EP1156701A2 - Electroacoustic transducer with small dimensions - Google Patents

Abstract

The invention relates to electroacoustic transducers with small dimensions, in particular those with a housing with an outer diameter of 15 mm and smaller. The invention is characterized in that it has a pot-like pot component (11) made of a metallizable plastic, which is encapsulated by a housing component (12) made of a non-metallizable plastic, and that at least the inner surface of the pot component (11) is coated with a Metal coating is provided. Refinements relate to the contacting of the electroacoustic transducer and a variant for radially magnetized magnetic plates. <IMAGE>

Description

The invention relates to electroacoustic transducers with small dimensions, in particular those with a housing with an outer diameter of 15 mm and smaller.

With the increasing miniaturization of electroacoustic transducers for use in Cordless phones, in cell phones, in headphones, in dictation machines, in screens from Integrated computers and the like more, problems occur that are classic Converter technology has not existed. A major problem is compliance with the Transformer characteristic of the larger with the reduction in dimensions becoming relative tolerances while maintaining constant or even reducing the unit costs, because, due to the high number of units, the question of costs is an essential one more attention is paid than with large-volume converters, which in small Numbers can be built for special applications.

Classic electroacoustic transducers that work on the electrodynamic principle, consist essentially of a pot-like housing, open on the front, into which a magnet system is used in the front, which consists of the actual magnet and a there is a multi-part yoke, the yoke having an annular air gap on the front trains. A membrane attached to the front of the magnet system has one Voice coil that protrudes into the air gap of the yoke and there in the axial direction can swing. The individual yoke parts are mostly: a pot-like, bottom side arranged part, in the center of which the magnet is glued and a circular Front part, the outer circumference of which forms the inner circumference of the air gap.

A particular problem with miniaturization is centricity or eccentricity between the air gap and the voice coil because the membrane closes with every eccentricity begins to wobble and the transducer characteristics are disturbed. Through the Miniaturization of the transducers now represent eccentricities that in large format Transducers are quite permissible, already a serious quality problem, since the relative Eccentricity with constant absolute tolerances and downsizing of the components of course, gets bigger with the miniaturization. So it is with converters with one Diameter of the housing of about 15 mm is already necessary, the eccentricity in the Press area of a few hundredths of a millimeter to get to the given Converter characteristics without distortion.

If you consider that the tolerances of the commonly used parts: Housing, magnet system, retaining rings and the like. in normal converter construction in the range of Tenths of a millimeter, for high-precision parts, as they obey today for small ones Transducers used are in the range of five hundredths of a millimeter immediately apparent that it is easy even with average pairings of the tolerances can lead to eccentricities that are no longer in the acceptance range. At unfavorable pairings are shot far beyond any permissible eccentricity.

The invention now aims to solve these problems and make a converter smaller Dimensions, in particular with an outer diameter of the housing of 15 mm or including specifying the inexpensive the required accuracy and especially the necessary centricity achieved.

According to the invention, an electroacoustic transducer is characterized in that it is made of a pot-like component having at least one radially projecting projection made of a metallizable plastic, the component having a housing shape is cast from a non-metallizable plastic, and that the inner Surface of the pot-like component and at least part of the surface of the radial protruding projection are provided with a metal coating.

A method according to the invention for producing such an electroacoustic Transducer is characterized in that a component with the shape of the Magnetic pot including the contacts of the electroacoustic transducer made of metallizable Plastic is made that then in the same injection mold, but under Use of another upper part of the injection mold, this component with one not metalizable plastic is cast in the housing shape, and that as Magnetic pot and contacts before surface areas with a metal coating will be given away. The latter can be achieved, for example, by chemical activation, subsequent copper plating and finally nickel plating.

The inventive measures achieve a one-piece body that both the usual magnetic pot as well as the housing and finally the contacts themselves has one piece and, since these parts are formed and manufactured in a single shape be the tolerances inevitable according to the prior art and their Avoids addition or interaction.

The method according to the invention is for small size electroacoustic transducers Particularly suitable, since only with such miniaturized transducers by Copper plating and nickel plating achievable metal cross sections are sufficient to Ladder can be used.

die Fig. 1 den Aufbau eines elektroakustischen Wandlers gemäß dem Stand der Technik in rein schematischer Darstellung vor dem Zusammenbau,

die Fig. 2 einen erfindungsgemäßen elektroakustischen Wandler in schematischer Ansicht,

die Fig. 3 und 4 eine erfindungsgemäße Variante,

die Fig. 5 einen Wandler mit Radialmagnet gemäß dem Stand der Technik und

die Fig. 6 einen erfindungsgemäßen Wandler mit Radialmagnet.

The invention is explained below with reference to the drawing. It shows

1 shows the structure of an electroacoustic transducer according to the prior art in a purely schematic representation before assembly,

2 shows an electroacoustic transducer according to the invention in a schematic view,

3 and 4 a variant according to the invention,

5 shows a converter with a radial magnet according to the prior art and

6 shows a transducer according to the invention with a radial magnet.

Fig. 1 shows the parts of an electroacoustic essential for the invention Converter in its construction according to the prior art. The bottom, Pot-like yoke part 1, which is usually made of soft iron sheet by deep drawing is. This means that the inside diameter is sufficiently precise, but the outside diameter depends on the sheet thickness, the sheet type and its ductility and is therefore tolerant. When installing the pot-like yoke part 1 in the by injection molding Manufactured housing 2, there are joining gaps and thus eccentricity. If if one chooses overlapping tolerances in order to avoid joining gaps, this is the case Deformations and internal mechanical stresses, which in particular Temperature loads become free and the (not shown) sensitive, on Deform the membrane attached to the top part of the housing, which now results in acoustic Distortion and wobble of the membrane when vibrating.

Usually, two contacts 4 for the supply wires for the voice coil (not shown) of the membrane are arranged on a projection 3 of the housing 2. These contacts 4 usually consist of sheet metal as stamped or bent parts, which are to be fitted to the projection 3 with a precise fit and not wobbling. These parts must therefore be fixed by gluing, using an adhesive drop with a volume of about 0.3 mm ³ . This dosage and correct placement encounter major problems in automatic series production and require human monitoring and support. The manufacture and handling of the contacts themselves, in their original size their maximum dimensions are in the range of about 1.5 mm, is difficult.

These problems are completely avoided by the measures according to the invention. According to the invention, a component 11 is produced in an injection mold essentially has the shape of the pot-like yoke part 1, but on the one Projection 3 corresponding projection 13 is integrally formed with. This component consists of a metallizable plastic and it is when in the injection mold is solidified accordingly, this is not removed, but only the top of the Injection mold is replaced by another upper part and this then becomes pot-like Component 11 in essential areas surrounded by a plastic that is not is metallizable and finally has an outer shape, at least in essentially the shape of the housing 2 of conventional electroacoustic transducers corresponds. This outer part 12 preferably has at one point, as shown in FIG. 2, a recess or notch 16 so that an area 14 'of the projection 13 over a free surface lying in the area of the notch 16 with the inner area of the Pot-like component 11 is connected.

A cover 15 is located between the contact part 14 'and its counterpart 14 " provided, through which the surface of the projection 13 in two metallizable areas is separated, which have no connection to each other that could be metallized. As a result, the two contacts are electrically separated from one another. The material of the Housing part 12 encloses the outside (the underside not visible in FIG. 2) of the Pot-like component 11 entirely.

If the surfaces to be metallized are now to be metallized, it is after appropriate activation of the plastic in a bathroom possible later contacts 14 ', 14 "can also be used immediately, in the example shown, via the contact 14' and the notch 16, the inside of the pot-like component 11 and the small-area, to metallize the exposed outer part of its jacket in the region of the notch 16.

This metallization, for example from the application of a copper layer and the subsequent application of a nickel layer by galvanic processes, belong to the state of the art and need no further explanation here. It's just supposed to be advised that the formation of a functional coating Layer thickness of the nickel layer should be at least 25 microns and preferably at least Is 100 µm.

The further processing of the semi-finished electro-acoustic transducer thus produced, takes place in the usual way: the magnet becomes in the center of the pot-like component 11 including the disc-shaped yoke part already glued to it, whereby by Appropriate guidance or teaching ensures sufficient centricity. It then the membrane, if necessary with a mounting or retaining ring on Housing part 12 attached, the voice coil mounted on the diaphragm centrally in the air gap comes to rest. The voice coil supply wires are in the Area of the membranes fastening from the inside of the then closed transducer guided and each with one of the two contacts 14 ', 14 "mechanically and electrically conductively connected, for example by friction welding or ultrasonic welding.

The outer sides or the lower sides of the two contacts 14 ', 14 "serve the Contacting the electroacoustic transducer in the device in which it is used.

Because the membrane, the coil attached to it and the retaining ring of the membrane in one Centricity is guaranteed to a high degree. There the retaining ring is attached to the housing part 12 and this part in excellent Centricity to the pot-like part 11 is the problem of the eccentric arrangement the voice coil in the air gap solved as best as possible. Due to the one-piece training of Pot-like component 11 and the housing part 12 with one another and with the contacts 14 ', 14 "is the entire handling for such a highly miniaturized electro-acoustic Converter compared to handling according to the prior art is extraordinary improved.

3 and 4 show a variant possible by the measures according to the invention with a slightly different construction of the transducer than that obtained according to FIG. 2: It will thereby how the exploded in the axial direction in the manner of an explosion sketch The illustration shows a body part 21 with a correspondingly partially galvanized surface extrusion-coated with a housing part 22, the material of the housing part 22 not is galvanizable. The body part 21 has integrally formed a central elevation represents the inner yoke part 23.

In the annular gap thus formed between the inner yoke part 23 and the housing part 22 becomes a ring magnet 24 magnetized in the axial direction and also one above it ring-shaped pole plate 25 inserted and with the body part 21 and the Housing part 22 glued.

By manufacturing in a single mold using a replaceable one Head part one achieves the best possible accuracy and the avoidance of any addition of tolerances, so that the insertion of the pole plate 25 into the corresponding recess of the housing part 22 does not contribute to the otherwise feared eccentricity.

3 and 4, the contact, unlike in Fig. 2, is not shown, it can in an analogous manner as there or else.

The fitting of the pole plate 25 shown in FIG. 4 need not be as shown take place, since it can be quite advantageous, the recess in the housing part 22 in axial direction so large that the pole plate in the axial direction only sits on the ring magnet 24 and is glued to it and the recess in Housing part 22 only takes over the radial guidance.

Another variant is shown in FIGS. 5 and 6; one (or several appropriately arranged) used radially magnetized magnet. 5 shows this the previous structure of such electroacoustic transducers according to the state of the Technology and Fig. 6 shows a variant according to the invention.

As can be seen from Fig. 5, there is an electroacoustic transducer with radial magnetized magnets made of several plate-shaped magnets that are normal to the Platelet main plane are magnetized, these platelets along the lateral surface of a regular polygon. The cause of using this The arrangement is that it is extremely difficult to use radial magnets with radial To produce magnetization, so that you are quasi-ring-shaped Arrangement helps.

As can be seen from Fig. 5, this is radially inside and radially outside Magnetic plates each have a yoke part, thus an inner yoke part 33 and an outer one Yoke part 35. These two yoke parts are on the front of the electroacoustic transducer, which faces a membrane 37 shown in this figure, an air gap, into which a voice coil 38 is immersed. The two yoke parts are each in one Inner housing 31 and an outer housing 32 mounted, the outer housing 32 also the membrane 37 carries.

In the embodiment according to the prior art, as shown in FIG. 5, it is necessary to cut the two metallic yoke parts 33, 35, namely by milling edit, since there is no other possibility to a flat as possible Contact between the individual magnets 34 and the sides facing them of the yoke parts 33, 35 to come. In the production itself, the yoke parts are velvet their plastic housings held in a centering device and the magnets 34 are then inserted into the cavities released for them and with the Yoke parts glued. After the adhesive has hardened, the transducer is used to assemble the Membrane 37 removed from the centering device and further assembled.

The invention now allows these complicated work processes to be drastically reduced Simplify and thus cheap in some areas of application Magnet arrangement to supply a larger width of the application, because the so built converter are no longer covered by the previous costs. On Converter of this type according to the invention is shown in FIG. 6: A partially galvanic Metallized outer housing 42 and an at least partially galvanized yoke part 41 are provided with correspondingly flat surfaces 43, 45 during injection molding, between which the plate-shaped magnets 44 lie in the assembled state come. The surfaces 43, 45 and the adjacent areas (Fig. 6 up), the finally leave the air gap between them are galvanized with metal coated and serve as a yoke for the magnet system. It can only get here to one to come a part of the surface covering coating, the yoke part 41 and Housing part 42 made of two different types of plastic in a two-stage Injection molding processes are produced, as is shown in the description of FIG. 2 for the variant there has been described.

For centering, it is possible, for example, to place the two parts 41, 42 upside down on one Center ring to insert, which corresponds to the air gap to be formed and then from the then protruding upwards from the bottom, the individual magnetic plates 44 into the to thread and glue the pockets formed.

A centrally symmetrical transducer body has been shown in Fig. 6, but it is of course also possible and advantageous here, the contacts, as with the 2 and 3, to be trained at the same time and also galvanized, what can happen analogously to the formation of Fig. 2 or 3 and here no closer Explanation needs more.

In Fig. 6, an annular groove is indicated on the upper outer edge of the housing part 42, the serves to receive a fastening ring for a membrane, this ring groove can of course, be designed differently, the attachment of the membrane to one Housing part is part of the state of the art, due to the integral manufacture of Injection molding can achieve extremely high centricity without this being otherwise would cause necessary costs.

The invention is not limited to the exemplary embodiments shown, but rather can be modified in various ways. It is essential that at least part of the Yoke-forming parts of the magnet system of an electroacoustic transducer are not considered to be discrete components are produced, but as a metallic coating on a through Injection molded plastic part of the electroacoustic transducer. Especially it is preferred that all yoke parts consist of such metallic coatings, because thereby achieving the best possible centering in the simplest and most economical way can be.

In an advantageous embodiment of the invention, it is also provided for Contacting the electroacoustic transducer provided contacts in this way create and so the separate manufacture and subsequent application of metallic To avoid contacts.

In both applications it is possible instead of the copper plating and subsequent nickel plating to apply another metallic coating, sofeme this only, if it is used for the yoke parts, the necessary magnetic Features, this is particularly the case when you have pure iron or Uses cobalt. For the creation of contacts to contact the electroacoustic transducer, it is of course possible to use gold or applying thicker copper layers, a corresponding multi-stage treatment or a separate galvanic treatment of the yoke parts and the contacts is then necessary, but plays because of the uncritical handling of the already finished cast transducer body no longer a critical role.

Claims (4)

Electroacoustic transducer with small dimensions, in particular with a housing with an outer diameter of 15 mm and smaller, characterized in that it has a pot-like pot component (11, 21, 31) made of a metallizable plastic, which has a housing component (12, 22 , 32) is cast from a non-metallizable plastic, and that at least the inner surface of the pot component (11, 21, 31) is provided with a metal coating. Electroacoustic transducer according to Claim 1, characterized in that the pot component (11, 21, 31) has at least one radially projecting projection (13), and in that at least part of the surface (14 ', 14 ") of the radially projecting projection (13) is provided with a metal coating. Electroacoustic transducer with small dimensions, in particular with a housing with an outer diameter of 15 mm and smaller, with radially magnetized magnetic plates (44), characterized in that it has a yoke part (41) which is metallized in the region of its outer lateral surface (43) and an annular housing component (42) which is separate from the yoke part and which is metallized in the region of its inner lateral surface (45), and that the magnetic plates (44) are arranged between the metallized lateral surfaces (43, 45). Electroacoustic transducer according to Claim 3, characterized in that the yoke part (41) has at least one radially projecting projection, and in that at least part of the surface of the radially projecting projection is provided with a metal coating.

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