JPH0580278B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Application of the Invention) The present invention provides a method for making vibration distribution uniform when exciting a plate-shaped piezoelectric (electrostrictive) vibrator that utilizes vibration in the thickness direction. This relates to an excitation method.

(Prior Art and its Problems) An example of a device that utilizes vibration in the thickness direction of a plate-shaped piezoelectric vibrator is an ultrasonic cleaning device.

For example, as shown in the cross-sectional side view and bottom view shown in FIGS.
In other words, the vibrator 1 has a width wider than the thickness direction, and at the same time, the length is sufficiently long compared to the resonant wavelength in the thickness direction.
are connected to the cleaning tank 2, which is individually glued to the tank bottom 2a, and to the excitation lines 3a, 3b from one end of the electrode metal films 1a, 1b of the vibrator 1. and an oscillator 4 that supplies excitation high-frequency power that matches the resonance frequency (for example, 1 MHz) of the oscillator 4. As is well known, the vibration of the vibrator 1 in the thickness direction is transmitted to the cleaning water 5 in the cleaning tank 2, thereby cleaning parts etc. immersed in the tank.

However, in such a cleaning device, the sound pressure partial pressure in the direction of vibration spread, that is, in the length direction of the vibrator surface, is generally caused by the electrode metal film 1a, as is clear from the water in the cleaning tank. It becomes smaller as it moves away from the connecting portion of the excitation lines 3a and 3b on the plane 1b, and this tendency becomes stronger as the size of the diaphragm increases as the size of the cleaning tank increases. Therefore, the occurrence of uneven cleaning cannot be avoided, resulting in a decrease in the performance of the cleaning device.

FIG. 2a shows the results of an experiment conducted to specifically illustrate the above. As shown in FIG. 2b, excitation lines 3a and 3
A commonly used vibrator 1 with a long side of 136 mm, a short side of 40 mm, and a thickness of 2 mm is provided with This is the result of actually measuring the distribution of vibration amplitude (vibration displacement) in the longitudinal direction of the vibrator 1 using a laser vibration distribution measuring device.

As this result shows, the vibration displacement is the excitation line 3a,
It is largest near the connection part of 3b, and becomes smaller as the distance from the connection part increases, and it was confirmed that this tendency remained the same in a separate experiment conducted on a product bonded to the bottom of the cleaning tank. Therefore, in order to improve the deterioration in cleaning performance due to uneven cleaning, it is essential to make the distribution of vibration amplitude uniform.

(Object of the Invention) The present invention has been made for the purpose of correcting the non-uniform distribution of vibration amplitude in the plate-shaped piezoelectric vibrator as described above, and the details thereof will be explained below with reference to the drawings.

(Means for Solving the Problems) The present invention does not apply an excitation voltage only at one point on the electrode metal film surface as in the conventional method, but instead applies an excitation voltage to the excitation line so as to compensate for the reduced vibration amplitude. This was achieved through experiments that revealed that the distribution of vibration amplitude can be made almost uniform by providing excitation lines at multiple points distributed in the direction away from the connecting part of 3a and 3b and excitation. and may be implemented, for example, by the structure described below with reference to FIGS. 3a to 3c.

In the example shown in FIG. 3a, excitation wires 3a and 3b are connected to the electrode metal films 1a and 1b at the center of both short sides of the vibrator 1, respectively. Electric power is applied to excite at two points at both ends.

Fig. 3b shows N locations including the side edges on both short sides of the electrode metal films 1a and 1b, and in the figure N locations are opposed to each other, including both ends and the central portion where the vibration amplitude is smaller than that at both ends. This is an example in which the excitation lines 3a and 3b are connected to excite at a plurality of locations at the same time.

In addition, in the example shown in FIG. 3c, one side of the electrode metal films 1a and 1b is connected to only one point of the excitation line 3b, and this is used as a common excitation line, and excitation is carried out by multiple excitation lines 3a on the other side. This example is advantageous for a vibrator that is used with one side adhered to the bottom of a cleaning tank or the like.

In this way, in the present invention, when the length dimension of the long side, that is, the length of the vibrator is relatively short, it is possible to excite at two points on the left and right ends on the short side.
As the length of the vibrator becomes longer, it is preferable to adopt the structure shown in FIGS. 3b and 3c, in which one or more excitation points are provided in the middle.

The excitation method of the plate-shaped piezoelectric vibrator described above connects the excitation line provided on the electrode metal film surface of the vibrator to multiple locations on at least one side, and the positional relationship of these connection locations is approximately symmetrical (point symmetrical, line symmetrical). ), but if the excitation lines described above are connected at a plurality of locations approximately symmetrically on the metal film surfaces of both electrodes, the distribution of vibration displacement can be made even more uniform.

(Operations and Effects of the Present Invention) As described above, if the excitation is performed at both the left and right ends of the short side of the vibrator, for example, the thickness of the vibrator spreads in the right direction due to the excitation at the left end shown in FIG. It is excited so that the part where the amplitude of the vibration in the thickness direction is large is overlapped with the part where the amplitude of the vibration in the thickness direction is small due to the simultaneous excitation of the right end. Therefore, the distribution of vibration displacement in the longitudinal direction of the vibrator is greatly improved and substantially uniform compared to the conventional structure in which excitation is performed only at one end.

FIGS. 4a and 4b show the results of actually measuring the distribution of vibration displacement in the thickness direction when exciting at two points on the left and right using the same vibrator used in the experiment shown in FIG. 2. As is clear from this, it can be seen that the cleaning is almost uniform over almost the entire length of the vibrator, and from this it can be seen that the unevenness of cleaning can be reduced compared to the conventional method.

However, as the length of the vibrator becomes longer, the vibration displacement at the center becomes smaller and the distribution of vibration displacement becomes uneven. In this case, for example, by adopting a method of vibrating not only at the left and right ends but also at the center as shown in FIG. 3B, the distribution of vibration displacement can be made uniform. Therefore, even if the cleaning tank becomes large and the diaphragm becomes large, the unevenness of washing can be reduced compared to the conventional method.

Furthermore, the present invention has been described above regarding a rectangular plate-shaped piezoelectric vibrator. However, even in the case of a disk-shaped piezoelectric vibrator that utilizes vibration in the thickness direction, as the diameter increases, the distribution of vibration displacement in the radial direction becomes uneven. Therefore, for example, as shown in Fig. 5, the non-uniform distribution of vibration displacement can be improved by exciting not only the center but also multiple points at approximately the same intervals around the center, and the present invention applies ultrasonic vibration. It can contribute to improving the performance of various devices.

[Brief explanation of the drawing]

Figures 1a and b are cross-sectional side views and bottom views of the ultrasonic cleaning device, and Figures 2a and b are distribution diagrams of vibration displacement in conventional vibrators and an explanation of the vibrators used for measurement. Figures 3a to 3c are diagrams of an embodiment of the present invention, Figure 4 is a distribution diagram of vibration displacement of a vibrator according to the present invention, and Figure 5 is an embodiment of the present invention in a disk-shaped piezoelectric vibrator. It is a diagram. 1... Vibrator, 1a, 1b... Electrode metal film, 2
...Cleaning tank, 2a... Tank bottom, 3a, 3b... Excitation line, 4... Oscillator, 5a, 5b... Connection member for excitation line.

Claims (1)

[Claims] 1. A plate-shaped piezoelectric vibrator that is excited by high-frequency power having a frequency corresponding to the resonant frequency in the thickness direction of the vibrator through electrode metal films provided on both surfaces of the plate-shaped vibrator to obtain vibration displacement in the thickness direction. In the excitation method when a single unit is excited, the excitation line provided on the electrode metal film surface is provided at a plurality of locations on at least one side, and the excitation lines are provided in a substantially symmetrical positional relationship with respect to the center point of the electrode metal film surface. A method for exciting a plate-shaped piezoelectric vibrator, characterized in that the distribution of generated vibrations is made uniform by exciting the plate-shaped piezoelectric vibrator.