Patent Publication Number: US-8111868-B2

Title: Speaker device

Description:
TECHNICAL FIELD 
     The present invention relates to a dynamic type speaker provided with a drive cone and a diaphragm which are integrally driven by a voice coil and, more particularly, to a speaker device in which the rigidity of the diaphragm in a vibration direction can be further enhanced, and further, the durability of each of the drive cone and the diaphragm can be enhanced. 
     BACKGROUND ART 
     In a dynamic type speaker, a voice coil bobbin having a voice coil wound therearound is basically fixed at an inner circumferential edge of a cone diaphragm whereas a peripheral edge of the diaphragm is secured to a frame via an edge portion. Moreover, a circumferential edge of a damper is fixed to the voice coil bobbin whereas a peripheral edge of the damper is secured to the frame. That is to say, the edge portion or the damper constitutes a suspension in a vibration system such as the diaphragm or the voice coil. 
     A deep bass reproducing speaker which is called a woofer or a sub woofer for use in, for example, a vehicle-mounted audio system is configured such that a satisfactory sound pressure level in a bass region can be ensured by taking a great amplitude stroke of the diaphragm since there is a limitation on a diameter of a diaphragm. 
     The damper, in particular, constituting the above-described suspension in the vibration system need be equipped with a function for ensuring an amplitude stroke equal to that at the edge portion without any contact of the voice coil with a pole piece or a yoke constituting a magnetic gap. 
     As a consequence, it is difficult to give great compliance to the damper. There arises a problem of degradation of power linearity caused by the occurrence of non-linearity of a movable load in the damper in the speaker in which the great amplitude stroke is ensured. In addition, there is carried a problem that a mechanical fatigue of the damper occurs earlier than that of the edge portion. 
     In the meantime, a corrugation damper having a bellows shape in a cross section is frequently used as the damper in order to ensure the compliance. However, there arises a problem that peculiar vibrations or scratchy noises occur due to deformation between adjacent bellows accompanied with an amplitude motion. This prominently occurs in the speaker having the great amplitude stroke of the diaphragm, as described above. 
     In view of this, the Applicant has already filed the application of a speaker device in which, for example, a rolled edge having a function similar to that of the above-described edge portion is adopted in place of the above-described damper, and further, the rigidity of the diaphragm in the vibration direction can be enhanced, as disclosed in the gazette of Patent Document 1. 
     With a configuration of the speaker disclosed in Patent Document 1, it is possible to solve the problems experienced by the use of the above-described damper, and further, to enhance the rigidity of the diaphragm in the vibration direction, thus achieving excellent acoustic characteristics as a bass reproducing speaker. 
     Patent Document 1: Japanese Patent Application Laid-open No. 2005-191746 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     The bass reproducing speaker disclosed in Patent Document 1 is configured such that the vibration caused by the voice coil movably disposed in the magnetic gap is transmitted to the drive cone, via which the diaphragm is driven. This configuration adopts means for joining (i.e., bonding) the diaphragm to the drive cone by using, for example, an adhesive agent. 
     A bonded surface between the drive cone and the diaphragm is formed substantially in parallel to a surface perpendicular to the vibration direction of the drive cone and the diaphragm in the speaker disclosed in Patent Document 1. Therefore, the speaker of this type accompanied with the great amplitude generated in the diaphragm suffers from a problem that the portion is liable to be peeled off with poor durability. That is to say, in the case where the drive cone and the diaphragm are peeled off from each other, an abnormal noise on a high level occurs at the peeled-off portion, thereby inducing a critical result for the speaker of this type. 
     In the meantime, Patent Document 1 is directed to a thin speaker as a whole, and therefore, a sufficient rigidity in the vibration direction cannot be satisfactorily exhibited in an integral structure constituted of the drive cone and the diaphragm, in particular. This point is susceptible to improvement. 
     In a closed space defined by the frame, the drive cone, the diaphragm, and the edge portion, repeated motions of compression and expansion accompanied by the vibration of the diaphragm break the joint between the drive cone and the diaphragm, thereby inducing another critical problem that a sound cannot be reproduced. 
     The present invention is directed to solve the above-described problems. In other words, the present invention is suitable for, in particular, a speaker device accompanied with the high amplitude in the diaphragm, as described above, and therefore, its objects are to provide a speaker device in which the rigidity of the drive cone and the diaphragm in the vibration direction can be further enhanced, and a speaker having enhanced durability, which can reduce the frequency of occurrence of peeling-off between the drive cone and the diaphragm. 
     Means for Solving the Problems 
     In order to solve the above-described problems, a preferred basic mode of a speaker device according to the present invention, according to claim  1 , is featured by a speaker device which is provided with a drive cone and a diaphragm integrally driven by a voice coil movably disposed in a magnetic gap and in which peripheral edge portions of the drive cone and the diaphragm are supported by a frame via different edge portions, the speaker device characterized in that: a rising-up portion which rises up toward an acoustic radiation direction from an inner circumferential end of the drive cone, and a rising-down portion which reversely rises down toward a direction reverse to the acoustic radiation direction continuously to and outward of the rising-up portion are formed on the drive cone; and at a top formed between the rising-up portion and the rising-down portion on the drive cone, an inner circumferential end of the diaphragm is fixed to the drive cone, and further, a first rib and a second rib outside of the first rib are formed on the rising-down portion in the drive cone integrally with the drive cone toward the acoustic radiation direction, a back side of the diaphragm being secured at each of the tips of the first rib and the second rib. 
     In this case, in one preferred mode, the first rib and the second rib are formed concentrically with each other, as viewed in the acoustic radiation direction, and further, are formed in a state in which they are separated into a plurality of arcs. 
     With the speaker device having the above-described configuration, the top is formed, in the drive cone, between the rising-up portion which rises up at an acute angle toward the acoustic radiation direction from the tip at the inner circumferential edge (hereinafter referred to as an inner circumferential end) of the drive cone and the rising-down portion which rises down toward a direction reverse to the acoustic radiation direction. Moreover, the top has the groove, and further, the drive cone supports the diaphragm in the state in which the projection formed at the inner circumferential end of the diaphragm is inserted into the groove, thereby enhancing the rigidity in the vibration direction of the diaphragm. As a consequence, the drive cone and the diaphragm supported by the drive cone can be vibrated integrally with each other with the application of drive force of the voice coil, and thus, can be suitably adopted in, particularly, a speaker accompanied with a large amplitude in the diaphragm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view showing a speaker device in a first embodiment according to the present invention; 
         FIG. 2  is an enlarged cross-sectional view showing mainly a drive cone, in particular, in the speaker device shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view showing a second embodiment in which configurations of a drive cone and a diaphragm are partly varied; 
         FIG. 4  is a cross-sectional view showing a third embodiment in which a configuration of a drive cone is partly varied; 
         FIG. 5  is a partial cross-sectional view showing a speaker device in a fourth embodiment according to the present invention; 
         FIG. 6  is a partial cross-sectional view showing a speaker device in a fifth embodiment according to the present invention; 
         FIG. 7  is a plan view exemplifying arrangement of a rib with respect to a drive cone; 
         FIG. 8  is a plan view exemplifying another arrangement of the rib with respect to the drive cone; and 
         FIG. 9  is a plan view exemplifying a further arrangement of the ribs with respect to the drive cone. 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS 
     
         
           1  pole yoke 
           2   a ,  2   b  magnet 
           3  plate 
           4  sub plate 
           5  magnetic gap 
           6  voice coil 
           7  voice coil bobbin 
           11  drive cone 
           11   c  first rib 
           11   d  second rib 
           11   f  diaphragm fixing surface 
           11   g  first groove 
           11   h  second groove 
           11   i  third groove 
           11   m  joint surface 
           11   n  diaphragm fixing surface 
           12  frame 
           13  edge portion 
           14  diaphragm 
           14   a  first projection 
           14   b  second projection 
           14   c  third projection 
           14   h  rising-up surface 
           15  edge 
           16  gasket 
           17  center cap 
         A closed space 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, a speaker device according to the present invention will be described in the embodiments shown in the drawings. An obverse and a back side described hereinafter are defined as an acoustic radiation side and a side reverse to the acoustic radiation side, respectively.  FIG. 1  shows a first embodiment, being a cross-sectional view showing a right half on a center line in the speaker device. Reference numeral  1  designates a pole yoke having a central portion formed into a hollow shape. Ring-like magnets  2   a  and  2   b  are disposed coaxially with a cylindrical portion  1   b  of the pole yoke in such a manner that the pole yoke  1  is mounted on a disk-like flange  1   a  formed integrally with a bottom of the pole yoke  1 . 
     Upper surfaces of magnets  2   a  and  2   b  are disposed a ring-like plate  3  and a ring-like sub plate  4  in such a manner as to be fitted to an inner circumferential surface of the plate  3 . With the above-described configuration, a magnetic gap  5  is formed between an inner circumferential surface of the ring-like sub plate  4  and a peripheral surface of the pole yoke  1  (i.e., a peripheral surface of the cylindrical portion  1   b ). 
     To the magnetic gap  5  is movably fixed a cylindrical voice coil bobbin  7  having a voice coil  6  wound therearound along a longitudinal direction of the pole yoke  1  (i.e., in a vertical direction in  FIG. 1 ). Moreover, at a peripheral surface in the vicinity of an upper end of the voice coil bobbin  7  is fixed a ring member  8 , which forms an inversed L shape (a cross-sectional shape) by forming a wall surface upward so as to form a U-shaped sump for an adhesive agent between the voice coil bobbin  7  and the same. 
     An inner circumferential end of a drive cone  11  (i.e., a tip of an inner circumferential edge of the drive cone  11 ) is inserted into the U-shaped portion formed between the ring member  8  and the voice coil bobbin  7 , and further, an inner circumferential end of the drive cone  11  is joined to a peripheral surface of the voice coil bobbin  7  via an adhesive agent (not shown) impregnated into the U-shaped portion. The drive cone  11  is made of, for example, a synthetic resin material and molded into a substantially cylindrical shape as a whole, and further, includes a rising-up portion  11   a , which rises up at an acute angle toward an acoustic radiation direction from the inner circumferential end thereof, and a rising-down portion  11   b , which rises down toward a direction reverse to the acoustic radiation direction. 
     At the surface of the rising-down portion  11   b  on the drive cone  11  are formed two ribs  11   c  and  11   d  integrally with each other toward the acoustic radiation direction (in a direction from the surface of the drive cone  11  toward the back side of a diaphragm, described later, that is, upward in  FIG. 1 ). In the embodiment, the rib formed near the rising-up portion  11   a  on the drive cone  11  is referred to as a first rib  11   c  whereas the rib formed near an edge portion  13  is referred to as a second rib  11   d.    
     A peripheral end of the drive cone  11  (i.e., a tip of a peripheral edge of the drive cone  11 ) is formed into a flange shape. Between the flange lie and a frame  12  is interposed the roll-like edge portion  13 . That is to say, the drive cone  11  is supported by the frame  12  in such a manner as to become drivable in the acoustic radiation direction via the roll-like edge portion  13 . 
     In the meantime, grooves are formed along the annular top formed between the rising-up portion  11   a  and the rising-down portion  11   b  on the drive cone  11  and the tips of the first rib  11   c  and the second rib  11   d . The drive cone  11  is fixed to a back side of a diaphragm  14  via an adhesive agent (not shown) injected into the grooves. A structure for fixing the diaphragm  14  to the drive cone  11  will be described later in detail in reference to  FIG. 2 . 
     A peripheral edge of the diaphragm  14  is supported at an opening edge of the frame  12  via a wedged-shaped edge  15 . Here, reference numeral  16  designates a gasket for holding a peripheral edge of the wedged-shaped edge  15  at the opening edge of the frame  12 . 
     The diaphragm  14  in the embodiment is concentrically formed. In the vicinity of an inner circumferential edge of the diaphragm  14  is fixed a center cap  17  occupying a relatively large area. That is to say, a peripheral edge of the center cap  17  is bent toward the rising-down portion  11   b  of the drive cone  11 , intrudes into the groove formed on the diaphragm  14 , and then, is fixed to the diaphragm  14  at the groove via the adhesive agent (not shown). A structure for fixing the center cap  17  to the diaphragm  14  also will be described later in detail in reference to  FIG. 2 . 
     The wedged-shaped edge  15  supporting the diaphragm  14  at the peripheral edge of the diaphragm  14  is constituted of a first region  15   a  whose crest is high and which is widely formed, and a second region  15   b  whose crest is lower than the height of the crest of the first region  15   a  and which is narrowly formed on the side of the frame  12  with respect to the first region  15   a . With this constitution, the wedged-shaped edge constituting the first region  15   a , in particular, can secure a greater compliance, and therefore, it can operatively follow the diaphragm  14  even if the diaphragm  14  is largely driven. 
     In the speaker device having the above-described configuration, it is desirable that a space surrounded by the wedged-shaped edge  15 , the diaphragm  14 , the drive cone  11 , the edge portion  13  and the frame  12 , as indicated by reference character A, should be defined in a closed state. Air staying inside of the closed space A acts as an air spring in such a manner that the diaphragm  14  via the drive cone  11  is driven integrally with the drive cone  11 . 
       FIG. 2  is an enlarged cross-sectional view showing mainly the drive cone, in particular, in the speaker device shown in  FIG. 1 , in explaining the structure for fixing the diaphragm  14  to the drive cone  11 . 
     At the annular top formed between the rising-up portion  11   a  and the rising-down portion  11   b  on the drive cone  11 , a fixing surface  11   f  for the diaphragm is formed substantially in parallel to a surface perpendicular to the vibration direction of the drive cone, as shown in  FIG. 2 . An inner circumferential edge  14   d  of the diaphragm  14  is fixed at the back side thereof to the fixing surface  11   f  via the adhesive agent (not shown). 
     On an extension of the fixing surface  11   f , that is, between the fixing surface  11   f  and the rising-down portion  11   b  is further formed a groove  11   g  (also referred to as a first groove) along the fixing surface  11   f . A projection (also referred to as a first projection)  14   a  formed at the back side of the inner circumferential edge of the diaphragm  14  in such a manner as to project toward the drive cone  11  is fixed to the drive cone  11  via the adhesive agent (not shown) in a state in which the projection  14   a  is inserted into the groove  11   g.    
     Moreover, at the respective tips of the first rib  11   c  and the second rib  11   d  formed in the drive cone  11  are formed grooves  11   h  and  11   i  (also referred to as a second groove and a third groove, respectively) along the tips. 
     A projection (also referred to as a second projection)  14   b  formed on the diaphragm  14  in such a manner as to project toward the drive cone  11  is fixed via the adhesive agent (not shown) in a state in which the projection  14   b  is inserted into the groove  11   h  formed at the tip of the first rib, and further, a projection (also referred to as a third projection)  14   c  formed nearer the wedged-shaped edge  15  than the second projection  14   b  is fixed via the adhesive agent (not shown) in a state in which the projection  14   c  is inserted into the groove  11   i  formed at the second rib. 
     As described above, in the embodiment shown in  FIG. 1  and  FIG. 2 , the first, second and third projections  14   a ,  14   b  and  14   c  are formed on the diaphragm  14  in such a manner as to project toward the drive cone  11 , and further, are fixed via the adhesive agent (not shown) in the state in which the first to third projections are inserted into the first groove  11   g  formed at the top of the drive cone  11  and the second and third grooves  11   h  and  11   i  formed at the tips of the ribs  11   c  and  11   d , respectively. 
     In the meantime, to the above-described diaphragm  14  is fixed the peripheral edge of the center cap  17 , as described above. A groove  14   e  is formed on the diaphragm  14 . The center cap  17  is fixed to the diaphragm  14  in a state in which a bent portion  17   a  formed at the peripheral edge of the center cap  17  is inserted into the groove  14   e.    
     Here, the adhesive agent (not shown) should be preferably filled into the groove  14   e  formed on the diaphragm  14 , so that the center cap  17  and the diaphragm  14  are joined to each other, thereby achieving a satisfactory mechanical strength. 
     At a position of the diaphragm  14  corresponding to the bent portion  17   a  of the center cap, the second projection  14   b  formed on the diaphragm  14  is inserted into the groove  11   h  formed at the first rib  11   c  in the drive cone  11 , to be fixed via the adhesive agent (not shown). As a consequence, the center cap  17  is driven in the vibration direction of the voice coil together with the diaphragm  14  disposed in such a manner as to surround the center cap, thus securing a satisfactory sound pressure level in the bass region. 
     Consequently, with the above-described speaker structure, a part of the diaphragm  14  is joined at the top of the drive cone  11 , and further, is joined also to the first rib  11   c  and the second rib  11   d  formed on the drive cone  11 , thus further enhancing the rigidity in the vibration direction. Additionally, a high amplitude can be given to the diaphragm. 
     In addition, the diaphragm  14  is bonded to the drive cone  11  in the state in which the first, second and third projections  14   a,    14   b  and  14   c  formed on the back side of the diaphragm  14  are inserted into the first, second and third recesses  11   g ,  11   h  and  11   i  formed on the drive cone  11 , respectively, thereby remarkably reducing the frequency of occurrence of an inconvenience such as peeling-off of the diaphragm  14  from the drive cone  11 . In this way, the speaker device excellent in durability can be provided. 
       FIG. 3  shows a speaker device in a second embodiment according to the present invention.  FIG. 3  illustrates mainly a structure for fixing a diaphragm  14  to a drive cone  11 , like  FIG. 2  illustrated already. Here, in  FIG. 3 , typical parts exhibiting the same functions as those shown in  FIG. 2  are designated by the same reference numerals, and therefore, their detailed explanation will be omitted below. 
     In the embodiment shown in  FIG. 3 , a step  14   g  is formed on the diaphragm  14 , and further, a bent portion  17   a  formed toward the diaphragm  14  at a peripheral edge of a center cap  17  is joined along a rising-up surface  14   h  having the step  14   g . The bent portion  17   a  of the center cap  17  and the rising-up surface  14   h  of the diaphragm  14  are fixed substantially in parallel to a vibration direction via an adhesive agent (not shown). 
     In the meantime, in the embodiment shown in  FIG. 3 , a joint surface  11   m  to be joined to a third projection  14   c  formed from the diaphragm  14  is formed on an inside surface of a tip of a second rib lid formed on the drive cone  11 , and is formed substantially in parallel to the vibration direction of the drive cone  11 . 
     Specifically, a joint surface  11   m  is formed at the tip of the second rib  11   d  in such a manner as to face the third projection  14   c  formed from the diaphragm  14 . The joint surface  11   m  is formed substantially in parallel to the vibration direction of the drive cone  11 . The third projection  14   c  from the diaphragm  14  is fixed at the joint surface  11   m  formed on the rib  11   d  via the adhesive agent (not shown). 
     Moreover, with the configuration shown in  FIG. 3 , the step  14   g  is formed on the diaphragm  14 , and further, the center cap  17  is fixed to the diaphragm  14  in the state in which the bent portion  17   a  formed at the peripheral edge of the center cap  17  is joined along the rising-up surface  14   h  having the step  14   g . That is, with the configuration shown in  FIG. 3 , the bent portion  17   a  formed at the center cap  17  is fixed to the diaphragm  14  at the rising-up surface  14   h  formed on the diaphragm  14 , and therefore, a necessary and adequate fixing strength can be achieved. Moreover, in the speaker structure shown in  FIG. 3 , the joint surface ll m  corresponding to the third projection  14   c  from the diaphragm  14  in the second rib ll d  is formed substantially in parallel to the vibration direction of the drive cone  11 , and therefore, a necessary and adequate fixing strength can be achieved against the peeling-off of the diaphragm even in the case of the application of the vibration. 
     Incidentally, the embodiment shown in  FIG. 3  is configured such that the joint surface  11   m  corresponding to the third projection  14   c  from the diaphragm  14  is formed at the tip of the second rib  11   d.  Alternatively, there may be adopted a structure having a joint surface to be fixed substantially in parallel to the vibration direction in a manner corresponding to the rising-up surface  14   h  also in a first rib  11   c.    
       FIG. 4  shows a speaker device in a third embodiment according to the present invention.  FIG. 4  illustrates mainly a structure for fixing a diaphragm to a drive cone, like  FIG. 2  illustrated already. Here, in  FIG. 4 , typical parts exhibiting the same functions as those shown in  FIG. 2  are designated by the same reference numerals, and therefore, their detailed explanation will be omitted below. 
     The embodiment shown in  FIG. 4  is configured such that a fixing surface  11   n  of a diaphragm  14  formed at a tip of a first rib  11   c  formed on a drive cone is formed substantially in parallel to a surface perpendicular to a drive direction of a drive cone  11 , and further, the diaphragm  14  is fixed to the fixing surface  11   n  via an adhesive agent (not shown). 
     Also with the configuration shown in  FIG. 4 , the diaphragm  14  can have a necessary and adequate fixing strength with respect to the drive cone  11  in cooperation with other fixing means such as a second rib  11   d . The configuration of the fixing surface  11   n  of the diaphragm shown in  FIG. 4  may be adopted as the second rib  11   d  in the same manner. 
     Besides the configurations of the speaker device shown above in  FIGS. 1 to 4 , there may be configurations shown in  FIGS. 5 and 6 . 
     In  FIG. 5 , two projections formed on a back side of a diaphragm are inserted into two grooves formed on a surface of a drive cone, so that the drive cone and the diaphragm are joined to each other. In addition, it is possible to prevent the drive cone and the diaphragm from being peeled off from each other by forming a claw at one of the projections of the diaphragm. 
     In  FIG. 6 , a projection formed on a surface of a drive cone is inserted into a groove formed on a back side of a diaphragm, so that the drive cone and the diaphragm are joined to each other. In the same manner, projections formed at a first rib and a second rib are inserted into grooves formed on the back side of the diaphragm, so that the first rib and the second rib are joined to the diaphragm, that is, the drive cone supports the diaphragm via the first rib and the second rib. 
     In the meantime, as for the drive cone shown in  FIGS. 1 to 6 , a boundary portion (hereinafter referred to as a bent portion) having a large inclination to a small inclination in rising up is formed to the top from the rising-up portion  11   a . Thanks to such a shape of the drive cone, the rising-up portion  11   a  having the large inclination can be formed from the inner circumferential end of the drive cone to the bent portion, so that the vibration can be efficiently transmitted from the voice coil to the drive cone, and further, to the diaphragm more than a speaker device provided with the drive cone having no bent portion and the diaphragm. 
     As for the first and second ribs shown in  FIGS. 1 to 6 , the arrangement at the surface of the drive cone may be annular, elliptical or polygonal in such a manner as to surround the inner circumferential edge of the drive cone  11 . Although the first and second ribs are different from each other in the above-described embodiments, they may be connected to each other. Otherwise, for example, a cross section of a rib cut in a direction perpendicular to an acoustic radiation direction, as shown in  FIG. 7 , may be substantially arcuate, or the plurality of ribs may be circumferentially arranged in such a manner as to surround the inner circumferential edge of the drive cone. Arrangements shown in  FIGS. 8 and 9  are exemplified, and further, they are not limited. 
     As for the drive cone  11 , the first and second ribs may not be molded integrally with each other, and further, they are not limited. In the case where, in particular, the first and second ribs are molded integrally with the drive cone  11 , it is desirable that a first rib  11   c  and a second rib ll d  should be formed concentrically with each other, and further, should be split into a plurality of arcs, as viewed in the acoustic radiation direction, as shown in  FIG. 9 . With this configuration, it is possible to enhance the entire rigidity of the drive cone  11 , and to suppress the joint of the drive cone  11  to the diaphragm  14  from being broken even if a drive operation of a large stroke acts on the drive cone  11 , so as to prevent any generation of a critical problem that a sound cannot be reproduced. 
     The above-described integral molding can be conducted by a known method. For example, the drive cone  11  can be molded integrally with the first and second ribs by injection molding.