JPS5953494B2 - vibrating transducer - Google Patents

Description

Detailed Description of the Invention The present invention utilizes the fact that the natural frequency of a vibrator changes depending on the density of the fluid surrounding the vibrator and the tension applied to the vibrator. This relates to a vibrating transducer in which the value is determined from changes in the natural frequency of the vibrator.

FIG. 1 is a diagram showing the drive frequency-gain characteristics of a cylindrical vibrator with one end fixed.

Driving and vibration detection of this cylindrical vibrator are each performed with one piezoelectric element, and the gain is determined by the output voltage of the vibration detection piezoelectric element (always placed at the position where the maximum amplitude occurs) with respect to the voltage applied to the driving piezoelectric element. The ratio is expressed in decipels. This cylindrical vibrator is made of constant elastic material (Young's modulus is 19,500 kg/1, specific gravity is 8.
15), outer diameter 20 times, thickness 0.1 times,
It has a length of 30 layers. In this Figure 1, A,
B, C, D, and E each have 3 vibration modes of in-plane vibration.
It shows the gain when the vibration mode in the axial direction is the first order for the second order, fourth order, second order, fifth order, and sixth order.

Furthermore, F and G indicate gains when the in-plane vibration mode is fifth-order and fourth-order, and the axial vibration mode is both second-order. In this cylindrical vibrator, the frequencies of the third-order vibration mode (Fig. 1A) and the second-order vibration mode (Fig. 1C) are equal to the frequencies of the fourth-order vibration mode (Fig. 1B). Very close. Moreover, their gains are larger than those of the fourth-order vibration mode. Conventionally, when the frequencies of two or more vibration modes are close to each other, a piezoelectric element is placed at the antinode of the vibration mode to be obtained, and the signal obtained from the piezoelectric element is fed back through a band-pass filter. A method of vibrating in a fixed vibration mode is used, but with this conventional method, it is impossible to make a cylindrical vibrator exhibiting the characteristics shown in Figure 1 vibrate in a fourth-order vibration mode. . Further, even if the frequencies of the vibration modes are not very close to each other, the effect is small in conventional devices that perform mode relocation using only a bandpass filter. An object of the present invention is to realize a vibrating transducer with good mode relocation.

The present invention will be explained in detail below using the drawings.

J Fig. 2 is a diagram showing a cylindrical vibrator of a vibratory transducer according to the present invention, where A is a view seen from the open end side, and the mouth is a view seen from the side. This cylindrical vibrator is used to obtain a fourth-order in-plane vibration mode and a first-order axial vibration mode. In the figure, 1 is a cylindrical vibrator main body, 2 and 3 are piezoelectric elements for vibration detection having the same characteristics, and 4 is a piezoelectric element for driving. The portion to which the piezoelectric element 4 is attached forms an antinode in the fourth vibration mode. The piezoelectric elements 2 and 3 are 4
The piezoelectric elements 2 and 3 are attached to other antinodes of the next vibration mode (anodes other than the anodes to which the piezoelectric element 4 is attached) so that they are not in symmetrical positions with respect to the center of the cylinder. In this embodiment, the piezoelectric element 2 is mounted opposite to the piezoelectric element 4, and furthermore, the piezoelectric element 3 is mounted at a 99° angle with respect to the piezoelectric element 2.
It is installed at a position offset by 0°.゛Piezoelectric element 2
The axial mounting positions of 4 to 4 are at the nodes of the axial vibration mode of the cylindrical vibrator body 1, and therefore near the fixed end of the cylindrical vibrator body 1 in this embodiment. Piezoelectric elements 2, 3
Since the antinodes to which the They are connected to each other, and the voltage between both connection terminals is calculated as an output signal to obtain a voltage indicating the vibration of the cylindrical vibrator (hereinafter referred to as vibration output voltage).
The vibration of the cylindrical vibrator configured in this way will be explained.

FIG. 3 shows the characteristics when the cylindrical vibrator main body 1 of FIG. 2 has the same shape as that of FIG. 1. The gain in this case is the ratio of the vibration output voltage to the voltage applied to the piezoelectric element 4 expressed in decibels.
As is clear from comparing the characteristics shown in FIG. 3 and the characteristics shown in FIG. 1, in this embodiment, the odd vibration modes and the secondary vibration modes are extremely weakened. In addition to B, there is G in the fourth-order vibration mode, but both are 6
Since the kHz is different and the gain is not much different, by passing the vibration output voltage through a filter, the in-plane vibration modes can be divided into four.
In the following, it is possible to easily select a signal whose axial vibration mode is first-order. Therefore, the cylindrical vibrator as part of the vibratory transducer can be reliably vibrated in this vibration mode. In addition, in FIG. 2, the outputs of piezoelectric elements 2 and 3 are subtracted (the positive output terminal of piezoelectric element 2 and the negative connection terminal of piezoelectric element 3 are connected, and the negative output terminal of piezoelectric element 2 and the negative side connection terminal of piezoelectric element 3 are If the positive side output terminal of the oscilloscope is connected and the voltage between the two connection terminals is used as the output signal to obtain the vibration output voltage, it is possible to perform re-ejection at odd-number times and in the fourth-order vibration mode. can.

Further, by passing the vibration output voltage through a filter, it is possible to easily obtain a signal of only the second-order vibration mode. Fourth
The figure shows the characteristics when the above-mentioned subtraction is performed in the structure of FIG. 2. Comparing FIG. 4 with FIG. 1, it can be seen that good mode relocation is achieved. FIG. 5 is a view of a cylindrical vibrator according to another embodiment of the present invention, viewed from the open end side (portions corresponding to those in FIG. 2 are given the same reference numerals and explanations are omitted).

This cylindrical cylindrical vibrator has a third-order in-plane vibration mode and a first-order axial vibration mode. Therefore, the piezoelectric element 3 is mounted at a position shifted by 60 degrees with respect to the piezoelectric element 2. Furthermore, since the antinodes of the vibration mode (tertiary) to which the piezoelectric elements 2 and 3 are attached move in opposite directions, the configuration is such that the output of the piezoelectric elements 2 and 3 is subtracted to obtain the vibration output voltage. ing. FIG. 6 shows the characteristics when the cylindrical vibrator body 1 of FIG. 5 has the same shape as that of FIG. 1. In this case, the second-order and fourth-order vibration modes are well repositioned. Therefore, this cylindrical vibrator can reliably vibrate in the third-order in-plane vibration mode. The above explanation is for the second to fourth vibration modes, but the same applies to the other vibration modes.

Furthermore, the mounting positions of the piezoelectric elements 2 and 3 only need to be at the antinode of the desired vibration mode. However, both piezoelectric elements 2
, 3 are attached to the antinode at a symmetrical position with respect to the center of the cylinder, it is not possible to expect much effect of mode rigidity. Furthermore, although an example has been shown in which the piezoelectric elements for vibration detection are arranged at two antinodes of the vibration mode, they may be attached at three or more antinodes. In this way, the mode relocation function is further improved. In addition, although we have shown a device that performs addition and subtraction by connecting the output terminals of piezoelectric elements 2 and 3,
The charge generated by the piezoelectric element may be received by a charge amplifier, or the generated voltage may be received by a buffer amplifier, and the outputs of these amplifiers may be added or subtracted using an operational amplifier or the like. 9. Although the effect of the present invention (mode redirection) has been shown for a specific cylindrical vibrator with one end fixed, as is clear from the above explanation, the same effect can also be obtained with a cylindrical vibrator with both ends fixed, etc. I can do it.

Further, the vibration detecting means is not limited to one using a piezoelectric element, and it is also possible to use electrostatic, electromagnetic, optical, etc. vibration detecting means. As described above, according to the present invention, it is possible to realize a vibrating transducer with good mode redirection.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the driving frequency-gain characteristics of a cylindrical vibrator with one end fixed, FIG. 4 is a characteristic diagram of a cylindrical oscillator of another vibrating transducer according to the present invention, and FIG. 5 is a configuration of a cylindrical oscillator of another vibrating transducer according to the present invention. figure,
FIG. 6 is a characteristic diagram of the cylindrical vibrator shown in FIG. 1... Cylindrical vibrator body, 2, 3... Piezoelectric element for vibration detection, 4... Piezoelectric element for drive.

Claims (1)

[Claims] 1 comprising a cylindrical vibrator and a detection means for detecting the vibration of at least two antinodes that are not located at symmetrical positions with respect to the center of the cylinder among the antinodes of a constant vibration mode in the in-plane vibration of the cylindrical vibrator; A vibratory transducer characterized in that it is configured to add or subtract each output signal of the cylindrical vibrator to obtain a signal indicating the vibration of the cylindrical vibrator.