Patent Publication Number: US-2006013431-A1

Title: Damping system

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a damping system for damping vibration of a frame, on which a speaker is mounted, caused by the speaker.  
      2. Description of the Related Art  
      Generally, a speaker to be mounted on a door panel of a car includes a speaker unit having a vibration member and a magnetic circuit for generating sounds by vibrating the vibration member, and a case receiving the speaker unit. The vibration member includes a voice coil to be disposed in a later-described magnetic gap of the magnetic circuit, and a vibrating plate to vibrate freely together with the voice coil.  
      The magnetic circuit includes a yoke plate formed into a ring shape with a magnetic material and connected through a damper with the vibrating plate, a magnet mounted on the yoke plate, and a yoke made of the magnetic material and mounted on the magnet for forming the magnetic gap between the yoke plate to generate a magnetic force for driving (vibrating) the vibrating plate.  
      The case is formed into a blind end tube shape having a bottom wall and a tube extending from an outer edge of the bottom wall. The case receives the speaker unit so as to expose the vibrating plate out of the case. The case is fixed on the yoke of the magnetic circuit, and mounted on the door panel.  
      The speaker structured as mentioned above generates sounds corresponding to sound current by supplying the sound current to the voice coil to vibrate the voice coil and the vibrating plate. In the speaker by prior art, sound current is supplied into the voice coil to vibrate the voice coil for generating sounds. Thereby, a reaction against the vibration of the coil vibrates the yoke and the case. By the vibration of the case, the door panel is vibrated. Unexpected sounds generated by the vibration of the door panel are added on sounds generated by the speaker unit. Thereby, the speaker unit cannot securely play back sounds, especially bass sounds.  
      In the usual damping system, a damping material, such as asphalt, is pasted on a whole surface of the door panel for damping the vibration of the door panel quickly.  
      Objects to be Solved  
      Since the aforesaid damping system by prior art is by pasting the damping material like asphalt on the whole surface of the door panel, weight of the door panel, that is, weight of the car is increased. Furthermore, since the damping system by prior art is by pasting the damping material having relative large mass on the door panel, vibration in a range of relative high frequency can be attenuated easily, but vibration in a range of relative low frequency cannot be attenuated. Thus, the damping system by prior art cannot eliminate securely unexpected sounds by vibration of the door panel.  
      To overcome the above problem, one object of this invention is to provide a damping system, which can perform good acoustic characteristics of a speaker.  
     SUMMARY OF THE INVENTION  
      How to Attain the Object  
      In order to attain the objects, a damping system according to claim  1  of this invention is specified by having a frame, a speaker being mounted on the frame, and a damping device being mounted on the frame, and by that the damping device includes an elastic member mounted on the frame and a mass mounted on the elastic member.  
     DESCRIPTION OF THE BEST MODE  
      One embodiment of a damping system according to this invention will be described herein. In the damping system according to this embodiment, to mount the damping device having the elastic member and the mass mounted on the elastic member on the frame where the speaker is mounted, vibration of the frame can be attenuated when the frame is vibrated. Thereby, good acoustic characteristics of a speaker can be performed.  
      According to this invention, the damping device can include a plurality of units.  
      Furthermore, according to this invention, a natural frequency of the damping device can be made equal to a natural frequency of the mounting portion.  
      The above and other objects and features of this invention will become more apparent from the following description taken in conjunction with the accompanying drawings.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a damping system of one embodiment according to this invention;  
       FIG. 2  is a cross-sectional view of a speaker of the damping system shown in  FIG. 1 ;  
       FIG. 3A  is a perspective view of a damping device of the damping system shown in  FIG. 1 ;  
       FIG. 3B  is a cross-sectional view taken along line  3 B- 3 B in  FIG. 3A ;  
       FIG. 4  is a cross-sectional view showing one condition in vibration of the inner panel of the damping system shown in  FIG. 3B ; and  
       FIG. 5  is a cross-sectional view showing the other condition in vibration of the inner panel of the damping system shown in  FIG. 3B . 
    
    
     DESCRIPTION OF EMBODIMENTS  
      The first embodiment according to the present invention will be described with reference to  FIGS. 1-5 . A damping system  1  according to the first embodiment includes a door panel  40  structuring a car body of a vehicle, a speaker  2  mounted on the door panel  40 , and a plurality of damping devices  5  mounted on the door panel  40 .  
      The door panel  40  includes an outer panel  41  and an inner panel  42  to be mounted on the outer panel  41 . The outer and inner panels  41 ,  42  are made by roll-forming a steel sheet metal. A door glass (not shown) is received between the outer and inner panels  41 ,  42 . The door panel  40  is mounted on the car body with a hinge, and supported rotatably by the hinge. To rotate the door panel  40  by the hinge, a car room is opened and closed.  
      On the inner panel  42 , the speaker  2  and electronic devices (not shown), such as a motor for a power regulated window and an actuator for door locking are mounted. The inner panel  42  is provided with a plurality of holes  27  for receiving the speaker  2  and electronic devices, such as a motor for a power regulated window and an actuator for door locking. The inner panel  42  corresponds to a frame described in an aspect of the present invention.  
      The inner panel  42  vibrates along directions P 1 , P 2  parallel to an axis of the speaker  2  when the speaker generates sounds as describing later. Resonance frequencies of vibration along the directions P 1 , P 2  of the inner panel  42  are different from each other by depending on positions thereof. Generally, the natural frequency becomes smaller corresponding to approaching to the center of the inner panel  42 , and the natural frequency becomes larger corresponding to approaching to an outer edge of the inner panel  42 .  
      The natural frequency in this specification includes a general natural frequency of each body, such as the damping device  5  and the inner panel  42 , and an “n” dimension natural frequency at an “n” dimension vibration mode of the each body, such as the damping device  5  and the inner panel  42  (n is natural number)  
      The inner panel  42  is provided at the surface thereof with a plurality of mounting portions  43 . The mounting portions  43  are vibrated by sounds generated by the speaker  2 . Thereby, at least two resonance frequencies at the mounting portions  43  are different from each other. The damping devices  5  are mounted respectively at mounting portions  43 .  
      The speaker  2  has a speaker unit  3  and a case  4  as shown in  FIG. 2 . The speaker unit  3  includes a vibrating member  6  and a magnetic circuit  7  for vibrating the vibrating member  6  to generate sounds.  
      The vibrating member  6  has a voice coil  8 , a voice coil bobbin  9 , a vibrating plate  10 , a damper  11  and an edge ring  12 . The voice coil  8  is disposed coaxially with a later-described yoke  15  and a yoke plate  17  of the magnetic circuit  7 , and within a later-described magnetic gap G of the magnetic circuit  7 . Sound current is supplied to the voice coil  8 .  
      The voice coil bobbin  9  is formed into a cylindrical shape. The voice coil bobbin  9  is disposed coaxially with the yoke  15 , the yoke plate  17  and the voice coil  8 . One end of the voice coil bobbin  9  in an axial direction thereof is inserted in the magnetic gap G. The voice coil  8  is mounted on an outer wall of the one end. The coil bobbin  9  is supported to move freely along an axis P of the yoke  15  (shown with a long dashed short dashed line in  FIG. 2 ).  
      The vibrating plate  10  has a center cap  13  with a cross-section of an arc shape and a plan view of a circular disk shape, and a cone  14  with a side view of a circular truncated cone and a plan view of a ring shape. The cone  14  is disposed coaxially with the center cap  13 , that is, the yoke  15 . An inner edge of the cone  14  is connected with the other end of the voice coil bobbin  9 . An outer edge of the center cap  13  is connected with the cone  14  to cover the voice coil bobbin  9 .  
      The damper  11  is formed into a thin plate ring shape in plan view. An inner edge of the damper  11  is connected with the voice coil bobbin  9 , and an outer edge thereof is connected with an inner surface of the case  4 . The damper  11  allows the voice coil bobbin  9  to vibrate along the axis P. The damper  11  attenuates gradually the vibration of the voice coil bobbin  9 .  
      The edge ring  12  is formed into a thin plate ring shape in plan view. An inner edge of the edge ring  12  is connected with an outer edge of cone  14 , and an outer edge thereof is connected with an outer surface of the case  4 . The edge ring  12  allows the voice coil bobbin  9  to vibrate along the axis P. The edge ring  12  attenuates gradually the vibration of the voice coil bobbin  9 .  
      The magnetic circuit  7  includes the yoke  15  made of magnetic material (paramagnetic material or ferromagnetic material), a magnet  16 , and the yoke plate  17  made of magnetic material (paramagnetic material or ferromagnetic material). The yoke  15  has integrally a bottom plate  18  with a circular disk shape and a cylindrical center pole  19  projecting coaxially with the bottom plate  18  from the center of the bottom plate  18 . An outer diameter of the bottom plate  18  is larger than that of the center pole  19 . The yoke  15  is disposed on condition that a far-side end of the center pole  19  from the bottom plate  18  penetrates into the one end of the voice coil bobbin  9 .  
      The magnet  16  is formed into a circular ring shape. The magnet  16  is a permanent magnet or an electromagnet to be magnetized by direct current. The magnet  16  is stacked on the bottom plate  18  of the yoke  15  to locate the center pole  19  of the yoke  15  within a center hole of the magnet  16 .  
      The yoke plate  17  is formed into a circular ring shape. The yoke plate  17  is stacked on the magnet  16  so as to locate the center pole  19  of the yoke  15  within a center hole of the yoke plate  17 . The yoke  15 , the magnet  16  and the yoke plate  17  are fastened to an inner edge of the case  4  with bolts  34 . The yoke  15 , the magnet  16  and the yoke plate  17  are disposed coaxially with each other. An outer surface of the center pole  19  of the yoke  15  and an inner surface of the yoke plate  17  have a distance from each other.  
      According to a structure as mentioned above, the magnetic circuit  7  is formed as an external magnet type. In the magnetic circuit  7 , the magnetic gap G for generating magnetic force to drive (vibrate) the vibrating plate  10  in cooperation with the voice coil  8  is formed between the outer surface of the center pole  19  of the yoke  15  and the inner surface of the yoke plate  17 .  
      According to the speaker unit  3  structured as mentioned above, by supplying sound current into the voice coil  8 , the voice coil  8  supported within the gap G vibrates along the aforesaid axis P corresponding to the sound current. Thereby, the voice coil bobbin  9  supporting the voice coil  8  vibrates along the axis P together with the center cap  13  and the cone  14  of the vibrating plate  10 . Therefore, the center cap  13  and the cone  14  of the vibrating plate  10  generate sounds corresponding to the sound current. Thus, the magnetic circuit  7  vibrates the vibrating plate  10 , that is, the vibrating member  6  for generating sounds.  
      The case  4  is formed into a thin plate circular truncated cone shape in side view and a circular ring shape in plan view. The case  4  is mounted on the yoke plate  17 , the magnet  16  and the yoke  15  so as to stack the inner edge of the case  4  on the yoke plate  17 . An outer edge of the case  4  is fixed through the edge ring  12  and a gasket  20  on the inner panel  42 . In other words, The gasket  20  and the edge ring  12  are clamped between the inner panel  42  and the outer edge of the case  4 . The gasket  20  is made of an elastic material, such as rubber, for restraining transmission of vibration of speaker  2  to the inner panel  42 .  
      The aforesaid speaker  2  is inserted into the hole  27  to make the axis P perpendicular to a surface of the inner panel  42  and expose the vibrating plate  10 , and fixed on the inner panel  42 . Therefore, the axis P of the speaker  2  and an axis of the damping device  5  are parallel to each other.  
      A plurality of damping devices  5  is mounted respectively at the mounting portions  43  on the surface of the inner panel  42 . A natural frequency of each damping device  5  when a later-described mass  36  vibrates relatively against an elastic member  35  along the axis P is equalized with a first natural frequency of each mounting portion  43 , where each damping device  5  is mounted, vibrating along the axis P. Thus, the natural frequency of each damping device  5  is equal to the natural frequency of each mounting portion  43  where each damping device  5  is mounted.  
      By adjusting each outer diameter and thickness of the elastic member  35  and the mass  36 , the natural frequency of each damping device  5  is equalized with the natural frequency of each mounting portion  43 .  
      The damping device  5  has the elastic member  35  made of an elastic material such as rubber and the mass  36  as shown in  FIGS. 3A, 3B . The elastic member  35  is mounted on the aforesaid mounting portion  43 . The elastic member  35  can be made of silicon rubber. The elastic member  35  is formed into a circular disk shape. The elastic member  35  is stacked on the mounting portion  43  and mounted at the mounting portion  43 .  
      The mass  36  is formed into a thin circular disk shape. The mass  36  is stacked on the elastic member  35  and mounted thereon. In this embodiment, the mass  36  is made of a material which specific gravity is larger than that of aluminum alloy as a material for the case  4 .  
      In the damping system  1  structured as mentioned above, when the vibrating plate  10  is vibrated along the axis P by supplying the sound current into the voice coil  8  of the speaker unit  3  in the speaker  2 , the yoke  15  vibrates along the axis P oppositely against the vibration of the vibrating plate  10 . Therefore, vibration of the yoke  15  is transmitted through the case  4  to the inner panel  42 , so that each mounting portion  43  of the inner panel  42  vibrates oppositely against the vibrating plate  10 .  
      Thereby, the mass  36  is maintained at the present position by inertia. The mass  36  vibrates oppositely against the vibration of the inner panel  42  and relatively with the inner panel  42 . The natural frequency of the damping device  5  is equal to the natural frequency of the mounting portion  43 . Therefore, the mass  36  of the damping device  5  vibrates against the inner panel  42  oppositely to the vibration of the inner panel  42  at the same frequency as the vibration of the inner panel  42 . The elastic member  35  is provided between the mass  36  and the inner panel  42 , so that the elastic member  35  pushes the inner panel  42  to the mass  36  and pulls the inner panel  42  from the mass  36  oppositely against the vibration of the inner panel  42 .  
      When the mounting portion  43  of the inner panel  42  moves along the arrow P 1  shown in  FIG. 4 , the elastic member  35  pushes the inner panel  42  along the arrow P 2  opposite to the arrow P 1  by the inertia of the mass  36 . When the inner panel  42  moves along the arrow P 2  shown in  FIG. 5 , the elastic member  35  pulls the inner panel  42  along the arrow P 1  opposite to the arrow P 2  by the inertia of the mass  36 .  
      Thus, the vibration of the inner panel  42 , that is, the case  4  and the magnetic circuit  7  generated by reaction of the vibration of the vibrating plate  10  can be attenuated rapidly by the damping device  5 .  
      In this embodiment, the damping device  5  having the elastic member  35  and the mass  36  is provided at the inner panel  42  where the speaker  2  is mounted. When the speaker  2  vibrates the inner panel  42 , the mass  36  is maintained at the present position by its inertia. Thereby, the mass  36  moves relatively against the inner panel  42  in an opposite direction of the vibration of the inner panel  42 . Since the mass  36  and the inner panel  42  are connected together by the elastic member  35 , the inner panel  42  is pushed to the mass  36  and pulled from the mass  36  through the elastic member  35  in the opposite direction of the vibration. Therefore, when the inner panel  42  is vibrated, the vibration of the inner panel  42  can be attenuated rapidly. Unexpected sound caused by the vibration of the inner panel  42  can be prevented from adding on the sound generated by the speaker  2 , so that good sound characteristics can be given.  
      The plurality of damping devices  5  is provided, so that the vibrations at positions of the inner panel  42  can be attenuated rapidly and securely.  
      Since the natural frequency of each damping devices  5  is equal to the natural frequency of each mounting portion  43  of the inner panel  42 , the mass  36  of the damping device  5  vibrates relatively against the inner panel  42  oppositely to the mounting portion  43  at the same frequency as the vibration of each mounting portion  43  when the mounting portion  43  of the inner panel  42  vibrates. Thereby, the vibrations of the inner panel  42  can be attenuated rapidly and securely. Therefore, unexpected sound caused by the vibration of the inner panel  42  can be prevented from adding on the sound generated by the speaker  2 , so that good sound characteristics can be given.  
      In the embodiment mentioned above, rubber is used as the elastic member  35 . Thereby, comparing with use of a spring as the elastic member  35 , the elastic member  35  can be prevented from elastic deformation thereof by moving the mass  36  down by gravity. Since the rubber is used as the elastic member  35 , weight of the elastic member can be reduced. The elastic member  35  can be easily formed (manufactured) and easily mounted on the inner panel  42  and the mass  36 .  
      In the embodiment mentioned above, the damping device  5  is mounted on the inner panel  42 . The door panel  40  structured by the inner panel  42  is designed without attenuation of the vibration of case  4  of the speaker  2 , so that good sound characteristics can be given by attenuating the vibration of the case  4  of the speaker  2 .  
      In the embodiment mentioned above, the speaker  2  is mounted on the inner panel  42  of the door panel of the car. According to the present invention, the speaker  2  and the damping device  5  can be mounted on various panels such as a rear tray of the car, and can be mounted on various boxes installed on a floor. According to the present invention, a spring can be used as the elastic member  35 . It is effective that any one of resonance frequencies of the damping devices  5  is equalized to any one of resonance frequencies of the mounting portions  43 .  
      According to the aforesaid embodiment, following damping system  1  can be provided.  
      Type 1: A damping system  1  includes an inner panel  42 , a speaker  2  mounted on the inner panel  42 , and a damping device  5  mounted on the inner panel  42 , and the damping device  5  includes an elastic member  35  mounted on the inner panel  42  and a mass  36  mounted on the elastic member  35 .  
      Type 2: The damping system  1  according to type 1, wherein the damping device  5  includes a plurality of units.  
      Type 3: The damping system according to type 2, wherein respective mounting portions  43  of the plurality of damping devices are simultaneously vibrated by the speaker  2 , and a natural frequency of each unit  5  is equal to that of the mounting portion  43  of each unit of the damping device  5 .  
      The above mentioned embodiments are only typical examples according to the present invention, and the invention is not limited to the embodiments. Various modifications can be made without departing from the scope of the present invention. Incidentally, the contents of Japanese Patent Application No. 2004-166953 are hereby incorporated by reference.