DE2345285A1 - ELECTROMECHANICAL CONVERTER AND METHOD FOR MANUFACTURING IT - Google Patents

Description

PATENT AGENCY OFFICE TlEDTKE - BüHLING - KlNNE 2345285

TEL. (0811) 539653-56 TELEX: 524845 tlpat CABLE ADDRESS: Germaniapatent Munich

8000 Munich 2 Bavariarlng 4

P.O. Box 202403 ⁷ September 1973 B 5587

Uniroyal Ltd. Montreal (Canada)

Wan »Her and Vnrfnliron to his Tlerstrillun.Tr

The inventor; concerns a plclrtromcchariischon I / ^ ndlcr and a Vnri '-' Uiren for its production. In particular, the power supply refers to an electro-mechanical converter. is suitable your fin poinrisiertns dielelcfcrisebns material such as Ex iolswfiise fin electret Λην / ending is, in a structure <\ vr for push-pull operation without an external DC bias is required.

409812 / 09A6 ORIGINAL BATHROOM

One prior art transducer is constructed using a diaphragm which comprises a number of layers of thin electrolyte interi.nl and a number of 1 ext capable layers, which are arranged between two electrodes for push-pull operation. The dynamic mass of this membrane is usually higher than that of an electrostatic transducer of the same or similar type, in which no electrical relays are used, but in which an external direct current bias is used. The higher dynamic mass of the electret membrane adversely affects the fidelity of reproduction and the conversion sensitivity of the transducer. In addition, to achieve good fidelity, the air gap between the diaphragm and the stationary part (] cr, transducer should be of the order of about 0.254 mm. In the context of the present invention, it has been mathematically determined that the vibratory force on the diaphragm is a maximum is when dio thickness of the electret is greater than dc.v Luftspaltzwischenrnum, ie, when the thickness of the electret · :; equal to the dielectric constant of the electret ';... is multiplied by dom Luftspaltzvrisclicnrnum as a result, the maximum Vibrntionskraft to the above described previous electrification tubes could practically not be realized because the electrons would become too thick for a vibration or for the execution of oscillations.

409812/0946

BATH ORIGINAL

Due to the relatively thick construction of the 151 eic tr et s one Transducer constructed in accordance with the present invention Imimii di.e equi va 1. entc direct current bias at least one Be kilovolts. That is higher than the bias of conventional ones electrostatic earphones, which is typically around 200 volts. Accordingly, with converters in In accordance with the invention, without the risk of high spawning an external bias as required for conventional electrostatic earphones high sensitivity, quality and stability can be achieved.

According to the invention, an electromechanical transducer comprises a pair of electrophotatically polarized dielectric stator devices by.w. Stators each of which includes a conductive member and openings extending through the stator assembly or stator, respectively. The transducer also includes ^ ine thin Schwingungsniembranvorrichtung or Schwinguiigsmembran which r comprises a layer rx \ · .1 eitfi'higem material; also means for holding the r-iomhr.-m device between the stator device at a distance YM from the latter; and a device for individually electrically connecting the conductive part of the stator device and the conductive layer of the monibranch device.

The invention also includes a method of manufacture according to the present invention of an electromechanical transducer Hon assembling a

409812/0946 bad or _{! Ö1} .na _L

Pair of dielectric stator devices and dielectric Stators at a distance from each other, whereby each stator device or each stator has a conductive part and sieve through openings through each stator device or each stator extend, and a thin Schwingungsmoinbrnnvorrichtung or « Vibrating membrane comprising a layer of conductive material, between the fixed stator device or the assembled cn Stators by applying a high potential difference between the conductive © part of every stator device or each Stator and the conductive layer of the membrane device or Membrane.

Furthermore, an electro-technical converter according to the invention comprises an electrostatically polarized stator device or electrostatically polarized stators, which have a conductive part and have a dielectric constant. The transducer also has a thin vibrating diaphragm device which comprises a layer of leitfähigeiii material, and means for holding the membrane device at a distance from the Statorvorricbtung _t the thickness of the dielectric stator except the conductive member is approximately equal to the product of the Dielektrizitätkons Tanton ! .in] is fixed with the distance between the membrane device and the stator device; and furthermore a device for the individual electrical connection of the conductive part of the stator device and the conductive layer of the membrane device is provided.

409812/0946

BATH

ti.it is the "stator before direction" or the term "stator" fiino means that are stationary within the transducer is to the extent that mechanical vibrations, for example, sound reproducing or sound-related oscillations within the converter are affected.

The transducer has a low weight, for example 2 ".6 gi and a small thickness, for example 5 minutes.

The invention is explained in more detail below with reference to schematic drawings of performance examples.

Fig. 1 shows a partially schematic plan view a converter suitable for use in an earphone and constructed in accordance with the invention is ;

Fig. 2 shows pine fragmentary, partially scbeniatische Sectional view of the transducer of FIG. 1 along line 2-2 of FIG. 1, the transducer is drawn on an enlarged scale compared to Figure 1;

FIG. 3 shows a partially schematic plan view of a stator of the converter of FIG. 1;

409812/0946

h shows a partially schematic perspective sieve for the diaphragms and mounting brackets of the transducer in FIG. 1 5

Fig. 5 zeirjI. a fragmentary, partially schematic sectional view of the membrane of FIG. 4 along the line 5-5 of FIG. k and enlarged in relation to the latter figure! MnHstab;

Fin ;. Fig. 6 shows a plan view of a frame related to this is used to keep the membranes of Fig. '* at a distance from one another;

7 shows a partial sectional view of the transducer 1 on an enlarged scale compared to the latter figure, namely along the line 7-7 of FIG. 1, wherein nine device for electrically connecting the conductive layers of the Meiiibran device you can see i and

Fig. ?) Shows a partially schematic diagram of two earphone transducers constructed in accordance with the invention, as well as electrical circuits connected to the transducers and suitable for coupling to sources of electrical audio signals representing stereophonic sound .

409812/0946

1 and 2 of the drawing, in which an electromechanical transducer according to the invention is shown, which is suitable for use as earphones, for example headphones, telephones or the like is. The transducer can be housed in a conventional earphone case (not shown) and attached to it by any suitable means, such as contact cement.

The transducer comprises a pair of polarized dielectric stators 10, 11, a conductive layer being provided on each stator and each stator having openings 10a, 11a through it or a dielectric stator preferably comprises a polarized sheet-like electret material such as a thin sheet of electret material such as a thin sheet of a material available from the General Electric Company under the handpis designation "Lexan" which is believed to be a polycarbonate of the following composition: Poly ; 2,2-bis ( ¹ l -hydroxyphenyl) propane carbonate. VJcdo thin plate 10, 11 made of polycarbonate can have a thickness of, for example, 1.27 mm, preferably a thickness in the range of 0.025 ^ 1 mm to 12.7 mm A flat material of this type, for example in the form of a thin plate and 1.27 "" thick, has the mechanical strength, stability and rigidity that f is suitable for the electric electrode.

0 9 8 12/0946 BAD ORIGINAL

The thickness of the conductive layer 10b, 11b on each electret can be, for example, 0.25 ** mm. A layer of electrically insulating material 12, 13, for example a coating approximately 0.0127 mm thick, can be applied to the conductive layers 10b, lib. In some constructions, a thin film of wire can be laminated to a stiffer material, such as a perforated metal plate, to provide a rod of the desired mechanical strength and rigidity.

To form each stator 10, 11, a thin polycarbonate plate can be provided with a suitable conductive coating, for example by spraying, painting or screen printing, for example with an adhering coating provided with silver. The coated thin plate can be cut into any desired shape and perforated in the desired pattern, for example one is indicated schematically in FIG conductive epoxy can be glued to a projection 10c of the silver imistor, which surrounds an opening in the stator, so that κιητι a suitable conductive connection between the silver coating and a connection, which is electrically connected in a manner described in more detail below If the conductive oxide has completely set or hardened, the stator can be cleaned in a suitable manner.Another opening 16 in the non-veraiJborton area of the stator

409812/0946

BATH ORIGINAL

is intended for an "in" device which serves to establish an electrical connection with the silver coating of the other stator 11, as will be explained in more detail below the pattern lib · ο arranged such that its projection lic extending in the opposite direction to the projection 1NC, as indicated by the illustrated using a broken line in F £ g _D IL construction.

··

For example, the stator 10 has 90 openings per 6.45 ent

of I.587 Mn diameter in a pattern as it schematize !! is shown in FIG. 3 Here is to. Note that, for example, there are no openings in the central area, which has a size of 12.7 »by χ 12.7 mn, and that there are no openings in the rim area, which has a width of 3.175 mm of the silver pattern, so that the desired electromechanical Umwan 'treatment effectiveness and low distortion sound transmission in a frequency range of, for example, 50 Hz to 10 kHz. The dimensions of the silver area · of the stator can now be, for example, 76 · 2 him χ ΠΠ.9 and have the shape of an ellipse, for example. The opening dimension, the number of openings and their positions can be changed, uin a change in sensitivity, performance, quality or the like

and the fidelity as desired

409812/0946

- JO -

aim the openings are preferably evenly distributed, as shown, and not in a single area. or -rushed.

With a suitable coupling circuit between an electrical Signal generator and earphones made according to the invention are constructed, the earphones can have 90 openings 2

6 "% 5 cm and a diameter of 1.5 ^ 7" en produce an output of over 100 decibels (relative to 0.0002 dyn / cw **) with a flat frequency response, ie plus or minus 3 Decibels, and »was over a frequency range from 50 Hz to IC kHz. Preliminary investigations have shown that for openings of 1 "5" 7 HOT .Durclunesser approximately 50 openings per 6.5 cm "result in a maximum sound transmission with a" flat frequency curve, ie "with a frequency curve of plus-5 or minus 3 decibels over a frequency range from 50 Hz to .12

The stator or stator can be polarized or charged, for example by negative ion injection from an electrode at, for example, a negative voltage of 2G-10 kV via an air gap to the polycarbonate side of the stator, while the silver side of the stator is connected to ground. The charging period can be, for example, half a minute to 20 minutes. The stators are preferably charged at the same time after they have become a complete changeover

409812/0946

- Il -

preferred method of manufacturing the transducer that further will be described in more detail below.

Reference is now again made to FIGS. 1 and 2, after which the transducer also has a vibrating membrane device having a layer of conductive material 17a and 17b and a device for holding the membrane device between the stators at a distance from the latter.

Reference is now made to FIGS. 1 and 5 in greater detail taken, after which the membrane device, for example, two stretched Polyäthylentercphthalatfilnte or -folien iSa and lOb, which under the trade name "Mylar" are available. The means for holding the membrane device includes, for example, cardboard frames 19, 20 and 21, which are glued in the required position in the transducer are connected·

On at least one Mylar sheet of the membrane is a conductive one Layer formed, for example by vacuum lengthening an aluminum layer. Preferably both are. Foils are conductively coated, as this results in a better electronic and mechanical balance in push-pull modes can be achieved. The films are preferably arranged so that their insulating side the respective Facing stators while their conductive The layers 17a and 17b face each other. Each of the

409812/0946

Mylar sheets can have a thickness of, for example, 0.0127 mm, and each of the conductive layers on the films can be several thousand angstroms thick. The cardboard spacer 20 preferably has a conductive metallized surface and a thickness of e.g. 0.254 mm, and this cardboard spacer is inserted between the conductive surfaces 17a and 17b of the membrane sheets so that the latter are kept at the same electrical potential and prevented from being at high frequency to one another to rub or scrub. The girdles 19 and 21 can each have a thickness of, for example, 0.381 mm, so that an air gap of zD Ο.3ΠΙ mm thickness or width results between each membrane and the corresponding stator. The dielectric constant of the polycarbonate core in the form of a thin sheet is 3.O2. As a result, the thickness of the electret material present as a thin plate of each stator 10, 11 is preferably greater than the thickness of the air gap, and it is preferably approximately equal to the product of the dielectric constant, the thin, plate-shaped electret material multiplied by the thickness of the air gap, so that one receives a maximum vibratory force on the diaphragm in response to an applied AC voltage signal. In order to achieve this, the thickness of the thin, plate-shaped electret matorial of each stator 10, 11 _t with the exception of the conductive layer on it, preferably un-

409812/0946

danger 1.1 ¹ 13 mm.

From a publication by Recdyk and I'orlmnn with the Title "The Measurement of Surface Charge" found in "Eloctrets and Related Electrostatic Charge Storage Phenomena ", Electrochemical Society, Inc. (19i» ß) has been published, .makes it possible that the strength of the electrical direct current fold E_ between the electret stator part and the conductive layer of the membrane by the following equation is represented:

(D

where · 'is the surface charge density, i.e. the thickness of the electric red, d the thickness of the air gap between the electret stator part and the conductive layer of the membrane, K the dielectric constant of the electret and f the dielectric constant or the dielectric conductivity of the air bodouton.

On the basis of the above-mentioned publication it can be shown that the capacitance C between the electret. ··, · tatorte.il and the Membrane can be expressed in the following way:

409 .12 / 0946

^d 2 ^{+ d} l

(2)

where a is the Oberfla'chenbereich of Elektretstfitorteils, the old cooperates membrane.

Then the surface charge Q, which is due to the membrane of the alternating signal between the lilektretstorteil and the membrane is induced, can be expressed by

Q = CV (3)

where V is the V / current voltage signal applied between the stator electrode and the diaphragm.

According to Coulomb's law, the vibration force F on the membrane is proportional to the product of the strength E _{2 of} the direct voltage field and the surface charge; Which has been induced on the membrane due to the Wec'isolstromsignals Q, and this vibrating force can been expressed in folgonder l / ation:

F = QE Ci)

F = CVE ₂ (5)

409812/0946

- 1

Substitute equations (1) and (2) into the equation (5) i then mrm obtains the following equation:

F = -V « a

^d 2 ^{+ d} l

-U ₁ + K d

(5a)

Differentiating equation (5a) with respect to K gives that the Vibrationslcraft F reaches a maximum when the relationship is:

= K

(6)

In the production of the McNibran assembly, stretched metallized film 17 "" *, 1 · ^η · η can be attached by means of clamps η η to a cardboard wire, such as the frame 19, which is shown in FIG. 5, for example by means of contact cement or similar to the frame 1 <ϊ, and a stretched metallized film 17b, 1 "> b can be on this! Frame in the same bwf. similar wines can be attached. A cardboard spacer 20, as shown, for example, in FIG

409812/0948

- Lr, -

Sheets are placed and the components of the membrane assembly can be glued together with contact cement, with a conductive contact between the areas of the metallized spacer 2O and the conductive Surfaces 17a, 17b of the I-Iombran foil are maintained will. .

After the cement has solidified, the membrane structure can be placed in a preheated oven at a temperature of, for example, 95 C for a period of about 2 minutes, until the mylar film undergoes heat shrinkage and this results in a suitable baking stress. As FIG. 6 shows, the metallized spacer has a slot 20a of, for example, 1.P.7 now UniLo, which makes it possible for the gas pressure to stabilize in the membrane structure of FIG.

The membrane structure can then be glued to the stators 10, are attached, which are shown in Figs. 1 and 2, preferably such that the openings of both stators align with each other so that a higher acoustic permeability results. Reference is now also made to FIG. 7, in which a partial sectional view of the one shown in FIG Converter on a larger scale than this figure iiit, along the line 7-7 of the Fip. 1. One Opening .1Od in the stator 10 and similar «! or similar openings

409812/0946

19d and 21d, which run through the cardboard frames 19 and 21, form openings for electrical connection devices, with which the central metallized spacer 30 and the 1 conductive layers 17 "" "17b of the membrane device electrical are connected, these electrical connection devices, for example, a suitable connection or a loitfi'higc Lötfahno 33 <"" include the or those in conductive Contact with the spacer 20 is maintained by means of a screw 31a, which siel) through a conductive Washer 32a, the spacer 20 and the other cardboard frame 21 extends and which by means of a suitable washer Vl and a nut 3 '* a is fastened.

Reference is now made in greater detail to FIG. 2 of the drawing, in which a device 7 for electrically connecting the stator surface IQa is shown in a partial sectional view of the transducer according to FIG. 1 on an enlarged scale compared to FIG. For example, a screw 25 extends through a spring ring 26 and a conductive Lütfahne 27 as well as through the conductive ring Ik and a silver projection 10c of the surface 10a, further through an insulating compressible sealing or a compressible insulating tube 2fl, for example made of rubber, and through a spring washer 29 and a nut 3 ° on the other side of the transducer. In this way, an electrical connection between the Lülfahnc 27 and the silver coating 10b is screened.

409812/0946

BATH

23-5285

A substantially identical or similar connection can be made with the silver coating 11b of the other stator, which also extends int. Noisplelsweise in FIG conductive ring 3 '*' an insulating compressible seal or a compressible insulating tube 35 'the projection 1 1 of the silver coating, a conductive ring 3' and a nut 37 · In the transducer according to FIG. 1 comprises the device for the individual electrical connection of the conductive layers the door device and the indoor device a device tin application of electrical signals to the conductive layers C ¹ ^ i door device and the internal device.

A preferred method of manufacturing an electromechanical transducer comprises assembling a panic of dielectric stents at a distance from one another, a conductive layer being provided on each of these stators, and each of these stators having openings extending through them, and thin vibration diaphragm devices or thin vibration sensors comprising a layer of conductive material and held between the stator device or stators. The method comprises electrostatically polarizing the tin-plated door device by applying a high dead gold from the conductive layer of each stator part to the conductive layer

409812/0946

BATH ORIGINAL

dor Mombrnnvorrichtung. The process step of polarizing the assembled stator device preferably comprises a process step of applying the same high potential difference from the conductive layer or door device to the conductive layer of the membrane device. This can for example be achieved in that the two Aiinchli'ssr "dos stator IIa5; so vcrbinrlet while illustrates · Connection dcv membrane device with a normative Vo is tential connected, for example, 5 ^ V or more, during a period of at least a few seconds bir: to half an hour or flour ·. The polarized dielectric stator device 10; 11 brings electrical direct voltage. *; / Oldei- the same polarity relative to the layer of conductive material. 1 l? A, 1? '> Of the Henibran device.

By producing the transducer according to the dom just described preferred practice has been the activities during the AuJTbcius vercinfiiclit, and there will be a degradation dor Iloch-ΠΓ 'τιηυη ^, ^ ηΓ, -Ιπ ·' ..- "hroiit! der Polar is ifvunp; or LndT'ng dor Stators reached. Also, no handling of the electret as individual components is required after the charge has been listed, and iode adverse effect on the surface coating of the electrets, such as a surface contamination by fingerprint « prevented. Converters in which electret stators are used,

409812/0946 bad OfflGiNAt

which have been polarized by dirses method, have a higher sensitivity or performance and lower distortion than transducers in dom: n stators are used that were polarized before dom assembly in the transducer by the method described above, because the potential differences between the central The membrane and the conductive layers of the electret stators are approximately the same due to the surface charges of the electret stator after the charging process. This is important for a distortion-free operation of the converter of the counter-clock type. Also, the best electret stators have been formed while maintaining an air gap between one of the charging electrodes and the electret material. When the electret stators are charged after the transducer has been assembled, air gaps are provided between the membranes and the electrodes comprising the silver coatings of the stators.

Compared with previous electrostatic earbuds Converters constructed in accordance with the invention below Use of electret, which before assembly in the Converting the manner described above "; has been loaded are, also a higher susceptibility to conversion, -performance, -good or the like, because of the high equivalents DC bias of, for example, 1 IcV or more, and the converters have a low Distortion; however, the procedure for loading the WamHer-

409812/0946

BATH ¹

electretβ to be preferred after assembly, as it an even higher sensitivity and lower distortion is achieved.

In Fig. 0 of the drawing is shown a, partially schcinntisdics, circuit diagram of two watch headphones, each earphone has a transducer that is constructed according to the invention and calibrated for a push-pull drive, these earphones or the transducer on you. Au. * S, rav »gr» Bchaltun.cren of a stereophonic sound system can be coupled. The resistors h0 can individually have values of, for example, 10 megohms, and are connected to the connections of the stators 10, 11 and the membrane device I7 ^f "17h, i '^ n, lP" b of each transducer ", as can be seen from FIG Representation results. The resistors can be positioned on or on the back of each transducer. In some designs, the resistors can be shaped or not required and can therefore be omitted A stereophonic sound source (not shown) are connected to the transducers to electrical interference frequency signals, which cause a gage clock operation of each of the transducers.

E «is still possible. Loudspeakers, the transducers according to the Invention comprises building up a group

409812/0948

combined by transducers in order to achieve a larger radiation area. The transducers according to the invention can furthermore, for example, be guided or built up to all Gogontijktmikrophono and Vlbreitungsaufnehiner or Schwinßurißs-Tonabnehiner.

SAO ORlGlNAI

"• WNAL 409812/0948

Claims (1)

- 23 patent claims 1. Electromechanical converter, characterized by a pair of electrostatically polarized dielectric stators (10, 11), each of which has a conductive part (10b, lib) and openings (10a, 11a) passing through the stator and has a thin vibration membrane device (17a , 18a) comprising a layer of conductive material (17a, 17b); means (19, 20, 21) for holding the diaphragm device between the stators spaced therefrom; and a device (25-35, 31a, 32a, 33a, 3 ¹ Ia) for the individual electrical connection of the conductive parts of the stators and the conductive layer of the membrane device. 2. Converter according to claim 1, characterized in that the polarized dielectric stators (10, 11) DC electric fields of the same polarity relative to the layer of conductive material (17a, 17b) of the membrane device. 3. Converter according to claim 1 or 2, characterized in that the device for individual electrical Connection of the conductive parts (10b, lib) of the stators and the conductive layer of the membrane device (17a, 17b, 18a, 18b) a device (27, 33, 33a) for applying electrical signals to the conductive Parts of the stators and the conductive layer of the membranes 409812/0946 - 21 »- includes. l ». Converter according to Claim 1, 2 or 3, characterized in that the openings (10a, Ha) of the pair of stators are essentially aligned. 5. Transducer according to one of claims 1 to Ί, characterized by a frame (19, 21) made of insulating material, which holds the membrane device, wherein the membrane device comprises a pair of plastic films, on each of which a conductive layer is provided, wherein a conductive layer is also provided Spacer frame (20) is provided between the conductive layers on the plastic films and in conductive contact with them. 6. Converter according to one of claims 1 to 5, characterized in that the stator or the stators (10, 11) is or are or includes an electret. 7. Converter according to one of claims 1 to 6, characterized in that the thickness of each of the stators (10, 11), excluding the conductive part, approximately equal to the product of the dielectric constant of the respective Stator multiplied by the distance between the diaphragm device and each of the stators. 4098 12/0946 8. A method for producing an electromechanical converter ^ in particular according to one of claims 1 to 7, characterized by the steps of assembling a pair of dielectric stators, wherein on each of these stators is provided with a conductive part and each of these stators has openings extending through the same, and a thin, vibrating membrane device, which comprises a layer of conductive material and is held between the stators, at a distance from each other; and the electrostatic polarization of the assembled stators by applying a high potential difference from the conductive part of each stator to the conductive layer of the membrane device. 9. The method according to claim 8, characterized in that the step of polarizing the joined Stators or the assembled stator device, the process step of creating the same high potential difference from the conductive part of each stator to the conductive layer of the membrane device. A0981 2 / Ü946