JP4892661B2 - Ultrasonic motor vibrator - Google Patents
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Description
本発明は、圧電素子を用いて構成する超音波モータ用振動子に関する。 The present invention relates to a vibrator for an ultrasonic motor configured using a piezoelectric element.
近年、電子・情報産業の急速な発展に伴い、精密部品の更なる微細化、高集積化が求められており、ナノオーダー（１０-9ｍオーダー）での検査や加工に対応する超精密位置決め装置が必要となっている。また、医療やバイオ研究においてタンパク質や細胞の制御による応用技術開発が進み、より微細な領域への位置決めが可能な顕微鏡用ステージに対するニーズが非常に強くなっている。更に近年では高精度化への要求と併せて、検査・加工・測定の対象物が小さくなるに伴い、位置決め装置やその駆動源の小型化・軽量化も求められるようになってきた。 In recent years, with the rapid development of the electronics and information industry, there has been a demand for further miniaturization and higher integration of precision parts, and ultra-precision positioning for nano-order (10 -9 m order) inspection and processing. A device is needed. In addition, the development of applied technology by controlling proteins and cells in medical and bio research has advanced, and the need for a microscope stage that can be positioned in a finer area has become very strong. Furthermore, in recent years, along with the demand for higher accuracy, as the objects to be inspected / processed / measured have become smaller, it has become necessary to reduce the size and weight of the positioning device and its drive source.
従来、位置決め装置の駆動源としては電磁モータが用いられてきた。しかし、電磁モータによる位置決め装置では、電磁モータが持つ種々の間題点に合わせて、減速装置（ギヤ）やボールねじが必要となる等の構造的な間題点も多く、ナノレベルの精度を得ることは困難となっていた。また、占有体積や重量も構造上の制約のために必然的に大きなものになる。電磁モータ方式の位置決め装置の場合、比較的高精度と言われているものでも、位置決め精度は１μｍ（１．０×１０-6ｍ）が限界となっており、マーケット・ニーズであるナノオーダーに比べると１０００倍も粗動であるといえる。つまり、電磁モータ方式の位置決め装置でナノオーダーが達成できる可能性は非常に低いと予想される。 Conventionally, an electromagnetic motor has been used as a driving source of the positioning device. However, the positioning device using an electromagnetic motor has many structural issues such as the need for a speed reducer (gear) and a ball screw in accordance with the various issues of the electromagnetic motor. It was difficult to get. Also, the occupied volume and weight are inevitably large due to structural limitations. In the case of an electromagnetic motor type positioning device, even though it is said to be relatively high accuracy, the positioning accuracy is limited to 1 μm (1.0 × 10 −6 m), which is in the nano-order that is a market need It can be said that it is 1000 times as coarse as compared. That is, it is expected that the possibility of achieving nano-order with an electromagnetic motor type positioning device is very low.
そこで、電磁モータ方式の位置決め装置に代わる新しい位置決め装置として超音波モータを駆動源とする位置決め装置が期待され始めている。この超音波モータ方式の位置決め装置は、超音波振動をそのまま摩擦摺動運動に変換するという動作原理を利用したものであり、減速装置やボールネジを必要とせず、また小型軽量、応答性が高い、作動音がない、停止時の保持力が大きい等の優れた特性も付与できると期待されている。このように、超音波モータを駆動源とする技術は、非常に高精度な位置決め装置を作る要素技術として注目され、多くのタイプが提案され研究されている。 Therefore, a positioning apparatus using an ultrasonic motor as a drive source is beginning to be expected as a new positioning apparatus that replaces the electromagnetic motor type positioning apparatus. This ultrasonic motor type positioning device utilizes the operating principle of directly converting ultrasonic vibrations into frictional sliding motion, does not require a speed reducer or a ball screw, is small and light, and has high responsiveness. It is expected that excellent characteristics such as no operating noise and a large holding force at the time of stopping can be imparted. As described above, a technique using an ultrasonic motor as a drive source has been attracting attention as an elemental technique for producing a very high-precision positioning device, and many types have been proposed and studied.
一般的な超音波モータの原理を図２に示す。超音波モータは振動子１とスライダ２（移動体）を含み、振動子はその伸縮と屈曲の組み合わせにより、少なくともその一部が楕円運動をする。例えば、図２（Ａ）中のｐ点（振動子の左端面の中心点）は、（ａ）〜（ｄ）の４つの状態を通って同図（Ｂ）に示す軌跡を描く（ｘは振動子の長手方向、ｙは振動子の上下面に垂直な軸）。振動子の楕円運動をしている部分には、通常、固定摺動部材（ステータ）３となる耐磨耗性材料が接着されている。振動子の楕円運動はステータを介してスライダに伝達され、スライダを動かす駆動力となる。図２では、楕円運動の繰り返しにより移動体は図のガイド４に沿って下方へと送られる。この例では直線的に移動体を駆動しているが、移動体を円環状にすれば回転運動を生じることも可能である。
The principle of a general ultrasonic motor is shown in FIG. The ultrasonic motor includes a vibrator 1 and a slider 2 (moving body), and at least a part of the vibrator makes an elliptical motion due to a combination of expansion and contraction. For example, point p (center point of the left end face of the vibrator) in FIG. 2A draws a locus shown in FIG. 2B through four states (a) to (d) (x is The longitudinal direction of the vibrator, y is an axis perpendicular to the upper and lower surfaces of the vibrator). A wear-resistant material to be a fixed sliding member (stator) 3 is usually bonded to the portion of the vibrator that is moving elliptically. The elliptical motion of the vibrator is transmitted to the slider via the stator and becomes a driving force for moving the slider. In FIG. 2, the moving body is sent downward along the
後述するように、振動子は圧電素子で構成できるが、この場合、前述の楕円運動の大きさは圧電素子への入力電圧に依存する。すなわち、図３（図２（Ｂ）に対応する図。但し、図２（Ｂ）のｙ軸は図３では水平方向として示す。）に模式的に示すように、入力電圧が大きければ楕円運動も大きく、従って、スライダの移動速度も大きくなる。一方、入力電圧が小さければ楕円運動も小さく、従って、スライダの移動速度も小さくなる。
例えば、超音波モータを用いてＸＹテーブル等で精密位置決めする場合、目的位置に近づくと移動速度を遅くして、少しずつ近づくという動作が必要となるが、移動速度を遅くするためには入力電圧を小さくする必要がある。
As will be described later, the vibrator can be composed of a piezoelectric element. In this case, the magnitude of the aforementioned elliptical motion depends on the input voltage to the piezoelectric element. That is, as schematically shown in FIG. 3 (the figure corresponding to FIG. 2B, where the y-axis of FIG. 2B is shown as the horizontal direction in FIG. 3), if the input voltage is large, elliptical motion Therefore, the moving speed of the slider is also increased. On the other hand, if the input voltage is small, the elliptical motion is small, and therefore the moving speed of the slider is also small.
For example, in the case of precise positioning using an XY table or the like using an ultrasonic motor, an operation of slowing down the moving speed when approaching the target position and approaching gradually is necessary. Need to be small.
一方、固定摺動部材を介してスライダに駆動力を伝達できるのは両者が接触しているからであり、この目的のため、ステータは、適当な圧力でスライダに押し当てられている。しかし、押し当て加重が強すぎると、ステータがスライダに押し当てられ過ぎるため、互いが一瞬たりとも離れる事ができず、弱い入力電圧では全く動かない（図３の楕円運動の横方向の振幅成分がゼロになることに相当、従来の振動子の場合は同時に縦方向の振幅もゼロになる）。入力電圧を上げていくと、ある電圧（しきい電圧）で突然動き出し、このしきい電圧を超えた領域で楕円運動が起こり始める。 On the other hand, the driving force can be transmitted to the slider via the fixed sliding member because they are in contact with each other. For this purpose, the stator is pressed against the slider with an appropriate pressure. However, if the pressing load is too strong, the stator is pressed against the slider too much, so that they cannot be separated from each other even for a moment, and do not move at all with a weak input voltage (the horizontal amplitude component of the elliptical motion in FIG. 3). Is equivalent to zero, and in the case of the conventional vibrator, the longitudinal amplitude is also zero). When the input voltage is increased, the voltage suddenly starts moving at a certain voltage (threshold voltage), and elliptical motion starts to occur in a region exceeding the threshold voltage.
押し当て力をどれだけ弱くしてもしきい電圧が低くなるだけで、しきい電圧は必ず存在し、ある電圧（しきい電圧）で突然動き出すという挙動を無くすことは難しい。すなわち、電圧−移動速度の関係は、図４に示すように、低電圧領域では電圧一移動速度の特性が比例関係ではない上に非常に急峻な曲線を描いており、僅かな電圧の変動によって移動速度が大幅に変化してしまう（入出力特性の非線形性）。
このように、超音波モータを用いて精密位置決めを使用とする場合、入力電圧を低くする必要があるが、入出力特性の非線形性のため、微動領域では制御が困難になる。
No matter how weak the pressing force is, the threshold voltage is always reduced, and there is always a threshold voltage, and it is difficult to eliminate the behavior of sudden movement at a certain voltage (threshold voltage). That is, as shown in FIG. 4, the voltage-moving speed relationship is such that the characteristics of voltage-moving speed are not proportional in the low voltage region, and a very steep curve is drawn. The moving speed changes significantly (non-linearity of input / output characteristics).
As described above, when precise positioning is used using an ultrasonic motor, it is necessary to lower the input voltage. However, because of the nonlinearity of the input / output characteristics, control becomes difficult in the fine movement region.
従来の超音波モータ用振動子として、例えば、特許文献１、２は、矩形状の積層圧電素子に伸縮振動と屈曲振動の２種類の振動を同時に励振させることにより、振動体の所定の位置に楕円運動を発生させ、この楕円運動を移動体（スライダ）へ伝達することで移動体を回転運動もしくは直線運動させるものが開示されている。また、特許文献３、４には、屈曲２次振動を加振するための圧電素子と、伸縮１次振動を加振するための圧電素子とを個別にそれぞれ積層させ、振動子に楕円運動を発生させるものが開示されている。
しかし、従来の超音波モータ用振動子は、入出力特性の非線形性を解消したものではなく、このため、微動領域での振動子の制御性が悪く、精密な位置決めに用いるのは困難であった。
As a conventional ultrasonic motor vibrator, for example,
However, conventional ultrasonic motor vibrators do not eliminate the nonlinearity of the input / output characteristics. For this reason, the controllability of the vibrator in the fine movement region is poor, and it is difficult to use for precise positioning. It was.
また、従来の超音波モータ用振動子の圧電素子は、特許文献５に代表されるように、板状の素子を挟んで、その両面のほぼ全面に電極を形成している。このため、静電容量が大きくなり、必要以上の電流が流れるため、駆動電源に大きな負担がかかるという問題があった。さらに、特許文献３、４では、屈曲２次振動を加振するための圧電素子と、伸縮１次振動を加振するための圧電素子とを個別にそれぞれ積層させるが、振動子全体の半分だけが屈曲振動を、もう半分だけが伸縮振動を加振していることになる。このため、素子全体に占める加振領域の割合が小さくなり、結果的には振動振幅の小さな振動子になってしまうと考えられ、加振効率が悪いという問題があった。
Further, as represented by Patent Document 5, a conventional piezoelectric element of a vibrator for an ultrasonic motor has electrodes formed on almost the entire surface of a plate-like element. For this reason, there is a problem that a large load is applied to the drive power supply because the capacitance increases and more current flows than necessary. Further, in
本発明は、入出力特性の非線形性を緩和し、微動領域での制御性（位置決め精度）の高い超音波モータ用振動子の提供、及び振動効率の高い超音波モータ用振動子の提供を目的とする。 An object of the present invention is to provide a vibrator for an ultrasonic motor with high controllability (positioning accuracy) in a fine movement region, and to provide a vibrator for an ultrasonic motor with high vibration efficiency. And
本発明者らは、上記目的を達成するために鋭意検討した結果、圧電素子において屈曲振動（好ましくは、屈曲２次振動）と伸縮振動（好ましくは、伸縮１次振動）を独立して励振させることで、振動子の制御性が大幅に向上し、また各々の振動を励振させるための分極領域を適切な位置および大きさに最適化することにより振動効率が高まることを見出し、本発明を完成するに至った。
すなわち、本発明は以下の超音波モータ用振動子を提供するものである。
As a result of intensive studies to achieve the above object, the present inventors independently excite bending vibration (preferably bending secondary vibration) and stretching vibration (preferably stretching primary vibration) in the piezoelectric element. As a result, it was found that the controllability of the vibrator was greatly improved, and that the vibration efficiency was improved by optimizing the polarization region for exciting each vibration to an appropriate position and size, and the present invention was completed. It came to do.
That is, the present invention provides the following ultrasonic motor vibrators.
１．圧電素子に、屈曲振動と伸縮振動をそれぞれ独立して励振する分極領域をもち、当該分極領域に電圧信号を印加するための電極を設けたことを特徴とする超音波モータ用振動子。
２．圧電素子の屈曲振動と伸縮振動を励振する分極領域が、それぞれの振動による圧電素子の歪みが最大になる部位を含む前記１記載の超音波モータ用振動子。
３．屈曲振動が屈曲２次振動、伸縮振動が伸縮１次振動である前記１または２記載の超音波モータ用振動子。
４．圧電素子が矩形板であり、伸縮振動を励起する分極領域が、前記矩形板の対向する長辺及び短辺の中点を含む領域に、矩形板の各辺に平行な辺によって画される矩形または十字型領域であり、当該領域における長辺に平行な辺が、前記矩形板の長辺の長さの１０％以上、９５％以下であり、前記当該領域における矩形板の短辺に平行な辺が、前記矩形板の短辺の長さの１０％以上である前記３に記載の超音波モータ用振動子。
５．圧電素子が矩形板であり、屈曲振動を励起する分極領域が、前記矩形板の短辺から長辺に沿って長辺の長さの１／４だけ中心寄りの領域において、それぞれ設けられる各面２対の電極であり、各々の分極領域の長辺に平行な辺が前記長辺の長さの４０％以下であり、短辺に平行な辺が前記短辺の長さの４０％以下である前記３に記載の超音波モータ用振動子。
６．請求項１〜５のいずれか記載の圧電素子と、外部電極との短絡を目的とする引き出し電極パターンを持つ前記１に記載の電極を積層して構成した積層圧電型超音波モータ用振動子。
1. A transducer for an ultrasonic motor, characterized in that a piezoelectric element has a polarization region for independently exciting bending vibration and stretching vibration, and an electrode for applying a voltage signal to the polarization region is provided.
2. 2. The ultrasonic motor vibrator according to claim 1, wherein the polarization region for exciting the bending vibration and the stretching vibration of the piezoelectric element includes a portion where the distortion of the piezoelectric element due to each vibration is maximized.
3. 3. The ultrasonic motor vibrator according to
4). A rectangular shape in which a piezoelectric element is a rectangular plate, and a polarization region that excites stretching vibration is defined by a side parallel to each side of the rectangular plate in a region including the midpoints of the opposing long side and short side of the rectangular plate Or, it is a cross-shaped region, and the side parallel to the long side of the region is 10% or more and 95% or less of the length of the long side of the rectangular plate, and is parallel to the short side of the rectangular plate in the
5. Each surface provided in a region where the piezoelectric element is a rectangular plate, and the polarization region for exciting the bending vibration is a quarter of the length of the long side along the long side from the short side of the rectangular plate. Two pairs of electrodes, the side parallel to the long side of each polarization region is 40% or less of the length of the long side, and the side parallel to the short side is 40% or less of the length of the
6). 6. A vibrator for a laminated piezoelectric ultrasonic motor comprising a laminate of the electrode according to claim 1 having a lead electrode pattern for short-circuiting the piezoelectric element according to claim 1 and an external electrode.
本発明の超音波モータ用振動子は、従来に比べ制御性、特に微動領域における制御性が大幅に向上するため、精密位置決め装置の駆動源として有用である。さらに、従来よりも高い振動効率の超音波モータ用振動子を得ることができる。 The vibrator for an ultrasonic motor according to the present invention is useful as a driving source for a precision positioning device because controllability, particularly controllability in a fine movement region, is greatly improved as compared with the related art. Furthermore, it is possible to obtain an ultrasonic motor vibrator having a vibration efficiency higher than that of the prior art.
本発明では、圧電素子を用いて構成する超音波モータ用振動子において、１個の素子上に屈曲振動（好ましくは、屈曲２次振動）と伸縮振動（好ましくは、伸縮１次振動）を独立して励振するように電極を設け、その配置を最適にする。なお、屈曲（２次）振動とは、図６（ａ）に模式的に示す横振動（２次では１波長≒振動子の全長）であり、伸縮（１次）振動とは、同図（ｂ）に模式的に示す縦振動（１次では半波長＝振動子の全長））である。
以下本発明を詳細に説明する。
In the present invention, in an ultrasonic motor vibrator configured using a piezoelectric element, bending vibration (preferably, bending secondary vibration) and stretching vibration (preferably, stretching primary vibration) are independently performed on one element. The electrodes are provided so as to be excited, and the arrangement thereof is optimized. Note that the bending (secondary) vibration is the transverse vibration (one wavelength in the second order≈the total length of the vibrator) schematically shown in FIG. 6A, and the expansion / contraction (primary) vibration is the same figure ( It is a longitudinal vibration (half wavelength in the first order = full length of the vibrator) schematically shown in b).
The present invention will be described in detail below.
本発明の圧電素子の加振点（電極位置）は、伸縮振動や屈曲振動を効率よく発生させるため、各振動による歪が最大となる場所に配置する。具体的には、伸縮振動では振動の「節」の位置に、屈曲運動では振動の「腹」の位置に電極を配置する。
例えば、矩形薄板状の圧電素子を用いた場合、屈曲２次振動の振幅分布は図７（ａ）に示すようになる。屈曲２次振動は圧電素子の全長がほぼ１波長に相当する横振動(素子面内に振幅を有する振動)であるため、歪が最大になる場所は振幅が最大になる箇所であり、振動の自由端である左右の端から１／４位置程度の場所である。実際は圧電素子の全長（Ｌ）は屈曲２次振動の１波長（λ2B）よりわずかに長く、歪みが最大になる場所は、左右の端から（１／４）Ｌ＋α中心に近い所となる。α＝（１／４）（Ｌ−λ2B）であり、通常、αはＬの４．５％〜６．５％程度である。従って、本発明ではこの位置に屈曲（２次）振動用の電極を配置する。
The excitation point (electrode position) of the piezoelectric element of the present invention is disposed at a location where the distortion due to each vibration is maximized in order to efficiently generate stretching vibration and bending vibration. Specifically, the electrode is arranged at the position of the vibration “node” in the stretching vibration, and at the position of the vibration “antinode” in the bending motion.
For example, when a rectangular thin plate-shaped piezoelectric element is used, the amplitude distribution of the bending secondary vibration is as shown in FIG. Since the bending secondary vibration is a transverse vibration (vibration having an amplitude in the element surface) corresponding to the entire length of the piezoelectric element, the place where the distortion is maximum is the place where the amplitude is the maximum. It is a place about 1/4 position from the left and right ends which are free ends. Actually, the total length (L) of the piezoelectric element is slightly longer than one wavelength (λ 2B ) of the bending secondary vibration, and the place where the distortion is maximized is near the (¼) L + α center from the left and right ends. α = (1/4) (L−λ 2B ), and α is usually about 4.5% to 6.5% of L. Therefore, in the present invention, an electrode for bending (secondary) vibration is disposed at this position.
また、同じく矩形薄板状の圧電素子を用いた場合の伸縮１次振動の振幅分布を図７（ｂ）に示す。伸縮１次振動は圧電素子の全長が１／２波長に相当する縦振動(素子の長手方向に振幅を有する振動)であるため、屈曲振動の場合とは異なり、歪が最大になる場所は変位が最小になる箇所であり、素子の中央付近である。従って、本発明ではこの位置に伸縮（１次）振動用の電極を配置する。
伸縮１次振動および屈曲２次振動において、振動の励振効率は共振周波数（ｆｓ）と反共振周波数（ｆｐ）の差（Δｆ＝ｆｐ−ｆｓ）で間接的に評価することが出来る事が知られている。図１２には伸縮１次振動、図１３および図１４には屈曲２次振動の、それぞれ分極領域の大きさを変えた場合のΔｆの推移を示す。
伸縮１次振動を励振する場合、振動子の伸縮１次振動のΔｆは、分極領域の長辺に平行な辺の長さが素子の長辺の長さの７０％程度が極大であり、９５％を超えると大幅に低下していることが分かる。このことから、伸縮１次振動を励振するための分極領域として、長辺側の長さは素子の長辺の９５％以下が好ましいといえる。一方で、５５％以下になった場合にもΔｆの低下が著しいが、伸縮１次振動は、ステータとスライダを突き離すという補助的な振動が主な役割であるので、励振効率の低下という欠点よりもむしろ電極面積が小さくなることに伴う消費電力の低減化という利点が好まれる場合が多い。このことから、伸縮１次振動を励振するための分極領域として、長辺側の長さは素子の長辺の長さの１０％以上が好ましく、振動効率を優先的に設計するならば、５５％以上が好ましいといえる。また、短辺側の長さは、屈曲２次振動を励振するための分極領域によって最大値が制限されるが、最小値としては素子の短辺側の長さの１０％以上であれば、長辺側の長さと同じ理由で、必要充分であると思われる。
また、屈曲２次振動を励振する場合、振動子の屈曲２次振動のΔｆは、各々の分極領域の短辺側の長さが素子の長辺側の側面から素子の短辺側の長さの３０％程度が極大であり、４０％を超える、または２０％以下になると大幅に低下していることが分かる。また、長辺側の長さは素子の長辺側の長さの３０％程度が極大であり、４０％を超える、または２０％以下になると大幅に低下していることが分かる。屈曲２次振動の歪み分布を有限要素解析によって調べてみると、歪みは素子の短辺から長辺に沿って長辺の長さの１／４程度中心寄りの領域において、素子の長辺側の側面近傍に局所的に集中している。したがって、局所的な励振をすることで、幾分は振動効率が低下すると思われるが、必要充分な振幅が得られると考えられる。屈曲２次振動の場合は、スライダの移動速度や駆動力を支配する主導的な役割であるので、励振効率は極力高い方が好まれる場合が多い。しかし、一方では消費電力の低減化に対する要望も多い。つまり、消費電力の低減化のために、歪みが集中する局所に、励振に必要十分な分極領域を設けてもよい。このことから、屈曲２次振動を励振するための分極領域として、各々の分極領域は、短辺側の長さは素子の長辺側側面から４０％以下が好ましく、長辺側の長さは４０％以下が好ましいといえる。なお、分極領域の下限値は、形状等の条件や求められる特性により変わり得る。有限要素解析等により有効と推定される最小値以上であればよいが、例えば、各１％以上、好ましくは素子の長辺側側面から３％以上、長辺側の長さ１０％以上、より好ましくはそれぞれ５％以上、２０％以上である。
Further, FIG. 7B shows the amplitude distribution of the expansion and contraction primary vibration when the rectangular thin plate-like piezoelectric element is used. The expansion and contraction primary vibration is a longitudinal vibration (vibration having an amplitude in the longitudinal direction of the element) corresponding to a half wavelength of the entire length of the piezoelectric element. Is a position where the current is minimized and is near the center of the element. Therefore, in the present invention, an electrode for expansion / contraction (primary) vibration is disposed at this position.
It is known that the vibration excitation efficiency can be indirectly evaluated by the difference (Δf = fp−fs) between the resonance frequency (fs) and the anti-resonance frequency (fp) in the expansion / contraction primary vibration and the bending secondary vibration. ing. FIG. 12 shows the transition of Δf in the case where the size of the polarization region of the expansion / contraction primary vibration is changed, and FIGS.
In the case of exciting the expansion and contraction primary vibration, Δf of the expansion and contraction primary vibration of the vibrator is maximum when the length of the side parallel to the long side of the polarization region is about 70% of the length of the long side of the element. It can be seen that when the ratio exceeds%, it is greatly reduced. From this, it can be said that the length of the long side is preferably 95% or less of the long side of the element as the polarization region for exciting the expansion and contraction primary vibration. On the other hand, although Δf is significantly reduced even when it is 55% or less, the primary vibration of expansion and contraction plays a main role of auxiliary vibration that pushes and separates the stator and the slider. Rather, the advantage of reduced power consumption associated with a smaller electrode area is often preferred. Therefore, as the polarization region for exciting the expansion and contraction primary vibration, the length on the long side is preferably 10% or more of the length of the long side of the element. % Or more is preferable. In addition, the maximum value of the length on the short side is limited by the polarization region for exciting the bending secondary vibration, and the minimum value is 10% or more of the length on the short side of the element. It seems necessary and sufficient for the same reason as the length on the long side.
When bending secondary vibration is excited, Δf of the bending secondary vibration of the vibrator is such that the length on the short side of each polarization region is the length on the short side of the element from the side on the long side of the element. It can be seen that about 30% of the maximum is a maximum, and when it exceeds 40% or 20% or less, it is greatly reduced. Further, it can be seen that the length on the long side is about 30% of the length on the long side of the element, and it is greatly reduced when it exceeds 40% or 20% or less. When the strain distribution of the bending secondary vibration is examined by the finite element analysis, the strain is in the region near the center of the length of the long side from the short side to the long side of the device. Concentrate locally in the vicinity of the side. Therefore, it is considered that the vibration efficiency is somewhat lowered by performing local excitation, but a necessary and sufficient amplitude can be obtained. In the case of bending secondary vibration, since it is a leading role that governs the moving speed and driving force of the slider, it is often preferred that the excitation efficiency be as high as possible. However, on the other hand, there are many requests for reducing power consumption. That is, in order to reduce power consumption, a polarization region necessary and sufficient for excitation may be provided in a region where distortion is concentrated. Therefore, as the polarization regions for exciting the bending secondary vibration, the length of each polarization region is preferably 40% or less from the long side surface of the element, and the length of the long side is It can be said that 40% or less is preferable. The lower limit value of the polarization region can vary depending on conditions such as shape and required characteristics. More than the minimum value estimated to be effective by finite element analysis or the like, for example, 1% or more each, preferably 3% or more from the long side surface of the element, 10% or more of the long side length Preferably, they are 5% or more and 20% or more, respectively.
以下では、伸縮１次振動と屈曲２次振動を例として説明するが、伸縮振動と屈曲振動とを独立に励振するものであれば、他の振動モードの組み合わせであってもよい。もっとも、高次モードでは一般に振幅の絶対値が小さくなり、伸縮振動と屈曲振動とを独立に励振するのが困難となる上、電極配置も複雑となるため、伸縮１次振動と屈曲２次振動の組み合わせが好ましい。また、以下の例では、概ね均一な厚みを有する矩形薄板状の圧電素子を用いた場合における矩形板の4辺に平行な辺によって画された分極領域の配置について説明するが、伸縮振動や屈曲振動による歪が最大となる場所に各振動を独立して励振し得るような分極領域の形状であれば、その形状は問わず、適当な解析手法によって決定されるそのような場所に分極領域および電気的信号を印加するための電極を配置した振動子も本発明の範囲に含まれる。 In the following description, the primary and secondary expansion vibrations and the secondary bending vibration will be described as an example. However, other vibration modes may be combined as long as the expansion and contraction vibrations and the bending vibrations are excited independently. However, in the higher order mode, the absolute value of the amplitude is generally small, and it becomes difficult to excite the stretching vibration and the bending vibration independently, and the electrode arrangement is complicated, so that the stretching primary vibration and the bending secondary vibration are complicated. The combination of is preferable. In the following example, the arrangement of the polarization regions defined by the sides parallel to the four sides of the rectangular plate when using a rectangular thin plate-shaped piezoelectric element having a substantially uniform thickness will be described. As long as the shape of the polarization region is such that each vibration can be excited independently at a place where the distortion due to the vibration is maximized, the shape of the polarization region and the region determined by an appropriate analysis method are not limited. A vibrator in which an electrode for applying an electrical signal is arranged is also included in the scope of the present invention.
本発明の超音波モータ用振動子の圧電素子の電極配置の基本構成を図１に示す。
図１に示すように、電極は伸縮１次振動用電極（図中、ｃ）と屈曲２次振動用電極（図中、ａ及びｂ）を含む。
伸縮１次振動用電極は、伸縮1次振動を励振するための分極領域の両面、つまり圧電素子（矩形板）の対向する長辺の中点を結ぶ中心線上の少なくとも一部を含む領域に設けられる。図示していないが、ｃの対電極は素子の裏面に存在し、両者間に交流電圧を印加することにより伸縮１次振動を励振する。
伸縮振動励起用の電極領域は、図１では概ね十字型の領域として示しているが、前記中心線の中点を含む限りにおいて任意の形状でよく、例えば、多角形、円形、楕円形でもよい。もっとも、図１の十字型のほか、圧電素子（矩形板）の各辺に平行な辺によって画される矩形状領域が好ましい。また、圧電素子側面への短絡のため、図１及び８に示すように一辺を素子側面に接触させてもよく、図９に示すように引き出し部分を作ってもよい。なお、引き出し部分は、電極領域間の配置、外部電極や端子の配置、構造等を考慮し、これらの間の干渉や電極等による振動の抑制が最小になるように配置することが好ましい。
FIG. 1 shows the basic configuration of the electrode arrangement of the piezoelectric element of the ultrasonic motor vibrator of the present invention.
As shown in FIG. 1, the electrodes include an expansion / contraction primary vibration electrode (c in the figure) and a bent secondary vibration electrode (a and b in the figure).
The electrode for expansion and contraction primary vibration is provided on both sides of the polarization region for exciting the expansion and contraction primary vibration, that is, the region including at least a part on the center line connecting the midpoints of the opposing long sides of the piezoelectric element (rectangular plate). It is done. Although not shown, the counter electrode of c exists on the back surface of the element, and excites the expansion and contraction primary vibration by applying an alternating voltage between them.
The electrode region for stretching vibration excitation is shown as a substantially cross-shaped region in FIG. 1, but may be any shape as long as it includes the midpoint of the center line, for example, a polygon, a circle, or an ellipse. . However, in addition to the cross shape in FIG. 1, a rectangular region defined by sides parallel to each side of the piezoelectric element (rectangular plate) is preferable. Further, for short circuit to the side surface of the piezoelectric element, one side may be brought into contact with the side surface of the element as shown in FIGS. 1 and 8, and a lead-out portion may be made as shown in FIG. In consideration of the arrangement between the electrode regions, the arrangement of the external electrodes and terminals, the structure, and the like, the lead-out portion is preferably arranged so as to minimize the interference between them and the suppression of vibration due to the electrodes.
本発明においては、前記領域における矩形板の長辺に平行な辺が、前記長辺の長さの１０％以上９５％以下であることが好ましい。１０％以下であっても伸縮振動を励振することは出来るが十分な励振を行なうことが困難である。一方、前述の中心点から外れた位置まで含めて電圧を印加しても励振効率は上がらず、静電容量が増すとともに電極によって却って振幅が抑制される。従って、特に図７に示すように、圧電素子の幅ほぼ全部に及ぶ矩形形状の電極とする場合は、長辺に沿った長さは、長辺全長の９５％以下が好ましく、８５％以下であることがより好ましい。
また、前記領域における矩形板の短辺に平行な辺が、前記短辺の長さの１０％以上であることが好ましい。１０％未満では分極領域の面積が小さくなりすぎるために十分な励振を行なうことが困難である。
伸縮１次振動用電極は、上記の通り、素子の分極領域の表裏面に設ける。
In the present invention, the side parallel to the long side of the rectangular plate in the region is preferably 10% or more and 95% or less of the length of the long side. Even if it is 10% or less, the stretching vibration can be excited, but it is difficult to perform sufficient excitation. On the other hand, even if a voltage is applied including a position deviating from the above-mentioned center point, the excitation efficiency does not increase, and the capacitance is increased and the amplitude is suppressed by the electrode. Therefore, as shown in FIG. 7 in particular, in the case of a rectangular electrode that covers almost the entire width of the piezoelectric element, the length along the long side is preferably 95% or less, and 85% or less of the total length of the long side. More preferably.
Moreover, it is preferable that the side parallel to the short side of the rectangular plate in the region is 10% or more of the length of the short side. If it is less than 10%, the area of the polarization region becomes too small, and it is difficult to perform sufficient excitation.
As described above, the expansion and contraction primary vibration electrodes are provided on the front and back surfaces of the polarization region of the element.
また、図１に示すように、屈曲２次振動用電極（図中ａ及びｂ）は、屈曲２次振動を励振するための分極領域の両面、つまり圧電素子（矩形板）の短辺から長辺に沿って長辺の長さの１／４だけ中心寄りの領域にそれぞれ設けられる各面２対の電極である。ここで、各対の電極は、前記中心点に対して点対称的に設られる。図示していないが、ａ及びｂの対電極は素子の裏面に存在し、ａとｂに逆位相の交流電圧を印加することにより屈曲２次振動を励振する。
ａ及びｂの電極は、互いに、また、ｃとの間で十分に絶縁が確保されるように設ければよいが、ａ及びｂの電極はｃとの間に０．２ないし０．５ｍｍの隙間を設けて、充分な絶縁性を確保することが好ましい。
Further, as shown in FIG. 1, the bending secondary vibration electrodes (a and b in the figure) are long from both sides of the polarization region for exciting the bending secondary vibration, that is, from the short side of the piezoelectric element (rectangular plate). These are two pairs of electrodes on each surface provided in a region closer to the center by ¼ of the length of the long side along the side. Here, each pair of electrodes is provided point-symmetrically with respect to the center point. Although not shown, the counter electrodes a and b exist on the back surface of the element, and excite a secondary bending vibration by applying an AC voltage having opposite phases to a and b.
The electrodes a and b may be provided so that sufficient insulation is secured between each other and between c and the electrodes a and b are 0.2 to 0.5 mm between c and c. It is preferable to provide a gap to ensure sufficient insulation.
本発明の振動子を超音波モータに用いる場合、早く動かしたい場合はａ−ｂ及びｃに大きな交流電圧を印加する。微動領域では、ｃには通常通りの電圧で、ａ−ｂに印加する電圧を弱くすることにより、微調節可能な振動状態を得る。従来の振動子が発生する楕円運動と、本発明の振動子が発生する楕円運動の比較を図５に示す。各振動を独立して励振できる本発明の振動子は、移動体への加圧方向の振動だけ予め充分に励起しておき、さらに送り方向の振動を微弱に励起することができる。そのため、低電圧領域においても比較的線形な特性が得られ、しきい電圧を超えてからの急峻な特性を緩和し、微動領域の制御性を高めることができる。 When the vibrator of the present invention is used in an ultrasonic motor, a large alternating voltage is applied to ab and c if it is desired to move quickly. In the fine movement region, a normal state voltage is applied to c, and a vibration state that can be finely adjusted is obtained by weakening the voltage applied to ab. FIG. 5 shows a comparison between the elliptical motion generated by the conventional vibrator and the elliptical motion generated by the vibrator of the present invention. The vibrator of the present invention capable of exciting each vibration independently can sufficiently excite the vibration in the pressurizing direction to the moving body in advance, and can further excite the vibration in the feeding direction weakly. Therefore, a relatively linear characteristic can be obtained even in the low voltage region, the steep characteristic after exceeding the threshold voltage can be relaxed, and the controllability of the fine movement region can be improved.
各電極は、適宜、電圧印加用のリード部分を有してもよいし、あるいは圧電素子板に電極が設けられたフレキシブル基板を接合してもよい。
また、本発明の超音波モータ用振動子は、単層の振動子に限定されず、上述の振動子を積層したものでもよい。本発明では、圧電体の全ての層に屈曲振動を励振させる部分と伸縮振動を励振させる部分を配置する。そのため、振動子全体に占める加振領域の割合も多くなり、振動効率の良い振動子が得られる。
Each electrode may have a lead portion for applying a voltage as appropriate, or may be joined to a flexible substrate provided with electrodes on a piezoelectric element plate.
The ultrasonic motor vibrator of the present invention is not limited to a single-layer vibrator, and may be a laminate of the above-described vibrators. In the present invention, a portion for exciting bending vibration and a portion for exciting stretching vibration are arranged in all layers of the piezoelectric body. For this reason, the proportion of the excitation area in the entire vibrator increases, and a vibrator with good vibration efficiency can be obtained.
本発明において用いる圧電素子及び電極の材料、振動子上に電極を付与する方法、積層体とする場合の積層方法は、当分野で利用可能な任意の材料及び方法を含む。後で述べる実施例においては圧電素子材料としては、チタン酸ジルコン酸鉛（ＰＺＴ）を用いたが、他の圧電性材料、例えばニオブ酸リチウム（ＬｉＮｂＯ3）、タンタル酸リチウム（ＬｉＴａＯ3）、リチウムテトラボレート（Ｌｉ2Ｂ4Ｏ7）、ランガサイト（Ｌａ3Ｇａ5ＳｉＯ14）、窒化アルミニウム等の無機材料、ポリフッ化ビニリデン（ＰＶＤＦ）等の有機圧電材料を用いても良い。また、後で述べる実施例においては電極材料としては、銀・パラジウム合金電極を用いたが、他の電極材料、例えば銅、銀、金、アルミニウム、白金、パラジウムあるいはこれらを含む合金等を用いても良い。電極付与方法の例としては、導電ペーストの塗布ないし印刷、メッキ、蒸着等が挙げられる。
積層体を形成する手法の例としては、圧電素子材料とバインダーを含むスラリーをシート状に成型、乾燥し、その上に図１０に示すように、圧電素子側面への短絡のために引き出される引き出し電極の位置を変えた２種類の電極（内部電極）パターンを付与した後、図１１に示すような順序でこれらを積層、本焼成し、さらに外部電極を設ける方法が挙げられる。図１５に、個々の圧電体の内部電極と１層おきに短絡する外部電極７ａ、７ｂ、８ａ、８ｂを形成した積層型の振動子を示す。もっとも、以上はいずれも例であり、この他の材料や方法を用いても本発明の振動子を製造することは可能である。
The material of the piezoelectric element and electrode used in the present invention, the method of applying an electrode on a vibrator, and the method of laminating in the case of a laminate include any materials and methods available in the art. In examples described later, lead zirconate titanate (PZT) was used as the piezoelectric element material, but other piezoelectric materials such as lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), lithium An inorganic material such as tetraborate (Li 2 B 4 O 7 ), langasite (La 3 Ga 5 SiO 14 ), aluminum nitride, or an organic piezoelectric material such as polyvinylidene fluoride (PVDF) may be used. In the examples described later, a silver / palladium alloy electrode is used as the electrode material. However, other electrode materials such as copper, silver, gold, aluminum, platinum, palladium or alloys containing these are used. Also good. Examples of the electrode application method include application or printing of conductive paste, plating, vapor deposition, and the like.
As an example of a method of forming a laminate, a slurry containing a piezoelectric element material and a binder is formed into a sheet, dried, and then drawn out for short-circuiting to the side of the piezoelectric element as shown in FIG. There is a method of providing two types of electrode (internal electrode) patterns in which the positions of the electrodes are changed, then laminating them in the order shown in FIG. FIG. 15 shows a laminated vibrator in which internal electrodes of individual piezoelectric bodies and external electrodes 7a, 7b, 8a, and 8b that are short-circuited every other layer are formed. However, the above is only an example, and it is possible to manufacture the vibrator of the present invention using other materials and methods.
なお、本明細書において「超音波モータ」とは、振動子の少なくとも一部の部位が圧電機構によって楕円運動を行い、他の部材を駆動し得るものをすべて含む。また、その振動周波数は、必ずしも超音波域でなくてもよく駆動源として機能し得るものであればよい。 In the present specification, the “ultrasonic motor” includes all of those that can drive at least a part of the vibrator to perform an elliptical motion by a piezoelectric mechanism and drive other members. Further, the vibration frequency does not necessarily have to be in the ultrasonic range as long as it can function as a drive source.
実施例１
厚さ２ｍｍ×長さ３０ｍｍ×幅８．４ｍｍの矩形状の圧電素子板を用意し、図１に準じた形状及び配置の伸縮１次振動用電極及び屈曲２次振動用電極を形成した。伸縮１次振動用電極は長さ２０ｍｍの十字型とし、圧電素子の面積の４１％の大きさを有する。屈曲２次振動用の電極は、各々、長さ６ｍｍ、幅１．５ｍｍとし、２対で圧電素子の面積の１４％を有する。短辺中央部にはステータを接着した。
前記圧電振動子の端部に接着したステータの振動状態を測定した結果を図１６に示す。電極ａとｂには位相差１８０度でそれぞれ１００Ｖp-p、５５．２ｋＨｚの交流電圧を印加するとともに、電極ｃには電極ａとｂに印加する信号と位相が異なる信号として、１００Ｖp-p、同一周波数の交流電圧を印加した。なお、電極ａとｂに対する電極ｃの位相差は、端部の振動位相に９０度の位相差が生じるように適宜調節した。この結果、図１６に示すように、短辺中央に設けたステータは楕円運動を行なうことが確認された。電極ａとｂと電極ｃの伸縮１次振動への寄与を調べるため電極ａとｂの印加電圧の振幅を２５Ｖp-pまで低減したところステータの楕円運動の長径はほぼ変わらないものの（ほぼ１００％）、短径は２５％まで低減し、非常に微細な独立した制御が可能であることが確認できた。
Example 1
A rectangular piezoelectric element plate having a thickness of 2 mm, a length of 30 mm, and a width of 8.4 mm was prepared, and a stretchable primary vibration electrode and a bent secondary vibration electrode having a shape and arrangement according to FIG. 1 were formed. The expansion / contraction primary vibration electrode is a cross shape having a length of 20 mm and has a size of 41% of the area of the piezoelectric element. Each of the electrodes for bending secondary vibration has a length of 6 mm and a width of 1.5 mm, and two pairs have 14% of the area of the piezoelectric element. A stator was bonded to the center of the short side.
FIG. 16 shows the result of measuring the vibration state of the stator bonded to the end of the piezoelectric vibrator. Electrodes a and b, respectively 100 V pp 180 degrees out of phase in, while applying an AC voltage of 55.2KHz, as a signal to the electrode c to be applied to the electrodes a and b and the signal having different phases, 100 V pp, the same frequency AC voltage was applied. In addition, the phase difference of the electrode c with respect to the electrodes a and b was adjusted as appropriate so that a phase difference of 90 degrees was generated in the vibration phase at the end. As a result, as shown in FIG. 16, it was confirmed that the stator provided at the center of the short side performs an elliptical motion. When the amplitude of the applied voltage of the electrodes a and b is reduced to 25 V pp in order to investigate the contribution of the electrodes a and b and the electrode c to the expansion and contraction primary vibration, the major axis of the elliptical motion of the stator is not substantially changed (almost 100%). The minor axis was reduced to 25%, and it was confirmed that very fine independent control was possible.
実施例２
厚さ２ｍｍ×長さ３０ｍｍ×幅８．４ｍｍの矩形状の圧電素子板を用意し、図８に準じた形状及び配置の伸縮１次振動用電極及び屈曲２次振動用電極を形成した。伸縮１次振動用電極は長さ６ｍｍの矩形とし、圧電素子の面積の１９％の大きさを有する。屈曲２次振動用の電極は実施例１と同様に、各々、長さ６ｍｍ、幅１．５ｍｍとし、２対で圧電素子の面積の１４％を有する。短辺中央部にはステータを接着した。また実施例１と同様に短辺中央部にはステータを接着した。
各々の電極には実施例１と同様の電圧を印加したので、以下には測定結果について実施例１との相違点について主に述べる。測定の結果、伸縮１次振動用の分極領域が素子の長辺の２０％という小さな領域になったことに伴う伸縮１次振動の大幅な振幅低下が認められたが、短辺中央に設けたステータには楕円運動の発生が確認された。電極ａとｂと電極ｃの伸縮１次振動への寄与を調べるため電極ａとｂの印加電圧の振幅を２５Ｖp-pまで低減したところステータの楕円運動の長径はほぼ変わらないものの（ほぼ１００％）、短径は２５％まで低減し、実施例１と同様に、非常に微細な独立した制御が可能であることが確認できた。
Example 2
A rectangular piezoelectric element plate having a thickness of 2 mm, a length of 30 mm, and a width of 8.4 mm was prepared, and a stretchable primary vibration electrode and a bent secondary vibration electrode having a shape and arrangement according to FIG. 8 were formed. The expansion / contraction primary vibration electrode is a rectangle having a length of 6 mm and has a size of 19% of the area of the piezoelectric element. Similar to the first embodiment, each of the electrodes for bending secondary vibration has a length of 6 mm and a width of 1.5 mm, and two pairs have 14% of the area of the piezoelectric element. A stator was bonded to the center of the short side. Further, as in Example 1, a stator was bonded to the central portion of the short side.
Since the same voltage as in Example 1 was applied to each electrode, the difference from Example 1 in the measurement results will be mainly described below. As a result of the measurement, a significant decrease in the amplitude of the expansion / contraction primary vibration was observed as the polarization region for the expansion / contraction primary vibration became a small region of 20% of the long side of the element. Occurrence of elliptical motion was confirmed in the stator. When the amplitude of the applied voltage of the electrodes a and b is reduced to 25 V pp in order to investigate the contribution of the electrodes a and b and the electrode c to the expansion and contraction primary vibration, the major axis of the elliptical motion of the stator is not substantially changed (almost 100%). The minor axis was reduced to 25%, and as in Example 1, it was confirmed that very fine independent control was possible.
実施例３
厚さ２ｍｍ×長さ３０ｍｍ×幅８．４ｍｍの矩形状の圧電素子板を用意し、図９に準じた形状及び配置の伸縮１次振動用電極及び屈曲２次振動用電極を形成した。伸縮１次振動用電極は長さ２０ｍｍの矩形とし、圧電素子の面積の２９％の大きさを有する。屈曲２次振動用の電極は実施例１と同様に、各々、長さ６ｍｍ、幅１．５ｍｍとし、２対で圧電素子の面積の１４％を有する。短辺中央部にはステータを接着した。また実施例１と同様に短辺中央部にはステータを接着した。
各々の電極には実施例１と同様の電圧を印加したので、以下には測定結果について実施例１及び実施例２との相違点について主に述べる。測定の結果、伸縮１次振動用の分極領域が実施例１より小さく、また実施例２より大きくなったことに伴う伸縮１次振動の振幅が実施例１より若干小さく、実施例２より大幅に大きくなったことが認められ、短辺中央に設けたステータは楕円運動を行なうことが確認された。電極ａとｂと電極ｃの伸縮１次振動への寄与を調べるため電極ａとｂの印加電圧の振幅を２５Ｖp-pまで低減したところステータの楕円運動の長径はほぼ変わらないものの（ほぼ１００％）、短径は２５％まで低減し、この場合でも実施例１と同様に、非常に微細な独立した制御が可能であることが確認できた。
Example 3
A rectangular piezoelectric element plate having a thickness of 2 mm, a length of 30 mm, and a width of 8.4 mm was prepared, and a stretchable primary vibration electrode and a bent secondary vibration electrode having a shape and arrangement according to FIG. 9 were formed. The expansion / contraction primary vibration electrode has a rectangular shape with a length of 20 mm, and has a size of 29% of the area of the piezoelectric element. Similar to the first embodiment, each of the electrodes for bending secondary vibration has a length of 6 mm and a width of 1.5 mm, and two pairs have 14% of the area of the piezoelectric element. A stator was bonded to the center of the short side. Further, as in Example 1, a stator was bonded to the central portion of the short side.
Since the same voltage as in Example 1 was applied to each electrode, the following description will mainly describe differences in measurement results from Example 1 and Example 2. As a result of measurement, the amplitude of the expansion and contraction primary vibration due to the fact that the polarization region for the expansion and contraction primary vibration is smaller than that of the first embodiment and larger than that of the second embodiment is slightly smaller than that of the first embodiment. It was confirmed that the stator was large, and the stator provided at the center of the short side was confirmed to perform elliptical motion. When the amplitude of the applied voltage of the electrodes a and b is reduced to 25 V pp in order to investigate the contribution of the electrodes a and b and the electrode c to the expansion and contraction primary vibration, the major axis of the elliptical motion of the stator is not substantially changed (almost 100%). The minor axis was reduced to 25%, and even in this case, it was confirmed that very fine independent control was possible as in Example 1.
実施例４
実施例１〜３の電極配置を持つ、厚み０．０８ｍｍの圧電素子を３５層積層した積層型の超音波モータ用振動子を形成し、実施例１ないし実施例３と同様に振動状態を測定した。圧電体の１層厚みが薄くなったことに伴い、実施例１ないし実施例３と同程度の振幅を得るために必要な印加電圧は大幅に低下し、約５Ｖp-pで同程度の振幅が得られた。前記電圧を印加して振動状態を測定したところ、短辺中央に設けたステータは楕円運動を行なうことが確認された。また、電極ａとｂと電極ｃの伸縮１次振動への寄与を調べるため電極ａとｂの印加電圧の振幅を１Ｖp-pまで低減したところステータの楕円運動の長径はほぼ変わらないものの（ほぼ１００％）、短径は２０％まで低減し、実施例１ないし実施例３と同様に、各振動モードが互いに独立した制御が可能であることが確認できた。
Example 4
A laminated ultrasonic motor vibrator in which 35 layers of piezoelectric elements having a thickness of 0.08 mm having the electrode arrangements of Examples 1 to 3 are stacked is formed, and the vibration state is measured in the same manner as in Examples 1 to 3. did. As the thickness of one layer of the piezoelectric material is reduced, the applied voltage required to obtain the same amplitude as in the first to third embodiments is greatly reduced, and the same amplitude is obtained at about 5 Vpp. It was. When the vibration state was measured by applying the voltage, it was confirmed that the stator provided at the center of the short side performs an elliptical motion. Further, when the amplitude of the voltage applied to the electrodes a and b was reduced to 1 V pp in order to investigate the contribution of the electrodes a, b, and c to the expansion and contraction primary vibration, the major axis of the elliptical motion of the stator remained almost the same (almost 100 %), The minor axis was reduced to 20%, and it was confirmed that each vibration mode can be controlled independently of each other as in Example 1 to Example 3.
本発明の圧電素子は、最適な電極配置を採ることで、送り方向の振幅（図３の楕円運動の横方向の振幅）と加圧方向の振幅（図３の楕円運動の縦方向の振幅）を独立で制御できる。このため、いわゆる「超音波モータ」の駆動源として広く用いることができる。 The piezoelectric element of the present invention adopts an optimum electrode arrangement, so that the amplitude in the feeding direction (amplitude in the lateral direction of the elliptical motion in FIG. 3) and the amplitude in the pressing direction (the amplitude in the vertical direction of the elliptical motion in FIG. 3). Can be controlled independently. For this reason, it can be widely used as a drive source of a so-called “ultrasonic motor”.
ａ 屈曲２次振動用電極
ｂ 屈曲２次振動用電極
ｃ 伸縮１次振動用電極
１ 振動子
２ スライダ
３ 固定摺動部材（ステータ）
４ ガイド
ｐ 振動子の左端面の中心点
６ 積層型振動子
７ａ、ｂ 外部電極
８ａ、ｂ 外部電極
a flexural secondary vibration electrode b flexual secondary vibration electrode c telescopic primary vibration electrode 1
4 Guide p Center point of left end face of
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Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |