US3922502A

US3922502A - Diaphragm for electroacoustic transducer

Info

Publication number: US3922502A
Application number: US537939A
Authority: US
Inventors: Shunichi Tabuchi
Original assignee: Foster Electric Co Ltd
Current assignee: Foster Electric Co Ltd
Priority date: 1975-01-02
Filing date: 1975-01-02
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25

Abstract

A circular and uniformly vibratable type diaphragm for electroacoustic transducer of flat-plane driving types is provided. The diaphragm comprises a circular nonmagnetic and insulative membrane and a series of conductors formed on the membrane and comprises radial outlet parts extending as mutually spaced at regular intervals substantially from central field to peripheral field of the membrane, arcuate outlet parts extending in the peripheral field and connecting most of peripheral side ends of the radial parts, and central parallel parts to be subjected to magnetic fluxes of associated magnetic circuits as concentratively arranged in the central field and connected in series with the other central side ends of the radial parts. Remaining two peripheral side ends of the radial parts not connected are adapted to be input or output ends of the series conductors. The shape of the central parts of the conductors is advantageously similar U-shapes.

Description

United States Patent [191 Tabuchi [451 Nov. 25, 1975 DIAPHRAGM FOR ELECTROACOUSTIC TRANSDUCER [75] Inventor: Shunichi Tabuchi, Okutarna, Japan [73] Assignee: Foster Electric Co., Ltd., Tokyo,

Japan [22] Filed: Jan. 2, 1975 [2H Appl. No; 537,939

[52] U.S. Cl. ..l79/l15.5 PV [5 l] lnt. Cl. H04R 9/02 [58] Field of Search 179/1 I5i5 PV, 181 R [56] References Cited FOREIGN PATENTS OR APPLICATIONS 6.6l3,7l3 4/l968 Netherlands I, 179/! 15.5 PV

Primary ExaminerKathleen H. Claffy Assistant Examiner-George G. Stellar Attorney, Agent, or FirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

F Nit ABSTRACT A circular and uniformly vibratable type diaphragm for electroacoustic transducer of flat-plane driving types is provided. The diaphragm comprises a circular nonmagnetic and insulative membrane and a series of conductors formed on the membrane and comprises radial outlet parts extending as mutually spaced at regular intervals substantially from central field to peripheral field of the membrane, arcuate outlet parts extending in the peripheral field and connecting most of peripheral side ends of the radial parts, and central parallel parts to be subjected to magnetic fluxes of associated magnetic circuits as concentrativcly arranged in the central field and connected in series with the other central side ends of the radial parts. Remaining two peripheral side ends of the radial parts not connected are adapted to be input or output ends of the series conductors. The shape of the central parts of the conductors is advantageously similar U-shapesi 6 Claims, 3 Drawing Figures U.S. Patent Nov. 25, 1975 3,922,502

in g/ DIAPHRAGM FOR ELECTROACOUSTIC TRANSDUCER This invention relates to electroacoustic transducers and, more particularly, to a diaphragm to be used for an electroacoustic transducer comprising a diaphragm made of a nonmagnetic and insulative material having a series of conductors and a plurality of permanent magnets arranged as respectively opposed to each other with pole surfaces of the same polarity through a slight clearance on both surfaces of said diaphragm.

Conventional flat plane driving type speakers of this kind are of such a structure as shown, for example, in FIG. 1, wherein l is a diaphragm made of a membrane of a nonmagnetic and insulative material, 2, 2', 2" and 3, 3', 3" are a plurality pair of elongated permanent magnets, each of the

respective pairs

2 and 3, 2' and 3', 2" and 3" of which is arranged as opposed to each other with magnetic pole surfaces through a slight clearance on both sides of the diaphragm l and in parallel relation to adjacent pairs so that, while the magnetic poles of the respective pairs adjacent one another in expanding direction of the diaphragm 1 will be alternately of different polarities, the poles of each pair opposing will be of the same polarity. 4, 4 are parallel strip conductors formed on the diaphragm l by such a means as a printing or the like so as to be respectively positioned intermediate between the

adjacent magnets

2 and 2', 2' and 2" or 3 and 3', 3' and 3" which conductors are connected at the respective ends with one another so as to be at least one zigzag shaped continuous conductor (as shown in FIG. 2). 5 and 6 are soft iron plates bonded respectively on outside surfaces of the respective groups of the

magnets

2, 2', 2" and 3, 3', 3" on each side of the diaphragm 1 and one of them, for example, the iron plate 5, is provided with perforations 7 for allowing sounds to pass therethrough, between the

adjacent magnets

2 and 2', 2' and 2" and so on. Dotted lines shown in FIG. 1 in spaces between the opposing and adjacent magnetic pole surfaces represent magnetic flux distribution.

The operation of the electroacoustic transducer shown in FIG. I shall be explained next.

In the drawing, the opposing surfaces of, for example, the pair of magnets 2' and 3 are of N-pole and those of adjacent pairs of the

magnets

2 and 3, 2" and 3" are S-pole, so that the magnetic flux will be caused to flow from the respective opposing N-poles to the respective adjacent S-poles so as to be substantially in parallel with the plane of the diaphragm l. The parallel sections 4, 4' of the continuous conductor are disposed thus in such magnetic flux at right angles with respect to the flowing direction of the flux.

In case an electric current is passed through the continuous conductor in the above arrangement, the diaphragm l on which the conductor is provided is subjected to an electromagnetic force effective in a direction perpendicular to the plane of the diaphragm. While the direction of the electric current flowing each of the parallel sections 4, 4' of the conductor is opposite to one another, the direction of the magnetic flux traversing each of such sections 4, 4' is also opposite to one another. Consequently, the diaphragm l is subjected to a driving force effective in a fixed direction, so that the electroacoustic transducer will be uti lized as a speaker operated in response to the direction 2 and magnitude of the current passed through the strip conductor.

It is obvious that in case the diaphragm I is caused to be vibrated by a sound contrarily to the above, there is produced an electromotive force in the conductor on the diaphragm l vibrated, so that the electroacoustic transducer will be able to be utilized as a microphone.

Now, the shape of such diaphragm as disclosed of the arrangement in the electroacoustic transducers referred to is generally rectangular as shown in FIG. 2 where the series of conductors generally of copper, aluminium or the like material formed by, for example, a print-wiring process on the diaphragm membrane is in a zigzag pattern 8 so as to correspond to parallel rows of the elongated permanent magnets, or is often circular as shown in FIG. 3 where the conductors are arranged in a vortex shape 10 having concentric circular sections. Such circular diaphragm having vortexshaped conductor may be used in combination with the elongated permanent magnets of parallel arrangement but, in this case, the same driving effect at least as in the case of FIGS. 1 and 2 cannot be expected so that it will be required to arrange the permanent magnets in a special pattern other than the simple parallel pattern.

In either cases, further, the rigidity and elasticity of the diaphragm having the metal conductor thereon must be well balanced in order that the sound transducing or reproducing frequency bands of the transducer referred to will be made uniform and also expanded. With this regards, the circular diaphragm having vortex conductor may be preferable while confronting'the above discussed problem. In the case of the rectangular diaphragm, the elasticity of the same is hard to be uniform depending on the extending direction of the respective conductor sections as the conductors act as a rib, so that the entire diaphragm is hard to vibrate uni formly. In the case of the circular diaphragm of vortex conductor, further, at least an end of the conductor comes to the centre of the circular diaphragm and it will be necessary to connect such a pull out lead wire as a copper foil to the centre of the diaphragm, which will cause bad influences to occur in the vibration of the diaphragm.

The present invention has been suggested to solve such problems as referred to in the above. According to the present invention, the problems have been successfully solved by providing on the circular diaphragm a series conductor comprising radial outlet parts arranged at substantially regular intervals as extended from the centre side to the peripheral side of the diaphragm, peripheral arcuate parts respectively connecting peripheral side ends of said radial outlet parts with one another, and central parallel parts respectively connected with centre side ends of said radial outlet parts.

A main object of the present invention is, therefore, to provide a diaphragm for electroacoustic transducers enabled to obtain uniform vibrations and a flat transducing or reproducing frequency characteristic.

Another object of the present invention is to provide a circular diaphragm having a conductor including linear and parallel sections which intersect magnetic fluxes of associated magnetic circuits, so as to enable it possible to render the diaphragm vibration uniform and to be used in combination with magnetic circuits that required none of specially designed arrangement of the permanent magnets.

The present invention shall now be explained in detail in the following with reference to a preferred embodiment as shown in accompanying drawing, in which:

FlG. is a fragmentary sectioned view of a general electroacoustic transducer showing essential parts thereof;

H65

2 and 3 are plan views of conventional diaphragms;

FIG. 4 is a plan view of a diaphragm of the present invention; and

FIG. 5 is a sectioned view of the diaphragm shown in FIG. 4 taken along a line V V in FIG. 4.

Referring now to FIGS. 4 and 5, 11 is a circular diaphragm made of such highly nonmagnetic and insulating material as, for example, polyimide, polyester, mica, phenol or the like, 12 is a group of substantially U-shaped conductors, in which A, is an innermost part of the U-shaped conductors, A, is a second part of the U-shaped conductors arranged outside the innermost part A, and so on so that many U-shaped conductors are arranged outside in the same manner. An end of the conductor part A, is extended outward so as to form a starting terminal 14 of the whole conductors and the other end of A, is connected with one end of the next conductor part A through a radial outlet part 16, arcuate outlet part 16" and radial outlet part 16", the conductor A is connected at the other end with an end of a next U-shaped conductor part A, through another radial and arcuate outlet parts so that the respective U- shaped parts will be all sequentially connected in series, and an end of the outermost conductor part is connected through similar outlet parts to an end terminal for the whole conductors. In this arrangement, the arcuate outlet parts are preferably located at the peripheral section of the diaphragm where the same is fitted to a supporting ring 13.

That is to say, the conductors are print'formed on the diaphragm so as to have the input or output ends positioned on the supporting ring and have the effective conductor parts for the magnetic driving concentrated in the central section of the diaphragm so as to render distribution density of such effective conductor parts to be high and thus the inertia at the central section of the diaphragm to be larger.

Further, the distribution density of the conductors disposed in the range between the central section and the peripheral section of the diaphragm, that is, of the radial outlet parts is made low as arranged at regular intervals, so that the increase of the inertia in this range of the diaphragm by the conductors will be prevented,

a proper elasticity will be given and the diaphragm will be able to vibrate uniformly. Further, the material thickness of the central conductor parts is to be properly selected so that the inertia at the central section of the diaphragm can be properly selected or controlled and, also, any desired elasticity of the diaphragm can be obtained by properly selecting the thickness of the diaphragm material, Thus, with a proper combination of conductor distribution density and quality and thickness and the quality and thickness of the diaphragm and conductor materials properly selected, a uniform transducing or reproducing frequency characteristic will be able to be obtained while expanding the transducing or reproducing frequency band.

It will be understood that the diaphragm of the present invention can be widely used for speakers, headphones, microphones and the like electroacoustic transducers.

What is claimed is:

l. A diaphragm for electroacoustic transducers comprising a circular diaphragm membrane of a nonmagnetic and highly insulative material, and a series of conductors formed on said membrane and including radial outlet parts arranged substantially at regular intervals as extended from central section to peripheral section of the circular membrane, arcuate outlet parts respectively connecting said radial outlet parts with one another at their ends on the peripheral side, and central parallel conductor parts disposed substantially in the central section of the circular membrane and connected in series with the other central side ends of the radial outlet parts.

2. The diaphragm according to claim I wherein said central conductor parts comprises a plurality of conductor parts of respectively similar U-shapes, and respective ends on the peripheral side of two of said radial outlet parts are adapted to form both terminals of said series of conductors.

3. The diaphragm according to claim 1 wherein said arcuate outlet parts are substantially disposed on the peripheral section of the diaphragm membrane.

4. The diaphragm according to claim 2 wherein said U-shaped central conductor parts are concentratively arranged in the central section of the diaphragm membrane so that distribution density of the series conductors will be high at the central section,

5. The diaphragm according to claim 1 wherein said series of conductors is made of copper.

6. The diaphragm according to claim 1 wherein said series of conductors is made of aluminium.

I i it

Claims

1. A diaphragm for electroacoustic transDucers comprising a circular diaphragm membrane of a nonmagnetic and highly insulative material, and a series of conductors formed on said membrane and including radial outlet parts arranged substantially at regular intervals as extended from central section to peripheral section of the circular membrane, arcuate outlet parts respectively connecting said radial outlet parts with one another at their ends on the peripheral side, and central parallel conductor parts disposed substantially in the central section of the circular membrane and connected in series with the other central side ends of the radial outlet parts.

2. The diaphragm according to claim 1 wherein said central conductor parts comprises a plurality of conductor parts of respectively similar U-shapes, and respective ends on the peripheral side of two of said radial outlet parts are adapted to form both terminals of said series of conductors.

4. The diaphragm according to claim 2 wherein said U-shaped central conductor parts are concentratively arranged in the central section of the diaphragm membrane so that distribution density of the series conductors will be high at the central section.