Patent Publication Number: US-2015076629-A1

Title: Microphone

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2013-0111703 filed on Sep. 17, 2013, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a microphone using a piezoelectric element, and more particularly, to a microphone, a sensitivity of which to sound waves is adjustable. 
     A microphone is a device converting sound waves into electrical signals. A microphone includes a thin film member receiving sound waves and a converting unit converting vibrations of the thin film member into electrical signals. 
     Microphones may be divided into capacitive type microphones and piezoelectric type microphones, depending on the method of sensing sound waves utilized thereby. The former converts sound waves into electrical signals through changes in capacitance, due to the vibrations of the thin film member, and the latter senses sound waves by electrical signals of a piezoelectric element generated by the vibrations of the thin film member. 
     Here, since the piezoelectric type microphone has a structure in which the piezoelectric element is formed on one surface of the thin film member, it may be relatively simply manufactured and has a relatively simple structure, such that it is advantageous for miniaturization. However, the piezoelectric element is formed on one surface of the thin film member as described above to hinder vibrations or warpage deformation of the thin film member, thereby decreasing sensitivity thereof to sound waves. 
     Therefore, development of a microphone capable of improving sensitivity to sound waves in spite of having a piezoelectric type structure has been demanded. For reference, as the related art as sociated with the present disclosure, there are provided Patent Documents 1 and 2. 
     RELATED ART DOCUMENT 
     
         
         (Patent Document 1) U.S. Pat. No. 5,856,956 A1 
         (Patent Document 2) U.S. Pat. No. 7,615,912 B2 
       
    
     SUMMARY 
     An aspect of the present disclosure may provide a piezoelectric type microphone capable of adjusting and improving sensitivity to sound waves. 
     According to an aspect of the present disclosure, a microphone may include: a thin film member including leg members extended in a direction not in parallel with a vibration direction; first supports supporting first points of the leg members, respectively; and a piezoelectric member connected to second points of the leg members and converting vibrations of the thin film member into electrical signals. 
     The thin film member may be more adjacent to the first point than the second point. 
     A plurality of leg members may be provided and may be disposed in a rotation symmetrical form based on the center of the thin film member. 
     The piezoelectric member may include: a first piezoelectric member extended from one end of the leg member toward a fixed body; and a second piezoelectric member extended from the other end of the leg member toward the fixed body. 
     A distance from a connection point between the first piezoelectric member and the leg member to the first point may be different from a distance from a connection point between the second piezoelectric member and the leg member to the second point. 
     The piezoelectric member may be disposed so that both ends thereof are connected to a fixed body based on the leg member. 
     The piezoelectric member may be disposed so that both ends thereof are connected to the first support based on the leg member. 
     The piezoelectric member may have a curved shape. 
     The first support may have a curved shape. 
     The piezoelectric member may include: a first piezoelectric member connected to the second point on the leg member; and a second piezoelectric member connected to a third point on the leg member. 
     A distance from the first point to the second point may be different from a distance from a connection point between the leg member and the thin film member to the first point. 
     According to another aspect of the present disclosure, a microphone may include: a thin film member including a plurality of leg members extended in a direction not in parallel with a vibration direction; first supports supporting first points of the plurality of leg members, respectively; second supports connecting the first supports and a fixed body to each other, respectively; and a piezoelectric member connected to second points of the leg members and the second supports and converting vibrations of the thin film member into electrical signals. 
     The thin film member may have a circular shape, and the first support may have a ring shape. 
     The piezoelectric member may have a ring shape in which it encloses the outside of the thin film member. 
     The piezoelectric member may include: a first piezoelectric member connecting the second point on the leg member and the second support to each other; and a second piezoelectric member connecting a third point on the leg member and the second support to each other. 
     The first and second piezoelectric members may have a curved shape, and the first piezoelectric member may have a radius of curvature larger than that of the second piezoelectric member. 
     A distance from the first point to the second point may be equal to or different from a distance from a connection point between the leg member and the thin film member to the first point. 
     According to another aspect of the present disclosure, a microphone may include: a thin film member connected to a fixed body by at least two leg members; and a piezoelectric member connected to the fixed body and the leg members and converting vibrations of the thin film member into electrical signals. 
     The thin film member may have a circular or oval shape, and the piezoelectric member may have a curved shape in which it is extended lengthwise along a circumference of the thin film member. 
     Both ends of the piezoelectric member may be disposed to be connected to different leg members, respectively. 
     The piezoelectric member may include: a first piezoelectric member connected to a first point on the leg member; and a second piezoelectric member connected to a second point on the leg member. 
     The microphone may further include a protrusion member extended from the fixed body and connected to the piezoelectric member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a view showing a configuration of a microphone according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is an enlarged view of part A shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along line B-B of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view taken along line B-B for describing an operational principle of the microphone shown in  FIG. 1 ; 
         FIGS. 5 through 10  are plan views another form of the microphone shown in  FIG. 1 ; 
         FIG. 11  is a view showing a configuration of a microphone according to another exemplary embodiment of the present disclosure; 
         FIG. 12  is a perspective view showing a part of the microphone shown in  FIG. 11 ; 
         FIGS. 13 and 14  are plan views showing another form of the microphone shown in  FIG. 11 ; 
         FIG. 15  is a view showing a configuration of a microphone according to another exemplary embodiment of the present disclosure; 
         FIG. 16  is a cross-sectional view taken along line C-C of  FIG. 15 ; 
         FIGS. 17 and 18  are plan views showing another form of the microphone shown in  FIG. 15 ; and 
         FIG. 19  is a plan view showing another form of the microphone shown in  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a view showing a configuration of a microphone according to an exemplary embodiment of the present disclosure;  FIG. 2  is an enlarged view of part A shown in  FIG. 1 ;  FIG. 3  is a cross-sectional view taken along line B-B of  FIG. 1 ;  FIG. 4  is a cross-sectional view taken along line B-B for describing an operational principle of the microphone shown in  FIG. 1 ;  FIGS. 5 through 10  are plan views another form of the microphone shown in  FIG. 1 ;  FIG. 11  is a view showing a configuration of a microphone according to another exemplary embodiment of the present disclosure;  FIG. 12  is a perspective view showing apart of the microphone shown in  FIG. 11 ;  FIGS. 13 and 14  are plan views showing another form of the microphone shown in  FIG. 11 ;  FIG. 15  is a view showing a configuration of a microphone according to another exemplary embodiment of the present disclosure;  FIG. 16  is a cross-sectional view taken along line C-C of  FIG. 15 ;  FIGS. 17 and 18  are plan views showing another form of the microphone shown in  FIG. 15 ; and  FIG. 19  is a plan view showing another form of the microphone shown in  FIG. 15 . 
     A microphone according to an exemplary embodiment of the present disclosure will be described with reference to  FIGS. 1 through 4 . 
     The microphone  100  according to the exemplary embodiment of the present disclosure may include a thin film member  110 , leg members  120 , first supports  130 , and piezoelectric members  140 . In addition, the microphone  100  may include a fixed body  160  configuring an outer casing of the microphone  100 . 
     The microphone  100  configured as described above may be mounted in a portable terminal or other electronic devices and convert sound waves into electrical signals. 
     Hereinafter, detailed components of the microphone  100  will be described. 
     The thin film member  110  may be vibrated by sound waves. For example, the thin film member  110  may have a film form. The thin film member  110  may be formed of a silicon dioxide (SiO 2 ) film, a silicon nitride film, or the like, deposited on one surface of the fixed body  160 . More specifically, the thin film member  110  may be formed by depositing the silicon dioxide (SiO 2 ) film or the silicon nitride film on a silicon substrate and then etching the silicon substrate. 
     The thin film member  110  may have a circular shape. However, the thin film member  110  is not limited to having the circular shape, but may have other shapes such as a square shape or a regular polygonal shape if necessary. 
     The thin film member  100  may include a plurality of layers. For example, the thin film member  110  may include a first layer formed of a silicon dioxide or silicon nitride film and a second layer formed of a dielectric material on the first layer. Here, the second layer may be used as a lower electrode layer of the piezoelectric member  140 . 
     The leg members  120  may be formed on the thin film member  110  and be extended lengthwise in a plane direction of the thin film member  110 . More specifically, a plurality of leg members  120  may be extended in a rotation symmetrical form based on the center of gravity of the thin film member  110 . 
     The leg member  120  may be formed integrally with the thin film member  110 . More specifically, the leg member  120  may be formed of a silicon dioxide (SiO 2 ) film, a silicon nitride film, or the like, similar to the thin film member  110 . 
     The first supports  130  may be formed in the fixed body  160 . More specifically, the first supports  130  may be formed together with the fixed body  160  in a process of forming a sound wave inlet  162  in the fixed body  160 . The first supports  130  may be a part of the fixed body  160 . 
     The first supports  130  may support the leg members  120 . More specifically, the first support  130  may rotate freely, based on a connection point P 1  (See  FIG. 3 ) (hereinafter, referred to as a first point) between the leg member  120  and the first support  130 . Therefore, when sound waves are introduced through the sound wave inlet  162 , the thin film member  110  may vibrate in a vertical direction (a Z axis direction in  FIG. 4 ) as illustrated with a dotted line in  FIG. 4 . 
     The first support  130  may include a pair of protrusions  132  as shown in  FIG. 2 . The pair of protrusions  132  may contact both sides of the leg member  120  as shown in  FIG. 2  to enable smooth movement of the leg member  120 . 
     The piezoelectric element  140  may connect the leg member  120  and the fixed body  160  to each other. More specifically, the piezoelectric member  140  may be extended from the fixed body  160  to the leg member  120 . 
     The piezoelectric member  140  may convert vibrations of the thin film member  110  into electrical signals. More specifically, a portion of the piezoelectric member  140  formed in the fixed body  160  may be firmly fixed, such that it does not move. However, a portion of the piezoelectric member  140  extended to the leg member  120  may be bent in the Z axis direction (See  FIG. 4 ) depending on movement of the leg member  120 . The piezoelectric member  140  is bent as described above to generate a piezoelectric effect, whereby a current having a predetermined magnitude may be generated. That is, when the leg member  120  moves vertically due to the vibrations of the thin film member  110 , the piezoelectric member  140  may generate the current having the predetermined magnitude whenever the leg member  120  moves. Here, since the magnitude of the current is in proportion to an amplitude of the leg member  120 , the piezoelectric member  140  may transmit current signals having different magnitudes, depending on a vibration frequency of the thin film member  110  to a controlling unit. 
     A position of the piezoelectric member  140  may be arbitrarily set. More specifically, since the amplitude of the leg member  120  increases from the first point P 1  toward the outside (toward the fixed body  160  in  FIG. 3 ), sensitivity to sound waves of the piezoelectric member  140  may be adjusted by adjusting a position of a connection point P 2  (hereinafter, referred to as a second point) between the piezoelectric member  140  and the leg member  120 . For example, when a distance L 2  from the first point P 1  to the second point P 2  is shorter than a distance L 1  from a connection point P 0  (hereinafter, referred to as a comparison point) between the thin film member  110  and the leg member  120  to the first point P 1 , sensitivity to sound waves may be decreased. On the contrary, when the distance L 2  is greater than the distance L 1 , sensitivity to sound waves may be increased. 
     The piezoelectric member  140  may include a lower electrode  142 , a piezoelectric element  144 , and an upper electrode  146 , as shown in  FIG. 3 . The lower electrode  142  may be formed on the fixed body  160 . More specifically, the lower electrode  142  may be formed over one surface of the fixed body  160  via an adhesive such as epoxy. The lower electrode  142  may be made of a conductive material. The lower electrode may be formed of two metal thin film layers made of titanium (Ti) and platinum (Pt), respectively. The piezoelectric element  144  may be formed of a piezoelectric material. For example, the piezoelectric element  144  may be formed of a ceramic, more specifically, lead zirconate titanate (PZT). The piezoelectric element  144  configured as described above may generate a predetermined electrical signal while being contracted or released depending on the amplitude of the leg member  120 . Here, the electrical signal may be changed depending on the amplitude of the leg member  120  and a size and a length of the piezoelectric element  144 . The upper electrode  146  may be formed on an upper surface of the piezoelectric element  144 . The upper electrode  146  may be formed of any one material selected from a group consisting of Pt, Au, Ag, Ni, Ti, Cu, and the like. Here, the lower electrode  142  and the upper electrode  146  may be connected to external circuits to transmit the electrical signal generated from the piezoelectric element  144  to an electronic device in which the microphone  100  is mounted. 
     The fixed body  160  may form an outer casing of the microphone  100  and be formed of one or more substrate. More specifically, the fixed body  160  may be formed in an array form on a single crystal silicon substrate or a silicon on insulator (SOI) substrate through a semiconductor process. The fixed body  160  manufactured in the scheme as described above may have a rectangular, polygonal, or circular cross section by a cutting process. 
     The fixed body  160  may be provided with the sound wave inlet  162  through which sound waves are introduced. The sound wave inlet  162  may be formed by an etching process of a silicon substrate. For reference, the etching process may include both dry and wet etching processes. Meanwhile, although the case in which a cross section of the sound wave inlet  162  has a rectangular shape has been shown in the accompanying drawings, the cross section of the sound wave inlet  162  is not limited to the rectangular shape, and the cross section of the sound wave inlet  162  may have a circular shape or other shapes if necessary. 
     Since the microphone  100  configured as described above may effectively sense the vibrations of the thin film member  110  while preventing the piezoelectric member  140  from hindering the vibrations of the thin film member  110 , it may improve sensitivity to sound waves. 
     In addition, since the microphone  100  according to the exemplary embodiment of the present disclosure may adjust sensitivity to sound waves by adjusting the connection point (that is, the second point P 2 ) between the piezoelectric member  140  and the leg member  120 , it may be applied to various fields. 
     Next, another form of the microphone according to the exemplary embodiment of the present disclosure will be described with reference to  FIGS. 5 through 10 . 
     In another form of the microphone  100 , a disposition form of the piezoelectric member  140  may be changed, as shown in  FIG. 5 . More specifically, the piezoelectric member  140  may be extended in a direction in which it is in parallel with the leg member  120 . Here, the piezoelectric member  140  may have one end fixed to the fixed body  160  and the other end connected to the leg member  120 . 
     The microphone  100 , configured as described above, may have an advantage that a length of the piezoelectric member  140  may be decreased. 
     Another form of the microphone  100  may include piezoelectric members  140 :  1402  and  1404  having different shapes as shown in  FIGS. 6 and 7 . More specifically, first and second piezoelectric members  1402  and  1404  may have different sizes and be connected to the leg members  120  at different points P 3  and P 4 , respectively. More specifically, the first piezoelectric member  1402  may be connected to the leg member  120  at a third point P 3 , and the second piezoelectric member  1404  may be connected to the leg member  120  at a fourth point P 4 . Here, a distance L 3  from the first point P 1  to the third point P 3  may be longer than a distance L 4  from the first point P 1  to the fourth point P 4 . 
     In the microphone configured as described above, since two piezoelectric members  1402  and  1404  sense sound waves at different sensitivities, sound waves may be simultaneously sensed in various bands. 
     In another form of the microphone, a plurality of piezoelectric members  140 :  1402  and  1404  may be disposed in parallel with each other as shown in  FIG. 8 . As a result, sensitivity to sound waves may be further improved. 
     Another form of the microphone may be different in terms of a manner in which the piezoelectric member  140  is disposed from the form of the microphone described above, as shown in  FIGS. 9 and 10 . More specifically, in the present form, the piezoelectric member  140  may be connected to the first support  130 . To this end, a shape of the piezoelectric member  140  may be changed to a curved shape as shown in  FIG. 9 . Alternatively, a shape of the first support  130  may be changed to a curved shape as shown in  FIG. 10 . 
     Next, a microphone according to another exemplary embodiment of the present disclosure will be described. For reference, in the following description, the same components as those of the microphone according to the exemplary embodiment of the present disclosure described above will be denoted by the same reference numerals and a description thereof will be omitted. 
     A microphone according to another exemplary embodiment of the present disclosure will be described with reference to  FIGS. 11 and 12 . 
     The microphone  100  according to another exemplary embodiment of the present disclosure may include a thin film member  110 , leg members  120 , first supports  130 , apiezoelectric member  140 , and second supports  150 , and may be different from the microphone  100  according to the exemplary embodiment of the present disclosure described above in terms of a disposition structure of the piezoelectric member  140 . 
     The thin film member  110  may have a circular cross section and include a plurality of leg members  120 . The leg members  120  may be extended in a radial direction based on the center of gravity of the thin film member  110  and be connected to the first supports  130 . Here, a connection structure between the leg member  120  and the first support  130  may be the same as or similar to the connection structure between the leg member  120  and the first support  130  in the exemplary embodiment of the present disclosure described above. Therefore, seesaw movement in which the other end (portion connected to the piezoelectric member  140 ) of the leg member  120  vibrates in a direction opposite to one direction when one end (portion connected to the thin film member  110 ) of the leg member  120  vibrates in one direction may be performed. 
     The piezoelectric member  140  may have a ring shape. More specifically, the piezoelectric member  140  may have a closed curved shape in which it encloses a circumference of the thin film member  10 . However, the piezoelectric member  140  is not limited to having the ring shape, but may have a curved shape in which a portion thereof is opened if necessary. 
     The piezoelectric member  140  may be disposed so that a distance L 2  from the first point P 1  to the second point P 2  is greater than a distance L 1  from the comparison point P 0  to the first point P 1 . This disposition structure may be advantageous for transferring fine vibrations of the thin film member  110  to the piezoelectric member  140 . 
     The second supports  150  may be radially extended from the fixed body  160  toward the center of the thin film member  110 . Here, the number of second supports  150  may be the same as that of leg members  120 , and the second supports  150  may be disposed so as not to be overlapped with the leg members  120 . The second supports  150  formed as described above may be connected to the first supports  130  to fix the first supports  130  to the fixed body  160 . In addition, the second supports  150  may fix a part of the piezoelectric member  140 . 
     In the microphone  100 , configured as described above, since the piezoelectric member  140  having the ring shape is connected to the plurality of leg members  120  to sense the vibrations of the thin film member  110 , sensitivity to sound waves may be improved. 
     Next, another form of the microphone according to another exemplary embodiment of the present disclosure will be described with reference to  FIGS. 13 and 14 . 
     In another form of the microphone according to another exemplary embodiment of the present disclosure, as shown in  FIG. 13 , the numbers of leg members  120  and second supports  150  may be decreased. More specifically, in the present form, the numbers of leg members  120  and second supports  150  may be two, respectively. In this form, since an angle θ from a fixed position Pf of the piezoelectric member  140  to a movable point Pm of the piezoelectric member  140  is increased, an extension and contraction rate of the piezoelectric member  140  may be increased. As a result, sensitivity to sound waves may be improved. 
     Another form of the microphone may include a plurality of piezoelectric members  140 :  1402  and  1404  as shown in  FIG. 14 . Here, the respective piezoelectric members  140 :  1402  and  1404  may sense sound waves in different frequency bands. 
     To this end, a first piezoelectric member  1402  may be connected to the leg member  120  at a fourth point P 4 , and a second piezoelectric member  1404  may be connected to the leg member  120  at a third point P 3 . Here, since the first piezoelectric member  1402  has a displacement width relatively larger than that of the second piezoelectric member  1404 , it may sense sound waves in a high frequency band. Unlike this, since the second piezoelectric member  1404  has a displacement width relatively smaller than that of the first piezoelectric member  1402 , it may sense sound waves in a low frequency band. 
     A microphone according to another exemplary embodiment of the present disclosure will be described with reference to  FIGS. 15 and 18 . 
     The microphone  100  according to another exemplary embodiment of the present disclosure may be different in terms of a connection structure of a leg member  120  from the microphones  100  according to the exemplary embodiments of the present disclosure described above. That is, in the microphone  100  according to another exemplary embodiment of the present disclosure, the leg member  120  may be directly connected to the fixed body  160  without a separate support. In addition, the piezoelectric member  140  may be extended from the fixed body  160  toward the leg member  120  and connected to a second point P 2  of the leg member  120 . 
     In the microphone  110  configured as described above, an amplitude of the leg member  120  depending on vibrations of the thin film member  110  may be reduced from a comparison point P 0  to a first point P 1 , as shown in  FIG. 16 . Therefore, a position of the second point P 2  at which the piezoelectric member  140  and the leg member  120  are connected to each other is adjusted, whereby sensitivity to sound waves may be raised or lowered. For example, when a length L 2  from the second point P 2  to the comparison point P 0  is reduced, the vibrations of the thin film member  110  are transferred well to the piezoelectric member  140 , whereby sensitivity to sound waves may be raised. Unlike this, when the length L 2  is increased, the vibrations of the thin film member  110  are not properly transferred to the piezoelectric member  140 , whereby sensitivity to sound waves may be lowered. However, when the distance L 2  is excessively short, the piezoelectric member  140  may hinder the vibrations of the thin film member  110 . Therefore, it may be preferable that the second point P 2  be spaced apart from the comparison point P 0  by a predetermined distance. 
     Meanwhile, in another form of the microphone  100 , the piezoelectric member  140  may have a ring shape having an oval trajectory (See  FIG. 17 ). In addition, in another form of the microphone  100 , the piezoelectric member  140  may have a ring shape having a circular trajectory, and the sound wave inlet  162  may have a rectangular cross-sectional shape (See  FIG. 18 ). 
     Since the microphone  100  configured as described above may have a simplified structure, a process of manufacturing the microphone  100  may be simplified and a cost required to manufacture the microphone  100  may be decreased. 
     Next, another form of the microphone according to another exemplary embodiment of the present disclosure will be described with reference to  FIG. 19 . 
     Another form of the microphone  100  may include a protrusion member  170  and have a form similar to the form shown in  FIG. 11 . That is, in another exemplary embodiment of the present disclosure, the piezoelectric member  140  may be fixed to the protrusion member  170  and have a ring shape. 
     As set forth above, since the microphone according to the exemplary embodiments of the present disclosure may arbitrarily adjust sensitivity to sound waves, it may be widely used from a precision field requiring a high sensitivity to a general field requiring a low sensitivity. 
     In addition, since the microphone according to the exemplary embodiments of the present disclosure may convert the vibrations of the thin film member into the electrical signal of the piezoelectric element, sensitivity to sound waves may be improved. 
     While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the spirit and scope of the present disclosure as defined by the appended claims.