Patent Translate Powered by EPO and Google Notice This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate, complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or financial decisions, should not be based on machine-translation output. DESCRIPTION JPS56106498 Description of Invention Electret electrostatic speaker DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electret electrostatic speaker comprising a diaphragm and a pair of fixed electrodes sandwiching the diaphragm from the front and back. Heretofore, electret electrostatic loudspeakers have been well known, in which a flat diaphragm is driven by a fixed flat plate electrode from the front to the rear and between pores. An example of the operation principle is shown in FIG. The film 1 of monoball electret, which holds a single charge (in this example, a negative charge) semipermanently, is used as a vibrating film, and the fixed electrodes 2 and 3 are disposed before and after that. The fixed electrode and the vibrating film form a capacitor, and a positive charge is induced on the surface of the fixed electrode. A signal voltage whose phase is inverted is applied to the front and rear electrodes 2 and 3 to push-pull drive the vibrating membrane 1 by electrostatic force. The acoustic vibration generated by the vibrating membrane is radiated back and forth through the pores of the wedge / fixed electrode. In another conventional example, as shown in FIG. 2, the film 5 coated with the conductive coating 4 is used as a vibrating film, and the polarization is semipermanently held on the metal electrode 6.7 before and after. In the case of the conventional Electric EndPage: 1 treads 8 and 9, in this example, the fixed electrodes are disposed with the negative charge side facing the vibrating membrane. The vibrating membrane and the fixed electrode form a capacitor as in the previous example, and a positive charge is induced on the surface of the vibrating membrane by the voltage of the electret. The diaphragm is push-pull driven by the phase-inverted input voltage. Acoustic vibrations are also emitted back and forth through the pores which are drilled in the stationary electrode. However, in the case of the conventional electrostatic speaker, it is necessary to increase the amplitude between the fixed 04-05-2019 1 electrode and the vibrating film in order to reproduce the low-pitched range, so that the gap between the fixed electrode and the diaphragm must be increased. It has the disadvantage of having to give up reproduction in the low range or having to take a very large area of the vibrating film because it becomes very bad. The present invention has the above-mentioned conventional drawbacks by applying to the electret electrostatic type speaker the same pronunciation tit = as used in the electrodynamic speaker known as a so-called bail driver. It is an object of the present invention to provide a compact speaker which enables wide-band, highefficiency reproduction with an apparent vibrating membrane area. Hereinafter, the configuration of the present invention will be described with reference to one embodiment. FIG. 3 is a cross-sectional view of an embodiment of the present invention. The vibrating membrane 10 is formed by bending a monoball electret polymer film into an accordion pleat shape and is fixed by a support frame 11 at both ends. The fixed electrode group 12.13 is fixed by the support plate 14 from above and below in a form in which it is inserted into the folds of the vibrating film from the front and back respectively. (The top support plate is not shown in this cross section. The fixed electrode group 12 in front of the vibrating membrane is all electrically connected, and the rear fixed electrode group 13 is similarly wired. The upper and lower sides of the vibrating membrane 10 are adhered to the support plate 14, and the spaces in front of and behind the vibrating membrane are completely separated by the vibrating membrane, and there is no air leakage. The principle of operation of this embodiment is shown in FIG. The vibrating membrane and the fixed electrode groups 12 'and 13 form a capacitor. Here, when the vibrating film is negatively electretized, positive charges are induced on the electrodes. If there is no signal voltage, the vibrating membrane is in an equilibrium position centered between the electrodes, as shown in FIG. 4 (α). When a signal voltage is applied such that the front electrode group 12 is negative and the rear electrode group 13 is positive, the vibrating membrane is pushed by the electrode group 12 by the electrostatic force and pulled by the electrode group 13. 4 As shown in FIG. As a result, the forwardly open folds open above the equilibrium position and draw air as shown by the arrows in the figure, while the rearward open folds close from the equilibrium position and release air. When the phase of the signal input is reversed and the electrode group 12 is positive and the electrode group 13 is negative, the driving force is also reverse, the diaphragm is deformed as shown in FIG. 4 (c), and the air is released forward. Suction air from behind. When an alternating current input is applied, the above-described motion is repeated to emit sound waves whose phases are reversed forward and backward. Although the embodiment in which the vibrating membrane is constituted by a monopole electret has been described above, the vibrating membrane may be drawn by a film coated with a conductive coating, and a normal electret may be attached to a fixed electrode. Due to the bias voltage by the electret, charge is induced on the surface of the vibrating film, and push-pull driving is performed by the signal voltage applied to the fixed electrode. There is almost no change except for the change of the material of the diaphragm and the fixed electrode, and the speaker can be realized with the same configuration as shown in FIG. 04-05-2019 2 In the electret electrostatic speaker according to the present invention, since the vibrating membrane folded in accordion pleats is used as a sound source, the apparent size is the same in size, and the electret electrostatic type having a wider area than the conventional one is used. There is an advantage that a wide frequency band and high efficiency comparable to a speaker can be obtained. Since the fixed electrode is not disposed at the position where the front surface of the vibrating membrane is closed, it is not necessary to open the pore, and the manufacture is easy. Also, compared with the electrodynamic speaker known as a so-called bail driver, the expensive magnetic circuit for providing a uniform bias magnetic field, which is necessary for the electrodynamic speaker, is not required, and cost, volume and weight You can save a lot. Furthermore, it is necessary to print a complicated electrode pattern on the vibrating membrane surface in the case of End Page: 2 lever, but in the present invention, it is only necessary to electretize and form a polymer film, and more. Does not require a multi-period manufacturing process. Therefore, the formation of the vibrating film becomes very easy, and the improvement of the yield and the cost reduction can be expected. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 do not show the operation principle of the conventional electret electrostatic loudspeaker, FIG. 3 is a cross sectional view showing one embodiment of the electret electrostatic loudspeaker according to the present invention, FIG. FIG. 4 shows the operation principle of the embodiment. Reference Signs List 1 monopole electret vibrating membrane 2 front fixed electrode 3 rear fixed electrode 4 conductive coating layer 8.9 electret 10 monoball electret vibrating membrane 12 Front fixed electrode group 13 ··· Rear fixed electrode group or more EndPage: 3 04-05-2019 3
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