Patent Publication Number: US-9432774-B2

Title: Transducer with a bent armature

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of European Patent Application Serial No. 14163161.4, filed Apr. 2, 2014, and titled “A Transducer with a Bent Armature,” which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a transducer in which an armature is provided in the magnetic field of at least one magnet, and provided in a coil tunnel of a coil. 
     BACKGROUND OF THE INVENTION 
     Traditionally, transducer technology relies on the positioning of coil and magnet in one line to have a small and elongated transducer. 
     Bent armatures may be seen in e.g. EP2146521 and KR20140038232. 
     SUMMARY OF INVENTION 
     It is an object of embodiments of the invention to provide an improved transducer. 
     It is a further object of embodiments of the invention to provide a transducer which is more compact than traditional transducers. 
     Another object is to arrive at a transducer having a larger possible deflection of the membrane while keeping the form factor low. 
     According to a first aspect, the invention relates to a transducer comprising: 
     a housing defining a chamber, 
     a bent armature having at least a first leg and a second leg, the first leg having a first length, and a bent portion interconnecting the first and second legs, 
     a magnet assembly configured to provide a magnetic field in an air gap, and 
     a coil comprising a coil tunnel, 
     wherein the armature extends through the air gap and the coil tunnel and is fixed to the housing so that the second leg and at least a portion of the first leg, the portion extending from the bent portion and comprising at least 50% of the first length, are movable in relation to the housing. 
     The transducer may convert both ways between electrical power and sound, thus being applicable both as a receiver, such as a loudspeaker in a hearing aid, and as a microphone. Typically, the transducer is adapted to transform electrical energy into mechanical energy by movement of a leg of the U-shaped armature whereby sound waves may be created by movement of a membrane which may be coupled to the moving armature leg. 
     The transducer may be adapted to be fitted into any hearing aid such as a Behind-the-Ear (BTE) device, an In the Ear (ITE) device, a Receiver in the Canal (RIC) device, or any other hearing aid. In the context of the present invention, the term “hearing aid” shall be understood as an electromagnetic device which is adapted to amplify and modulate sound and to output this sound to a user, such as into the ear canal of a user. 
     The armature, coil and magnet assembly are provided, usually completely, in the housing. In the housing, one or more chambers may be defined. Often multiple chambers are defined by the inner housing walls and a membrane. Usually, two chambers are defined, one on either side of the membrane. Often, the armature and coil are provided in the same chamber. The magnet assembly may be provided in one chamber or may be divided into parts provided in different chambers. 
     The coil may comprise a number of windings defining the coil tunnel through which the armature extends. The coil may have a cross section, perpendicular to a longitudinal axis along the coil tunnel, which is circular, triangular, star-shaped, rectangular, rectangular with rounded corners, oval or any other shape. 
     The magnet assembly provides a magnetic field in an air gap through which the armature extends. The magnet assembly may be provided by a first and a second magnet portion positioned on opposite sides of the armature and defining an air gap between them. In one embodiment, the first and second magnet portions are separate magnets which provide the magnetic field. In an alternative embodiment, the first and second magnet portions are two parts of a single magnet, e.g. formed as a U-shaped magnet, or the magnet assembly may be formed by one or more magnets and a (for example U-shaped) yoke of a magnetically conducting material. 
     The armature is bent as opposed to straight or plane armatures which extend solely in one plane. The bent armature has a first and a second leg and an interconnecting, bent portion. A plane exists in which the first leg extends but wherein the second leg does not extend. The bent portion may be bent during production of the armature or may be initially provided in the desired shape. 
     Usually, the first and second legs are straight armature portions in a relaxed or non-operative state, even though any shape may in principle be used. 
     The armature may be made from any type of material, element and/or assembly able to guide or carry a magnetic flux. The armature may be electrically conducting or not. 
     The armature often has a flat cross section perpendicular to a longitudinal direction, such as when made from a piece of sheet material, so that the bending of the armature is well-defined (perpendicular to the width of the armature material). Usually, the width of the armature material is perpendicular to a plane in which both the first and second arms extend. 
     The bent portion may have any shape interconnecting the two legs. Thus, this portion may straight, U-shaped, S-shaped, V-shaped, L-shaped or the like, where the legs are attached to or extend from the bent portion in the respective, desired directions. 
     Naturally, the fastened or fixed portion of the first leg may be less than 50%, such as no more than 40%, such as no more than 30%, such as no more than 20%, such as no more than 10% of the first length. In a preferred embodiment, an end portion of the first leg is fastened so that virtually all of the first leg is movable in relation to the housing. 
     The legs may have the same or different lengths. In one embodiment, the second leg has a length of 90-110% of the first length. 
     Preferably, the second leg extends through the air gap. When the first leg is fastened to the housing, and when the moving force is applied to the armature by the magnetic field in the air gap, the largest translation or bending may be obtained when the second leg extends through the air gap. In this situation, the force applied may be used for bending/deforming both the second leg, the bent portion and the portion of the first leg. 
     In a particularly interesting embodiment, the armature is U-shaped, where the first and second legs are substantially parallel. In this embodiment, preferably, the second leg and the portion of the first leg are movable in a direction transverse to longitudinal directions of the first and second legs. 
     In the context of the present invention, three directions can be used to describe the bent or U-shaped armature. An X-direction which corresponds to the extent of the legs of the U-shaped armature. The dimension of the U-shaped armature in the X-direction may be designated “the length”. A Z-direction which defines a line extending through both the legs of the U-shaped armature. The dimension of the U-shaped armature in the Z-direction may be designated “the height”. A Y-direction which is perpendicular to both the Z- and the X-directions. The dimension of the U-shaped armature in the Y-direction may be designated “the width”. 
     Then, the coil tunnel and the air gap may extend substantially parallel to each other, such as in the X-direction, whereby a centre line of the coil extends in the X-direction. Then, one of the second leg and the portion of the first leg extends through the coil tunnel and the other of the second leg and the portion of the first leg extends through the air gap. The legs may extend in the X-direction, such as when the two legs are positioned at different positions along the Z-direction. 
     When the coil tunnel and the air gap extend substantially parallel to each other, the transducer may be embodied as a stacked transducer where the term “stacked transducer” should be understood as a transducer comprising a coil and a magnet assembly which are arranged above each other in the Z-direction so that one leg of the U-shaped armature extends through the coil tunnel and the other leg extends through the air gap when the U-shaped armature is arranged so that the legs extend in the X-direction. 
     It should however be understood, that the term stacked does not imply that the coil and the magnet assembly must be arranged in direct contact with each other. 
     By providing the transducer as a stacked transducer, the transducer is more compact in the X-direction than a traditional transducer, in which the coil and the magnet assembly are arranged on line in the X-direction. Thereby the transducer may be arranged in a smaller module allowing for a deeper fit and better fit-rate. 
     Additionally, a more compact transducer may facilitate arrangement of the transducer in a module being shaped substantially as a cylinder, which may further improve positioning of the hearing aid, e.g. inside the ear canal of a user. 
     To further facilitate a compact transducer, the magnet assembly and the coil may be arranged substantially above each other in the Z-direction, i.e. substantially perpendicularly to the first and second directions or the first and second legs. 
     Another interesting embodiment of the invention is a transducer having an L-shaped armature, wherein the first leg extends in a first direction through the coil tunnel and the second leg extends in a second direction through the air gap, wherein the coil tunnel and the air gap extend transverse to each other, such as with an angle of at least 10 degrees to each other, such as at least 20 degrees, such as at least 40 degrees, such as at least 50 degrees, such as at least 75 degrees, such as around 90 degrees. 
     The L-shaped armature may be positioned so that the first leg extends in the X-direction and so that the second leg extends in the Z-direction, whereby the legs may extend substantially perpendicular to each other. 
     In an alternative embodiment, L-shaped armature may be positioned so that the first leg extends in the Z-direction and so that the second leg extends in the X-direction, whereby the legs may still extend substantially perpendicular to each other, but in the opposite directions. 
     The part of the first leg may be attached or fixed to an attachment point of the housing either directly or via one or more attachment elements. In one embodiment, the fixed end portion is glued and/or welded and/or soldered to the housing. It should be understood that the term “attached to” may also cover embodiments were the fixed end point forms part of the housing so that the armature is formed integrally with the housing. 
     In general, the bent may extend in the Z-direction. Each leg may have a length being a distance from the bent portion to an end thereof, i.e. from the bent portion to e.g. a fixed end portion and from the bent portion to a free end portion, respectively. Each leg may extend freely from the bent portion towards the ends portions, whereby at least 50% of the length of each leg is movable in the housing. By moving freely should be understood, that the legs or parts thereof are at least rotatable in relation to the housing. When the first leg comprises a fixed end portion being attached to the housing, a portion of this leg first leg may move during use of the device as only the part of the first leg being closest to the housing is prevented from moving relative to the housing, while the remaining portion of the first leg may move relative to the housing. 
     The legs and the bent portion may be a monolithic element or may alternatively be made from several parts. In one embodiment, the transitions between the legs and the bent portion are rounded, whereas the transitions in another embodiment form sharp corners. The first and the second legs may be substantially straight. 
     The legs may be movable in a direction transverse to the first and second directions or longitudinal directions/axes thereof, such as in a direction being transverse to the X-direction. As the movement of the legs may be caused by the operation of the coil and the magnet assembly, the legs may be movable in a direction which is substantially along magnetic field lines of the magnetic field. Thus, the coil may introduce an electromagnetic field in the armature, which field will flow through the armature and thus also through the part positioned in the air gap, whereby at least this part will move in a direction being substantially along magnetic field lines of the magnet assembly. Thus, this part may be movable in a direction of the magnetic field lines, such as a direction which is substantially along the Z-direction. 
     As mentioned above, the magnet assembly may comprise a first magnet portion and a second magnet portion. The magnet portions may be positioned above each other in the Z-direction. To facilitate a compact layout of the transducer, a first part of the coil and the first magnet portion may be positioned in an area between the first and second legs, whereas a second part of the coil and the second magnet portion may be positioned outside the area, thus forming a layered transducer in the Z-direction. 
     The first part of the coil should be understood as the part of the coil being positioned at one side of the armature portion extending in the coil tunnel, whereas the second part of the coil should be understood as the part of the coil being positioned at the other side of the armature portion. As an example, the first part of the coil may be positioned above the armature portion in the Z-direction, whereas the second part of the coil may be positioned below the armature portion in the Z-direction. 
     The transducer may further comprise a membrane which may be operationally attached to the armature, such as the second leg, such that movement of the armature is transferred to the membrane. It will be appreciated that movement of the membrane causes sound waves to be generated. In one embodiment, the second leg is operationally attached to the membrane by means of a membrane connecting member, such as a drive pin. Alternatively, the membrane may itself be attached to the second leg. Further alternatively, the armature may itself constitute the membrane or a part thereof 
     The membrane may comprise a plastic material, such as a polymer, or alternatively a metal material such as aluminium, nickel, stainless steel, or any other similar material. The membrane may divide the chamber into two chambers as is described above. 
     The housing may comprise a sound opening. In embodiments, where the transducer is used as a receiver, this opening is a sound outlet. The membrane may be positioned between the sound opening and other elements of the transducer, such as the armature, the coil and/or the attachment point. The membrane may be positioned substantially above at least a part of the magnet assembly, e.g. the first magnet portion, whereby the membrane forms part of the stacked magnet assembly and coil, as this may add to the compactness of the transducer. In fact, part of the magnet assembly may be positioned on one side of the membrane and another part on the other side of the membrane. 
     The compact layout of the transducer may be improved by arranging a suspension attached to a fixation point in the housing. The suspension may extend in the housing, such as in the X-direction, and may be attached to the coil and/or the magnet assembly. Thus, the suspension may be arranged to at least partly support the magnet assembly and/or the coil. The suspension may be positioned between the membrane and the attachment point in the Z-direction. The suspension may extend into a space between the first and second legs. 
     The armature may comprise a first and a second support portion configured for supporting the armature in and fixing the armature to the housing. In one embodiment, the armature may be attached to the housing by these support portions. The support portions may be attached to the first leg. The first and second support portions may be attached to the housing and may extend parallel to the first leg, whereby the first leg and the two support portions together form an E, which may extend in the Y-direction. 
     The housing may comprise a top wall, a bottom wall, and one or more side walls extending between the top wall and the bottom wall. The top wall may form part of the outer surface of the housing and may be positioned highest in the Z-direction, whereas the bottom wall, also forming part of the outer surface, may be positioned lowest in the Z-direction. The side wall(s) may form the outer surfaces being positioned at each end of the housing in the X-direction. 
     The distance between the top wall and the bottom wall may be in the range of 0.5-5.0 mm, such as in the range of 1.0-3.0 mm, such as in the range of 1.5-2.5 mm. The distance between two opposed side walls or side wall portions may be in the range of 2.0-5.0 mm, such as in the range of 2.5-4.0 mm. 
     The width of the housing may be defined by two additional side walls or side wall portions being positioned at each end of the housing in the Y-direction. The distance between the two additional side walls may be in the range of 2.0-5.0 mm, such as in the range of 2.5-4.0 mm. 
     The chamber may have a volume in the range of 10-20 mm 3 , such as in the range of 12-18 mm 3 . 
     The armature may be arranged in the housing so that the distance between the attachment point and the fixation point is at least 10 percent of the distance between the top wall and the bottom wall in the Z-direction. 
     In one embodiment, the shape of the transducer in the X-Y plane is substantially rectangular, or even quadratic, whereas it in an alternative embodiment is substantially circular, thereby providing a very compact transducer. 
     It should be understood, that a skilled person would readily recognise that any feature described in combination with the first aspect of the invention could also be combined with the second aspect of the invention, and vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be further described with reference to the drawings, in which: 
         FIG. 1  schematically illustrates a first embodiment of a transducer according to the invention, 
         FIG. 2  schematically illustrates a second embodiment of a transducer according to the invention, 
         FIG. 3  is a 3D illustration of the first embodiment of the transducer schematically illustrated in  FIG. 1 , 
         FIG. 4  is a 3D illustration of an alternative embodiment of a transducer according to the invention, 
         FIG. 5  illustrates an L-shaped armature, and 
         FIGS. 6, 7, and 8  illustrate different views of a further embodiment of a transducer according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       FIG. 1  illustrates an embodiment of a transducer  1 . The transducer  1  comprises a housing  2  defining a chamber  3 , and a U-shaped armature  4  with a first leg  5  and a second leg  6 . Furthermore, the transducer comprises a magnet assembly  7  for providing a magnetic field in an air gap  8 , and a coil  9  comprising a coil tunnel  10 . The coil tunnel  10  and the air gap  8  extend substantially parallel to each other, and the first leg  5  extends in a first direction through the coil tunnel  10  and the second leg  6  extends in a second direction through the air gap  8 . 
     The first and second directions both extend along the X-direction illustrated by the arrow X. The X-direction corresponds to the extent of the legs  5 ,  6  of the U-shaped armature  4 . The Z-direction which is illustrated by the arrow Z is parallel to a line extending through both the legs of the U-shaped armature. The Y-direction is perpendicular to both the Z- and the X-directions. 
     The transducer  1  is adapted to transform electrical energy into mechanical energy by movement of the second leg  6  of the U-shaped armature  4  whereby sound waves are created by movement of the membrane  11  which is coupled to the armature  4 . A soft suspension element  11 ′ is provided allowing the membrane  11  to move in relation to the housing while preventing air flow from the upper side of the membrane  11  to the lower side thereof. Naturally, a vent may be provided allowing DC pressure equalization between the space below the membrane and that above the membrane. 
     The magnet assembly  7  is embodied as a first magnet portion  7   a  and a second magnet portion  7   b  positioned on opposite sides of the second leg  6 . 
     The coil  9  is formed as a tubular element and comprises a number of windings defining the coil tunnel through which the first leg  5  extends. A first part of the coil  9   a  and the first magnet portion  7   a  is positioned in the area between the first leg  5  and second leg  6 , whereas a second part of the coil  9   b  and the second magnet portion  7   b  is positioned outside the area, thus forming a stacked/layered transducer in the Z-direction. 
     The U-shaped armature  4  is formed so that both legs  5 ,  6  are attached to a bent portion  12  which forms the bottom of the U. The bent portion  12  extends in the Z-direction. 
     The armature  4  has a fixed end portion  13  where an end portion of the first leg  5  is attached to an attachment point of the housing. At the opposite end, the U-shaped armature  4  has an end portion  14  which may move freely in the chamber  3 . The first leg  5  comprises the fixed end portion  13  and the second leg  6  comprises the free end portion  14 . Alternatively, the first leg  5  may be attached along a portion thereof from the end portion toward the bent portion  12 , as long as the bent portion  12  and a portion of the first leg  5  closer to the bent portion  12  is movable in relation to the attachment point. 
     The housing  2  comprises a sound opening  15  for outlet of sound. In general, the direction of sound may be reversed so that the present transducer  1  acts as a sound detector or microphone. 
     A suspension  16  is attached to a fixation point of the housing  2 , extends in the housing in the X-direction and is attached to the coil  9  and the magnet assembly  7  in order to at least partly support the magnet assembly  7  and the coil  9 . Alternatively, the coil  9  may be attached to the housing or even to the first leg  5 . 
     It is seen that the membrane  11  extends in the air gap  8 , so that the magnet portion  7   b  is positioned in the front chamber (with the sound opening) and the magnet portion  7   a  in the back chamber (the chamber on the opposite side of the membrane  11 ). 
     The housing  2  comprises a top wall  17 , a bottom wall  18 , and one or more side walls of which two opposite side wall portions  19 ,  20  are illustrated which extend between the top wall  17  and the bottom wall  18 . The top wall  17  and the bottom wall  18  form part of the outer surface of the housing and are positioned highest and lowest in the Z-direction. The two side wall portions  19 ,  20  also form part of the outer surfaces and are positioned at each end of the housing  2  in the X-direction. The width of the housing  2  is defined by two additional side wall portions (not shown) being positioned at each end of the housing in the Y-direction. 
       FIG. 2  illustrates a second embodiment of a transducer  101  according to the invention. The transducer  101  is similar to the transducer  1  illustrated in  FIG. 1 . However, the membrane  111  is positioned above the second magnet portion  107   b  and is operationally attached to the second leg  106  a by a drive pin  121 . 
     Furthermore, a second suspension  122  is attached to a second fixation point of the housing  102  and extends in the housing in the X-direction. The second suspension  122  is attached to the magnet assembly  107  to thereby at least partly support the magnet assembly  107 . 
       FIG. 3  is a 3D illustration of the first embodiment of the transducer  1  schematically illustrated in  FIG. 1 . 
       FIG. 4  is a 3D illustration of an alternative embodiment of parts of a transducer  201  according to the invention. The transducer  201  comprises a U-shaped armature  204  which comprises a first support portion  223  (not shown) and a second support portion  224  configured for supporting the armature  204  in the housing  202 . The armature  204  is attached to the housing  202  by these support portions  223 ,  224  in the same manner as typical E-shaped armatures. The first and second support portions  223 ,  224  are attached to the housing  202  along their length in the X-direction, and extend parallel to the first leg  205 , whereby the first leg  205  and the two support portions  223 ,  224  together form an E which extends in the Y-direction. The first leg  205  thus is attached to the housing at an end thereof 
       FIG. 5  illustrates an L-shaped armature  304  for use in another embodiment of a transducer according to the invention. This L-shaped armature may be used in a transducer, wherein the coil tunnel and the air gap extend transverse to each other. The L-shaped armature  304  may be positioned so that the first leg  305  extends in the X-direction and so that the second leg  306  extends in the Z-direction, whereby the legs extend substantially perpendicular to each other. 
     The first leg  305  may be arranged so that it extends in a first direction through the air gap and the second leg  306  may be arranged to that it extends in a second direction through the coil tunnel. The membrane may thus be attached to the leg  306 , as the magnet assembly will make the leg  305  move in the Z direction. 
       FIGS. 6, 7, and 8  illustrate different views of a further embodiment of a transducer  401  having a substantially circular shape in the X-Y plane. 
       FIG. 6  illustrates the transducer  401  comprising a circular housing  402 . The housing comprises a circular top wall  417  and a circular bottom wall  418  (see  FIG. 7 ). The sidewall  419  is substantially tube shaped. 
       FIG. 7  is a cross-sectional view through the transducer  401 . The layout of the transducer  401  is similar to the transducer  1  of  FIG. 1  except for the circular shape. The first armature leg  405  extends between the first and second parts of the coil  409   a ,  409   b . The second armature leg  406  and the membrane  411  extend between first and second magnet portions  407   a ,  407   b.    
       FIG. 8  illustrates a U-shaped armature  404  for use in the transducer  401 . The armature comprises a first support portion  423  and a second support portion  424  configured for supporting the armature  404  in the housing  402 . The armature  404  is attached to the housing  402  by these support portions  423 ,  424  (see  FIG. 6 ).