Patent Publication Number: US-2017353800-A1

Title: Diaphragm assembly

Description:
TECHNICAL FIELD 
     The present invention relates to a diaphragm assembly, and more particularly, to a diaphragm assembly capable of improving frequency characteristics including the damping function thereof. 
     BACKGROUND ART 
     A component speaker includes a diaphragm assembly. When a driving force is applied to the diaphragm, the diaphragm assembly vibrates to generate a sound pressure. The driving force varies depending on the speaker type. The dynamic speaker uses electromagnetic force induced in the coil as the driving force. The electrostatic speaker uses electrostatic force acting on the diaphragm as the driving force. The piezoelectric speaker uses change of the shape of the piezoelectric body as the driving force. 
       FIG. 1  shows a conventional diaphragm assembly and a speaker apparatus including the same. A diaphragm assembly used for a TV or the like generally has a square or track shape with a major axis and a minor axis perpendicular to the major axis. This rectangular shape is advantageous in attaching the speaker to the bezel located at the edge of the display. The diaphragm assembly includes a vibration surface  60 , an edge  50 , and a suspension  40 . The vibration surface  60  is formed of compressed pulp and includes a stiffness enhancing portion forming a convex portion on the upper surface thereof to enhance the stiffness. 
     The edge  50  is formed of an elastic material such as Thermoplastic Polyurethane (TPU) and has an annular shape so as to be joined to the rim of the vibration surface. The edge includes a portion formed on the inner side thereof and joined to the vibration surface and a portion formed on the outer side thereof and joined to a fixed end such as a frame of the speaker apparatus or the suspension  40 . A convex portion for structurally enhancing the elasticity of the edge is formed between the joining portion of the vibration surface and the joining portion of the fixed end. 
     The suspension  40  functions to provide a damping force to the vibration surface  60  and is formed by a metal leaf spring. One side of the suspension  40  is attached to the bottom surface of the vibration surface  60  and the other side is attached to a fixed end such as the frame  20  of the speaker apparatus. 
     Since the speaker of a rectangular structure has a different vibration distance according to the direction of vibration, it structurally has a poor frequency response characteristic compared to speakers having a circular or square structure. Particularly, since the vibration surface  60  is elongated along the major axis, break-up vibration occurs by a vibration mode at a specific frequency. When the break-up mode vibration occurs, vibrations having a phase difference of 180° between a specific area and an adjacent area of the vibration surface  60  cause destructive interference with each other, and a dip phenomenon, which refers to significant drop of the sound pressure at a corresponding frequency, inevitably occurs. The dip phenomenon distorts the frequency response characteristic of the speaker apparatus, and as a result, the output sound is distorted, which results in severe degradation of sound quality. 
     The suspension  40  may provide an additional damping force to help attenuate the dip phenomenon caused by the break-up mode vibrations. However, the suspension  40  provides only limited damping, and is therefore not sufficient to eliminate the dip phenomenon. Moreover, since the conventional diaphragm structure further includes the suspension  40 , the unit cost is increased, and the process becomes complicated. Thereby, the process cost is increased, and the defect rate is increased. 
     DISCLOSURE 
     Technical Problem 
     It is an aspect of the present invention to provide a diaphragm assembly capable of providing a damping force to a vibration surface and suppressing the break-up mode vibration. 
     It is another aspect of the present invention to provide a diaphragm assembly with a major axis and a minor axis capable of suppressing abnormal noise that may occur in the diaphragm assembly. 
     Technical Solution 
     In accordance with one aspect of the present invention, a diaphragm assembly includes: a diaphragm configured to generate a sound pressure by vibration; and an edge of an elastic material, one side of the edge being joined to the diaphragm and the other side of the edge being joined to a fixed end, wherein the diaphragm includes: a vibration surface configured to generate a sound pressure by vibration and having a rim; an extension extending outward from at least a part of the vibration surface; and an joining portion formed at an end of the extension and joined to the fixed end, wherein the one side of the edge is joined to the rim of the vibration surface. 
     In the diaphragm assembly according to an embodiment of the present invention, the extension partially extends from the vibration surface. 
     In the diaphragm assembly according to an embodiment of the present invention, the joining portion is annularly connected to connect the plurality of the partially extending extensions. In the diaphragm assembly according to an embodiment of the present invention, the vibration surface is substantially formed in a rectangular shape having the major axis and the minor axis, and the extension includes a primary extension formed to extend from both ends of the major axis of the vibration surface. 
     In the diaphragm assembly according to an embodiment of the present invention, the vibration surface further includes a secondary extension adjacent to the primary extension. 
     In the diaphragm assembly according to an embodiment of the present invention, a surface of the secondary extension adjacent to the primary extension extends at an acute angle with respect to the vibration surface. 
     In the diaphragm assembly according to an embodiment of the present invention, a surface of the secondary extension adjacent to the primary extension extends at an obtuse angle with respect to the vibration surface. 
     In the diaphragm assembly according to an embodiment of the present invention, the extension extends curvedly. 
     In the diaphragm assembly according to an embodiment of the present invention, the extension includes a downwardly convex shape. 
     In the diaphragm assembly according to an embodiment of the present invention, the vibration surface has the same height as the joining portion. 
     In the diaphragm assembly according to an embodiment of the present invention, the extension includes an upwardly convex shape. 
     In the diaphragm assembly according to an embodiment of the present invention, a damping agent is applied to an upper surface of the extension. 
     In the diaphragm assembly according to an embodiment of the present invention, the joining portion is joined to a bottom surface of the edge through an upper surface thereof. 
     In the diaphragm assembly according to an embodiment of the present invention, the damping agent applied to the upper surface of the extension contacts the bottom surface of the edge. 
     In the diaphragm assembly according to an embodiment of the present invention, the joining portion is joined to a frame of a speaker apparatus through a bottom surface thereof. 
     In the diaphragm assembly according to an embodiment of the present invention, the joining portion is joined to a frame of a speaker apparatus with a metal suspension interposed. 
     In accordance with another aspect of the present invention, a diaphragm assembly including a diaphragm configured to generate a sound pressure by vibration, wherein the diaphragm includes: a vibration surface configured to generate a sound pressure by vibration and formed in a shape having a major axis and a minor axis, the vibration surface having a rim; an extension extending outward from at least a part of the rim near both ends of the major axis of the vibration surface and not formed on at least a part of the rim near the minor axis of the vibration surface; and an joining portion formed at an end of the extension and joined to the fixed end, wherein a part of the vibration surface on the major axis is not connected to the fixed end. 
     In the diaphragm assembly according to an embodiment of the present invention, at least one of the extension and the joining portion is not formed at the part on the major axis. 
     Advantageous Effects 
     According to the configuration above, the diaphragm assembly according to the present invention may suppress the break-up mode vibrations by generating an additional damping force through an extension. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view of a speaker apparatus including a diaphragm assembly according to the prior art. 
         FIG. 2  is a perspective view of a speaker apparatus including a diaphragm assembly according to an embodiment of the present invention. 
         FIG. 3  is an exploded perspective view of a speaker apparatus including a diaphragm assembly according to an embodiment of the present invention. 
         FIGS. 4 to 15  are plan views of a diaphragm of a diaphragm assembly according to other embodiments of the present invention. 
         FIG. 16  is a cross-sectional view taken along line a-a in  FIG. 15 ; 
         FIGS. 17 to 20  are a perspective view and a plan view of a diaphragm of a diaphragm assembly according to other embodiments of the present invention. 
     
    
    
     BEST MODE 
     A diaphragm assembly according to the present invention includes a diaphragm and an edge. 
     The diaphragm  110  functions to generate a sound pressure by vibration. The material of the diaphragm  110  is not particularly limited, and materials such as, for example, paper, metal, polymer film, glass fiber, or carbon fiber may be used. The shape of the plane of the diaphragm  110  is not particularly limited and may be a plane shape such as a square, a circle, a rectangle, a track, an ellipse, or the like. The diaphragm  110  includes a vibration surface  112 , an extension  114 , and a joining portion  116 . 
     The vibration surface  112  functions to generate a sound pressure by vibration, and the rim thereof is joined to the inner side of the edge  120 . The extension  114  is formed to extend outward from at least a part of the vibration surface. The extension  114  is preferably formed on the outer side on the major axis to effectively eliminate the break-up mode vibration along the major axis. The joining portion  116  is formed at the end of the extension and joined to a fixed end such as a frame of the speaker apparatus or the outer side of a metal suspension. The vibration surface  112 , the extension  114 , and the joining portion  116  are integrally formed. Since the vibration surface  112 , the extensions  114  and the joining portion  116  are integrally formed, the manufacturing cost of the diaphragm  110  may be reduced by producing the diaphragm  110  through a single press operation. 
     In the conventional diaphragm assembly  10 , the entire rim of the diaphragm  11  is joined to the edge  12 , and the diaphragm  11  is not directly connected to a fixed end such as a frame but connected to the fixed end through the edge  12 . In the present invention, on the other hand, the diaphragm assembly is indirectly connected to the fixed end through the edge  120 , and in addition, the joining portion  116  of the diaphragm  110  is directly connected to the fixed end. The fixed end may provide a damping force directly to the vibration surface  112  via the extension  114 . With this configuration, the diaphragm  110  functions as a conventional suspension. According to this configuration, the diaphragm can provide a direct damping force to the vibration surface to eliminate the metal suspension, and therefore the manufacturing cost of the diaphragm assembly is reduced, and the step of attaching the suspension is eliminated. Thereby, the assembly cost is reduced, and the defect rate is lowered. 
     According to an embodiment, the diaphragm assembly may further include a conventional metal suspension  130 . In this case, the damping force provided by the extension  114  of the diaphragm  110  and the additional damping force of the suspension  130  are provided, and thus the break-up mode vibration of the diaphragm  110  can be prevented more effectively. Thereby, vibration close to an ideal piston vibration in which the entire area of the vibration surface  112  uniformly vibrates may be obtained. More preferably, the height of the extension  114  may be less than the heights of the vibration surface  112  and the joining portion  116 , and may have a downwardly curved shape. More specifically, the extension  114  may have a curved shape that is convex downward. This shape is advantageous in providing the additional damping force of the extension  114 . 
     Alternatively, the extension  114  may have a curved shape that is convex upward (see  FIGS. 15 and 16 ). In this case, the shape of the extension  114  and the cross-sectional shape of the edge  120  shown in  FIGS. 2 and 3  may correspond to each other to some extent. According to this structure, a damping agent  118  may be applied to the upper surface of the extension  114  and covered by the edge  120 . Thereby, the bottom surface of the edge  120  may appear to be covered with the damping agent  118 . Particularly, in the case of a speaker having a diaphragm of a rectangular, track, or elliptic shape, which is the main application object of the present invention, there is a possibility that fine vibration occurs at both ends of the major axis of the diaphragm, generating noise and deteriorating sound quality. If the above structure is applied to the extension  114  extending outward from both ends of the major axis of the vibration surface  112 , the fine vibration occurring at both ends of the major axis of the diaphragm may be easily eliminated without requiring any additional parts or processes. 
     The shapes of the extension  114  and the joining portion may be diversified according to the material of the diaphragm or the sound characteristic of a desired speaker apparatus. According to the embodiment of  FIG. 4 , two extensions  114  extend on the outer sides of the major axis of the diaphragm, and the joining portion  116  is formed to extend from each of the extensions  114 . Although the joining portion  116  is shown as being distinguished from the extensions  114  in the figure, it indicates the areas to be adhered to the fixed end, and may be integrated with each other in a practical product so as not to be visually distinguished. 
     Here, the shape of the extension  114  may form an obtuse angle α 1  with respect to the vibration surface  112  as shown in  FIG. 4 , form a right angle with respect to the vibration surface  112  as shown in  FIG. 5 , or form an acute angle α 2  with respect to the vibration surface  112  as shown in  FIG. 6 . Although not shown, the joining portion  116  may be configured to be connected in a closed loop shape as in the embodiments of  FIGS. 10 to 14 . These various shapes may be selectively applied according to the material of the diaphragm and desired sound characteristics. 
     According to the embodiments shown in  FIGS. 4 to 6 , in the diaphragm  110 , a weak damping force acts on the middle portion of the major axis, and a strong damping force acts on the ends of the major axis of the diaphragm. Therefore, the break-up mode vibration may be effectively prevented, and suppression of vibration of the vibration surface  112  may be minimized. Thereby, lowering of the SPL and increase of the resonance frequency may be minimized. 
     Hereinafter, the embodiments of  FIGS. 7 to 9  will be described. These embodiments are different from the embodiments of  FIGS. 4 to 6  in that the extension  114  further includes a primary extension  114 - 1 ,  114 - 2  and a secondary extension  114 - 3 ,  114 - 4  formed adjacent thereto. The end of the primary extension  114 - 1 ,  114 - 2  is connected to the end of the secondary extension  114 - 3 ,  114 - 4  adjacent to the primary extension  114 - 1 ,  114 - 2  through a joining portion  116 - 1 ,  116 - 2 . Here, the shapes of the secondary extension  114 - 3 ,  114 - 4  may form an obtuse angle α 1  with respect to the vibration surface  112  as shown in  FIG. 7 , a right angle with respect to the vibration surface  112  as shown in  FIG. 8 , or an acute angle α 2  with respect to the vibration surface  112  as shown in  FIG. 9 . Four secondary extensions  114  are formed in a manner that one secondary extension  114  is formed at four each end of the two primary extensions  114 . However, the number of the secondary extensions  114  is not limited thereto. 8 secondary extensions may be formed in a manner that two secondary extensions are formed at each end, or 12 or more secondary extensions may be formed in a manner that three or more secondary extensions are formed at each end. 
     According to the embodiments of  FIGS. 7 to 9 , the secondary extensions  114 - 3  and  114 - 4  can provide an additional damping force, and accordingly the break-up mode vibration of the diaphragm may be more effectively suppressed. 
     Hereinafter, the embodiments of  FIGS. 10 to 14  will be described. These embodiments are different from the embodiments of  FIGS. 7 to 9  in that the joining portion  116  is connected in a ring shape. According to these embodiments, since the joining portion  116  is seamlessly connected to the fixed end, a stronger damping force can be provided to the vibration surface  112 . 
     The shape of the secondary extensions  114 - 3  and  114 - 4  may form an obtuse angle α 1  with respect to the vibration surface  112  as shown in  FIG. 10 , a right angle α 1  with respect to the vibration surface  112  as shown in  FIG. 11 , or an acute angle α 2  with respect to the vibration surface  112  as shown in  FIG. 12 . Four secondary extensions  114 - 3 ,  114 - 4  are formed in a manner that one secondary extension  114 - 3 ,  114 - 4  is formed at each of both ends of the primary extensions  114 - 1 ,  114 - 2 . However, the number of the secondary extensions is not limited thereto. 8 secondary extensions may be formed in a manner that two secondary extensions are formed at each end, or 12 or more secondary extensions may be formed in a manner that three or more secondary extensions are formed at each end. 
       FIG. 13  illustrates an embodiment in which four extensions  114 - 1 ,  114 - 2 ,  114 - 3 , and  114 - 4  extend outward from the edges near both ends of the diaphragm on the major axis and the joining portion  116  is connected in a ring shape.  FIG. 14  illustrates an embodiment similar to the embodiment of  FIG. 13 . In the embodiment of  FIG. 14 , the extensions  114 - 1 ,  114 - 2 ,  114 - 3 , and  114 - 4  have a refracting shape to provide an additional damping force. Such a refracting shape is not limited to the embodiment shown in  FIG. 14 . The shape may have a single refraction, two refractions as shown in the figure, or three or more refractions. 
       FIGS. 15 and 16  illustrate an embodiment in which four extensions  114 - 1 ,  114 - 2 ,  114 - 3 , and  114 - 4  extend outward from the edges near both ends of the diaphragm on the major axis and the joining portion  116  is not connected in a ring shape. The ends of the four extensions are provided with joining portions  116 - 1 ,  116 - 2 ,  116 - 3 , and  116 - 4 , respectively. The extensions shown in  FIGS. 15 and 16  have an upwardly convex shape, which correspond to the convex shape of the edge  120  shown in  FIGS. 2 and 3 . The damping agent  118  is applied to the upper portions of the extensions  120 . In the process of joining one side of the edge  120  to the rim of the vibration surface, the extensions are accommodated in a space formed in the bottom surface of the edge  120 , and the damping agent  118  applied to the upper portions of the extensions is brought into contact and covered with the inner surface of the edge  120 . Thus, the structure of the extensions of  FIGS. 15 and 16  may not only further provide a damping force to the vibration surface through the extensions, but also eliminate fine vibration generated at both ends of the vibration surface on the major axis, through the damping agent  118  and the edge  120 . 
     While  FIG. 15  illustrates that the extensions  114  form a right angle with respect to the vibration surface  112 , the extensions  114  may form an obtuse angle α 1  or an acute angle α 2  with respect to the vibration surface  112 , as shown in the other embodiments and figures described above. Needless to say, it is also possible for the extensions to have a refracting shape as shown in  FIG. 14 . Since such a shape has been already shown in the drawings, the corresponding drawing is omitted in order to avoid redundancy. 
     Korean Patent No. 1,560,365, granted to the inventor of the present invention, discloses a diaphragm structure for securing stiffness enough to sufficiently prevent break-up mode vibrations of a diaphragm having a major axis and a minor axis to improve the sound characteristics. Such a diaphragm has a very high stiffness due to the shape thereof. However, in order to prevent the break-up mode vibration of the diaphragm having a shape with the major axis and the minor axis and to improve the sound quality, techniques other than securing stiffness are further required. 
     In the case where the diaphragm does not have a point-symmetrical shape (circle, square, etc.), particularly the diaphragm has a thin and long shape (having a major axis and a minor axis), the vibration direction of the diaphragm may be disturbed or shaken, even though high stiffness of the diaphragm may be secured and thus deformation of the diaphragm can be prevented. Particularly, in the case of a compact speaker, this behavior of the diaphragm causes elements around the diaphragm to collide or produce friction with the diaphragm, which results in noise. 
       FIGS. 17 and 18  show a diaphragm type obtained by applying the present invention to the structure of the diaphragm disclosed in Korean Patent No. 1,560,365. The illustrated diaphragm  110  has extensions  114 - 1  and  114 - 2  extending outward from the rim near both ends of the major axis of the vibration surface  112  and has joining portions  116 - 1  and  116 - 2  formed at the ends of the extensions. When both ends of line C-C, which is the major axis of the diaphragm  110 , is supported on the frame  200  by the extensions and the joining portions, the diaphragm is likely to roll about line C-C, which is the major axis of the diaphragm  110  and serves as a rotation axis, independently of the damping force provided by the extensions and the joining portions because the diaphragm is axially connected to the frame  200  along line C-C. Such rolling of the diaphragm causes contact between the voice coil  140  fixed to the bottom of the diaphragm assembly  110 ,  120  and  130  and the magnetic circuits  310 ,  320  and  330 , which may result in undesired noise in the speaker. 
     Accordingly, in the present invention, the vibration surface  112  is arranged unconnected with the frame  200  at the portion of the major axis line C-C line that causes such rolling, thereby preventing the diaphragm  110  from rolling about the major axis. To this end, the present invention discloses a structure in which at least a joining portion is eliminated from the part of the major axis line C-C. For example,  FIGS. 19 and 20  illustrate a diaphragm in which the joining portion  116  is not formed on the portion of the major axis line C-C. This configuration may be obtained by cutting away parts of the joining portions formed at both ends of the major axis of  FIGS. 17 and 18  along a cutting line parallel with the minor axis. As the vibration surface is not directly connected to the frame  200  through the extensions and the joining portions on the major axis, the above-described concern may be eliminated. 
     The diaphragm shown in  FIG. 15  also has a structure in which the major axis is not directly connected to the frame  200 . In this structure, none of the extensions and the joining portions is formed on the major axis. The diaphragm shown in  FIGS. 13 and 14  also has a structure in which the major axis is not directly connected to the frame  200 . In this structure, the extensions are not formed on the major axis. 
     As described above, when at least one of the extensions and the joining portion proposed in the present invention is configured not to be formed on the major axis at both ends of the major axis of the vibration surface, rolling of the diaphragm described above may be prevented. 
     It is apparent that the shapes of the extensions and the joining portions described in the embodiments above can be combined with each other. That is, various combinations relating to whether a secondary joining portions is to be formed in addition to the primary extension, what kind of angle (among an acute angle, a right angle, and an obtuse angle) is to be formed between the vibration surface and the extensions, whether or not the joining portion is connected in an annular shape, whether the extension is bent downward or upward, whether the extension has a refracting shape, whether or not at least one of the extensions and the joining portions is eliminated from the major axis portion at both ends of the major axis of the vibration surface, and the like are also within the scope of the present invention. 
       FIGS. 2 and 3  illustrate a speaker apparatus including a diaphragm assembly according to an embodiment of the present invention. The speaker apparatus includes a diaphragm assembly  110 ,  120 , and  130 , a voice coil  140 , magnetic circuits  310 ,  320 , and  330 , and a frame  200 . The voice coil  140  may be attached to the bottom of the diaphragm assembly  110 ,  120  and  130 . The voice coil may be self-bonded and attached to the bottom of the diaphragm assembly  110 ,  120  and  130 , or may be attached to the bottom of the diaphragm assembly with a bobbin interposed therebetween. The voice coil  140  may have a circular shape as shown in  FIG. 3 , a square shape, or a track shape, depending on the shape of the magnetic circuit. The voice coil  140  may be joined to a seating portion formed on the suspension  130  or to the bottom surface of the diaphragm  110 , according to an embodiment. 
     The magnetic circuit includes a yoke  330 , a magnet  320  and a plate  310 . In the positional relationship between the magnet  320  and the voice coil  140 , the magnet  320  may be positioned outside or inside the voice coil  140 , or may be distributed inside and outside the voice coil  140 . The magnet  320  may be made of a material such as neodymium or ferrite according to an embodiment. 
     The frame  200  forms the outer shape of the speaker apparatus, accommodates the magnetic circuits  310 ,  320  and  330  therein, and is joined to the edge of the diaphragm assembly  110 ,  120  and  130  through the rim of the upper opening. According to an embodiment, a radiator  400  formed of a material such as a metal having a high thermal conductivity as shown in  FIG. 3  may be further provided to improve heat dissipation performance. The radiator  400  is configured to discharge heat generated from the voice coil  140  to the outside. As shown in the figure, the radiator  400  may be configured to be coupled to an opening formed on the bottom surface of the frame  200  including a plurality of heat dissipation holes. Further, it is preferable that the radiator grill is brought into contact with the magnetic circuits  310 ,  320 , and  330  to discharge heat transferred to the magnetic circuits  310 ,  320 , and  330  through conduction. 
     According to an embodiment, the diaphragm assembly may further include a suspension  130  composed of a metal leaf spring. The suspension  130  may be attached to the bottom surface of the diaphragm assembly to provide additional damping force to the diaphragm. The voice coil  140  may be directly joined to the bottom surface of the suspension, and an end of the voice coil may be connected to the suspension. The suspension may further function as an electric path for providing an external acoustic signal to the voice coil. 
     The diaphragm  110  of the diaphragm assembly may further include a stiffness enhancing portion for enhancing the stiffness on the upper surface thereof. The stiffness enhancing portion may be a convex portion formed in an annular or track shape along the periphery of the diaphragm. According to an embodiment, in order to further enhance the stiffness, the concave portion may be gradually lowered toward the center along the major axis direction as shown in  FIG. 3 , and the peak point of the convex portion surrounding the concave portion may become higher toward the center along the major axis. The diaphragm may further include expanded portions at both ends of the central are as shown in  FIG. 3  to secure a space where the voice coil  140  is seated. In an embodiment further including the suspension  130 , since the expanded portion secures a space for attaching the suspension  130 , joining between the suspension  130  and the diaphragm  110  may be reinforced, thereby improving the reliability of the speaker apparatus. 
     INDUSTRIAL APPLICABILITY 
     It is apparent that the above-described invention is industrially applicable.