Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3894199 A
Publication typeGrant
Publication dateJul 8, 1975
Filing dateNov 18, 1970
Priority dateNov 19, 1969
Also published asCA949674A1, DE2055683A1, DE2055683B2
Publication numberUS 3894199 A, US 3894199A, US-A-3894199, US3894199 A, US3894199A
InventorsAsahina Mitsuo, Iwama Kiyonori, Tamura Masahiko
Original AssigneePioneer Electronic Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electret electrostatic electroacoustic transducer
US 3894199 A
Abstract
An electrostatic electroacoustic push-pull type transducer wherein a vibrating film is not connected to any signal terminal. One terminal of a step-up transformer is connected to one fixed electrode, and the other terminal of the transformer is connected to another fixed electrode.
Images(1)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent [191 Tamura et al.

[ July 8,1975

[ ELECTRET ELECTROSTATIC ELECTROACOUSTIC TRANSDUCER [75] Inventors: Masahiko Tamura; Kiyonori Iwama,

both of Tokorozawa; Mitsuo Asahina, Tokyo, all of Japan [73] Assignee: Pioneer Electronic Corporation, Tokyo, Japan [22] Filed: Nov. 18, 1970 211 Appl. No.: 90,771

[30] Foreign Application Priority Data Nov. 19, 1969 Japan 44-92079 [52] US. Cl 179/111 E [51] Int. Cl H041 19/00 [58] Field of Search 179/111 R, 111 E [56] References Cited UNITED STATES PATENTS 3,118,022 1/1964 Sessler 179/111 E 3,474,197 10/1969 Koukal 179/111 E 3,646,280 2/1972 Tamura 179/111 E FOREIGN PATENTS OR APPLICATIONS 494,221 6/1926 Germany 179/111 E 1,147,423 4/1969 United Kingdom 179/111 E Primary Examinerl(athleen H. Claffy Assistant ExaminerGeorge G. Stellar Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT An electrostatic electroacoustic push-pull type transducer wherein a vibrating film is not connected to any signal terminal. One terminal of a step-up transformer is connected to one fixed electrode, and the other terminal of the transformer is connected to another fixed electrode.

4 Claims, 2 Drawing Figures ELECTRET ELECTROSTATIC ELECTROACOUSTIC TRANSDUCER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to an electrostatic electroacoustic transducer, and more particularly to a novel and improved push-pull type transducer using an electret.

2. Description of the Prior Art Prior art push-pull electrostatic electroacoustic transducers, such as a speaker, generally comprise a vibrating film, two electrodes and a holding member which holds the vibrating film between the two electrodes. A polarization voltage is applied to the film and a potential is applied across the electrodes through a step-up transformer.

The prior art devices have many disadvantages. First, the polarization voltage E is large and therefore a larger conductor for the polarizing voltage is required. Second, the step-up transformer must be provided with a center tap to boost and divide an input signal and to place opposing potentials on the fixed electrodes. Third, a vibrating film must be connected to the center tap of the step-up transformer.

SUMMARY OF THE INVENTION It is therefore the primary object of this invention to provide a novel and improved electrostatic electroacoustic transducer in which above mentioned defects are overcome.

It is a further object of this invention to provide an electrostatic electroacoustic transducer, using an electret, which is simple in construction and inexpensive to produce.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional plan view of a prior art push-pull electrostatic electroacoustic transducer showing its principle.

FIG. 2 is a sectional plan view of a push-pull electrostatic electroacoustic transducer of the preferred embodiment of the present invention.

Prior art push-pull type electrostatic electroacoustic transducers are constructed as shown in FIG. 1. A holdv ing member 11, made of an insulating material, holds two fixed electrodes 12. A vibrating film 13 is positioned between the electrodes. Fixed electrodes 12 have many holes which pass the acoustic radiation. A polarization voltage E0 is applied across the vibrating film l3 and each fixed electrode through a step-up transformer 14 and a resistor R0. The primary winding of the step-up transformer 14 is connected to a signal source 15. The potential of both fixed electrodes is supplied by an alternating signal of the signal source 15. The potential of the two fixed electrodes is opposing. That is, when one is positive, the other is negative.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 2, fixed electrodes 21 and 22 face each other. They comprise back electrodes 211 and 221, and electrets 212 and 222 which are affixed to the back electrodes. The fixed electrodes 21 and 22 have many holes which pass acoustic radiation. The potential of the facing surfaces of the two electrets is same. A vibrating film 23 is positioned between the fixedelectrodes 21 and 22. The vibrating film 23 is electroconductive at least at its surface. Holding member 24 is made of an insulated material, and holds the fixed electrodes 21 and 22 and the vibrating film 23. One terminal of the secondary winding of step-up transformer 25 is connected to the fixed electrode 21, and the other terminal is connected to the fixed electrode 22. A signal source 26 is connected to the primary winding of step-up transformer 25.

In operation, when facing surfaces of electrets 212 and 222 are positive, both surfaces of the vibrating film 23 are negative. The vibrating film 23 assumes a negative charge because it has an electroconductive surface and is positioned between the two positively charged electrets. When an alternating signal from signal source 26 is stepped-up by transformer 25 and applied to the fixed electrodes 21 and 22, the positive potential of one electret, for example electret 212, is increased and that of the other electret is decreased during a half cycle of the signal. Thereby, the vibrating film 23 is biased toward the electret 212. Then during next half cycle of the signal, the vibrating film 23 is biased toward the other electret 222. This process is cyclicly repeated, vibrating film 23. As can be seen, the vibrating film 23 is not connected electrically to the electrets.

The present invention, as described hereinabove, gives many improvements over prior art devices. First, the vibrating film is not connected electrically, therefore the construction becomes simple and poor connections will not occur. Second, a polarization source and the center tap of the step-up transformer is unnecessary, therefore the transducer may be small in size, light in weight and inexpensive to produce.

While the invention has been particularly shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

We' claim:

1. An electrostatic electroacoustic transducer comprising first and second electrets positioned to face each other, said electrets having identical potentials on their-facing surfaces, first and second back electrodes affixed to said first and second electrets, a vibrating film positioned between said electrets, said film being electroconductive on its surface, and a signal source wherein one terminal of said source is connected to said first back electrode and the other terminal is connected to said second back electrode.

2. An electrostatic electroacoustic transducer is set forth in claim 1, further comprising a holding means for holding said electrets, said back electrodes and said vibrating film.

3. An electrostatic electroacoustic transducer comprising first and second electrets positioned to face each other, said electrets being identically charged on facing surfaces, first and second back electrodes affixed to said first and second electrets, a vibrating film positioned between said electrets, said film being electroconductive on its surface, a step-up transformer having a primary and secondary winding wherein one terminal of the secondary winding is connected to said first back electrode and the other terminal of said secondary Winding is connected to said second back electrode, and a signal source connected to said primary winding of said step-up transformer.

4. An electrostatic electroacoustic transducer as set forth in claim 3, further comprising a holding means for holding said electrets, said back electrodes and said vibrating film.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3118022 *May 22, 1962Jan 14, 1964Bell Telephone Labor IncElectroacoustic transducer
US3474197 *Oct 13, 1965Oct 21, 1969Tesla NpElectret microphone
US3646280 *Aug 26, 1970Feb 29, 1972Pioneer Electronic CorpBackplate for electret loudspeaker
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3942029 *Jul 17, 1974Mar 2, 1976Sony CorporationElectrostatic transducer
US5097515 *Oct 30, 1989Mar 17, 1992Matsushita Electric Industrial Co., Ltd.Electret condenser microphone
US7376239 *Oct 9, 2003May 20, 2008Panphonics OyElectromechanical transducer and method for transforming energies
US7542579 *Sep 15, 2005Jun 2, 2009Seiko Epson CorporationUltrasonic transducer, ultrasonic speaker, acoustic system, and control method of ultrasonic transducer
US7668323 *Sep 21, 2005Feb 23, 2010Seiko Epson CorporationElectrostatic ultrasonic transducer and ultrasonic speaker
US7949143 *Apr 23, 2009May 24, 2011Seiko Epson CorporationUltrasonic transducer, ultrasonic speaker, acoustic system, and control method of ultrasonic transducer
US8107651Aug 7, 2008Jan 31, 2012Industrial Technology Research InstituteSpeaker structure
US8126189May 27, 2009Feb 28, 2012Industrial Technology Research InstituteMulti-directional flat speaker device
US8139794Feb 13, 2009Mar 20, 2012Industrial Technology Research InstituteSpeaker devices
US8155356Jul 18, 2008Apr 10, 2012Industrial Technology Research InstituteStructure and manufacturing method of electrostatic speaker
US8184833 *Dec 14, 2007May 22, 2012Sony Ericsson Mobile Communications AbElectrostatic speaker arrangement for a mobile device
US8196282 *Feb 13, 2009Jun 12, 2012Industrial Technology Research InstituteMethods of making speakers
US8243966Aug 4, 2009Aug 14, 2012Industrial Technology Research InstituteAssembly structure of a flat speaker
US8322018Mar 5, 2010Dec 4, 2012Industrial Technology Research InstituteMethod of manufacturing speaker
US8385586Apr 14, 2010Feb 26, 2013Industrial Technology Research InstituteFlat loudspeaker structure
US8391520Aug 13, 2009Mar 5, 2013Industrial Technology Research InstituteFlat speaker unit and speaker device therewith
US8559660Jul 12, 2007Oct 15, 2013Industrial Technology Research InstituteElectrostatic electroacoustic transducers
US8588438 *Dec 30, 2010Nov 19, 2013Industrial Technology Research InstituteDriving interface device adaptive to a flat speaker
US8594349Dec 30, 2009Nov 26, 2013Industrial Technology Research InstituteFlat speaker structure
US8625824Dec 28, 2010Jan 7, 2014Industrial Technology Research InstituteFlat speaker unit and speaker device therewith
US20100024198 *Feb 13, 2009Feb 4, 2010Industrial Technology Research InstituteMethods of making speakers
US20120002826 *Aug 19, 2010Jan 5, 2012Tsung-Hung WuElectret electroacoustic transducer
US20120106761 *Dec 30, 2010May 3, 2012Industrial Technology Research InstituteDriving interface device adaptive to a flat speaker
CN1750716BSep 16, 2005Dec 21, 2011精工爱普生株式会社超声波扬声器、声学系统以及超声波换能器的控制方法
EP0008237A1 *Aug 10, 1979Feb 20, 1980Shigeo OkuboA sensor for generating electrical signals representative of relative motion
EP1718107A2 *Apr 25, 2006Nov 2, 2006Panphonics OyElectrostatic transducer, method for connecting the same and manufacturing method
WO2014100012A1 *Dec 17, 2013Jun 26, 2014The Regents Of The University Of CaliforniaElectrostatic graphene speaker
Classifications
U.S. Classification381/116, 381/191
International ClassificationH04R19/00, H04R19/01
Cooperative ClassificationH04R19/013
European ClassificationH04R19/01B