JPS58202699A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To obtain a speaker having high energy converting efficiency and flat output sound pressure frequency characteristics, by forming an electric signal input terminal of an oscillator on a frame for a piezoelectric speaker consisting of a diaphragm made of a bimorph oscillator and a polymer material film and a frame. CONSTITUTION:The utmost outer circumference part 53c of a diaphragm 53 is adhered with an adhesive to the adhering surface 55a of a frame 55 made of a metal such as brass, etc. The electrode surface of the diaphragm 53 is connected electrically to the frame 55 by means of the surface 55a. Then a piezoelectric electro-acoustic transducer 51 is adhered to the frame 55 so that the frame 55 functions as an electric signal input terminal. A terminal plate 56 connected electrically to the frame 55 and then adhered to the frame is connected with the electrode of piezoelectric ceramics 52a and an electrode 56a of the plate 56 via a lead wire 54. The plate 56 functions as another electric signal input terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric speaker using a bimorph vibrator.

1(A) and 1(B) are a plan view and a side view of a conventional piezoelectric electroacoustic transducer, and FIG. 2 is an operation of the piezoelectric electroacoustic transducer showing the operating principle of FIG. 1. It is a diagram.

2 is a piezoelectric ceramic made of lead zirconate titanate (1) Z T )-based porcelain, etc., and 6 is a thin metal plate made of titanium, stainless steel, brass, etc., and the piezoelectric ceramic 2 is attached concentrically to the metal plate B. By attaching the piezoelectric electroacoustic transducer 1 to an asymmetric circular bimorph, the piezoelectric electroacoustic transducer 1 is constructed.

Generally, when an AC voltage is applied to a thin disc-shaped piezoelectric ceramic, the lowest resonance phenomenon occurs as a radial vibration, and at this time the diameter of the disc-shaped piezoelectric ceramic slightly expands or contracts. However, the expansion and contraction of the piezoelectric ceramic 2 results in distortional vibrations because it is bonded to the metal plate A as shown in FIG. That is, when the periphery of the metal plate 6 is fixed, when a positive voltage is applied to the terminals 4 and 5 as shown in FIG. When the piezoelectric ceramic 2 is distorted and a negative voltage is applied to the terminals 4 and 5, the piezoelectric ceramic 2 contracts as shown in FIG.

Therefore, if the polarity of terminal 4 is changed continuously to C+) (-'), that is, if an AC signal is applied within the audible frequency range, distortion vibration of the metal plate B will occur, and an audible sound can be generated. It has become.

In this way, the conventional piezoelectric electroacoustic transducer 1 generates audible sound by converting the simple expansion and contraction of the piezoelectric ceramic 2 in the diametrical direction into distorted vibration of the metal plate 6, which is a diaphragm. The vibration of the piezoelectric ceramic 2 could not be directly converted into the vibration of the metal plate B, resulting in an electroacoustic transducer with poor energy conversion efficiency. Furthermore, since the metal plate 6 is used as the diaphragm, the lowest resonant frequency f that determines the reproduction frequency band of the piezoelectric electroacoustic transducer 1.

(hereinafter abbreviated as f.) becomes high, and has the disadvantage that it is not possible to reproduce bass sounds.

One of the drawbacks of the conventional piezoelectric electroacoustic transducer 1 described in -4- is the poor energy conversion efficiency. Is there anything I can do to hope for things to get better?
One way to realize this idea is to use a bimorph vibrator instead of the piezoelectric ceramic 2.

Figure 3 is a configuration diagram of a bimorph oscillator.
Figure (A) shows a series type bimorph, and Figure 3 ([3) shows a parallel type bimorph.

To put it simply, a bimorph resonator is a piece of piezoelectric ceramic that stretches and contracts in the length direction, and is bonded together so that when one stretches, the other contracts, causing the whole to undergo bending vibration (flexural bimorph). If the shape of the ceramic is a disc as shown in Fig. 1, the bimorph vibrator itself can produce distortive vibrations as shown in Fig. 2.

The series bimorph 10 shown in FIG. 3(A) is made up of two piezoelectric ceramic plates 12a and 12b bonded together with electrical contacts.
With the direction of the component w as j1η (parallel polarization; arrow 1
6a, 161) indicate the polarization direction), and the outer electrode is used as an electrical signal input terminal.The parallel bimorph 11 shown in FIG. in the evening (evening; arrows 17a, 17b
(indicates the polarization direction), the outer electrodes are short-circuited, and the outer electrodes and the center electrode are used as electrical signal input terminals.

In this way, bimorph resonators can be divided into series types and parallel types depending on how the electrical signal input terminals are taken out, but in both cases, bending vibration ( 7. "It is there" so that it can cause distortion vibrations).

FIG. 4(A) and FIG. 4(B) are a plan view and a cross-sectional view of an electroacoustic transducer constructed for the purpose of effectively utilizing the vibration energy of piezoelectric ceramics. In place of the ceramic 2, an electroacoustic transducer is shown in which a disk-shaped bimorph vibrator shown in No. 31-1 is adhered to a metal plate.

22 is two pieces of pressure η, ceramics 22, 1.221)
This is a bimorph resonator in which a bimorph structure is formed by bonding two types of materials together, and in this example, it is a series bimorph. 26 is a thin metal plate similar to that shown in FIG.
An electroacoustic transducer 21 is constructed by attaching bimorph vibrators 22 concentrically to a plate 26. The electroacoustic transducer 21 configured as described above causes the bimorph vibrator 22 to distortly vibrate by applying an alternating current signal to the bimorph vibrator 22.
This is an attempt to generate an audible sound by directly distorting and vibrating a metal plate 26 to which is bonded by a bimorph vibrator 22.

FIG. 5 is a partial sectional view of the 41st unit 1, and is an analysis of the operation of the electroacoustic transducer 21 shown in FIG.

24 and 25 are electric signal input terminals, and when the polarity of the electric signal input terminals 24 and 25 is (''-) and (-), respectively, the piezoelectric ceramic 22a is extended, and the piezoelectric ceramic 1 It is assumed that the 22b side is formed to contract (of course, the direction of expansion and contraction may be opposite).

Under these conditions, the operation of the electroacoustic transducer 21 when the polarities of the electrical signal input terminals 24 and 25 become (''-) and (-), respectively (Figure 5 (A)) is analyzed using Figure 5. I'll try it.

In this state, if the bimorph oscillator 22 operates independently, the piezoelectric ceramic 22 a (the rule is broken and the piezoelectric ceramic 22 b side shrinks, so the piezoelectric ceramic 22 a Similarly, if the metal plate 26 and the piezoelectric ceramic 22b attached to the metal plate 26 are moved, the piezoelectric ceramic 22b will shrink, as shown in FIG. 5(C). In this case, the piezoelectric ceramic 221] side is distorted in a bowl-like manner.Therefore, the operation of the electroacoustic transducer 21 tends to be distorted in opposite directions as shown in FIGS. 5(B) and 5(C). , the overall distortion becomes smaller, and the 561st (D)
You can see that it will look like this.

In this way, the electroacoustic transducer 2 is configured to directly and effectively utilize the distortion vibration of the bimorph vibrator 21 alone.
It can be seen that 1 achieved its purpose and became an inefficient '□':.

FIGS. 6(A) and 6(B) are a plan view and a sectional view of a piezoelectric electroacoustic transducer θ) configured to eliminate the above-mentioned drawbacks, and FIG. 6(C) is a FIG. 6(B) is a partially enlarged sectional view of FIG. 6(B).

62 is a bimorph vibrator in which two piezoelectric ceramics 32a, 621) are bonded together to form a bimorph structure; 1,321.322 is an electrode attached to the piezoelectric ceramic 32a, and 626.624 is the piezoelectric ceramic 621.
) shows the electrode attached. In this embodiment, the bimorph resonator 32 is a series bimorph with electrodes 621 and 624 as electrical signal input terminals. Reference numeral 66 denotes a diaphragm made of a polymer material film such as aromatic polyester polyarylate, polysulfone, polycarbonate-1, polyethylene terephthalate-1, polyethersulfone, polypropylene, etc. Almost the entire surface is coated with film technology - that is, a technique in which a film is formed by vapor deposition or chemical plating and then etched to form a film in the desired shape, or a film in the desired shape is formed by mask vapor deposition or mask plating. Electrode 6
The bimorph resonator 62 is bonded onto the electrode 64 of the diaphragm 36 so that the diaphragm 63 covers the entire surface of one electrode surface 624 of the bimorph resonator 62. 62 electrodes 621 and diaphragm 66
A piezoelectric electroacoustic transducer 31 is constructed in which the electrode 64 serves as an electrical signal input terminal.

As mentioned above, since the piezoelectric electroacoustic transducer 31 shown in FIG. 6 uses the diaphragm 36 made of a polymer film, it is different from the diaphragm 23 made of a metal plate as shown in FIG. Young's modulus is very small, and the diaphragm 66 is a bimorph oscillator 6.
2, and the distortion of the bimorph vibrator 62 is directly converted into the distortion of the diaphragm 66. Therefore, if the bimorph vibrator 62 is caused to vibrate in a distorted manner, that is, if an AC signal is applied to the electrodes 321 and 64, which are electrical signal input terminals, the diaphragm 66 to which the bimorph vibrator 62 is bonded will also vibrate in a distorted manner. Therefore, a piezoelectric electroacoustic transducer with high energy conversion efficiency that can generate audible sound is constructed.

FIG. 7 is a cross-sectional view showing an example in which the piezoelectric electroacoustic transducer 61 of FIG. 6 is incorporated into a watch case.

33' is a diaphragm made of a polymer film made by thermoforming the diaphragm 66 shown in FIG. There is. 60 is a watch module (shown with an imaginary line as it has no important meaning to the present invention);
38 and 39 are springs, the spring 68 makes an electrical connection between the electrodes of the bimorph oscillator 62 (not shown) and the module 0, and the spring 69 connects the diaphragm 63 (not shown).
An electrical connection is made between the electrode of ' and the module 60. That is, the watch module 30 via the springs 68,39
The electrical signal output by the piezoelectric electroacoustic transducer 41
is transmitted to generate an audible sound.

42 is a body, and 46 is a back cover, which together with the glass 46 constitute the watch case 40. 44 is a module support frame, 45
is a gasket, and the diaphragm 66' is fixed by compressing the gasket 45 provided between the module support frame 44 and the back cover 46, and a waterproof structure is also formed at the same time. 4
3a is a sound emitting hole provided in the back cover 46, and the audible sound generated by the piezoelectric electroacoustic transducer 41 is emitted from the sound emitting hole 43a.

8 and 9 are output sound pressure frequency characteristic diagrams of the piezoelectric electroacoustic transducer measured when it is assembled in the watch case 40 of FIG. 7, and FIG. 8 is the same as that shown in FIG. 1. FIG. 9 is an output sound pressure frequency characteristic diagram of the piezoelectric electroacoustic transducer 41 of FIG. 7.

Comparing Figure 8 and Figure 9, Figure 9 has more fn'h;
(ffl<, and the sharp sound pressure peak like 47.48 seen in Fig. 8 does not appear in Fig. 9). The structure of the electroacoustic transducer is... If the diaphragm is made of a polymeric 4" film: □ is used, the Young's modulus will be smaller than that of a metal plate, and the Q as a diaphragm will be lower. It has been demonstrated that since the value can be kept small, it is possible to construct a piezoelectric electroacoustic transducer with low Jo and flat output sound pressure frequency characteristics.

FIG. 10 is a plan view and a cross-sectional view of a piezoelectric electroacoustic transducer configured to further improve the output sound pressure frequency characteristics of FIG. 9, and is another example of FIG. 6 or 7. It shows.

52 is a bimorph resonator in which two pieces of piezoelectric ceramics 52a and 521 are bonded together to form a bimorph structure;
56 is a diaphragm made of a polymer material film such as aromatic polyester-based boria relay 1. The diaphragm 5 is provided with corrugations 53a and 53b by thermoforming, etc., and concentric circles are formed on the 1G moving plate 56. bimorph oscillator 5
2, a piezoelectric electroacoustic transducer 51 is constructed. Said corrugation 53a, 561]
is provided to soften the outer periphery (so-called edge) of the diaphragm, and the entire diaphragm 56 or arrow A
-A' It becomes easier to vibrate in the force direction, and the diaphragm 56 can be vibrated in a manner similar to piston motion. Therefore, the first
The output sound pressure frequency characteristic of the piezoelectric electroacoustic transducer 51 in FIG. 0 can be made more flat compared to that in FIG.

Now, as a method of driving the piezoelectric type electroacoustic transducer 31, 41, 51 configured to eliminate the conventional drawbacks as described above, there are two methods: (1) using two springs 38 as shown in FIG. .69 etc. directly to the piezoelectric electroacoustic transducer, and the spring 68.69 etc.
Inputting electrical signals from etc. (2) There are two possible methods: connecting a lead wire to a piezoelectric electroacoustic transducer using solder or the like, and inputting an electrical signal from the lead wire.

However, in the case of ■, the piezoelectric electroacoustic transducer 6
1.41.51 is always subjected to pressure (spring force), and the free vibrations of the diaphragms 66, 66' and 56 are constrained, resulting in the vibrations shown in Figures 6, 7, and 10. Even if a piezoelectric electroacoustic transducer is configured, f will increase,
The drawback is that peaks and valleys tend to appear in the output sound pressure frequency characteristics, making it impossible to make full use of these characteristics. In addition, in the case of ■, when installing into a storage container such as a watch case, the lead 1 wire must be electrically connected to the drive circuit using a conductor, etc., and the installation is difficult. 8 In order to eliminate the above-mentioned drawbacks, the present invention provides a bimorph resonator in which two piezoelectric ceramics are bonded together to form a bimorph structure, and a bimorph vibrator. A piezoelectric speaker is constituted by a diaphragm made of a polymeric material film that is bonded to the bimorph oscillator so as to cover the entire surface of one electrode surface of the element, and a frame to which the diaphragm is fixed, and By forming the electrical signal input terminal of the bimorph vibrator on the frame, a state in which the diaphragm can vibrate freely is created, and at the same time, the problem of poor incorporation of the piezoelectric electroacoustic transducer is solved. A detailed explanation will be given below based on the drawings.

FIG. 11 is a sectional view and a plan view of a piezoelectric speaker showing an embodiment of the present invention, and shows an embodiment constructed using the piezoelectric electroacoustic transducer shown in FIG. 10.

Reference numeral 55 denotes a frame made of metal such as brass, synthetic resin, etc. In this embodiment, the frame 55 is made of metal 411f'l. The outermost peripheral part 53C of the diaphragm 5B is fixed to the fixing surface 55a provided on the frame 55 with adhesive, and the fixing surface 55a is used to attach the electrode surface of the diaphragm 56 (not shown) to the frame. 5
The piezoelectric electroacoustic transducer 51 is fixed to the frame 55 so that the frame 55 becomes one of the electrical signal input terminals. Reference numeral 56 denotes an end plate that is electrically insulated from the frame 55 and fixed to the frame 55, and includes electrodes (not shown) of the piezoelectric ceramic 52a constituting the bimorph vibrator 52 and the electrodes 5 of the terminal plate 56.
6a is electrically connected to the terminal board 56Q using the frame 54, and becomes another electrical signal input terminal. An input terminal is formed, and a piezoelectric type piece 150 is formed.

Therefore, 49< of the two springs 68 and 69 shown in Figure 7
Even if a spring is brought into contact with the frame 55 and the terminal plate 56 connected to the electrical signal input terminal of the bimorph vibrator 52, no pressure is applied to the diaphragm 56, and no electricity is applied in this state. Since the piezoelectric electroacoustic transducer 51 can be driven by inputting a signal, the piezoelectric speaker 50 can fully exhibit the excellent characteristics of the piezoelectric box-air acoustic transducer 51. There is.

FIG. 12(A') and FIG. 12(I3) are a sectional view and a plan view of a piezoelectric speaker showing another embodiment of the present invention.

62 is a bimorph resonator in which two pieces of piezoelectric ceramics 62a and 621) are bonded together to form a bimorph structure;
Reference numeral 66 denotes a diaphragm made of a polymeric material film similar to that shown in FIG. A piezoelectric electro-acoustic transducer 61 is constructed by pasting . The outermost peripheral part 63C of the plate 66 is fixed with an adhesive or the like, and the electrode surface of the diaphragm 66 (not shown) and the frame 65 are electrically connected using the fixed surface 65a, and the frame 65 receives car electrical signals. The piezoelectric electroacoustic transducer 61 is connected to the frame 65 so as to serve as one of the input terminals.
is fixed to. 66 is a terminal plate fixed on the frame 65, and an electrode (not shown) of the piezoelectric ceramic 62a constituting the bimorph plate 62 and the electrode 66a of the terminal plate 66 are connected to each other using a lead wire or the like. The terminal board 66 serves as another electrical signal input terminal.

Reference numeral 67 is a telescopic member fixed at one end 67a to the frame 65-toe, such as a comb, sponge, spring, polystyrene foam, etc., and the other end 67a of the telescopic member 67 Combined with the central portion 62C of the vibrator 62, the bimorph vibrator 62
The bonded diaphragm 66 is elastically supported. The piezoelectric speaker 60 thus formed is shown in FIG. 12, and the electrical signal input terminal is formed on the frame 65 as in FIG.

Therefore, as in FIG. 11, no pressure is applied to the diaphragm 63, and no electrical signal is input to the electrical signal input terminal formed on the frame 65. can be driven.

In this embodiment, since the center portion 62C of the bimorph oscillator 62 is held by the telescopic member 67, the bimorph oscillator 62 collides with the frame 65 due to impact.
Not only does it prevent the bimorph vibrator from cracking, but the elastic member 67 acts as a damper, so the apparent Q value of the piezoelectric electroacoustic transducer 61 can be reduced, resulting in excellent shock resistance and output. It is possible to provide a piezoelectric speaker with flat sound pressure frequency characteristics.

In addition, in the embodiments shown in FIGS. 11 and 12, the frame l, 55
Metal materials were used as the material for the terminal plates 56 and 65, but synthetic resin etc. were of course used for the terminal plates 56 and 66.
Two electrical signal input terminals may be provided, or a synthetic resin frame insert-molded with a metal material may be used (and the electrical signal input terminal may be extracted from the metal material of the frame).

FIGS. 13 and 14 are cross-sectional views of the piezoelectric speaker when it is assembled into the back lid, and FIG.
The piezoelectric speaker 50 shown in the figure, and FIG. 14 do not show an embodiment in which the piezoelectric speaker 60 of FIG. 12 is incorporated, respectively.

The method of fixing the piezoelectric speaker 50 in FIG. 13 and the piezoelectric speaker 60 in FIG. 14 is almost the same.
When screwed onto the body of a watch case (not shown) using the threaded parts 59a and 64a, the gaskets 7 [1, 7
1 is compressed and fixed. A waterproof structure is formed by compressing the gasket 70.71, and it has a 1-1 degree angle. This member elastically supports the piezoelectric electroacoustic transducer 51.61, and is made of rubber, sponge, etc. as shown in the actual Mji example in FIG. It is a telescoping member similar to the telescoping section zero 7 in Fig. 14, with one end fixed to the freno, 55'', and together with 58, 67, and 68, the piezoelectric electroacoustic transducer 51.
It serves to prevent the bimorph vibrator 52, 62 from breaking due to impact caused by the bimorph vibrator 52, 62 colliding with the back cover 59, 64 or the frame 55, 65.

According to the present invention, as shown in FIG. Drives a piezoelectric electroacoustic transducer consisting of a bimorph resonator and a polymeric material film, always in an unloaded state.
I can do something. This is a highly efficient energy conversion device that takes advantage of the characteristics of a bimorph oscillator and a diaphragm made of polymer film. It is possible to provide a piezoelectric speaker with a low output sound pressure frequency characteristic and a peaceful output sound pressure frequency characteristic. Output sound pressure frequency of piezoelectric speaker of misfiring F91 w
The problem is that it is possible to have output sound pressure frequency characteristics comparable to those obtained with conventional electrodynamic speakers, and it does not generate audible sound on its own like a conventional electrodynamic speaker. Not only can it be used, but it is also easy to incorporate, so it can generate audible sound no matter where it is installed. Additionally, conventional electrodynamics.

Since it does not require a magnetic circuit like a type speaker, manufacturing costs are not only reduced, but it can also be constructed very thinly.Also, whereas conventional electrodynamic type speakers are current-driven, the present invention's Since piezoelectric speakers are driven by voltage, their energy consumption is extremely low, and if used as a replacement for conventional electrodynamic speakers, their effects will be very significant.

Furthermore, by fixing a telescoping member on the frame and elastically supporting the diaphragm to which the bimorph vibrator is bonded at the other end of the telescoping member, not only will it be resistant to impact, but the output sound pressure frequency characteristics will also be improved. This has the effect of making it more flat.

[Brief explanation of drawings]

Figures 1 (A) and (I3) are a plan view and a side view of a conventional piezoelectric electroacoustic transducer, and Figures 2 (A) and (I3) are a
Figure 3 (A) and (B) are configuration diagrams of the bimorph resonator;
Figures (A) and (I3) are a plan view and a side view of an acoustic transducer constructed by bonding a bimorph vibrator to a metal plate;
5(A) to (1)) are partial sectional views of FIG. 4 showing the operation of FIG. 4, and FIGS. 6(A), (B), and (C) are
A plan view and a sectional view of a piezoelectric electroacoustic transducer configured to eliminate the drawbacks shown in Figs.
A front view of a watch showing an example of the case where the piezoelectric electroacoustic transducer shown in the figure is incorporated into a watch case, and Fig. 8 shows the conventional piezoelectric electroacoustic transducer measured when it is incorporated into the watch case shown in Fig. The output sound pressure frequency characteristic diagram of the transducer, Fig. 9 is the output sound pressure frequency characteristic diagram of the piezoelectric type electroacoustic transducer of Fig. 7 measured when it is assembled in the watch case of Fig. 7, and Fig. 10. (
A), (B) are a plan view and a sectional view of a piezoelectric electroacoustic transducer showing other embodiments of FIGS. 6 and 7, and FIG. 11 (A),
(B) is a cross-sectional view and a plan view of a piezoelectric speaker that does not show one embodiment of the present invention, and FIGS. 12 (A) and (B) are cross-sectional views of a piezoelectric speaker that shows another embodiment of the present invention. A plan view, FIG. 13 is an assembly cross-sectional view showing an example when the piezoelectric speaker shown in FIG. 11 is assembled into the back lid, and FIG. 14 is an implementation when the piezoelectric speaker shown in FIG. 12 is assembled into the back lid. Figure 3 shows an illustrative assembly cross-section. 32.52.62...Bimorph oscillator, 66.
66', 56.66...7 from the polymeric material film. (Diaphragm, 61.41.51.61... Piezoelectric electroacoustic transducer, 55.65... Frame, 56.66... Terminal board. Patent applicant: Citizen Co., Ltd. Company (23) Figure 1 Figure 3 (A) 23 21 22bH liquid number (Hz) Circumferential liquid number (1-1z) Figure 10 (A) Figure 11 (A”) (B) Prisoner 56 Figure 12 (A) (B) Figure 13

Claims (1)

[Claims] A vibration device consisting of a bimorph resonator formed by bonding two piezoelectric ceramics together to form a bimorph structure, and a polymer material film bonded to the bimorph resonator so as to cover the entire surface of one electrode surface of the bimorph resonator. 1. A piezoelectric speaker comprising a plate and a frame to which the diaphragm is fixed, and wherein an electrical signal input terminal of the bimorph vibrator is formed on the frame.