JPS607880B2 - Composite speaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flat speaker using a piezoelectric film.

Conventionally, various types of flat speakers that drive the entire surface of the diaphragm have been proposed and implemented.

For example, Tokuko Sho 47-12432, Jitoseki Sho 52-4592
Publications No. 2, etc. describe piezoelectric speakers using polymer piezoelectric films, JP-A No. 47-13474, Jitsugyo-Sho 51-
Publication No. 100536 and the like describe a lightning-operated speaker that employs a special coil shape to achieve full-surface drive. FIG. 1 shows an example of the structure of a conventional full-plane drive speaker, in which a large number of rod-shaped magnets 2 are arranged with a vibrating membrane 1 in between. Magnets facing each other across the vibrating membrane 1 are placed so that the same poles face each other, and adjacent magnets are placed so that different poles face each other, so that a magnetic field parallel to the vibrating membrane 1 is formed. . A coil conductor 3 is provided on the vibrating membrane 1 by means such as vapor deposition so that currents perpendicular to this magnetic field alternately flow in opposite directions, and when a current is passed through the coil conductor 3, the interaction between this current and the magnetic field is The force acting between them drives the entire surface of the vibrating membrane 1 in the same direction. If an audio current is passed through this coil conductor 3, the diaphragm 1
Sound is reproduced by the vibrations of the Next, FIG. 2 shows an example of the structure of a conventional piezoelectric speaker. A pressing elastic layer 5 is formed on the substrate 4, and a polymer piezoelectric film 6 is stretched over this in a curved shape. This piezoelectric film 6
Electrode surfaces are formed on both sides by means such as vapor deposition,
When an audio signal voltage is applied between these electrodes, the film 6 expands and contracts in the direction of the arrow, and due to the pressure of the elastic layer 5 vibrates in a direction perpendicular to this, thereby reproducing sound. All of these speakers have advantages such as less distortion than conventional cone speakers because their vibrating surfaces are driven in the same phase over almost the entire surface. However, in the electrodynamic type speaker shown in Figure 1, it is difficult to obtain a sufficiently large magnetic flux density due to its structure, and in the piezoelectric type speaker shown in Figure 2, it is difficult to obtain a sufficiently large piezoelectric constant. The efficiency of both methods was low because no piezoelectric material was available. Furthermore, since these speakers use a vibrating membrane stretched under tension, they cannot produce large amplitudes, making it particularly difficult to reproduce bass sounds. For example, in the case of the Kinryu-type speaker shown in Figure 1, the diaphragm 1 is always under tension in the direction of the arrow, and as a result, a force acts to limit vibration in the direction of vibration perpendicular to this, reducing efficiency and This made large amplitude impossible. The purpose of the present invention is to provide a speaker that employs a composite structure of an electrodynamic full-drive speaker and a piezoelectric speaker, has high efficiency while taking advantage of these advantages, and is capable of reproducing sufficient bass. be.

The present invention provides a coil conductor layer that is integrated with the vibrating membrane and acts as a planar coil on at least one side of the vibrating membrane including a polymeric piezoelectric film, and further extends and/or contracts the piezoelectric film constituting the vibrating membrane. The present invention is characterized in that a means for applying an electric field to the film is provided, and a magnetic device is further provided for forming a magnetic field that vibrates the diaphragm by interaction with the current flowing through the coil conductor layer. The invention will be explained in detail below with reference to the drawings.

FIG. 3 is a sectional view showing an embodiment of a full-plane drive type speaker according to the present invention.

The vibrating membrane 7 includes a polymer piezoelectric film 8 made of a thin film such as polyvinylidene fluoride (PVDF), a full-surface electrode layer 9 formed on one side of this piezoelectric film by means such as vapor deposition or pasting, and the other side of the piezoelectric film. and a zigzag-shaped coil conductor layer 10 formed by a similar method.A perspective view of this vibrating membrane 7 is shown in FIG. 4.The vibrating membrane 7 is stretched by a frame 11. Other than the structure of the diaphragm, it has the same structure as the conventional full-plane drive electrodynamic speaker explained in FIG. It consists of a magnetic plate 14 having a large number of gates 13 that support this magnet 12 and at the same time form part of a magnetic circuit.These magnetic circuits allow the flow to flow parallel to the diaphragm 7 and through the coil conductor 10. The formation of a magnetic field orthogonal to the current is also similar to the secondary example of Fig. 1. Fig. 4 shows a perspective view of the vibrating membrane 7, as well as a method of supplying a signal voltage to the vibrating membrane.

The coil conductor 1 is supplied with a signal voltage from a low impedance signal source so that a relatively large signal current flows through the coil conductor 1. The force acting between this current and the magnetic field causes the vibrating membrane 7 to vibrate in accordance with the signal.
Furthermore, according to the present invention, a voltage obtained by full-wave rectification of the audio signal, that is, the absolute value of the audio signal voltage is applied from a high impedance signal source between the electrode layer 9 and the coil conductor layer 10. A voltage proportional to the absolute value of the signal voltage is applied between the two. At this time, the polarity of the voltage is selected so that the piezoelectric film 8 expands when the voltage is applied. In this way, when a signal voltage is applied, the piezoelectric film 8 expands in the direction of arrow A, that is, in the direction of the film surface, depending on the magnitude of the signal voltage, and the vibrating membrane 7 and film 8 vibrate in a direction perpendicular to the surface, that is, in the direction of arrow B. The tension of the film 8 is less likely to impede this process. Note that the amount of elongation of the piezoelectric film 8 can be selected to an appropriate value by selecting the voltage value. As mentioned above, the signal voltage is applied to the coil conductor 10,
To add to the electrode layer 9, for example, add the output from the audio signal amplifier to the primary terminal 16 of the transformer 15, and
Connect the next low impedance terminals 17 and 18 to the coil conductor 1.
0 terminals 21 and 22, and the outputs of the high impedance terminals 19 and 20 on the secondary side of the transformer are connected to the diodes 23 and 2.
It is sufficient to perform full-wave rectification in step 4 and add it to the electrode layer 9.

The trough properties of the diodes 23 and 24, the winding ratio of the transformer, etc. are selected so that the amount and direction of elongation of the film 8 are appropriate, as described above. Note that the low impedance terminals 17 and 18 are both taken out from a position close to the midpoint of the high impedance terminals 19 and 20, and the voltage applied to the electrode layer 9 and the coil conductor layer 10 is approximately proportional to the absolute value of the signal voltage. I'm trying to make it happen. However, strictly speaking, the potential of the coil conductor layer 10 differs depending on the position of the conductor. For example, the voltage applied to the electrode layer 9 and one end 21 of the coil conductor 10 is e, and the voltage applied to the other end 22 is e2. Then, there is a slight difference between e and e2. However, e2~e,《1e,,e
2, so this is not a big problem. Further, the influence of forward voltage drop caused by the diodes 23 and 24 is not a particular problem when compared with the magnitude of the voltage applied between the electrode layer 9 and the coil conductor layer 10. What is shown in FIG. 5 is another signal voltage supply method, which is almost the same as that shown in FIG.
The difference is that the voltage supplied to the transformer is taken from the transformer primary side 16'.

Reference numeral 25 indicates the center tap on the secondary side of the transformer, and the fourth
Parts corresponding to the figures are indicated by the same reference numerals with a dash added. Alternatively, an amplifier for passing a current through the coil conductor and an amplifier for applying a voltage between the coil conductor layer 10 and the electrode layer 9 may be separately provided without using a transformer.

FIG. 6a is a sectional view showing another embodiment of the speaker according to the present invention.

This embodiment is based on the same concept as that explained in FIGS. 3 to 5. However, while the shape of the vibrating membrane was square in the above embodiment, it is circular in this embodiment. The vibrating membrane 26 is also the piezoelectric film 2
7, a full-surface electrode layer 28 and a coil conductor layer 29. The vibrating membrane 26 is stretched by an annular frame 30, and as shown in FIG.
6, and adjacent magnets have opposite polarities. Note that these magnets are held by a magnetic disc 34 having a large number of gates 33, forming a magnetic circuit. FIG. 7a shows a sectional view of an example using the same disc-shaped vibrating membrane as in FIG. 6, and FIG. 7b shows a top view of a magnet used in this embodiment. The embodiment shown in FIG. 7 is almost the same as that shown in FIG. 6, but instead of using a plurality of concentric magnets, two disc-shaped magnets 37 and 38 magnetized in the same circle are used. They differ in the way they are used. Note that the magnets 37 and 38 are provided with a large number of exits 39 for acoustic radiation. 8 and 9 are top views of the pattern of the coil conductor layer 29 used in the embodiment of FIG. 6 or 7. FIG.

It can be seen that in both patterns, the electric particles flow concentrically, and the currents in adjacent circles are in opposite directions. In both the configurations shown in FIGS. 6 and 7 above, the magnetic field formed by the magnets 31, 32, 37, and 38 is parallel to the diaphragm 26 and perpendicular to the current flowing through the coil conductor layer 29. Similarly to the embodiment shown in FIG. 3, when a signal current flows through the coil conductor layer 29, the vibrating membrane 26 is vibrated in accordance with the signal. Therefore, the fourth
The loudspeaker according to these embodiments can be driven in the manner shown in FIG. 5, or in the manner described elsewhere. The device shown in FIG. 10 has coil conductor layers provided on both sides of a vibrating membrane, and the vibrating membrane may have a rectangular shape or a circular shape.

In this example, two piezoelectric films 41 and 42 are provided with a full-surface electrode layer 40 in between, and coil conductor layers 43 and 44 are further provided. As a driving method, the coil conductor layer 43
, 44 so that the direction of the current flowing through the coil conductors 43, 44 is the same, that is, the interaction between the current flowing through the coil conductors 43, 44 and the magnetic field generated by the magnet is in the same direction.
4 can be connected in series or in parallel. Also, in the same manner as in the above embodiments, a voltage proportional to the absolute value of the signal voltage is applied between the coil conductor layers 43, 44 and the entire surface electrode layer 40 in the direction in which the compression films 41, 42 extend. Note that the present invention is not limited to the above-mentioned embodiments; for example, the coil conductor layer, the pattern of the electrode layer, the arrangement of the magnets, etc. can be used to create a force that vibrates the piezoelectric film in response to a signal current flowing through the coil conductor. It is sufficient that a force that stretches the piezoelectric film is applied, and other suitable configurations can be used.

For example, if a magnetic field is formed that has an appropriate interaction with the current flowing through the coil conductor, the magnet may be placed on one side of the vibrating surface, or the structure of the vibrating membrane may be made of more layers. . Further, the conductor layer acting as a coil may not also be used as an electrode for applying a voltage to the piezoelectric film, but a dedicated coil conductor layer and electrode layer may be provided respectively. Furthermore, in all of the above-mentioned embodiments, the diaphragm was used in a stretched state so that the diaphragm expanded more when there was a signal than when there was no signal. It is also possible to have a structure in which vibration is promoted by. Furthermore, the shape of the vibrating membrane is not limited to circular or rectangular shapes, and may be, for example, elliptical. According to the present invention, by combining the completely different principles of electrodynamic type and piezoelectric type, the distortion of the electrodynamic type planar drive speaker can be reduced.
While maintaining its advantages such as flat frequency characteristics, it is possible to obtain a speaker that is more efficient than conventional membrane-mounted systems, has a large vibration amplitude, is relatively compact, and is capable of reproducing low frequencies.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view showing the structure of a slave full-plane drive power speaker, Fig. 2 is a cross-sectional view showing the structure of an example of a conventional piezoelectric speaker, and Fig. 3 is a cross-sectional view showing the structure of an example of a conventional piezoelectric speaker. 4 is a cross-sectional view showing the structure of an embodiment of a full-surface drive type speaker, FIG. 4 is a diagram showing a driving method of the full surface drive type speaker according to the present invention, and FIG. 5 is a diagram showing another embodiment of the driving method. , FIG. 6a is a diametrically cut perspective view of another embodiment of a full-plane drive speaker according to the present invention, FIG. 6b is a top view showing the arrangement of magnets used in this embodiment, and FIG. A perspective view showing the configuration of yet another embodiment of the present invention cut in the diametrical direction, b is a top view of the magnet used in this embodiment, and FIGS. 8 and 9 are the same as those in FIGS. 6 and 7. A top view showing a coil conductive layer pattern of a vibrating membrane used in an example,
FIG. 10 is a sectional view showing the structure of a vibrating membrane used in yet another embodiment of the present invention. 1, 7, 26... Vibration membrane, 2, 12, 31, 3
2... Magnet, 3, 10, 29, 43, 44. ．．
・．． ．．・Coil conductive layer, 8, 27...Piezoelectric film, 9, 28, 40...Full surface electrode layer, 11,
30. ．．・．． ．．・Frame, 13, 33, 39...
Open □, 14, 34. ．． ．． ．． ．． ．． Magnetic plate, 15, i5'...
...Transformer, 23, 23', 24, 24'...Diode. Figure 1 Figure 2 Figure 3. Figure 14 Figure 5 Figure 10 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Scope of Claims] 1. A coil conductor layer is provided on at least one side of a vibrating membrane including a polymeric piezoelectric film and is integrated with the vibrating membrane and acts as a planar coil, and furthermore, the piezoelectric film constituting the vibrating membrane is stretched and/or Alternatively, a means for applying an electric field to the film so as to cause it to contract is provided, and a magnetic device is further provided for forming a magnetic field that causes the vibrating membrane to vibrate through interaction with the current passed through the coil conductor layer. A composite piezoelectric and electrodynamic speaker. 2 A vibrating membrane formed by providing a coil conductor layer that acts as a planar coil and also an electrode layer on one side of a polymeric piezoelectric film, and a full-scale electrode layer on the other side, and connecting the same polarity with each other with this vibrating membrane in between. A magnetic device of bar-shaped magnets arranged so that opposite polarities are arranged to form a nearly parallel magnetic field to the vibrating membrane, and the coil conductor layer has parallel portions through which currents in opposite directions alternately flow. 2. A composite speaker according to claim 1, characterized in that: 3 A vibrating membrane formed by providing a coil conductor layer that acts as a planar coil and also an electrode layer on one side of a polymer piezoelectric film, and a full-scale electrode layer on the other side, and connecting the same polarity with each other with this vibrating membrane in between. A plurality of annular magnets arranged concentrically so that they face each other and alternately have opposite polarities, or magnets with the same polarity facing each other across a vibrating membrane and magnetized concentrically and alternately with opposite polarities. A magnetic device consisting of two disk-shaped magnets forms a magnetic field substantially parallel to the diaphragm, and the coil conductor layers are concentric coil conductor layers configured so that currents in opposite directions alternately flow through the coil conductor layers. A composite speaker according to claim 1, characterized in that: 4 A vibrating membrane formed by providing a coil conductor layer that acts as a planar coil and also an electrode layer on one side of a polymer piezoelectric film, and a full-scale electrode layer on the other side, and a magnetic field that is almost parallel to this vibrating membrane. A magnetic device is provided, in which an audio current from a low-impedance signal source is passed through the coil conductor to operate as a full-surface drive type electrodynamic speaker, and an absolute value of the audio signal is provided between the coil conductor and the full-surface electrode layer. 1. A composite system speaker characterized in that a full-wave rectified audio signal is added so that the diaphragm expands and contracts in response to the vibration.