１２に移行し、カウンタＴＣ２が所定時間ＭａｘＴＣ２を越えた場合、すなわち、切り込みが無いと判断したのに工作物径ＤＷが所定時間減少する場合には定寸装置２４の異常と判断して、ステップ１７８に移行して研削加工を中止し異常終了とする（後述する異常状態２の場合）。
【００４３】
以上に説明したように、ステップ１１１（ステップ１５１からステップ１７９）により以下の３つの状態により定寸装置２４の異常が判別される。
１．研削残量ＤＲ＞０（切り込み有り）でかつ一定時間（ＭａｘＴＣ１）の間、工作物径ＤＷが減少しない。すなわち、異物等により定寸装置２４がメカ的に作動せず測定が正常に行われない、もしくは定寸装置が２４が断線等により保持した値を出力し続けている等の異常。
【００４４】
２．研削残量ＤＲ＜０（切り込み無し）でかつ一定時間（ＭａｘＴＣ２）の間、工作物径ＤＷが減少する。すなわち、砥石１９と定寸装置２４の位置的誤差が大きい場合や、時間的なノイズが乗っている等の異常。
３．研削残量ＤＲ＜０（切り込み無し）でかつ一定時間（ＭａｘＴＣ２）の間、工作物径ＤＷの変化量が許容値以上である。すなわち、定寸装置２４が測定系の異常を起こしている等の場合に該当する。なお、本実施例において異常状態３は、
（その１）工作物１回転当たりの工作物径の変化量Ｄ１
（その２）工作物径測定開始からの工作物径の変化量Ｄ２
の２つ工作物径の変化量により異常を判断している。
【００４５】
なお、上述した定寸装置の異常判別処理において、研削残量ＤＲおよび工作物径の変化量Ｄ１，Ｄ２は、時間的な補正を行った値である平均化工作物径ＤＷおよび平均化砥石位置ＤＸによって算出しているが測定値ｄｗ，ｄｘや平均値Ａｄｗ，Ａｄｘより求めた研削残量および工作物径の変化量から定寸装置の異常判別を行ってもよい。
【００４６】
続いて図２のステップ１１２について説明する。ステップ１１２は研削加工の各種制御処理の全般が行われるステップであり、砥石台１３の切り込みをはじめとする加工制御が行われる。ここでは、ステップ１０７、１０８で算出した平均化工作物径ＤＷおよび平均化砥石位置ＤＸに基づいて工作物径の変化率の算出および砥石車１９と工作物Ｗの接触検知処理が行われる。
【００４７】
まず、工作物径の変化率の算出処理について詳細に説明する。この工作物径の変化率は、例えば、砥石台送り制御における研削残量を予測する処理に使用されるものである。ただし、この研削残量の予測処理は本発明の主旨と関係ないため説明を省略する。
工作物径の変化率ＤＷ’（ｔ）は次式により算出される。
【００４８】
【数８】

【００４９】
なお、この工作物径の変化率ＤＷ’（ｔ）は現在の工作物径ＤＷ（ｔ）および第３バッファ３２ｃに記憶されている１回前の工作物径ＤＷ（ｔ−Δｔ）の差をサンプリング周期Δｔで除したものである。この工作物径の変化量ＤＷ’（ｔ）は平均化処理された平均化工作物径ＤＷにより算出されるためにトルク変動に起因する周期的な変動やノイズによるバラツキから発生する誤差の小さい精度の良い値が求められている。
【００５０】
次に、図９に基づき砥石車１９と工作物Ｗの接触検知処理について説明する。この接触検知処理は研削開始位置の測定に使用されるものである。
まず、ステップ１９１にて工作物径ＤＷが減少しているかが判別される。すなわち、現在の工作物径ＤＷ（ｔ）が工作物径の最小値ＭｉｎＤＷと比較され現在の工作物径ＤＷ（ｔ）の方が小さい場合はステップ１９２に移行して工作物径の最小値ＭｉｎＤＷを更新しステップ１９３に移行する。一方、現在の工作物径ＤＷ（ｔ）の方が大きい場合には、砥石車１９と工作物Ｗは接触していないと判別しステップ１１２の種々の加工制御ルーチンを実行してステップ１１３に移行する。
【００５１】
ステップ１９３では、研削残量ＤＲが正、すなわち切り込みが有るか否かの判別を行う。ステップ１９３にて研削残量ＤＲ＞０の場合、砥石車１９と工作物Ｗは接触したと判別され、ステップ１９４で接触フラグをＯＮにし、ステップ１９５にて、この時の工作物径ＤＷ（ｔ）および砥石位置（ｔ）を接触点における工作物径ＤＷＣおよび砥石位置ＤＸＣとしてそれぞれメモリ３２に記憶する。そして、この接触点における工作物径ＤＷＣおよび砥石位置ＤＷＣはステップ１１２内の種々の加工制御ルーチンに使用される。
【００５２】
また、ステップ１９３で研削残量ＤＲが負（切り込み無し）と判断されると、砥石車１９および工作物Ｗは接触していないと判別しステップ１１５の種々の加工制御ルーチンを実行してステップ１１３に移行する。
以上に説明したように、接触検知処理（ステップ１９１からステップ１９５）においては、工作物径ＤＷが減少し、かつ、研削残量ＤＲ＞０である時に砥石車１９と工作物Ｗが接触したと判別しており、研削残量ＤＲ＜０になった時点のみで接触したことを判別する場合より正確に接触を検知できるようになっている。
【００５３】
以上の加工制御処理（ステップ１１２）を実行し、ステップ１１３に移行すると、上述したステップ１１５同様にステップ１０７およびステップ１０８で算出した現在の平均化工作物径ＤＷと平均化砥石位置ＤＸを第３バッファ３２ｃに記憶する。そして、ステップ１１４に移行すると、研削加工が完了したか否かが判断され、加工が途中の場合にはステップ１０１に戻りステップ１０１からステップ１１３を繰り返す。一方、ステップ１１６で加工が完了した場合にはプログラムを終了する。
【００５４】
なお、上述した実施例において、平均化工作物径ＤＷの算出の際、測定した工作物径ｄｗの工作物１回転分の測定値（ｄｗ（ｔ），ｄｗ（ｔ−Δｔ），・・・，ｄｗ（ｔ−ＮΔｔ））から算出しているが、この平均化する測定値の個数は図１０から図１３に示す実験結果より決定されている。
この実験は工作物の回転速度を２００／ｍｉｎ、定寸装置２４からの工作物径ｄｗの測定時間（サンプリング周期）Δｔを１０ｍｓした場合に、図１６の切り込みを行った場合の工作物径ＤＷの変化率（工作物径の変化率ＤＷ’）の時間的推移を示したグラフである。
【００５５】
図１０は測定した工作物径の測定値ｄｗそのものから工作物径の変化率ＤＷ’を算出したグラフである。図１１は工作物径の測定値ｄｗを１０個バッファリングして平均化した工作物径ＤＷより工作物径の変化率ＤＷ’算出したグラフである。同様に図１２は工作物径の測定値ｄｗを３０個、図１３は５０個バッファリングして算出した工作物径の変化率ＤＷ’を算出したグラフである。
【００５６】
すなわち、平均化する測定値の個数を１から増やしていくと工作物径の変化率ＤＷ’の変動の振幅は徐々に小さくなり、３０個の時変動の振幅ははぼ０になる。この場合、工作物回転速度をが２００／ｍｉｎでサンプリング周期が１０ｍｓなので工作物１回転当たりの径測定の回数Ｎは３０となり、これに相当する。つまり、平均化によって１回転周期の工作物径ｄｗの変動がキャンセルされたことになる。このことは、平均化処理の測定値数をさらに増加させて、５０とすると、再び周期的な変動が現れることから確認ができる。そこで、工作物径ＤＷは、定寸装置２４からのサンプリング周期とその時の工作物回転速度から算出される工作物１回転分の個数の測定値を平均化して求めるのがよい。
【００５７】
また、上述した実施例において、時間的な補正を行う手段としてステップ１０５にて工作物径の平均値Ａｄｗを工作物１回転分バッファリングし、前回の工作物径の平均値Ａｄｗ（ｔ−ＮΔｔ）と今回の工作物径の平均値Ａｄｗ（ｔ）の値から今回の平均化工作物径ＤＷ（ｔ）を求めている。しかし、現在の工作物径の平均値Ａｄｗ（ｔ）と前回工作物径の測定値ｄｗ（ｔ−ＮΔｔ）から、ステップ１０７で次式（９）により平均化工作物径ＤＷを求め、同様に、今回の砥石位置の平均値Ａｄｘ（ｔ）と前回砥石位置の測定値ｄｘ（ｔ−ＮΔｔ）により、ステップ１０５で次式（１０）により平均化砥石位置ＤＸを求めれば、ステップ１０５にて工作物径の平均値Ａｄｗおよび砥石位置の平均値Ａｄｘをバッファリングしなくてもよい。
【００５８】
【数９】

【００５９】
【数１０】

【００６０】
上記式（９）および式（１０）は、図１４のように補正したものである。この場合、上記実施例の工作物径ＤＷよりも精度は落ちるが、バッファリングするデータを少なくできるといった利点がある。
【００６１】
【発明の効果】
以上に述べたように本発明の研削装置は、工作物径を工作物１回転当たりの測定回数分の測定値を平均化した値より求めているので、トルクの変動に起因する周期的な変動やノイズによるバラツキを除去でき、精度の高い工作物径の測定が行え、高精度な砥石と工作物の接触検知や研削加工が行えるといった効果がある。その上、周期的な変動やバラツキを除去できるために各種研削制御で使用される工作物径の変化率の算出も可能になる。
【００６２】
また、本発明の研削装置は、算出された研削残量と工作物径の変化量の２つの条件に基づき定寸装置の異常を検知できるため、定寸装置の異常に起因する切り込みすぎによる手直し不可能な工作物の発生を防止できるといった効果がある。
【図面の簡単な説明】
【図１】本発明の実施例を示す研削装置の全体構成を示す図である。
【図２】本発明の実施例を示す研削装置の動作を示したフローチャートである。
【図３】第１バッファ３２ａを示した図である。
【図４】第２バッファ３２ｂを示した図である。
【図５】第３バッファ３２ｃを示した図である。
【図６】平均化工作物径算出を説明する説明図である。
【図７】定寸装置異常判別処理を示したフローチャートである。
【図８】定寸装置異常判別処理を示したフローチャートである。
【図９】接触検知処理を示したフローチャートである。
【図１０】工作物径の変化率を時間的推移で示した実験結果である。
【図１１】工作物径の変化率を時間的推移で示した実験結果である。
【図１２】工作物径の変化率を時間的推移で示した実験結果である。
【図１３】工作物径の変化率を時間的推移で示した実験結果である。
【図１４】平均化工作物径算出を説明する説明図である。
【図１５】工作物径および砥石位置を時間的推移で示したグラフである。
【図１６】工作物径の誤差を示したグラフである。
【図１７】本発明が対象とする研削装置の一例を主要部を示した図である。
【符号の説明】
１３ 砥石台
１９ 砥石車
２４ 定寸装置
３０ 制御装置
３２ メモリ
３２ａ 第１バッファ
３２ｂ 第２バッファ
３２ｃ 第３バッファ
Ｗ 工作物
ｄｗ 工作物径の測定値
ｄｘ 砥石位置の測定値
Ａｄｗ 工作物径の平均値
Ａｄｘ 砥石位置の平均値
ＤＷ 平均化工作物径
ＤＸ 平均化砥石位置
ＤＲ 研削残量
ＤＷ０ 初期工作物径
ＤＷ１ 工作物１回転当たりの工作物径の変化量
ＤＷ２ 測定開始からの工作物径の変化量[0001]
[Industrial application fields]
The present invention relates to a grinding apparatus for grinding an outer diameter of a workpiece. Specifically, the present invention relates to a grinding apparatus having an in-process sizing apparatus.
[0002]
[Prior art]
In a grinding apparatus such as a cylindrical grinder, as shown in FIG. 17, a grinding wheel base having a grinding wheel 19 that rotates with respect to a workpiece W supported by the centers 15a and 16a of the headstock and the tailstock is fed to be ground. The outer diameter of the surface Wa is ground. In this type of cylindrical grinding, in order to obtain high accuracy, the sizing device 24 is used to perform machining while measuring the outer diameter of the surface Wa to be ground during grinding (in-process sizing control).
[0003]
The sizing device 24 continuously measures the outer diameter of the surface Wa to be ground of the workpiece W, and outputs the measurement signal (analog signal) to the control device of the grinding device via the AD converter. It has become. The input measurement value is used at a predetermined sampling period in the control device of the grinding apparatus and is used as the measurement value at that moment.
[0004]
[Problems to be solved by the invention]
FIG. 15 shows the outer diameter of the surface Wa to be ground (hereinafter referred to as the workpiece diameter) dw measured by the sizing device 24 and the output of the wheel head measured from the encoder attached to the servo motor for driving the wheel head. An example of the measurement result which showed the time transition of position (henceforth a grindstone position) dx is shown. The grindstone position dx is measured at the same cycle as the sampling cycle of the sizing device 24, and the measured value is converted to the outer diameter of the surface to be ground Wa of the workpiece W. That is, it is stored as a value of the diameter when the distance from the rotation axis of the workpiece W to the tip position of the grinding wheel 19 is a radius. The diameter dw and the grindstone position dx in FIG. 15 change linearly when viewed macroscopically. However, when the workpiece diameter dw is viewed microscopically as shown in the enlarged view of the time transition of the workpiece diameter dw shown in FIG. 16, there are periodic fluctuations due to torque fluctuations and variations due to noise. However, since this variation is within an error range with respect to the workpiece diameter dw, there is an influence when the value of the workpiece diameter dw is directly used or when the remaining grinding amount that is the difference from the grinding wheel position dx is calculated. Don't give. However, when calculating the rate of change of the workpiece diameter, which is the slope of the workpiece diameter dw displacement, the error is diffused, so that the measured rate of change of the workpiece diameter dw is directly used. There was a problem that it could not be calculated.
[0005]
When the contact point between the workpiece W and the grinding wheel 19 is detected using this sizing device 24, the change in the workpiece diameter dw is monitored, and the time when the value of the workpiece diameter dw starts to decrease is shown. The contact point between the grinding wheel 19 and the workpiece W is actually contacted due to the above-described periodic variation caused by the torque variation and variations due to noise. There was a problem of misalignment.
[0006]
Further, in the in-process sizing control, grinding is performed according to the measurement value (workpiece diameter dw) from the sizing device 24. Therefore, the sizing device 24 is inconvenient for some reason, and an erroneous measurement value (workpiece) When the object diameter dw) is output to the control device of the grinding device, normal machining is not performed. If the measured value (workpiece diameter dw) from the sizing device 24 does not change despite the grinding by the grinding wheel 19, the cutting by the grinding wheel 19 is continued and the workpiece W is continued. Even if the target machining diameter is exceeded, cutting is made, and there is a problem that a workpiece W that cannot be reworked is generated.
[0007]
[Means for Solving the Problems]
The configuration of the invention according to claim 1 for solving the above-described problem is measured by the sizing device in a grinding device that performs grinding while measuring the diameter of the workpiece being processed using the sizing device. The workpiece diameter is input at a predetermined sampling period, and the measured value holding means for storing and holding as a measured value of the workpiece diameter, and at least one rotation of the workpiece diameter of the workpiece diameter stored and held by the measured value holding means Average value of the workpiece diameter obtained by averaging the measured values of the workpiece for the number of times per measurement, the measured value averaging means for obtaining each sampling period, and the workpiece diameter obtained by the measured value averaging means Calculate the slope of the change in the average value of Half of the time obtained by multiplying the sampling period by the number of measurements The average value correcting means for obtaining the averaged workpiece diameter corrected by multiplying by the above, the feed of the grinding wheel base as the workpiece diameter at the time of measurement of the sizing device the average workpiece diameter obtained by the average value correcting means And control means for controlling.
[0008]
Further, in the grinding apparatus, the grinding wheel position measuring means for measuring the position of the grinding wheel table at the predetermined sampling period, and the averaging workpiece in the grinding apparatus. Diameter And a grinding wheel remaining amount calculating means for calculating a remaining grinding amount at the time of measurement of the sizing device from the position of the grinding wheel table, and a grinding wheel and the work based on the remaining grinding amount obtained by the remaining grinding amount calculating means. It comprises contact detection means for detecting that an object has come into contact.
[0009]
Furthermore, the configuration of the invention according to claim 3 is as follows. 3. The grinding apparatus according to claim 2, wherein the measured value. A diameter change amount calculating means for calculating a change amount of the work piece diameter from the work piece diameter held by the holding means for each sampling period; ,Previous A sizing device abnormality determining means for determining an abnormality of the sizing device based on the remaining grinding amount calculated by the remaining grinding amount calculating means and the change amount of the workpiece diameter calculated by the diameter change amount calculating means; Consists of.
[0010]
[Action]
According to the first aspect of the present invention, when measurement of the workpiece diameter by the sizing device is started, the measured value of the workpiece diameter is inputted at a preset sampling cycle and stored by the measured value holding means. Retained. Then, the average value of the workpiece diameter is determined from the measured values of the workpiece for at least the number of measurements per rotation of the workpiece among the measured values of the workpiece diameter stored and held in the measured value holding means by the measured value averaging means. It is obtained at any time in the predetermined sampling period. Subsequently, the average value of the workpiece diameter obtained by the measurement value averaging means is temporally corrected by the average value correction means to obtain the averaged workpiece diameter. The averaged workpiece diameter obtained as described above is used as the workpiece diameter at the time of measurement by the sizing device, and grinding is performed by controlling the feed of the grinding wheel table by the control means.
[0011]
Further, the operation of the invention according to claim 2 is characterized in that the remaining grinding amount is calculated by the remaining grinding amount calculation means from the position of the grinding wheel platform measured by the grinding wheel position measuring means at the predetermined sampling period and the average workpiece diameter. Calculated. Then, contact between the workpiece and the grinding wheel is detected by the contact detection means based on the value of the remaining grinding amount.
Further, according to the third aspect of the present invention, when measurement of the workpiece diameter by the sizing device is started, the workpiece diameter is input at a sampling period set in advance by the workpiece diameter measuring means. The inputted workpiece diameter is stored and held by the measured value holding means. Then, the change amount of the workpiece diameter is obtained at any given sampling period from the measured value of the workpiece diameter stored and held in the measurement value holding means by the diameter change amount calculating means. Further, an abnormality of the sizing device is determined based on the position of the grinding wheel platform measured by the grinding wheel position measuring means at every predetermined sampling period and the change amount of the workpiece diameter calculated by the diameter change amount calculating means. Determined by abnormality determination.
[0012]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an overall configuration diagram of a grinding apparatus according to an embodiment of the present invention. A spindle 15 is mounted on a workpiece table 12 guided and supported on a bed 11 of a grinding machine 10 so as to be movable in the left-right direction (Z direction). A spindle stock 14 and a tailstock 16 which are supported by bearings are provided coaxially facing each other in the left-right direction, and the workpiece W is supported at both ends by centers 15 a and 16 a provided on the spindle 15 and the tailstock 16. The main shaft 15 is rotationally driven by a motor 18 provided on the main shaft base 14, and the workpiece W is rotated with the main shaft 15 by engaging a rotation stop member 17 whose left end protrudes from the main shaft 15.
[0013]
A grinding wheel base 13 is guided and supported on the bed 11 so as to be movable in a horizontal X direction orthogonal to the Z direction. A grinding wheel 19 such as a CBN grinding wheel is parallel to the main shaft 15 on the grinding wheel base 13. It is supported by a shaft 20 and is rotationally driven by a motor 22 via a V-belt rotation transmission mechanism 21. The servo motor 23 provided in the bed 11 is controlled and driven by a drive circuit 41 that operates based on a control pulse distributed from a pulse distribution circuit 34 of the numerical control device 30, and the grindstone table 13 via a feed screw device (not shown). Gives the feed in the X direction. A position detector 25 such as an encoder detects the movement position of the grindstone table 13 through the rotation angle of the servomotor 23, and this detected value is input to the numerical control device 30 through the sensor controller 42.
[0014]
The sizing device 24 installed on the workpiece table 12 engages the tip of the pair of measuring elements 34a with the surface to be ground of the workpiece W being ground, and continuously measures the outer diameter thereof. The measurement signal (analog signal) is input to the numerical controller 30.
As shown in FIG. 1, the numerical controller 30 is a central processing unit (CPU) 31 that controls and manages the entire grinding apparatus, a memory 32, an interface 33 that exchanges data with the outside, and a command from the CPU 31. And a pulse distribution circuit 34 for distributing and transmitting drive pulses. A sizing device 24 is connected to the CPU 31 via an AD converter 35, and a sensor controller 42 is also connected. The sensor controller 42 is controlled by the CPU 31 and is connected to the position detector 25 described above. Further, an input device 40 such as a keyboard for inputting control data or the like is connected to the interface 33, and the servo motor 23 is connected to the pulse distribution circuit 34 via a drive circuit 41. The memory 32 stores a machining program for machining the workpiece W, other data, and the like. Further, the memory 32 stores a grindstone position dx and workpiece diameter dw, a grindstone position average value Adx and a workpiece diameter average value Adw, an average grindstone position DX and an average workpiece diameter DW, which will be described later, per rotation of the workpiece. A first buffer 32a, a second buffer 32b, and a third buffer 32c are provided for storing and holding each of the measured times.
[0015]
Next, the operation of the present embodiment configured as described above will be described with reference to the flowchart shown in FIG. 2 and the explanatory diagrams shown in FIGS.
The CPU 31 of the numerical control device 30 rotates the grinding wheel 19 when the grinding device starts operating in response to a command from the input device 40, and the workpiece W supported by the headstock 14 and the tailstock 16 is driven at a predetermined speed by the motor 18. Rotate with. Further, measurement of the sizing device 24 is also started. Then, the program shown in the flowchart of FIG. 2 is executed. However, it is assumed that the following steps are all executed at every sampling period Δt. The sampling period Δt is a time for sampling the outer dimension of the surface to be ground of the workpiece W measured by the sizing device 24.
[0016]
First, the outer diameter (hereinafter referred to as workpiece diameter) dw of the surface to be ground of the workpiece W measured by the sizing device 24 in step 101 is input to the CPU 31 as a digital signal via the AD converter 35. . For the sake of explanation, the workpiece diameter at time t is denoted as dw (t).
In subsequent step 102, the cutting position (hereinafter referred to as the grinding wheel position) dx of the grinding wheel base 13 measured by the position detector 25 is input to the CPU 31 through the sensor controller 42. For the sake of explanation, the grindstone position at time t is denoted as dx (t). Further, the value of the grinding wheel position dx is converted into a diameter value when the outer diameter of the surface to be ground of the workpiece W, that is, the distance from the rotation axis of the workpiece W to the tip position of the grinding wheel 19 is defined as the radius. It shall be.
[0017]
In step 103, the workpiece diameter dw (t) input in step 101 and the workpiece diameters dw (t−Δt), dw (t) stored and held in a first buffer 32a (see FIG. 3) described later. -2NΔt),. . . , Dw (t− (N−1) Δt), the average value Adw (t) of the workpiece diameter is calculated from the following equation.
[0018]
[Expression 1]

[0019]
The average value Adw (t) of the workpiece diameter calculated by the equation (1) is an average value of the workpiece diameter dw measured during one rotation of the workpiece. Note that N is the number of times the workpiece diameter is measured per rotation of the workpiece, and is determined from the rotational speed of the workpiece W and the sampling period Δt.
Subsequently, in step 104 as in step 103, the grindstone position dx (t) input in step 102 and the grindstone position dx (t−Δt) stored and held in a first buffer 32a (see FIG. 3) described later. , Dx (t−2NΔt),. . . , Dx (t− (N−1) Δt), the average value Adx (t) of the grindstone position is calculated from the following equation.
[0020]
[Expression 2]

[0021]
In step 105, the calculated workpiece diameter dw and grindstone position dx are stored in the first buffer 32a provided in the memory 32, and the calculated average value Adw of the workpiece diameter and the average value Adx of the grindstone position are set. Each is stored in the second buffer 32b.
As shown in FIG. 3, the first buffer 32a is provided with an area for storing the workpiece diameter dw and the grindstone position dx corresponding to the number N of measurement times per rotation of the workpiece. The measured values (workpiece diameter dw and grindstone position dx) are deleted from the oldest one, and always measured values for one rotation of the workpiece (dw (t−Δt) to dw (t−NΔt) from the previous measured value and dx (t−Nt)) is held from dx (t−Δt). For example, if the sampling period Δt is 10 ms and the rotation speed of the workpiece W is 200 / min, the number of measurements N per rotation of the workpiece is 30, and 30 measurement values dw and dx are held respectively.
[0022]
As shown in FIG. 4, the second buffer 32b is provided with an area for storing the average value Adw of the workpiece diameter N times the number of times of measurement per rotation of the workpiece and the average value Adx of the grindstone position. As in the case of 1 buffer 32a, the measured values in the buffer exceeding the capacity (average value Adw of workpiece diameter and average value Adx of grindstone position) are deleted from the oldest one, and always one rotation of the workpiece from the previous calculated value. The calculated values (Adw (t−Δt) to Adw (t−NΔt) and Adx (t−Δt) to Adx (t−NΔt)) are held.
[0023]
In step 106, it is determined whether or not the workpiece diameter dw and the grindstone position dx are each measured 2N times or more. Whether the average value Adw of the workpiece diameter in the second buffer 32b and the average value Adx of the grindstone position are all satisfied with values calculated from only the measured values (workpiece diameter dw and grindstone position dx). It is determined whether or not. That is, since the value in the first buffer 32a is not filled with the measured values dw and dx from the start of measurement by the sizing device 24 until the workpiece W rotates once, the workpiece W rotates twice from the start of measurement. Until then, the average values Adw and Adx are calculated incorrectly. Then, in step 106, it is determined that the number of measurements is 2N or more, that is, when the workpiece W has made two rotations from the start of measurement, the process proceeds to step 107, and when the number of measurements is less than 2N, from step 101. Step 105 is repeated.
[0024]
In step 107, the averaged workpiece diameter DW is calculated by the following equation.
[0025]
[Equation 3]

[0026]
The averaged workpiece diameter DW is a value obtained by temporally correcting the workpiece diameter average value Adw calculated by the equation (1). That is, as shown in FIG. 6, the average value Adw (t) of the calculated workpiece diameter is a time difference (N−1) Δt / 2 corresponding to a half rotation with respect to the measured value dw (t) of the workpiece diameter. Have. Accordingly, assuming that the change in the workpiece diameter dw during one rotation of the workpiece W is linear, the previous average workpiece diameter value Adw (t−NΔt) and the current average workpiece diameter value Adw (t) From the displacement of the workpiece diameter (Adw (t) −Adw (t−NΔt)) / NΔt is calculated, and the workpiece difference is multiplied by the time difference (N−1) Δt / 2. The displacement amount of the workpiece diameter is obtained and corrected in addition to the average value Adw (t) of the workpiece diameter this time. The averaged workpiece diameter DW (t) calculated by the above calculation is a value obtained by removing periodic fluctuations due to torque fluctuations and variations due to noise from the measured diameter dw of the workpiece at time t. Then, the following steps are executed with the averaged workpiece diameter DW (t) as the workpiece diameter at time t. Although not shown, the averaged workpiece diameter DW calculated first after the start of measurement is stored and held in the memory as the initial workpiece diameter D0.
In step 108, the averaged grinding wheel position DX (t) is calculated by the following equation in the same manner as the averaged workpiece diameter DW.
[0027]
[Expression 4]

[0028]
Then, similarly to the workpiece diameter DW, the following steps are executed with the averaged grinding wheel position DX (t) as the grinding wheel position at time t. However, since the change amount of the grindstone position dx is not calculated in step 113 and the like which will be described later, the measured value dx of the grindstone position may be used as it is without performing steps 104 and 108.
In step 109, it is determined whether or not the workpiece diameter dw and the grindstone position dx are each measured 3N times or more. This determines whether or not all the values of the average workpiece diameter DW and the average grinding wheel position DX are satisfied in a third buffer 32c described later. That is, when the workpiece W rotates three times after the measurement by the sizing device 24 starts, the average workpiece diameter DW and the average grinding wheel position DX are filled in the third buffer 32c. In step 109, it is determined that the number of measurements is 3N or more, that is, if the workpiece W has rotated three times from the start of measurement, the process proceeds to step 110. If the number of measurements is less than 2N, the process proceeds to step 115. Transition.
[0029]
When the process proceeds to step 115, the averaged workpiece diameter DW and the averaged grindstone position DX calculated by the above equations (3) and (4) are stored in the third buffer 32c provided in the memory 32. Return. As shown in FIG. 5, the third buffer 32c is provided with an area for storing N averaged workpiece diameters DW and averaged grinding wheel positions DW, as in the first and second buffers 32a and 32b. The calculated values DW and DX in the buffer exceeding the capacity are deleted from the oldest ones, and the calculated values for N minutes from the previous calculated value (DW (t−Δt) to DW (t−NΔt) and DX (t DX (t−NΔt)) is held from −Δt).
[0030]
On the other hand, when the routine proceeds to step 110, the remaining grinding amount DR, which is the difference between the grinding wheel position DX and the workpiece diameter DW, is calculated by the following equation.
[0031]
[Equation 5]

[0032]
Next, at step 111, abnormality determination processing of the sizing device 24 is performed. This sizing apparatus abnormality determination process will be described in detail with reference to the flowcharts of FIGS.
In step 151 of FIG. 7, it is determined whether the remaining grinding amount DR calculated by the equation (5) is positive or negative, that is, whether there is a notch. If it is determined that there is a cut (DR> 0), the process proceeds to step 152. If it is determined that there is no cut (DR <0), the process proceeds to step 171 in FIG.
[0033]
If it is determined that there is a cut, the process proceeds to step 152 where it is determined whether the grindstone table 13 has stopped cutting due to spark-out or the like. When the cutting is stopped, the process proceeds to step 112 described later, and when the cutting is not stopped, the process proceeds to step 153.
In step 153, the current workpiece diameter DW (t) and the workpiece diameter minimum value MinDW are compared, and whether the current workpiece diameter DW (t) is the minimum value, that is, the workpiece diameter DW is It is determined whether or not it is decreasing. The workpiece diameter minimum value MinDW is substituted with the workpiece diameter DW (t) in step 155 to be described later. When step 153 is executed for the first time, the workpiece diameter minimum value MinDW is set to the workpiece diameter minimum value MinDW in the previous unillustrated steps. The initial workpiece diameter DW0 described above is substituted.
[0034]
When the current workpiece diameter DW (t) is determined to be the minimum value in step 153 (DW (t) <MinDW), the process proceeds to step 154 to reset the counter TC1 that counts a predetermined time, and step 155 The workpiece diameter minimum value MinDW is updated with the current workpiece diameter DW (t), and the process proceeds to the subsequent step 112.
On the other hand, when the current workpiece diameter DW (t) is not the minimum in step 153, that is, when the workpiece diameter DW does not decrease, the routine proceeds to step 156 and the counter TC1 is counted up. In step 157, if the counter TC1 is within the predetermined time MaxTC1 set in advance, the process proceeds to step 112 in FIG. 2, and if the counter TC1 exceeds the predetermined time MaxTC1, that is, it is determined that there is a cut. However, if the workpiece diameter DW does not decrease for a predetermined time, it is determined that the sizing device 24 is abnormal, and the process proceeds to step 158 to stop the grinding process and terminate abnormally (in the case of abnormal state 1 described later).
[0035]
If it is determined in step 151 that there is no notch (DR <0), the process proceeds to step 171 in FIG. 8, and a change amount DW1 of the workpiece diameter per rotation of the workpiece is calculated by the following equation.
[0036]
[Formula 6]

[0037]
The change DW1 in the workpiece diameter per one rotation of the workpiece is the workpiece diameter DW (t−NΔt) before one rotation held in the third buffer 32c and the current workpiece diameter DW (t ) Difference.
In step 172, the change amount DW1 of the workpiece diameter per rotation of the workpiece calculated by the above formula (6) is compared with a preset allowable value MaxDW1 of the change amount, and the workpiece per rotation of the workpiece. When the diameter change amount DW1 is within the change amount allowable value MaxDW1, the process proceeds to the subsequent step 173, and when the change amount exceeds the maximum value MaxDW1, that is, per rotation of the workpiece when it is determined that there is no incision. If the cutting amount exceeds the allowable value, it is determined that the sizing device 24 is abnormal, and the process proceeds to step 178 to stop the grinding process and terminate abnormally (in the case of abnormal state 3 (part 1) described later). ).
[0038]
When the process proceeds to step 173, a workpiece diameter change amount DW2 from the start of workpiece diameter measurement is calculated by the following equation.
[0039]
[Expression 7]

[0040]
The workpiece diameter change amount DW2 from the start of workpiece diameter measurement is the difference between the initial workpiece diameter DW0 and the current workpiece diameter DW (t).
In step 174, the workpiece diameter change amount DW2 calculated from the above-described equation (7) from the start of the workpiece diameter measurement is compared with a preset change amount allowable value MaxDW2. When the workpiece diameter change amount DW2 from the start of the workpiece diameter measurement is within the maximum value MaxDW2, the process proceeds to step 174, and the workpiece diameter change amount DW2 from the start of the workpiece diameter measurement is the decrease amount. When the allowable value MaxDW2 is exceeded, that is, when it is determined that there is no incision but the amount of cutting after the measurement of the workpiece diameter exceeds the allowable value, it is determined that the sizing device 24 is abnormal, The process proceeds to step 178, where the grinding process is stopped and the process ends abnormally (in the case of an abnormal state 3 (part 2) described later).
[0041]
In step 175, it is determined whether the workpiece diameter DW is decreasing. That is, the current workpiece diameter DW (t) is compared with the workpiece diameter DW (t−Δt) calculated one time before in the third buffer 32c.
If it is determined in step 175 that the current workpiece diameter DW (t) is smaller than the workpiece diameter DW (t−Δt) measured once before (DW (t) <DW (t−Δt)). The process proceeds to step 176. On the other hand, when it is determined that the current workpiece diameter DW (t) is equal to or larger than the workpiece diameter DW (t−Δt) measured once before (DW (t)> = DW (t−Δt). ), The process proceeds to step 176, the counter TC2 for counting a predetermined time is reset, and the process proceeds to the subsequent step 112.
[0042]
At step 176, the counter TC2 is counted up. At step 177, when the counter TC2 is within the preset predetermined time MaxTC2, the routine proceeds to the subsequent step 112, and the counter TC2 has exceeded the predetermined time MaxTC2. In this case, that is, when it is determined that there is no notch but the workpiece diameter DW decreases for a predetermined time, it is determined that the sizing device 24 is abnormal, the process proceeds to step 178, the grinding process is stopped, and the process ends abnormally. (In case of abnormal state 2 described later).
[0043]
As described above, in step 111 (steps 151 to 179), the abnormality of the sizing device 24 is determined based on the following three states.
1. The workpiece diameter DW does not decrease while the remaining grinding amount DR> 0 (with cutting) and for a certain time (MaxTC1). That is, abnormalities such as the sizing device 24 not mechanically operating due to foreign matter or the like and measurement is not performed normally, or the sizing device 24 continues to output the value held by the disconnection or the like.
[0044]
2. The workpiece diameter DW decreases while the remaining grinding amount DR <0 (no cutting) and for a certain time (MaxTC2). That is, abnormalities such as when the positional error between the grindstone 19 and the sizing device 24 is large or when temporal noise is on the wheel.
3. The amount of change in the workpiece diameter DW is greater than or equal to the allowable value during the grinding remaining amount DR <0 (no cutting) and for a certain time (MaxTC2). That is, it corresponds to the case where the sizing device 24 has an abnormality in the measurement system. In this embodiment, abnormal state 3 is
(Part 1) D1 of change in workpiece diameter per workpiece rotation
(Part 2) Change D2 of workpiece diameter from the start of workpiece diameter measurement
The abnormality is judged by the amount of change in the workpiece diameter.
[0045]
In the above-described abnormality determination process of the sizing device, the remaining grinding amount DR and the workpiece diameter changes D1 and D2 are the averaged workpiece diameter DW and the averaged grinding wheel position DX, which are values obtained by temporal correction. However, the abnormality determination of the sizing device may be performed from the remaining grinding amount obtained from the measured values dw and dx and the average values Adw and Adx and the change amount of the workpiece diameter.
[0046]
Next, step 112 in FIG. 2 will be described. Step 112 is a step in which various control processes of grinding are performed in general, and machining control including cutting of the grinding wheel base 13 is performed. Here, calculation of the change rate of the workpiece diameter and contact detection processing of the grinding wheel 19 and the workpiece W are performed based on the averaged workpiece diameter DW and the averaged grinding wheel position DX calculated in steps 107 and 108.
[0047]
First, the calculation process of the change rate of a workpiece diameter is demonstrated in detail. The change rate of the workpiece diameter is used for, for example, processing for predicting the remaining grinding amount in the wheel head feed control. However, since this grinding remaining amount prediction process is not related to the gist of the present invention, the description thereof is omitted.
The change rate DW ′ (t) of the workpiece diameter is calculated by the following equation.
[0048]
[Equation 8]

[0049]
The change rate DW ′ (t) of the workpiece diameter is the difference between the current workpiece diameter DW (t) and the previous workpiece diameter DW (t−Δt) stored in the third buffer 32c. Divided by the sampling period Δt. Since the workpiece diameter change amount DW ′ (t) is calculated by the averaged workpiece diameter DW subjected to the averaging process, the accuracy of the error caused by the periodic fluctuation due to the torque fluctuation and the variation due to noise is small. A good value is sought.
[0050]
Next, the contact detection process between the grinding wheel 19 and the workpiece W will be described with reference to FIG. This contact detection process is used for measuring the grinding start position.
First, in step 191, it is determined whether the workpiece diameter DW is decreasing. That is, the current workpiece diameter DW (t) is compared with the minimum workpiece diameter MinDW, and if the current workpiece diameter DW (t) is smaller, the process proceeds to step 192 and the minimum workpiece diameter MinDW. And the process proceeds to step 193. On the other hand, if the current workpiece diameter DW (t) is larger, it is determined that the grinding wheel 19 and the workpiece W are not in contact with each other, and various machining control routines in step 112 are executed, and the routine proceeds to step 113. To do.
[0051]
In step 193, it is determined whether the remaining grinding amount DR is positive, that is, whether there is a cut. If the remaining grinding amount DR> 0 in step 193, it is determined that the grinding wheel 19 and the workpiece W are in contact with each other. In step 194, the contact flag is turned ON. In step 195, the workpiece diameter DW (t ) And the grindstone position (t) are stored in the memory 32 as the workpiece diameter DWC and the grindstone position DXC at the contact point, respectively. The workpiece diameter DWC and the grindstone position DWC at this contact point are used for various machining control routines in step 112.
[0052]
If it is determined in step 193 that the remaining grinding amount DR is negative (no cutting), it is determined that the grinding wheel 19 and the workpiece W are not in contact with each other, and various machining control routines in step 115 are executed. Migrate to
As described above, in the contact detection process (from step 191 to step 195), the grinding wheel 19 and the workpiece W are in contact with each other when the workpiece diameter DW decreases and the remaining grinding amount DR> 0. The contact can be detected more accurately than when the contact is determined only when the remaining grinding amount DR <0.
[0053]
When the above machining control process (step 112) is executed and the process proceeds to step 113, the current average workpiece diameter DW and the average grinding wheel position DX calculated in step 107 and step 108 as in step 115 described above are stored in the third buffer. 32c. When the process proceeds to step 114, it is determined whether or not the grinding process is completed. If the process is in progress, the process returns to step 101 and steps 101 to 113 are repeated. On the other hand, when the machining is completed in step 116, the program is terminated.
[0054]
In the above-described embodiment, when the averaged workpiece diameter DW is calculated, measured values (dw (t), dw (t−Δt),..., One revolution of the workpiece diameter dw are measured. dw (t−NΔt)), the number of measurement values to be averaged is determined from the experimental results shown in FIGS.
In this experiment, when the rotation speed of the workpiece is 200 / min and the measurement time (sampling period) Δt of the workpiece diameter dw from the sizing device 24 is 10 ms, the workpiece diameter DW when the incision of FIG. 16 is performed. It is the graph which showed the time transition of change rate (workpiece diameter change rate DW ').
[0055]
FIG. 10 is a graph in which the change rate DW ′ of the workpiece diameter is calculated from the measured value dw itself of the measured workpiece diameter. FIG. 11 is a graph in which the workpiece diameter change rate DW ′ is calculated from the workpiece diameter DW obtained by buffering and averaging 10 measured workpiece diameter values dw. Similarly, FIG. 12 is a graph in which a workpiece diameter change rate DW ′ calculated by buffering 30 workpiece diameter values dw and FIG. 13 is calculated by buffering 50 workpiece diameters.
[0056]
That is, when the number of measurement values to be averaged is increased from 1, the amplitude of change in the workpiece diameter change rate DW ′ gradually decreases, and the amplitude of 30 time fluctuations becomes approximately zero. In this case, since the workpiece rotation speed is 200 / min and the sampling period is 10 ms, the number N of diameter measurements per workpiece rotation is 30, which corresponds to this. That is, the fluctuation of the workpiece diameter dw in one rotation cycle is canceled by averaging. This can be confirmed from the fact that when the number of measurement values in the averaging process is further increased to 50, periodic fluctuations appear again. Therefore, the workpiece diameter DW is preferably obtained by averaging the measured values of the number of one workpiece rotation calculated from the sampling period from the sizing device 24 and the workpiece rotation speed at that time.
[0057]
In the above-described embodiment, as a means for performing temporal correction, in step 105, the workpiece diameter average value Adw is buffered by one rotation of the workpiece, and the previous workpiece diameter average value Adw (t−NΔt). ) And the average value Adw (t) of the current workpiece diameter, the current averaged workpiece diameter DW (t) is obtained. However, from step 107, the average workpiece diameter DW is obtained by the following equation (9) from the current average workpiece diameter value Adw (t) and the previous measured workpiece diameter value dw (t−NΔt). If the average grindstone position DX is obtained by the following equation (10) in step 105 from the average value Adx (t) of the present grindstone position and the measured value dx (t−NΔt) of the previous grindstone position, the workpiece is obtained in step 105. The average value Adw of the diameter and the average value Adx of the grindstone position need not be buffered.
[0058]
[Equation 9]

[0059]
[Expression 10]

[0060]
The above formulas (9) and (10) are corrected as shown in FIG. In this case, the accuracy is lower than the workpiece diameter DW of the above embodiment, but there is an advantage that data to be buffered can be reduced.
[0061]
【The invention's effect】
As described above, the grinding apparatus according to the present invention obtains the workpiece diameter from the average value of the measurement values for the number of times of measurement per rotation of the workpiece, and therefore the periodic fluctuation caused by the fluctuation of the torque. It is possible to eliminate variations due to noise and noise, to measure the workpiece diameter with high accuracy, and to perform contact detection and grinding processing between the grinding wheel and the workpiece with high accuracy. In addition, since periodic fluctuations and variations can be removed, it is possible to calculate the rate of change of the workpiece diameter used in various grinding controls.
[0062]
In addition, since the grinding device of the present invention can detect abnormality of the sizing device based on the two conditions of the calculated remaining grinding amount and the change amount of the workpiece diameter, it is corrected by excessive cutting due to the abnormality of the sizing device. This has the effect of preventing the generation of impossible workpieces.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a grinding apparatus showing an embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of a grinding apparatus showing an embodiment of the present invention.
FIG. 3 is a diagram illustrating a first buffer 32a.
FIG. 4 is a diagram illustrating a second buffer 32b.
FIG. 5 is a diagram showing a third buffer 32c.
FIG. 6 is an explanatory diagram for explaining calculation of an averaged workpiece diameter.
FIG. 7 is a flowchart showing a sizing apparatus abnormality determination process.
FIG. 8 is a flowchart showing a sizing apparatus abnormality determination process.
FIG. 9 is a flowchart showing contact detection processing;
FIG. 10 is an experimental result showing the change rate of the workpiece diameter as a function of time.
FIG. 11 is an experimental result showing the change rate of the workpiece diameter as a function of time.
FIG. 12 is an experimental result showing the change rate of the workpiece diameter as a function of time.
FIG. 13 is an experimental result showing the change rate of the workpiece diameter as a function of time.
FIG. 14 is an explanatory diagram for explaining calculation of an averaged workpiece diameter.
FIG. 15 is a graph showing the workpiece diameter and the grindstone position over time.
FIG. 16 is a graph showing a workpiece diameter error.
FIG. 17 is a diagram showing a main part of an example of a grinding apparatus targeted by the present invention.
[Explanation of symbols]
13 Whetstone stand
19 Grinding wheel
24 Sizing device
30 Control device
32 memory
32a first buffer
32b Second buffer
32c 3rd buffer
W Workpiece
dw Workpiece diameter measurement
dx Measured value of grinding wheel position
Adw Average workpiece diameter
Adx Average value of grinding wheel position
DW Average workpiece diameter
DX Averaging wheel position
DR grinding remaining amount
DW0 Initial workpiece diameter
DW1 Change in workpiece diameter per workpiece rotation
DW2 Change in workpiece diameter from the start of measurement

Claims (3)

In a grinding device that performs grinding while measuring the workpiece diameter during processing using a sizing device,
A measured value holding means for inputting a workpiece diameter measured by the sizing device at a predetermined sampling cycle and storing and holding it as a measured value of the workpiece diameter;
An average value of the workpiece diameter obtained by averaging the measured values of the workpiece for at least the number of measurements per rotation of the workpiece stored in the measured value holding means is obtained for each sampling period. Means for averaging measured values;
An average corrected by calculating the inclination of the change in the average value of the workpiece diameter obtained by the measurement value averaging means, and multiplying the inclination by half of the time obtained by multiplying the sampling period by the number of measurements. Mean value correction means for determining the diameter of the workpiece,
A grinding apparatus comprising: control means for controlling the feed of the grindstone table by using the averaged workpiece diameter obtained by the average value correcting means as the workpiece diameter at the time of measurement by the sizing device. 2. The grinding apparatus according to claim 1, wherein the sizing device is measured from a grinding wheel position measuring means for measuring the position of the grinding wheel base at every predetermined sampling period, the average workpiece diameter and the position of the grinding wheel base. A remaining grinding amount calculating means for calculating the remaining grinding amount at the time, and a contact detecting means for detecting that the grinding wheel and the workpiece are in contact based on the remaining grinding amount obtained by the remaining grinding amount calculating means. A grinding device characterized by that. 3. The grinding apparatus according to claim 2, wherein a diameter change amount calculating means for calculating a change amount of a work piece diameter from the work piece diameter held in the measured value holding means for each sampling period, and the remaining grinding amount calculation. Sizing device abnormality determining means for determining abnormality of the sizing device based on the remaining grinding amount calculated by the means and the change amount of the workpiece diameter calculated by the diameter change amount calculating means. A characteristic grinding device.

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