EP1538875A1 - Induction coil with cross-sensitivity for hearing aids - Google Patents

Abstract

The coil (7) has a cylindrical core (1) and at least one ferromagnetic core expansion (3) that expands the core radially at one end. The core expansion element is mounted on one end of the core in the form of a ferromagnetic ring or disk. The core expansion element can be stuck, plugged or pressed onto the core end. An independent claim is also included for a method of manufacturing an induction coil.

Description

The present invention relates to an induction or telephone coil for a hearing aid with a cylindrical core and at least one core extension that is the core of a its ends enlarged in the radial direction. Furthermore The present invention relates to a corresponding method for producing such an induction coil for hearing aids.

In hearing aids induction coils for receiving magnetic Signals used. Typical applications in which Induction coils can be exploited next to the Telephoning the care of hearing impaired people in schools, Cinemas, churches and the like.

The induction coils currently used in hearing aids are typically 9 mm long and 1.4 to 1.9 mm thick. Due to the relatively large length dimension comes it to coupling effects, for example, with the hearing device listener or the battery contacts. Furthermore, this large opens Length only a small margin for placement or movement the induction coil in the hearing aid.

To avoid the coupling effects, the induction coil in usually placed in the hearing aid as far away from the listener. Because of their length often not sufficiently large Distance to the listener can be achieved in these cases between the hearing aid handset and the induction coil a mu-sheet metal used. Although this Mu metal sheet reduces the coupling effects, but it also reduces the sensitivity the induction coil.

The above-mentioned induction coil is from the document DE 81 05 651 U1 known. There, a core is used in which at the lateral ends, the winding to be attached later limiting thickening are appropriate. These thickenings can be made of the material from which the bobbin itself, e.g. Mu-metal. For the thickenings or lateral ends of the coil but can also plastic be used. The shape of the thickenings on the ends of the bobbin has the shape of attached discs, which are concentric to the core. Thus they define one available changing room.

Another induction coil for use as electromagnetic Induction converter in electrical hearing aids is known from the document DE 43 26 358. The bobbin the induction coil consists in this case of a stamped part. At the free end surfaces of the bobbin are formations arranged with receiving means for insulating parts. The Insulating parts have electrically conductive connection elements Contacting the coil winding on.

The object of the present invention is therefore to the manufacturing cost of induction coils for hearing aids to reduce.

According to the invention this object is achieved by an induction coil for a hearing aid with a cylindrical core and at least one ferromagnetic core extension, the Core enlarged at one of its ends in the radial direction, the core extension being mounted on one end of the core is. Consequently, the core expansion core is in two parts.

Further, the invention provides a method for manufacturing an induction coil for a hearing aid by providing a cylindrical core and mounting a Winding on the core, as well as mounting at least one ferromagnetic Core expansion, which is at the core of one of his Ends in the radial direction enlarged, on the core.

By the core expansion at the end of the core in the radial direction the induction coil can be shortened overall. Of the The reason for this is that the inductance of the induction coil through the ferromagnetic core expansion increases and thus the antenna effect of the induction coil is increased.

As a result of the shortening of the induction coil, it can in the hearing aid be placed better. Among other things, she can attend one Locate at the less coupling effect too are expected. In turn, this can be the case with devices that have a lower Have output power, i. their listeners lower Produce stray fields on a mu metal shield between Handset and induction coil are dispensed with.

The shortening of the induction coil also has the advantage that less space is available in the hearing aid for the induction coil must be made. Thus, the hearing aid can be total make smaller, which is a primary goal of hearing aid manufacturers is to be considered.

The radial core expansion in the end region of the induction coil core also leads to a better magnetic page sensitivity. This is due to the fact that the magnetic field lines at the end of the core through the ferromagnetic Material of core expansion also in the radial direction be directed to the outside. This increased page sensitivity has advantages when telephoning, because the induction coils are usually arranged vertically in the hearing aid and thus their highest sensitivity in the vertical direction have. The sensitivity in the lateral direction towards An earphone held to the ear is at the induction coils corresponding with simply designed cylindrical cores low. The core expansion becomes the directional characteristic but toned down, making changes to the Position of the induction coil or the head of the hearing impaired less critical. By an asymmetrical core expansion For example, cross-sensitivity may be special be improved for telephoning.

The core extension is mountable on one end of the core, i.e. formed in two parts with this. This can be a very cost effective solution compared to a dumbbell coil be realized because the core of the known dumbbell coil is turned to the full.

In a preferred embodiment, the core extension exists from a ferromagnetic ring or a ferromagnetic Disc. This makes it easy to produce and assemble. In addition, through the ring or the disc a better magnetic lateral or lateral sensitivity in all radial directions relative to the induction coil core given.

Preferably, the core extension is at one end of the Kerns glued on, plugged or pressed. hereby can realize a cost-effective installation.

In addition, the core expansion can be made of a mu-metal consist. The permeability of this metal is advantageous adjustable according to requirements.

Particularly preferred is when at each end of the core respectively a core expansion is arranged. This will automatically also fixed the winding on the core. Special fixations such as plastic leaflets or rings, need then no longer be applied to the core.

FIG 1

eine perspektivische Ansicht einer erfindungsgemäßen Induktionsspule;

FIG 2

eine Ansicht einer Einzelscheibe der Induktionsspule von FIG 1;

FIG 3

eine Draufsicht auf eine Induktionsspule mit Richtcharakteristik nach dem Stand der Technik; und

FIG 4

eine Draufsicht auf eine erfindungsgemäße Induktionsspule mit Richtcharakteristik.

The present invention will now be explained in more detail with reference to the accompanying drawings, in which:

FIG. 1

a perspective view of an induction coil according to the invention;

FIG. 2

a view of a single disc of the induction coil of Figure 1;

FIG. 3

a plan view of an induction coil with directional characteristic according to the prior art; and

FIG. 4

a plan view of an inventive induction coil with directional characteristics.

The embodiment described in more detail below a preferred embodiment of the present invention represents.

An induction coil according to the invention consists of a core 1, on which a winding 2 is wound. At the two ends of the core 1, Mu metal disks 3 and 4 are applied. The mounting of the Mu-metal rings 3 and 4 takes place by sticking or pressing on the cylindrical core 1, as indicated in FIG 1 with the arrows.

A Mu-metal ring 3 typically has the one shown in FIG Dimensions. Accordingly, he has an outer diameter of about 1.5 mm and a thickness of about 0.5 mm. Further points he in the example chosen a hole with the inner diameter of 0.5 mm.

Alternatively to the Mu-metal rings shown in FIGS. 1 and 2 3 and 4 can also be on the front sides of the Kerns 1 corresponding Mu-metal discs are glued.

Both the Mu metal discs and the Mu metal rings 3 and 4 cause a dumbbell shape of the core or the induction coil. Thus, not only the winding 2 is fixed on the core 1, but it takes place at the end of the core 1 and a deflection the magnetic field lines in the radial direction. Furthermore is through the Mu-metal discs or Mu-metal rings 3, 4 increases the end face of the induction coil, so that a Collector effect of the disks or rings, i. the core extensions, results.

The Mu metal collector discs or rings lead to a increased sensitivity of the induction coils, so this can be shortened. At the following numerical example can the effects will be better illustrated: Will the coil shortened from 9 mm to 7.5 mm, so their sensitivity is reduced on average by 1 to 2 dB. This sensitivity reduction can be done by sliding mu-metal collector discs or rings with the dimensions shown in FIG 2 the ends of the core of the induction coil are compensated. This shortening leads to the advantages mentioned of the better ones Placeability of the induction coil and the reduction the hearing aid size.

In Figure 3 is a conventional induction coil according to the prior Technology reproduced. It has simple linear structure and a relatively high directional characteristic, such as it is indicated by the clubs 6. The directional characteristic arises primarily from the fact that the magnetic Field lines almost exclusively at the small end face the core of the induction coil 5 enter or exit.

In contrast, in FIG. 4, a dumbbell-shaped, inventive Induction coil 7 shown. Through the mu-metal discs or rings at both ends becomes the directional characteristic the induction coil 7 reduced. The highest sensitivity Although the induction coil is still in Coil longitudinal axis direction, which is side sensitivity However, significantly increased, which by the rounder clubs 8 is indicated. This increased page sensitivity makes especially on the phone positive.

Claims (8)

Induction coil for a hearing aid with a cylindrical core (1), and at least one ferromagnetic core extension (3) which increases the core (1) at one of its ends in the radial direction, characterized in that
the core extension (3) is mounted on one end of the core (1). An induction coil according to claim 1, wherein the core extension (3) a ferromagnetic ring or a ferromagnetic Disc exists. Induction coil according to claim 1 or 2, wherein the core extension (3) glued on one end of the core (1), attached or pressed on. Induction coil according to one of the preceding claims, wherein the core extension (3) consists of a Mu metal. Induction coil according to one of the preceding claims, wherein at each end of the core (1) each have a core extension (3) is arranged. A method for producing an induction coil for a hearing aid Providing a cylindrical core (1) and Mounting a winding (2) on the core (1), marked by Assembling at least one ferromagnetic core extension (3), which increases the core (1) at one of its ends in the radial direction, on the core (1). Method according to claim 6, wherein the core extension (3) glued on the one end of the core (1), plugged or is pressed on. The method of claim 6 or 7, wherein at each end of Kerns (1) each core extension (3) is mounted.

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