Patent Publication Number: US-11395053-B2

Title: Speaker housing

Description:
TECHNICAL FIELD 
     This invention relates to a speaker housing. 
     BACKGROUND ART 
     In a speaker, vibrations occur in a speaker housing due to sound emission. These vibrations in the speaker housing significantly affect the quality of sound reproduced by the speaker. In this regard, a technique of controlling the quality of reproduced sound by increasing the rigidity of the speaker housing has been provided. 
     In a technique disclosed in JP S58-046613Y2, a plurality of ribs are provided on surfaces of inner walls of a speaker housing. Here, the ribs have a straight shape extending in a distal direction of the housing, and have different sizes. According to this technique, the sound quality of the speaker can be changed and improved by changing a vibration mode of the speaker housing. 
     In a technique disclosed in JP H01-030354A, recessed and protruding portions are provided on inner walls of a speaker housing. Here, the recessed and protruding shape in a plan view is a shape such as an ellipse, a rectangle, a straight shape, a curved shape, or a wave-like shape. By providing repetition of such recesses and protrusions, it is possible to increase the rigidity of the speaker housing and shorten a substantial vibration span on a plate material that constitutes the speaker housing to suppress a resonance phenomenon, without increasing the overall thickness of the plate material. 
     SUMMARY 
     If ribs or recesses and protrusions are provided on the inner walls of the speaker housing as disclosed in the above prior arts, the rigidity of the speaker housing increases, and vibrations in the speaker housing can be suppressed. However, the techniques disclosed in the above prior arts are not designed for increasing rigidity focusing on vibrations in a specific mode that affects the quality of reproduced sound, of the vibrations occurring in the speaker housing. For this reason, to suppress degradation of the quality of reproduced sound, large-scale ribs or recesses and protrusions with which a large rigidity can be obtained need to be provided for a wide range of vibration modes that may occur in the speaker housing, which leads to an increase in the weight of the speaker housing. 
     This invention has been made in view of the foregoing situation, and aims to provide a technical means for increasing rigidity with respect to vibrations in a specific mode while avoiding an increase in the weight of a speaker housing, and suppressing degradation of the quality of reproduced sound. 
     A first speaker housing according to the present invention includes: a front wall to which a speaker unit is to be attached; at least one first wall; at least one second wall; and a plurality of ribs provided on the first wall, wherein an internal space is formed by the front wall, the first wall, and the second wall, a plurality of meshes that segment the first wall are defined, and shapes of the ribs are determined based on directions of a maximum principal stress generated in the meshes due to vibrations when the vibrations occur in a state where the ribs are not provided in the first wall. 
     A second speaker housing according to the present invention includes: a front wall to which a speaker unit is to be attached; at least one first wall; at least one second wall; and a plurality of ribs provided on the first wall, wherein an internal space is formed by the front wall, the first wall, and the second wall, the plurality of ribs are arranged substantially in parallel in a first direction, and at least some of the plurality of ribs curve so as to protrude toward one of two sides in the first direction. 
     A third speaker housing according to the present invention comprising: a front wall where a speaker is to be attached; at least one first wall; at least one second wall; and a plurality of ribs disposed on the first wall, wherein the front wall, the first wall, and the second wall form an internal space, a plurality of meshes that segment the first wall are defined, and the ribs are shaped according to contours of the direction of a maximum principal stress induced in the meshes by vibrations applied to the first wall in a state where the ribs are not disposed on the first wall. 
     A forth speaker housing according to the present invention comprising: a front wall where a speaker is to be attached; at least one first wall; at least one second wall; and a plurality of ribs disposed on the first wall, wherein the front wall, the first wall, and the second wall form an internal space, wherein the plurality of ribs are disposed spaced along a first direction, and wherein at least some of the plurality of ribs are curved protruding along the first direction toward one of two opposing sides of the first direction. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing a configuration of a speaker housing that is an embodiment of this invention. 
         FIG. 2A  is a diagram showing an example configuration of a rib on a left wall of the speaker housing in  FIG. 1 . 
         FIG. 2B  is a diagram showing an example configuration of a rib on a back wall of the speaker housing in  FIG. 1 . 
         FIG. 3A  is a diagram showing a distribution of stress generated in the left wall when vibrations in a primary mode are generated. 
         FIG. 3B  is a diagram showing a distribution of von Mises stress in the left wall in a state where the stress in  FIG. 3A  is generated. 
         FIG. 4A  is a diagram showing a distribution of stress generated in the back wall when vibrations in the primary mode are generated. 
         FIG. 4B  is a diagram showing a distribution of von Mises stress in the back face in a state where the stress in  FIG. 4A  is generated. 
         FIG. 5  is a diagram illustrating a method for determining the shape of a rib. 
         FIG. 6  is a diagram showing a configuration of a speaker housing that is a third comparative example of the same embodiment. 
         FIG. 7  is a diagram showing frequency characteristics of vibrations occurring in a speaker housing that is a first comparative example of the same embodiment. 
         FIG. 8  is a diagram showing frequency characteristics of vibrations occurring in a speaker housing that is a second comparative example of the same embodiment. 
         FIG. 9  is a diagram showing frequency characteristics of vibrations occurring in a speaker housing that is the third comparative example of the same embodiment. 
         FIG. 10  is a diagram showing frequency characteristics of vibrations occurring in the speaker housing according to the same embodiment. 
         FIG. 11A  is a diagram showing an example configuration of a rib fixed to an inner wall face of a speaker housing that is another embodiment of this invention. 
         FIG. 11B  is a diagram showing an example configuration of a rib fixed to an inner wall face of a speaker housing that is another embodiment of this invention. 
         FIG. 12  is a diagram showing an example configuration of a rib fixed to an inner wall face of a speaker housing that is another embodiment of this invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of this invention will be described with reference to the drawings. 
       FIG. 1  is a diagram showing a configuration of a speaker housing  10  that is an embodiment of this invention. This speaker housing  10  has a front wall  11 , a back wall  12  that opposes the front wall  11 , a left wall  13  and a right wall  14  that sandwich an internal space between the front wall  11  and the back wall  12  from left and right, and a top wall  15  and a bottom wall  16  that sandwich the internal space from above and below. Holes  21  and  22  for accommodating a speaker unit are formed in the front wall  11 . 
     A plurality of ribs  31 L to  35 L with different shapes are arranged and fixed substantially in parallel on an inner wall face of the left wall  13 . Here, the ribs  31 L to  35 L are arranged in a direction from a lower short side of the left wall  13  toward an upper short side. 
     The rib  33 L is located substantially in the middle among the ribs  31 L to  35 L, and has a straight shape parallel to the top wall  15  and the bottom wall  16  on the upper and lower sides of the left wall  13  in a plan view. The ribs  34 L and  35 L, which are arranged above the rib  33 L, have a curved shape that bulges upward in a plan view, or more specifically, an arc shape. The ribs  32 L and  31 L, which are arranged below the rib  33 L, have a curved shape that bulges downward in a plan, or more specifically, an arc shape. That is to say, the ribs  31 L to  35 L include the ribs  34 L and  35 L and the ribs  32 L and  31 L that bulge in a direction in which the ribs are arranged with the rib  33 L in the middle. The curvature radius of the rib  35 L is smaller than the curvature radius of the rib  34 L, and the curvature radius of the rib  31 L is smaller than the curvature radius of the rib  32 L. The closer the ribs are to the ribs (specifically, the ribs  35 L and  31 L) at two ends in the arrangement direction relative to the rib (specifically, the rib  33 L) near the middle in the arrangement direction, the smaller the curvature radius of the ribs  31 L to  35 L is. 
     Ribs  31 R to  35 R, which have shapes similar to those of the ribs  31 L to  35 L, are also arranged and fixed in the vertical direction on an inner wall face of the right wall  14 . Ribs  31 B to  35 B, which have shapes similar to those the ribs  31 L to  35 L, are also arranged and fixed in the vertical direction on an inner wall face of the back wall  12 . 
     In the present embodiment, the height of the ribs from the inner wall faces of the housing varies depending on their position in the longitudinal direction.  FIG. 2A  is a diagram showing the rib  33 L fixed to the left wall  13  viewed from a direction parallel to the left wall  13 .  FIG. 2B  is a diagram showing the rib  35 L fixed to the left wall  13  viewed from the direction parallel to the left wall  13 . 
     As shown in  FIG. 2A , the height of the rib  33 L from the left wall  13  increases from the two ends of the rib in the longitudinal direction toward the middle in the longitudinal direction. As shown in  FIG. 2B , the height of the rib  35 L from the left wall  13  increases as it extends away from two ends of the rib in the longitudinal direction, and then decreases toward the middle in the longitudinal direction. Although omitted in the diagrams, the same applies to the other ribs  31 L,  32 L, and  34 L, and the height of the ribs from the inner wall face of the housing inner varies depending on the position in the longitudinal direction. The same applies to the ribs  31 R to  35 R on the right wall  14  and the ribs  31 B to  35 B on the back wall  12 . 
     In the present embodiment, the average height of the ribs  31 L to  35 L from the left wall  13  decreases from the middle in the arrangement direction toward the two sides in the arrangement direction. The same applies to the ribs  31 R to  35 R on the right wall  14  and the ribs  31 B to  35 B on the back wall  12 . Here, the average height means the average height of the ribs at each position in the longitudinal direction. 
       FIGS. 3 and 4  are diagrams illustrating a method for determining the shapes of the ribs according to the present embodiment. Regarding measures against vibrations in the speaker housing, the measures against vibrations in a primary mode, in which the contribution of emitted sound is large, is considered to be important. For this reason, the inventor of the present application caused the primary vibration mode to be generated in the speaker housing  10  in which the ribs are not provided, and obtained a distribution of stress that is generated in each of the walls of the speaker housing  10  in this state.  FIGS. 3A and 4A  show distributions of stress generated in the left wall  13  and the back wall  12 , respectively, when vibrations in the primary mode were generated.  FIGS. 3B and 4B  show distributions of von Mises stress at each position in the inner wall faces in the housing in a state where the stress shown in  FIGS. 3A and 4A  is generated. Here, the von Mises stress refers to a scalar value of the stress. In  FIGS. 3B and 4B , the von Mises stress is expressed by the density of dots, and the higher the von Mises stress in a region is, the higher the density of dots in this region is. Note that, in  FIGS. 4A and 4B, 121 and 122  denote holes that are formed in the back wall  12  in order to take out wires, for example. 
       FIGS. 3A and 4A  show curved lines and straight lines (hereinafter simply referred to as lines)  31 L′ to  35 L′ and lines  31 B′ to  35 B′, which are arranged substantially in parallel from the lower short sides of the left wall  13  and the back wall  12  toward the upper short sides, and are obtained by connecting a plurality of arrows. An arrow at each position on these lines schematically indicates the maximum principal stress at this position. These lines  31 L′ to  35 L′ and lines  31 B′ to  35 B′ have shapes that are based on the maximum principal stress direction at each position on the wall faces of the left wall  13  or the back wall  12 . Specifically, the shapes of the lines  31 L′ to  35 L′ and the line  31 B′ to  35 B′ are determined such that the maximum principal stress direction at each position on the respective lines continues on the left wall  13  and the back wall  12 . Although various methods can be considered as the method for determining the lines  31 L′ to  35 L′ and the lines  31 B′ to  35 B′, the lines may be determined as follows, for example. 
     First, the wall faces of the left wall  13  and the back wall  12  are segmented to form fine meshes (e.g. meshes with a maximum outer diameter of 1 to 5 mm), and the maximum principal stress in each of the meshes is obtained. Next, as shown in  FIG. 5 , a section from the upper side to the lower side of each of the left wall  13  and the back wall  12  is substantially evenly divided into six subsections, and the five dividing positions in the middle in the left-right direction are set as initial positions X 0 . Next, portions rightward from the initial positions X 0  on the lines  31 L′ to  35 L′ and the lines  31 B′ to  35 B′ are obtained. Specifically, as shown in an enlarged view in  FIG. 5 , each of the initial positions X 0  is assumed to be a current position X 1 , the maximum principal stress in the mesh at the current position X 1  is compared with the maximum principal stress in the meshes at an upper right position X 2 , a right position X 3 , and a lower right position X 4  with respect to the mesh at the current position X 1 , and a mesh is selected in which the maximum principal stress with the closest orientation and magnitude is generated. The thus-selected mesh is set as a mesh at the current position, and the same processing is repeated. Thus, the shapes of the portions of the lines  31 L′ to  35 L′ and the lines  31 B′ to  35 B′ on the right side of the initial positions X 0  are determined. The shapes of the portions of the lines  31 L′ to  35 L′ and the lines  31 B′ to  35 B′ on the left side of the initial positions X 0  are determined through the same processing. 
     Here, since stress and distortion are in a proportional relationship, the maximum principal stress direction can be considered as a direction in which a large distortion is occurring. Accordingly, it is conceivable that if the rigidity in the maximum principal stress direction in which a large distortion occurs is increased, the rigidity can be effectively increased with respect to vibrations in the primary mode. For this reason, in the present embodiment, lines are obtained that form a curved or straight shape along which the maximum principal stress at each position on the lines extending along the respective walls continues, and ribs extending along these lines are fixed to the inner wall faces of the speaker housing  10 . 
     That is to say, as shown in  FIG. 1 , five ribs are formed on each of the left wall  13 , the back wall  12 , and the right wall  14 . The shapes of the ribs  31 L to  35 L,  31 R to  35 R, and  31 B to  35 B in  FIG. 1  are determined so as to thus extend along continuous curved or straight lines drawn by the maximum principal stress in the meshes on the lines on the wall faces of the speaker housing  10  in which the ribs are not provided. 
     Specifically, for example, in the left wall  13  in  FIG. 1 , the rib (first rib)  33 L disposed near the middle in the vertical direction is disposed extending straight in the horizontal direction, and the ribs (second ribs)  34 L and  35 L, which are disposed above the rib  33 L, curve so as to protrude upward. Meanwhile, the ribs (third ribs)  32 L and  31 L, which are disposed below  33 L, curve so as to protrude downward. The ribs  31 B to  35 B and  31 R to  35 R in the other walls  12  and  14  are also formed in the same manner. 
     As mentioned above, in the present embodiment, the height of each rib from the inner wall face of the housing is varied in the vertical direction. The reason will be described below. 
     As shown in  FIGS. 3B and 4B , the von Mises stress is not uniform over the inner wall faces of the housing, and generally, the von Mises stress is at its maximum in the middle of the inner wall faces of the housing, and the von Mises stress decreases toward the periphery of the inner wall faces of the housing. Accordingly, the von Mises stress is not uniform either on the lines  31 L′ to  35 L′ and  31 B′ to  35 B′ along which the maximum principal stress continues, and the von Mises stress varies in the longitudinal direction of the lines. 
       FIG. 3A  shows lines  31 L″ to  35 L″ that correspond respectively to the lines  31 L′ to  35 L′ shown in  FIG. 3B , and  FIG. 4B  shows lines  31 B″ to  35 B″ that correspond respectively to the lines  31 B′ to  35 B′ shown in  FIG. 4A . According to  FIG. 3B , for example, the von Mises stress in the meshes on the line  33 L″ increases from a left end of the line  33 L″ toward the middle, and decreases from the middle toward a right end. The von Mises stress on the line  35 L″ increases once rightward from a left end of the line  35 L″, then decreases therefrom toward the middle, increases once again rightward from the middle, and then decreases therefrom toward a right end. 
     Here, in order to sufficiently increase the rigidity with respect to vibrations in a specific mode, it is thought that it is effective to provide rigidity corresponding to the von Mises stress that is locally generated in each mesh, at a position on a rib corresponding to the mesh. In the present embodiment, the height of the ribs  31 L to  35 L,  31 R to  35 R, and  31 B to  35 B at a position corresponding to each mesh is a height corresponding to the von Mises stress at this position in the corresponding inner wall face of the housing, and thus, the local rigidity of the ribs corresponds to the local von Mises stress. Note that the height of each rib is not specifically limited, but may be 5 to 20 mm, for example, and is preferably 10 to 15 mm. The width of each rib may also be the same as the height. 
     Next, the effects of the present embodiment will be described in comparison with the following first to third comparative examples. This first comparative example is a common speaker housing with no rib provided, and the plate thickness of the left wall and the right wall is 5 mm. This plate thickness is also the same in the present embodiment and the third comparative example. The second comparative example is a speaker housing in which the plate thickness of the left wall and the right wall is 2 mm greater than in the first comparative example. The third comparative example is a speaker housing  10 B in which a plurality of ribs  40 , which extend in parallel in the vertical direction, are fixed to inner wall faces of a left wall  13 , a right wall  14 , and a back wall  12 , as shown in  FIG. 6 . The height of the ribs  40  from the inner fall faces is 5 mm, and the width is 5 mm. The speaker housing  10  according to the present embodiment is basically a housing with the configuration in  FIG. 1 . However, the height of the ribs  31 L to  35 L,  31 R to  35 R, and  31 B to  35 B was not varied in accordance with the position in the longitudinal direction, and was set uniformly to 5 mm. The width was also set to 5 mm. 
       FIGS. 7 to 9  are diagrams showing frequency characteristics of vibrations occurring in the wall faces of the speaker housings due to sound emission in the first to third comparative examples.  FIG. 10  is a diagram showing frequency characteristics of vibrations occurring in the wall faces of the speaker housing due to sound emission in the speaker housing  10  according to the present embodiment. In  FIGS. 7 to 10 , the horizontal axis indicates the frequency (Hz), and the vertical axis indicates the average acceleration (m/s2) of vibrations in the walls. A 11  denotes a frequency characteristic of vibrations occurring in the front wall  11 , A 12  denotes a frequency characteristic of vibrations occurring in the back wall  12 , A 13  denotes a frequency characteristic of vibrations occurring in the left wall  13 , A 14  denotes a frequency characteristic of vibrations occurring in the right wall  14 , and A 15  denotes a frequency characteristic of vibrations occurring in the top wall  15 . 
     According to  FIGS. 7 to 10 , the frequency with which a peak P 1  in the primary vibration mode is generated is 425 Hz in the first comparative example ( FIG. 7 ), 535 Hz in the second comparative example ( FIG. 8 ), 485 Hz in the third comparative example ( FIGS. 6 and 9 ), and 730 Hz in the present embodiment ( FIGS. 1 to 10 ). Thus, according to the present embodiment, the frequency in the primary vibration mode can be greatly increased compared with the first to third comparative examples. In addition, according to the present embodiment, it is possible to greatly increase the frequency in the primary vibration mode and suppress degradation of the quality of sound reproduced by the speaker without greatly increasing the weight of the speaker housing, compared with the second and third comparative examples. 
     An embodiment of the present invention has been described above, but there may also be other embodiments of this invention. For example, the following embodiments are possible. Note that one or more of the following examples can be combined. 
     (1) In the above embodiment, the height of each rib is varied in the longitudinal direction of the rib in order to obtain rigidity corresponding to the local von Mises stress at positions corresponding to the meshes of the rib. However, instead of employing this configuration, the width of each rib may be varied in the longitudinal direction thereof, as shown as an example in  FIG. 11 . Alternatively, both the height and the width of each rib may be varied in the longitudinal direction thereof. That is to say, the size of at least one of the height and the width of each rib may be varied in the longitudinal direction of the rib. 
     (2) In the above embodiment, the ribs are fixed to the left wall  13 , the right wall  14 , and the back wall  12  of the speaker housing  10 , but the ribs may also be fixed to the other walls, or may be fixed to all of the walls. That is to say, the ribs can also be provided on one or more of the left wall  13 , the right wall  14 , the back wall  12 , the top wall  15 , and the bottom wall  16 . Since the ribs can be provided on all of the walls, the ribs can also be provided on a second wall according to the present invention. 
     (3) In the above embodiment, five ribs are fixed to one inner wall face, but the number of ribs is not limited thereto. More than five ribs, or less than five ribs may be fixed. Different numbers of ribs may be fixed on different inner wall faces. In the above embodiment, the rib near the middle in the vertical direction is formed straight, the ribs thereabove curve so as to protrude upward, and the ribs therebelow curve so as to protrude downward. However, the present invention is not limited thereto. For example, two or more straight ribs may be provided, or no straight rib may be provided. The straight rib may alternatively be disposed at a position other than a position near the middle in the vertical direction. All of the ribs can also be formed to curve so as to protrude downward, or curve so as to protrude upward. That is to say, at least some of the plurality of ribs arranged in parallel may curve. The curvature radius of the ribs is not specifically limited either. 
     (4) In the above embodiment, the ribs are fixed onto the inner faces of the speaker housing, but the installation mode of the ribs is not limited to fixation. For example, the ribs may alternatively be formed in the inner wall faces by means of drilling or the like. 
     (5) In the above embodiment, the ribs are formed so as to extend substantially in the horizontal direction. However, as long as the ribs are provided along the main stress direction in the meshes, the ribs can alternatively be provided substantially in the vertical direction, or the directions in which the plurality of ribs extend may include a plurality of mixed directions such as substantially the horizontal direction and substantially the vertical direction. 
     In the above embodiment, when the direction in which the ribs extend is determined, meshes are selected such that the direction and the magnitude of the main stress in adjacent meshes are close to each other, but the present invention is not limited thereto. That is to say, the direction and the magnitude of the main stress need not be close to each other in all of the adjacent meshes. The direction and the magnitude may slightly differ from each other in some of the adjacent meshes. The direction in which the ribs extend may also be determined in accordance with the thus-selected meshes. Also, the ribs need not be continuous, and the ribs may alternatively be disposed with predetermined gaps therebetween in the direction in which the ribs extend. 
     In the above embodiment, the direction in which the ribs extend is determined based on the main stress generated when vibrations in the primary mode are generated. However, for example, the direction in which the ribs extend may alternatively be determined based on the main stress generated when vibrations in a higher mode, such as a secondary mode or a tertiary mode, are generated. For example, in an example shown in  FIG. 12 , the ribs are formed based on the main stress generated when vibrations in the secondary mode are generated. Accordingly, various ribs can be formed based on the direction of generated main stress, regardless of the mode of vibrations. 
     The shape of the speaker housing is not limited to a rectangular-parallelpiped as in the above embodiment, and various modes are possible. That is to say, an internal space need only be formed by the front wall to which the speaker unit is attached, as well as by a plurality of other walls, and the ribs need only be formed on at least some of the plurality of other walls. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10  Speaker housing 
               11  Front wall 
               12  Back wall 
               13  Left wall 
               14  Right wall 
               15  Top wall 
               16  Bottom wall 
               31 L to  35 L,  31 R to  35 R,  31 B to  35 B Rib