JP2016162998A - Method of manufacturing annular piezoelectric element - Google Patents
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本発明は、進行波型超音波モーターなどに用いられる円環状圧電素子の製造方法に関する。具体的には圧電歪１５モードを用いて駆動する円環状圧電素子の製造方法に関する。 The present invention relates to a method for manufacturing an annular piezoelectric element used in a traveling wave type ultrasonic motor or the like. Specifically, the present invention relates to a method for manufacturing an annular piezoelectric element that is driven using a piezoelectric strain 15 mode.
周知のごとく、互いに対面する二つの電極板で圧電体を狭持してなる圧電素子は、電界の印加方向と振動方向との関係によって様々な振動モード（圧電歪モードとも言う）がある。そして進行波形超音波モーター（以下、超音波モーター）やランジュバン振動子などに利用される圧電素子は、円環状の圧電体の表裏両面を電極板で狭持した構造を有した円環状圧電素子であり、圧電歪モードとしては電界の印加方向と振動方向が一致する圧電歪３１モードを用いることが多い。概略的には円環状の圧電体の表裏両面の円環中央を貫く軸方向を上下方向とすると、圧電体の分極方向は上下方向であり、円周が複数の分極領域に分割されて互いに隣り合う分極領域ではその分極方向が上下反対方向となっている。 As is well known, a piezoelectric element having a piezoelectric body sandwiched between two electrode plates facing each other has various vibration modes (also referred to as piezoelectric strain modes) depending on the relationship between the direction of application of an electric field and the vibration direction. Piezoelectric elements used in traveling waveform ultrasonic motors (hereinafter referred to as ultrasonic motors) and Langevin vibrators are annular piezoelectric elements having a structure in which both front and back surfaces of an annular piezoelectric body are sandwiched between electrode plates. In many cases, the piezoelectric strain mode is a piezoelectric strain 31 mode in which the direction of electric field application and the direction of vibration coincide. In general, when the axial direction passing through the center of the ring on both the front and back sides of the annular piezoelectric body is the vertical direction, the polarization direction of the piezoelectric body is the vertical direction, and the circumference is divided into a plurality of polarization regions and adjacent to each other. In the matching polarization region, the polarization direction is the opposite direction.
しかしながら圧電体において圧電歪３１モードに対応する圧電定数ｄ３１は、ｄ３３やｄ１５に比べて約半分の値であり、超音波モーターであれば高いモータトルクを得ることが難しい。そこで大きな圧電定数ｄ１５を利用した圧電歪１５モードで円環状圧電素子を駆動させることが考えられる。そして圧電歪１５モードで駆動する円環状圧電素子では、圧電体の分極方向が円環を周回する方向となる。なお圧電歪１５モードで駆動する円環状圧電素子の応用例としては、周知の「ねじり式モーター」がある。また圧電素子の振動モードや圧電素子の評価方法などについては以下の非特許文献１に記載されている。 However, the piezoelectric constant d 31 corresponding to the piezoelectric strain 31 mode in the piezoelectric body is about half that of d 33 and d 15 , and it is difficult to obtain a high motor torque with an ultrasonic motor. Therefore it is conceivable to drive the annular piezoelectric element of a piezoelectric strain 15 mode using a large piezoelectric constant d 15. In the annular piezoelectric element driven in the piezoelectric strain 15 mode, the polarization direction of the piezoelectric body is a direction around the ring. As an application example of the annular piezoelectric element driven in the piezoelectric strain 15 mode, there is a well-known “torsion type motor”. Further, the vibration mode of the piezoelectric element and the evaluation method of the piezoelectric element are described in Non-Patent Document 1 below.
上述したように、圧電歪１５モードを利用した円環状圧電素子では、円環状の圧電体を周方向に一方向に分極する必要がある。周知のごとく、圧電体を分極するためには圧電体を二つの電極板で狭持して大きな電界を印加する。圧電歪３１モードであれば一体的な円環状圧電体の上面と下面に電極を配置して電界を印加すれば上下方向に分極する。しかし圧電歪１５モードで使用する円環状圧電素子では、円環の円周に沿う方向に分極している。図１に圧電歪１５モードで使用する円環状圧電素子における従来の分極手順を示した。まず図１（Ａ）に示したように、扇状に円周分割された圧電材料からなるセラミックス焼結体１１０の端面に導電性ペーストなどを塗布して電極１２０を形成し、この電極間（１２０−１２０）の電圧Ｖによって扇状の圧電体１１０に電界Ｅを印加する。そして図１（Ｂ）に示したように電極１２０を除去して扇状の圧電体１１１を作製する。なお図中では分極方向を矢印Ｐで示した。つぎに図１（Ｃ）に示したように扇状の圧電体１１１の表裏両面に駆動用の電極（以下、駆動用電極１３０）を形成する。そして図１（Ｄ）に示したように表裏両面に駆動用電極１３０が形成された扇状の圧電体１１１を円環状に配置した状態で固定すると、図１（Ｄ）に示した円環状圧電素子１００が完成する。このように圧電歪１５モードで使用する円環状圧電素子は極めて複雑な工程を経て作製される。そのため製造コストが嵩み圧電素子を安価に提供することが難しくなる。 As described above, in the annular piezoelectric element using the piezoelectric strain 15 mode, it is necessary to polarize the annular piezoelectric body in one direction in the circumferential direction. As is well known, in order to polarize a piezoelectric body, the piezoelectric body is sandwiched between two electrode plates and a large electric field is applied. In the piezoelectric strain 31 mode, when electrodes are arranged on the upper and lower surfaces of an integral annular piezoelectric body and an electric field is applied, it is polarized in the vertical direction. However, the annular piezoelectric element used in the piezoelectric strain 15 mode is polarized in the direction along the circumference of the ring. FIG. 1 shows a conventional polarization procedure in an annular piezoelectric element used in the piezoelectric strain 15 mode. First, as shown in FIG. 1A, an electrode 120 is formed by applying a conductive paste or the like to the end face of a ceramic sintered body 110 made of a piezoelectric material that is divided into a fan shape, and between the electrodes (120 The electric field E is applied to the fan-shaped piezoelectric body 110 by the voltage V of −120). Then, as shown in FIG. 1B, the electrode 120 is removed to produce a fan-shaped piezoelectric body 111. In the figure, the polarization direction is indicated by an arrow P. Next, as shown in FIG. 1C, driving electrodes (hereinafter referred to as driving electrodes 130) are formed on the front and back surfaces of the fan-shaped piezoelectric body 111. Then, as shown in FIG. 1D, when the fan-shaped piezoelectric body 111 having the driving electrodes 130 formed on both front and back surfaces is fixed in an annular shape, the annular piezoelectric element shown in FIG. 100 is completed. As described above, the annular piezoelectric element used in the piezoelectric strain 15 mode is manufactured through an extremely complicated process. Therefore, the manufacturing cost increases and it becomes difficult to provide the piezoelectric element at a low cost.
そこで本発明は、圧電歪１５モードで使用する円環状圧電素子をより簡素な工程を用いてより安価に製造するための方法を提供することを目的としている。 Therefore, an object of the present invention is to provide a method for manufacturing an annular piezoelectric element used in the piezoelectric strain 15 mode at a lower cost by using a simpler process.
上記目的を達成するための本発明は、円環状の圧電体の表裏に電極が形成されて、当該電極間に電界を印加すると圧電歪１５モードで振動する円環状圧電素子の製造方法であって、
円環の軸方向を上下方向として、
圧電材料からなる一体的な円環状セラミック焼結体を成形する焼結体成形ステップと、 前記円環状セラミックス焼結体の上面に半径方向に延長する分極用電極を複数箇所に配置する電極配置ステップと、
前記複数箇所に配置された分極用電極のうち、互いに隣り合う二つの電極の一方を接地電極として当該二つの電極間に電位差を与えることで、前記円環状セラミック焼結体において当該二つの分極用電極によって区分される円周分割領域を円周方向に向かって分極させる分極ステップと、
を含むことを特徴とする円環状圧電素子の製造方法としている。
In order to achieve the above object, the present invention provides a method for manufacturing an annular piezoelectric element in which electrodes are formed on the front and back surfaces of an annular piezoelectric body and vibrates in a piezoelectric strain 15 mode when an electric field is applied between the electrodes. ,
With the axial direction of the ring as the vertical direction,
A sintered body forming step for forming an integral annular ceramic sintered body made of a piezoelectric material, and an electrode arrangement step for arranging polarization electrodes extending in the radial direction on the upper surface of the annular ceramic sintered body at a plurality of locations. When,
Among the electrodes for polarization arranged at the plurality of locations, one of two electrodes adjacent to each other is used as a ground electrode, and a potential difference is applied between the two electrodes, so that the two electrodes for polarization in the annular ceramic sintered body A polarization step that polarizes a circumferentially divided region divided by the electrodes in a circumferential direction;
It is set as the manufacturing method of the annular | circular shaped piezoelectric element characterized by including these.
前記電極配置ステップでは、分極用電極を配置する角度位置を３カ所以上とし、
前記分極ステップでは、互いに隣り合う二つの分極電極を順次選択するとともに、当該二つの分極用電極の延長方向がなす劣角側の円周分割領域を円周の所定方向に向かって分極させる、
ことを特徴とする円環状圧電素子の製造方法とすることもできる。
In the electrode arrangement step, the angular position where the electrode for polarization is arranged is 3 or more,
In the polarization step, the two polarization electrodes adjacent to each other are sequentially selected, and the circumferential divided region on the minor angle side formed by the extension direction of the two polarization electrodes is polarized in a predetermined direction of the circumference.
It can also be set as the manufacturing method of the annular piezoelectric element characterized by this.
前記電極配置ステップでは、前記円環状セラミック焼結体の半径方向に延長する前記分極用電極体が、所定の半径となる位置にて分割されて、内周側から外周側に向かって複数の分極電極片が形成され、
前記分極ステップでは、同じ半径となる領域に形成されて互いに周方向で隣接する二つの前記分極用電極片を選択するともに、選択した二つの分極用電極片が属する分極用電極の延長方向がなす劣角側の円周分割領域に同じ強度の電界が印加されるように電位差を与える、
ことを特徴とする円環状圧電素子の製造方法としてもよい。
In the electrode arrangement step, the polarization electrode body extending in the radial direction of the annular ceramic sintered body is divided at a position having a predetermined radius, and a plurality of polarizations are performed from the inner circumference side toward the outer circumference side. An electrode piece is formed,
In the polarization step, two polarization electrode pieces that are formed in a region having the same radius and are adjacent to each other in the circumferential direction are selected, and an extension direction of the polarization electrode to which the two selected polarization electrode pieces belong is defined. Giving a potential difference so that an electric field of the same strength is applied to the circumferentially divided region on the minor angle side,
It is good also as a manufacturing method of the annular piezoelectric element characterized by this.
前記焼結体成形ステップでは、上面に半径方向に延長する溝が形成された円環状セラミックス焼結体を成形し、
前記分極用電極配置ステップでは、前記溝内に導電体を配置する、
ことを特徴とする円環状圧電素子の製造方法としてもよい。
In the sintered body forming step, an annular ceramic sintered body in which grooves extending in the radial direction are formed on the upper surface is formed,
In the polarization electrode placement step, a conductor is placed in the groove.
It is good also as a manufacturing method of the annular piezoelectric element characterized by this.
前記焼結体成形ステップでは、半径方向を横断する切欠が形成された円環状セラミックス焼結体を形成し、
前記分極ステップでは、前記切欠をギャップとすることで、前記円環状セラミックス焼結体を周の一方向にのみ分極させる、
ことを特徴とする円環状圧電素子の製造方法とすることもできる。そして前記切欠に絶縁体からなる補強部材を充填することを特徴とする円環状圧電素子の製造方法としてもよい。
In the sintered body forming step, an annular ceramic sintered body in which a notch traversing the radial direction is formed is formed,
In the polarization step, the annular ceramic sintered body is polarized only in one circumferential direction by setting the notch as a gap.
It can also be set as the manufacturing method of the annular piezoelectric element characterized by this. And it is good also as a manufacturing method of the annular | circular shaped piezoelectric element characterized by filling the said notch with the reinforcing member which consists of an insulator.
本発明によれば、圧電歪１５モードで使用する円環状圧電素子をより簡素な工程を用いてより安価に製造することができる。なお、その他の効果については以下の記載で明らかにする。 According to the present invention, an annular piezoelectric element used in the piezoelectric strain 15 mode can be manufactured at a lower cost by using a simpler process. Other effects will be clarified in the following description.
本発明の実施例について、以下に添付図面を参照しつつ説明する。なお以下の説明に用いた図面において、同一または類似の部分に同一の符号を付して重複する説明を省略することがある。ある図面において符号を付した部分について、不要であれば他の図面ではその部分に符号を付さない場合もある。 Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the drawings used for the following description, the same or similar parts may be denoted by the same reference numerals and redundant description may be omitted. In some drawings, reference numerals may be assigned to parts that are not required in other drawings if unnecessary.
＝＝＝第１の実施例＝＝＝
図２は本発明の実施例に係る製造方法によって製造される円環状圧電素子の一例を示す図である。当該圧電素子１は、円環の軸方向を上下方向として、一体的な円環状圧電体１１の上下両面に円周分割された駆動用電極３０が形成されている。そして円環状圧電体１１は円環を周回する方向Ｐに分極している。そして本発明の実施例に係る円環状圧電素子の製造方法では、圧電材料からなる円環状セラミックス焼結体を円環を周回する方向に分極させる手順に大きな特徴がある。
=== First Embodiment ===
FIG. 2 is a view showing an example of an annular piezoelectric element manufactured by the manufacturing method according to the embodiment of the present invention. In the piezoelectric element 1, driving electrodes 30 that are circumferentially divided are formed on both upper and lower surfaces of an integrated annular piezoelectric body 11 with the axial direction of the ring being the vertical direction. The annular piezoelectric body 11 is polarized in the direction P that goes around the ring. The method for manufacturing an annular piezoelectric element according to the embodiment of the present invention has a great feature in the procedure of polarizing an annular ceramic sintered body made of a piezoelectric material in a direction around the ring.
概略的には、円環状セラミックス焼結体の上下一方の面に上記軸から放射方向に上面を横断する分極用電極を複数に形成し、その複数の分極用電極において、互いに隣接する分極用電極間に一方向の電界を印加することで圧電体を円周の一方向に分極させることとしている。以下では、基本的な分極手順を本発明の第１の実施例として挙げる。 Schematically, a plurality of polarizing electrodes that cross the upper surface in the radial direction from the axis are formed on one of the upper and lower surfaces of the annular ceramic sintered body, and the polarizing electrodes adjacent to each other in the plurality of polarizing electrodes By applying an electric field in one direction between them, the piezoelectric body is polarized in one direction on the circumference. In the following, a basic polarization procedure is given as a first embodiment of the present invention.
図３に第１の実施例の概略を示した。なお第１の実施例を含め、以下に挙げる各実施例では分極用電極２０を円環状セラミックス焼結体１０の上面１２に形成することとする。そして図３に示したように、第１の実施例に係る製造方法では一体的な円環状セラミックス焼結体（以下、円環状焼結体１０とも言う）の上面１２に二つの分極用電極（２１、２２）を劣角θ１（あるいは優角θ２）となるように形成し、その二つの分極用電極間（２１−２２）に電位差Ｖを与えることで、当該二つの電極間（２１−２２）の円周分割領域（１２１、１２２）に円周に沿った一方向の電界（Ｅ１、Ｅ２）を印加する。それによって劣角θ１に対応する円周分割領域１２１と優角θ２に対応する円周分割領域１２２のそれぞれが円周に沿うように分極する。またその分極方向は互いに反対となる。なお分極用電極（２１、２２）については銀ペーストなどを印刷によって形成してもよいし、焼結体１０の表面に固定せずに帯状の金属板を焼結体１０の上面１２に一時的に接触させることで形成してもよい。そして焼結体１０を分極させてなる圧電体の上下両面に駆動用電極を形成すれば図２に示したような円環状圧電素子１が完成する。円環状圧電素子１を駆動する際には、上下方向で対面する駆動用電極間（３０−３０）の電圧を分極の方向や分極の強度に応じて制御すればよい。 FIG. 3 shows an outline of the first embodiment. In each of the following examples including the first example, the polarization electrode 20 is formed on the upper surface 12 of the annular ceramic sintered body 10. As shown in FIG. 3, in the manufacturing method according to the first embodiment, two polarizing electrodes (on the upper surface 12 of an integral annular ceramic sintered body (hereinafter also referred to as an annular sintered body 10)). 21 and 22) are formed so as to have an inferior angle θ 1 (or a dominant angle θ 2 ), and a potential difference V is applied between the two polarization electrodes (21-22), so that the two electrodes (21 A unidirectional electric field (E 1 , E 2 ) along the circumference is applied to the circumferential division region (121, 122) of −22). As a result, each of the circumferential divided region 121 corresponding to the minor angle θ 1 and the circumferential divided region 122 corresponding to the dominant angle θ 2 is polarized along the circumference. The polarization directions are opposite to each other. The polarization electrodes (21, 22) may be formed by printing a silver paste or the like, or a band-shaped metal plate may be temporarily attached to the upper surface 12 of the sintered body 10 without being fixed to the surface of the sintered body 10. You may form by making it contact. Then, if driving electrodes are formed on the upper and lower surfaces of the piezoelectric body obtained by polarizing the sintered body 10, the annular piezoelectric element 1 as shown in FIG. 2 is completed. When the annular piezoelectric element 1 is driven, the voltage between the driving electrodes facing in the vertical direction (30-30) may be controlled in accordance with the direction of polarization and the intensity of polarization.
＜分極状態＞
図３に示した第１の実施例に係る製造方法では、円環状焼結体１０の軸５０に対して半径方向に延長する二つの分極用電極（２１、２２）によって分極していた。そのため焼結体１０は劣角θ１の円周分割領域１２１と、優角θ２の円周分割領域１２２の二つの領域に分割され、それぞれの領域（１２１、１２２）では分極方向が互いに反対方向となる。また二つの円周分割領域（１２１、１２２）に印加される電界強度（Ｅ１、Ｅ２）は分極用電極間（２１−２２）の周方向の距離に反比例するため、劣角θ１に対応する円周分割領域１２１の方が分極の強度が大きくなる。
<Polarization state>
In the manufacturing method according to the first embodiment shown in FIG. 3, polarization is performed by two polarization electrodes (21, 22) extending in the radial direction with respect to the axis 50 of the annular sintered body 10. Therefore, the sintered body 10 is divided into two regions, ie, a circumferentially divided region 121 having a minor angle θ 1 and a circumferentially divided region 122 having a dominant angle θ 2 , and the polarization directions are opposite to each other in each region (121, 122). Direction. In addition, since the electric field strengths (E 1 , E 2 ) applied to the two circumferentially divided regions (121, 122) are inversely proportional to the distance in the circumferential direction between the electrodes for polarization (21-22), the minor angle θ 1 Corresponding circumferential divided regions 121 have higher polarization intensity.
そこで第１の実施例のように、二つの分極用電極（２１−２２）を用いて円環状焼結体１０を分極させる際に劣角θ１の円周分割領域１２１と優角θ２の円周分割領域１２２のそれぞれに印加される電界強度をシミュレーションによって求めてみた。図４にそのシミュレーションの概略と結果を示した。図４（Ａ）はシミュレーションに用いた焼結体１０のサイズを示す図であり、当該焼結体１０は円環の外径φ１＝１２ｍｍ、内径φ２＝７ｍｍ、厚さ（以下、ｔ１）＝０．４ｍｍの外形サイズを有し、二つの分極用電極（２１、２２）は、幅ｗ１＝２．０ｍｍで劣角θ１＝１２０°（優角θ２＝２４０°）となる位置に形成されている。また二つの分極用電極間（２１−２２）に電位差Ｖ＝１Ｖを与えることとしている。そしてこの電位差Ｖにより劣角θ１の円周分割領域１２１では円周に沿う所定の方向（ここでは時計回り）の電界Ｅ１が印加され、優角θ２の円周分割領域１２２では反時計回りの方向に電界Ｅ２が印加される。 Therefore, as in the first embodiment, when the annular sintered body 10 is polarized using two polarization electrodes (21-22), the circumferential divided region 121 of the minor angle θ 1 and the dominant angle θ 2 The electric field strength applied to each of the circumferential division regions 122 was obtained by simulation. FIG. 4 shows the outline and results of the simulation. FIG. 4A is a diagram showing the size of the sintered body 10 used in the simulation. The sintered body 10 has an annular outer diameter φ 1 = 12 mm, an inner diameter φ 2 = 7 mm, and a thickness (hereinafter, t 1 ) = 0.4 mm, and the two polarization electrodes (21, 22) have a width w 1 = 2.0 mm and an inferior angle θ 1 = 120 ° (major angle θ 2 = 240 °). It is formed in the position. In addition, a potential difference V = 1V is applied between the two polarization electrodes (21-22). Then, by this potential difference V, an electric field E 1 in a predetermined direction along the circumference (clockwise in this case) is applied in the circumferential divided region 121 having the subordinate angle θ 1 , and counterclockwise in the circumferential divided region 122 having the dominant angle θ 2. electric field E 2 is applied in the direction of rotation.
図４（Ｂ）は上述した条件に基づいて行ったシミュレーションの結果を示す図である。ここでは電位差Ｖによる分極に際して焼結体１０に印加される電界強度を濃淡で表している。劣角θ１および優角θ２のそれぞれに対応する円周分割領域（１２１、１２２）では、同心円上に沿って同じ強度の電界（Ｅ１、Ｅ２）が印加されており、外周（１２１ｏ、１２２ｏ）側より内周（１２１ｉ、１２２ｉ）側の電界強度が大きくなっている。具体的には劣角θ１の円周分割領域１２１における電界強度は、外周１２１ｏで８１．５Ｖ／ｍ、内周１２１ｉで１４０．０Ｖ／ｍとなる。一方優角θ２の円周分割領域１２２における電界強度は、外周１２２ｏで４０．１Ｖ／ｍ、内周１２２ｉで６６．８Ｖ／ｍとなる。なお上下方向の電界強度は分極用電極（２１、２２）の直下以外では一様に０Ａ／ｍであり、上下方向には分極されないことが分かった。以上より第１の実施例に係る方法によって、円環の周方向に分極させることができ、圧電歪１５モードで駆動可能な円環状圧電体が得られることが確認できた。 FIG. 4B is a diagram showing a result of a simulation performed based on the above-described conditions. Here, the electric field strength applied to the sintered body 10 upon polarization by the potential difference V is represented by shading. In the circumferential division regions (121, 122) corresponding to each of the minor angle θ 1 and the dominant angle θ 2 , electric fields (E 1 , E 2 ) having the same intensity are applied along the concentric circles, and the outer circumference (121o , 122o) side, the electric field strength on the inner circumference (121i, 122i) side is larger. Specifically, the electric field strength in the circumferential divisional region 121 with the minor angle θ 1 is 81.5 V / m at the outer periphery 121o and 140.0 V / m at the inner periphery 121i. On the other hand, the electric field strength in the circumferential division region 122 having the dominant angle θ 2 is 40.1 V / m at the outer periphery 122o and 66.8 V / m at the inner periphery 122i. It was found that the electric field strength in the vertical direction was uniformly 0 A / m except under the polarization electrodes (21, 22) and was not polarized in the vertical direction. From the above, it was confirmed that an annular piezoelectric body that can be polarized in the circumferential direction of the ring and can be driven in the piezoelectric strain 15 mode is obtained by the method according to the first embodiment.
＝＝＝第２の実施例＝＝＝
図３、図４に示したように、第１の実施例では二つの分極用電極（２１、２２）によって焼結体１０を円周に沿う方向に分極させていた。しかし二つの分極用電極（２１、２２）によって分極の方向や強度が異なる二つの円周分割領域（１２１、１２２）が形成されてしまう。そして焼結体１０を分極させた円環状圧電体の上下両面に駆動用電極を形成した圧電素子を駆動する際には、二つの円周分割領域（１２１、１２２）が協調して振動するように制御する必要がある。そこで第２の実施例として、円環状焼結体１０を全円周に亘って一方向に分極させるための手順を示す。
=== Second Embodiment ===
As shown in FIGS. 3 and 4, in the first embodiment, the sintered body 10 is polarized in the direction along the circumference by the two polarization electrodes (21, 22). However, two circumferential division regions (121, 122) having different polarization directions and intensities are formed by the two polarization electrodes (21, 22). Then, when driving the piezoelectric element in which the driving electrodes are formed on the upper and lower surfaces of the annular piezoelectric body in which the sintered body 10 is polarized, the two circumferential divided regions (121, 122) seem to vibrate in a coordinated manner. Need to control. Therefore, as a second embodiment, a procedure for polarizing the annular sintered body 10 in one direction over the entire circumference is shown.
図５に第２の実施例における分極手順を示した。まず図５（Ａ）に示したように、円環状焼結体１０に三つ以上の分極用電極（２１〜２４）を等角度間隔で形成する。この例ではθ＝９０°の角度ごとに四つの分極用電極（２１〜２４）を形成している。つぎに図５（Ｂ）に示したように、互いに隣接する二つの分極用電極（２１、２２）を選択し、その電極間（２１−２２）に電位差Ｖを与えて、当該二つの分極用電極間（２１−２２）の円周分割領域（１２１、１２２）を分極させる。ここでは劣角θ１＝９０゜に対応する円周分割領域１２１に時計回り方向の強電界Ｅ１が印加され、優角θ２＝２７０゜に対応する円周分割領域１２２に反時計回りの方向に弱い電界Ｅ２が印加される。ここで、このとき接地電位にした分極用電極２１を基準となる第１電極２１と称し、以下この第１電極２１に対して反時計回りにθ＝９０°ごとに形成されている分極用電極（２２〜２４）を順次第２電極２２、第３電極２３、および第４電極２４と称することとする。また円環状焼結体１０において、第１電極２１と第２電極２２との間の劣角θ１＝９０°に対応する円周分割領域を第１領域１２１１とし、以後反時計回りに角度９０°ごとに区切られた領域を第２〜第４領域（１２１２〜１２１４）とする。 FIG. 5 shows a polarization procedure in the second embodiment. First, as shown in FIG. 5A, three or more electrodes for polarization (21 to 24) are formed on the annular sintered body 10 at equal angular intervals. In this example, four polarization electrodes (21 to 24) are formed for each angle of θ = 90 °. Next, as shown in FIG. 5B, the two polarizing electrodes (21, 22) adjacent to each other are selected, and a potential difference V is given between the electrodes (21-22), so that the two polarizing electrodes are selected. Polarization is performed on the circumferentially divided regions (121, 122) between the electrodes (21-22). Here, a strong electric field E 1 in the clockwise direction is applied to the circumferential divided region 121 corresponding to the subordinate angle θ 1 = 90 °, and the counterclockwise rotation is applied to the circumferential divided region 122 corresponding to the dominant angle θ 2 = 270 °. weak electric field E 2 is applied in the direction. Here, the polarization electrode 21 brought to the ground potential at this time is referred to as a first electrode 21 serving as a reference. Hereinafter, the polarization electrode formed counterclockwise with respect to the first electrode 21 every θ = 90 °. (22 to 24) will be sequentially referred to as the second electrode 22, the third electrode 23, and the fourth electrode 24. In the annular sintered body 10, a circumferentially divided region corresponding to the recessive angle θ 1 = 90 ° between the first electrode 21 and the second electrode 22 is defined as the first region 1211, and thereafter the angle 90 is counterclockwise. The regions divided every degree are defined as second to fourth regions (1212 to 1214).
そして第１領域１２１１とその優角θ２に対応する領域１２２を分極したら、図５（Ｃ）に示したように、第３電極２３を高電位にして第２電極２２との間に電位差Ｖを与え、第２領域１２１２に時計回りの電界Ｅ１を印加する。もちろんこの場合も優角θ２に対応する領域１２２に反時計回りの電界Ｅ２（＜Ｅ１）が印加される。つぎに図５（Ｄ）（Ｅ）に示したように、同様にして第３領域１２１３と第４領域１２１４に時計回りの電界Ｅ１を順次印加する。そしてこの時点で第１〜第４領域（１２１１〜１２１４）は、各領域（１２１１〜１２１４）に印加された時計回りの強い電界Ｅ１と、これらの領域（１２１１〜１２１４）において優角θ２に対応する領域１２２に印加された反時計回りの弱い電界Ｅ２との差分に相当する時計回りの電界によって分極される。すなわち図５（Ｅ）に示したように、第１〜第４領域（１２１１〜１２１４）が同じ方向に同じ強度Ｐで分極される。すなわち全円周に亘って同方向に分極された円環状圧電体１１が作製される。 When the first region 1211 and the region 122 corresponding to the dominant angle θ 2 are polarized, the potential difference V between the second electrode 22 and the third electrode 23 is set high as shown in FIG. And a clockwise electric field E 1 is applied to the second region 1212. Of course, also in this case, a counterclockwise electric field E 2 (<E 1 ) is applied to the region 122 corresponding to the dominant angle θ 2 . Next, as shown in FIG. 5 (D) (E), sequentially applying an electric field E 1 clockwise in the third area 1213 and the fourth region 1214 in the same manner. The first to fourth regions at this time (1211 to 1214) includes a strong electric field E1 of the applied clockwise to the respective regions (1211-1214), the reflex angle theta 2 in these regions (1211-1214) It is polarized by a clockwise electric field corresponding to the difference from the counterclockwise weak electric field E 2 applied to the corresponding region 122. That is, as shown in FIG. 5E, the first to fourth regions (1211 to 1214) are polarized with the same intensity P in the same direction. That is, an annular piezoelectric body 11 that is polarized in the same direction over the entire circumference is produced.
なお図５に示した分極手順では円周に沿って一方向に順番に二つの分極用電極（２１〜２４）を選択し、劣角θ１に対応する第１〜第４領域（１２１１〜１２１４）とその優角θ２に対応する円周分割領域１２２を順番に分極していたが、例えば第１領域１２１１に続いて第３領域１２１３を分極するなど円周に沿って順番に分極させる必要は無い。また各領域（１２１１〜１２１４）の分極回数は１回ずつでなくてもよい。いずれにしても各領域（１２１１〜１２１４）の分極回数が同じであればよい。もちろん分極用電極の数は四つに限らない。 In the polarization procedure shown in FIG. 5, two polarization electrodes (21 to 24) are sequentially selected in one direction along the circumference, and the first to fourth regions (1211 to 1214) corresponding to the minor angle θ 1 are selected. ) And the circumferential divided region 122 corresponding to the dominant angle θ 2 are sequentially polarized. For example, the third region 1213 needs to be sequentially polarized along the circumference, for example, by polarizing the third region 1213. There is no. In addition, the number of polarizations of each region (1211-1214) may not be one. In any case, the number of polarizations in each region (1211-1214) may be the same. Of course, the number of polarization electrodes is not limited to four.
＝＝＝＝第３の実施例＝＝＝
第１および第２の実施例では、円環状焼結体を放射方向に連続して延長しつつ所定の角度を介して離間する二つの分極用電極間を用いて分極させていた。そのため図４にも示したように、焼結体１０の内周側から外周側に向かって（１２１ｉ→１２１ｏ、１２２ｉ→１２２ｏ）電界強度（Ｅ１、Ｅ２）が円環の軸５０からの距離に反比例して強くなっていく。そのため円環状焼結体の径方向の幅が広い場合、内周側と外周側に印加される電界強度の差が大きくなる。そこで円環状焼結体の外周側と内周側とに印加される電界強度の差を小さくできる分極手順を本発明の第３の実施例として挙げる。
==== Third embodiment ===
In the first and second embodiments, the annular sintered body is polarized between two electrodes for polarization that are separated from each other by a predetermined angle while continuously extending in the radial direction. Therefore, as shown also in FIG. 4, the electric field strength (E 1 , E 2 ) from the annular shaft 50 from the inner peripheral side of the sintered body 10 toward the outer peripheral side (121i → 121o, 122i → 122o) It becomes stronger in inverse proportion to the distance. Therefore, when the radial width of the annular sintered body is wide, the difference in electric field strength applied between the inner peripheral side and the outer peripheral side becomes large. Therefore, a polarization procedure capable of reducing the difference in electric field strength applied between the outer peripheral side and the inner peripheral side of the annular sintered body will be described as a third embodiment of the present invention.
図６に第３の実施例における分極手順の概略を示した。図６に示したように、ここでは放射方向に延長する分極用電極（２１〜２４）が９０゜の角度間隔ごとに配置し、各分極用電極（２１〜２４）をさらに所定の半径ｒとなる位置で分割している。この例では、内周の半径ｒｉと外周の半径ｒｏとの中間の半径ｒを有する同心円１６上で分割している。それによって一つの分極用電極（２１〜２４）に外周側の分極用電極（以下、外周側分極用電極２１ｏ〜２４ｏとも言う）と内周側の分極用電極（以下、内周側分極用電極２１ｉ〜２４ｉとも言う）が形成される。 FIG. 6 shows an outline of the polarization procedure in the third embodiment. As shown in FIG. 6, here, polarization electrodes (21 to 24) extending in the radial direction are arranged at an angular interval of 90 °, and each polarization electrode (21 to 24) is further set to a predetermined radius r. It is divided at the position. In this example, it is divided on a concentric circle 16 having a radius r intermediate between an inner radius r i and an outer radius r o . As a result, an outer-polarization electrode (hereinafter also referred to as outer-polarization electrodes 21o to 24o) and an inner-polarization electrode (hereinafter referred to as inner-polarization electrode) are added to one polarization electrode (21-24). 21i-24i) is formed.
そしてこれらの内周側と外周側の分極用電極（２１ｉ〜２４ｉ、２１ｏ〜２１ｏ）を用いて円環状焼結体１０を分極させる際には、例えば、図中で示したように互いに隣接する分極用電極（２１、２２）を用いるのであれば、外周側分極用電極（２１ｏ、２２ｏ）で区切られた外周側の円周分割領域１２１ｏに印加される電界強度Ｅｏと内周側分極用電極（２１ｉ、２２ｉ）で区切られた内周側の円周分割領域１２１ｉに印加される電界強度Ｅｉが同じになるように、外周側と内周側のそれぞれにおいて互いに隣接する二つの分極電極間（２１ｉ−２２ｉ、２１ｏ―２２ｏ）の電位差Ｖ１とＶ２を調整する。 When the annular sintered body 10 is polarized using the inner and outer peripheral polarization electrodes (21i to 24i, 21o to 21o), for example, they are adjacent to each other as shown in the figure. If the polarization electrodes (21, 22) are used, the electric field intensity Eo applied to the outer circumferential side divided region 121o divided by the outer circumferential side polarization electrodes (21o, 22o) and the inner circumferential side polarization electrode (Between two polarization electrodes adjacent to each other on the outer peripheral side and the inner peripheral side so that the electric field strength Ei applied to the inner peripheral circumferential divided region 121i divided by (21i, 22i) is the same ( 21i-22i, to adjust the potential difference V 1 and V 2 of 21o-22o).
＝＝＝第４の実施例＝＝＝
上記第１〜第３の実施例では分極用電極を円環状焼結体の表面（ここでは上面）に形成していた。そのため分極用電極の直下では、図４（Ｂ）にも示したように上下方向にも電界が印加され、分極用電極の形成領域では上下方向の分極成分が残存する。その結果、圧電歪１５モードでの振動効率が低下する可能性がある。そこ円環状焼結体を周方向に一様に分極させる手順を第４の実施例として以下に説明する。図７に第４の実施例における分極手順の概略を示した。図７（Ａ）は円環状焼結体１０を上方から見たときの平面図である。ここでは４つの分極用電極２０がθ＝９０゜の角度間隔ごとに形成されている例を示した。図７の（Ｂ）と（Ｃ）は、ともに図７（Ａ）におけるａ−ａ斜視断面を示している。なお図７の（Ｂ）と（Ｃ）では分極用電極２０の構成が異なっている。
=== Fourth embodiment ===
In the first to third embodiments, the polarization electrode is formed on the surface (here, the upper surface) of the annular sintered body. Therefore, immediately below the polarization electrode, an electric field is also applied in the vertical direction as shown in FIG. 4B, and the vertical polarization component remains in the formation region of the polarization electrode. As a result, vibration efficiency in the piezoelectric strain 15 mode may be reduced. A procedure for uniformly polarizing the annular sintered body in the circumferential direction will be described below as a fourth embodiment. FIG. 7 shows an outline of the polarization procedure in the fourth embodiment. FIG. 7A is a plan view when the annular sintered body 10 is viewed from above. Here, an example is shown in which four polarization electrodes 20 are formed at an angle interval of θ = 90 °. FIGS. 7B and 7C both show an aa perspective cross section in FIG. 7B and 7C, the configuration of the polarization electrode 20 is different.
第４の実施例では、そして図７の（Ｂ）と（Ｃ）に示したように、焼結体１０の上面１２おいて分極用電極２０が形成される位置に溝１３が形成されている。そしてその溝１３内に導電体（１２０ａ、１２０ｂ）を埋め込み、その導電体（１２０ａ、１２０ｂ）を分極用電極２０としている。なお図７（Ｂ）に示した例では、ブロック状の金属などからなる導電体１２０ａを溝１３内に嵌め込んで、上端が焼結体１０の上面１２から突出している。図７（Ｃ）に示した例では、溝１３内に導電体２０ｂとして銀ペーストを充填している。このように第４の実施例では焼結体１０の厚さ方向にも分極用電極２０を形成することで分極用電極２０の形成領域における上下方向の電界強度を低減させている。 In the fourth embodiment, and as shown in FIGS. 7B and 7C, the groove 13 is formed at the position where the polarization electrode 20 is formed on the upper surface 12 of the sintered body 10. . Then, conductors (120a, 120b) are embedded in the groove 13, and the conductors (120a, 120b) are used as the polarization electrodes 20. In the example shown in FIG. 7B, a conductor 120a made of block-like metal or the like is fitted into the groove 13, and the upper end protrudes from the upper surface 12 of the sintered body 10. In the example shown in FIG. 7C, the groove 13 is filled with a silver paste as the conductor 20b. As described above, in the fourth embodiment, by forming the polarization electrode 20 also in the thickness direction of the sintered body 10, the electric field strength in the vertical direction in the region where the polarization electrode 20 is formed is reduced.
＝＝＝第５の実施例＝＝＝
上記第１〜第４の実施例では、周囲が連続する円環状焼結体に形成した二つの分極用電極を用いて当該焼結体を分極していた。そのため優角に対応する円周分割領域と劣角に対応する円周分割領域のそれぞれに互いに逆方向の電界が印加されていた。すなわち分極用電極間の電位差を用いて効率よく分極させることが難しかった。そこで第５の実施例としており効率よく分極させるための手順を挙げる。
=== Fifth embodiment ===
In the first to fourth embodiments, the sintered body is polarized using two polarization electrodes formed in an annular sintered body having a continuous periphery. For this reason, electric fields in opposite directions are applied to each of the circumferential divided region corresponding to the dominant angle and the circumferential divided region corresponding to the minor angle. That is, it has been difficult to efficiently polarize using the potential difference between the electrodes for polarization. Therefore, the fifth embodiment is described as a procedure for efficiently polarizing.
図８は第５の実施例における分極手順の概略を示す図である。図８（Ａ）は第５の実施例に用いる円環状焼結体１０の外観を示す図であり、図８（Ｂ）は図８（Ａ）に示した円環状焼結体１０を分極させるときの電界の印加状態を示す図である。そして図８（Ａ）に示したように、円環状焼結体１０ｂは、その一部に切欠部１４が形成されており、この切欠が円環状焼結体１０に印加される電界を遮断するギャップとして機能する。図８（Ｂ）に示したように、円環状焼結体１０に形成された二つの分極用電極間（２０−２０）に電位差Ｖを与えたとき、切欠部（以下、ギャップ１４）を含む円周分割領域１２２では電界Ｅ２が遮断される。それによって一方向にのみ電界Ｅ１が印加され、効率的に円環状焼結体１０を分極させることができる。 FIG. 8 is a diagram showing an outline of the polarization procedure in the fifth embodiment. FIG. 8A is a view showing the appearance of the annular sintered body 10 used in the fifth embodiment, and FIG. 8B is a diagram for polarizing the annular sintered body 10 shown in FIG. 8A. It is a figure which shows the application state of the electric field at the time. As shown in FIG. 8A, the annular sintered body 10b has a notch 14 formed in a part thereof, and the notch blocks an electric field applied to the annular sintered body 10. Acts as a gap. As shown in FIG. 8B, when a potential difference V is applied between two polarization electrodes (20-20) formed on the annular sintered body 10, a notch (hereinafter referred to as a gap 14) is included. field E 2 in the circumferential divided area 122 is cut off. It field E 1 only in one direction is applied by, can be efficiently polarizing the annular sintered body 10.
なお第５の実施例では、円環状焼結体の一部にギャップ１４が設けられているため、当該焼結体１０が薄い場合などでは強度不足が懸念される。そのような場合にはギャップ１４内に樹脂などの絶縁体を充填して補強すればよい。 In the fifth embodiment, since the gap 14 is provided in a part of the annular sintered body, there is a concern that the strength is insufficient when the sintered body 10 is thin. In such a case, the gap 14 may be reinforced by filling an insulator such as resin.
＝＝＝圧電特性＝＝＝
＜サンプル＞
上述した第１〜第５の実施例における方法によって製造される円環状圧電素子の特性を評価するために、上記各実施例の分極手順で得た円環状圧電体をサンプルとして作製した。ここで第１〜第５の実施例に対応するサンプルを順にサンプルａ〜ｅとする。また第５の実施例によって得た環状圧電体のギャップに樹脂を充填したサンプルをサンプルｆとして作製した。そして各サンプルの圧電特性を調べた。なお各サンプルの作製手順は分極の手順以外は一般的な圧電体の製造手順と同じである。
=== Piezoelectric properties ===
<Sample>
In order to evaluate the characteristics of the annular piezoelectric element manufactured by the method in the first to fifth embodiments described above, an annular piezoelectric body obtained by the polarization procedure of each of the above embodiments was prepared as a sample. Here, samples corresponding to the first to fifth embodiments are sequentially referred to as samples a to e. A sample in which a resin was filled in the gap of the annular piezoelectric body obtained in the fifth example was prepared as sample f. The piezoelectric characteristics of each sample were examined. The procedure for producing each sample is the same as that for manufacturing a general piezoelectric body except for the polarization procedure.
＜サンプルの作製手順＞
図９にサンプルの作製手順を示した。図９に示したように、まず圧電材料をリング状に形成する。具体的にはＰＬＺＴなどの圧電材料を粉末状にした原材料をバインダを添加した上で型を用いて円環状の成形体にする。あるいは粉末状の原材料にバインダを添加してスラリー状にしたものを圧膜印刷技術により円環状の成形体にする（ｓ１）。第４および５の実施例に対応するサンプルｅ、サンプルｆについては、この成形工程（ｓ１）において溝やギャップを形成しておく。もちろん円環状焼結体に成形したあとにダイサーなどを用いた機械加工によって溝やギャップを形成してもよい。
<Sample preparation procedure>
FIG. 9 shows a sample manufacturing procedure. As shown in FIG. 9, first, a piezoelectric material is formed in a ring shape. Specifically, a raw material in which a piezoelectric material such as PLZT is powdered is added with a binder, and an annular molded body is formed using a mold. Alternatively, a powdery raw material added with a binder to form a slurry is formed into an annular shaped body by a pressure film printing technique (s1). For samples e and f corresponding to the fourth and fifth embodiments, grooves and gaps are formed in this forming step (s1). Of course, after forming into an annular sintered body, grooves and gaps may be formed by machining using a dicer or the like.
つぎに円環状に成形した圧電材料を３００℃〜５００℃の温度で１〜５時間程度加熱してバインダ成分が残渣しないよう完全に脱脂する（ｓ２）。そして１０００℃〜１３００℃の温度で成形体を焼成し、相対密度９５％以上の緻密化されたセラミックからなる円環状焼成体を作製する（ｓ３）。ついで上記第１〜第５の実施例のそれぞれの分極手順に応じて位置や形状が異なる分極用電極を円環状焼結体に設ける。なお分極用電極は、溝内に分極用電極を形成する第４の実施例に対応するサンプルｄ以外のサンプルでは、電極板を円環状焼結体の表面に接触させることで設ける（ｓ４→ｓ５）。サンプルｄについては溝内に銀ペーストを充填した後、これを加熱して溝内に焼き付けることで分極用電極を設けた（ｓ４→ｓ１０）。最後に分極用電極を用いて円環状焼成体に電界を印加して分極させる（ｓ５→ｓ６、ｓ１０→ｓ６）。分極時に二つの分極用電極間に電圧を印加する際には、分極させたい方向に平均して１ｋＶ／ｍの強度の電界が印加されるようにする。そして円環状焼結体の全周にわたって分極させれば円環状圧電体が完成する（ｓ７→ｓ８→終わり）。サンプルｄについては、分極後に溶剤を用いたり機械的に研磨したりするなどして銀ペーストからなる分極電極を除去した（ｓ７→ｓ８→ｓ９→終わり）。 Next, the annularly shaped piezoelectric material is heated at a temperature of 300 ° C. to 500 ° C. for about 1 to 5 hours to completely degrease the binder component so as not to remain (s2). And a molded object is baked at the temperature of 1000 to 1300 degreeC, and the annular | circular shaped sintered body which consists of a densified ceramic with a relative density of 95% or more is produced (s3). Next, polarization electrodes having different positions and shapes are provided on the annular sintered body in accordance with the polarization procedures of the first to fifth embodiments. Note that the polarization electrode is provided by bringing the electrode plate into contact with the surface of the annular sintered body (s4 → s5) in samples other than the sample d corresponding to the fourth embodiment in which the polarization electrode is formed in the groove. ). For sample d, after filling the groove with a silver paste, this was heated and baked into the groove to provide a polarizing electrode (s4 → s10). Finally, an electric field is applied to the annular fired body using the polarization electrode to polarize it (s5 → s6, s10 → s6). When a voltage is applied between two polarization electrodes during polarization, an electric field having an intensity of 1 kV / m on average is applied in the direction in which the polarization is desired. If the entire circumference of the annular sintered body is polarized, an annular piezoelectric body is completed (s7 → s8 → end). For sample d, the polarization electrode made of silver paste was removed by using a solvent or mechanically polishing after polarization (s7 → s8 → s9 → end).
＜評価用素子について＞
上述した手順によって作製した各サンプルの圧電特性を測定するために、サンプルの一部を試料片として切り出し、その切り出した矩形平板状の試料片の表裏に特性評価用の電極を形成した。図１０に各サンプルの外形や試料片についての概略を示した。具体的には、図１０（Ａ）〜（Ｆ）のそれぞれに、サンプルａ〜ｆの外形やサンプル片の形状や切り出位置、および分極時の分極用電極の位置や形状を示した。各サンプルの外形は図１０（Ｃ）に示したサンプルｃが外径φ１＝５０ｍｍ、内径φ２＝２０ｍｍ であり、図１０（Ａ）（Ｂ）（Ｄ）〜（Ｆ）に示した他のサンプルａ、ｂ、ｄ〜ｆは外径φ１＝５０ｍｍ、内径φ２＝４０ｍｍである。厚さｔ１は全てのサンプルで０．２ｍｍである（図１０（Ｄ）参照）。分極用電極２０の幅ｗ１は各サンプル共通でｗ１＝２ｍｍである。
<About the evaluation element>
In order to measure the piezoelectric characteristics of each sample produced by the above-described procedure, a part of the sample was cut out as a sample piece, and electrodes for characteristic evaluation were formed on the front and back of the cut out rectangular flat sample piece. FIG. 10 shows an outline of the outer shape of each sample and the sample piece. Specifically, in each of FIGS. 10A to 10F, the outer shape of the samples a to f, the shape and cutting position of the sample piece, and the position and shape of the electrode for polarization during polarization are shown. As for the outer shape of each sample, the sample c shown in FIG. 10 (C) has an outer diameter φ1 = 50 mm and an inner diameter φ2 = 20 mm. Other samples shown in FIGS. 10 (A), (B), (D) to (F) a, b, and d to f have an outer diameter φ1 = 50 mm and an inner diameter φ2 = 40 mm. The thickness t 1 is 0.2 mm for all the samples (see FIG. 10D). The width w1 of the polarization electrode 20 is w 1 = 2 mm common to the samples.
また図１０（Ｃ）に示したサンプルｃについては、内周から外周までの円環の幅ｗ３を二等分する半径φ３＝３５ｍｍの同心円１６によって内周側分極用電極２０ｉと外周側分極用電極２０ｏに分割され、内周側分極用電極２０ｉと外周側分極用電極２０ｏとの間には幅ｗ４＝０．５ｍｍの間隙が介在している。図１０（Ｄ）に示したサンプルｄは表面に溝が形成されており、このサンプルｄは図１０（Ｂ）に示したサンプルｂの分極用電極２０が配置される位置に深さｄ＝２ｍｍの溝１３が形成されて、その溝１３内に分極用電極２０として厚さｔ２＝１ｍｍの銀ペースト１２０ｂが充填されている。 The Figure for the sample c shown in 10 (C), the inner circumferential inner circumferential side polarizing electrode 20i and the outer periphery side polarization by a radius .phi.3 = 35 mm concentric 16 the width w 3 of the ring to the outer periphery bisecting from The electrode is divided into electrodes for use 20o, and a gap with a width w 4 = 0.5 mm is interposed between the inner periphery side polarization electrode 20i and the outer periphery side polarization electrode 20o. The sample d shown in FIG. 10D has a groove formed on the surface, and this sample d has a depth d = 2 mm at the position where the polarization electrode 20 of the sample b shown in FIG. The groove 13 is formed, and the groove 13 is filled with a silver paste 120b having a thickness t 2 = 1 mm as the polarization electrode 20.
分極用電極２０の配置については、図１０（Ａ）に示したサンプルａでは１２０゜の角度間隔を隔てて二つの分極用電極２０を設けているが、図１０（Ｂ）〜（Ｄ）に示したサンプルｂ〜ｄでは９０゜の角度ごとに４カ所に分極用電極２０を設けている。図１０の（Ｅ）と（Ｆ）のそれぞれに示したサンプルｅとサンプルｆでは、ギャップ１４の両側に他と同様の幅ｗ１＝２ｍｍの分極用電極２０ｇが形成されているとともに、ギャップ１４の形成位置から９０゜の角度ごとに３カ所に分極用電極２０が設けられている。 With respect to the arrangement of the polarization electrodes 20, in the sample a shown in FIG. 10 (A), two polarization electrodes 20 are provided with an angular interval of 120 °, but in FIGS. 10 (B) to (D). In the samples b to d shown, polarization electrodes 20 are provided at four positions every 90 °. In the sample e and the sample f shown in FIGS. 10E and 10F, the polarization electrodes 20g having the same width w 1 = 2 mm are formed on both sides of the gap 14, and the gap 14 Polarizing electrodes 20 are provided at three positions at an angle of 90 ° from the formation position.
そして図１０の（Ａ）、（Ｂ）、（Ｃ）、（Ｅ）および（Ｆ）に示したように、各サンプルについて所定の位置から長さＬ＝１０ｍｍ、幅ｗ２＝２．５ｍｍの試験片２００を分極後の円環状焼結体１０の厚さｔ１＝０．２ｍｍにわたって切り出した。図１０（Ｄ）に示したサンプルｄは図１０（Ｂ）に示したサンプルｂと同じ位置から試験片２００を切り出した。そして各サンプルの特性を評価するために切り出した試験片２００の上面と下面に塗布した銀ペーストを焼き付けてなる電極を形成して圧電素子（以下、評価用素子とも言う）を作製した。図１１に評価用素子２２０の概略を示した。サンプルａ〜ｆから切り出した矩形平板状の試験片２００の上下両面に電極２１０を形成している。そして評価用素子２２０における分極方向Ｐは矩形の平面形状における長辺方向に分極している。また各サンプルとの特性を比較するための基準となる試料として試験片２００と同じ大きさの焼結体を分極させてなる圧電素子（以下、比較用素子とも言う）も用意した。図１２に比較用素子の作製手順の概略を示した。試験片と同じ矩形平面形状を有する焼結体３１０の短辺側の端面に分極用電極３２０を形成し、この電極間（３２０−３２０）間に与えた電位差Ｖによって焼結体３１０の長辺方向に電界Ｅを印加して分極させる。そして分極用電極３２０を除去し、評価用素子と同様に分極後の焼結体３１０の上下両面に電極を形成して比較用素子を完成させた。 And as shown to (A), (B), (C), (E) and (F) of FIG. 10, each sample has a length L = 10 mm and a width w 2 = 2.5 mm from a predetermined position. The test piece 200 was cut out over the thickness t 1 = 0.2 mm of the annular sintered body 10 after polarization. In the sample d shown in FIG. 10D, the test piece 200 was cut out from the same position as the sample b shown in FIG. And the electrode formed by baking the silver paste apply | coated to the upper surface and lower surface of the test piece 200 cut out in order to evaluate the characteristic of each sample was formed, and the piezoelectric element (henceforth the element for evaluation) was produced. FIG. 11 shows an outline of the evaluation element 220. Electrodes 210 are formed on both upper and lower surfaces of a rectangular flat test piece 200 cut out from samples a to f. The polarization direction P in the evaluation element 220 is polarized in the long side direction in the rectangular planar shape. In addition, a piezoelectric element (hereinafter also referred to as a comparative element) obtained by polarizing a sintered body having the same size as that of the test piece 200 was prepared as a reference sample for comparing characteristics with each sample. FIG. 12 shows an outline of a procedure for manufacturing a comparative element. The electrode 320 for polarization is formed on the end surface on the short side of the sintered body 310 having the same rectangular planar shape as the test piece, and the long side of the sintered body 310 is generated by the potential difference V applied between the electrodes (320-320). Polarization is performed by applying an electric field E in the direction. Then, the polarization electrode 320 was removed, and electrodes were formed on both the upper and lower surfaces of the sintered body 310 after polarization in the same manner as the evaluation element to complete the comparative element.
＜特性評価＞
上述したように作製した各サンプルａ〜ｆに対応する評価用素子と比較用素子の圧電特性を調べた。以下の表１に各サンプルの圧電特性を示した。
<Characteristic evaluation>
The piezoelectric characteristics of the evaluation element and the comparison element corresponding to the samples a to f manufactured as described above were examined. Table 1 below shows the piezoelectric characteristics of each sample.
そして表１に示したように、評価用素子ａ〜ｆのｋ１５はいずれも比較用素子の８０％以上の値を有し、充分に実用的な特性を有している。しかもＱｍについては全ての評価用素子で比較用素子を上回っている。またεｒ １１についてはほぼ同等の特性が得られた。以上により本発明の実施例に係る方法では圧電歪１５モードで駆動する実用的な円環状圧電素子をより安価に製造することが可能となる。 As shown in Table 1, each of k 15 of the evaluation elements a to f has a value of 80% or more of the comparative element and has sufficiently practical characteristics. Moreover, with respect to Qm, all the evaluation elements exceed the comparison elements. In addition, almost the same characteristics were obtained for ε r 11 . As described above, in the method according to the embodiment of the present invention, a practical annular piezoelectric element that is driven in the piezoelectric strain 15 mode can be manufactured at a lower cost.
１，１００ 円環状圧電素子、１０ 円環状セラミックス焼結体、１１ 円環状圧電体、１３ 溝 １４ ギャップ、１５ 補強材、
２０，２１〜２４，２０ｇ，１２０，３２０ 分極用電極、３０，１３０ 駆動用電極、
２０ｉ，２１ｉ〜２４ｉ 内周側分極用電極、
２０ｏ，２１ｏ〜２４ｏ 外周側分極用電極、１１０ 扇状焼結体、
１１１ 扇状圧電体、１２１，１２２，１２１１〜１２１４ 円周分割領域、
２００ 試験片、２２０ 評価用素子
1,100 annular piezoelectric element, 10 annular ceramic sintered body, 11 annular piezoelectric body, 13 groove, 14 gap, 15 reinforcing material,
20, 21 to 24, 20 g, 120, 320 Polarizing electrode, 30, 130 Driving electrode,
20i, 21i to 24i inner circumferential side polarization electrodes,
20o, 21o to 24o outer circumferential side polarization electrode, 110 fan-shaped sintered body,
111 fan-shaped piezoelectric bodies, 121, 122, 1211-1214 circumferentially divided regions,
200 test piece, 220 evaluation element
Claims (6)
円環の軸方向を上下方向として、
圧電材料からなる一体的な円環状セラミック焼結体を成形する焼結体成形ステップと、 前記円環状セラミックス焼結体の上面に半径方向に延長する分極用電極を複数箇所に配置する電極配置ステップと、
前記複数箇所に配置された分極用電極のうち、互いに隣り合う二つの電極の一方を接地電極として当該二つの電極間に電位差を与えることで、前記円環状セラミック焼結体において当該二つの分極用電極によって区分される円周分割領域を円周方向に向かって分極させる分極ステップと、
を含むことを特徴とする円環状圧電素子の製造方法。 An electrode is formed on the front and back of an annular piezoelectric body, and when an electric field is applied between the electrodes, a method of manufacturing an annular piezoelectric element that vibrates in a piezoelectric strain 15 mode,
With the axial direction of the ring as the vertical direction,
A sintered body forming step for forming an integral annular ceramic sintered body made of a piezoelectric material, and an electrode arrangement step for arranging polarization electrodes extending in the radial direction on the upper surface of the annular ceramic sintered body at a plurality of locations. When,
Among the electrodes for polarization arranged at the plurality of locations, one of two electrodes adjacent to each other is used as a ground electrode, and a potential difference is applied between the two electrodes, so that the two electrodes for polarization in the annular ceramic sintered body A polarization step that polarizes a circumferentially divided region divided by the electrodes in a circumferential direction;
The manufacturing method of the annular | circular shaped piezoelectric element characterized by including these.
前記電極配置ステップでは、分極用電極を配置する角度位置を３カ所以上とし、
前記分極ステップでは、互いに隣り合う二つの分極電極を順次選択するとともに、当該二つの分極用電極の延長方向がなす劣角側の円周分割領域を円周の所定方向に向かって分極させる、
ことを特徴とする円環状圧電素子の製造方法。 In claim 1,
In the electrode arrangement step, the angular position where the electrode for polarization is arranged is 3 or more,
In the polarization step, the two polarization electrodes adjacent to each other are sequentially selected, and the circumferential divided region on the minor angle side formed by the extension direction of the two polarization electrodes is polarized in a predetermined direction of the circumference.
A manufacturing method of an annular piezoelectric element characterized by the above.
前記電極配置ステップでは、前記円環状セラミック焼結体の半径方向に延長する前記分極用電極体が、所定の半径となる位置にて分割されて、内周側から外周側に向かって複数の分極電極片が形成され、
前記分極ステップでは、同じ半径となる領域に形成されて互いに周方向で隣接する二つの前記分極用電極片を選択するともに、選択した二つの分極用電極片が属する分極用電極の延長方向がなす劣角側の円周分割領域に同じ強度の電界が印加されるように電位差を与える、
ことを特徴とする円環状圧電素子の製造方法。 In claim 1 or 2,
In the electrode arrangement step, the polarization electrode body extending in the radial direction of the annular ceramic sintered body is divided at a position having a predetermined radius, and a plurality of polarizations are performed from the inner circumference side toward the outer circumference side. An electrode piece is formed,
In the polarization step, two polarization electrode pieces that are formed in a region having the same radius and are adjacent to each other in the circumferential direction are selected, and an extension direction of the polarization electrode to which the two selected polarization electrode pieces belong is defined. Giving a potential difference so that an electric field of the same strength is applied to the circumferentially divided region on the minor angle side,
A manufacturing method of an annular piezoelectric element characterized by the above.
前記焼結体成形ステップでは、上面に半径方向に延長する溝が形成された円環状セラミックス焼結体を成形し、
前記分極用電極配置ステップでは、前記溝内に導電体を配置する、
ことを特徴とする円環状圧電素子の製造方法。 In any one of Claims 1-3,
In the sintered body forming step, an annular ceramic sintered body in which grooves extending in the radial direction are formed on the upper surface is formed,
In the polarization electrode placement step, a conductor is placed in the groove.
A manufacturing method of an annular piezoelectric element characterized by the above.
前記焼結体成形ステップでは、半径方向を横断する切欠が形成された円環状セラミックス焼結体を形成し、
前記分極ステップでは、前記切欠をギャップとすることで、前記円環状セラミックス焼結体を周の一方向にのみ分極させる、
ことを特徴とする円環状圧電素子の製造方法。 In claims 1 to 4,
In the sintered body forming step, an annular ceramic sintered body in which a notch traversing the radial direction is formed is formed,
In the polarization step, the annular ceramic sintered body is polarized only in one circumferential direction by setting the notch as a gap.
A manufacturing method of an annular piezoelectric element characterized by the above.
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