JPS5953493B2 - 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 performed by a piezoelectric element (driving is done by one piezoelectric element), and the gain is determined by the piezoelectric element for vibration detection (where the maximum amplitude always occurs) with respect to the voltage applied to the driving piezoelectric element. This is the ratio of the output voltages (in decibels) expressed in decibels. Note that this cylindrical vibrator is made of constant elastic material (Young's modulus is 19500 kg/1,
The specific gravity is 8.15), the outer diameter is 20 mm, and the thickness is 0.
．． It has a diameter of 1 mm and a length of 30 mm. In this figure, A, B, C, D, and E have 3rd, 4th, 2nd, 5th, and 6th in-plane vibration modes, respectively, and 1st-order axial vibration modes. It shows the gain in case. Also,
F and G indicate gains when the in-plane vibration modes are fifth-order and fourth-order, respectively, and the axial vibration modes are both second-order. In this cylindrical vibrator, the third-order vibration mode (
The frequencies of each of the vibration modes of FIG. 1A) and the second vibration mode (FIG. 1C) are very close to the frequencies of the fourth vibration mode (FIG. 1B). Moreover, their gains are larger than those of the fourth vibration mode. Conventionally, when the frequencies of two or more vibration modes are close to each other, a piezoelectric element is installed 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 to provide a constant value. However, with this conventional method, it is impossible to vibrate a cylindrical vibrator exhibiting the characteristics shown in FIG. 1 in a fourth-order vibration mode. Also,
Even when the frequencies of each vibration mode are not very close to each other, the effect of the conventional device that performs mode relocation using only a bandpass filter is small. 5
An object of the present invention is to realize a vibratory transducer with good mode relocation, that is, to realize a vibratory transducer that can reliably vibrate a cylindrical vibrator in a constant vibration mode.

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

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 has 4 in-plane vibration modes.
The next step is to obtain a one-order axial vibration mode. In the figure, 1 is a cylindrical vibrator main body, and 2 and 3 are driving piezoelectric elements having the same characteristics. The piezoelectric element 3 is located at the other antinode of the fourth-order vibration mode (the part where the piezoelectric element 2 is attached forms one antinode), and also between the antinode where the piezoelectric element 2 is attached and the center of the cylinder. It is mounted on the belly in a non-symmetrical position. In this embodiment, the piezoelectric element 3 is mounted at a position shifted by 90 degrees from the piezoelectric element 2. The axial mounting positions of the piezoelectric elements 2 and 3 are as follows:
This is the node portion 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. 4 is the antinode of the fourth vibration mode (piezoelectric elements 2 and 3
It is a piezoelectric element for vibration detection that is attached to an antinode (any antinode other than the antinode to which it is attached).

In this embodiment, the antinode to which the piezoelectric elements 2 and 3 are attached is
Since both peaks and valleys occur in the fourth vibration mode, driving voltages of the same phase are applied to the piezoelectric elements 2 and 3. The vibration of the cylindrical vibrator constructed in this way will be explained.

Figure 3 shows the circular oscillator body 1 having the same shape as that in Figure 1.
This figure shows the characteristics when vibrated by the piezoelectric elements 2 and 3 attached at the positions shown in FIG. The gain in this case was also determined by bonding a piezoelectric element for vibration detection to the portion where the maximum amplitude occurs. Therefore, it is not determined based on the output signal of the piezoelectric element 4 shown in FIG. As is clear from comparing the characteristics shown in FIG. 3 and the characteristics shown in FIG. ing.

As a result, a large alternating voltage is output from the piezoelectric element 4 only when the cylindrical vibrator is vibrating in the fourth-order vibration mode. In addition to B, there is G in the fourth-order vibration mode, but since they are separated by 6 kHz and the gain is not much different, by passing the output signal of the piezoelectric element 4 through a filter,
Only signals whose in-plane vibration mode is fourth-order and whose axial vibration mode is first-order can be easily selected. With this force f, the cylindrical vibrator as a part of the vibration transducer can be reliably vibrated in this vibration mode. In addition, in Fig. 2, by applying a drive voltage of opposite phase to the piezoelectric elements 2 and 3, the odd-order and fourth-order vibration modes can be reset, and a signal of only the second-order vibration mode can be obtained. .

FIG. 4 is a characteristic diagram obtained under the same conditions as FIGS. 1 and 3. 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 denoted by the same reference numerals and explanations are omitted).

This cylindrical vibrator is used to obtain a third-order in-plane vibration mode and a first-order axial vibration mode. For this reason,
The piezoelectric element 3 is installed at a position offset by 60 degrees from the piezoelectric element 2, and the antinode of the vibration mode (tertiary) in which the piezoelectric elements 2 and 3 are installed moves in opposite directions. Therefore, a driving voltage having a phase opposite to that of the piezoelectric element 2 is applied to the piezoelectric element 3. FIG. 6 is a characteristic diagram when the cylindrical vibrator main body 1 having the same shape as that in FIG. 2 is used. 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 applies to the second to fourth vibration modes, but the same applies to the other vibration modes.

Furthermore, the mounting position of the piezoelectric element 3 only needs to be at the antinode of the desired vibration mode. However, the antinode must not be located at a symmetrical position with respect to the antinode to which the piezoelectric element 2 is attached and the center of the cylinder. 7. This is because the symmetrical position reduces the constraints on the deformation that acts as mode rejudgement.

Furthermore, although an example has been shown in which the driving piezoelectric elements are arranged at two antinodes of the vibration mode, they may be attached at three or more antinodes. In this way, the model logic execution function is further improved. In this case, it is necessary to drive the piezoelectric element group attached to the antinodes of the peak (or valley) and the piezoelectric element group attached to the antinodes of the valley (or peak) in opposite phases (piezoelectric If elements with opposite polarities are used, they may be driven with the same five phases). 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. can be done.

Further, the driving means is not limited to one using a piezoelectric element, but may be one using electromagnetic force or electrostatic force. As explained above,
According to the present invention, it is possible to realize a vibrating transducer with good mode relocation.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] 1 comprising a cylindrical vibrator and a driving means for applying an external force to at least two antinodes of a constant vibration mode in in-plane vibration of the cylindrical vibrator that are not located at symmetrical positions with respect to the center of the cylinder, A vibrating transducer characterized in that the vibrator is configured to vibrate.