JPS63300939A - Vibration unit for specific gravity or viscosity measuring instrument - Google Patents

Abstract

PURPOSE:To vibrate a probe in a circular direction at an invariably resonance frequency and to improve the measurement accuracy of viscosity and specific gravity by constituting three vibration units where a probe is coupled with one end of a diaphragm rigidly and a inertia mass body is coupled with the other end. CONSTITUTION:The probe 3 for liquid to be measured is coupled rigidly with one end of the diaphragm (c) which forms a circular piezoelectric vibrator 1A and the inertial mass body 13 is coupled with the other end. Piezoelectric ceramic plates (a) and (b) are stuck on the diaphragm (c) to form the vibrator 1A, whose circular vibration is transmitted to the probe 3 through one-end coupling parts of the ceramic plates (a) and (b). Consequently, one end of the vibrator of the vibrator 1A is fixed by the mass body 13 to cancel the transmission of the circular vibration, and the other is made free to induce circular vibration. Further, the probe 3 which is coupled directly with it is excited directly by the ceramic plates (a) and (b) to converge and transmit the circular vibration efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a device for measuring the specific gravity and viscosity of a liquid, particularly a piezoelectric vibrator which is immersed in a liquid to be measured, and which uses a piezoelectric vibrator as a vibration source in the specific gravity and viscosity measuring device. The present invention relates to an imaging unit that vibrates a probe and detects viscosity or specific gravity based on a change in the vibration.

Prior Art Conventionally, a piezoelectric element having an electromechanical conversion function is used as a vibrator as a vibration source as a specific gravity measuring device for a liquid to be measured.
A probe in which a probe is vibrated in a liquid to be measured is known.

As this piezoelectric vibrator, a thickness-longitudinal vibrator that vibrates longitudinally in the thickness direction of a diaphragm is considered. This thickness-longitudinal vibrator receives harmful hydraulic resistance due to thickness-longitudinal vibration in the liquid, or generates longitudinal waves, etc., which becomes a disturbance factor.
Furthermore, mere longitudinal vibration in the thickness direction does not accurately sense the viscous resistance or moment of inertia of the liquid to be measured, and is not suitable as a vibration source for measuring specific gravity or viscosity.

In addition, the mechanism for properly transmitting the vibrations of the small piezoelectric vibrator with its weak vibration force to the detector has become a bottleneck, and the challenge is how to efficiently and appropriately transmit the vibrations of the vibrator to improve detection performance. It becomes.

Means for Solving the Problems The present invention provides a vibration unit for a specific gravity or viscosity measuring device using a circular vibration mode, which effectively and rationally solves the above problems. As described above, the liquid probe to be measured is rigidly coupled to one end of the diaphragm forming the circular piezoelectric vibrator so that the circular vibration axes are the same, and the inertial mass body is rigidly coupled to the other end of the diaphragm. death,
A piezoelectric material is bonded to the surface of the diaphragm to form the circular piezoelectric vibrator, one end of the diaphragm is fixed to the inertial mass body, and transmission of circular vibration at the same end is sealed, The structure is such that free circular vibration is generated at the other end, and the liquid probe directly connected to the probe is directly excited to cause the probe to vibrate in the circular direction.

As described above, the present invention uses a circular piezoelectric vibrator made of a diaphragm and a bimorph of piezoelectric material as a vibration source for measuring the specific gravity or viscosity of a liquid to be measured, and one end of the circular piezoelectric vibrator is connected to an inertial mass. While fixing it with your body and suppressing the transmission of circular vibration,
The other end can be freed to generate active circular imaging, and the liquid probe directly connected to this can be directly excited by the diaphragm, concentrating the circular vibration and transmitting it appropriately and efficiently. can do.

In addition, the probe is vibrated in a circular direction in the liquid to be measured, preventing disturbances such as waves in the liquid to be measured as much as possible, and accurately and sensitively sensing the viscous resistance or moment of inertia of the liquid to be measured. High performance can be achieved by making the entire vibration unit compact and rationally structured.

Example Embodiments of the present invention will be described in detail below with reference to the drawings.

As described above, the present invention uses the circular piezoelectric vibrator IA as a vibrator having an electromechanical conversion function as a vibration source.

For example, a torsional vibrator can be used as the circular piezoelectric vibrator IA. The torsional vibrator is a piezoelectric vibrator that repeatedly vibrates alternately in clockwise and counterclockwise directions at both ends of the vibrator centering on the vibration axis, that is, vibrates in a circular direction. In other words, circular vibration is a vibration mode in which vibrations are repeated in mutually opposite thickness directions at both ends of the vibrator with the vibration axis as the center.

As shown in FIG. 1, a probe 3 is attached to one end of a diaphragm C constituting the circular piezoelectric vibrator IA, which is the driving source, through a small-diameter shaft 2 so that its circular vibration axes G are the same. Rigidly connect.

The shaft portion 2 has a round or square shaft shape and is directly connected to the circular vibration axis of the diaphragm C, and inputs the vibration of the circular piezoelectric vibrator IA at the circular vibration axis G, and from the circular vibrator IA. The signal is transmitted to the probe 3 which is spaced apart.

Depending on the implementation, a mass body 5 having a constant moment of inertia is integrally attached to the shaft portion 2 to adjust the resonance frequency of the circular piezoelectric vibrator IA.

Depending on the implementation, an imaging sensor IB for detecting circular vibration of the probe 3 in the liquid to be measured is attached to the shaft portion 2.

The vibration sensor IB is composed of an element having an electromechanical conversion function such as a piezoelectric ceramic, and applies mechanical vibration in the liquid to be measured of the probe 3 to the vibration sensor IB via the shaft portion 2, The IB function converts the mechanical vibration into an electrical signal to measure specific gravity or viscosity.

Even if the circular piezoelectric vibrator IA is used as a sensor due to its mechanical-electric conversion function without using the vibration sensor IB, viscosity and specific gravity can be detected using the same principle as described above.

Furthermore, the other end of the diaphragm C constituting the circular piezoelectric vibrator IA as described above is rigidly coupled to the inertial mass body 13 via the shaft portion 2a at a portion of the circular vibration axis G thereof. In this way, a three-member vibration unit is constructed in which the probe 3 is rigidly connected to one end of the diaphragm C, and the inertial mass 13 is rigidly connected to the other end.

As an example of a rigid connection between the diaphragm of the circular oscillator IA, the inertial mass body 13, and the probe 3, each part may be constructed as a single piece by cutting, or each part may be constructed as a single piece as shown in FIG. 1C. It is divided into several parts and machined and then joined together by screwing or gluing.

The vibration unit 10 thus formed is housed in a handgrip-shaped envelope 8 using the inertial mass body 13 as a fixed carrier. That is, the vibration unit 10 is mounted inside the envelope 8 with the inertial mass body 13 as a fixed carrier by fixing the inertial mass body 13 to the inner surface of the envelope 8 via a shock absorbing material 14 for vibration absorption. The probe 3 side is made free and exposed from the tip of the envelope 8 so that it can penetrate into the liquid to be measured 9.

The inertial mass body 13 uses its moment of inertia to block the transmission of vibrations to the fixed side (the other end side of the imaging plate), prevents the attenuation of circular vibrations, and transmits the vibrations to the probe 3 on the one end side. be carried out stably and efficiently.

The inertial mass body 13, which is a fixed carrier of the imaging system, may be extended in the direction of the imaging axis and fixed to the envelope 8.

By fixing one end of the diaphragm C as described above, the circular piezoelectric vibrator IA blocks vibration transmission to the same end, generates free circular direction vibration at the other end, and transmits the circular direction vibration to the same end. The vibration is transmitted to the probe 3 directly connected to the other end, vibrates in a circular direction around the shaft 2, and the vibration of the probe 3 in the liquid is applied to the vibration sensor IB. Specific gravity or viscosity is detected as an equivalent electrical signal from the change in vibration proportional to .

Next, a torsional vibrator will be explained as a specific example of the circular piezoelectric vibrator IA.

Zero-polarization treatment, which uses piezoelectric ceramic that has been polarized (poled) to give piezoelectricity as a piezoelectric material, fixes the polarization direction in one direction, and depending on the polarization direction, it can be used as a positive or negative voltage. The direction of expansion or contraction (direction of length vibration) relative to the voltage is opposite.

As shown in FIGS. 3 to 7, this torsional vibrator is a vibrator formed by laminating a diaphragm C interposed between piezoelectric ceramics a and b that vibrate along the length, and one side of the diaphragm C. Both length vibrating piezoelectric ceramics a and b on one side and the other side are arranged so that their length vibration directions intersect, and both length vibrating piezoelectric ceramics a and b are placed on one side and the other side of the diaphragm C. The structure is such that the length of the diaphragm C is vibrated to cause expansion or contraction at the same time, and return vibration of the diaphragm C is obtained.

To explain this specifically, a pair of elongated piezoelectric ceramics a and b exhibiting a rectangular shape that vibrate in the longitudinal direction is prepared, one elongated piezoelectric ceramic a is attached to one side of a rectangular diaphragm C, The other elongated piezoelectric ceramic b is connected to the same diaphragm C.
At the same time, one elongated piezoelectric ceramic a is placed on one diagonal of the diaphragm C, and the other elongated piezoelectric ceramic b is placed on the other diagonal of the diaphragm C. The piezoelectric ceramics a and b are arranged so that their longitudinal vibration directions intersect. The piezoelectric ceramics a and b intersect at the center of the rectangular diaphragm C, and both ends thereof are located at diagonal corner portions of the diaphragm C.

In the case of parallel connection as shown in FIG. 6A, both elongated piezoelectric ceramics a and b are pasted on one side and the other side of the diaphragm C so that their respective polarization directions P are opposite to each other. Form a crossover state.

Further, as shown in FIG. 6B, in the case of series connection, the elongated piezoelectric ceramics a and b are stacked on the diaphragm C in the above-mentioned crossed arrangement so that they are polarized in the same direction.

As a result of the above, as shown in Fig. 7, when the vibration mode of each piezoelectric ceramic, Mick a, b, causes elongation xl in one piezoelectric ceramic a, the other piezoelectric ceramic b also elongates x.
2, and conversely, when one piezoelectric ceramic a contracts, the other piezoelectric ceramic b also contracts, so that stretching vibration modes in the same direction occur simultaneously on the intersecting axis. Therefore, the diaphragm C bonded thereto is bent in one direction in the thickness direction at both ends of the vibrating piezoelectric element a of one length that intersects, and at the same time at both ends of the vibrating piezoelectric element a of the other length that intersects. This results in bending y in the other direction in the thickness direction. By alternately producing this reverse thickness direction vibration, so-called double bending vibration (return vibration) Z
That is, circular direction vibration is already described.

Next, a specific structural example of the vibration sensor IB will be described (see FIGS. 8 to 10).

As the vibration sensor IB, an acceleration sensor is used, and as a suitable example, an angular acceleration sensor composed of a pair of left and right piezoelectric bisulf type vibration elements S, S2 as shown in the figure is used.

The vibrating elements S, , S are piezoelectric ceramic bimorphs,
Or it is a bimorph of a piezoelectric ceramic and an imaging plate (metal plate).

The vibrating elements S, , S2 are installed at appropriate positions on the shaft 2 so as to be axially symmetrical, and when a circular vibration centered on the shaft 2 is applied, the vibrating elements S, , S2 have the same phase. It is arranged so that a voltage is generated and output.

Figure 10A shows a case in which piezoelectric bimorph type vibrating elements S1 and S2 are connected in parallel with each other.As each vibrating element, bimorphs stacked with the polarization directions P, , P, in the same direction are used. are attached to the shaft part 2 so that the polarization directions are opposite to each other, and the internal electrodes and the external electrodes are connected to each other, respectively, and one connection end is a positive voltage terminal (or negative voltage terminal) and the other is a negative voltage terminal. (or positive voltage terminal)
shall be.

With the above configuration, the same vibrating elements S, , S.

When the same thickness direction vibration w, , W in the figure is applied to the free end of , a positive voltage is generated on one of the internal electrodes of the vibrating element S, , S2, and a negative voltage is generated on the other, which cancel each other out, and similarly. A positive voltage is generated at one external electrode of the vibrating elements S, S2, and a negative voltage is generated at the other external electrode, which cancel each other out, and as a result, the output between the positive voltage terminal and the negative voltage terminal becomes zero. That is, the vibration sensor IB does not produce an output due to vibrations other than circular excavation.

On the other hand, when circular vibration with the coaxial part 2 as the vibration axis is applied to the vibrating element S I + 52 via the shaft part 2 arranged at the center of the vibrating elements S, S2, one of the vibrating elements 51 and S2 When the free end vibrates in one direction W in the thickness direction, the other free end vibrates in the other direction W2 in the thickness direction. A voltage (or negative voltage) is generated, and a negative voltage (or positive voltage) of the same phase is generated on the same external electrode, resulting in a voltage output between the positive voltage terminal and the negative voltage terminal.

FIG. 10B shows a case where one of the vibrating elements S, S2 has an outward polarization direction and the other has an inward polarization direction, forming a bimorph and connecting them in series, As shown in the figure, one external electrode is connected to each other to form a positive voltage terminal + (or negative voltage terminal), and the other external electrode is connected to each other to form a negative voltage terminal - (or positive voltage terminal). The same operation result as in the case of FIG. 10A is obtained. Of course, other piezoelectric bimorph connection configurations can be used in accordance with the above arrangement to obtain similar operation.

Vibration element S1 configuring the vibration sensor IB. As shown in FIGS. 8 and 9, the axially symmetrical arrangement of S2 is such that a rectangular pedestal 15 is integrally formed on the shaft portion 2, and the base of one vibrating element S is formed on one side surface of the pedestal 15 facing each other. The end of the vibrating element S2 is attached with a plane parallel to the electrode plane, and the base end of the other vibrating element S2 is attached to the other side with a plane parallel to the electrode plane. , S, are arranged so that they extend in opposite directions.

Further, as shown by virtual lines in FIG. 9, the same vibration elements Sl and S2
may be arranged axially symmetrically on the same straight line. As the coupling mechanism between the shaft portion 2 and the vibrating elements S, , S, other coupling means may be used in accordance with the above arrangement conditions.

As a result of the above, the circular vibration of the probe 3 in the liquid to be measured is applied to the vibration sensor IB, which is excited in the same direction to generate a voltage output between the positive and negative voltage terminals according to the operating principle described above. . The specific gravity or viscosity is displayed using the voltage output as a detection signal.

To explain the case of a hydrometer, a hollow or solid perfect cylindrical body or a thin plate having a mirror-finished circumferential surface with a relatively wide area is used as the liquid to be measured probe 3, and the circular piezoelectric vibrator IA is The directional vibration is transmitted to the probe 3 via the shaft part 2 which is rigidly coupled to the diaphragm C, and the probe 3 is loosely attached to the liquid to be measured, and the directional vibration is transmitted around the shaft part 2, that is, the diaphragm C. It is caused to vibrate in a circular direction around the circular vibration axis G of . As a result of this circular vibration, the moment of inertia of the liquid to be measured 9 is loaded onto the probe 3, increasing the rotational moment of the probe 3. Due to this increase in rotational moment, the resonance frequency of the vibration unit 10 including the circular piezoelectric vibrator IA is changed, and the vibration sensor I
An electric signal corresponding to the amount of change in the resonant frequency is obtained by B.

That is, when the probe 3 is immersed in a liquid, the resonance frequency changes, causing a shift in the resonance point. A hydrometer measures the specific gravity by observing the shift in resonance frequency (change in frequency) at the resonance point of this vibration.

This function is due to the mechanical-electrical energy conversion effect of the piezoelectric ceramic that constitutes the vibration sensor IB. The circular vibration, unlike the longitudinal vibration in the thickness direction, suppresses the wave motion of the liquid that causes disturbance, keeps the liquid in a static state, and senses inertial resistance well.

Also, to explain the case of a viscometer, the liquid to be measured probe 3
A solid or hollow perfect cylindrical body or disk having a mirror-finished circumferential surface with a relatively wide area is used as the body, and is rigidly connected to one end of the diaphragm C through the shaft part 2 at the center of the end face.

As a result of the above, the circular vibration of the circular piezoelectric vibrator IA is transmitted to the probe 3 via the shaft portion 2, and the probe 3 is moved in a circular motion around the shaft portion 2, that is, around the circular vibration axis G. directional vibration,
The viscous resistance of the liquid to be measured is sensed on the circular vibration surface. The circular vibration, unlike the longitudinal vibration, suppresses the wave motion of the liquid that causes disturbance, keeps the liquid in a static state, and effectively captures viscous resistance. The resonance frequency is changed by sensing the viscous resistance, and the vibration sensor IB is excited at the resonance frequency.

By sensing the viscous resistance by the probe 3, the mechanical impedance of the entire vibration system when excited at the resonance frequency is changed according to the viscous resistance, and the vibration level (voltage level) of the vibration sensor IB at the time of resonance is changed. causes a change in That is, a viscometer measures the viscosity by observing the level of this vibration. This function is due to the mechanical-electrical energy conversion effect of the vibration sensor IB.

As described above, the function of the vibration sensor IB as described above may be provided to the circular piezoelectric vibrator IA.

Effects of the Invention As described above, the present invention uses a circular piezoelectric vibrator consisting of a diaphragm and a bimorph of a piezoelectric material as a vibration source for measuring the specific gravity or viscosity of a liquid to be measured, and one end of the circular piezoelectric vibrator is While fixing with an inertial mass body and suppressing the transmission of circular vibration,
With the other end free, active circular vibrations can be generated, and the liquid probe directly connected to the liquid probe to be measured can be directly excited by the diaphragm to transmit the circular vibrations soundly.

According to the present invention, one end of the diaphragm is rigidly coupled to the inertial mass body, thereby effectively preventing the attenuation of the vibration of the circular vibrator, while directly and intensively vibrating the probe at the other end of the diaphragm. It is possible to give vibration and excite the probe, and it is possible to perform proper and efficient vibration transmission, and the probe can always be vibrated in a circular direction at an accurate resonance frequency, thereby increasing the measurement accuracy and reliability of viscosity and specific gravity. In particular, by connecting a small-diameter shaft to the circular vibration axis of the diaphragm and connecting the probe through this, the left and right corners of the diaphragm end are made free parts, and the Active vibration is induced without inhibiting the torsional vibration. There is a risk that axial vibration components may enter the left and right corner portions of the diaphragm away from the vibration axis, causing disturbances in vibration. Only healthy torsional vibration components (circular vibration components) in the vibration axis of the diaphragm can be appropriately captured and transmitted to the probe.

In addition, the probe is vibrated in a circular direction in the liquid to be measured, and disturbances such as waves in the liquid to be measured are prevented as much as possible, so that the viscous resistance or moment of inertia of the liquid to be measured can be accurately and sensitively sensed. With the above configuration, it is possible to make the entire vibrating unit compact and have a rational structure, thereby achieving improved performance.

4 Drawing PJ-! 1A is a side view showing a vibration unit constituting a viscosity or specific gravity measuring device according to an embodiment of the present invention, FIG. 1B is a front view of the same, FIG. C is a sectional view of the same, and FIG. A perspective view showing the appearance of the viscosity or specific gravity measuring device, FIG. 3 is a perspective view of a circular piezoelectric vibrator, FIG. 4 is a side view of the same, FIG. 5 is a plan view of the same, FIG.
B is a side view showing an example of how the vibrator is connected; FIG. 7 is a perspective view illustrating torsional vibration of the vibrator; FIG. 8 is a perspective view of a vibration unit showing a part of the vibration sensor; FIG. A partial plan view of the vibration sensor, and FIGS. 10A and 10B are side views showing an example of connection of the same imaging sensor (angular acceleration sensor).

IA...Circular piezoelectric vibrator, a, b...Piezoelectric ceramic, C...Vibration plate, 2...Shaft portion, 3...Measurement liquid probe, 9...Inertial mass Body, G...Circular imaging axis.

Figure 4 IA Figure 5 Figure 6 Figure 8 Figure 10

Claims (2)

[Claims] (1) A liquid probe to be measured is rigidly coupled to one end of a diaphragm forming a circular piezoelectric vibrator so that its circular vibration axes are the same, and an inertial mass body is rigidly coupled to the other end of the diaphragm. ,
A piezoelectric material is bonded to the diaphragm to form the circular piezoelectric vibrator, and the circular vibration of the circular piezoelectric vibrator is transmitted to the liquid probe to be measured via the one end coupling portion of the diaphragm. A vibration unit in a specific gravity or viscosity measuring device configured to transmit information. (2) The liquid probe to be measured is rigidly coupled to one end of the diaphragm via a shaft portion arranged so that the circular vibration axes are the same. Vibration unit in specific gravity or viscosity measuring equipment.