Abstract:
To provide an electronic device case structure which suppresses noise generation caused by vibrations generated from electronic devices held inside an electronic device unit being propagated to a unit case. 
     An electronic device case structure provided with a unit case which is detachably mounted to an electronic device unit that holds electronic devices therein, said electronic devices being vibration generating sources. The unit case is provided with unit support mechanisms which comprise rotatable roller members that guide and support the electronic device unit when the electronic device unit is being attached or detached. The roller members are configured from vibration-preventing members that comprise an elastic material.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electronic device case structure which suppresses noise generation caused by propagation of vibration from vibration generating sources such as an HDD (Hard Disk Drive) and other disk drive devices to a unit case as an electronic device unit which holds the vibration generating sources is mounted in the unit case. 
       BACKGROUND ART 
       [0002]    In general, an electronic device such as a server includes movable units such as an HDD, a disk drive device, or a cooling fan. These movable units act as vibration generating sources. 
         [0003]    Vibration generated by such vibration generating sources propagates to each unit of a unit case and acts as noise generating sources, as an electronic device unit which holds the electronic device is mounted in the unit case. 
         [0004]    Especially noise generated when the HDD acts as a vibration generating source grates on human&#39;s ears because of its constant frequency, thus making the users feel uncomfortable. In highly silent products, the ratio of noise due to vibration of the HDD to the total noise is relatively high. 
         [0005]    When a plurality of HDDs are mounted, interference between vibration forces generated by the HDDs may produce beat waveforms due to slight differences in frequency between the HDDs, which grate on human&#39;s ears as noise. The users often make complaints about this problem, against which a countermeasure is required. 
         [0006]    Examples of effective solutions to this problem include preventing vibration generated by the vibration generating sources from propagating to each unit of the unit case that may act as a noise emitting source. 
         [0007]    The known conventional examples include an electronic device case structure  110  having a structure which prevents vibration propagation, as shown in  FIG. 6 . 
         [0008]    More specifically, an electronic device unit  130  which holds an electronic device includes four vibration generating sources  135  (for example, HDDs). The electronic device unit  130  is, for example, movable in a direction indicated by an arrow A (direction of attachment and detachment) relative to a unit case  111  of a tower server device  125  and can be easily attached to and detached from the unit case  111 . 
         [0009]    The unit case  111  has a quadrangular frame-shaped cross-section defined by a bottom surface portion  112 , side surface portions  113 , and a top surface portion  114 . The bottom surface portion  112  includes a plate  112 A. The bottom surface of the electronic device unit  130  abuts against the top surface of the plate  112 A and is slidable on this top surface. 
         [0010]    Three guide rails  113 A are arranged on each of the opposed inner surface portions of the side surface portions  113  to vertically align themselves and extend in the direction indicated by the arrow A. 
         [0011]    An opening portion  114 A is formed in the top surface portion  114  of the unit case  111 . A unit holding member  115  is detachably provided to seal the opening portion  114 A. Engagement portions  115 B are formed at the two ends of the unit holding member  115  in a direction perpendicular to the direction of attachment and detachment A by bending. 
         [0012]    In contrast to this, engagement holes  114 B which engage with the engagement portions  115 B of the unit holding member  115  are formed in the top surface portion  114  of the unit case  111 . 
         [0013]    A sheet-like low-elasticity material  116  surrounds the plate  112 A of the bottom surface portion  112 . Sheet-like low-elasticity materials  117  are arranged between adjacent guide rails of the three guide rails  113 A and outside the two, uppermost and lowermost guide rails  113 A. A sheet-like low-elasticity material  118  is placed on the back surface of the unit holding member  115 . 
         [0014]    Independently of the above-mentioned electronic device case structure, a housing device for an acoustic device is known (see PTL 1). 
         [0015]    The housing device for an acoustic device disclosed in PTL 1 includes a plurality of rollers which are formed by elastic members and arranged on four faces of a box-shaped sleeve. With this arrangement, an acoustic device can be easily housed in and removed from the sleeve. Since the acoustic device is pressed by the elasticity of the rollers, vibration of the housing is suppressed and vibration externally applied to the sleeve is blocked. 
         [0016]    Examples of other known devices which prevent vibration include a drawer device (see PTL 2). 
         [0017]    In the drawer device disclosed in PTL 2, rollers are rotatably attached to helical coil insert nuts for bolts at the lower end portions of the side walls of the housing, which mount a video tape recorder accommodated in an accommodation unit on a mounting table and pull it out. The mounting table is slid and pulled out so as to clamp the rollers by slider fittings at the two ends of the mounting table. 
         [0018]    In, for example, accommodation of an MD (MiniDisc) device, a housing device for an acoustic device which presses an MD device inserted in a sleeve by the elasticity of rollers is also known (see PTL 3). 
       CITATION LIST 
     Patent Literature 
       [0019]    [PTL 1] Japanese Patent No. 3980359 
         [0020]    [PTL 2] Japanese Unexamined Patent Application Publication No. 2002-305048 
         [0021]    [PTL 3] Japanese Unexamined Patent Application Publication No. H09-191186 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0022]    However, the above-mentioned conventional examples respectively pose the following problems. That is, in the electronic device case structure  110  shown in  FIG. 6 , the electronic device unit  130  comes into contact with the plate  112 A and guide rails  113 A of the unit case  111  and is detachably slid. Hence, the unit case  111  is not in direct contact with the low-elasticity material  116  in the bottom surface portion  112  and the low-elasticity materials  117  between adjacent guide rails of the guide rails  113 A in the side surface portions. 
         [0023]    In the above-mentioned arrangement, vibration generated upon driving of the HDDs held in the electronic device unit  130  directly propagates not to the low-elasticity materials  116  and  117  but to the unit case  111 . Therefore, an unsatisfactory anti-vibration effect is produced, making it impossible to sufficiently suppress noise generation by the case. 
         [0024]      FIG. 7  shows a temporal change in sound pressure in the vibration propagation preventing structure  110  according to this conventional example. The temporal change in sound pressure is obtained as a result of sound pressure measurement by a microphone. 
         [0025]    As can be seen from the measurement result shown in  FIG. 7 , in this example, noise is generated because the amplitude of natural vibration is large and vibration transmitted to the unit case  111 , in turn, is large. 
         [0026]    In the housing device for an acoustic device disclosed in PTL 1, an acoustic device can, indeed, be easily housed in and removed from the sleeve. Further, in this housing device, since the acoustic device is pressed by the elasticity of the rollers, vibration of the housing is suppressed and vibration externally applied to the sleeve is blocked. 
         [0027]    Note, however, that the above-mentioned housing device for an acoustic device is used for an MD device. The MD device is low in height and the housing device for an acoustic device is also low in height. Therefore, when a housing device having such a configuration is designed to be capable of holding even a plurality of (for example, four) high-height products such as HDDs, rollers having a large total length are required. In addition, since the weight of the rollers is heavy, the weight of the housing for an acoustic device is also heavy. 
         [0028]    When long, heavy rollers are attached and any of them breaks down for some reason, the roller in question requires individual replacement, resulting in poor efficiency. 
         [0029]    In the drawer device disclosed in PTL 2, the rollers are rotatably attached to the helical coil insert nuts for the bolts at the lower end portions of the side walls of the housing. However, these rollers are intended to slide the slider fittings and not intended to suppress propagation of vibration generated by the vibration generating sources held in the electronic device unit. 
         [0030]    The housing device for an acoustic device disclosed in PTL 3 also has the same problem as in PTL 1. 
       Objective of Invention 
       [0031]    It is an exemplary object of the present invention to provide an electronic device case structure which suppresses noise generation caused by propagation of vibration generated by an electronic device held in an electronic device unit to a unit case. 
       Solution to Problem 
       [0032]    An electronic device case structure according to the present invention includes a unit case detachably mounted with an electronic device unit which holds inside, an electronic device acting as a vibration generating source, and a unit support mechanism including a plurality of roller members implemented in a vibration-preventing member made of an elastic material, the roller members supporting the electronic device unit and guiding the electronic device unit in attaching and detaching the electronic device unit. 
       Advantageous Effects of Invention 
       [0033]    With the electronic device case structure according to the present invention, since an electronic device unit which holds inside, an electronic device acting as a vibration generating source is supported by a unit case through a unit support mechanism including roller members, the electronic device unit and the unit case are supported by a floating structure without being in direct contact with each other. Since the roller members are implemented in a vibration-preventing member made of an elastic material, propagation of vibration generated by the electronic device acting as a vibration generating source is suppressed. Therefore, it is possible to prevent vibration generated by the electronic device from propagating to the unit case and radiating from the unit case as sound waves to suppress noise generation. 
         [0034]    Since the electronic device unit is guided by the roller members in attaching and detaching the electronic device unit to and from the unit case, attachment and detachment can easily be done. 
         [0035]    Since the roller members are implemented in a vibration-preventing member and rotate in attaching and detaching the electronic device unit, it is possible to prevent the vibration-preventing member that is made of a low-elasticity material from greatly deforming by a shearing force to, in turn, prevent degradation in performance of the vibration-preventing member. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0036]      FIG. 1  is an exploded perspective view illustrating an exemplary embodiment of an electronic device case structure according to the present invention. 
           [0037]      FIG. 2  is a front view showing an electronic device unit according to the exemplary embodiment as mounted in a unit case when only the unit case is represented in a cross-sectional view. 
           [0038]      FIG. 3  is a side view showing the electronic device unit according to the exemplary embodiment as mounted in the unit case when only the unit case is represented in a cross-sectional view in the direction of attachment and detachment. 
           [0039]      FIG. 4  is an overall perspective view showing details of a unit support mechanism including a roller member according to the exemplary embodiment. 
           [0040]      FIG. 5  is a chart illustrating an exemplary result of measuring, by a microphone, the sound pressure of vibration transmitted from a vibration generating source in the electronic device unit to the unit case in the case structure according to the exemplary embodiment. 
           [0041]      FIG. 6  is an overall perspective view showing the conventional electronic device case structure. 
           [0042]      FIG. 7  is a chart illustrating an exemplary result of measuring, by a microphone, the sound pressure of vibration transmitted from the vibration generating source in the electronic device unit to the unit case in the conventional electronic device case structure. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0043]    An exemplary embodiment of an electronic device case structure according to the present invention will be described below with reference to  FIGS. 1 to 4 . 
         [0044]      FIG. 1  is an overall perspective view illustrating an electronic device case structure  10 .  FIG. 2  is a front view showing an electronic device unit (to be simply referred to as a unit hereinafter)  30  which holds an electronic device as mounted in a unit case  11 .  FIG. 3  is a side view showing the unit  30  as mounted in the unit case  11  in a cross-section taken in the direction of attachment and detachment.  FIG. 4  is an overall perspective view showing a unit support mechanism  18  including a rotatable roller member  19 . 
         [0045]    The electronic device case structure  10  according to this exemplary embodiment includes a unit case  11  detachably mounted with the unit  30  that holds inside, electronic devices such as HDDs  35 , as described above, acting as vibration generating sources. 
         [0046]    The unit case  11  includes, in a plurality of areas, unit support mechanisms  18  which support the unit  30  and guide the unit  30  in its attachment and detachment. The unit support mechanisms  18  include rotatable roller members  19 . The roller members  19  are implemented in a vibration-preventing member made of an elastic material, especially a low-elasticity material. 
         [0047]    The unit  30  is made of a steel plate or hard plastic and has a quadrangular box shape. The unit  30  includes an accommodation room separated by partitions (not illustrated). A plurality of (in this exemplary embodiment, four) HDDs  35  are exchangeably accommodated in the accommodation room. 
         [0048]    The unit  30  as mentioned above is attached to, for example, a tower server device  25  including the unit case  11 . 
         [0049]    The unit  30  is moved toward the unit case  11  in the direction of attachment and detachment indicated by an arrow A in  FIG. 1  so as to be detachably attached to the unit case  11 . 
         [0050]    An engagement hole  30 A which engages with a locking portion  15 A formed in a holding member  15  (to be described in detail later) is formed in the top surface of the unit  30  on the side of an insertion opening of the HDDs  35 . 
         [0051]    The unit case  11  is also made of a steel plate or hard plastic and has a quadrangular frame-shaped cross-section to allow it to receive the unit  30 . The unit case  11  is fixed to a bottom plate  25 A and side plate  25 B of the main body portion of the tower server device  25 . 
         [0052]    The unit  30  is supported inside the unit case  11  in a nearly floated state through the roller members  19  of the unit support mechanisms  18 , as shown in  FIG. 2 . 
         [0053]    More specifically, the unit support mechanisms  18  include a plurality of (in this exemplary embodiment, four) rotatable roller members  19  arranged in each of a bottom surface portion  12  and opposed side surface portions  13  of the unit case  11 . 
         [0054]    With this arrangement, the unit  30  is supported, while the outer peripheral surfaces of the respective roller members  19  are kept in direct contact with the outer peripheral surfaces of three out of four faces of the unit  30 , that is, in a floated state. 
         [0055]    Two unit support mechanisms  18  each including the roller member  19  are arranged in the bottom surface portion  12  of the unit case  11  on each of two lines, that is, the front and back sides in the direction of attachment and detachment A. 
         [0056]    Two unit support mechanisms  18  each including the roller member  19  are also arranged in each of the opposed side surface portions  13  of the unit case  11  on each of two lines, that is, the front and back sides in the direction of attachment and detachment A. 
         [0057]    The unit support mechanisms  18  are arranged on the front and back sides in the direction of attachment and detachment A with spacings between them nearly equal in the bottom surface portion  12  and the side surface portions  13 . 
         [0058]    As described above, the unit  30  is supported using a plurality of (in this exemplary embodiment, a total of 12) roller members  19  of the unit support mechanisms  18  as support points. 
         [0059]    In the electronic device unit  30 , the unit case  11  can be effectively insulated against vibration by supporting the areas (nodes of vibration) where the amplitude of natural vibration generated by vibration generating sources such as HDDs is minimal. 
         [0060]    In this exemplary embodiment, two roller members  19  of the unit support mechanisms  18  are arranged in each of the bottom surface portion  12  and side surface portions  13  of the unit case  11 , in correspondence with the position of each of areas (a) and (b) where the amplitude of natural vibration obtained by sound pressure measurement shown in  FIG. 7  in the conventional structure is minimal, that is, the position of each node of vibration. 
         [0061]    This state is represented by (a) and (b) respectively indicating the front and back roller members  19 , as illustrated in  FIGS. 1 and 3 . 
         [0062]      FIG. 5  is a chart illustrating an exemplary vibration measurement result obtained by sound pressure measurement using a microphone. In this measurement, four HDDs were mounted as vibration generating sources. 
         [0063]    As described above, when the two roller members  19  of the unit support mechanisms  18  on each of the front and back sides are arranged at the positions of areas (a) and (b) having nodes of vibration, a great noise reduction effect could be obtained, as illustrated in  FIG. 5 . 
         [0064]    In this case, the rotational speed of the HDDs is 15000 rpm (rotation per minute). The main frequency of vibration generated by the rotation of the HDDs is 250 Hz (=15000/60). To focus attention on sounds generated by the HDDs, a sound wave in a waveband having a center frequency of 250 Hz was extracted by band-pass filtering. 
         [0065]    As shown in  FIGS. 2 and 4 , each unit support mechanism  18  arranged in the bottom surface portion  12  includes a rotatable roller member  19  and shaft members  20  which support the roller member  19 . The roller member  19  is made of rubber or an elastomer that is a low-elasticity material. The shaft members  20  are made of a metal or hard plastic. 
         [0066]    The shaft members  20  of the unit support mechanisms  18  having the above-mentioned configuration are rotatably supported by a support plate  21 . The support plate  21  is mounted on the top surface of the bottom plate  25 A of the tower server device  25  while being laid below the bottom surface portion  12  of the unit case  11 , as shown in  FIG. 1 . 
         [0067]    The support plate  21  has an inverted tray configuration defined by a top surface portion  21 A and an edge portion  21 B which is formed below the top surface portion  21 A and has a predetermined height, as shown in  FIG. 4 . 
         [0068]    An opening portion  21 C is formed at a predetermined position in the top surface portion  21 A to rotatably mount the roller member  19  of the unit support mechanism  18 . 
         [0069]    Bifurcated shaft support portions  21 D which horizontally support the shaft members  20  of the unit support mechanism  18  are formed on an edge portion defining the opening portion  21 C to stand upright from the top surface portion  21 A. 
         [0070]    The shaft support portions  21 D are arranged with a predetermined spacing between them in a direction perpendicular to the direction of attachment and detachment A to enable the roller member  19  to rotate in the direction of attachment and detachment A. 
         [0071]    Two sets of unit support mechanisms  18  like that shown in  FIG. 4  are also arranged in the side surface portions  13 , respectively. 
         [0072]    The unit support mechanisms  18  arranged in the bottom surface portion  12  are different from the sets of unit support mechanisms  18  arranged in the side surface portions  13  in terms of positions where the unit support mechanisms  18  are attached and features of a support unit which rotatably supports the shaft members  20 . 
         [0073]    More specifically, opening portions  13 A (see  FIG. 2 ) are formed at predetermined positions in the side surface portions  13  to rotatably mount the unit support mechanisms  18 . 
         [0074]    The unit support mechanisms  18  are arranged in each of the side surface portions  13  so that the shaft members  20  at the two ends of each unit support mechanism  18  extend vertically. With this arrangement, the roller members  19  can rotate about the vertical axis. 
         [0075]    The unit support mechanisms  18  are attached to the side surface portions  13  by holding the outer peripheries of the shaft members  20  of the unit support mechanisms  18  using shaft support members  22  such as commonly-used U bands while the shaft members  20  abut against the outer surfaces of the side surface portions  13 , as shown in  FIG. 2 . 
         [0076]    In doing this, the side surface portions  13  that abut against the lower surfaces of the lower shaft members  20 , of the upper and lower shaft members  20  of the vertically aligned unit support mechanisms  18 , at given positions bear the loads of the unit support mechanisms  18 . Therefore, shaft receptacles (not illustrated) are placed at these positions of the side surface portions  13 . 
         [0077]    As described above, when the unit  30  is attached to the unit case  11 , the unit support mechanisms  18  respectively arranged in the side surface portions  13  of the unit case  11  are supported by the shaft support members  22  so that the outer peripheral surface of the unit  30  slightly presses the outer circumferential surfaces of the respective roller members  19  of the unit support mechanisms  18 . 
         [0078]    With this arrangement, as shown in  FIG. 2 , the unit  30  is supported by the roller members  19  of the unit support mechanisms  18  arranged in each of the bottom surface portion  12  and side surface portions  13  of the unit case  11  and is attached to the unit case  11  in a nearly floated state, as described earlier. 
         [0079]    As shown in  FIGS. 1 to 3 , an opening portion  14 A is formed in a top surface portion  14  of the unit case  11 , and the unit holding member  15  that also serves as a lid is removably placed in the opening portion  14 A. 
         [0080]    The unit holding member  15  has a nearly quadrangular shape, and a locking portion  15 A shaped by being bent to have an L-shaped cross-section is formed in the front surface portion of the unit case  11  in the direction of attachment and detachment A. 
         [0081]    The locking portion  15 A engages with an engagement hole  30 A, as described above, formed in the top surface of the unit  30 , upon being inserted into a through hole  14 C formed in the top surface portion  14  of the unit case  11  when the unit  30  is attached to the unit case  11 . 
         [0082]    With this arrangement, engaging the locking portion  15 A with the engagement hole  30 A makes it possible to prevent the unit  30  mounted in the unit case  11  from slipping in the direction of attachment and detachment A. 
         [0083]    A plurality of (in this exemplary embodiment, four) pressing members  16  are arranged on the back surface of the unit holding member  15  and capable of pressing the top surface of the unit  30 . The pressing members  16  are opposed to the unit support mechanisms  18  arranged in the bottom surface portion  12  of the unit case  11 . 
         [0084]    The pressing members  16  are made of rubber or an elastomer, as in the roller members  19  of the unit support mechanisms  18 , and have, for example, a cylindrical shape. The pressing members  16  can press and support the top surface of the unit  30  attached to the unit case  11 , by a predetermined pressure. 
         [0085]    Engagement portions  15 B for attachment, having inverted L-shaped cross-sections are formed at the two ends of the unit holding member  15  in a direction perpendicular to the locking portion  15 A of the unit holding member  15 . 
         [0086]    In contrast to this, engagement holes  14 B which engage with the engagement portions  15 B are formed in the top surface portion  14  of the unit case  11 . With this arrangement, when the unit  30  is attached to the unit case  11  and the top surface portion  14  of the unit case  11  is covered with the unit holding member  15 , the locking portion  15 A engages with the engagement hole  30 A and the engagement portions  15 B engage with the engagement holes  14 B. 
         [0087]    An operation of attaching or detaching the unit  30 , as described above, to or from the unit case  11  is performed in the following way. 
         [0088]    First, in attachment, the user removes the unit holding member  15  of the unit case  11 . The user then moves the unit  30  holding the HDDs  35  in the direction of attachment and detachment A to insert the unit  30  into the unit case  11 . 
         [0089]    In doing this, the user inserts the unit  30  into the unit case  11  while checking the position of the unit  30  so that the outer peripheral bottom surface and outer peripheral side surfaces of the unit  30  are slightly pressed by the outer peripheral surfaces of the roller members  19  of the unit support mechanisms  18  arranged in the bottom surface portion  12  and the side surface portions  13 . 
         [0090]    When the unit  30  has been inserted up to a predetermined stop position, the user sets the unit holding member  15  at a position above the opening portion  14 A of the unit case  11 . 
         [0091]    The user inserts the locking portion  15 A of the unit holding member  15  into the through hole  14 C in the top surface portion  14  of the unit case  11  and engages the locking portion  15 A with the engagement hole  30 A of the unit  30 . At the same time, the user engages the engagement portions  15 B of the unit holding member  15  with the engagement holes  14 B in the top surface portion  14  of the unit case  11 . 
         [0092]    In detaching the unit  30  from the unit case  11 , the user need only execute the procedure reverse to the above-mentioned procedure of attachment. 
         [0093]    More specifically, first, the user lifts the unit holding member  15  to the upper side to cancel both the engagement between the locking portion  15 A of the unit holding member  15  and the engagement hole  30 A of the unit  30  and the engagement between the engagement portions  15 B of the unit holding member  15  and the engagement holes  14 B in the top surface portion  14  of the unit case  11 . 
         [0094]    The user need only pull the unit  30  out of the unit case  11  in the direction of attachment and detachment A. In doing this, the unit  30  moves along the roller members  19  of the unit support mechanisms  18  held on three faces, namely, the bottom surface portion  12  and side surface portions  13  of the unit case  11 . This makes it easy for the user to pull out the unit  30 . 
         [0095]    The use of the electronic device case structure  10  according to this exemplary embodiment produces the following effects. 
         [0096]    (1) A unit  30  which holds inside, the HDDs  35  acting as vibration generating sources is supported by the unit case  11  through the unit support mechanisms  18  including the roller members  19 . With this arrangement, the unit  30  is supported by a floating structure without being in direct contact with the unit case  11 . Since the roller members  19  are implemented in a vibration-preventing member made of a low-elasticity material, propagation of vibration generated by the HDDs  35  acting as vibration generating sources to the unit case  11  is suppressed. It is, therefore, possible to prevent vibration generated by the HDDs  35  from propagating to the unit case  11  and radiating from the unit case  11  as sound waves to suppress noise generation. 
         [0097]    (2) The unit  30  can be easily attached to and detached from the unit case  11  because the unit  30  is guided by the roller members  19  in its attachment and detachment. 
         [0098]    (3) The roller members  19  are implemented in a vibration-preventing member made of rubber or an elastomer that is a low-elasticity material and rotate in attaching and detaching the unit  30 . It is, therefore, possible to prevent the vibration-preventing member made of a low-elasticity material from greatly deforming by a shearing force to, in turn, prevent degradation in performance of the vibration-preventing member. 
         [0099]    (4) Four pressing members  16  which press the top surface of the unit  30  are arranged on the back surface of the unit holding member  15 . The pressing members  16  are positioned in correspondence with the four roller members  19  arranged in the bottom surface portion  12  of the unit case  11 . Therefore, the pressing members  16  can press the unit  30  with good balance and also serve to suppress propagation of vibration to the unit case  11 . 
         [0100]    (5) A locking portion  15 A shaped by being bent to have an L-shaped cross-section is formed in the front surface portion of the unit holding member  15  of the unit case  11  in the direction of attachment and detachment A. The locking portion  15 A can engage with the engagement hole  30 A formed in the top surface of the unit  30 . Therefore, engaging the locking portion  15 A with the engagement hole  30 A makes it possible to prevent the unit  30  mounted in the unit case  11  from slipping in the direction of attachment and detachment A. 
         [0101]    (6) Two roller members  19  are arranged on each of the front and back sides, in the direction of attachment and detachment A, of each of the bottom surface portion  12  and opposed side surface portions  13  of the unit case  11 . The roller members  19  are formed large enough to support and guide the unit  30 . This obviates the need to use long rollers, unlike those described in the conventional example, thus achieving a lightweight configuration. 
         [0102]    (7) Two roller members  19  are arranged on each of the front and back sides, in the direction of attachment and detachment A, of each of the bottom surface portion  12  and opposed side surface portions  13  of the unit case  11 . Therefore, even if any of the roller members  19  breaks down for some reason, the broken roller member need only be replaced with a new one and this prevents any serious obstacle to the operations. 
         [0103]    (8) As described with reference to  FIG. 5 , the electronic device case structure  10  according to this exemplary embodiment can produce a great noise reduction effect, as is apparent from the information obtained by sound pressure measurement using a microphone. 
         [0104]    Although the present invention has been described above with reference to an exemplary embodiment, the present invention is not limited to the above-described exemplary embodiment. Various changes that would be understood by those skilled in the art can be made to the configurations and details of the present invention. The present invention also incorporates appropriate combinations of some or all of the configurations of the above-described exemplary embodiment. 
         [0105]    For example, a locking portion  15 A shaped by being bent to have an L-shaped cross-section is formed in the front surface portion of the unit holding member  15  of the unit case  11  in the direction of attachment and detachment A. The locking portion  15 A engages with the engagement hole  30 A formed in the top surface of the unit  30 . However, the configuration of the locking portion  15 A is not limited to this. The locking portion  15 A may be formed not only in the front surface portion of the unit holding member  15  in the direction of attachment and detachment A but also on the back side, and an engagement hole which engages with the locking portion may be formed on the back side of the top surface of the unit  30  in correspondence with the locking portion  15 A, so that locking portions and engagement holes are formed in the two, front and back areas in the direction of attachment and detachment A. This makes it possible to more reliably lock the unit  30  using the two, front and back areas in the direction of attachment and detachment. 
         [0106]    Although the engagement portions  15 B are formed at the two ends of the unit holding member  15  in a direction perpendicular to the direction of attachment and detachment A to fit into the top surface portion  14  of the unit case  11 , the present invention is not limited to this. Engagement portions may be formed at, for example, the two ends of the unit holding member  15  in the direction of attachment and detachment A. 
         [0107]    In this case, the front engagement portion in the direction of attachment and detachment A can also be used as a locking portion by being formed to have the same shape and size as those of the locking portion  15 A. Therefore, bent portions need only be formed in two areas and this saves time and effort for processing. 
         [0108]    Further, although the electronic device case structure  10  is applied to the tower server device  25  in the exemplary embodiment, the electronic device case structure  10  is applicable not only to the tower server device  25  but also to general information devices. 
         [0109]    The exemplary embodiment has been described taking an HDD as a vibration generating source. However, the present invention may also be applied to general devices including movable units such as a disk drive device other than an HDD or a cooling fan. 
       (Supplementary Note 1) 
       [0110]    An electronic device case structure includes: 
         [0111]    a unit case detachably mounted with an electronic device unit which holds inside, an electronic device acting as a vibration generating source; and 
         [0112]    a unit support mechanism including a plurality of roller members implemented in a vibration-preventing member made of an elastic material, the roller members supporting the electronic device unit and guiding the electronic device unit in attaching and detaching the electronic device unit. 
       (Supplementary Note 2) 
       [0113]    The case structure according to supplementary note 1, further includes a unit holding member which is formed in an opening portion formed in the top surface of the unit case and holds down a top surface of the electronic device unit mounted in the unit case. 
       (Supplementary Note 3) 
       [0114]    The case structure according to supplementary note 2, wherein 
         [0115]    the unit case includes a quadrangular frame-shaped cross-section defined by four surrounding faces, and 
         [0116]    the roller members include four roller members mounted on each of three faces, excluding the top face, of the unit case to abut against each of three faces of the electronic device unit. 
       (Supplementary Note 4) 
       [0117]    The case structure according to supplementary note 3, wherein the unit holding member includes a locking portion which engages with an engagement hole formed in the electronic device unit and locks the electronic device unit to prevent the electronic device unit as mounted in the unit case from moving in a direction of attachment and detachment. 
       (Supplementary Note 5) 
       [0118]    The case structure according to supplementary note 4, wherein the roller members include two roller members mounted in each of a front area and a back area of each of the three faces of the unit case with a predetermined spacing therebetween in the direction of attachment and detachment. 
       (Supplementary Note 6) 
       [0119]    The case structure according to supplementary note 5, wherein the predetermined spacing is equal to a distance between two nodes at which an amplitude of natural vibration of the electronic device unit is minimal when the electronic device unit is attached to the unit case. 
       (Supplementary Note 7) 
       [0120]    The case structure according to supplementary note 6, further includes a pressing member mounted on a back surface of the unit holding member, the pressing member pressing the top surface of the electronic device unit. 
       (Supplementary Note 8) 
       [0121]    The case structure according to supplementary note 7, wherein the holding member is removably mounted in the unit case. 
       (Supplementary Note 9) 
       [0122]    The case structure according to supplementary note 8, wherein the electronic device unit is equipped with a plurality of hard disk drive devices. 
         [0123]    This application claims the benefit of priority based on Japanese Patent Application No. 2013-048952 filed on Mar. 12, 2013, the disclosure of which is hereby incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0124]    The electronic device case structure according to the present invention can be employed when an electronic device unit which holds an electronic device as a vibration generating source is attached not only to a tower server but also to general information devices. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  case structure 
           11  unit case 
           12  bottom surface portion 
           13  side surface portion 
           14  top surface portion 
           14 B engagement hole 
           15  unit holding member 
           15 A locking portion 
           16  pressing member 
           18  unit support mechanism 
           19  roller member 
           30  electronic device unit 
           35  HDD