DE1173184B - Electromechanical converter, especially for hearing aids - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY GERMAN 40S7WW PATENT OFFICE Internat. Kl .: HOId;

EDITORIAL

HOIh; H 02k

German class: 21g-2/02

Number: 1 173 184

File number: K 37528 VIII c / 21;

Filing date: April 21, 1959

Opening day: July 2nd, 1964

Electromechanical converters, especially for hearing aids, with two in parallel at a mutual distance yokes arranged to one another, which form two air gaps that are spaced from one another, with a vibrating armature surrounded by an electromagnetic winding at a distance, which with its one end in the one air gap (clamping gap) with the interposition of a magnetic Resistance to the yokes is clamped so that it is in the other air gap ίο (Working air gap) can oscillate, and with at least one extending parallel to the armature, Permanent magnet magnetized perpendicular to the yoke disks, whose pole faces are used for generation a constant magnetic flux through both air gaps with one of the two yoke disks in magnetic contact have long been known. Electroacoustic transducers are also known in which means are provided with which the outgoing from the permanent magnet and for Working air gap of the armature guided constant flow can be influenced in order to achieve a leveling can, so z. B. such a converter in which two permanent magnets are arranged one above the other and between their pole faces of opposite polarity with the interposition of highly permeable spacers pinch one end of the anchor, its free tongue in one through two of the facing away The working air gap formed by the pole faces of the yoke arms going out of the magnets oscillate can. The armature of said transducer is made of highly permeable magnetic material and is in magnetic connection with two soft iron tongues, which are immediately next to the clamping gap bent about 90 ° to the anchor plane on opposite sides in the direction of the yoke arms are. These bent arms form two mechanically variable magnetic resistances, the are arranged parallel to the two bridge branches formed by the magnets that through them there is a possibility of influencing the constant flow in the two bridge branches. The two Tongues work directly with a protruding edge of the magnets to the To bridge magnets more or less by a soft iron flux path or that of the magnets to short-circuit outgoing constant flow more or less.

The known magnet described belongs to a different genus than the subject matter of the invention, since in the known case the pole faces of the magnets directly through flux paths of high permeability with electromechanical transducers, in particular
for hearing aids

Applicant:

Hugh Shaler Knowles, Glen Ellyn, JIl. (V. St. A.)

Representative:

Dr. J. Fricke, patent attorney,

Munich 2, Josephspitalstr. 7th

Named as inventor:

Hugh Shaler Knowles, Glen Ellyn, JIl. (V. St. A.)

Claimed priority:

V. St. v. America April 22, 1958 (730 082)

the also highly permeable armature are in magnetic contact, while for teaching the Invention is essential that also at the clamping gap of the armature between this and the magnet outgoing constant flux paths a magnetic resistance in the form of disks of non-magnetic Material is arranged.

The invention is based on the object of providing a converter of the type indicated at the outset create, in which a correction of the practically always occurring magnetic detunings in the converter even with devices of the smallest dimensions, such as those in hearing aids or pickups or the like. Use find can be done in a simple yet very effective way.

This object is achieved according to the invention in that for influencing the known per se Magnetic constant flux at least one of the clamping gap in the adjacent air space between the yokes protruding correction element made of magnetizable material is arranged, the partial Bridging the magnetic resistance of the clamping gap in the direction of one or both Yoke parts is bendable. With this arrangement is not as in the known cases of the Magnetic outgoing direct flux more or less short-circuited and thus rendered ineffective,

409 628/214

Instead, the value of the magnetic resistances in the clamping gap is carefully and individually corrected. By means of the measure according to the invention, the longitudinal flow passing through the anchor tongue can once to be influenced. They can also be used to correct the magnetic detuning in the gaps which will be explained in more detail below. The correction element can advantageously formed by a lug of the oscillating armature projecting beyond the clamping gap be. But it can also - z. B. on each side of the clamped end of the anchor - one immediately platelet-23 in contact with the anchor Correction element can be provided, the two in opposite directions perpendicular to the plane of movement of the anchor has bendable tabs protruding into the air space between the yokes.

The invention is illustrated by means of schematic drawings of several exemplary embodiments explained. Herein shows

F i g. 1 is a plan view of the magnet system of a transducer according to the invention,

F i g. 2 the converter in longitudinal section.

F i g. 3 the converter in plan view after removing a pole disc,

F i g. 4 is a schematic representation to illustrate the mode of operation of the invention Measures,

F i g. 5 shows a cross section through a modified embodiment of the transducer,

F i g. 6 to 9 further embodiments of the converter according to the invention,

10 shows another influence on the magnetic flux clarifying schematic representation and

11 shows a transducer according to the invention when used as a microphone.

The transducer according to the invention is mainly for use as a receiver (or with minor modification as a microphone as in Fig. 11) in hearing aids. He has a coil 20 which is attached between adjacent pole pieces 22 and 23 on. These in turn are through Screws 24 held together and inserted into a housing 25 as a unit.

An elongated armature tongue 27 is clamped at one end between the pole pieces with the interposition of non-magnetic spacers 28 W so that it extends freely through the coil and can move with its free end in an air gap 29 between the pole pieces with the aid of a non-magnetic Spacer 30 is formed. A membrane 31 (FIG. 2) is fastened in the housing 25, 26 in such a way that it can vibrate in the recess in the wall 26. It is coupled to the anchor tongue by a light drive pin 32. Permanent magnets 33 ^ 4 and 33 B , which are magnetized in the direction perpendicular to the pole discs, are arranged between the pole pieces on both sides of the coil 20 (FIG. 3).

In the F i g. 1 to 3 the converter is shown greatly enlarged. In fact, it is so small (e.g., the device of FIG. 1 is less than 1 cm ³ ) that there are many problems which make these devices difficult to manufacture and operate. These include, inter alia, the effective, rapid and economical production of certain critical adjustments with regard to detunings in the magnetic circuit, both during and after production.

To illustrate this problem, FIG. 4 schematically shows a pair of polarized pole pieces A and B and an armature tongue C which is clamped at one end between non-magnetic spacers S (for example made of brass). The spacers form a first pair of air gaps G ₁ and G, (which are referred to as clamping gaps). The other end of the tongue can swing freely in a working gap that forms _{a second pair of air gaps G. r} G _1.

The magnetic resistance in each of the columns G ₁ to G ₄ is with R ₁ to 7? ₄ designated. The optimum mode of operation is achieved when the ideal relationship Ζ? //?;, = /?., //? ,, exists between these values with no or only a small current flow in the coil 20. Then the entire longitudinal flow in the armature is essentially balanced for the tongue C in the state of rest.

However, when the transducer is used as a miniature telephone handset, the direct current in coil 20 will normally result in longitudinal flux in the reed. In this case, the relative values of R ₁ and R are changed, expediently by using non-magnetic disks or shims of suitable strength at G ₁ or G. from R ₁ and R., and the resulting detuning of the magnetic circuit flows in the reverse longitudinal direction through the tongue.

In order to achieve a high degree of efficiency, the permeability of the tongue should be high. A high However, permeability is accompanied by a low saturation induction. To be distortion-free To achieve playback in a receiver or listener, the flow in the tongue must be proportional be the signal stream. Therefore, a permeability of the tongue is required that is sufficient for all signal currents in the is essentially constant. If highly permeable materials are used, it is necessary that the tongue carries essentially no magnetic flux as long as there is no signal current. this allows to achieve the largest signal current amplitudes without distortion.

In order to achieve this, means are provided according to the invention to reduce the reluctance at one or the other of the clamping gaps which are located on both sides of the tongue at the clamped tongue end. For this purpose, a magnetic part 40 according to FIGS. 1 to 3 or T in FIG. 4 is provided, which can be a part of the tongue and forms an extension of the tongue beyond the clamping gap, which is accessible in such a way that it can be bent out of the tongue plane to one or the other pole piece, as by the positions of the part 40 shown in dashed lines and T in FIGS. 2 or 4 is shown.

Just mechanical centering of the tongue C with respect to the air gaps does not necessarily lead to an equalization of the flow passing through the tongue, although mechanical centering of the tongue is generally desirable for other reasons.

As is known, the reluctance can be expressed by the following equation: R = I / μ F, where / is the length of the magnetic path, F is the direction

of the lines of force perpendicular surfaces through which the flow passes, and μ is the permeability of the material along the length I. Unless otherwise specified here, it is assumed that the ferromagnetic parts of the magnetic circuit, such as the pole pieces and the armature spring, have a high permeability compared with the permeability of air. The reluctance of the gaps or the parts of the magnetic circuit in which the magnetic flux passes through air or non-magnetic metals is IiF, since μ is equal to the unit. Because μ is the same as the unit and independent of the number of lines of force, the gap reluctance is independent of the number of lines of force. When evaluating the reluctance of a gap between adjacent ferromagnetic surfaces which are not evenly spaced from each other, a surface element must be considered which is so small that the length of the lines of force / between them can be considered to be uniform. The sum of the reciprocal values of the reluctance, FIl, of all elements of the surface in the area of the gap is equal to the reciprocal value of the entire gap reluctance.

The effect of the tab-like extension 40 of the armature tongue 27 can therefore be understood as the reduction in the reluctance of the gaps G ₁ and G ₂ by expanding the normal clamping gap area. When the flap is shown by the hatched cross-section in FIG. 2 is in the plane of the tongue, this reduction is small because the length of the magnetic path from the tongue to the pole pieces is long compared to the length of the gap on the clamping surfaces. The last-mentioned gap length in the direction of the lines of force is determined by the thickness of a disk 28 W. As the lobes are bent towards a pole piece, the reluctance between the lobes and the pole piece decreases slowly at first and then rapidly as the gap length approaches zero. The reluctance between the lobe and the other pole piece from which the lobe is moving away takes only a little zxi. The lobe has the greatest effect when it is close to a pole piece.

The favorable consequences resulting from the above-mentioned reluctance adjustment have particular ones Meaning for miniature transducers.

It has already been noted that the tab 40 can only decrease the effective reluctance in the fixed gaps G ₁ , G ₂ (FIG. 4). It follows from this that the flap 40 primarily prevents a longitudinal flow in the tongue C. The longitudinal flow is sometimes arbitrarily referred to as the circulating flow, although strictly speaking it does not circulate in the ordinary sense of the word. However, when this term is used in connection with a magnetic circuit of this type, it is intended to indicate the flux which acts along the tongue as a result of the detuning resulting from the reasons described. This state is shown in the schematic representation of a magnetic circuit according to FIG. 10, in that the dashed arrows indicate a magnetic flux as it runs from the gap G ₁ along the tongue into the gap G ₄ , the gap G ₄ in this sense being complementary to the Gap G is ₁ . In the opposite direction, the dash-dotted arrow lines show the longitudinal flow which, starting from the gap G ₃ , acts in the opposite direction along the tongue and passes _{into the complementary lower gap G 2.} There is another state of magnetic detuning in such devices, which is extremely disruptive, especially in smaller embodiments. It is based on an unequal induction in different gaps, which can have numerous causes, such as changes in the dimensions, in the shape and in the metallurgical and physical properties of the material of the permanent magnets, pole pieces and armatures. All of these influencing variables can cause unequal inductions in the total flux at any one of the various gaps G ₁ to G ₄ or their counterparts 28,29. This type of detuning of the main flow in the gaps cannot be effectively eliminated with a single cloth 40, as has been described with reference to FIGS. 1 to 4.

The modified one shown in FIGS. 6 and 6A However, the form of adjustment flaps can be used for effective correction of both types of detuning handle. Here, the anchor tongue 50 shows no increase in its normal length. Instead of a thin magnetic disk 51 of preferably rectangular shape is provided, which is shown in FIG the center is drilled through at 52 for the passage of the clamping screw 24 (FIG. 2).

Like F i g. 6 shows, the disc 51 is clamped together with the tongue between two non-magnetic spacers 28 W , which in turn are arranged between the upper and lower pole pieces 22 and 23, respectively. The disks 51 carry laterally protruding tabs 51A and 51B on both sides, which can be bent upwards and downwards into different adjustment positions, which are indicated by dashed lines in FIG.

As has been shown with reference to FIGS. 2, 4, 6 and 6A, the clamping gaps at 28 or G ₁ or G _{2 are made} by bending the tabs 51A and 51B towards the adjacent pole pieces (ie G ₁ upwards, G ₂ after below).

The total number of lines of force provided by the permanent magnets for the magnetic device depends on the reluctance of the device as viewed from the surfaces of the permanent magnets. As the reluctance of the device is increased, the total number of lines of force entering the magnetic circuit from the magnets decreases. This decrease is less than it would be if the magnets had no internal reluctance. This internal reluctance of the magnets makes it possible even to change the magnitude of the magnetic flux _{somewhat in all four gaps G 1} to G ₄ , although the reluctance is only changed in one gap. In order for this to be useful in practice, the effect is increased by introducing gaps (65 in FIG. 5) between the magnets and the magnetic circuit. If one or more of the tabs are adjusted, the reluctance of the entire magnetic circuit changes slightly. Since the total reluctance of the magnetic circuit and the reluctance of the additional magnetic air gap add up, the introduction of this reluctance, which has a fixed value, has the consequence that changes in the reluctance of the magnetic circuit have very little effect. As a result, the magnet delivers an almost constant flux.

In the devices shown in Fig. 6 to 8, by precisely adjusting the tabs, the total

7 8

Flow through the gaps at both the nip and gaps at any given time is affected who also adjusts at the working gap ends of the tongue cannot be subject to such restrictions. When the tab 51 B in FIG. Rather, either a gap is bent in the position shown by dashed lines, the reluctance or both gaps at the same time up to a dance R ₁ of G ₁ has become smaller. This will affect the 5 specified dimensions. If both power flow on the path dashed in Fig. 10 and tabs 51, 4, 51 B in the same direction (ie _{greater through the gap G 4.} Since the piece 33, both upwards or both downwards from the pole) is bent 4 (N in Fig. 10) available power flow, if mainly a fixed gap is limited, a small part of the power flow will flow out. However, if the two flaps are shown in FIG. 6 diverted to gap G _3. By bending the io downwards in the opposite direction, the two fixed gaps are influenced by the lobes 51, 4 in the dashed position according to FIG. 6, and consequently the reluctance of G _{2 is} reduced and the flow becomes the flow in this gap G _{2 is} enlarged. This results in both working gaps, influenced in the same way, an increase in the flow through G ₃ . Since the flow of force, which can thus cause a detuning in the total gap flow from the pole piece 33, 4 and which is easily available, as well as in the longitudinal flow along the armature tongue, is limited, the flow can be corrected quickly.
G ₁ and G ₄ from. With precise adjustment, however, the armature is usually made of a metal, however reluctance R ₁ JR ₂ = R ₃ ZR ₄ can be met, higher permeability than the yoke disks. Hence there is no longitudinal flow through the tongue. is the effective control range for a correction-However, the flow has _{shifted from G 3} and G ₄ to G ₁ 20, which is part of the armature tongue through which G _{2 and G 2 are} shifted. This is favorable if the induction high permeability of the material of the armature limits betion in the arms of the pole pieces near the working point, since the saturation induction should be reduced very quickly in order to reach saturation there. During this to avoid the practical recovery induction. This effect is not impaired in availability in a microphone, listeners significant, where the signal change flow in Fig. 25 leads the saturation of the lobes in a listener to pole pieces to a considerable part of the constant distortion of the signals with large amplitudes. polarizing flow becomes. The form of the correction device according to FIGS. 6th

Thus, when the tab T in FIG. 4 overall upward and 6 A, is bent with a double side flap 51Λ, the reluctance of the upper gap 51 B-carrying disc 51 is such restric-G lowered ₁ and the current passing through it 30 effects not subjected, since the disc easily enlarged from river. As a result, a reversed other material with a much higher saturation induction effect at the complementary working gap and with a different strength and other transverse aim is achieved, ie the flow through the gap G ₄ at 29 cut and surfaces than the tongue 50 is smaller because decreasing the reluctance of the poses. The result is that the disk of the upper fixed gap G ₁ redirects the flow of force from the 35 even if it is thinner than the tongue, a tongue so that a smaller force-larger flow of lines of force and a larger flow of the tongue at the leaves the other end and can move into the effective tax area,
complementary lower working gap G ₄ goes. If it is desired, however, the reluctance is directly proportional to the gap thickness and two double lobes (Fig. 7) equipped adjustment inversely proportional to the gap area and the 40 device also integral with the tongue 50 gear permeability of the material in the gap. When it's ready. An assembly of this type is the unified gap material is air, the permeability (shown in multiples in FIGS. 7 and 7a. The usual system of measurements) is equal to the unit. The Per- borrowed adjustment tabs 55Λ, SSB are selectively movable in the meability of non-magnetic materials, such as measuring trim positions. Both can be used individually or sing. Copper, aluminum, etc., is also equal to 45 together upwards and downwards or one upwards. The reluctance of a gap can, however, be adjusted independently or at the bottom, namely in the dependent on the force F i g passing through it. 7 flow shown in dashed and dash-dotted lines. Similar results follow from the bending way. In Fig. 7 a is the tongue 55 in the plan view of the tab 40 downwards. That means that the depicted. The bending line of the tongue in the fixed reluctance of the lower fixed gap G ₉ decreases 50 Gap runs along the dashed line 60, and and as the flow therethrough increases, the movement of the lobes 55,4 and SSB has none while the associated reluctance of the complementary noticeable effect on the swinging end of the tarry upper working gap G ₃ effectively enlarges the tongue.

is, since only a reduced flow of force the tongue in order to the in F i g. 7 facility shown at the most favorable

In the longitudinal direction from gap G ₃ to gap G ₂ , it is advisable to use one of the

can cross. both columns at 28 (corresponding to G ₁ or G ₂ ,

Due to the longitudinal flow in the tongue according to FIG. 2) initially a slightly lower reluctance

F i g. 4 leads to a modification of the power flow in give than the other, so that the greatest possible

a gap to an effect in opposite correction of the reluctance at the remaining gap

Sense at the complementary gap. 60 can be carried out in that both flaps

The same principles apply to the side 55A, 55.8 in the same direction from the gap with

protruding double tabs 51,4, 51B and the lower reluctance to be bent away. These

Corresponding adjacent column in the disk-shaped measure can be omitted and the adjustment effect

gene correction devices according to FIG. 6, but with enlarged if two disks are used

the significant difference that the devices 65 are spaced one above the other according to the in

according to FIG. 6 in contrast to the single flap 40 F i g. 8 are arranged, with a

in Fig. 2, which can only be adjusted so that in tongue 60 normal length up and down from

primarily only one or the other of the fixed magnetic disks 61 and 62 is flanked, the

I 173

lie one above the other and are separated from the associated pole pieces 22, 23 by corresponding non-magnetic spacer disks 28 W.

This arrangement ensures all adjustment options, as they are possible by bending all tabs 61Λ, 61 B and 62 Λ, 62 B in the same direction, ie all up or down, or as they result when the tabs 61A and 6IjB or when the flap 61Λ upward, downward 62.4, 61 B and 62 B is upwardly bent downwardly toward each other and the remaining tabs are bent in other ways, etc.

The effectiveness of the by using multiple disks according to F i g. 8 attainable settings is quite excellent, and in very small constructions of the kind described the overall quality or design of the transducers can be further improved by keeping the total flux provided by the magnets as constant as possible under the constraints imposed by the small size of these units is made. This is done in that, as shown in FIG. 5, each magnet 33 AX and 33BX is separated from the upper pole piece by a shallow air gap 65. This gap is preferably created by grinding the upper pole faces of each of the two magnets in order to create the gap 65, the thickness of which is as close as possible to about 5% of the thickness of the magnets. In order to mechanically stabilize this arrangement, the gaps are preferably filled with a non-magnetic spacer 66 made of brass or the like.

The reluctance introduced by column 65 increases the total reluctance of the magnetic circuit, and the reluctance changes on the columns therefore have only a small change in the total of the result of the force flow supplied to these magnets.

In Fig. 9 is a further modification of FIG Means for balancing the power flow in the form of an external magnetic correction element 70 with a large Permeability indicated, which has roughly the shape of an omega. This shunt can be attached to the nip end of the transducer so that the concave side of the arc 73 next to the fixed end of a tongue 74 of normal (i.e., non-extended) length. The attachment of the limb 70 can by spot welding one of its legs, e.g. B. 72, take place on one of the pole pieces. The starting material should be thin enough to allow bending and should have a high permeability exhibit.

In the device according to FIG. 9, the single adjustment member 70 is used to adjust both types of Gap upset. The shunt 70 becomes the clamping gaps and the as required Tip of the tongue bent towards or away from it, thereby both detuning the main flow at all Cleavage as well as the flow traversing the tongue in the longitudinal direction for adjustment in the foregoing Sense is brought. As in the earlier described embodiments, the power flow source is in the arrangement according to FIG. 9 viewed as essentially constant and for this purpose It is best to provide special column 65 (Fig. 5).

Claims (6)

Patent claims: 1. Electromechanical converter, especially for hearing aids, with two spaced apart Yokes arranged parallel to one another, the two air gaps lying at a mutual distance form, with a vibrating armature surrounded by an electromagnetic winding at a distance, one end of which is in the an air gap (clamping gap) with the interposition of a magnetic resistance is clamped against the yokes so that it is in the other air gap (working air gap) can oscillate, and with at least one extending parallel to the armature, perpendicular permanent magnet magnetized to the yoke disks, whose pole faces are used to generate a constant magnetic flux through both air gaps with one of the two yoke disks stand in magnetic contact, thereby gekennzeichnefc ^ that for in itself known influencing of the magnetic direct flux at least one of the clamping gap Correction element made of magnetizable material protruding into the adjacent air space between the yokes Material is arranged to partially bridge the magnetic resistance of the clamping gap in the direction of one or both yoke parts is bendable ^. 2. Converter according to claim 1, characterized in that the correction element of a is formed over the clamping gap protruding tabs of the oscillating armature itself. 3. Converter according to claim 1, characterized in that in immediate magnetic In contact with the oscillating armature, a plate-shaped correction element is provided in the clamping gap is, the two in opposite directions perpendicular to the plane of movement of the oscillating armature in the air space between the Has yokes protruding bendable correction flaps. 4. Converter according to claim 3, characterized in that on each side of the oscillating armature a plate-shaped correction element in direct contact with the anchor is provided. 5. Converter according to claim 4, characterized in that between a pole face of the permanent magnet and the associated yoke part is provided with a magnetic resistance of a predetermined size. 6. Converter according to claim 1 to 5, characterized in that as a correction element on the one yoke part attached bridging element made of flexible magnetizable material serves, the free end of which partially bridging the clamping gap in the direction of the other yoke is bendable. Considered publications:
German Patent Nos. 734 040, 890 992;
Swiss patents No. 217 613,
774, 311081; U.S. Patent Nos. 2245,511, 2511114. 1 sheet of drawings 409 628/214 6.64 © Bundesdruckerei Berlin