Patent Publication Number: US-2007121992-A1

Title: Speaker and electronic device equipped with the speaker

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2005-346090, filed Nov. 30, 2005, the entire contents of which are incorporated herein by reference.  
     BACKGROUND  
      1. Field  
      One embodiment of the invention relates to improvement of an attachment mechanism of a speaker converting an electric signal into mechanical vibration and, more particularly, to a structure in which when a speaker successively generating great vibration at an actual use is attached to a cabinet having elements (high-definition display device, high-frequency components, etc.) which do not like vibration, vibration (sound pressure) is hardly transmitted to the cabinet or the elements provided in the cabinet.  
      2. Description of the Related Art  
      In a conventional speaker structure, a frame and a flange are formed in a mechanically coupled state. Vibration occurring at a diaphragm is transmitted to the frame. For this reason, the vibration is also transmitted to the flange serving as a fixing portion of the cabinet (see a speaker structure of Jpn. Pat. Appln. KOKAI Publication No. 10-023596 or Jpn. Pat. Appln. KOKAI Publication No. 2002-159091).  
      In Jpn. Pat. Appln. KOKAI Publication No. 10-023596, a magnetic circuit is inserted into a resin casing and a distal end portion of the resin frame is engaged with an opening portion of the resin casing to fix the magnetic circuit inside the resin casing, a breakage portion which can be broken with a circumferential force is provided on a flange of the resin casing, a flange portion at a top of the breakage portion is welded on the resin frame. In Jpn. Pat. Appln. KOKAI Publication No. 2000-159091, injection molding is executed by using thermoplastic resin to mold a dome portion, a voice coil junction, a cone portion, and a frame-attached outer peripheral portion as one body.  
      When the speaker having such a structure is mounted, it is considered that a damping member (rubber-formed, donut-shaped bushing, etc.) having internal loss to the vibration is attached to the flange portion and the speaker is fixed to the cabinet with a screw passing through the damping portion, in order to restrict transmission of the vibration to the cabinet. In this case, the flange portion of the speaker is mechanically screwed on the cabinet via the damping portion.  
      One of the objects of the present invention is to prevent the vibration generated at the speaker from being easily transmitted even if the speaker is firmly fixed to the cabinet. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.  
       FIG. 1  is a cross-sectional view illustrating a structure of a speaker according to a first embodiment of the invention;  
       FIG. 2  is a perspective view illustrating an outer appearance of the speaker according to the first embodiment of the invention;  
       FIG. 3  is an illustration of an effect of a frame opening portion covered under feet of a spring structure in the structure of  FIG. 2 ;  
       FIG. 4  is an illustration of an outer appearance of an electronic device (slim-type digital TV equipped with the speaker of  FIG. 1 ) according to the first embodiment of the invention; and  
       FIG. 5  is an illustration of the manner of providing the speaker of  FIG. 1  inside the device of  FIG. 4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, a speaker comprises a frame, a drive source attached to the frame, which converts an electric signal into mechanical vibration, a diaphragm coupled to the drive source, which emits an acoustic wave corresponding to the mechanical vibration, and an attachment structure coupled to a predetermined portion of the frame, which has a flange at a position remote from the predetermined portion, which has predetermined compliance in a direction of vibration of the diaphragm, and which has predetermined stiffness in a direction substantially orthogonal to the direction of vibration of the diaphragm.  
       FIG. 1  is a cross-sectional view illustrating a structure of a speaker  10  according to the embodiment of the invention. The speaker  10  is roughly composed of a frame portion  100 , a field unit  200 , a vibration system ( 300 - 306 ), and an attachment structure ( 400 - 404 ).  
      The vibration system ( 300 - 306 ) is composed of a conical (or ellipsoidal or rectangular) diaphragm  300 , an edge  302 , a voice coil  304  wound round a voice coil bobbin, a damper (spider)  306  and a center cap  308 . The attachment structure ( 400 - 404 ) is formed by integrally molding a spring structure  400  obtained by shaping a flat plate into wave, feet  402 , and a flange  404 , in plastic (thermoplastic resins such as PP, PE, PS, ABC, etc.)  
      The field unit  200  is composed of a main magnet  202 , a top plate  204 , a pole piece (center pole)  206  integrated with a bottom plate, and a cancel magnet  208  (and a magnet cover if necessary).  
      The frame portion  100  is shaped in a deep dish having a trapezoidal cross-section. A hole is formed at a center of a bottom surface (field unit attachment surface)  104 . The voice coil bobbin passes through the hole. The field unit  200  is bonded and/or screwed (or welded) to the field unit attachment surface  104  to coaxially arrange the through hole and the pole piece  206 . The frame portion  100  comprises an opening portion  106  which releases a back pressure when the diaphragm  300  generates a great-amplitude low tone.  
      At the frame portion  100 , the voice coil bobbin is positioned by the damper  306  such that the voice coil  304  is arranged in a magnetic gap between the pole piece  206  and the top plate  204  so as to be in no contact therewith. In addition, an outer peripheral portion of the edge  302  is bonded to a frame outer peripheral portion  102  such that the voice coil  304  does not rub against the pole piece  206  or the top plate  204  even if the diaphragm  300  vibrates at great amplitude. After that, a gasket  108  is attached to the frame outer peripheral portion  102  so as to catch an outer peripheral portion of the edge  302 .  
      The frame portion  100  can be formed of metal (iron plate, etc.) or plastic (thermoplastic resin such as PP, PE, PS, ABS, etc.) If the frame portion  100  is formed of metal, the attachment structure ( 400 - 404 ) is fixed to the frame portion  100  by screwing the field unit  200  on the field unit attachment surface  104  so as to catch a part of the attachment structure (i.e. flat plate portions between waveform spring structures  400  at right and left sides of the field unit  200  in  FIG. 1 ).  
      If the frame portion  100  is formed of plastic (thermoplastic resin) similarly to the attachment structure ( 400 - 404 ), the frame portion  100  and the attachment structure ( 400 - 404 ) can be molded with the same material (thermoplastic resin such as ABS, etc.) In this case, mold die is relatively complicated, but molding the frame and the attachment structure at low costs can be expected at mass production.  
      The frame outer peripheral portion  102  and the flanges  404  are structurally separated, irrespective of the materials of the frame portion  100  and the attachment structure ( 400 - 404 ), and irrespective of integral molding or separate formation of the frame portion  100  and the attachment structure ( 400 - 404 ).  
      In the speaker  10  shown in  FIG. 1 , the diaphragm  300  is supported by the edge  302  and damper  306  having spring characteristics and can conduct piston vibration in a longitudinal direction of the pole piece  206 . This vibration is generated by the voice coil  304  which flows a current in a direction orthogonal to a magnetic field formed at the field unit  200 . The diaphragm  300  can be vibrated by flowing a current to the voice coil  304 . The gasket  108  has effects of preventing peeling of the edge  302 , filling a gap between the frame portion  100  and the cabinet ( 12  in  FIG. 4  or  FIG. 5 ), and leading the acoustic energy (particularly low audio-frequency energy) generated at the diaphragm  300 . In this embodiment, the effects of filling the gap and restricting transmission of the vibration generated at the frame can be achieved by forming the gasket  108  with, for example, a sponge structure such as urethane foam.  
      In the structure of the speaker  10  shown in  FIG. 1 , the vibration energy generated at the voice coil  304  operates the diaphragm  300  such that the electric input is converted into acoustic energy. At this time, the diaphragm  300  vibrates with the frame portion  100  serving as an axis. For this reason, energy (reaction of diaphragm vibration) opposing the energy of the diaphragm  300  is generated at the frame  100 . Initially, this energy should escape to the cabinet, etc. ( 12  in  FIG. 4  or  FIG. 5 ) by the strictly fixed flanges  404 . In this case, however, the vibration energy propagates to the structure (display device, electronic circuit, etc.) including the cabinet and causes abnormal sounds and the other influences (for example, rocking a coil of a tuner, etc. and unbalancing the tuning, etc.).  
      To prevent this, the propagation can be decreased by using damping members (rubber bush, etc.) as the flanges  404 . However, if a loss amount of the damping members is too great, the vibration (particularly low-frequency vibration) of the diaphragm  300  is reduced (i.e. the movement of the frame  100  becomes great, the diaphragm  300  that should be originally vibrated is not operated by air resistance, instead the frame  100  is operated, and the energy is absorbed by the damping members). The amount of the acoustic conversion is thereby radically decreased.  
      If the damping members become hard (i.e. the loss amount is reduced), the propagation amount of the vibration to the cabinet becomes increased and the object of preventing the generation of abnormal sounds and the influence to the inner components (tuner coil, etc. in the above example) cannot be thereby achieved. Thus, the characteristics of the damping members need to be tuned in accordance with the performance of the speaker. As the tuning generally depends on the material characteristics, tuning the details is difficult.  
      On the other hand, in the structure shown in  FIG. 1  in which the spring structure  400  particularly has a large surface by plastic molding, the frame  100  is fixed if the diaphragm  300  is in a small amplitude. If the amplitude of the diaphragm  300  becomes great, the vibration of the frame  100  is absorbed by the spring structure  400  and the propagation of the vibration to the flanges  404  can be reduced. They can be controlled in accordance with the material (plastic, etc.) of the spring structure  400 , etc., the spring structure (number of waves, pitch of the waves, shape/size such as the height of waves, etc.), and the thickness and/or width of the spring structure, etc. Thus, an ideal vibration restriction effect can be produced in accordance with the specifications of the speaker  10 .  
      In addition, by the integral molding of plastic (thermoplastic resin) having not rigidity similarly to a metal but flexibility to a certain degree, it is also possible to reduce an influence from displacement in the relationship in attachment position between the cabinet and the gasket  108  which can be hardly provided thereat originally in this structure (i.e. the relationship between a position of an attachment boss  501  of the cabinet  12  and a position of an attachment  601  of the flange  404 , in an example shown in  FIG. 5 ). In other words, the speaker  10  having the structure shown in  FIG. 1  can be easily positioned when it is attached to the cabinet  12 , etc. (The spring structure can be flexibly moved. Even if the attachment aperture of the flange  404  is slightly displaced, the position of the attachment aperture can be easily shifted to the position of the attachment boss  501 , etc.)  
       FIG. 2  is a perspective view illustrating an outer appearance of the speaker  10  according to the embodiment of the invention. The speaker  10  is formed by integrally molding the flame  100  and flanges  404 , and the spring structure  400  provided therebetween with plastic (thermoplastic resin). In this case, the spring structure  400  supports the field unit  200  and the frame  100  against the flanges  404 , and the spring structure  400  is provided to be wide (such that stiffness in a direction orthogonal to the direction of vibration of the diaphragm  300  becomes great). The rolling of the flame  100  and the field unit  200  (i.e. wobbling in the lateral direction, at the vibration and the attachment) can be thereby restricted.  
      In addition, the faces of the wide spring structure  400  relieve the air vibration directly radiated from a back of the diaphragm  300  through an opening portion ( 106  in  FIG. 1  or  FIG. 3 ) formed on the frame  100 , relieve the influences of the air vibration on the back of the diaphragm to the other members (i.e. influences to electronic components inside the cabinet which are sensitive to the vibration), properly control the back pressure of the diaphragm  300 , and contributes to the restriction of the vibration at a great amplitude (i.e. Q damp at the lowest resonant frequency of the speaker).  
      In the structure of the speaker  10  shown in  FIG. 2 , the conventional speaker structure having the flanges in an extension of both sides of the frame is denied, the flanges  404  are separated from the frame  100  and bonded to the speaker body (field unit  200  and frame  100 ) via the spring structure  400 .  
      The field unit  200  and the frame  100  cannot be separated for the purpose of holding and vibrating the diaphragm  300 . Thus, the spring structure  400  is bonded to the structure ( 200  and  100 ) in which they are bonded, and the flanges  404  are formed on the side ends of the spring structure  400  to fix the speaker body to the cabinet, etc. This structure can be integrally molded by forming the frame  100 , the spring  400  and the flanges  404  by plastic molding.  
       FIG. 3  is an illustration of an effect of the frame opening portion  106  covered under feet of the spring structure in the structure of  FIG. 2 . The opening portion  106  is provided to form an escape route of the air on the back of the diaphragm when the diaphragm  300  vibrates.  
      If the opening portion  106  is not provided, the vibration of the diaphragm  300  is restricted by the air pressure of the space formed by the back face of the diaphragm and the frame  100  and, particularly, a great amplitude of the air vibration in a low audio frequency cannot be formed. In this embodiment, a cover (including the spring structure  400  and the feet  402 ) preparing an escape route of the air is formed over the opening portion  106  at a certain interval. Therefore, the opening portion  106  has an effect of relieving the direct radiation of the air vibration through the opening portion  106  and restricting the influences to the other members. In addition, the spring structure  400  and/or the feet  402  become obstacles to the airflow of the great-amplitude acoustic wave generated at a very great low-sound input. Thus, air control of certain degree is applied to the back face of the diaphragm  300  via the opening portion  106 , and an effect of reducing load on the damper  306  and the edges  302  supporting the diaphragm  300  can be thereby obtained.  
       FIG. 4  is an illustration of an outer appearance of the electronic device (slim-type digital TV equipped with the speaker  10  of  FIG. 1 ) according to the embodiment of the invention. In  FIG. 4 , a television receiver  11  (i.e. electronic device equipped with the speaker  10  according to the invention) mainly comprises a slim cabinet  12  formed in a substantially square shape as an device body, and a stand  13  which supports the cabinet  12  upright. A display area of an image display unit  14  composed of, for example, a flat liquid-crystal display panel (high-definition display panel: a precision device to which application of great vibration is undesirable), etc. is exposed on the front face of the cabinet  12 . A pair of speakers  10 , an operation portion  16 , a photoreceiver  18  for receiving operation information transmitted from a remote controller, etc. are arranged on the cabinet  12 .  
      The stand  13  is formed in a substantially thin box shape such that one of plains thereof, i.e. a bottom plate is placed on a predetermined table (not shown) installed horizontally. A support member projecting upwardly from a substantially central portion of a top plate opposite to the bottom plate placed on the table is coupled to a back face of the cabinet  12 . The stand  13  thereby supports the cabinet  12  upright. The stand  13  can contain a HDD unit (and/or DVD recorder unit)  20  to be described later. A plurality of operation buttons for controlling operations such as recording, reproduction, and stop, etc. of the HDD unit (and/or DVD recorder unit)  20  are arranged on a portion of the top plate of the stand  13  which projects to the front side from the position of the cabinet  12 . The HDD unit (and/or DVD recorder unit)  20  is also one of electronic devices to which application of great vibration from the speaker is undesirable. The television receiver comprises a tuner which receives minute-level high-frequency signals. This tuner is also an electronic device to which application of great vibration from the speaker is undesirable.  
       FIG. 5  illustrates an example of attachment of the speaker  10  of  FIG. 1  inside the device (cabinet  12 ) of  FIG. 4 . In the structure of the speaker  10 , there is a condition for the attachment to the cabinet  12  in the direction of gravity. The frame  100  cannot be strictly screwed on the cabinet  12 , from the viewpoint of the prevention of propagation of the vibration. In addition, as described with reference to  FIG. 1 , since the field unit  200  is composed of heavy components such as the magnet, top plate, poll piece, etc., the field unit  200  is comparatively heavy. For this reason, if the speaker of  FIG. 5  is attached to attachment bosses  501 ,  502 , . . . of the cabinet  12  via attachment apertures of the flanges  404  by screws  601  to  604 , the spring structure  400  needs not be inclined due to the weight of the field unit  200 .  
      The above requirement is satisfied by the manner of attachment shown in  FIG. 5  if the direction of gravity is a lateral direction of  FIG. 5 . In other words, in the speaker attached to the cabinet  12  as shown in  FIG. 5 , since the spring structure  400  of  FIG. 5  has great compliance at waveform portions thereof in the direction of vibration of the diaphragm  300  of  FIG. 1 , the acoustic vibration on the field unit attachment surface ( 104 ) of the frame  100  is rarely transmitted to the flanges  404 . In addition, the spring structure  400  has stiffness enough to support the weight of the speaker (at least the field unit  200 ) in a direction substantially orthogonal to the direction of vibration of the diaphragm  300  in  FIG. 1  (“substantially orthogonal” represents permitting a certain degree of αat 90°±α°: longitudinal direction of the spring structure  400  in  FIG. 5 ). Therefore, the field unit  200  is not inclined by its own weight. At this time, if the gasket  108  of  FIG. 1  slightly abuts on a part of the cabinet  12  of  FIG. 5 , the inclination occurs more hardly.  
      In addition, the spring structure  400  extending from the flange  404  to the attachment face ( 104 ) of the field unit  200  can easily be elastically deformed by great compliance at this part of the spring structure  400 . For this reason, even if screw apertures of the left flange  404  of  FIG. 5  are shifted to the right or left side from the positions of the attachment bosses  501  and  502  after the right flange  404  of  FIG. 5  is screwed at attachment bosses (not shown) of the cabinet  12  with screws  603  and  604 , this shift can easily be corrected (by shifting the positions of the screw apertures of the flange  404  to the positions of the bosses with a slight force).  
      In the above embodiment, the frame  100  is formed of plastic (thermoplastic resin) from the viewpoint of implementing integral molding with the spring structure  400 . However, if they are not integrally molded, the frame  100  may be formed of a metal frame of an iron plate, etc. In this case, the spring structure  400 , the feet  402  and the flanges  404  are produced in advance, separately from the frame  100 . When the field unit  200  is attached to the frame  100 , the middle part of right and left spring structures  400  may be sandwiched between the field unit attachment face  104  of the frame  100  and the field unit  200  and thereby fixed. The fixing method can be arbitrarily selected from bonding, welding, screwing, etc.  
      &lt;Advantages of the Embodiment of this Invention&gt; 
      &lt;1&gt;The frame and the flange, and the spring Structure provided therebetween can be integrally molded with plastic;  
      &lt;2&gt;The spring structure can restrict the rolling of the frame and the field unit (i.e. wobbling occurring at the vibration and attachment) by supporting the unit field and the frame against the attached flange and having great width;  
      &lt;3&gt;The face of the wide spring structure can relieve the direct radiation of air vibration from the back face of the diaphragm through the opening portion formed on the frame and can relieve influences of the air vibration from the back face of the diaphragm to the other units; and  
      &lt;4&gt;Since the structure &lt;3&gt;also contributes to controlling the back pressure of the diaphragm and restricting the vibration occurring at the great amplitude, the structure can bring about a loudness effect in low sound pressure output characteristics (the restriction of vibration is small at a low-volume level since the diaphragm amplitude is small, while the restriction of vibration is great at a high-volume level).  
      &lt;Short description of the speaker ( FIG. 1 ) according to the embodiment of the present invention&gt; 
      The flange  404  and the frame  100  are separated from each other, and the spring-like structure  400  is provided between the flange  404  and the coupling unit  104  on the speaker main unit ( 200  and  300 ) side to restrict propagation of the vibration occurring at the speaker main unit ( 200  and  300 ) to the flange  404  (speaker).  
      In the spring structure  400  provided between the flange  404  and the speaker main unit ( 200  and  300 ), the flange  404 , the feet  402 , the spring structure  400  and the frame  100  are integrally molded with plastic (speaker frame).  
      The present invention is not limited to the embodiment described above but the constituent elements of the invention can be modified in various manners at present or in future, on the basis of the technology available at that time, without departing from the spirit and scope of the invention. For example, the spring structure according to the invention is provided at the dynamic speaker using cone paper as the diaphragm in  FIG. 1 . However, the spring structure according to the invention is provided at the frame of the speaker using a flat diaphragm. In addition, the principle of operation of the diaphragm in the speaker to which the spring structure according to the invention can be applied may employ not only a force generated by flowing a current to a conductor in the magnetic field (dynamic speaker in a broad sense), but also Coulomb force (capacitor speaker) or a piezoelectric element (crystal speaker). However, since a dynamic speaker can output a greater vibration power, the spring structure according to the invention may be generally applied to the dynamic speaker from the viewpoint of restricting a harm caused by propagating the vibration of the speaker to the cabinet.  
      While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.