Patent Publication Number: US-9420379-B2

Title: Performance enhancing apparatus of balanced armature transducer

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed on Jul. 2, 2013 in the Korean Intellectual Property Office and assigned Serial No. 10-2013-0077071, the entire disclosure of which is hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a balanced armature transducer. More particularly, the present disclosure relates to an improved balanced armature transducer that uses little space and that can improve sound performance using limited elements. 
     BACKGROUND 
     With continuing advances in technology, electronic devices are formed having smaller sizes, such that they can be carried by a user while supporting a specific user function, and have been spotlighted in many industrial and living fields. Nowadays, electronic devices supporting various advanced user functions are available. 
     For example, a mobile terminal is an electronic device that has an audio reproduction function and is able to output various audio signals according to a user request. A Moving Picture Experts Group layer-3 (MP3) player, a Personal Digital Assistant (PDA), and a laptop computer are other electronic devices that are available with a sound output function of a radio receiver and an MP3 player. 
     An earphone is provided as a typical accessory to an electronic device having such a sound output function. Using the earphone, a user can obtain audio information through the electronic device without disturbance from external noise, such as from a surrounding environment. Further, the earphone enables the user to enjoy desired audio contents, assists the user to clearly listen and understand audio contents, and enables the user to receive clearer sound than that transferred through the air. Such an earphone can be used when studying, performing work requiring concentration, or when wishing to escape from noise in a noisy environment. 
     Earphones of the related art use a moving coil speaker having a frequency response curve characterized by a sound quality in which intermediate and low frequency bands are reinforced. Further, in another earphone of the related art, a balanced armature speaker characterized by a frequency response curve having a sound quality in which a high band is reinforced may be used. 
       FIG. 1A  is a perspective view illustrating a balanced armature transducer according to the related art, and  FIG. 1B  is a cross-sectional view illustrating a balanced armature transducer according to the related art. 
     Referring to  FIGS. 1A and 1B , in a balanced armature transducer  10  according to the related art, an armature  11  is formed in a C shape having an upper surface located between magnets  17  and  18 , and between a coil  14 , and having a lower surface  12  fixed as a bottom. Additionally, the magnets  17  and  18  are supported by a yoke  19  and the transducer  10  is partially covered by a frame  20  having a diagraph  16  disposed above. When a current is applied to the coil  14 , the upper surface of the armature  11  vibrates and the vibration of the armature  11  is transferred to the diaphragm  16  through a connecting rod  15  connected to the armature  11 . Accordingly, the diaphragm  16  vibrates and generates sound. 
     A balanced armature transducer according to the related art is formed in a C shape so as to fix the armature  11  and to fix the lower surface  12  thereof as the bottom. As such, the lower surface  12  is unrelated to the production of sound in that it is only the armature  11  that actually vibrates, while the lower surface  12  only performs a function of fixing the armature  11 . However, the lower surface  12  occupies a large volume as compared with the importance of its function and thus a limitation exists in reducing an entire size and volume of the balanced armature transducer  10  and a mounting ability is thus deteriorated. 
     Further, in order to improve a performance of a balanced armature transducer, when a size of the magnets  17  and  18  or a size of the coil  14  is increased, a performance of the balanced armature transducer can be secured. However, a large size of the magnets  17  and  18  or of the coil  14  also causes difficulty when attempting to reduce a size and volume of the balanced armature transducer  10 . 
     Therefore, a need exists for an improved apparatus and method for enhancing a mounting ability of the balanced armature transducer using limited space and limited elements and for improving a sound output function. 
     The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure. 
     SUMMARY 
     Aspects of the present disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide a method and apparatus for enhancing a volume of a balanced armature transducer that can support an improved sound output while maximizing space use in a structure of the balanced armature transducer. 
     Another aspect of the present disclosure is to provide a method and apparatus for enhancing a volume of a balanced armature transducer that can secure a sound volume feeling when listening to sound by enhancing the efficiency of sound pressure release in a low frequency band. 
     In accordance with an aspect of the present disclosure, a balanced armature transducer formed with components housed within a frame is provided. The balanced armature transducer includes a pair of magnets separated by a gap to form a Direct Current (DC) magnetic field, and an armature having one end positioned between the separated magnets and having another end curved upward and fixed to an upper portion of the frame. 
     In accordance with another aspect of the present disclosure, a balanced armature transducer formed with components housed within a frame is provided. The balanced armature transducer includes a pair of magnets separated by a gap to form a DC magnetic field, an armature having one end positioned between the separated magnets and having another end curved upward and fixed to an upper portion of the frame and in which a surface opposite to the magnet is formed in an uneven structure, a coil wound around a portion of the armature the coil configured to create an Alternating Current (AC) magnetic field between the armature and the magnets by generating a magnetic flux to the armature when a signal current is applied, a diaphragm configured to radiate sound, and a connecting rod connected between the armature and the diaphragm, wherein the diaphragm is further configured to vibrate in correlation with displacement of the connecting rod, the connecting rod being displaced as the armature is deformed when the AC magnetic field is overlapped with the DC magnetic field. 
     In accordance with another aspect of the present disclosure, a balanced armature transducer is provided. The balanced armature transducer includes a frame, a pair of magnets separated by a gap to form a Direct Current (DC) magnetic field, and an armature having a first end positioned between the separated magnets, the first end including a first surface and a second surface opposite the first surface, each of the first surface and the second surface having a length dimension and a width dimension, wherein at least one of the first surface and the second surface has an increased surface area as compared with a plane surface of the same dimensions. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a perspective view illustrating a balanced armature transducer according to the related art; 
         FIG. 1B  is a cross-sectional view illustrating a balanced armature transducer according to the related art; 
         FIG. 2  is a perspective view illustrating an external appearance of a balanced armature transducer according to an embodiment of the present disclosure; 
         FIGS. 3A, 3B, and 3C  are cross-sectional views illustrating a balanced armature transducer, such as the balanced armature transducer of  FIG. 2 , according to an embodiment of the present disclosure; 
         FIG. 4  is a cross-sectional view illustrating a balanced armature transducer according to another embodiment of the present disclosure; 
         FIG. 5  is a perspective view illustrating a balanced armature transducer, such as the balanced armature transducer of  FIG. 2 , according to an embodiment of the present disclosure; 
         FIG. 6  is an exploded perspective view illustrating a balanced armature transducer, such as the balanced armature transducer of  FIG. 2 , according to an embodiment of the present disclosure; 
         FIGS. 7A, 7B, 7C, 7D, and 7E  are cross-sectional views and partial side cross-sectional views illustrating balanced armature transducers of various forms according to the related art and according to an embodiment of the present disclosure; and 
         FIG. 8  illustrates a graph representing a frequency characteristic of sound radiated by each balanced armature transducer of  FIGS. 7A to 7E  and a table of a sound pressure average according to an embodiment of the present disclosure. 
     
    
    
     The same reference numerals are used to represent the same elements throughout the drawings. 
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     A balanced armature transducer is used for an audio device such as a miniature speaker adapted for use as a hearing aid or an earphone. In operation, the earphone or the hearing aid transfers sound by increasing a sound pressure at the inside of the ear. When warn by a user, an open type earphone does not entirely contact with the user&#39;s ear, such that the space within the ear is open to the outside. Thus, the sound pressure within the ear is easily diminished and a low frequency characteristic is deteriorated. On the other hand, a closed type earphone has close contact with the inside of the user&#39;s ear, such that it is much more difficult for an external sound to be heard by the user. Thus, the closed type earphone has merit in that it is better at preventing external interference. Furthermore, the sound pressure is more easily maintained such that the closed type earphone has an excellent characteristic in a low frequency band. 
     Such an earphone is formed with a plurality of constituent elements that each has a sensitive influence on sound transfer. Further, while it may be desired to increase the size of a particular constituent element to improve its performance, the size of each constituent element is limited due to the small size of the inside of an ear. 
     A balanced armature transducer according to an embodiment of the present disclosure enlarges a surface area having an influence on a magnetic force of a magnet by forming a cross-section of an armature opposite to the magnet to have an uneven structure and thus enhances a displacement of an armature rod without increasing a size of the armature, thereby enhancing efficiency of sound pressure release. Accordingly, by securing a sound volume feeling when listening to sound in a low sound band, a performance of the balanced armature transducer can be enhanced. 
     Further, a balanced armature transducer according to an embodiment of the present disclosure omits a structure disposed only to fix an armature regardless of emission of a sound pressure and has an armature structure modified not to increase a volume of the balanced armature transducer and thus can enhance space efficiency while stably fixing the armature. 
     Hereinafter, a structure of a balanced armature transducer according to an embodiment of the present disclosure is described with reference to  FIGS. 2 to 6 . 
       FIG. 2  is a perspective view illustrating an external appearance of a balanced armature transducer according to an embodiment of the present disclosure,  FIGS. 3A to 3C  are cross-sectional views illustrating a balanced armature transducer, such as the balanced armature transducer of  FIG. 2 , according to an embodiment of the present disclosure,  FIG. 4  is a cross-sectional view illustrating a balanced armature transducer according to another embodiment of the present disclosure,  FIG. 5  is a perspective view illustrating a balanced armature transducer, such as the balanced armature transducer of  FIG. 2 , according to an embodiment of the present disclosure, and  FIG. 6  is an exploded perspective view illustrating a balanced armature transducer, such as the balanced armature transducer of  FIG. 2 , according to an embodiment of the present disclosure. 
     Referring to  FIGS. 2 to 6 , a balanced armature transducer  200  receives a sound signal through a sound signal line (not shown) connected from the outside and outputs sound to a radiation port  230 . The balanced armature transducer  200  may be formed in a closed type frame that exposes the radiation port  230 . 
     As shown in  FIGS. 3A to 3C and 4 , the radiation port  230  may be formed having a structure that externally protrudes from one side surface of a closed type frame, a structure in which one side surface (e.g., an upper side surface) of a closed type frame is open, or a structure in which one side surface and an upper side surface of a circumference of a closed type frame are open, as shown in  FIG. 4 . That is, a structure of the radiation port  230  may have any of various forms and those shown in the accompanying drawings are merely for example and not to be construed as limiting. 
     Referring to the cross-sectional view of a balanced armature transducer of  FIG. 3A , the balanced armature transducer  200  according to an embodiment of the present disclosure may include a frame  210 , a pair of magnets  310  and  320 , a yoke plate  330 , an armature  340 , a coil  350 , a connecting rod  360 , and a diaphragm  370 . 
     The frame  210  performs a function of supporting the diaphragm  370 . In an embodiment, the frame  210  is formed with an internal frame and an external frame, and may have an external shape of a cuboid. Of course, a structure of the frame  210  is not limited thereto but may be any of various shapes. Also, the frame  210  may be made of a hard material such as aluminum or a hard resin. 
     The pair of magnets  310  and  320  are separated by a gap to form a Direct Current (DC) magnetic field. The pair of magnets  310  and  320  may be considered as, for example, an upper magnet  310  and a lower magnet  320 , a top magnet  310  and a bottom magnet  320 , or simply a first magnet  310  and a second magnet  320 . 
     In a lower end portion of the lower magnet  320 , the yoke plate  330  is provided. The yoke plate  330  may be provided to form a closed circuit including the magnets  310  and  320 . That is, within an air gap, a substantially constant static magnetic field occurs from the upper magnet  310  and the lower magnet  320 . A return path of such a static magnetic field is limited by the yoke plate  330 . The yoke plate  330  may be made of a material having a high magnetic permeability and thus having a high magnetic property. 
     One end  342  of the armature  340  is positioned between the pair of magnets  310  and  320  that are separated by a gap. The other end  344 , which is located in an opposite direction from the one end  342 , has a bent or curved form in that it is formed to bend or curve upward to be fixed to an upper portion of the frame  210 . A bending structure of the other end  344  may have a hook form as shown in  FIG. 3A , a U-shaped streamline shape  345  in which a bent portion is laid to the side as shown in  FIG. 3B , or a shape in which a bent portion is formed in a  -shaped form  346  as shown in  FIG. 3C . Of course, it is to be understood that the other end  344  may adapt any structure that can be fixed to an upper portion of the frame  210 . 
     As explained above, an armature of the related art is formed having a C type in order to fix the armature. However, when formed having a C type, the armature not only occupies an additional volume, the additional volume is unnecessary as it does not assist in a function of emitting a sound pressure. On the other hand, a balanced armature transducer according to an embodiment of the present disclosure forms one end  342  having a bent or curved structure and fixes the one end  342  to the frame  210 , thereby lowering an overall height of the balanced armature transducer. Accordingly, in the present disclosure, while stably fixing an armature, the space occupied by the armature can be effectively reduced. 
     The armature  340  may be formed using any of various methods. For example, the armature  340  may be formed by stamping out a metal strip. In that case, one end of the metal stamp may be easily bent. The armature  340  may be formed to include a known magnetic material such as a permalloy (or iron-nickel magnetic alloy) and an iron-silicone material such as a silicon steel or other materials. Also, the armature  340  may be made of a material having a high magnetic permeability and thus having a high magnetic property. 
     The armature  340  is positioned between the pair of separated magnets  310  and  320  may include an air gap between itself and either or both of the magnets  310  and  320 . 
     The coil  350  is wound at a circumference of a portion of the armature  340 . With this arrangement, when a driving signal such as a current signal is applied, the coil  350  generates a magnetic flux to the armature  340  to enable an Alternating Current (AC) magnetic field to be formed between the armature  340  and the magnets  310  and  320 . 
     More specifically, when a driving signal is not applied to the coil  350 , the armature  340  is positioned at an intermediate location in the air gap between the upper magnet  310  and the lower magnet  320 , and a magnetic force operating from the magnets  310  and  320  on the armature  340  is balanced. That is, the one end  342  of the armature  340  is formed to freely move under a magnetic force, and in a state in which a driving signal is not applied through the coil  350 , the one end  342  is positioned at a substantially equal distance from the upper magnet  310  and the lower magnet  320 . 
     The driving signal is a signal current applied to the coil  350  and may be applied to the coil  350  wound at a circumference of a portion of the armature  340 . The driving signal increases an attractive force between the armature  340  and one of the magnets  310  and  320 , depending on the polarity of the driving signal, thereby enabling the armature  340  to displace toward a corresponding magnet. Here, the armature  340  has sufficient rigidity such that, even as the armature  340  is so biased toward the magnet, the armature  340  is not stuck to the magnet. 
     More particularly, in the armature  340  according to an embodiment of the present disclosure, a surface area of the one end  342 , located between the magnets  310  and  320 , is formed having a structure that is greater than that of a flat plane. 
     More specifically, a surface of the one end  342 , located between the magnets  310  and  320 , is formed having an uneven structure and thus a surface area that is affected by the magnetic force of the magnets  310  and  320  may be enlarged. The uneven structure may be formed having a surface area wider than that of a flat surface in at least one form of a sine wave, quadrangle, polygon, and hemisphere. 
     As a surface area of the armature  342  located between the magnets  310  and  320  is enlarged, an attractive force generated in the armature  340  increases. Therefore, a displacement of the connecting rod  360  connected to the armature  340  increases which causes an increase in the vibration of the diaphragm  370  and enhances the sound quality. 
     That is, in the present disclosure, by forming an uneven structure at one end  342  of an armature located between the magnets  310  and  320  so that the magnetic force has a greater influence on the armature  340 , a sound performance can be enhanced without an increase in the size of a component. 
     The diaphragm  370  may be fixedly attached or otherwise coupled to the frame  210  and may be physically connected to the armature  340  through the connecting rod  360 . The connecting rod  360  may be made of a non-magnetic material having rigidity. 
     When a signal current is applied to the coil  350 , an AC magnetic field formed between the armature  340  and the magnets  310  and  320  is overlapped with a DC magnetic field formed between the magnets  310  and  320  by a magnetic flux generating in the armature  340 . In this case, the armature  340  is deformed in a vertical direction. Accordingly, the connecting rod  360  connected to the armature  340  displaces in a vertical direction. As a displacement of the connecting rod  360  is transferred to the diaphragm  370 , connected and fixed to an upper end portion thereof, the diaphragm  370  vibrates, and thus sound may occur. Sound generated in this way is emitted to the outside of the balanced armature transducer through the radiation port  230  and is thus finally transferred to the user&#39;s ear. 
     Under substantially the same conditions, a performance of components of embodiments of the present disclosure were compared with that of the related art shown in  FIGS. 1A and 1B . Two cases of a balanced armature transducer having one end  342  as an uneven portion of the armature  340  and the other end  344  as a fixing portion were analyzed. The results showed an improvement of 7.6 dB in the 200 Hz-4 kHz frequency band and a decrease of 4.8 dB in the 4 kHz-20 kHz frequency band. Accordingly, sound output by a balanced armature transducer of the present disclosure is advantageous in securing a performance of a low frequency band because a first resonant point F 0  is lower than that of the related art. 
     It is also observed that, as a width of the armature  340  is reduced, the first resonant point F 0  moves upward and thus a sound performance is changed. Thereby, a width of the armature  340  can be adjusted according to a desired sound pressure sensitivity. Therefore, by adjusting a width of the armature  340 , a balanced armature transducer having a desired performance can be produced. 
       FIGS. 7A to 7E  are cross-sectional views and partial side cross-sectional views illustrating balanced armature transducers of various forms according to the related art and to an embodiment of the present disclosure, and  FIG. 8  illustrates a graph representing a frequency characteristic of sound radiated by each balanced armature transducer of  FIGS. 7A to 7E  and a table of a sound pressure average according to an embodiment of the present disclosure. 
     Referring to  FIGS. 7A to 7E ,  FIG. 7A  illustrates a cross-section and a partial side cross-section of a balanced armature transducer of the related art as shown above with reference to  FIGS. 1A and 1B , and  FIGS. 7B to 7E  illustrate cross-sections and partial side cross-sections of balanced armature transducers according to embodiments of the present disclosure. The width of armature  340  narrows as the drawings advance from  FIG. 7B  to  FIG. 7E . Also,  FIG. 7B  illustrates a yoke plate  330  having substantially flat sides as the yoke plate  330  approaches the frame  210 , while  FIGS. 7C to 7E  illustrate a yoke plate  330  having sides that bend or flare out as the yoke plate approaches the frame  210 . These different configurations of the yoke plate  330  are provided as examples only and should not be construed as limiting. For example, the configuration of the yoke plate  330  may be altered to accommodate a manufacturing scheme. Moreover, simply because an armature  340  having one end  342  with a certain width or configuration is illustrated in conjunction with a certain yoke plate  330 , it should be understood that this is simply for illustration and should not be construed as limiting the various configurations and combinations of yoke plates  330  and armatures  340 . 
     Referring to  FIGS. 7A to 7E, and 8 , as a width of the armature  340  reduces, it can be seen that a first resonant point F 0  moves upward. Therefore, as a width of the armature  340  is increase, sound pressure sensitivity of a low frequency band may increase. In this way, a balanced armature transducer according to an embodiment of the present disclosure can adjust sound pressure sensitivity of a low frequency band by simply adjusting a width of an armature without using an electric circuit. 
     Further, it can be seen that a sound pressure of sound emitted by a balanced armature transducer according to an embodiment of the present disclosure increased as compared with that of sound emitted by the balanced armature transducer of the related art. 
     An embodiment of the present disclosure provides an improved balanced armature transducer such as a speaker and a microphone to use for a hearing aid, a speaker wearing in an ear, an earphone, a bone-conduction audio device, a cellular phone, other different phones, an earpiece, a radio receiver, a portable music player, and other entertainment devices. 
     As described above, in a volume enhancing apparatus of a balanced armature transducer according to the present disclosure, by fixing an armature to a frame by changing a structure of the armature, while the armature is stably fixed, the space occupied by components can be effectively reduced. 
     Further, by forming a cross-section of an armature located between a pair of magnets to have an uneven structure, a surface area affected by a magnetic force of the magnets is enlarged and a displacement of an armature rod increases such that an efficiency of sound pressure release can be enhanced. More particularly, by enhancing the efficiency of sound pressure release in a low frequency sound band, when listening to sound, a volume feeling can be secured. 
     While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.