JPS5917563B2 - bending vibration transducer - Google Patents

Description

Detailed Description of the Invention The present invention is composed of a highly stable constant elastic material, a piezoelectric ceramic material with a large electrical-mechanical coupling coefficient, and an adhesive such as solder, and is capable of converting an electrical input signal into a mechanical output signal or vice versa. This invention relates to a vibrating piece-shaped and tuning fork-shaped bending vibration transducer.

Bending vibration transducers are widely put into practical use mainly in low frequency bands as transducers for mechanical filters used in various communication devices and control devices.

In particular, it has recently been used in channel filters for communication path converters for carriers, and its applications are likely to continue to expand in the future.

A mechanical filter is a filter that uses ultrasonic waves as a medium and converts an electrical signal into a mechanical signal, which is then output as an electrical signal.

A transducer using a piezoelectric ceramic plate is most commonly used to convert an electrical signal into a mechanical signal, or vice versa.

The equivalent circuit analogous to a C circuit using a transducer using a piezoelectric ceramic plate is shown in Figure 1.

In FIG. 1, Lo, Co, and Ro are the equivalent inductance, equivalent capacitance, and equivalent resistance of the series resonance of the transducer, and Cd is the damping capacitance of the piezoelectric ceramic plate.

The capacity ratio γ, which indicates the performance of the converter, and the quality coefficient Q are (1), (
2) As in the formula (defined).

In Equation 2, ω is the series resonance angular frequency of the transducer.

On the other hand, the achievable passband width Δf of the mechanical filter is inversely proportional to the capacitance ratio γ.

Therefore, if the capacitance ratio γ is small, a broadband mechanical filter can be realized.

Acoustic piece-shaped bending vibration transducers that have been widely used in mechanical filters can be divided into the following two types of structures.

FIG. 2 shows the first structure of the vibrating flexural vibration transducer.

In the figure, an elastic plate 1 made of a constant elastic material is covered with a transverse effect piezoelectric ceramic plate 2 having a residual polarization 3 shown by an arrow in the thickness direction of the elastic plate, and an adhesive such as Nonder is attached to the upper surface in the length direction of the elastic plate 1. It has a structure in which the piezoelectric ceramic plate 2 and the elastic plate 1 are joined by
When an alternating current voltage of a predetermined frequency is applied between the lead wires 6 and 7 that are connected to Bending vibration indicated by dotted line 5 is performed.

This transducer is relatively simple in structure and easy to manufacture.

Furthermore, it is mainly used as a low-frequency narrowband filter because of its stability against temperature changes and changes over time.

However, since the electro-mechanical coupling coefficient of the stretching vibration of the piezoelectric ceramic plate that performs electro-mechanical conversion is small at about 0.3, the capacitance ratio of the transducer is large (therefore, the bandwidth of the mechanical filter that can be realized is narrow; As a result, the impedance of the filter also increases.

When using a converter with such a large capacitance ratio in order to widen the bandwidth of the mechanical filter or to match the impedance with an external circuit, it is necessary to add an electric circuit of C to the input and output sides. Must be.

However, there is a problem in that the size of the added electric circuit is equal to or larger than the size of the mechanical vibration system consisting of a transducer, a resonator, and a coupler.

FIG. 3 shows the second structure of the vibrating vibration transducer.

This transducer is a low capacitance ratio transducer that can remove mechanical filters and C electric circuits, and has two elastic plates 8 and 90 between which two pieces with different directions of residual polarization 12 and 13 are used. Longitudinal effect piezoelectric ceramic plates 10 and 11
are arranged so that the remanent polarization direction coincides with the length direction of the transducer, and each is bonded with the above-mentioned adhesive.

When an alternating current voltage of a predetermined frequency is applied to the two lead wires 17 and 18 fixed to the elastic plates 8 and 9, the transducer is caused to vibrate vertically as shown by arrows 14 and 15 in the piezoelectric ceramic plates 10 and 110. Bending vibration indicated by dotted line 16 is performed.

Electricity of the vertical vibration of the piezoelectric ceramic plate used in the above transducer
Since the mechanical coupling coefficient is generally as large as 0.5 to 0.6, the capacitance ratio of the transducer is small, and a mechanical filter having desired broadband characteristics can be obtained without using L and C additional electric circuits.

Furthermore, if one support wire (not shown) is connected to each of the elastic plates 8 and 9 sandwiching the piezoelectric ceramic plates 10 and 11 to the bending vibration node, the surface support wire will serve as a mechanical support member for the transducer. In addition to this, the lead wire can also serve the role of the lead wire described above, and the lead wire, which is likely to cause failure of the mechanical filter, can be removed.

However, since the latter transducer has more components than the former transducer, more manufacturing steps are required, and the remanent polarization directions of the two piezoelectric ceramic plates are made to be opposite to each other. There are some problems that you need to be careful about.

It is an object of the present invention to solve the problems of the above-mentioned bending vibration transducer, and to provide a transducer having a structure that can be added as a low capacitance ratio transducer and eliminate the C electric circuit. This is a low capacitance ratio converter for wideband mechanical filters that has superior characteristics, functionality, and manufacturability compared to other converters.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 4 shows an embodiment of the sound piece type bending vibration transducer of the present invention.

In FIG. 4, 19 and 20 are elastic plates made of a constant elastic material, and a piezoelectric ceramic plate 21 polarized in the direction of arrow 22 is placed between the two elastic plates 19 and 20 in the longitudinal direction. The two elastic plates 19 and 20 are arranged to be substantially perpendicular to the longitudinal direction, and the piezoelectric ceramic plate 2
This is a transducer having a structure in which elastic plates 19 and 200 one side end surface facing both electrode surfaces are connected in series with an adhesive such as solder.

Further, 26 and 27 are support wires attached to nodes of bending vibration, and also serve as lead wires.

When an alternating current voltage of a predetermined frequency is applied to the surface support wires 26 and 27, the piezoelectric ceramic plate 21 performs thickness shear vibration in the directions of arrows 23 and 24, and this vibration causes the transducer to perform a bending vibration as shown by a dotted line 25.

The transducer shown in FIG. 4 is a diagram in which the lengths of the two elastic plates 19 and 20 are approximately equal.

FIG. 5 shows the frequency response of the transducer of FIG.

In the figure, the horizontal axis represents frequency, and the vertical axis represents response level.

28 indicates a resonance point of the second-order bending vibration, and 29 indicates a resonance point of the fourth-order bending vibration.

In reality, even-numbered vibrations such as the sixth and eighth vibrations appear in a frequency range higher than the resonance point of the fourth vibration, but this is omitted in this figure.

The reason why only even-order vibrations appear in this embodiment is that the piezoelectric ceramic plate is arranged at the center of the transducer in the length direction.

FIG. 6 shows another embodiment of the present invention.

In the figure, the piezoelectric ceramic plate 32 is offset from the longitudinal center of the transducer.

30 and 31 are elastic plates having different lengths, and 32 is a piezoelectric magnetic plate that vibrates through thickness shear.

Support lines 30' and 31' are fixed at the nodes of the desired vibration mode.

FIG. 7 is a diagram showing the frequency response of the transducer of FIG. 6,
The horizontal axis of the figure shows frequency, and the vertical axis shows response level.

In the figure, 33, 34, 35 and 36 are respectively the first bending points.
The resonance points of the next, second, third and fourth vibrations are shown.

In addition, in the frequency range higher than the resonance point of the fourth-order vibration, the odd-order vibration
Resonance points appear in the order of even orders, but are omitted in this figure.

Next, the characteristics of the bending vibration transducer of the present invention will be described.

The characteristics of the bending vibrator of the present invention can be mainly divided into structural characteristics and characteristic characteristics.

(1) Structural Features A1 The transducer according to the present invention has an elastic plate and a piezoelectric ceramic plate connected in series in the longitudinal direction of the transducer, similar to the conventional bending vibration transducer shown in FIG.

1. The transducer according to the present invention requires only one piezoelectric ceramic plate, and there is no need to pay attention to the polarization direction of two piezoelectric ceramic plates arranged in parallel, unlike the conventional transducer shown in FIG. ,
This is advantageous in terms of control of the converter manufacturing process.

According to the present invention, a conversion r that does not require a lead wire can be obtained.

That is, by selecting the support wire fixed to the two elastic plates as the node of the desired vibration mode of the transducer, the support wire can also have the function of a lead wire.

(2) Characteristic Features A0 The transducer according to the present invention utilizes the thickness shear vibration of a piezoelectric ceramic plate.

In general, the electro-mechanical coupling coefficient of thickness shear vibration is larger than the electro-mechanical coupling coefficient of stretching vibration of piezoelectric ceramic plates used in conventional transducers and single thickness vibration.

Therefore, since the converter according to the present invention has a lower capacitance ratio than the conventional converter, a mechanical filter having broadband characteristics can be obtained without using an additional LC electric circuit.

The converter according to the present invention has a high quality factor Q of 3000 or more despite its low capacitance ratio.

Note that a Langevin type torsional vibration transducer having a capacitance ratio equivalent to that of the transducer of the present invention has a Q of about 300.

C1 The spurious characteristics of the converter according to the present invention are extremely good.

As shown in FIGS. 5 and 7, the transducer of the present invention exhibits almost no vibrations other than bending vibrations.

In particular, in the transducer shown in Fig. 4 in which the longitudinal center of the piezoelectric ceramic plate is aligned with the longitudinal center of the transducer, only even-order vibrations in bending are excited. The resonances can be separated considerably as shown in FIG.

As a result, if the transducer of the present invention is used in a mechanical filter, a filter with less spurious response can be realized.

Further embodiments of the converter according to the present invention will be described in 1 below.

FIG. 8 shows a structure in which a piezoelectric ceramic plate 38, which is polarized approximately perpendicularly to the length direction of the transducer and which performs thickness shear vibration, is continuously connected to one end surface of an elastic plate 370 with an adhesive such as solder in the longitudinal direction. This is a sound piece-shaped bending vibration transducer.

In this transducer, one elastic plate of the transducer shown in FIG. 4 or 6 is removed, and a lead wire 40 is attached to the end surface opposite to the surface joined to the piezoelectric ceramic plate 380 and the elastic plate 37. It is something.

The support wire 39 is fixed to a vibration node of a desired vibration order, supports the transducer, and functions as the other lead wire for the lead wire 40.

The converter shown in FIG. 8 has fewer components than the converters shown in FIGS. 4 and 6, and is easier to manufacture.

Figure 9 uses two piezoelectric ceramic plates, and the angle is 41°42.
43 is an elastic plate, 44 and 45 are piezoelectric magnetic plates, 46.47,
Reference numeral 48 indicates a support wire that also functions as a lead wire.

When an AC voltage of a predetermined frequency is applied between the support wires 46 and 47, this transducer vibrates in a bending vibration mode, and this vibration is mechanically-electrically converted by the piezoelectric ceramic plate 45 to the terminal 4.
8 and 47 as electrical output signals.

That is, it can be used as a band-pass type filter with one converter.

Note that if the terminals 46 and 48 are electrically connected in common and an electric signal is applied between them and the terminal 47, it can also be used as a transducer similar to those shown in FIGS. 4, 6, and 8.

FIG. 10 shows an example in which the present invention is applied to a tuning fork-shaped bending vibration transducer.

In general, a tuning fork type vibrator can operate at a lower frequency than a tone piece type vibrator and can be made more compact, so it is widely used at a lower frequency than a tone piece type vibrator.

In Fig. 10, 49° 50 and 51 are elastic plates made of a constant elastic material, of which 50 has two arms.
formed into a shape.

52 and 53 are piezoelectric ceramic plates that perform thickness shear vibration;
56 is a support line.

Arrows 54 and 55 indicate the remanent polarization direction of the piezoelectric ceramic plate, respectively.

When an alternating current voltage of a predetermined frequency is applied between the lead wires 57 and 58, the transducer vibrates in a symmetrical vibration mode as shown by dotted lines 60 and 61.

This vibration is mechanically-electrically converted by the piezoelectric ceramic plate 53 and output as an electrical output signal between the lead wires 58 and 59.

Therefore, like the transducer shown in FIG. 9, one transducer can be used as a band-pass type filter.

Note that it is also possible to connect the terminals 57 and 59 electrically in common and apply an electric signal between them and the terminal 58 to operate in the same manner as the above-mentioned transducer.

As explained in detail above, the bending vibration transducer according to the present invention has a small number of components, a simple structure, and excellent manufacturability.Furthermore, since a low capacitance ratio can be obtained, a broadband mechanical filter can be easily obtained. It has extremely excellent effects such as

[Brief explanation of drawings]

Figure 1 is an equivalent circuit diagram analogous to the C circuit of a piezoelectric side dynamic transducer; Figures 2 and 3 are perspective views showing the structure of a conventional bending vibration transducer; Figures 4 and 6; 8 and 9 are perspective views showing a vibrating piece-shaped bending vibration transducer according to the present invention,
5 and 7 are frequency response diagrams of the transducers of the embodiments shown in FIGS. 4 and 6, respectively, and FIG. 10 is a perspective view showing the embodiment of the tuning fork-shaped bending vibration transducer according to the present invention. be. 19.20, 30, 31, 37, 41, 42°43.4
9,50,51...Elastic plate, 21.32°38
．． 44, 45, 52, 53... Piezoelectric ceramic plate, 2
2.54,55...Remanent polarization direction.

Claims (1)

[Claims] 1. Consisting of at least one elastic plate made of a constant elastic material, at least one piezoelectric ceramic plate that performs electrical-mechanical signal conversion in a thickness-shear vibration mode, and an adhesive such as solder. In the transducer, the elastic plates and the piezoelectric ceramic plates are arranged in tandem one after another in the length direction, and the residual polarization direction of the piezoelectric ceramic plates is substantially perpendicular to the length direction of the elastic plates. A bending vibration transducer characterized in that the electrode surface of the piezoelectric ceramic plate is further bonded to one end surface of the elastic plate facing the electrode surface in the form of a vibrating bar using the adhesive. 2. In a transducer composed of an elastic plate, a piezoelectric ceramic plate, and an adhesive, the elastic plate and the piezoelectric ceramic plate are arranged in series in the length direction of the arm length of the tuning fork vibrator, and the residual polarization of the piezoelectric ceramic plate is The direction is substantially perpendicular to the length direction of the elastic plate constituting the arm portion and substantially coincides with the direction of vibration displacement, and the electrode neck of the piezoelectric ceramic plate is positioned at one end face of the elastic plate opposite to the electrode surface. and a flexural vibration transducer, characterized in that the above-mentioned adhesive is used to combine the flexural vibration transducer into a tuning fork shape.