JPS5924975Y2 - Piezoelectric remaining amount detection device - Google Patents

Description

[Detailed description of the invention] This invention detects the level of liquid such as water or fine powder in a container by changing the vibration of a piezoelectric ceramic plate attached to it, and determines whether the remaining amount has fallen below a certain value. The present invention relates to a piezoelectric remaining amount detecting device, and more specifically, it provides a piezoelectric remaining amount detecting device that is easy to manufacture and operates stably.

Conventionally, this type of piezoelectric remaining amount detection device is shown in FIG. 1a.

The structure is as shown in b, and in the figure, 1 is a circular diaphragm made of a metal plate or a printed circuit board, etc., 2 is a piezoelectric ceramic plate bonded to this diaphragm 1, and a separation band 3 is provided on the surface. divided electrodes 4, 4' are formed, and the electrodes 4, 4'
A lead wire 5.5' is connected to each of the wires 4'.

Further, the electrode on the back surface of the piezoelectric ceramic plate 2 is connected to the shield wire 6 via the diaphragm 1.

The peripheral portion of the diaphragm 1 is fixed to one end of a cylindrical case 7 made of metal or resin, and a flat plate 8 is further fixed to the upper surface of the cylindrical case 7. 7. It is housed in a space defined by a flat plate 8.

When using a piezoelectric remaining amount detection device with such a structure, place it in a liquid such as water or fine powder in a container, fix it in the container, and then connect the lead wire 5゜5' and the shield wire. 6 to an external circuit to vibrate the diaphragm 1 at a frequency that substantially matches the resonance frequency of the diaphragm 1.

In this state, if the amount of the object to be measured is large and the diaphragm 1 is inside the object to be measured, the vibration of the diaphragm 1 is suppressed by the object to be measured, and the output voltage is small, but the amount of the object to be measured is If the remaining amount of the object to be measured falls below diaphragm 1,
The diaphragm 1 vibrates with a large amplitude, and a large output voltage can be obtained.

That is, the remaining amount of the object to be measured can be detected based on the magnitude of this output voltage.

However, in the conventional structure, a rectangular piezoelectric ceramic plate 2 is used as shown in Fig. 1 a, l), and split electrodes 4 and 4' are formed on the left and right sides of the piezoelectric ceramic plate 2. However, since one electrode was used to drive the diaphragm 1 and the other was used to extract electrical signals, the diaphragm 1 was driven in a position that was biased toward the periphery from the center, and as a result, the diaphragm 1 The vibration is not symmetrical with respect to the center, resulting in the inconvenience that the output voltage becomes unstable.

In particular, when the detection device is installed perpendicular to the surface of the object to be measured, for example, the liquid surface, the driving divided electrode 4 is positioned parallel to the liquid surface as shown in Figure 2a. The output voltage is large in the case of Fig. 2 a, and the output voltage is small in the case of Fig. 2 (a). However, there was a drawback that the liquid level could only be detected at a certain level.

Moreover, it is extremely difficult to attach the piezoelectric ceramic plate 2 to the diaphragm 1 so that the divided electrodes 4, 4' always face in a fixed direction, which is a factor in increasing the price.

The present invention was devised in order to solve such conventional drawbacks, and FIGS.
This will be explained using the drawing of l).

In addition, in FIG. 3 a, l), the same parts as those shown in FIG. 1 a, l), which are drawings of the conventional example, are given the same numbers and explanations are omitted.

In the figure, reference numeral 9 denotes a disk-shaped piezoelectric ceramic plate, and on the surface of the piezoelectric ceramic plate 9 on the opposite side from the side to which it is attached to the diaphragm 1, divided electrodes 10 and 10' are arranged at intervals separated by separation strips 11. It is formed in open concentric circles.

That is, according to the piezoelectric remaining amount detection device of the present invention, since the driving electrode is located point-symmetrically with respect to the center of the diaphragm 1, the vibration of the diaphragm 1 is also center-symmetrically, and a stable output voltage is obtained. can be obtained.

Further, even when the detection device is used vertically, since the electrodes are symmetrical about the center, the magnitude of the output voltage does not vary depending on the orientation of the electrodes, and a constant output voltage can be obtained.

Furthermore, when attaching the piezoelectric ceramic plate 9 to the diaphragm 1, there is no need to consider the orientation of the divided electrodes 10, 10' of the piezoelectric ceramic plate 9, which facilitates manufacturing.

As described above, according to the present invention, a stable output voltage can be obtained, a constant output voltage can be obtained without being affected by the mounting state of the detection device, and it can be easily manufactured. It is possible to obtain a piezoelectric residual amount detecting device which has a very high practical value.

[Brief explanation of drawings]

Figure 1 a, l) is a plan view and cross-sectional view showing a conventional piezoelectric remaining amount detection device, and Figure 2 a, l) is an explanatory diagram to explain the drawbacks caused by differences in the mounting state of the detection device. , FIGS. 3a and 3l) are a plan view and a sectional view showing a piezoelectric remaining amount detection device according to an embodiment of the present invention. 1... Vibration plate, 9... Piezoelectric ceramic plate, 1
0.10'...Divided electrode.

Claims (1)

[Scope of utility model registration request] Concentric split electrodes are provided on one side of a disk-shaped piezoelectric ceramic plate, and a diaphragm is attached to the other side of the piezoelectric plate, and the remaining amount of liquid or fine powder is detected by vibration changes of this diaphragm. Piezoelectric remaining amount detection device.