JPS6030160B2 - Resonance type vibration pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resonant type vibration pickup device used to detect elastic vibrations in a liquid, and particularly to a resonant type vibration pickup device with excellent detection sensitivity for a predetermined frequency.

Conventionally, a vibration pickup having a Langevin type structure is known as a device for detecting elastic vibrations in a liquid.

However, since this pickup uses a longitudinal vibration mode, its resonance frequency is almost inversely proportional to the thickness dimension of the Langevin structure. It has the disadvantage of being significantly larger in size. On the other hand, it is known that sagging vibration is used as a method of lowering the resonant frequency without significantly increasing the shape and dimensions.

In particular, when the surface manipulation vibration mode of a disk is used, the disk has the advantage of being simple in shape, can be manufactured with high precision, and is easy to analyze and handle the vibration mode. However, in this case, there is a drawback that in order to stabilize the resonance frequency, the conditions for fixing the circumference of the disk must be stabilized. In addition, when using such a resonant vibration pickup using the undulating vibration of a disk as an elastic detection element in liquid, the vibration frequency to be detected is set as the resonance frequency in the liquid storage container in which the pickup is attached. If such elements were present, vibrations would propagate from the pickup mounting portion, resulting in a disadvantage that the S/N ratio would deteriorate. The present invention aims to solve the drawbacks of conventional pickup devices, and uses a peripheral fixed surface undulation vibration mode that operates stably in liquid, has a resonant frequency in the audible frequency range, and - The purpose is to provide a resonant type vibration pickup device with a good S/N ratio.

The vibration pickup device according to the present invention has the following configuration.

That is, a piezoelectric ceramic element is bonded to the bottom of a cap-shaped diaphragm formed by extending and protruding an annular side wall from the periphery of a thin metal disk that resonates at the vibration frequency to be detected. At the same time, the side wall portion of the diaphragm is joined to the tip of the support member, and an annular member is attached so as to cooperate with the iron joint portion of the support member to sandwich the side wall portion of the diaphragm. Fix the periphery of the diaphragm so that the vibration mode is stable. In addition, when attaching the holding part that holds the pickup configured in this way to a liquid storage container, the pickup holding member and the container are attached so that mechanical vibrations from the part attached to the container are not transmitted to the pickup. The part between the mounting member and the mounting member is made of a material with a large vibration damping coefficient, or an elastic body with a large elastic loss such as a rubber-like substance is interposed therebetween. In the vibration pickup device of the present invention having the above-described configuration, the side wall portion is provided on the diaphragm, and the entire side wall portion is fixed uniformly to the support member by the annular member, so that the conditions for fixing the periphery of the diaphragm are stabilized. This has the effect of making the peripheral green part at the boundary between the circular flat plate part and the side wall part act as a vibration node, and also stabilizing the resonant frequency of the diaphragm.

An example of this will be described below. FIG. 1 is a sectional view of a resonant vibration pickup device according to an embodiment of the present invention.

In the figure, 1 and 1' are thin piezoelectric ceramic elements, and 2 and 2' are caps 2 and 2 formed from thin metal plates.
' are glued to the bottom of each with an adhesive such as epoxy resin. The adhesive is applied thinly enough to ensure electrical continuity between the piezoelectric ceramic element electrodes 3, 3' and the metal caps 2, 2'. The caps 2, 2' are iron-bonded to both ends of a cap support member 4 made of a conductive material, and the side walls of the caps 2, 2' are further attached to an annular member 5.
, 5'. FIG. 2 shows a perspective view of the piezoelectric ceramic element 1', the metal caps 2, 2', the cap support village 4, and the annular members 5, 5'.

As described above, the adhesive surface electrodes of the piezoelectric ceramic elements 1, 1' are electrically connected to the metal caps 2, 2', and are further attached to the cap support member 4 by the annular members 5, 5'. Therefore, electrical continuity is established with the conductive support member 4 as well.

Therefore, the electrical terminal 6 is taken out by means such as soldering to the support member 4, and the piezoelectric ceramic elements 1, 1'
is connected to a common terminal 7 of the electrical outputs of. Furthermore, electrical terminals are taken out by means such as soldering from the electrode surfaces 8, 8' facing the adhesive surfaces of the piezoelectric ceramic elements 1, 1', and output terminals 9, 10 are also connected thereto, respectively. The cap support member 4 is further attached to the holding member 12 via a fitting portion 11 formed of a screw or the like. The holding member 12 is made of a material with high elastic loss, such as resin or vibration-proofing alloy, that can withstand the operating temperature range and operating pressure. Reference numeral 13 denotes an attachment member for attaching the holding member 12 to the liquid storage container wall 14.

The attachment member 13 is attached to the container wall 14 by means such as screws. The holding member 12 and the mounting member 13 are engaged with each other in a watertight manner through vibration-proofing materials 15, 15' such as rubber. 16, the holding member 12 is attached to the mounting member 1
As mentioned above, since the holding member 12 is made of a material with a large elastic loss, vibrations propagated from the container wall 14 via the mounting member 13 are used to hold the cap. This prevents the information from being transmitted to the member 12.

As is clear from the above description, the metal disk to which the piezoelectric ceramic element is bonded is formed into a cap shape, and the entire side wall portion of the cap is fixed uniformly to the support member using an annular member. Therefore, the boundary between the bottom of the cap and the side wall becomes a node of vibration, and compared to the conventional method of bonding a piezoelectric ceramic element to a flat metal plate and pressing the periphery of the flat metal plate, the peripheral fixing conditions can be satisfied more reliably. The resonance frequency of the vibration pickup becomes stable.

In other words, the resonant frequency of the peripheral fixed surface manipulation vibration is determined only by the thickness of the piezoelectric ceramic element to be bonded and the diameter of the cap, and if this resonant frequency is set to the frequency of the vibration to be detected, excellent detection sensitivity can be obtained. Become. Furthermore, since a plurality of vibration pickups can be attached to the same support member, by making the resonance frequencies of the individual vibration pickups the same or different, detection sensitivity at a predetermined frequency can be increased or correlation can be improved.

As described above, the present invention is characterized in that it is not only easy to manufacture industrially, but also that its resonance frequency is extremely stable under conditions where it is assembled in the atmosphere and used in a liquid.

Furthermore, since a plurality of vibration pickups can be attached to the same support member, a plurality of elements having the same resonance frequency or mutually different resonance frequencies can be selected. Furthermore, since the surface manipulation vibration is used compared to the wavelength of the focused elastic vibration in the liquid, its shape and dimensions are extremely small, and as a result, there is an advantage that the influence on the system to be measured is small.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a resonance type vibration pickup device according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of the main parts thereof. 1, 1'...Piezoelectric ceramic element, 2, 2'...
...metallic cap, 4...cap support member, 5, 5'... annular member. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A diaphragm formed into a cap shape by annularly extending and projecting a side wall from a peripheral edge of a metal disc, a piezoelectric element joined to a bottom of the diaphragm, and a piezoelectric element bonded to the bottom of the diaphragm. a support body having a portion that fits into the side wall portion; a holding member that cooperates with the fit portion of the support body to sandwich the side wall portion of the diaphragm; and a holder that holds the support body in a liquid container. 1. A resonant vibration pickup device characterized by having a member. 2. The resonance type vibration pickup device according to claim 1, wherein a plurality of diaphragms are arranged on the support body. 3. The holding member includes a first holding means that supports the support body;
and a second holding means for holding the first holding means in a liquid container, and at least one of the first and second holding means is made of a material with a large vibration damping coefficient. A resonant type vibration pickup device according to claim 1, characterized in that: 4. The holding member includes a first holding means that supports the support body;
and a second holding means for holding the first holding means in a liquid container, and an elastic body made of a rubber-like substance is provided between the first holding means and the second holding means. A resonant type vibration pickup device according to claim 1, characterized in that a resonant type vibration pickup device is provided.