Patent Publication Number: US-8983104-B2

Title: Ring-shaped speaker having two voice coils and control member

Description:
PRIORITY CLAIM 
     This application claims the benefit of Japanese Patent Application No. 2010-257775, filed on Nov. 18, 2010, and which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a speaker which includes a ring-shaped vibrating member, and in particular, relates to a speaker which can prevent decrease of sound pressure and deterioration of sound quality when listening at diagonal front. 
     2. Description of the Related Art 
     Speakers respectively utilizing a ring-shaped vibrating member have been disclosed in Japanese Patent Application Laid-open 2006-100879, Japanese Patent Application Laid-open 2009-171475, and U.S. Pat. No. 6,320,972. 
     The ring-shaped vibrating member is unlikely to cause divisional resonance compared to a circular dome-shaped vibrating member and to cause sound distortion. Accordingly, such a vibrating member is often used for a tweeter which generates sound mainly in a treble range as being formed in relatively small diameter. 
     Here, in a speaker utilizing a ring-shaped vibrating member, a part of the vibrating member exists respectively at both sides as sandwiching a center line when viewing a sectional view sectioned at a face including the center line. Accordingly, a sound-generating portion is to be located respectively at both sides as sandwiching the center line. 
     Accordingly, when listening sound from diagonal front being angled against the center line, interference is more likely to occur between a sound wave from a sound-generating portion at one side and a sound wave from a sound-generating portion at the other side as sandwiching the center line. 
     Since treble sound waves have short wavelength and high directivity, sound pressure is more likely to be decreased and sound quality is more likely to be deteriorated when listening at diagonal front owing to interference between sound waves from the sound-generating portions located at both sides as sandwiching the center line. 
     In particular, in a speaker system for automobile use, tweeters are often attached at diagonal front positions from an occupant (e.g., pillar portions at both sides of a front window). Accordingly, influence due to the abovementioned sound wave interference is apt to be obtrusive. 
     SUMMARY 
     To address the above issues, the present invention provides a speaker with a ring-shaped vibrating member having a structure in which sound pressure decrease and sound quality deterioration are less likely to occur when listening at diagonal front against a center line. 
     A speaker of the present invention includes: 
     a vibrating member which is supported by a support body as being vibratile, a voice coil which applies vibration force to the vibrating member, and a magnetic field generating portion which provide magnetic field to the voice coil; 
     wherein the vibrating member is ring-shaped having an internal peripheral edge and an external peripheral edge and vibration force is applied from the voice coil at least to the external peripheral edge; 
     a ring-shaped control member is disposed at the front in a sound-generating direction of the vibrating member; and 
     pass space for sound waves to be generated from the vibrating member is formed respectively at an area surrounded by an internal peripheral end portion of the control member and an area outside an external peripheral end portion. 
     In the present invention, the pass space which is formed outside the external peripheral end portion of the control member is faced to the front in the sound-generating direction of the external peripheral edge of the vibrating member and the pass space which is surrounded by the internal peripheral end portion of the control member is faced to the front in the sound-generating direction of the internal peripheral edge of the vibrating member. 
     Further, in the present invention, the external peripheral end portion of the control member is located at the center side from the external peripheral edge of the vibrating member; and the internal peripheral end portion of the control member is located at the external peripheral side from the internal peripheral edge of the vibrating member. 
     In the speaker of the present invention, the ring-shaped control member is faced to the front of the ring-shaped vibrating member. When sound is listened from diagonal front being angled against the center line, a sound wave generated from a sound-generating portion at a position of the inclined side sandwiching the center line is more likely to be transmitted to a person through the pass space located outside the external peripheral end portion of the control member. However, propagation of a sound wave generated from a sound-generating portion at an opposite position to the inclined side is more likely to be suppressed. Accordingly, interference between sound waves from the bilateral sound-generating portions can be suppressed and sound pressure decrease and sound quality deterioration can be suppressed. 
     In contrast, when sound is listened at the front on the center line of the speaker, sound waves generated from the ring-shaped vibrating member are transmitted frontward through the pass space which is surrounded by the internal peripheral end portion of the control member, so that the sound waves are more likely to be transmitted to a person without causing phase difference. 
     In the present invention, it is preferable that an inclined side face be formed at the external peripheral end portion of the control member to be apart gradually from a center as getting away frontward in the sound-generating direction from the vibrating member. 
     With the above structure, the sound waves generated from the ring-shaped vibrating member are more likely to be guided to diagonally frontward as being guided by the inclined side face. Accordingly, when listening from the front being diagonal against the center line, decrease of the sound pressure level is easy to be suppressed. 
     In the present invention, it is preferable that an opposite inclined face be formed at an opposite portion of the control member being faced to the vibrating member so that distance against the vibrating member is increased gradually as getting away from the center. 
     In the above structure, resonance at the opposite portion between the vibrating member and the control member is less likely to occur, so that sound quality deterioration caused by the resonance is easy to be prevented. 
     In the present invention, the internal peripheral edge of the vibrating member is fixed to the support body; and the external peripheral edge has degree of freedom as being supported by the support body via a damper member. Alternatively, both of the internal peripheral edge and the external peripheral edge of the vibrating member are supported by the support body respectively via a damper member; and vibration force is separately applied to the internal peripheral edge and the external peripheral edge from separate voice coils. 
     A speaker of the present invention utilizes a ring-shaped vibrating member and is likely to prevent occurrence of sound pressure decrease and sound quality deterioration when listening sound from diagonal front. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view of a speaker of a first embodiment of the present invention; 
         FIG. 2  is a front view of the speaker of the first embodiment; 
         FIG. 3  is a longitudinal sectional view of a speaker of a second embodiment of the present invention; and 
         FIG. 4  is a graph indicating an effect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A speaker  1  of the first embodiment illustrated in  FIGS. 1 and 2  is used mainly for high-pitched tones. 
     The speaker  1  includes a magnetic field generating portion  10 . The magnetic field generating portion  10  includes a magnetic-material-made lower yoke  11  of which center part is concavely formed, a disc-shaped magnet  12  which is disposed in the concave portion of the lower yoke  11 , and a disc-shaped upper yoke  13  which is disposed on the magnet  12 . The magnet  12  is magnetized in the direction so that polarities of a lower face  12   a  contacted to the lower yoke  11  and an upper face  12   b  contacted to the upper yoke  13  are to be opposite. 
     As illustrated in  FIGS. 1 and 2 , a line passing through the center of the disc-shaped upper yoke  13  is the center line O of the speaker  1 . 
     An upper internal peripheral face  11   a  of the lower yoke  11  is cylindrical and an external peripheral face  13   a  of the upper yoke  13  is cylindrical, as well. Then, a magnetic gap G is formed at an opposed part between the upper internal peripheral face  11   a  and the external peripheral face  13   a.    
     An outer support body  15  formed of non-magnetic material such as synthetic resin and non-ferrous metal is fixed to an upper external peripheral part of the lower yoke  11 . An inner support body  16  formed of non-magnetic material such as synthetic resin and non-ferrous metal is fixed to a center part of an upper face of the upper yoke  13 . 
     A vibrating member  21  is disposed between the outer support body  15  and the inner support body  16 . The vibrating member  21  is formed of soft sheet material of cloth, nonwoven fabric, paper, resin film or combined material thereof. 
     The vibrating member  21  being ring-shaped in a front view as illustrated  FIG. 2  includes an internal peripheral edge  21   a  and an external peripheral edge  21   b . The vibrating member  21  has a protruded shape as a center part between the internal peripheral edge  21   a  and the external peripheral edge  21   b  is protruded frontward. 
     The internal peripheral edge  21   a  of the vibrating member  21  is fixed to the inner support body  16 . A damper member  22  is connected to the external peripheral edge  21   b  of the vibrating member  21 . The damper member  22  is fixed to the external support body  15 . As illustrated in  FIG. 1 , the damper member  22  is attached between the external peripheral edge  21   b  of the vibrating member  21  and the outer support body  15  so that the sectional shape thereof is curved. The damper member  22  may be integrally formed with the vibrating member  21  as being extended therefrom with the same material as that of the vibrating member  21 . Alternatively, it is also possible that the damper member  22  is formed of different sheet material from that of the vibrating member  21  and is jointed to the external peripheral edge  21   b.    
     The external peripheral edge  21   b  of the vibrating member  21  can be moved back and forth as being supported by the damper member  22 . Since the internal peripheral edge  21   a  is fixed to the inner support body  16 , degree of freedom of the vibrating member  21  is the highest at the external peripheral edge  21   b . Further, since the damper member  22  is vibrated back and forth together with the vibrating member  21 , the damper member  22  also functions as a part of the vibrating member  21 . 
     As illustrated in  FIG. 1 , a cylindrical bobbin  23  is fixed to the external peripheral edge  21   b  of the vibrating member  21 . A voice coil  24  is attached to the bobbin  23  and the voice coil  24  is inserted to the magnetic gap G. 
     An equalizer  30  is placed at the front of the speaker  1 . The equalizer  30  is formed of non-magnetic material such as synthetic resin and non-ferrous metal. The equalizer  30  has a ring-shaped attaching portion  31  at the external peripheral part thereof as being fixed to a front end part of the external support body  15 . As illustrated in  FIG. 2 , the equalizer  30  has a plurality of support ribs  33  integrally extending toward the center line O from the attaching portion  31 . A ring-shaped control member  32  is integrally formed at distal portions of the respective support ribs  33 . 
     As illustrated in  FIG. 1 , the ring-shaped control member  32  is faced to the front of a sound-generating side of the ring-shaped vibrating member  21  as being spaced therebetween.  FIG. 1  illustrates a cylindrical internal peripheral vertical face V 1  extending in parallel to the center line O frontward in the sound-generating direction from the internal peripheral edge  21   a  of the vibrating member  21  and a cylindrical external peripheral vertical face V 2  extending in parallel to the center line O frontward from the external peripheral edge  21   b  of the vibrating member  21 . 
     An external peripheral end portion  34  of the control member  32  is placed to the inner side being closer to the center line O than the external peripheral vertical face V 2 . An internal peripheral end portion  35  of the control member  32  is placed to the external peripheral side as being further apart from the center line O than the internal peripheral vertical face V 1 . 
     A ring-shaped outer pass space  38  through which a sound wave generated when the vibrating member  21  is vibrated passes is formed between the external peripheral end portion  34  of the control member  32  and the attaching portion  31 . A circular inner pass space  37  through which a sound wave generated by the vibration of the vibrating member  21  passes frontward is formed at an area surrounded by the internal peripheral end portion  35  of the control member  32 . The outer pass space  38  is faced to the front of the external peripheral edge  21   b  of the vibrating member  21  and the inner pass space  37  is faced to the front of the internal peripheral edge  21   a  of the vibrating member  21 . 
     An inclined side face  34   a  is formed at the external peripheral end portion  34  of the control member  32 . The inclination direction S 1  of the inclined side face  34   a  is the direction being apart gradually from the center line O as approaching frontward in the sound-generating direction from the vibrating member  21 . Further, an internal peripheral face  31   a  of the attaching portion  31  of the equalizer  30  is faced to the inclined side face  34   a . The internal peripheral face  31   a  is also inclined to the same direction as the inclined side face  34   a.    
     The outer pass space  38  is the space at which the inclined side face  34   a  and the internal peripheral face  31   a  are faced to each other. The space extends in the direction to be apart gradually from the center line O as getting away from the vibrating member  21 . Owing to the outer pass space  38 , a sound wave generated at the vicinity of the external peripheral edge  21   b  of the vibrating member  21  is more likely to be guided in the direction being apart from the center line O (i.e., the D 1  direction). In addition, the sound wave generated at the vicinity of the external peripheral edge  21   b  is more likely to be disturbed from being propagated in the direction toward the center line O (i.e., the D 2  direction). 
     Since the outer pass space  38  has the inclined side face  34   a , opening area of a part faced to the vibrating member  21  is widened. In the present specification, the sentence of “the outer pass space  38  is faced to the front in the sound-generating side of the external peripheral edge  21   b  of the vibrating member  21 ” denotes that the opening portion of the outer pass space  38  oriented to the vibrating member  21  is faced to the external peripheral edge  21   b . Under the above conditions, the external peripheral end portion  34  of the control member  32  may be placed at the external peripheral side from the external peripheral vertical face V 2 . Here, when the external peripheral end portion  34  is placed at the center line O side from the external peripheral vertical face V 2  as illustrated in  FIG. 1 , the sound wave generated by the vibration at the vicinity of the external peripheral edge  21   b  of the vibrating member  21  is more likely to be propagated frontward along the external peripheral vertical face V 2 . Accordingly, a sufficient sound pressure level is more likely to be ensured when sound is listened at the front on the center line O. 
     As illustrated in  FIG. 1 , an opposite inclined face  36   a  is formed at an opposite portion  36  of the control member  32  being faced to the vibrating member  21 . The inclination direction S 2  of the opposite inclined face  36   a  is set so that opposed distance to the vibrating member  21  is gradually enlarged as getting away from the center line O. Owing to forming of the opposite inclined face  36   a , the sound pressure generated by the vibration of the vibrating member  21  is effectively transmitted frontward through the outer pass space  38 . 
     Further, in the case that the opposite inclined face  36   a  is formed, occurrence of unnecessary resonance within a small space between the opposite portion  36  and the vibrating member  21  is more likely to be prevented. 
     An inclined face  35   a  is formed at the internal peripheral end portion  35  of the control member  32 . The inclined face  35   a  is formed in the direction to be gradually apart from the center line O as getting away frontward from the vibrating member  21 . Owing to forming of the inclined face  35   a , sound pressure to be transmitted frontward from the inner pass space  37  is more likely to be spread frontward. Further, in the case that the inclined face  35   a  is formed, occurrence of unnecessary resonance at the inner pass space  37  is more likely to be prevented, so that deterioration of sound quality due to resonance is more likely to be prevented. 
     In the speaker  1 , when a sound signal is provided to the voice coil  24 , vibration force is applied to the external peripheral edge  21   b  of the vibrating member  21  via the bobbin  23 . Since degree of freedom of the vibrating member  21  is the highest at the external peripheral edge  21   b , the external peripheral edge  21   b  is easy to be vibrated when a high frequency sound signal is applied. Accordingly, when treble sound is generated, sound pressure becomes the largest at the sound-generating portion of an area α. 
     When sound is listened on the center line O in front of the speaker  1 , treble sound pressure generated at the area α is transmitted frontward as passing through the outer pass space  38  along the external peripheral vertical face V 2 . Accordingly, when listening on the center line O, treble sound pressure is high and sound quality is favorable with less sound distortion. 
     In contrast, when sound is listened in an angled direction (e.g., the D 1  direction and the D 2  direction) being deviated from the center line O, a treble sound wave generated from the area α at the right side of  FIG. 1  is more likely to be listened for a person as being oriented in the D 1  direction as passing through the outer pass space  38 . On the other hand, a treble sound wave generated from the area α at the left side of  FIG. 1  is less likely to be transmitted in the D 2  direction as being disturbed by the control member  32  when being oriented in the D 2  direction. A treble sound wave has high directivity. Accordingly, since the sound at the right side is preferentially listened and the sound at the left side is hard to be listened, treble sound waves generated from the separated areas α, α at the bilateral sides is less likely to be interfered. Therefore, decrease of treble sound pressure when listening at diagonal front can be suppressed and deterioration of sound quality can be improved. 
     Further, since the internal peripheral edge  21   a  of the vibrating member  21  is fixed to the inner support body  16 , an area β being a sound-generating portion close to the internal peripheral edge  21   a  has low degree of freedom. Compared to the area α, sound pressure of a relatively low range is more likely to be formed in the area β. Directivity of sound waves of the relatively low range is not very strong and wavelength thereof is relatively long. Accordingly, sound waves capable of being transmitted frontward as passing through the internal pass space  37  from the area β are less likely to be interfered. Owing to wide opening of the inner pass space  37  in front of the area β, the sound pressure level of the relatively low range can be maintained at high. As a result, satisfactory sound quality can be obtained in a wide frequency range. 
     In a speaker  101  of the second embodiment illustrated in  FIG. 3 , a magnetic-field generating portion  110  includes a lower yoke  111 , a ring-shaped magnet  112 , and a ring-shaped upper yoke  113 . An external peripheral side magnetic gap G 1  and an internal peripheral side magnetic gap G 2  are formed between the lower yoke  111  and the upper yoke  113 . 
     Regarding a ring-shaped vibrating member  121 , an internal peripheral edge  121   a  thereof is supported by an inner support body  116  via a damper member  122   a  and an external peripheral edge  121   b  is supported by an outer support body  115  via a damper member  122   b . A bobbin  123   a  is attached to the internal peripheral edge  121   a  of the vibrating member  121 . A voice coil  124   a  attached to the bobbin  123   a  is inserted to the internal peripheral side magnetic gap G 2 . A bobbin  123   b  is attached to the external peripheral edge  121   b  of the vibrating member  121 . A voice coil  124   b  attached to the bobbin  123   b  is inserted to the external peripheral side magnetic gap G 1 . 
     An equalizer  30  having the same structure as illustrated in  FIG. 1  is attached to the outer support body  115 . The equalizer  30  includes an attaching portion  31 , a control member  32 , an outer pass space  38  and an inner pass space  37  which are integrally formed therewith. 
     Further, a cone-shaped center equalizer  130  is attached to the inner support body  116 . The center equalizer  130  is placed at the inner pass space  37 . 
     In the speaker  101 , since vibration force is applied to the internal peripheral edge  121   a  and the external peripheral edge  121   b  of the vibrating member  121  by the two voice coils  124   a ,  124   b , the sound pressure level is heightened. With the speaker  101 , the ring-shaped control member  32  is faced to the front of the vibrating member  121  as well. Accordingly, when sound is listened at the front being diagonal against the center line O, it is possible to suppress interference of sound waves generated from the external peripheral edge  121   b  of the vibrating member  121 . 
     Examples 
       FIG. 4  is a graph of comparison between sound pressure levels of the speaker of the embodiment of the present invention and a speaker of the related art. 
     The speaker  1  of the embodiment has the structure as illustrated in  FIG. 1 . The external peripheral edge  21   b  of the vibrating member  21  is 25 mm in diameter. A speaker of the comparison example is the same as the speaker of the embodiment while the equalizer  30  is detached. 
     A high frequency signal of 1 watt was applied to the voice coil  24 . The pressure levels were measured at a position being apart from the vibrating member  21  by 1 meter at diagonal front angled by 20 degrees from the center line as varying the frequency. 
     In  FIG. 4 , the horizontal axis denotes frequency and the vertical axis denotes a sound pressure level. A result of the embodiment is indicated by (a) and a result of the comparison example is indicated by (b). According to  FIG. 4 , it is perceptible that decrease of the sound level of the embodiment is suppressed while the sound level of the comparison example is decreased at the vicinity of 10 kHz. 
     Although preferred embodiments have been described in detail, the present invention is not limited to these specific embodiments. Rather, various modifications and changes can be made without departing from the scope of the present invention as described in the accompanying claims. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.