JP2014081313A - Piezoelectric sensor vibrator for ultrasonic viscometer, and ultrasonic viscometer using the same - Google Patents
Piezoelectric sensor vibrator for ultrasonic viscometer, and ultrasonic viscometer using the same Download PDFInfo
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本発明は、圧電振動子を用いて液体の粘度を測定することが可能な超音波粘度計に関し、特に、導電性を有する液体の粘度、及び導電率を極微小量の試料を用いて測定することが可能な超音波粘度計用圧電センサ振動子、及びこれを用いた超音波粘度計に関する。 The present invention relates to an ultrasonic viscometer capable of measuring the viscosity of a liquid using a piezoelectric vibrator, and in particular, measures the viscosity and conductivity of a conductive liquid using a very small amount of sample. The present invention relates to a piezoelectric sensor vibrator for an ultrasonic viscometer, and an ultrasonic viscometer using the same.
液体の粘度を測定するために、回転式粘度計が一般的に広く使用されている。これに対して、測定が容易で比較的少量の試料により粘度の測定が可能な、超音波振動子を用いたいろいろなタイプの超音波粘度計が提案されており、その測定原理も非特許文献1に示されているようにほぼ解明されている。
超音波粘度計に用いられる圧電振動子には板状の圧電素子(以下、圧電板という)が用いられ、主要な振動変位が圧電板の面に平行である必要があり、圧電板の対向する二つの面が、面に平行な方向に互いに逆向きに変位する厚みすべり振動モードや、薄い圧電円板の直径が伸縮するように変位する面拡がり振動モードなどが利用されている。
A rotary viscometer is generally widely used to measure the viscosity of a liquid. On the other hand, various types of ultrasonic viscometers using ultrasonic transducers that can be measured easily and can measure viscosity with a relatively small amount of sample have been proposed. As shown in Figure 1, it is almost elucidated.
The piezoelectric vibrator used in the ultrasonic viscometer uses a plate-like piezoelectric element (hereinafter referred to as a piezoelectric plate), and the main vibration displacement needs to be parallel to the surface of the piezoelectric plate. A thickness shear vibration mode in which two surfaces are displaced in directions opposite to each other in a direction parallel to the surface, a surface expansion vibration mode in which the diameter of a thin piezoelectric disk is expanded or contracted, and the like are used.
特許文献1には、厚みすべり振動子を用いた粘弾性評価用弾性振動センサが開示されている。ここで用いられている圧電センサ振動子は、図1に示すように、XカットLiTiO3の単結晶からなる短冊状圧電板の両面に、長さ方向の中央部で対向し、互いに異なる端部に引き出された電極が形成されている。
図1に示された圧電センサ振動子の寸法は、共振周波数を4MHzとした場合であり、共振周波数を高くすることにより、さらに小形にすることも可能である。
Patent Document 1 discloses an elastic vibration sensor for evaluating viscoelasticity using a thickness shear vibrator. As shown in FIG. 1, the piezoelectric sensor vibrator used here is opposite to each other at both sides of a strip-shaped piezoelectric plate made of a single crystal of X-cut LiTiO 3 at the center in the length direction. The electrode led out is formed.
The dimensions of the piezoelectric sensor vibrator shown in FIG. 1 are those when the resonance frequency is 4 MHz, and can be further reduced in size by increasing the resonance frequency.
図1の圧電センサ振動子の互いに異なる端部に引き出された電極にリード線を取り付け、図2に示すように、液体試料中に浸漬したときの圧電センサ振動子の共振抵抗の変化あるいは共振周波数の変化のいずれか、または、両方の特性から試料液体の粘弾性特性を求めることができる。 Changes in the resonance resistance or resonance frequency of the piezoelectric sensor vibrator when immersed in a liquid sample as shown in FIG. 2, with lead wires attached to the electrodes pulled out from different ends of the piezoelectric sensor vibrator in FIG. The viscoelastic properties of the sample liquid can be determined from either or both of the changes.
しかしながら、図2において、液体試料が導電性を有する場合、圧電センサ振動子の対向する電極端子間が電気的に一定の抵抗を介して短絡された状態となり、その抵抗値が液体試料の導電率により大きく変化することから、液体試料の粘度を正しく測定することが困難であった。 However, in FIG. 2, when the liquid sample has conductivity, the opposing electrode terminals of the piezoelectric sensor vibrator are electrically short-circuited via a certain resistance, and the resistance value is the conductivity of the liquid sample. Therefore, it was difficult to correctly measure the viscosity of the liquid sample.
超音波粘度計により導電性液体の粘度を測定する方法として、特許文献2には、「測定溶液の導電率が高く、圧電振動子が安定に発振しない場合は圧電振動子の片面だけを測定溶液に接するようにするのが好ましい。」として、図3に示すように、圧電振動子の一方の面を板状部材3とシリコン樹脂部材4により封止する方法が開示されている。しかしながら、図3に示されるように、寸法が等しい対向電極を用いてエネルギー閉じ込め厚みすべり振動を励振する場合、液体試料の導電性のために液体試料と接触する面の電極面積が圧電振動子と液体試料とが接触する面積まで大きくなったように作用し、液体試料の導電率により圧電体の対向電極部の電界分布が変化し、その結果センサ振動子の特性が変化して液体試料の粘度を正確に測定することが困難になるという問題があった。 As a method for measuring the viscosity of a conductive liquid with an ultrasonic viscometer, Patent Document 2 states that “If the measurement solution has high conductivity and the piezoelectric vibrator does not oscillate stably, only one side of the piezoelectric vibrator is measured. As shown in FIG. 3, a method of sealing one surface of a piezoelectric vibrator with a plate-like member 3 and a silicon resin member 4 is disclosed. However, as shown in FIG. 3, in the case of exciting the energy-confined thickness shear vibration using counter electrodes having the same dimensions, the electrode area of the surface in contact with the liquid sample is It acts as if the liquid sample is in contact with the liquid sample, and the electric field distribution of the counter electrode portion of the piezoelectric body changes depending on the conductivity of the liquid sample. There is a problem that it becomes difficult to accurately measure.
以上に説明した、特許文献1、及び特許文献2に開示されている超音波粘度計では、圧電振動子の振動モードとして厚みすべり振動モードが利用されているが、非特許文献2には、薄い圧電円板の面拡がり振動モードを利用することにより粘度の測定が可能であることが報告されている。
しかしながら、薄い圧電円板の面拡がり振動モードを利用する場合、圧電円板の両面には電極が形成され、圧電円板振動子の支持は、圧電円板の中心で行われるため、そのままの状態で圧電センサ振動子を、導電性を有する試料液体に浸漬すると、次の段落で詳しく説明するように、試料液体の導電率の影響により試料液体の粘度を正確に測定することができない。
In the ultrasonic viscometers disclosed in Patent Document 1 and Patent Document 2 described above, the thickness-shear vibration mode is used as the vibration mode of the piezoelectric vibrator. It has been reported that the viscosity can be measured by using the surface spreading vibration mode of the piezoelectric disk.
However, when using the surface expansion vibration mode of a thin piezoelectric disc, electrodes are formed on both sides of the piezoelectric disc, and the piezoelectric disc vibrator is supported at the center of the piezoelectric disc. If the piezoelectric sensor vibrator is immersed in a conductive sample liquid, the viscosity of the sample liquid cannot be accurately measured due to the influence of the conductivity of the sample liquid, as will be described in detail in the next paragraph.
一般に、超音波粘度計用圧電センサ振動子の電気的等価回路は、注目する共振周波数の近傍で図4のように表される。L1、C1、R1、Cdは粘度計用の圧電センサ振動子を大気中で測定した場合の等価回路定数であり、圧電センサ振動子を液体試料に浸漬した場合、液体試料の粘弾性特性によりL2とR2が付加されて共振周波数が低下するとともに共振周波数における抵抗値、いわゆる共振抵抗が大きくなる。超音波粘度計においては、このときの共振周波数の変化あるいは共振抵抗の変化のいずれか、または、両方から、液体試料の粘弾性特性を測定している。
しかしながら、圧電センサ振動子を、導電性を有する液体試料に浸漬すると、2つの電気端子に導電性液体が接触することになり、圧電センサ振動子の等価回路は、図4に示すように、圧電センサ振動子の端子間に、導電性液体の導電率による抵抗R0と導電性液体の誘電率による静電容量C0が並列に挿入された回路となり、圧電センサ振動子の共振抵抗や共振周波数が、これらの抵抗R0と静電容量C0抗により変化するため、導電性を有する液体の粘度を正しく測定することができなくなる。
In general, an electrical equivalent circuit of a piezoelectric sensor vibrator for an ultrasonic viscometer is expressed as shown in FIG. 4 in the vicinity of a resonance frequency of interest. L 1 , C 1 , R 1 , and Cd are equivalent circuit constants when the viscometer piezoelectric sensor transducer is measured in the atmosphere. When the piezoelectric sensor transducer is immersed in a liquid sample, the viscoelasticity of the liquid sample Depending on the characteristics, L 2 and R 2 are added to lower the resonance frequency and increase the resistance value at the resonance frequency, so-called resonance resistance. In the ultrasonic viscometer, the viscoelastic characteristics of the liquid sample are measured from either or both of the change in the resonance frequency and the change in the resonance resistance.
However, when the piezoelectric sensor vibrator is immersed in a conductive liquid sample, the conductive liquid comes into contact with the two electrical terminals, and the equivalent circuit of the piezoelectric sensor vibrator is piezoelectric as shown in FIG. Between the terminals of the sensor vibrator, a resistor R 0 due to the conductivity of the conductive liquid and a capacitance C 0 due to the dielectric constant of the conductive liquid are inserted in parallel, resulting in a resonance resistance and resonance frequency of the piezoelectric sensor vibrator. However, since it varies depending on the resistance R 0 and the capacitance C 0 , the viscosity of the conductive liquid cannot be measured correctly.
本発明は、以上に示した従来の超音波粘度計用圧電センサ振動子の欠点を除去し、導電性を有する液体試料の粘度、及び導電率を微小量の試料で測定可能な超音波粘度計用圧電センサ振動子、及びこれを用いた超音波粘度計を提供する。 The present invention eliminates the drawbacks of the conventional piezoelectric sensor vibrator for an ultrasonic viscometer and can measure the viscosity and conductivity of a liquid sample having conductivity with a very small amount of sample. A piezoelectric sensor vibrator for ultrasonic waves and an ultrasonic viscometer using the same are provided.
本発明によれば、厚さ方向に大きな分極成分を有する短冊状圧電板の長さ方向のほぼ半分の領域に厚さ方向に対向する励振用電極対を形成し、それぞれの対向電極からリード線を引き出すとともに、前記短冊状圧電板の長さ方向の中心部を支持固定した長さ方向縦振動モードの圧電センサ振動子を、この支持固定部を支持した状態で、前記短冊状圧電板の励振用対向電極対が形成されていない側の端面から所定の長さの部分を被測定試料液体に浸漬したときの、前記圧電センサ振動子の共振抵抗の変化量あるいは共振周波数の変化量から前記試料液体の粘度を測定する超音波粘度計用圧電センサ振動子、及びこれを用いた超音波粘度計が得られる。 According to the present invention, the excitation electrode pair opposed in the thickness direction is formed in a substantially half region in the length direction of the strip-shaped piezoelectric plate having a large polarization component in the thickness direction, and the lead wire is formed from each counter electrode. The piezoelectric sensor vibrator in the longitudinal longitudinal vibration mode in which the central portion in the longitudinal direction of the strip-shaped piezoelectric plate is supported and fixed, while the support-fixing portion is supported, the excitation of the strip-shaped piezoelectric plate is performed. The sample from the amount of change in the resonance resistance or the change in the resonance frequency of the piezoelectric sensor vibrator when a portion of a predetermined length from the end surface on the side where the counter electrode pair is not formed is immersed in the sample liquid to be measured A piezoelectric sensor vibrator for an ultrasonic viscometer that measures the viscosity of a liquid and an ultrasonic viscometer using the same are obtained.
また、本発明によれば、前記圧電センサ振動子用短冊状圧電板の励振用対向電極対が形成されていない側の端面から所定の長さの部分に、端面部分の厚さが最も薄くなるようなテーパ加工が施されている超音波粘度計用圧電センサ振動子、及びこれを用いた超音波粘度計が得られる。 Further, according to the present invention, the thickness of the end face portion is the smallest from the end face on the side where the excitation counter electrode pair of the strip-like piezoelectric plate for the piezoelectric sensor vibrator is not formed to a predetermined length. A piezoelectric sensor vibrator for an ultrasonic viscometer that has been subjected to such taper processing, and an ultrasonic viscometer using the same are obtained.
また、本発明によれば、前記圧電センサ振動子用短冊状圧電板の励振用対向電極対が形成されていない領域の少なくとも一方の面の先端からおよそ圧電センサ振動子の全長の3分の1の位置に、試料液体の深さを検出するための電極対を形成した超音波粘度計用圧電センサ振動子、及びこれを用いた超音波粘度計が得られる。 Further, according to the present invention, from the tip of at least one surface of the region where the excitation counter electrode pair of the strip-shaped piezoelectric plate for the piezoelectric sensor vibrator is not formed, approximately one third of the total length of the piezoelectric sensor vibrator. In this position, an ultrasonic viscometer piezoelectric sensor vibrator having an electrode pair for detecting the depth of the sample liquid and an ultrasonic viscometer using the piezoelectric sensor vibrator are obtained.
また、本発明によれば、前記圧電センサ振動子用短冊状圧電板の励振用対向電極対が形成されていない領域の、前記試料液体の深さを検出するための電極対が形成された面と対向する面に、試料液体の導電率を測定するため電極対を形成した、超音波粘度計用圧電センサ振動子、及びこれを用いた超音波粘度計が得られる。 Further, according to the present invention, the surface on which the electrode pair for detecting the depth of the sample liquid is formed in a region where the excitation counter electrode pair of the strip-shaped piezoelectric plate for the piezoelectric sensor vibrator is not formed. A piezoelectric sensor transducer for an ultrasonic viscometer and an ultrasonic viscometer using the same are formed on the surface facing the electrode, in which an electrode pair is formed to measure the conductivity of the sample liquid.
さらに、本発明によれば、前記圧電センサ振動子用短冊状圧電板の支持固定部において、前記圧電センサ振動子の励振用対向電極対が形成された部分を有底のパイプに挿入、固定するとともに、前記圧電センサ振動子の支持固定部に、前記圧電センサ振動子の励振用対向電極対が形成されていない部分よりも長い、複数個の棒状、あるいは板状、あるいは枠状の圧電センサ振動子ガードを具備した超音波粘度計用圧電センサ振動子、及びこれを用いた超音波粘度計が得られる。 Furthermore, according to the present invention, in the supporting and fixing portion of the strip-like piezoelectric plate for the piezoelectric sensor vibrator, the portion where the counter electrode pair for excitation of the piezoelectric sensor vibrator is formed is inserted and fixed to the bottomed pipe. In addition, a plurality of rod-shaped, plate-shaped, or frame-shaped piezoelectric sensor vibrations that are longer than a portion where the excitation counter electrode pair of the piezoelectric sensor vibrator is not formed on the support fixing portion of the piezoelectric sensor vibrator. A piezoelectric sensor vibrator for an ultrasonic viscometer provided with a child guard and an ultrasonic viscometer using the same are obtained.
本発明の圧電センサ振動子は、超音波粘度計の圧電センサ振動子として、短冊状圧電板の長さ方向縦振動モード振動子を用い、長さ方向縦振動を励振するための励振用対向電極対をこの短冊状圧電板の長さ方向の約半分の領域だけに形成しているため、残りの半分の領域の励振用対向電極対が形成されていない部分を被測定試料液体に浸漬することにより、導電性液体の導電率に影響されることなく、導電性液体試料の粘度を測定することができる。 The piezoelectric sensor vibrator of the present invention uses a longitudinal-direction longitudinal vibration mode vibrator of a strip-like piezoelectric plate as a piezoelectric sensor vibrator of an ultrasonic viscometer, and an excitation counter electrode for exciting longitudinal vibration in the longitudinal direction. Since the pair is formed in only about half the area of the strip-shaped piezoelectric plate in the length direction, the other half area where the excitation counter electrode pair is not formed is immersed in the sample liquid to be measured. Thus, the viscosity of the conductive liquid sample can be measured without being affected by the conductivity of the conductive liquid.
また、本発明の圧電センサ振動子は、圧電センサ振動子の厚さを可能な限り薄く加工するとともに、圧電センサ振動子の励振用対向電極対が形成されていない部分の端面にテーパ加工が施されているので、圧電センサ振動子の振動する端面が試料液体から受ける振動の反作用による測定誤差を最小限に抑えることができる。 In the piezoelectric sensor vibrator of the present invention, the thickness of the piezoelectric sensor vibrator is processed as thin as possible, and the end surface of the portion where the counter electrode pair for excitation of the piezoelectric sensor vibrator is not formed is tapered. Therefore, the measurement error due to the reaction of the vibration that the vibrating end face of the piezoelectric sensor vibrator receives from the sample liquid can be minimized.
また、本発明の圧電センサ振動子は、導電性を有する試料液体に圧電センサ振動子が浸漬される深さが所定の深さに達したかどうかを検出するための浸漬深さ検出用電極対を具備しているため、常に一定の浸漬深さにおいて粘度の測定が可能になり、浸漬深さの変動による測定誤差を極力抑えることができる。 In addition, the piezoelectric sensor vibrator of the present invention is an immersion depth detection electrode pair for detecting whether or not the depth at which the piezoelectric sensor vibrator is immersed in a conductive sample liquid has reached a predetermined depth. Therefore, the viscosity can always be measured at a constant immersion depth, and measurement errors due to variations in the immersion depth can be suppressed as much as possible.
また、本発明の圧電センサ振動子は、導電性を有する試料液体の導電率を測定するための導電率測定用電極対を具備しており、前記浸漬深さ検出用電極対により、浸漬深さを一定の値に管理した状態での
導電率検出用電極対間の電気抵抗を測定することにより、試料液体の導電率を高精度に測定することができる。
In addition, the piezoelectric sensor vibrator of the present invention includes a conductivity measuring electrode pair for measuring the conductivity of a conductive sample liquid, and the immersion depth detecting electrode pair provides an immersion depth. By measuring the electrical resistance between the conductivity detection electrode pairs in a state where is controlled to a constant value, the conductivity of the sample liquid can be measured with high accuracy.
さらに、本発明の圧電センサ振動子は、薄い短冊状圧電板の破壊を防ぐために、短冊状圧電板の被測定試料液体に浸漬する部分を囲むように、しかも試料液体と圧電センサ振動子の接触に影響を与えないように構成された圧電センサ振動子ガードを具備しているため、この圧電センサ振動子が、試料液体の容器やそのほかの物に当たったりした場合でも、圧電センサ振動子が簡単には壊れないため、測定が容易になる。しかも、圧電センサ振動子の寸法を、例えば、1mm×10mm×0.2mmとした場合、試料液体の量は、1ミリリットル以下あれば十分であり、極微小量の試料液体での粘度の測定が可能となる。 Furthermore, the piezoelectric sensor vibrator of the present invention surrounds the portion of the strip-shaped piezoelectric plate immersed in the sample liquid to be measured so as to prevent the thin strip-shaped piezoelectric plate from being broken, and the contact between the sample liquid and the piezoelectric sensor vibrator. Since the piezoelectric sensor vibrator guard is designed so that it does not affect the sensor, even if this piezoelectric sensor vibrator hits a sample liquid container or other objects, the piezoelectric sensor vibrator can be easily used. Because it does not break, measurement becomes easy. Moreover, if the dimensions of the piezoelectric sensor vibrator are 1 mm x 10 mm x 0.2 mm, for example, the amount of sample liquid should be 1 milliliter or less, and the viscosity can be measured with a very small amount of sample liquid. It becomes.
図5は、短冊状圧電板を用いた長さ方向縦振動子50の構造を示す斜視図である。図5において、51は厚さ方向に分極処理された圧電セラミックスの細い板、すなわち短冊状圧電板で、厚さ方向に対向する2つの面のほぼ全面に励振用対向電極対52、53が形成されている。図5において、共振時の波長に比べて厚さと幅が十分に小さい場合に、厚さ方向に対向するように形成された励振用対向電極対に交流電圧を印加した場合には、主に図5の白い両矢印で示すような長さが伸び縮みするような振動が発生し、幅方向や厚さ方向の振動を無視することができる。 FIG. 5 is a perspective view showing a structure of a longitudinal longitudinal vibrator 50 using a strip-shaped piezoelectric plate. In FIG. 5, 51 is a thin plate of piezoelectric ceramics polarized in the thickness direction, that is, a strip-shaped piezoelectric plate, and excitation counter electrode pairs 52 and 53 are formed on almost the entire two surfaces facing in the thickness direction. Has been. In FIG. 5, when an alternating voltage is applied to a pair of excitation counter electrodes formed so as to oppose each other in the thickness direction when the thickness and width are sufficiently smaller than the wavelength at the time of resonance, As shown by the white double arrows in FIG. 5, vibrations that extend and contract are generated, and vibrations in the width direction and thickness direction can be ignored.
図6は、短冊状圧電板の長さ方向縦振動の1次共振モードにおける振動変位分布と応力分布を、下側に示した短冊状圧電板と対応してそれぞれ実線と破線で示しており、図6(a)は、短冊状圧電板の対向する面のほぼ全面に電極が形成されている場合、図6(b)は、短冊状圧電板の対向する面の半分の面に電極が形成されている場合である。
圧電振動子においては、印加電界の分布に対応して応力が発生する。短冊状圧電板の長さ方向縦振動の1次共振モードにおいては、図6に示すように、短冊状圧電板の全体にわたって同一符号の応力が発生する。したがって、図6 (a)のように、短冊状圧電板の全面に対向電極が形成されている場合には、短冊状圧電板の長さ方向縦振動の1次共振モードを効率良く励振することができる。また、図6 (b)に示すように、短冊状圧電板の対向する面の半分の面に電極が形成されている場合には、図6 (a) と比較してちょうど半分の電極だけが応力分布と対応しているため、図6 (a)の場合と比較して半分の効率で励振できることがわかる。
FIG. 6 shows the vibration displacement distribution and the stress distribution in the primary resonance mode of the longitudinal vibration of the strip-shaped piezoelectric plate corresponding to the strip-shaped piezoelectric plate shown on the lower side by a solid line and a broken line, Fig. 6 (a) shows the case where the electrodes are formed on almost the entire opposing surface of the strip-shaped piezoelectric plate.Fig. 6 (b) shows the case where the electrodes are formed on half the opposing surface of the strip-shaped piezoelectric plate. This is the case.
In the piezoelectric vibrator, stress is generated corresponding to the distribution of the applied electric field. In the primary resonance mode of longitudinal vibration in the longitudinal direction of the strip-shaped piezoelectric plate, as shown in FIG. 6, stress of the same sign is generated over the entire strip-shaped piezoelectric plate. Therefore, when the counter electrode is formed on the entire surface of the strip-shaped piezoelectric plate as shown in FIG. 6 (a), the primary resonance mode of longitudinal vibration of the strip-shaped piezoelectric plate can be efficiently excited. Can do. In addition, as shown in FIG. 6 (b), when electrodes are formed on half of the opposing surfaces of the strip-shaped piezoelectric plate, only half of the electrodes are compared to FIG. 6 (a). Since this corresponds to the stress distribution, it can be seen that excitation can be performed with half the efficiency compared to the case of FIG. 6 (a).
図7は、短冊状圧電板の長さ方向縦振動の2次共振モードにおける振動変位分布と応力分布を、下側に示した短冊状圧電板と対応してそれぞれ実線と破線で示しており、図7(a)は、短冊状圧電板の対向する面のほぼ全面に電極が形成されている場合、図7(b)は、短冊状圧電板の対向する面の半分の面に電極が形成されている場合である。
短冊状圧電板の長さ方向縦振動の2次共振モードにおいては、図7に示すように、短冊状圧電板の右半分と左半分の領域の応力の符号が互いに逆極性になる。したがって、図7 (a)のように、短冊状圧電板の全面に対向電極が形成されている場合には、発生する応力が打ち消され、短冊状圧電板の長さ方向縦振動の2次共振モードを励振することができない。一方、図7 (b)に示すように、短冊状圧電板の対向する面の半分の面に電極が形成されている場合には、電極の領域が応力の分布が同符号の領域と重なるため、短冊状圧電板の長さ方向縦振動の2次共振モードを効率良く励振することができる。
FIG. 7 shows the vibration displacement distribution and the stress distribution in the secondary resonance mode of the longitudinal vibration of the strip-shaped piezoelectric plate corresponding to the strip-shaped piezoelectric plate shown on the lower side by a solid line and a broken line, Fig. 7 (a) shows the case where electrodes are formed on almost the entire opposing surface of the strip-shaped piezoelectric plate.Fig. 7 (b) shows the case where electrodes are formed on half the opposing surface of the strip-shaped piezoelectric plate. This is the case.
In the secondary resonance mode of longitudinal vibration in the longitudinal direction of the strip-shaped piezoelectric plate, as shown in FIG. 7, the signs of the stresses in the right half region and the left half region of the strip-shaped piezoelectric plate are opposite to each other. Therefore, as shown in FIG. 7 (a), when the counter electrode is formed on the entire surface of the strip-shaped piezoelectric plate, the generated stress is canceled out, and the secondary resonance of the longitudinal vibration of the strip-shaped piezoelectric plate is canceled. Unable to excite mode. On the other hand, as shown in FIG. 7 (b), when the electrodes are formed on half of the opposing surfaces of the strip-shaped piezoelectric plate, the area of the electrodes overlaps the area of the same sign in the stress distribution. The secondary resonance mode of longitudinal vibration in the longitudinal direction of the strip-shaped piezoelectric plate can be excited efficiently.
前に述べたように、圧電振動子においては、印加電界の分布に対応して応力が発生し、その応力分布が、圧電振動子が有する固有振動モードにおける応力分布に一致する割合の大きさにより、その固有振動モードすなわちその共振モードを励振する効率が定まる。したがって、一般的に、励振効率の高い圧電振動子を得る場合には、図6、及び図7について説明したように、その共振モードにおける応力分布に合わせて電極の配置、及び接続方法が決定される。 As described above, in the piezoelectric vibrator, stress is generated according to the distribution of the applied electric field, and the stress distribution depends on the magnitude of the ratio that matches the stress distribution in the natural vibration mode of the piezoelectric vibrator. The efficiency of exciting the natural vibration mode, that is, the resonance mode is determined. Therefore, in general, when obtaining a piezoelectric vibrator with high excitation efficiency, the electrode arrangement and connection method are determined in accordance with the stress distribution in the resonance mode, as described with reference to FIGS. The
図8は、本発明の1つの超音波粘度計用圧電センサ振動子80の構造例を示す斜視図である。図8において、81は厚さ方向に分極軸成分を有する短冊状圧電板、82、83は短冊状圧電板81の長さ方向の概略半分の領域の両面に形成された励振用対向電極対、84は短冊状圧電板81の励振用対向電極対が形成されていない部分(以下単に無励振電極部という)である。無励振電極部84の領域は、以下に示す本発明の別の構造例を含めて必ずしも厚さ方向の分極軸成分を有している必要はない。 FIG. 8 is a perspective view showing a structural example of one ultrasonic viscometer piezoelectric sensor vibrator 80 of the present invention. In FIG. 8, 81 is a strip-shaped piezoelectric plate having a polarization axis component in the thickness direction, 82 and 83 are excitation counter electrode pairs formed on both sides of a substantially half region in the length direction of the strip-shaped piezoelectric plate 81, Reference numeral 84 denotes a portion of the strip-shaped piezoelectric plate 81 where the excitation counter electrode pair is not formed (hereinafter simply referred to as a non-excitation electrode portion). The region of the non-excited electrode portion 84 does not necessarily have to have a polarization axis component in the thickness direction including another structural example of the present invention described below.
図8の短冊状圧電板81の励振用対向電極対82、83間に、短冊状圧電板81の長さ方向縦振動の共振周波数に等しい周波数の交流電圧を印加すると、短冊状圧電板81は、図5で説明したように、長さが伸縮するように振動する。今、印加する交流電圧の周波数を短冊状圧電板81の長さ方向縦振動の1次の共振周波数とすると、図7に示すように、短冊状圧電板81は、長さ方向の中央部を共振の節とし、両端部が共振の腹となるように振動する。ここで、短冊状圧電板81の長さ方向の中央部の共振の節の位置を支持した状態で、無励振電極部84の領域を試料液体に浸漬すると、短冊状圧電板81の無励振電極部84の表面と面に平行な振動に対する試料液体の反作用すなわち、試料液体の粘度による反作用により、圧電センサ振動子の共振抵抗、及び共振周波数が変化し、この共振抵抗の変化あるいは共振周波数の変化から、試料液体の粘度を測定することができる。
このとき、短冊状圧電板81の厚さをできるだけ薄くすることにより、短冊状圧電板81の振動する端面が試料液体から受ける振動の反作用が少なくなり、試料液体の粘度をより高精度に測定することができる。
When an alternating voltage having a frequency equal to the resonance frequency of the longitudinal longitudinal vibration of the strip-shaped piezoelectric plate 81 is applied between the excitation counter electrode pairs 82 and 83 of the strip-shaped piezoelectric plate 81 of FIG. 8, the strip-shaped piezoelectric plate 81 As described with reference to FIG. 5, it vibrates so that its length expands and contracts. Now, assuming that the frequency of the applied AC voltage is the primary resonance frequency of the longitudinal vibration of the strip-shaped piezoelectric plate 81, the strip-shaped piezoelectric plate 81 has a central portion in the length direction as shown in FIG. It vibrates so that both ends become antinodes of resonance as nodes of resonance. Here, when the region of the non-excited electrode portion 84 is immersed in the sample liquid in a state where the position of the resonance node at the center in the length direction of the strip-shaped piezoelectric plate 81 is supported, the non-excited electrode of the strip-shaped piezoelectric plate 81 The resonance resistance and resonance frequency of the piezoelectric sensor vibrator change due to the reaction of the sample liquid against the vibration parallel to the surface and surface of the part 84, that is, the reaction due to the viscosity of the sample liquid, and this resonance resistance change or resonance frequency change From this, the viscosity of the sample liquid can be measured.
At this time, by reducing the thickness of the strip-shaped piezoelectric plate 81 as much as possible, the reaction of the vibration that the vibrating end surface of the strip-shaped piezoelectric plate 81 receives from the sample liquid is reduced, and the viscosity of the sample liquid is measured with higher accuracy. be able to.
図9は、本発明の別の超音波粘度計用圧電センサ振動子90の構造例を示す斜視図である。図9において、91は厚さ方向に分極軸成分を有する短冊状圧電板、92、93は短冊状圧電板91の長さ方向の概略半分の領域の両面に形成された励振用対向電極対、94は短冊状圧電板91の無励振電極部、95は短冊状圧電板91の無励振電極部94の端面近傍に形成されたテーパ加工部である。 FIG. 9 is a perspective view showing a structural example of another piezoelectric viscometer 90 for an ultrasonic viscometer according to the present invention. In FIG. 9, 91 is a strip-shaped piezoelectric plate having a polarization axis component in the thickness direction, 92 and 93 are excitation counter electrode pairs formed on both surfaces of a substantially half region in the length direction of the strip-shaped piezoelectric plate 91, Reference numeral 94 denotes a non-excited electrode portion of the strip-shaped piezoelectric plate 91, and 95 denotes a tapered portion formed near the end surface of the non-excited electrode portion 94 of the strip-shaped piezoelectric plate 91.
前の段落で説明したように、短冊状圧電板の長さ方向縦振動モードを利用した超音波粘度計用圧電センサ振動子においては、振動端面の影響を少なくするために、圧電センサ振動子の厚さをできるだけ薄くすることが要求される。しかしながら、圧電板の材料は、セラミックスや単結晶など、いずれも比較的に脆い材料であるため、板の厚さを薄くすると壊れやすくなるという問題がある。図9に示す圧電センサ振動子90は、このような問題を解決する構造を有するものであり、短冊状圧電板91の無励振電極部94の端面近傍に先端部の厚さを最も薄くするようなテーパ加工部95が形成されている。このような構造とすることにより、短冊状圧電板91の厚さをより厚くしても、短冊状圧電板91の無励振電極部94の領域を試料液体に浸漬した場合に、短冊状圧電板91の振動する端面が試料液体から受ける振動の反作用が少なくなり、試料液体の粘度をより高精度に測定することができる。 As described in the previous paragraph, in the piezoelectric sensor vibrator for ultrasonic viscometers using the longitudinal vibration mode in the longitudinal direction of the strip-shaped piezoelectric plate, in order to reduce the influence of the vibration end face, It is required to make the thickness as thin as possible. However, since the material of the piezoelectric plate is a relatively fragile material such as ceramics or single crystal, there is a problem that it is easily broken when the thickness of the plate is reduced. The piezoelectric sensor vibrator 90 shown in FIG. 9 has a structure that solves such a problem, and the thickness of the tip portion is made the thinnest in the vicinity of the end face of the non-excited electrode portion 94 of the strip-shaped piezoelectric plate 91. A tapered portion 95 is formed. By adopting such a structure, even when the thickness of the strip-shaped piezoelectric plate 91 is made thicker, the strip-shaped piezoelectric plate is obtained when the region of the non-excited electrode portion 94 of the strip-shaped piezoelectric plate 91 is immersed in the sample liquid. The reaction of vibration received from the sample liquid by the vibrating end face of 91 is reduced, and the viscosity of the sample liquid can be measured with higher accuracy.
図10は、本発明のさらに別の超音波粘度計用圧電センサ振動子100の構造例を示す斜視図である。図10において、101は厚さ方向に分極軸成分を有する短冊状圧電板、102、103は短冊状圧電板101の長さ方向の概略半分の領域の両面に形成された励振用対向電極対、104は短冊状圧電板101の無励振電極部、105は短冊状圧電板101の無励振電極部104の端面近傍に形成されたテーパ加工部、106、107は導電性を有する試料液体に対する浸漬深さ検出用電極である。 FIG. 10 is a perspective view showing a structural example of yet another piezoelectric sensor vibrator 100 for an ultrasonic viscometer according to the present invention. In FIG. 10, 101 is a strip-shaped piezoelectric plate having a polarization axis component in the thickness direction, 102 and 103 are excitation counter electrode pairs formed on both surfaces of a substantially half region in the length direction of the strip-shaped piezoelectric plate 101, 104 is a non-excited electrode portion of the strip-shaped piezoelectric plate 101, 105 is a taper portion formed near the end face of the non-excited electrode portion 104 of the strip-shaped piezoelectric plate 101, and 106 and 107 are immersion depths in the sample liquid having conductivity. This is a detection electrode.
図8、図9に示した本発明の超音波粘度計圧電センサ振動子を用いて試料液体の粘度を測定する場合、原理的に、圧電センサ振動子先端からの試料液体が浸漬されている深さにより測定される粘度の値が変化する。試料液体の表面が短冊状圧電板101の中央付近に近づくほど、短冊状圧電板101の中央部分の振動変位量が小さいため、浸漬深さの変動に対する測定される粘度の変化の割合は小さくなるが、浸漬深さが浅い場合には、浸漬深さの変動に対する測定される粘度の変化の割合が大きくなるため、浸漬深さの管理が重要になる。
図10において、浸漬深さ検出用電極106、107は、短冊状圧電板101の無励振電極部104の、端面から短冊状圧電板101の全長のおよそ3分の1の位置から短冊状圧電板101のほぼ中央部まで延びて、互いに短冊状圧電板101の無励振電極部104の一方の面内で幅方向に対向して形成されている。
短冊状圧電板101に印加する交流電圧の周波数を短冊状圧電板101の長さ方向縦振動の1次の共振周波数とすると、振動振幅は、図6に示すように、短冊状圧電板101の両端部で最大、中央部でゼロとなり、その間の位置では正弦波的に変化している。したがって、端面から短冊状圧電板101の全長のおよそ3分の1の位置の位置まで部分を試料液体に浸漬すれば、圧電センサ振動子100は試料液体による反作用の大部分を検出することが可能となるとともに、前述したように、この深さでは、深さのばらつきの影響が比較的小さくなるので、浸漬深さを検出するのに適した位置になる。短冊状圧電板101の長さ方向の中央部の共振の節の位置を支持した状態で、無励振電極部104の領域を試料液体に徐々に浸漬し、試料液体が浸漬深さ検出用電極106、107に接触すると、浸漬深さ検出用電極106と107間が電気的に導通状態になるため、この位置で粘度の測定を行うことにより、より高精度の測定が可能になる。
When measuring the viscosity of the sample liquid using the ultrasonic viscometer piezoelectric sensor vibrator of the present invention shown in FIGS. 8 and 9, in principle, the depth at which the sample liquid from the tip of the piezoelectric sensor vibrator is immersed is measured. Depending on the thickness, the measured viscosity value changes. The closer the surface of the sample liquid is to the vicinity of the center of the strip-shaped piezoelectric plate 101, the smaller the vibration displacement of the central portion of the strip-shaped piezoelectric plate 101 is, so the rate of change in the measured viscosity with respect to the variation in immersion depth decreases. However, when the immersion depth is shallow, the ratio of the change in the measured viscosity with respect to the variation in the immersion depth becomes large, so that the management of the immersion depth becomes important.
In FIG. 10, the immersion depth detection electrodes 106 and 107 are strip-shaped piezoelectric plates from the position of about one-third of the total length of the strip-shaped piezoelectric plate 101 from the end face of the non-excited electrode portion 104 of the strip-shaped piezoelectric plate 101. They extend to substantially the center of 101 and are formed to face each other in the width direction within one surface of the non-excited electrode portion 104 of the strip-shaped piezoelectric plate 101.
Assuming that the frequency of the alternating voltage applied to the strip-shaped piezoelectric plate 101 is the primary resonance frequency of the longitudinal vibration of the strip-shaped piezoelectric plate 101, the vibration amplitude of the strip-shaped piezoelectric plate 101 is as shown in FIG. It is maximum at both ends and zero at the center, and changes sinusoidally between the positions. Therefore, if the part is immersed in the sample liquid from the end surface to the position of about one third of the total length of the strip-shaped piezoelectric plate 101, the piezoelectric sensor vibrator 100 can detect most of the reaction by the sample liquid. In addition, as described above, since the influence of the variation in depth is relatively small at this depth, the position is suitable for detecting the immersion depth. The region of the non-excited electrode 104 is gradually immersed in the sample liquid while supporting the position of the resonance node at the center in the length direction of the strip-shaped piezoelectric plate 101, and the sample liquid is immersed in the immersion depth detection electrode 106. , 107 is brought into electrical continuity between the immersion depth detection electrodes 106 and 107, and by measuring the viscosity at this position, it is possible to measure with higher accuracy.
図11は、本発明のさらに別の超音波粘度計用圧電センサ振動子110の構造例を示す斜視図である。図11において、111は厚さ方向に分極軸成分を有する短冊状圧電板、112、113は短冊状圧電板111の長さ方向の概略半分の領域の両面に形成された励振用対向電極対、114は短冊状圧電板111の無励振電極部、115は短冊状圧電板111の無励振電極部114の端面近傍に形成されたテーパ加工部、116、117は導電性を有する試料液体に対する浸漬深さ検出用電極対、118、119は導電性を有する試料液体の導電率検出用電極対である。 FIG. 11 is a perspective view showing a structural example of still another piezoelectric sensor vibrator 110 for an ultrasonic viscometer according to the present invention. In FIG. 11, 111 is a strip-shaped piezoelectric plate having a polarization axis component in the thickness direction, 112 and 113 are excitation counter electrode pairs formed on both surfaces of a substantially half region in the length direction of the strip-shaped piezoelectric plate 111, 114 is a non-excited electrode portion of the strip-shaped piezoelectric plate 111, 115 is a tapered portion formed near the end face of the non-excited electrode portion 114 of the strip-shaped piezoelectric plate 111, and 116 and 117 are immersion depths in the sample liquid having conductivity. The detection electrode pairs 118 and 119 are conductivity detection electrode pairs of a sample liquid having conductivity.
図11に示す構造では、短冊状圧電板111の無励振電極部に形成された導電性を有する試料液体に対する浸漬深さ検出用電極対116、117と対向する面に、導電性を有する試料液体の導電率を検出するための導電率検出用電極対118、119が形成されている。導電率検出用電極対118、119は、浸漬深さ検出用電極対116、117よりも所定の長さだけ端面側に長く形成されている。 In the structure shown in FIG. 11, there is a conductive sample liquid on the surface facing the immersion depth detection electrode pair 116, 117 with respect to the conductive sample liquid formed on the non-excited electrode portion of the strip-shaped piezoelectric plate 111. Conductivity detection electrode pairs 118 and 119 are formed for detecting the conductivity. The conductivity detection electrode pairs 118 and 119 are formed longer on the end face side by a predetermined length than the immersion depth detection electrode pairs 116 and 117.
短冊状圧電板111の長さ方向の中央部の共振の節の位置を支持した状態で、無励振電極部114の領域を試料液体に徐々に浸漬し、試料液体が導電率検出用電極対に接触すると導電率検出用電極対118と119の間に試料液体の導電率による電気抵抗が発生し、その抵抗値は、試料液体の浸漬深さが増えるにしたがって小さくなる。試料液体が浸漬深さ検出用電極対116、117に接触した位置における導電率検出用電極対118と119の間の電気抵抗の値を測定することにより、導電率検出用電極対118と119の試料液体への接触深さが一定となるので、試料液体の導電率を高精度に求めることができる。 While supporting the position of the resonance node at the center of the length of the strip-shaped piezoelectric plate 111, the region of the non-excited electrode 114 is gradually immersed in the sample liquid, and the sample liquid becomes the conductivity detection electrode pair. When contacted, an electrical resistance due to the conductivity of the sample liquid is generated between the conductivity detection electrode pairs 118 and 119, and the resistance value decreases as the immersion depth of the sample liquid increases. By measuring the value of the electrical resistance between the conductivity detection electrode pairs 118 and 119 at the position where the sample liquid contacts the immersion depth detection electrode pairs 116 and 117, the conductivity detection electrode pairs 118 and 119 Since the contact depth to the sample liquid is constant, the conductivity of the sample liquid can be obtained with high accuracy.
図12は、本発明のさらに別の超音波粘度計用圧電センサ振動子120の構造例を示す斜視図である。図12において、121は厚さ方向に分極軸成分を有する短冊状圧電板、122、123は短冊状圧電板121の長さ方向の概略半分の領域の両面に形成された励振用対向電極対、124は短冊状圧電板121の無励振電極部、125は短冊状圧電板121の無励振電極部124の端面近傍に形成されたテーパ加工部、126は支持固定部材、127は圧電センサ振動子ガード、128は有底中空ケース、129は外部接続端子である。
前述したように、短冊状圧電板の長さ方向縦振動モードを利用した超音波粘度計用圧電センサ振動子においては、振動端面の影響を少なくするために、圧電センサ振動子の厚さをできるだけ薄くすることが要求される。そのため、圧電センサ振動子が試料液体の容器などに触れた場合に壊れやすくなるという問題があった。
FIG. 12 is a perspective view showing a structural example of still another piezoelectric viscometer 120 for an ultrasonic viscometer according to the present invention. In FIG. 12, 121 is a strip-shaped piezoelectric plate having a polarization axis component in the thickness direction, 122, 123 are excitation counter electrode pairs formed on both surfaces of a substantially half region in the length direction of the strip-shaped piezoelectric plate 121, 124 is a non-excited electrode portion of the strip-shaped piezoelectric plate 121, 125 is a tapered processing portion formed near the end surface of the non-excited electrode portion 124 of the strip-shaped piezoelectric plate 121, 126 is a support fixing member, and 127 is a piezoelectric sensor vibrator guard , 128 is a hollow case with a bottom, and 129 is an external connection terminal.
As described above, in the piezoelectric sensor vibrator for ultrasonic viscometers using the longitudinal vibration mode in the longitudinal direction of the strip-shaped piezoelectric plate, the thickness of the piezoelectric sensor vibrator is made as small as possible in order to reduce the influence of the vibration end face. Thinning is required. Therefore, there is a problem that the piezoelectric sensor vibrator is easily broken when it touches a sample liquid container or the like.
図12の圧電センサ振動子120の構造は、薄い圧電素子を用いた場合でも、圧電センサ振動子の破壊を防ぎ、測定作業を容易にすることが可能な圧電センサ振動子を提供するものである。
図12において、短冊状圧電板121の長さ方向の中央部は支持固定部材126により、長さ方向縦振動1次共振モードの振動にほとんど影響を与えない状態で支持固定されている。短冊状圧電板121に形成された励振用対向電極対、及び浸漬深さ検出用電極からは、外部接続端子129が引き出されている。
短冊状圧電板121の励振用対向電極対が形成された側は、短冊状圧電板121を含むように有底中空ケース128が支持部材126に固定されて、短冊状圧電板121が異物に当たるのを防ぐ構造になっている。
短冊状圧電板121の無励振電極側、すなわち、試料液体に浸漬する側には、枠状の圧電センサ振動子ガード127が支持部材126に固定されて装着され、短冊状圧電板121の無励振電極部124が異物に当たるのを防ぐとともに、短冊状圧電板121の無励振電極部124が試料液体と良好な接触を行うような構造となっている。
The structure of the piezoelectric sensor vibrator 120 in FIG. 12 provides a piezoelectric sensor vibrator that can prevent the destruction of the piezoelectric sensor vibrator and facilitate measurement work even when a thin piezoelectric element is used. .
In FIG. 12, the central portion in the length direction of the strip-shaped piezoelectric plate 121 is supported and fixed by the support fixing member 126 in a state that hardly affects the vibration in the longitudinal longitudinal vibration primary resonance mode. An external connection terminal 129 is drawn out from the excitation counter electrode pair formed on the strip-shaped piezoelectric plate 121 and the immersion depth detection electrode.
On the side of the strip-shaped piezoelectric plate 121 on which the excitation counter electrode pair is formed, the bottomed hollow case 128 is fixed to the support member 126 so as to include the strip-shaped piezoelectric plate 121, and the strip-shaped piezoelectric plate 121 hits a foreign object. It is structured to prevent.
A frame-shaped piezoelectric sensor vibrator guard 127 is fixedly attached to the support member 126 on the non-excited electrode side of the strip-shaped piezoelectric plate 121, that is, the side immersed in the sample liquid, and the strip-shaped piezoelectric plate 121 is not excited. The electrode portion 124 is prevented from hitting the foreign matter, and the non-excited electrode portion 124 of the strip-shaped piezoelectric plate 121 is in good contact with the sample liquid.
図13は、本発明の超音波粘度計用圧電センサ振動子を支持、固定するための支持固部材の構造例を示す斜視図である。図13において、支持固定部材130は、プラスチック製の枠状支持部材132と、シリコンゴムなどの軟弾性材料により成形された角リング状軟弾性支持部材133により構成されており、角リング状軟弾性支持部材133の中央部には、本発明の短冊状圧電板131の断面寸法にほぼ等しい開口部134が形成され、中央部の開口部134の少なくとも一方から、角リング状の支持部材133の開口部に向けて、開口部が広がっている構造になっている。この中央部の開口部134から、角リング状の支持部材133の開口部に向けて広がっている開口部は、短冊状圧電板121を前記支持固定部材130にセットした後で、シリコンゴムなどの軟弾性接着剤を注入して、前記短冊状圧電板131を前記支持固定部材130に接着固定するために使用される。 FIG. 13 is a perspective view showing an example of the structure of a support fixing member for supporting and fixing the piezoelectric sensor vibrator for an ultrasonic viscometer of the present invention. In FIG. 13, the support fixing member 130 is composed of a plastic frame-like support member 132 and a square ring-shaped soft elastic support member 133 formed of a soft elastic material such as silicon rubber. An opening 134 that is substantially equal to the cross-sectional dimension of the strip-shaped piezoelectric plate 131 of the present invention is formed at the center of the support member 133, and the opening of the square ring-shaped support member 133 is formed from at least one of the openings 134 in the center. The opening is widened toward the part. The opening extending from the central opening 134 toward the opening of the square ring-shaped support member 133 is made of silicon rubber or the like after the strip-shaped piezoelectric plate 121 is set on the support fixing member 130. It is used to inject and fix the strip-shaped piezoelectric plate 131 to the support fixing member 130 by injecting a soft elastic adhesive.
図13において点線で示しているのは本発明の圧電センサ振動子を構成する短冊状圧電板であり、図13からわかるように、プラスチック製の枠状支持部材132と軟弾性材料からなる角リング状軟弾性支持部材133はいずれも金型を用いて成形されているため、寸法精度が高く、短冊状圧電板131は、枠状支持部材122、及び角リング状軟弾性支持部材133の開口面に対して垂直に位置決めされている。
また、図12においては、本発明の短冊状圧電板131が長さ方向縦振動の1次共振モードで共振するときの振動の節の部分を、軟弾性体のシリコンゴムで支持しているため、支持、固定により、共振振動が減衰される割合が極めて小さくなり、高精度の粘度の測定が可能になる。また、135は枠状支持部材132に一体に成形された外部接続端子であり、短冊状圧電板131の励振用対向電極対、及び浸漬深さ検出用電極からのリード線を前記中央部の開口部134から前記角リング状軟弾性支持部材133の開口部において、これらの外部接続端子135と接続し、端子接続完了後に接着性を有するシリコンゴムなどにより接着固定することにより、より信頼性の高い圧電センサ振動子を得ることができる。
In FIG. 13, a dotted line indicates a strip-shaped piezoelectric plate constituting the piezoelectric sensor vibrator of the present invention. As can be seen from FIG. 13, a rectangular frame made of a plastic frame-like support member 132 and a soft elastic material. Since each of the soft elastic support members 133 is formed using a mold, the dimensional accuracy is high, and the strip-shaped piezoelectric plate 131 is an opening surface of the frame-shaped support member 122 and the square ring-shaped soft elastic support member 133. It is positioned perpendicular to.
Also, in FIG. 12, because the strip-shaped piezoelectric plate 131 of the present invention resonates in the primary resonance mode of longitudinal vibration in the longitudinal direction, the vibration node portion is supported by the soft elastic silicon rubber. By supporting and fixing, the rate at which the resonance vibration is attenuated becomes extremely small, and the viscosity can be measured with high accuracy. Reference numeral 135 denotes an external connection terminal formed integrally with the frame-shaped support member 132, and a lead wire from the excitation counter electrode pair of the strip-shaped piezoelectric plate 131 and the immersion depth detection electrode is opened in the central portion. By connecting the external connection terminal 135 to the external connection terminal 135 from the portion 134 to the opening of the square ring-shaped soft elastic support member 133 and bonding and fixing with silicon rubber having adhesiveness after the terminal connection is completed, the reliability is higher. A piezoelectric sensor vibrator can be obtained.
本発明の圧電センサ振動子に用いる短冊状圧電板の材質としては、PZTに代表される圧電セラミックスはもちろん、水晶、LiTaO3(タンタル酸リチウム)やLiNbO3(ニオブ酸リチウム)などの圧電単結晶を用いることができる。
また、本発明の圧電センサ振動子に用いる短冊状圧電板に形成した、励振用対向電極対、浸漬深さ検出用電極対、及び導電率測定用電極対は、いずれもリード線の取り付けを短冊状圧電板の長さ方向縦振動の1次共振における共振の節の位置で行うために、それぞれの電極対からリード線取り付け電極が前記共振の節の位置に引き出されている。
また、本発明の圧電センサ振動子の振動モードとして、短冊状圧電板の長さ方向縦振動の2次共振モードあるいは3次共振モードを利用することも、励振用対向電極対を含むそれぞれの電極の配置を、各共振モードにおける応力分布に合わせるとともに、支持固定を共振の節の位置で行うなどの配慮を行うことにより比較的容易に可能である。
The material of the strip-shaped piezoelectric plate used for the piezoelectric sensor vibrator of the present invention is not only piezoelectric ceramics represented by PZT, but also piezoelectric single crystals such as quartz, LiTaO 3 (lithium tantalate) and LiNbO 3 (lithium niobate). Can be used.
In addition, the excitation counter electrode pair, the immersion depth detection electrode pair, and the conductivity measurement electrode pair formed on the strip-shaped piezoelectric plate used in the piezoelectric sensor vibrator of the present invention are all mounted with lead wires. In order to carry out at the position of the resonance node in the primary resonance of the longitudinal vibration in the longitudinal direction of the piezoelectric plate, the lead wire attaching electrode is drawn out from each electrode pair to the position of the resonance node.
Further, as the vibration mode of the piezoelectric sensor vibrator of the present invention, it is also possible to use the secondary resonance mode or the tertiary resonance mode of the longitudinal vibration in the longitudinal direction of the strip-shaped piezoelectric plate. This arrangement can be made relatively easy by matching the stress distribution in each resonance mode and taking into consideration such as supporting and fixing at the position of the resonance node.
50: 短冊状圧電板を用いた長さ方向縦振動子
80,90,100,110:圧電センサ振動子
51,81,91,101,111,121,131:短冊状圧電板
52,53,82,83,92,93,102,103,112,113,122,123:励振用対向電極対
84,94,104,114,124:短冊状圧電板の無励振電極部
95,105,115,125:無励振電極端面近傍のテーパ加工部
106,107,116,117: 浸漬深さ検出用電極対
118,119:導電率測定用電極対
126,130:支持固定部
127:枠状の圧電センサ振動子ガード
128:有底中空ケース
129,135:外部接続端子
132: 枠状支持部材
133: 角リング状軟弾性支持部材
134: 中央部の開口部
50: Longitudinal longitudinal vibrator using strip-shaped piezoelectric plate
80, 90, 100, 110: Piezoelectric sensor vibrator
51, 81, 91, 101, 111, 121, 131: Strip-shaped piezoelectric plate
52,53,82,83,92,93,102,103,112,113,122,123: Excitation counter electrode pairs
84, 94, 104, 114, 124: Non-excited electrode section of strip-shaped piezoelectric plate
95, 105, 115, 125: Tapered parts near the end face of the non-excited electrode
106,107,116,117: Electrode pair for immersion depth detection
118,119: Conductivity measurement electrode pair
126,130: Support fixing part
127: Frame-shaped piezoelectric sensor vibrator guard
128: Bottomed hollow case
129,135: External connection terminals
132: Frame-like support member
133: Square ring soft elastic support member
134: Central opening
Claims (5)
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2015132510A (en) * | 2014-01-10 | 2015-07-23 | 学校法人産業医科大学 | Coefficient-of-viscosity measuring method, coefficient-of-viscosity measuring apparatus, inspection method, body fluid electrolyte concentration and viscosity inspection system, and food manufacturing apparatus |
| JP2016223867A (en) * | 2015-05-29 | 2016-12-28 | 東北電子産業株式会社 | Method and device for measuring viscoelasticity characteristics |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2015132510A (en) * | 2014-01-10 | 2015-07-23 | 学校法人産業医科大学 | Coefficient-of-viscosity measuring method, coefficient-of-viscosity measuring apparatus, inspection method, body fluid electrolyte concentration and viscosity inspection system, and food manufacturing apparatus |
| JP2016223867A (en) * | 2015-05-29 | 2016-12-28 | 東北電子産業株式会社 | Method and device for measuring viscoelasticity characteristics |
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