JP3722050B2 - Drive device - Google Patents

Description

【００４２】
この数１におけるｆｒｏは圧電素子２６の両電極間におけるフリー共振周波数（圧電素子２６自体の電極間方向における機械共振周波数）、ｍｐは圧電素子２６の質量、ｍｆは駆動部材２８の質量をそれぞれ表わしている。なお、支持部材２４の質量は、共振系における圧電素子２６の機械共振周波数ｆｒに関係するが、支持部材２４の質量は圧電素子２６及び駆動部材２８の各質量ｍｐ，ｍｆを加算したものに比べて十分大きな値を有しており、機械共振周波数ｆｒに与える影響は小さいので演算パラメータとして考慮する必要はない。また、係合部材３０は、圧電素子２６の共振時には駆動部材２８に対して滑りを生じて実質的に共振系の要素として考慮する必要はないので、上記数１の演算パラメータとしては含まれていない。
【００４３】
図６（ａ）は、図５（ａ），（ｂ）のｆｄ１＜ｆｒ１＜ｆｄ２（▲２▼）の場合における振幅伝達特性を示す特性図であり、縦軸は駆動部材２８の振幅を表し、横軸は駆動部材２８の機械共振周波数ｆｒに対する駆動周波数ｆｄの比（ｆｄ／ｆｒ）を表す。図６（ｂ）は、図５（ａ），（ｂ）のｆｄ１＜ｆｒ１＜ｆｄ２（▲２▼）の場合における位相伝達特性を示す特性図であり、縦軸は位相を表し、横軸は駆動部材２８の機械共振周波数ｆｒに対する駆動周波数ｆｄの比（ｆｄ／ｆｒ）を表す。また、図７は、本発明に係る駆動装置１０に適用される駆動回路１４の具体的な動作を説明するための図である。
【００４４】
例えば、駆動周波数ｆｄ１が支持部材２４及び駆動部材２８が固着された状態での圧電素子２６の共振周波数ｆｒの最も低い機械共振周波数ｆｒ１の０．７５倍（ｆｄ１＝０．７５×ｆｒ１）となるように設定する。なお、説明の便宜上、直流電源電圧Ｖ１，Ｖ２をＶ１＝Ｖ２とする。すなわち、第１の駆動電圧Ｖｄ１及び第２の駆動電圧Ｖｄ２はＶｄ１＝Ｖｄ２となる。この場合、第１の駆動電圧Ｖｄ１は図７（ａ）に示すような矩形波となり、第２の駆動電圧Ｖｄ２は図７（ｂ）に示すような矩形波となる。圧電素子２６の両電極Ａ，Ｂには、第１の駆動電圧Ｖｄ１と第２の駆動電圧Ｖｄ２との差に相当する駆動電圧Ｖｄ（Ｖｄ＝Ｖｄ１−Ｖｄ２）が印加される。振幅伝達特性によって、第１の駆動電圧Ｖｄ１及び第２の駆動電圧Ｖｄ２に対する変位の高調波成分は各々除去され、残った変位の基本波成分は各々振幅と位相の変化を受ける。振幅伝達特性による振幅変化は、図６（ａ）に示すようにｒ１：ｒ２＝２．２５：０．７９４となる。また、位相伝達特性による位相の変化は、図６（ｂ）に示すようにθ１：θ２＝−９．７°：−１７３．２°となる。支持部材２４及び駆動部材２８が固着された状態での圧電素子２６の機械変位ｘは、第１の正弦波電圧Ｖｄ１ｃによる機械変位ｘ１と第２の正弦波電圧Ｖｄ２ｃによる機械変位ｘ２との合成変位（ｘ＝ｘ１＋ｘ２）となる（図７（ｄ））。また、支持部材２４及び駆動部材２８が固着された状態での圧電素子２６の速度ｖは、上記機械変位ｘ１を微分した速度ｖ１と機械変位ｘ２を微分した速度ｖ２との合成速度（ｖ＝ｖ１＋ｖ２）となる（図７（ｅ））。
【００４５】
ここで、図７（ｄ）に示す合成変位ｘの波形を見てみると、立ち上がり部Ｅで大きなふくらみが発生しており、鋸波形とはなっておらず、支持部材２４及び駆動部材２８が固着された状態での圧電素子２６の所望する機械変位ｘを得ることができない。また、支持部材２４及び駆動部材２８が固着された状態での圧電素子２６の速度ｖ１，ｖ２が略同相の場合に、合成速度ｖの波形は略台形形状になるが、図７（ｅ）に示す合成速度ｖの波形は略台形形状になっておらず、支持部材２４及び駆動部材２８が固着された状態での圧電素子２６の所望する速度を得ることはできない。そのため、支持部材２４及び駆動部材２８が固着された状態での圧電素子２６の所望する鋸波形の機械変位を得るためには第１の正弦波電圧Ｖｄ１ｃ、第２の正弦波電圧Ｖｄ２ｃの振幅と位相関係を操作する必要がある。この操作は機械共振周波数ｆｒ１の特性の変更は困難であるため、振幅の操作に関しては直流電源電圧Ｖ１又はＶ２の可変によって行い、位相の操作に関しては第１の駆動信号Ｓｄ１、第２の駆動信号Ｓｄ２の位相関係の可変によって行う。
【００４６】
そこで、直流電源電圧Ｖ１，Ｖ２を例えばＶ１：Ｖ２＝１：０．７に設定し、第２の駆動信号Ｓｄ２の位相を第１の駆動信号Ｓｄ１の位相に対して例えば６５°進ませる。これによって図７（ｆ）に示すような第２の駆動電圧Ｖｄ２''が得られる。このときの第２の正弦波電圧Ｖｄ２''による機械変位ｘ２''は図７（ｇ）に示す波形となる。機械変位ｘ１と機械変位ｘ２''との合成変位ｘ''は図７（ｇ）に示すような鋸波形となり、所望の機械変位を得ることができるようになる。また、このときの機械速度ｖ２''は図７（ｇ）に示す波形となる。機械速度ｖ１と機械速度ｖ２''との合成速度ｖ''は図７（ｇ）に示すような略台形波形となり、所望の機械速度を得ることができるようになる。
【００４７】
このように、第１の駆動回路１５１によって生成された所定の周波数の第１の駆動信号Ｓｄ１と、第２の駆動回路１５２によって生成された第１の駆動信号Ｓｄ１とは異なる所定の周波数の第２の駆動信号Ｓｄ２とを加算して電気機械変換素子である圧電素子２６に印加することで当該圧電素子２６が駆動される。このため、第１の駆動信号Ｓｄ１と第２の駆動信号Ｓｄ２の位相関係を操作することによって圧電素子２６の機械共振特性の有する位相伝達特性に頼ることなく、最適な機械変位の応答が得られる駆動装置が実現される。
【００４８】
また、第１の駆動信号Ｓｄ１と第２の駆動信号Ｓｄ２との位相関係を変化させることで電気機械変換素子である圧電素子２６の伸縮方向における駆動速度を変化させるため、例えば、鋸波形の最適状態の機械変位を得ている状態から第１の駆動信号Ｓｄ１と第２の駆動信号Ｓｄ２との位相関係を変化させることで当該変化量に応じた滑らかな速度変化を得ることができる。
【００４９】
図８は、駆動回路１４の別の構成例を示す図である。この図において、駆動回路１４'はブリッジ回路で構成され、第１の駆動回路１５１'と第２の駆動回路１５２'とから構成される。第１の駆動回路１５１'は、エンハンスメント型のＭＯＳ（Metal Oxide Semiconductor）型ＦＥＴ（Field Ｅffect Transistor）であるスイッチ素子Ｔｒ１からなる第１スイッチ回路１４１、同じくエンハンスメント型のＭＯＳ型ＦＥＴであるスイッチ素子Ｔｒ２からなる第２スイッチ回路１４２、図略の駆動電源からの直流電源電圧Ｖ１、波形発生器１４５'、コンデンサＣ１、入力抵抗Ｒ１及び帰還抵抗Ｒ２で構成される。第２の駆動回路１５２'は、エンハンスメント型のＭＯＳ型ＦＥＴであるスイッチ素子Ｔｒ３からなる第３スイッチ回路１４３、同じくエンハンスメント型のＭＯＳ型ＦＥＴであるスイッチ素子Ｔｒ４からなる第４スイッチ回路１４４、図略の駆動電源からの直流電源電圧Ｖ２、波形発生器１４６'、コンデンサＣ２、入力抵抗Ｒ３及び帰還抵抗Ｒ４で構成される。このように、第１の駆動回路１５１'に入力抵抗Ｒ１及び帰還抵抗Ｒ２を配置することによって、ゲインＧ１がＧ１＝Ｒ２／Ｒ１である増幅回路となり、同様に、第２の駆動回路１５２'に入力抵抗Ｒ３及び帰還抵抗Ｒ４を配置することによって、ゲインＧ２がＧ２＝Ｒ４／Ｒ３である増幅回路となる。ただし、ゲインＧ１，Ｇ２は充分大きいとする。
【００５０】
第１の駆動回路１５１'は、図略の駆動電源からの直流電源電圧Ｖ１がスイッチ素子Ｔｒ１のソート電極に供給され、接地される接続点ａとの間に第１スイッチ回路１４１及び第２スイッチ回路１４２の直列回路が接続される。第２の駆動回路１５２'は、図略の駆動電源からの直流電源電圧Ｖ２がスイッチ素子Ｔｒ３のソート電極に供給され、接地される接続点ａとの間に第３スイッチ回路１４３及び第４スイッチ回路１４４の直列回路が接続される。
【００５１】
第１スイッチ回路１４１を構成するスイッチ素子Ｔｒ１及び第３スイッチ回路１４３を構成するスイッチ素子Ｔｒ３はＰチャンネルＦＥＴであり、第２スイッチ回路１４２を構成するスイッチ素子Ｔｒ２及び第４スイッチ回路１４４を構成するスイッチ素子Ｔｒ４はＮチャンネルＦＥＴである。ＰチャンネルＦＥＴであるスイッチ素子Ｔｒ１，Ｔｒ３は駆動制御信号がローレベルのときにオンになり、ＮチャンネルＦＥＴであるスイッチ素子Ｔｒ２，Ｔｒ４は駆動制御信号がハイレベルのときにオンになる。なお、第１スイッチ回路１４１及び第２スイッチ回路１４２の接続点ｃと、第３スイッチ回路１４３及び第４スイッチ回路１４４の接続点ｄとの間に圧電素子２６が接続されてブリッジ回路が構成される。
【００５２】
第１の駆動信号Ｓｄ１'は直流阻止用のコンデンサＣ１を通じて入力抵抗Ｒ１に印加され、第１の駆動電圧Ｖｄ１'は第１の駆動信号Ｓｄ１'をゲインＧ１倍した電圧となる。同様に、第２の駆動信号Ｓｄ２'は直流阻止用のコンデンサＣ２を通じて入力抵抗Ｒ３に印加され、第２の駆動電圧Ｖｄ２'は第２の駆動信号Ｓｄ２'をゲインＧ２倍した電圧となる。
【００５３】
図９は、駆動回路１４'の原理的な動作を説明するための駆動電圧のパルス波形等を示す図である。図９（ａ）は、波形発生器１４５'から出力される第１の駆動信号Ｓｄ１'を表す正弦波であり、正弦波の振幅はＶ３である。図９（ｄ）は、波形発生器１４６'から出力される第２の駆動信号Ｓｄ２'を表す正弦波であり、正弦波の振幅はＶ４である。また、第１の駆動信号Ｓｄ１'と第２の駆動信号Ｓｄ２'との周波数の比は整数比であり、本実施の形態においてこの整数比は１：２である。
【００５４】
図９（ｂ）は、圧電素子２６に印加される第１の駆動電圧Ｖｄ１'を表す正弦波であり、図９（ｅ）は、圧電素子２６に印加される第２の駆動電圧Ｖｄ２'を表す正弦波である。図９（ｃ）は圧電素子２６に印加される駆動周波数ｆｄ１'の正弦波電圧Ｖｄ１ｃ'を表す波形であり、図９（ｆ）は圧電素子２６に印加される駆動周波数ｆｄ２'の正弦波電圧Ｖｄ２ｃ'を表す波形である。図９（ｇ）は第１の駆動電圧Ｖｄ１'と第２の駆動電圧Ｖｄ２'との差に相当する駆動電圧Ｖｄ'を表す図である。この駆動電圧Ｖｄ'が圧電素子２６の一方側の電極である電極Ａと他方側の電極である電極Ｂとから印加される。
【００５５】
このように、第１の駆動信号Ｓｄ１'及び第２の駆動信号Ｓｄ２'を正弦波とすることで、振幅伝達特性による高調波除去に留意しなくてもよくなるという利点がある。
【００５６】
また、第１の駆動回路１５１'によって生成された所定の周波数の正弦波である第１の駆動信号Ｓｄ１'と、第２の駆動回路１５２'によって生成された第１の駆動信号Ｓｄ１'とは異なる所定の周波数の正弦波である第２の駆動信号Ｓｄ２'とを加算して電気機械変換素子である圧電素子２６に印加することで当該圧電素子２６が駆動される。このため、第１の駆動信号Ｓｄ１'と第２の駆動信号Ｓｄ２'の位相関係を操作することによって圧電素子２６の機械共振特性の有する位相伝達特性に頼ることなく、最適な機械変位の応答が得られる駆動装置が実現される。
【００５７】
なお、本実施の形態では、第１の駆動信号及び第２の駆動信号としていずれも矩形波または正弦波を用いたが、本発明は特にこれに限定されず、いずれか一方が矩形波で他方が正弦波でもよい。この場合、駆動回路１４は、矩形波を発生させる第１の駆動回路１５１と正弦波を発生させる第２の駆動回路１５２'とで構成されるか、正弦波を発生させる第１の駆動回路１５１'と矩形波を発生させる第２の駆動回路１５２とで構成される。このように、第１の駆動信号及び第２の駆動信号として生成される波形は、いずれも矩形波またはいずれも正弦波またはいずれか一方が矩形波で他方が正弦波であるため、第１の駆動信号及び第２の駆動信号の波形に応じた駆動信号を得ることができる。
【００５８】
また、本実施の形態では、第１の駆動電圧Ｖｄ１のデューティ比Ｄ１あるいは第２の駆動電圧Ｖｄ２のデューティ比Ｄ２のうちの一方、または第１の駆動電圧Ｖｄ１のデューティ比Ｄ１及び第２の駆動電圧Ｖｄ２のデューティ比Ｄ２の両方が０．５であり、Ｄ１＋Ｄ２＝１の関係にある矩形波を用いたが、本発明は特にこれに限定されず、デューティ比Ｄ１，Ｄ２が０．５以外で、Ｄ１＋Ｄ２＝１の関係でない矩形波を用いてもよい。この場合、例えば図５（ａ）に示すｆｄ１＜ｆｄ２＜ｆｒ１（▲１▼）の関係にある駆動周波数の設定方法を選択したとすると第１の駆動電圧Ｖｄ１の第３高調波が機械共振周波数ｆｒ１の近傍に存在する可能性が高くなる。そのため、共振特性によって支持部材２４及び駆動部材２８が固着された状態での圧電素子２６の駆動周波数の第３高調波に対する機械変位の応答に悪影響を及ぼす（鋸波形とならない）可能性がある。そこで、第２の駆動電圧Ｖｄ２のデューティ比Ｄ２は０．５のままで、第１の駆動電圧Ｖｄ１にデューティ比Ｄ１が０．３３または０．６７の矩形波電圧を用いることで第１の駆動電圧Ｖｄ１には第３高調波成分が含まれなくなり、上記問題は解決される。このように、第１の駆動信号Ｓｄ１と第２の駆動信号Ｓｄ２とが互いに周波数が同じであり、第１の駆動信号Ｓｄ１のデューティ比Ｄ１と第２の駆動信号Ｓｄ２のデューティ比Ｄ２とが、Ｄ１＋Ｄ２＝１の関係にない場合にも適用することができ、設定の自由度が増すこととなる。
【００５９】
また、本発明に係る駆動装置の圧電素子の機械負荷の速度を変化させる場合や反転させる場合は、図７（ｇ）に示す鋸波形の機械変位を得ている状態から、第１の駆動信号Ｓｄ１と第２の駆動信号Ｓｄ２との位相関係を変化させることで、当該変化量に応じて鋸波形の機械変位は最適状態から外れていくため速度は徐々に低下する。そして、変化量をさらに増加させることで停止に至り、ついには反転した鋸波形が得られるため、変化量に応じた滑らかな速度変化を得ることができる。つまり、駆動装置の機械負荷の速度制御を第１の駆動信号Ｓｄ１と第２の駆動信号Ｓｄ２との位相差で行うことが可能となる。
【００６０】
また、圧電素子２６には、図４（ｇ）に示す駆動電圧Ｖｄによると１周期について３回の充放電が存在している。この放電時には、原理的に一旦０ボルトになる期間が存在する（図４（ｇ）のＥ１，Ｅ２，Ｅ３）。これは、駆動回路１４のトランジスタ（スイッチ素子Ｔｄ１，Ｔｒ２，Ｔｒ３，Ｔｒ４）による圧電素子２６の短絡放電動作である。従来のデューティ矩形波駆動は、駆動電圧の１周期について１回の充放電が存在し、放電時は短絡放電動作ではなく直流電源を通じての放電動作となるので、放電電流が駆動電源に流れて当該駆動電源での消費電力が加算され、その結果駆動時の消費電力が大きくなっている。従来のデューティ矩形波駆動での消費電力Ｐ１は下記の（１）式で表される。
【００６１】
Ｐ１＝Ｃ×（２Ｖ）²×ｆｄ＝４×Ｃ×Ｖ²×ｆｄ・・・・（１）
ただし、従来のデューティ矩形波駆動での消費電力をＰ１とし、圧電素子の静電容量をＣとし、直流電源電圧をＶとし、駆動周波数をｆｄとする。
【００６２】
しかしながら、本発明に係る駆動回路では、消費電力Ｐ２は下記の（２）式で表される。
Ｐ２＝３×Ｃ×Ｖ²×ｆｄ・・・・（２）
【００６３】
このように、本発明に係る駆動回路の消費電力Ｐ２は従来の駆動回路の消費電力Ｐ１の０．７５倍となり、消費電力が向上されることとなる。
【００６４】
なお、本実施の形態ではカメラの撮影レンズに関する駆動装置で説明したが、本発明は特にこれに限定されず、ＸＹ移動ステージ、オーバーヘッドプロジェクタの投影レンズ及び双眼鏡のレンズ等の駆動に適した駆動装置にも適用可能である。
【００６５】
【発明の効果】
請求項１に記載の発明によれば、第１の駆動手段によって生成された所定の周波数の第１の駆動信号と、第２の駆動手段によって生成された第１の駆動信号とは異なる所定の周波数の第２の駆動信号とを加算して電気機械変換素子に印加することで当該電気機械変換素子が駆動される。このため、第１の駆動信号と第２の駆動信号の位相関係を操作することによって電気機械変換素子の機械共振特性の有する位相伝達特性に頼ることなく、最適な機械変位の応答を得ることができる。
【００６７】
また、第１の駆動信号の周波数と第２の駆動信号の周波数との比が整数比である駆動装置に適用することができる。
【００６８】
請求項２に記載の発明によれば、第１の駆動信号の周波数と第２の駆動信号の周波数との比が１：２である駆動装置に適用することができる。
【００６９】
請求項３に記載の発明によれば、第１の駆動信号と第２の駆動信号との位相関係を変化させることで電気機械変換素子の伸縮方向における駆動速度を変化させるため、例えば、鋸波形の最適状態の機械変位を得ている状態から第１の駆動信号と第２の駆動信号との位相関係を変化させることで当該変化量に応じた滑らかな速度変化を得ることができる。
【００７０】
請求項４に記載の発明によれば、第１の駆動信号及び第２の駆動信号の周波数が電気機械変換素子の最も低い機械共振周波数ｆｒに基づいて設定されるため、例えば、第１の駆動信号の駆動周波数ｆｄ１と第２の駆動信号の駆動周波数ｆｄ２とをｆｄ１＜ｆｒ＜ｆｄ２となるように設定することや、ｆｒ＜ｆｄ１＜ｆｄ２となるように設定することや、ｆｄ１＜ｆｄ２＜ｆｒとなるように設定することができ、設定の自由度が増すこととなる。
【００７１】
請求項５に記載の発明によれば、第１の駆動信号と第２の駆動信号とが互いに周波数が同じであり、第１の駆動信号のデューティ比Ｄ１と第２の駆動信号のデューティ比Ｄ２とが、Ｄ１＋Ｄ２＝１の関係にない場合にも適用することができ、設定の自由度が増すこととなる。
【図面の簡単な説明】
【図１】 本発明の一実施形態に係るインパクト型圧電アクチュエータからなる駆動装置の基本構成を概略的に示すブロック図である。
【図２】 駆動部の構成例を示す斜視図である。
【図３】 駆動回路の構成例を示す図である。
【図４】 駆動回路の原理的な動作を説明するための駆動電圧のパルス波形等を示す図である。
【図５】 駆動装置を構成する支持部材及び駆動部材が固着された状態での圧電素子の機械共振特性を示す特性図である。
【図６】 本発明に係る駆動装置の振幅伝達特性及び位相伝達特性を示す特性図である。
【図７】 本発明に係る駆動装置に適用される駆動回路の具体的な動作を説明するための図である。
【図８】 駆動回路の別の構成例を示す図である。
【図９】 別の構成例である駆動回路の原理的な動作を説明するための駆動電圧のパルス波形等を示す図である。
【図１０】 従来例の駆動装置の概略構成を示す図である。
【図１１】 図１０に示す駆動装置の駆動回路の構成例を示すブロック図である。
【図１２】 図１１に示す駆動回路の出力波形を示す図である。
【図１３】 従来例の駆動装置の振幅伝達特性及び位相伝達特性を示す特性図である。
【符号の説明】
１４，１４' 駆動回路
２６ 圧電素子（電気機械変換素子）
１４１ 第１のスイッチング回路
１４２ 第２のスイッチング回路
１４３ 第３のスイッチング回路
１４４ 第４のスイッチング回路
１４５，１４５' 第１の波形発振器
１４６，１４６' 第２の波形発振器
１５１，１５１' 第１の駆動回路（第１の駆動手段）
１５２，１５２' 第２の駆動回路（第２の駆動手段）
Ｔｒ１ 第１のスイッチ素子
Ｔｒ２ 第２のスイッチ素子
Ｔｒ３ 第３のスイッチ素子
Ｔｒ４ 第４のスイッチ素子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving device, and more particularly to a driving device suitable for driving an XY moving stage, a camera photographing lens, a projection lens of an overhead projector, a binocular lens, and the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an impact-type piezoelectric actuator constructed by coupling an engagement member to which a photographic lens or the like is attached to a rod-like drive member so as to have a predetermined frictional force and fixing a piezoelectric element to one end of the drive member A driving device is known. For example, FIG. 10 is a diagram illustrating a schematic configuration of a driving device for adjusting the position of the photographing lens of the camera.
[0003]
10 includes a piezoelectric element 101 that is an electromechanical conversion element, a rod-like driving member 102 that is driven by the piezoelectric element 101, and an engagement member 103 that is coupled to the driving member 102 with a predetermined frictional force. And a drive circuit 104 that applies a drive voltage to the piezoelectric element 101.
[0004]
The piezoelectric element 101 expands and contracts according to the drive voltage applied from the drive circuit 104, and one end in the expansion / contraction direction is fixed to the support member 105, and the other end is in the axial direction of the drive member 102. One is fixed to one end. The engaging member 103 has a photographing lens L, which is a driving object, fixed to a predetermined location, and is movable along the axial direction on the driving member 102.
[0005]
As shown in FIG. 11, the drive circuit 104 includes a waveform generator 107 and a power amplifier 108. The waveform generator 107 generates a drive voltage composed of, for example, a rectangular wave of 0 to 5V and inputs it to the power amplifier 108. The power amplifier 108 converts the drive voltage supplied from the waveform generator 107 into a rectangle of 0 to 10V, for example. Amplified to a drive voltage consisting of waves and applied to the piezoelectric element 101.
[0006]
In the drive device 100 configured as described above, a drive voltage having a rectangular waveform as shown in FIG. 12A in which the duty ratio D (D = B / A) is 0.25, for example, is applied from the drive circuit 104 to the piezoelectric element. 101 is applied. This driving method using the driving voltage uses the amplitude transmission characteristic and the phase transmission characteristic due to the mechanical resonance characteristic of the driving member 102 coupled to the piezoelectric element 101 constituting the impact type piezoelectric actuator.
[0007]
FIG. 13A is a diagram illustrating the amplitude transfer characteristic, where the vertical axis represents the amplitude of the drive member 102, and the horizontal axis represents the ratio (fd / fr) of the drive frequency fd to the mechanical resonance frequency fr of the drive member 102. . FIG. 13B is a diagram showing the phase transfer characteristic, where the vertical axis represents the phase, and the horizontal axis represents the ratio (fd / fr) of the drive frequency fd to the mechanical resonance frequency fr of the drive member 102. The frequency fd1 (see FIG. 12 (b)) of the fundamental wave signal included in the drive voltage before and after the lowest mechanical resonance frequency fr1 among the plurality of resonances and the frequency fd2 of the second harmonic (see FIG. 12 (c)). Are set so that fd1 <fr1 <fd2 is satisfied, the mechanical response of the drive shaft to the harmonic signal component of the third harmonic frequency fd3 or higher is lowered. Then, the response of an appropriate mechanical displacement with respect to the fundamental wave signal and the second harmonic signal is obtained using the unimodal characteristic representing the distribution having only one mode of mechanical resonance, and further, the fundamental wave and the second harmonic wave are obtained. The amplitude of the drive voltage, the duty ratio D, the drive frequency fd, the amplitude transfer characteristic, and so that the mechanical displacement of the drive shaft finally becomes a sawtooth waveform as shown in FIG. A desired mechanical load speed of the impact type piezoelectric actuator is obtained by setting the phase transfer characteristic.
[0008]
Further, as an operation of the driving device 100, when a driving voltage is repeatedly applied to the piezoelectric element 101, the engagement member 103 is extended (direction away from the piezoelectric element 101) in the direction of the arrow a due to the expansion and contraction of the piezoelectric element 101. (See FIG. 10). That is, since the driving member 102 is gently extended at the rising portion C where the mechanical displacement is slow as shown in FIG. 12D, the friction coefficient between the engaging member 103 and the driving member 102 increases, and the engaging member 103 moves together with the drive member 102 in the feeding direction, but the drive member 102 is rapidly reduced at the steep falling portion D. Therefore, the friction coefficient between the engagement member 103 and the drive member 102 is reduced, and the drive is performed. Even if the member 102 moves in the return direction (the direction opposite to the arrow a), the engaging member 103 slips on the driving member 102 and stays at substantially the same position. For this reason, when a driving voltage having a waveform as shown in FIG. 12A is repeatedly applied to the piezoelectric element 101, the engaging member 103 moves intermittently in the direction of the arrow a.
[0009]
Further, when the engagement member 103 is moved in the return direction, the rising portion C shown in FIG. 12 (d) becomes a steep rising by changing the duty ratio D of the driving voltage. Try to fall slowly. As a result, at the rising portion C where the mechanical displacement is steep, the driving member 102 is suddenly extended in the feeding direction, so that the friction coefficient between the engaging member 103 and the driving member 102 is reduced, and the engaging member 103 is driven. While slipping on the member 102 and staying at substantially the same position, the driving member 102 is gradually reduced at the slow falling portion D, so that the friction coefficient between the engaging member 103 and the driving member 102 increases, The engaging member 103 moves with the driving member 102 in the return direction (the direction opposite to the arrow a). For this reason, the engaging member 103 moves intermittently in the direction opposite to the arrow a.
[0010]
[Problems to be solved by the invention]
However, in the above conventional drive device, the amplitude transfer characteristic and the phase transfer characteristic are the characteristics achieved by the mechanical design of the impact type piezoelectric actuator, so that it cannot be designed freely with restrictions such as cost reduction and miniaturization. Absent. Further, the amplitude and duty ratio D of the drive signal can be manipulated, and the composite ratio of the amplitude of the fundamental wave and the second harmonic can be changed. However, even if the duty ratio D is changed, the phase is in phase. It is difficult to manipulate the phase relationship because it remains unchanged. For this reason, it is necessary to set the phase relationship in the mechanical design of the impact type piezoelectric actuator. However, in this case as well, it cannot be designed freely due to restrictions such as cost reduction and size reduction.
[0011]
The present invention has been made to solve the above-described problem, and without relying on the phase transfer characteristic of the mechanical resonance characteristic by the drive signal application method that can manipulate the phase relationship in addition to the amplitude and the synthesis ratio. An object of the present invention is to provide a drive device that can obtain an optimum response of mechanical displacement.
[0012]
[Means for Solving the Problems]
The invention according to claim 1 is an electromechanical conversion element that expands and contracts when a drive signal is applied; a support member that is fixed to one end in the expansion and contraction direction of the electromechanical conversion element; The electromechanical conversion includes a drive member fixed to the other end in the expansion / contraction direction, an engagement member engaged with the drive member with a predetermined frictional force, and a drive circuit for driving the electromechanical conversion element. In the drive device that relatively moves the support member and the engagement member by expanding and contracting elements at different speeds, the drive circuit includes a first drive unit that generates a first drive signal having a predetermined frequency; Second driving means for generating a second driving signal having a predetermined frequency different from that of the first driving signal, and adding the first driving signal and the second driving signal to generate the electric Mechanical conversion element Applying the electro-mechanical conversion element is driven by the ratio between the frequency of the first frequency and the second driving signal of the driving signal and said integral ratio der Rukoto.
[0013]
According to this configuration, the first driving signal having the predetermined frequency generated by the first driving unit and the second driving unit having the predetermined frequency different from the first driving signal generated by the second driving unit. The electromechanical conversion element is driven by adding the drive signal and applying it to the electromechanical conversion element. For this reason, by operating the phase relationship between the first drive signal and the second drive signal, a drive capable of obtaining an optimum mechanical displacement response without depending on the phase transfer characteristic of the mechanical resonance characteristic of the electromechanical transducer. A device is realized.
[0015]
The ratio between the frequency of the frequency of the first drive signal a second drive signal for an integer ratio, the ratio between the frequency of the frequency of the first drive signal the second driving signal is an integer ratio It can be applied to a driving device.
[0016]
The invention according to claim 2 is characterized in that the integer ratio is 1: 2. According to this configuration, the present invention can be applied to a drive device in which the ratio of the frequency of the first drive signal and the frequency of the second drive signal is 1: 2.
[0017]
The invention according to claim 3 is characterized in that the drive speed in the expansion / contraction direction of the electromechanical transducer is changed by changing the phase relationship between the first drive signal and the second drive signal. According to this configuration, the drive speed in the expansion / contraction direction of the electromechanical transducer is changed by changing the phase relationship between the first drive signal and the second drive signal. By changing the phase relationship between the first drive signal and the second drive signal from the state where the displacement is obtained, a smooth speed change corresponding to the change amount can be obtained.
[0018]
According to a fourth aspect of the present invention, the frequencies of the first drive signal and the second drive signal are set based on the lowest mechanical resonance frequency fr of the electromechanical transducer. According to this configuration, since the frequencies of the first drive signal and the second drive signal are set based on the lowest mechanical resonance frequency fr of the electromechanical transducer, for example, the drive frequency fd1 of the first drive signal And the drive frequency fd2 of the second drive signal are set to satisfy fd1 <fr <fd2, set to satisfy fr <fd1 <fd2, or set to satisfy fd1 <fd2 <fr. This increases the degree of freedom of setting.
[0019]
According to the fifth aspect of the present invention, the first drive signal and the second drive signal have the same frequency, and the duty ratio D1 of the first drive signal and the duty ratio D2 of the second drive signal are , D1 + D2 = 1. According to this configuration, the first drive signal and the second drive signal have the same frequency, and the duty ratio D1 of the first drive signal and the duty ratio D2 of the second drive signal are D1 + D2 = The present invention can be applied even when the relationship is not 1, and the degree of freedom in setting increases.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram schematically showing a basic configuration of a drive device including an impact type piezoelectric actuator according to an embodiment of the present invention. In this figure, the drive device 10 includes a drive unit 12, a drive circuit 14 that drives the drive unit 12, a member sensor 16 that detects the position of an engagement member 30 attached to the drive unit 12, and the drive unit 12. A proximal end sensor 18 disposed at the proximal end of the drive unit 12, a distal end sensor 20 disposed at the distal end of the drive unit 12, and a control unit 22 for controlling the overall operation.
[0021]
FIG. 2 is a perspective view illustrating a configuration example of the drive unit 12. In this figure, the drive unit 12 has an element-fixed structure, and includes a support member 24, a piezoelectric element 26 that is an electromechanical conversion element, a drive member 28, and an engagement member 30.
[0022]
The support member 24 holds the piezoelectric element 26 and the drive member 28, and is formed by piercing the inside leaving the both end portions 241 and 242 in the axial direction of the cylindrical body and the partition wall 243 positioned substantially at the center. The first storage space 244 and the second storage space 245 are provided. In the first accommodation space 244, the piezoelectric element 26 is accommodated in a state in which the expansion / contraction direction, which is the polarization direction, coincides with the axial direction of the support member 24. Further, the drive member 28 and a part of the engagement member 30 are accommodated in the second accommodation space 245.
[0023]
The piezoelectric element 26 is formed by, for example, laminating a plurality of piezoelectric substrates having a predetermined thickness via electrodes between each piezoelectric substrate, and the longitudinal direction which is the expansion / contraction direction (lamination direction) thereof. One end surface is fixed to one end portion 241 side end surface of the first accommodation space 244. The other end 242 of the support member 24 and the partition wall 243 are provided with a round hole at the center position, and a rod-shaped drive member 28 having a circular cross section passes through both the round holes in the second storage space 245. It is accommodated so as to be movable along the axial direction.
[0024]
The end of the driving member 28 protruding into the first housing space 244 is fixed to the other end surface of the piezoelectric element 26, and the end of the driving member 28 protruding outside the second housing space 245 is predetermined by the leaf spring 32. Is biased toward the piezoelectric element 26 by the spring pressure. The urging of the drive member 28 by the leaf spring 32 is to stabilize the axial displacement of the drive member 28 based on the expansion / contraction operation of the piezoelectric element 26.
[0025]
The engaging member 30 includes a base portion 302 having mounting portions 301 on both sides in the axial direction of the driving member 28, and a sandwiching member 303 mounted between the mounting portions 301. The base portion 302 is the driving member 28. The engaging member 30 is pressed downward by the leaf springs 304 attached to the two attachment portions 301 and is brought into contact with the driving member 28, whereby the engaging member 30 is driven with a predetermined frictional force. When the driving force larger than the frictional force is applied to the engaging member 30, the engaging member 30 can move along the axial direction of the driving member 28. The engaging member 30 is attached with a photographic lens L (FIG. 1) that is a driving object.
[0026]
FIG. 3 is a diagram illustrating a configuration example of the drive circuit 14. The driving circuit 14 shown in FIG. 3 includes a bridge circuit, and includes a first driving circuit 151 that is a first driving unit and a second driving circuit 152 that is a second driving unit. The first drive circuit 151 includes a first switch circuit 141 including a switch element Tr1 which is an enhancement-type MOS (Metal Oxide Semiconductor) FET (Field Effect Transistor), and a switch element Tr2 which is also an enhancement-type MOS FET. A second switch circuit 142, a DC power supply voltage V1 from a drive power supply (not shown), and a waveform generator 145. The second drive circuit 152 includes a third switch circuit 143 composed of a switch element Tr3 that is an enhancement type MOS FET, a fourth switch circuit 144 composed of a switch element Tr4 that is also an enhancement type MOS FET, It comprises a DC power supply voltage V2 from the drive power supply and a waveform generator 146.
[0027]
In the first drive circuit 151, a first switch circuit 141 and a second switch circuit are connected between a DC power supply voltage V1 from a drive power supply (not shown) and supplied to the sort electrode of the switch element Tr1 and grounded. 142 series circuits are connected. The second drive circuit 152 is supplied with a DC power supply voltage V2 from a drive power supply (not shown) to the sort electrode of the switch element Tr3, and is connected to the ground connection point a. The third switch circuit 143 and the fourth switch circuit 144 series circuits are connected.
[0028]
The switch element Tr1 constituting the first switch circuit 141 and the switch element Tr3 constituting the third switch circuit 143 are P-channel FETs, and constitute the switch element Tr2 and the fourth switch circuit 144 constituting the second switch circuit 142. The switch element Tr4 is an N-channel FET. The switch elements Tr1 and Tr3 that are P-channel FETs are turned on when the drive control signal is low level, and the switch elements Tr2 and Tr4 that are N-channel FETs are turned on when the drive control signal is high level. The piezoelectric element 26 is connected between the connection point c of the first switch circuit 141 and the second switch circuit 142 and the connection point d of the third switch circuit 143 and the fourth switch circuit 144 to form a bridge circuit. The
[0029]
The first drive signal Sd1 from the waveform generator 145 is applied to the gate electrodes of the switch element Tr1 and the switch element Tr2, and the second drive signal Sd2 from the waveform generator 146 is the gate electrode of the switch element Tr3 and the switch element Tr4. To be applied. The first drive signal Sd1 and the second drive signal Sd2 are drive signals whose frequency ratio is an integer ratio, and in the present embodiment, this integer ratio is 1: 2. The first drive signal Sd1 has a rectangular waveform with an amplitude of V3 and a duty ratio D1 (D1 = B1 / A1) of 0.5, and the second drive signal Sd2 has an amplitude of V4 and a duty ratio D2 (D2 = B2 / A2) is a rectangular waveform of 0.5. Note that the duty ratio D1 of the first drive signal Sd1 and the duty ratio D2 of the second drive signal Sd2 are in a relationship of D1 + D2 = 1.
[0030]
The DC power supply voltages V1 and V2 are values that determine the magnitude of the rectangular wave drive voltage applied to the piezoelectric element 26, and the DC power supply voltage V1 is the first drive voltage Vd1 corresponding to the first drive signal Sd1, and the DC The power supply voltage V2 becomes the second drive voltage Vd2 corresponding to the second drive signal Sd2. The first drive voltage Vd1 and the second drive voltage Vd2 are voltages opposite in phase to the first drive signal Sd1 and the second drive signal Sd2, and are applied to the piezoelectric element 26, respectively.
[0031]
Note that the power supply system may be unified by setting the DC power supply voltages V1 and V2 to V1 = V2. In this case, the circuit configuration is simplified, and the drive circuit can be further reduced in cost and size.
[0032]
Returning to FIG. 1, the member sensor 16 is disposed within a movable range of the engaging member 30 and is configured by an appropriate sensor such as an MRE (Magneto Resistive Effect) element or a PSD (Position Sensitive Device) element. Has been. In addition, the proximal sensor 18 and the distal sensor 20 are configured by appropriate sensors such as a photo interrupter. Thus, the position of the engaging member 30 is detected by the member sensor 16 so that the movement of the engaging member 30 to a predetermined position can be controlled. On the other hand, the position of the engaging member 30 is determined by the proximal sensor 18 and the distal sensor. The further movement of the engaging member 30 is prohibited by detecting by 20.
[0033]
The control unit 22 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read Only Memory) that stores processing programs and data, and a RAM (Random Access Memory) that temporarily stores data. The drive circuit 14 is driven and controlled based on signals input from the member sensor 16, the proximal sensor 18, and the distal sensor 20. That is, the control unit 22 includes the first drive signal Sd1 generated in the first drive circuit 151, the DC power supply voltage V1 from the drive power supply, and the second drive signal Sd2 generated in the second drive circuit 152. And the DC power supply voltage V2 from the drive power supply are controlled.
[0034]
Next, the principle operation of the drive circuit 14 will be described with reference to FIGS. FIG. 4 is a diagram showing a pulse waveform of the drive voltage for explaining the principle operation of the drive circuit 14. FIG. 4A shows a rectangular wave representing the first drive signal Sd1 output from the waveform generator 145, the amplitude of the rectangular wave is V3, and the duty ratio D1 is 0.5. FIG. 4D shows a rectangular wave representing the second drive signal Sd2 output from the waveform generator 146, the amplitude of the rectangular wave is V4, and the duty ratio D2 is 0.5. The frequency ratio between the first drive signal Sd1 and the second drive signal Sd2 is 1: 2, and the relationship between the duty ratio D1 and the duty ratio D2 is D1 + D2 = 1.
[0035]
4B is a rectangular wave representing the first drive voltage Vd1 applied to the piezoelectric element 26, and FIG. 4E is a rectangle representing the second drive voltage Vd2 applied to the piezoelectric element 26. It is a wave. 4C shows a waveform representing the sine wave voltage Vd1c of the first drive frequency fd1 applied to the piezoelectric element 26, and FIG. 4F shows the waveform of the second drive frequency fd2 applied to the piezoelectric element 26. It is a waveform showing the sine wave voltage Vd2c. FIG. 4G shows a drive voltage Vd corresponding to the difference between the first drive voltage Vd1 and the second drive voltage Vd2. This drive voltage Vd is applied from the electrode A which is one electrode of the piezoelectric element 26 and the electrode B which is the other electrode (see FIG. 3).
[0036]
FIG. 5 is a characteristic diagram showing mechanical resonance characteristics of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 constituting the drive device 10 are fixed. FIG. 5A is a diagram illustrating the amplitude transfer characteristic, where the vertical axis represents the amplitude of the drive member 28, and the horizontal axis represents the ratio (fd / fr) of the drive frequency fd to the mechanical resonance frequency fr of the drive member 28. . FIG. 5B is a diagram showing the phase transfer characteristic, where the vertical axis represents the phase, and the horizontal axis represents the ratio (fd / fr) of the drive frequency fd to the mechanical resonance frequency fr of the drive member 28. Note that the value of Q, which is an amount representing the sharpness of resonance characteristics, is 10 as an effective Q value in a state where a mechanical load is mounted on the driving member.
[0037]
An amplitude having resonance characteristics by setting the drive frequency fd1 and the drive frequency fd2 in the vicinity of the lowest mechanical resonance frequency fr1 of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 are fixed. Utilizing the transfer characteristics, the mechanical displacement response to the harmonic components of the first drive voltage Vd1 and the second drive voltage Vd2 (having odd harmonics each because the duty ratios D1 and D2 are 0.5) is eliminated, A response corresponding to the fundamental wave component is obtained. That is, the sine wave voltage Vd1c having the drive frequency fd1 and the sine wave voltage Vd2c having the drive frequency fd2 are applied to the piezoelectric element 26. Therefore, there are the following three types of setting of the drive frequencies fd1 and fd2 with reference to fr1.
[0038]
fd1 <fd2 <fr1 (1)
fd1 <fr1 <fd2 (2)
fr1 <fd1 <fd2 (3)
[0039]
These settings can only be set to fd1 <fr1 <fd2 (2) in the conventional duty rectangular wave drive in order to achieve both the amplitude transfer characteristic and the phase transfer characteristic of the piezoelectric element 26. However, since the frequencies of the first drive signal Sd1 and the second drive signal Sd2 are set based on the lowest mechanical resonance frequency fr1 of the piezoelectric element 26 that is an electromechanical transducer, for example, the first drive signal Sd1 The drive frequency fd1 of the second drive signal Sd2 and the drive frequency fd2 of the second drive signal Sd2 are set so as to satisfy fd1 <fr1 <fd2 (2), or so that fr1 <fd1 <fd2 (3). It can be set or set so that fd1 <fd2 <fr1 (1), and the degree of freedom of setting increases.
[0040]
Note that the mechanical resonance frequency fr of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 are fixed is obtained by the following equation.
[0041]
[Expression 1]

[0042]
In Equation 1, fro represents the free resonance frequency between the electrodes of the piezoelectric element 26 (mechanical resonance frequency in the direction between the electrodes of the piezoelectric element 26 itself), mp represents the mass of the piezoelectric element 26, and mf represents the mass of the drive member 28. ing. The mass of the support member 24 is related to the mechanical resonance frequency fr of the piezoelectric element 26 in the resonance system, but the mass of the support member 24 is larger than the sum of the masses mp and mf of the piezoelectric element 26 and the drive member 28. Therefore, it is not necessary to consider it as a calculation parameter because the influence on the mechanical resonance frequency fr is small. Further, the engaging member 30 does not have to be considered as a substantially resonant element because it slips with respect to the driving member 28 at the time of resonance of the piezoelectric element 26, and is therefore included as the calculation parameter of the above equation (1). Absent.
[0043]
FIG. 6A is a characteristic diagram showing the amplitude transmission characteristic in the case of fd1 <fr1 <fd2 (2) in FIGS. 5A and 5B, and the vertical axis represents the amplitude of the drive member 28. FIG. The horizontal axis represents the ratio of the drive frequency fd to the mechanical resonance frequency fr of the drive member 28 (fd / fr). FIG. 6B is a characteristic diagram showing the phase transfer characteristic in the case of fd1 <fr1 <fd2 (2) in FIGS. 5A and 5B, the vertical axis represents the phase, and the horizontal axis represents The ratio (fd / fr) of the drive frequency fd with respect to the mechanical resonance frequency fr of the drive member 28 is represented. FIG. 7 is a diagram for explaining a specific operation of the drive circuit 14 applied to the drive device 10 according to the present invention.
[0044]
For example, the drive frequency fd1 is 0.75 times (fd1 = 0.75 × fr1) the lowest mechanical resonance frequency fr1 of the resonance frequency fr of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 are fixed. Set as follows. For convenience of explanation, it is assumed that the DC power supply voltages V1 and V2 are V1 = V2. That is, the first drive voltage Vd1 and the second drive voltage Vd2 are Vd1 = Vd2. In this case, the first drive voltage Vd1 is a rectangular wave as shown in FIG. 7A, and the second drive voltage Vd2 is a rectangular wave as shown in FIG. 7B. A drive voltage Vd (Vd = Vd1−Vd2) corresponding to the difference between the first drive voltage Vd1 and the second drive voltage Vd2 is applied to both electrodes A and B of the piezoelectric element 26. Due to the amplitude transfer characteristics, the harmonic components of the displacement with respect to the first drive voltage Vd1 and the second drive voltage Vd2 are respectively removed, and the remaining fundamental components of the displacement are each subjected to changes in amplitude and phase. The amplitude change due to the amplitude transfer characteristic is r1: r2 = 2.25: 0.794 as shown in FIG. Further, the phase change due to the phase transfer characteristic is θ1: θ2 = −9.7 °: −173.2 ° as shown in FIG. 6B. The mechanical displacement x of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 are fixed is a combined displacement of the mechanical displacement x1 due to the first sine wave voltage Vd1c and the mechanical displacement x2 due to the second sine wave voltage Vd2c. (X = x1 + x2) (FIG. 7D). The speed v of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 are fixed is a combined speed (v = v1 + v2) of the speed v1 obtained by differentiating the mechanical displacement x1 and the speed v2 obtained by differentiating the mechanical displacement x2. (FIG. 7 (e)).
[0045]
Here, when looking at the waveform of the composite displacement x shown in FIG. 7 (d), a large bulge is generated at the rising portion E, which is not a saw waveform, and the support member 24 and the drive member 28 are The desired mechanical displacement x of the piezoelectric element 26 in the fixed state cannot be obtained. Further, when the velocities v1 and v2 of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 are fixed are substantially in phase, the waveform of the combined speed v has a substantially trapezoidal shape. The waveform of the composite speed v shown is not substantially trapezoidal, and the desired speed of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 are fixed cannot be obtained. Therefore, in order to obtain a desired sawtooth mechanical displacement of the piezoelectric element 26 with the support member 24 and the drive member 28 fixed, the amplitudes of the first sine wave voltage Vd1c and the second sine wave voltage Vd2c can be obtained. It is necessary to manipulate the phase relationship. Since it is difficult to change the characteristic of the mechanical resonance frequency fr1 in this operation, the amplitude operation is performed by changing the DC power supply voltage V1 or V2, and the phase operation is performed using the first drive signal Sd1 and the second drive signal. This is performed by varying the phase relationship of Sd2.
[0046]
Therefore, the DC power supply voltages V1 and V2 are set to, for example, V1: V2 = 1: 0.7, and the phase of the second drive signal Sd2 is advanced by, for example, 65 ° with respect to the phase of the first drive signal Sd1. As a result, a second drive voltage Vd2 ″ as shown in FIG. 7F is obtained. At this time, the mechanical displacement x2 ″ by the second sine wave voltage Vd2 ″ has a waveform shown in FIG. The combined displacement x ″ of the mechanical displacement x1 and the mechanical displacement x2 ″ has a sawtooth waveform as shown in FIG. 7G, and a desired mechanical displacement can be obtained. Further, the machine speed v2 ″ at this time has a waveform shown in FIG. The combined speed v ″ of the machine speed v1 and the machine speed v2 ″ has a substantially trapezoidal waveform as shown in FIG. 7G, and a desired machine speed can be obtained.
[0047]
As described above, the first drive signal Sd1 having a predetermined frequency generated by the first drive circuit 151 and the first drive signal Sd1 having a different frequency from the first drive signal Sd1 generated by the second drive circuit 152 are used. The two drive signals Sd2 are added and applied to the piezoelectric element 26 which is an electromechanical conversion element, so that the piezoelectric element 26 is driven. Therefore, by operating the phase relationship between the first drive signal Sd1 and the second drive signal Sd2, an optimum mechanical displacement response can be obtained without depending on the phase transfer characteristic of the mechanical resonance characteristic of the piezoelectric element 26. A driving device is realized.
[0048]
In addition, since the driving speed in the expansion / contraction direction of the piezoelectric element 26 that is an electromechanical conversion element is changed by changing the phase relationship between the first driving signal Sd1 and the second driving signal Sd2, for example, an optimal sawtooth waveform By changing the phase relationship between the first drive signal Sd1 and the second drive signal Sd2 from the state where the mechanical displacement of the state is obtained, a smooth speed change according to the change amount can be obtained.
[0049]
FIG. 8 is a diagram illustrating another configuration example of the drive circuit 14. In this figure, the drive circuit 14 'is constituted by a bridge circuit, and is constituted by a first drive circuit 151' and a second drive circuit 152 '. The first drive circuit 151 ′ includes a first switch circuit 141 composed of a switch element Tr1 which is an enhancement-type MOS (Metal Oxide Semiconductor) FET (Field Effect Transistor), and a switch element Tr2 which is also an enhancement-type MOS FET. And a second power supply voltage V1 from a drive power supply (not shown), a waveform generator 145 ′, a capacitor C1, an input resistance R1, and a feedback resistance R2. The second drive circuit 152 ′ includes a third switch circuit 143 composed of a switch element Tr3 that is an enhancement type MOS FET, a fourth switch circuit 144 composed of a switch element Tr4 that is also an enhancement type MOS FET, DC power source voltage V2 from the driving power source, waveform generator 146 ', capacitor C2, input resistor R3, and feedback resistor R4. As described above, by arranging the input resistor R1 and the feedback resistor R2 in the first drive circuit 151 ′, the gain G1 becomes an amplifier circuit with G1 = R2 / R1, and similarly, the second drive circuit 152 ′ has the gain G1. By arranging the input resistor R3 and the feedback resistor R4, an amplifier circuit in which the gain G2 is G2 = R4 / R3 is obtained. However, it is assumed that the gains G1 and G2 are sufficiently large.
[0050]
The first drive circuit 151 ′ includes a first switch circuit 141 and a second switch between a connection point a to which a DC power supply voltage V1 from a drive power supply (not shown) is supplied to the sort electrode of the switch element Tr1 and is grounded. A series circuit of the circuit 142 is connected. In the second drive circuit 152 ′, the third switch circuit 143 and the fourth switch are connected between the DC power supply voltage V2 from the drive power supply (not shown) and the ground connection point a to the sort electrode of the switch element Tr3. A series circuit of the circuit 144 is connected.
[0051]
The switch element Tr1 constituting the first switch circuit 141 and the switch element Tr3 constituting the third switch circuit 143 are P-channel FETs, and constitute the switch element Tr2 and the fourth switch circuit 144 constituting the second switch circuit 142. The switch element Tr4 is an N-channel FET. The switch elements Tr1 and Tr3 that are P-channel FETs are turned on when the drive control signal is low level, and the switch elements Tr2 and Tr4 that are N-channel FETs are turned on when the drive control signal is high level. The piezoelectric element 26 is connected between the connection point c of the first switch circuit 141 and the second switch circuit 142 and the connection point d of the third switch circuit 143 and the fourth switch circuit 144 to form a bridge circuit. The
[0052]
The first drive signal Sd1 ′ is applied to the input resistor R1 through the DC blocking capacitor C1, and the first drive voltage Vd1 ′ is a voltage obtained by multiplying the first drive signal Sd1 ′ by a gain G1. Similarly, the second drive signal Sd2 ′ is applied to the input resistor R3 through the DC blocking capacitor C2, and the second drive voltage Vd2 ′ becomes a voltage obtained by multiplying the second drive signal Sd2 ′ by a gain G2.
[0053]
FIG. 9 is a diagram showing a pulse waveform of the drive voltage for explaining the principle operation of the drive circuit 14 ′. FIG. 9A shows a sine wave representing the first drive signal Sd1 ′ output from the waveform generator 145 ′, and the amplitude of the sine wave is V3. FIG. 9D shows a sine wave representing the second drive signal Sd2 ′ output from the waveform generator 146 ′, and the amplitude of the sine wave is V4. The frequency ratio between the first drive signal Sd1 ′ and the second drive signal Sd2 ′ is an integer ratio, and in the present embodiment, this integer ratio is 1: 2.
[0054]
FIG. 9B shows a sine wave representing the first drive voltage Vd1 ′ applied to the piezoelectric element 26, and FIG. 9E shows the second drive voltage Vd2 ′ applied to the piezoelectric element 26. It is a sine wave that represents. FIG. 9C shows a waveform representing the sine wave voltage Vd1c ′ of the drive frequency fd1 ′ applied to the piezoelectric element 26, and FIG. 9F shows the sine wave voltage of the drive frequency fd2 ′ applied to the piezoelectric element 26. It is a waveform showing Vd2c '. FIG. 9G shows a drive voltage Vd ′ corresponding to the difference between the first drive voltage Vd1 ′ and the second drive voltage Vd2 ′. The drive voltage Vd ′ is applied from the electrode A that is one electrode of the piezoelectric element 26 and the electrode B that is the other electrode.
[0055]
As described above, by using the first drive signal Sd1 ′ and the second drive signal Sd2 ′ as sine waves, there is an advantage that it is not necessary to pay attention to harmonic removal due to the amplitude transfer characteristic.
[0056]
Further, the first drive signal Sd1 ′ that is a sine wave of a predetermined frequency generated by the first drive circuit 151 ′ and the first drive signal Sd1 ′ generated by the second drive circuit 152 ′ The piezoelectric element 26 is driven by adding the second drive signal Sd2 ′, which is a sine wave having a different predetermined frequency, and applying it to the piezoelectric element 26 that is an electromechanical conversion element. Therefore, by operating the phase relationship between the first drive signal Sd1 ′ and the second drive signal Sd2 ′, an optimum mechanical displacement response can be obtained without depending on the phase transfer characteristic of the mechanical resonance characteristic of the piezoelectric element 26. The resulting drive device is realized.
[0057]
In the present embodiment, a rectangular wave or a sine wave is used as both the first drive signal and the second drive signal. However, the present invention is not particularly limited to this, and either one is a rectangular wave and the other is the other. May be a sine wave. In this case, the drive circuit 14 includes a first drive circuit 151 that generates a rectangular wave and a second drive circuit 152 ′ that generates a sine wave, or a first drive circuit 151 that generates a sine wave. 'And a second drive circuit 152 for generating a rectangular wave. As described above, the waveforms generated as the first drive signal and the second drive signal are both rectangular waves, both sine waves, or either one is a rectangular wave and the other is a sine wave. A drive signal corresponding to the waveforms of the drive signal and the second drive signal can be obtained.
[0058]
In this embodiment, one of the duty ratio D1 of the first drive voltage Vd1 or the duty ratio D2 of the second drive voltage Vd2, or the duty ratio D1 of the first drive voltage Vd1 and the second drive. A rectangular wave having a relationship of D1 + D2 = 1 is used in which both the duty ratio D2 of the voltage Vd2 is 0.5, but the present invention is not particularly limited to this, and the duty ratios D1 and D2 are other than 0.5. , A rectangular wave not having a relationship of D1 + D2 = 1 may be used. In this case, for example, if the driving frequency setting method having the relationship fd1 <fd2 <fr1 (1) shown in FIG. 5A is selected, the third harmonic of the first driving voltage Vd1 is the mechanical resonance frequency. The possibility of being in the vicinity of fr1 increases. Therefore, there is a possibility that the response of the mechanical displacement to the third harmonic of the drive frequency of the piezoelectric element 26 in a state where the support member 24 and the drive member 28 are fixed due to the resonance characteristics may be adversely affected (not a saw waveform). Therefore, the duty ratio D2 of the second drive voltage Vd2 remains 0.5, and the first drive is performed by using a rectangular wave voltage with the duty ratio D1 of 0.33 or 0.67 as the first drive voltage Vd1. The voltage Vd1 does not contain the third harmonic component, and the above problem is solved. Thus, the first drive signal Sd1 and the second drive signal Sd2 have the same frequency, and the duty ratio D1 of the first drive signal Sd1 and the duty ratio D2 of the second drive signal Sd2 are: The present invention can also be applied to cases where there is no relationship of D1 + D2 = 1, and the degree of freedom of setting increases.
[0059]
Further, when changing or reversing the mechanical load speed of the piezoelectric element of the drive device according to the present invention, the first drive signal is obtained from the state of obtaining the sawtooth waveform of the mechanical displacement shown in FIG. By changing the phase relationship between Sd1 and the second drive signal Sd2, the mechanical displacement of the sawtooth waveform deviates from the optimum state in accordance with the amount of change, so the speed gradually decreases. Further, the amount of change is further increased to stop, and finally an inverted saw waveform is obtained, so that a smooth speed change according to the amount of change can be obtained. That is, the speed control of the mechanical load of the driving device can be performed by the phase difference between the first driving signal Sd1 and the second driving signal Sd2.
[0060]
Further, according to the driving voltage Vd shown in FIG. 4G, the piezoelectric element 26 is charged and discharged three times for one cycle. At the time of this discharge, there is a period in which the voltage once becomes 0 volt in principle (E1, E2, E3 in FIG. 4 (g)). This is a short-circuit discharge operation of the piezoelectric element 26 by the transistors (switch elements Td1, Tr2, Tr3, Tr4) of the drive circuit 14. In the conventional duty rectangular wave drive, there is one charge / discharge for one cycle of the drive voltage, and at the time of discharge, a discharge operation is performed through a DC power supply instead of a short-circuit discharge operation. The power consumption in the drive power supply is added, and as a result, the power consumption during driving is increased. The power consumption P1 in the conventional duty rectangular wave drive is expressed by the following equation (1).
[0061]
P1 = C × (2V) ² × fd = 4 × C × V ² × fd (1)
However, the power consumption in the conventional duty rectangular wave drive is P1, the capacitance of the piezoelectric element is C, the DC power supply voltage is V, and the drive frequency is fd.
[0062]
However, in the drive circuit according to the present invention, the power consumption P2 is expressed by the following equation (2).
P2 = 3 × C × V ² × fd (2)
[0063]
Thus, the power consumption P2 of the drive circuit according to the present invention is 0.75 times the power consumption P1 of the conventional drive circuit, and the power consumption is improved.
[0064]
Although the present embodiment has been described with respect to the driving device related to the photographing lens of the camera, the present invention is not particularly limited thereto, and the driving device is suitable for driving the XY moving stage, the projection lens of the overhead projector, the lens of the binoculars, and the like. It is also applicable to.
[0065]
【The invention's effect】
According to the first aspect of the present invention, the first driving signal having the predetermined frequency generated by the first driving unit and the first driving signal generated by the second driving unit are different from each other. The electromechanical conversion element is driven by adding the second drive signal having the frequency and applying it to the electromechanical conversion element. For this reason, an optimum mechanical displacement response can be obtained by manipulating the phase relationship between the first drive signal and the second drive signal without depending on the phase transfer characteristic of the mechanical resonance characteristic of the electromechanical transducer. it can.
[0067]
Further , the present invention can be applied to a drive device in which the ratio of the frequency of the first drive signal and the frequency of the second drive signal is an integer ratio.
[0068]
According to the second aspect of the present invention, the present invention can be applied to a drive device in which the ratio of the frequency of the first drive signal and the frequency of the second drive signal is 1: 2.
[0069]
According to the third aspect of the invention, the drive speed in the expansion / contraction direction of the electromechanical transducer is changed by changing the phase relationship between the first drive signal and the second drive signal. By changing the phase relationship between the first drive signal and the second drive signal from the state in which the optimum mechanical displacement is obtained, a smooth speed change corresponding to the change amount can be obtained.
[0070]
According to the invention described in claim 4 , since the frequencies of the first drive signal and the second drive signal are set based on the lowest mechanical resonance frequency fr of the electromechanical transducer, for example, the first drive signal The drive frequency fd1 of the signal and the drive frequency fd2 of the second drive signal are set so as to satisfy fd1 <fr <fd2, or set so that fr <fd1 <fd2, or fd1 <fd2 <fr. The degree of freedom of setting will increase.
[0071]
According to the fifth aspect of the present invention, the first drive signal and the second drive signal have the same frequency, and the duty ratio D1 of the first drive signal and the duty ratio D2 of the second drive signal are the same. Can be applied even when the relationship is not D1 + D2 = 1, and the degree of freedom of setting increases.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing a basic configuration of a drive device including an impact type piezoelectric actuator according to an embodiment of the present invention.
FIG. 2 is a perspective view illustrating a configuration example of a drive unit.
FIG. 3 is a diagram illustrating a configuration example of a drive circuit.
FIG. 4 is a diagram showing a pulse waveform of a drive voltage for explaining the principle operation of the drive circuit.
FIG. 5 is a characteristic diagram showing mechanical resonance characteristics of the piezoelectric element in a state where the supporting member and the driving member constituting the driving device are fixed.
FIG. 6 is a characteristic diagram showing an amplitude transfer characteristic and a phase transfer characteristic of the drive device according to the present invention.
FIG. 7 is a diagram for explaining a specific operation of a drive circuit applied to the drive device according to the present invention.
FIG. 8 is a diagram showing another configuration example of the drive circuit.
FIG. 9 is a diagram showing a drive voltage pulse waveform and the like for explaining a principle operation of a drive circuit as another configuration example;
FIG. 10 is a diagram showing a schematic configuration of a conventional drive device.
11 is a block diagram showing a configuration example of a drive circuit of the drive device shown in FIG.
12 is a diagram showing an output waveform of the drive circuit shown in FIG.
FIG. 13 is a characteristic diagram showing an amplitude transmission characteristic and a phase transmission characteristic of a conventional driving device.
[Explanation of symbols]
14, 14 'drive circuit 26 piezoelectric element (electromechanical transducer)
141 First switching circuit 142 Second switching circuit 143 Third switching circuit 144 Fourth switching circuits 145 and 145 ′ First waveform oscillators 146 and 146 ′ Second waveform oscillators 151 and 151 ′ First drive Circuit (first driving means)
152, 152 ′ second drive circuit (second drive means)
Tr1 First switch element Tr2 Second switch element Tr3 Third switch element Tr4 Fourth switch element

Claims (5)

An electromechanical conversion element that expands and contracts when a drive signal is applied, a support member that is fixed to one end in the expansion / contraction direction of the electromechanical conversion element, and an other end in the expansion / contraction direction of the electromechanical conversion element A drive member, an engagement member engaged with the drive member with a predetermined frictional force, and a drive circuit for driving the electromechanical conversion element, and extending and contracting the electromechanical conversion element at different speeds. In the drive device that relatively moves the support member and the engagement member,
The driving circuit includes a first driving unit that generates a first driving signal having a predetermined frequency, and a second driving unit that generates a second driving signal having a predetermined frequency different from the first driving signal. And adding the first drive signal and the second drive signal and applying the sum to the electromechanical conversion element to drive the electromechanical conversion element, and the frequency of the first drive signal drive the ratio of the frequency of the second drive signal and said integral ratio der Rukoto. The integral ratio of 1: driving apparatus according to claim 1, characterized in that the 2. 3. The driving apparatus according to claim 1, wherein the driving speed in the expansion / contraction direction of the electromechanical transducer is changed by changing a phase relationship between the first driving signal and the second driving signal. The drive device according to any one of claims 1 to 3 , wherein the frequencies of the first drive signal and the second drive signal are set based on the lowest mechanical resonance frequency fr of the electromechanical transducer. The first drive signal and the second drive signal have the same frequency, and the duty ratio D1 of the first drive signal and the duty ratio D2 of the second drive signal are not in a relationship of D1 + D2 = 1. drive device according to any one of claims 1 to 4, characterized in.

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