Abstract:
A magnetic disk device is removable from an apparatus body includes a case, a driving unit, and a connector. The driving unit is installed in the case, and includes a magnetic disk and a rotary driver for rotationally driving the magnetic disk. The connector connects the driving unit and the apparatus body. The case includes an elastic supporting member and a locking member. The elastic supporting member elastically supports the driving unit. The locking member is movable between a locked position and an unlocked position, the driving unit being locked at the locked position and being unlocked at the unlocked position in the case. The locking member moves to the locked position and the unlocked position by operational force from the exterior of the case.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a magnetic disk device that incorporates a driving unit for driving a magnetic disk and can be mounted to and removed from the body of an apparatus, and an electronic apparatus including the magnetic disk device and a body for mounting the magnetic disk device thereto.  
         [0003]     2. Description of the Related Art  
         [0004]     A removable magnetic disk device that can be mounted to and removed from the body of various apparatuses is one type of magnetic disk device usable in, for example, a vehicle-installed electronic apparatus, an information appliance, or a video recorder. This type of magnetic disk device is disclosed in Japanese Unexamined Patent Application Publication No. 6-176555 and PCT Japanese Translation Patent Publication No. 2001-502103.  
         [0005]     In this type of magnetic disk device, a hard disk is mounted as a recording medium in a case formed of a hard metal or synthetic resin. In addition, a rotary driver for rotationally driving the hard disk, a magnetic head unit for recording digital signals onto the hard disk and reproducing the digital signals recorded on the hard disk, a control circuit for controlling driving operations of the rotary driver and the magnetic head unit, a digital signal processing circuit, an interface circuit, etc., are mounted in the case.  
         [0006]     The case has a predetermined thickness and a rectangular shape. Connector means connected to the various circuits is disposed at the front portion of the case.  
         [0007]     A connector for connecting with the connector means is disposed at the body of an apparatus. The various circuits in the case and circuits of the body of the apparatus are connected by mounting the magnetic disk device to the body of the apparatus and fitting the connector means at the case to the body connector.  
         [0008]     Unlike a related magnetic disk device that has a hard disk mounted thereto and is fixed in a computer or various information apparatuses, the removable magnetic disk device can be removed from the body of the apparatus. Therefore, the removed magnetic disk device needs to be protected from shock that is produced, for example, when it is dropped.  
         [0009]     As disclosed in the aforementioned Japanese Unexamined Patent Application Publication No. 6-176555 and PCT Japanese Translation Patent Publication No. 2001-502103, a dampener is installed in the case of the magnetic disk device in order to protect the rotary driver and the magnetic head unit from shock produced, for example, when the magnetic disk device is dropped.  
         [0010]     In the removable magnetic disk device, the use of a soft elastic member having a low elastic modulus is used as the dampener for protecting the rotary driver and the magnetic head unit in the case may increase the error rate of the recording operation and that of the reproducing operation.  
         [0011]     In a magnetic disk device used for high recording density, the recording track density of the hard disk is high, the recording/reproduction track width of the magnetic head is small, and the linear recording density along the tracks is high. In this type of magnetic disk device, in order to prevent damage to a recording surface of the hard disk, sliding friction force between a magnet head chip and the recording surface of the hard disk is reduced by forming an air bearing between the magnetic head chip and the recording surface of the hard disk.  
         [0012]     In recording information onto and reproducing the information from the hard disk, the magnetic head chip carries out a very precise operation. That is, it searches for a sector in a recording area of the hard disk at a high speed, and instantaneously performs tracking of tracks in the searched sector.  
         [0013]     Therefore, when the rotary driver and the magnetic head unit are supported by a soft elastic member in the case, the hard disk and the magnetic head unit tend to move due toby vibration generated when the magnetic head unit performs the aforementioned searching operation. When this occurs, the spacing between the magnetic head chip and the surface of the hard disk changes to a value equal to or greater than a standard value, and the tracking operation is affected. As a result, the error rates of data recorded on the hard disk and of data reproduced from the hard disk are increased.  
         [0014]     Consequently, it is necessary to use a hard dampener having a high elastic modulus for the dampener disposed in the case of the magnetic disk device. However, such a hard dampener cannot sufficiently protect the components in the case. As a result, a large shock applied to the magnetic disk device when, for example, it is dropped by mistake tends to result in, for example, scratching of a surface of the hard disk or damage to the magnetic head chip.  
       SUMMARY OF THE INVENTION  
       [0015]     Accordingly, it is a first object of the present invention to provide a magnetic disk device that sufficiently protects a hard disk and a magnetic head unit in a case from, for example, external shock when the magnetic disk device is not mounted to the body of an apparatus, and to prevent a dampener from adversely affecting the magnetic disk device when the magnetic disk device is mounted to the body of the apparatus. A second object of the present invention is to provide an electronic apparatus for mounting the magnetic disk device thereto.  
         [0016]     According to one embodiment of the present invention, there is provided a magnetic disk device removable from an apparatus body. The magnetic disk device comprises a case including an elastic supporting member and a locking member; a driving unit including a magnetic disk and a rotary driver for rotationally driving the magnetic disk, the driving unit being installed in the case; and a connector for connecting the driving unit and the apparatus body. The elastic supporting member elastically supports the driving unit. The locking member is movable between a lock position and an unlock position, the driving unit being locked at the lock position and being unlocked at the unlock position in the case. In addition, the locking member moves to the lock position and the unlock position by operational force from the exterior of the case.  
         [0017]     According to another embodiment of the present invention, there is provided an electronic apparatus comprising a body for mounting the magnetic disk device thereto. The body comprises a body connector for connecting with the connector of the magnetic disk device, and a switching unit for moving the locking member to the lock position when the magnetic disk device is mounted.  
         [0018]     When the magnetic disk device is removed from the body of the apparatus, the driving unit is set in an elastically supported state in the case by externally operating the locking member, thereby protecting the magnetic disk device from external shock. Immediately before mounting the magnetic disk device to the body of the apparatus or after mounting it to the body of the apparatus, the driving unit is locked in the case by operating the locking member in order to restrict unnecessary movement of the hard disk and the magnetic head unit when performing a recording operation or a reproducing operation, thereby making it possible to reduce error rate.  
         [0019]     In the magnetic disk device and the electronic apparatus for mounting the magnetic disk device in a preferred embodiment of the present invention, the locking member may be moved to the lock position and the unlock position by operation of the locking member by a user with his/her finger or by the switching unit disposed at the body of the apparatus.  
         [0020]     For example, a structure may be used in which the locking member reaches the unlock position by moving towards a front portion of the magnetic disk device relative to the case, and reaches the lock position by moving towards a rear portion of the magnetic disk device relative to the case, the front portion corresponding to a side of the magnetic disk device where the connector is disposed and the rear portion corresponding to a side opposite thereto.  
         [0021]     By virtue of such a structure, it is possible to move the locking member to the lock position by making use of mounting force is produced when the magnetic disk device is mounted.  
         [0022]     The locking member may be biased in the direction of the unlock position by a biasing member.  
         [0023]     By virtue of such a structure, the driving unit is unlocked by operating the locking member by biasing force of the biasing member, such as a spring, when the magnetic disk device is not mounted to the body of the apparatus. In addition, the driving unit may be locked by moving the locking member to the lock position against the biasing force of the biasing member when the magnetic disk device is mounted to the body of the apparatus. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is an exploded perspective view of a magnetic disk device according to an embodiment of the present invention;  
         [0025]      FIG. 2  is a perspective view showing a state of a mounting portion of the body of an electronic apparatus when the magnetic disk device is not mounted according to an embodiment of the present invention.  
         [0026]      FIG. 3  is a perspective view showing a state of the mounting portion of the body of the electronic apparatus when the magnetic disk device is mounted according to an embodiment of the present invention.  
         [0027]      FIGS. 4A and 4B  are partial enlarged perspective views illustrating a locking member in an unlocked position and a locked position, respectively. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     A magnetic disk device  1  shown in  FIG. 1  comprises a lower case portion  2 , an upper case portion  3 , and a connector case portion  4 . Each case portion is injection molded out of synthetic resin. The lower case portion  2  comprises a bottom surface  2   a , a left surface  2   b , a right surface  2   c , and a rear surface  2   d  ; has a rectangular shape; and has a recess. The front portion of the bottom surface  2   a  is formed as a fitting portion  2   e  having a somewhat smaller width. The upper case portion  3  comprises a ceiling surface  3   a , a left frame  3   b , a right frame  3   c , and a rear frame  3   d  ; has a rectangular shape; and has a shallow recess. The front portion of the ceiling surface  3   a  is formed as a fitting portion  3   e  having a somewhat smaller width.  
         [0029]     The connector case portion  4  comprises a fitting recess  4   a  at its upper surface and a fitting recess  4   b  at its lower surface. The connector case portion  4  has positioning holes  4   c  and  4   c  passing through the fitting recess  4   a  and the fitting recess  4   b . A pair of upwardly protruding positioning protrusions  5  and  5  are formed on the front portion of the bottom surface  2   a  of the lower case portion  2 . A pair of downwardly protruding positioning protrusions  6  and  6  are formed on the front portion of the ceiling surface  3   a  of the upper case portion  3 .  
         [0030]     When the fitting portion  2   e  of the lower case portion  2  is fitted to the fitting recess  4   b  of the connector case portion  4 , and the fitting portion  3   e  of the upper case portion  3  is fitted to the fitting recess  4   a  of the connector case portion  4 , the positioning protrusions  5  and  5  on the lower case portion  2  and the positioning protrusions  6  and  6  on the upper case portion  3  are vertically fitted to the positioning holes  4   c  and  4   c , so that the lower case portion  2 , the upper case portion  3 , and the connector case portion  4  are combined, thereby forming a rectangular case C having a hollow interior. The lower case portion  2  and the upper case portion  3  are secured by, for example, screws.  
         [0031]     A rectangular driving unit  10  is installed in the case C. The volume of the driving unit  10  is smaller than the volume of the space in the case C that is formed when the lower case portion  2  and the upper case portion  3  are combined. Spaces are formed between the driving unit  10  and the bottom surface  2   a , the ceiling surface  3   a , the left surface  2   b , the right surface  2   c , and the connector case portion  4 , respectively.  
         [0032]     A plurality of elastic supporting members  7  are disposed between the bottom surface  2   a  of the lower case portion  2  and the driving unit  10 . A plurality of elastic supporting members  8  are similarly disposed between the ceiling surface  3   a  of the upper case portion  3  and the driving unit  10 . It is desirable that elastic supporting members are disposed between the driving unit  10  and the left surface  2   b  of the lower case portion  2 , the driving unit  10  and the right surface  2   c  of the lower case portion  2 , and between the driving unit  10  and the rear surface  2   d  of the lower case portion  2 .  
         [0033]     Each elastic supporting member  7  and each elastic supporting member  8  is formed of soft synthetic rubber having a low elastic modulus, such as butyl rubber or silicone rubber, and is, desirably, formed of viscoelastic rubber and has a sheet shape or a columnar shape. Each elastic supporting member  7  and each elastic supporting member  8  may be a damper comprising a bag formed of a flexible material, such as rubber, and which is filled with a fluid such as air or a liquid. The driving unit  10  is elastically supported by the elastic supporting members  7  and the elastic supporting members  8  so as to be movable leftward, rightward, upward, downward, forward, or backward within a range of approximately 0.1 to 2 mm.  
         [0034]     The driving unit  10  comprises a hard case portion  11  which is thin and has a cubic shape. The hard case portion  11  is formed by bending a nonmagnetic metallic plate, or by using synthetic resin. A pair of protrusions (locks)  18  are spaced apart in the forward-and-backward directions and fixed to one of the side surfaces of the hard case portion  11 . Similarly, a pair of protrusions  18  are spaced apart in the forward-and-backward directions and fixed to the other side surface of the hard case portion  11 .  
         [0035]     A hard disk  12 , which is a magnetic disk, and a rotary driver  13 , such as a spindle motor, for rotationally driving the hard disk  12  are disposed in the hard case portion  11 . In the driving unit  10 , the hard disk  12  in the hard case portion  11  cannot be replaced and is rotationally driven in a closed space in the hard case portion  11 .  
         [0036]     A magnetic head unit  14  is installed in the hard case portion  11 . The magnetic head unit  14  comprises a magnetic head chip  14   a  opposing a magnetic recording surface of the hard disk  12 , a load beam  14   b  for applying a predetermined load pressure to the magnetic head chip  14   a , and an access actuator  14   c  for rotating the load beam  14   b  around a shaft  14   d.    
         [0037]     The magnetic head chip  14   a  comprises a slider opposing the magnetic recording surface of the hard disk  12 , a reading unit comprising a magnetoresistive element mounted to the slider, and a writing unit comprising a thin-film inductive head. In recording digital signals onto the hard disk  12 , or in reproducing the digital signals from the hard disk  12 , the magnetic head chip  14   a  floats slightly through an air bearing at the surface of the hard disk  12  rotating at a high speed. Then, the load beam  14   b  is rotated by the access actuator  14   c , so that the magnetic head chip  14   a  searches for a sector on the magnetic recording surface of the hard disk  12 , and the reading unit or the writing unit performs a tracking operation in order to read or write the signals.  
         [0038]     A circuit board (not shown) is mounted in the hard case portion  11 , and has various circuits mounted thereto. The various circuits include a control circuit for controlling a driving operation of the rotary driver  13 ; a control circuit for controlling the operation of the magnetic head unit  14 ; a digital signal processing circuit for, for example, formatting a write signal and deformatting a read signal; and an interface circuit.  
         [0039]     A connector  16  is installed in the connector case portion  4 . Each terminal of the connector  16  and each of the circuits in the driving unit  10  are in electrical conduction through an electrically conductive pattern on a flexible printed circuit board  17 . The flexible printed circuit board  17  is in a slightly flexed state, and can allow the driving unit  10  to move in the magnetic disk device  1 . The flexible printed circuit board  17  also operates as an elastic supporting member for elastically supporting the driving unit  10  in the case C.  
         [0040]     A groove  21  is continuously formed in the forward-and backward-directions from the left surface of the connector case portion  4  to the outer side of the left surface  2   b  of the lower case portion  2 . A slit  22  passing through the left surface  2   b  of the lower case portion  2  and extending in the forward-and-backward directions is opens in the groove  21 . Similarly, a groove  21  and a slit  22  are also formed in the right surface of the connector case portion  4  and in the right surface  2   c  of the lower case portion  2 .  
         [0041]     A locking member  23  is disposed at the inner side of the left surface  2   b  of the lower case portion  2 . The locking member  23  is supported by guide means (not shown) so as to be movable towards the front and back along the left surface  2   b . A switching protrusion  23   a  is integrally formed with the outer surface of the locking member  23 , and is exposed in the groove  21  through the slit  22 . The slit  22  is wider than the switching protrusion  23   a  in the forward-and-backward directions, so that the switching protrusion  23   a  can slide in the slit  22  in the forward-and-backward directions. Therefore, when a user moves the switching protrusion  23   a  with his/her finger towards the front or the back, the locking member  23  slides towards the front or the back in the case C.  
         [0042]     Lock grooves  23   b  that are spaced apart in the forward-and-backward directions are formed in the locking member  23 . Each lock groove  23   b  has a recess which opens at the back. The lock grooves  23   b  oppose the protrusions (locks)  18  protruding from the associated left surface of the driving unit  10 . Similarly, a locking member  23  which moves in the forward-and-backward directions is also formed at the inner side of the right surface  2   c  of the lower case portion  2 . This locking member  23  also has a switching protrusion  23   a  and lock grooves  23   b . Although in this embodiment the two locking members  23  operate separately, it is desirable that the locking members  23  both move together in the forward-and-backward directions by integrally connecting both of the locking members  23 .  
         [0043]      FIGS. 2 and 3  illustrate a mounting portion  30  in an apparatus body  100  for removably mounting the above-described magnetic disk device  1 .  
         [0044]     The mounting portion  30  comprises a mounting frame  31 . The mounting frame  31  is formed by bending a metallic plate, and comprises a bottom plate  31   a,  a left plate  31   b,  and a right plate  31   c.  An engager  31   d  is formed by bending the top end portion of the left plate  31   b  inward, and an engager  31   e  is formed by bending the top end portion of the right plate  31   c  inward. The engager  31   d  moves into the groove  21  in the left surface  2   b  of the magnetic disk device  1 , and the engager  31   e  moves into the groove  21  in the right surface  2   c  of the magnetic disk device  1 . The rear end of the engager  31   d  and the rear end of the engager  31   e  are formed as a first engager portion  31   d   1  and a first engager portion  31   e   1 , respectively.  
         [0045]     A flat sliding member  32  is disposed on the bottom plate  31   a.  A guide slot  33  extending in a straight line in forward and backward is formed in the sliding member  32 . The sliding member  32  is slidable in the forward and backward by guiding the guide slot  33  by guide protrusions  34  secured to the bottom plate  31   a.  The left and right front end portions of the sliding member  32  are bent upwards at right angles to form contacts  32   a.    
         [0046]     A pair of switching holes  35  that are spaced apart are formed, one at the right ride and one at the left side of the rear portion of the sliding member  32 . Each switching hole  35  comprises a non-engaging switching portion  35   a , an engaging switching portion  35   b , and an inclined portion  35   c . The non-engaging switching portions  35   a  oppose each other with a certain distance therebetween and extend parallel to each other in the forward-and-backward directions. The engaging switching portions  35   b  are disposed behind the non-engaging switching portions  35   a , oppose each other with a distance therebetween that is smaller than the certain distance, and extend parallel to each other in the forward-and-backward directions. The inclined portions  35   c  connect the corresponding non-engaging switching portions  35   a  and the corresponding engaging switching portions  35   b.    
         [0047]     As shown in  FIG. 3 , a pair of engaging plates  41  are disposed at the lower surface of the bottom plate  31   a.  The engaging plates  41  are guided by a guide mechanism (not shown) and are supported so as to be slidable in the forward-and-backward directions and in the leftward-and-rightward directions perpendicular thereto. Sliding protrusions  42  are secured to the respective engaging plates  41 , and are inserted in the respective switching holes  35  of the sliding member  32  through respective guide holes  43  (see  FIG. 3 ) that are formed in a straight line towards the left and right in the bottom plate  31   a.    
         [0048]     Engagers  41   a  which are formed at right angles are integrally formed with ends of the respective engaging plates  41 , and operate as second engager portions.  
         [0049]     In this embodiment, the first engager portions  31   d   1  and  31   e   1  operate as first switching portions that allow the locking members  23  to move backward relative to the case C in the magnetic disk device  1  and reach lock positions. The engagers  41   a,  which are second engager portions operate as second switching portions which allow the locking members  23  to move forward relative to the case C and reach unlock positions. As described later, by the first switching portions and the second switching portions, the locking members  23  move from the unlock positions to the lock positions when the magnetic disk device  1  is inserted into the apparatus body  100 , whereas the locking members  23  move from the lock positions to the unlock positions when the magnetic disk device  1  is removed from the apparatus body  100 .  
         [0050]     The engaging plates  41 , the sliding protrusions  42 , and the switching holes  35  formed in the sliding member  32  operate as a switching setting mechanism for engaging the engagers  41   a,  which are second engager portions, with the respective locking members  23  by moving the engagers  41   a  towards each other, and for disengaging the engager portions  41   a  from the respective locking members  23  by moving the engager portions  41   a  and  41   a  away from each other.  
         [0051]     As shown in  FIG. 3 , a slot  3  If extending in the forward-and-backward directions is formed in the left plate  31   b.  A protrusion  32   b  is integrally formed with the sliding member  32 , and protrudes towards the left and outwards from the slot  31   f.  An ejector  45  for pushing the protrusion  32   b  backwards is disposed at the outer side of the left plate  31   b . It is desirable that the sliding member  32  be biased backwards by a weak spring material as shown in  FIG. 2 .  
         [0052]     A body connector  50  is disposed in front of the mounting frame  31 . A fitting portion  51  of the body connector  50  faces backward.  
         [0053]     Next, the mounting of the magnetic disk device  1  will be described.  
         [0054]      FIGS. 4A and 4B  are partial perspective views for describing the mounting of the magnetic disk device  1 . Here, the lower case portion  2  of the magnetic disk device  1 , the sliding member  32  disposed at the mounting portion  30 , etc. are not shown. The relationship between the driving unit  10  and the locking member  23  in the magnetic disk device I is only illustrated. In the mounting portion  30 , the operations of the first engager portion  31   d   1  and the engager  41   a  are only described. Since the operation of the locking member  23  disposed at the right surface  2   c  of the lower case portion  2  is the same as the operation of the locking member  23  shown in  FIGS. 4A and 4B , only the operation of the locking member  23  at the left surface  2   b  will be described.  
         [0055]     When the magnetic disk device  1  is not mounted to the mounting portion  30  of the apparatus body  100 , and before the magnetic disk device  1  is completely mounted to the mounting portion  30 , in the magnetic disk device  1 , as shown in  FIG. 4A , the locking member  23  is at the unlock position which it reaches by moving forward, and the protrusions (locks)  18  are not inserted in the respective lock grooves  23   b  of the locking member  23 . Therefore, in the case C of the magnetic disk device  1 , the driving unit  10  is elastically supported by the elastic supporting members  7  and the elastic supporting members  8 .  
         [0056]     A structure for increasing the sliding load of the locking member  23  with the locking member  23  and a sliding plate spring (not shown) being fixed in the lower case portion  2  may be used as means for stabilizing the locking member  23  at the unlock position shown in  FIG. 4A  when the magnetic disk device  1  is not mounted to the mounting portion  30 . It is desirable to use a structure for stabilizing the locking member  23  at the unlock position by biasing the locking member  23  by biasing force of a biasing member, such as a pulling force of a pulling coil spring S (see  FIG. 1 ) or a pushing force of a compression coil spring, in the forward direction (that is, in the direction f in  FIG. 4B ).  
         [0057]     When the magnetic disk device  1  is not mounted to the mounting portion  30  of the apparatus body  100 , the driving unit  10  in the case C is elastically supported by the elastic supporting members  7  and the elastic supporting members  8  without being locked by the locking member  23 . Therefore, even if a large shock is accidentally applied to the magnetic disk device  1 , it is possible to prevent an excessive shock from being directly applied to the driving unit  10 . Consequently, it is possible to prevent a surface of the hard disk  12  from becoming damaged due to collision with the magnetic head chip  14   a , or to prevent the magnetic head chip  14   a  from becoming damaged.  
         [0058]     When the magnetic disk device  1  is not mounted to the apparatus body  100 , as shown in  FIG. 2 , the sliding member  32  is moved back in the mounting portion  30 . At this time, since the sliding protrusions  42  at the respective engaging plates  41  are positioned in the non-engaging switching portions  35   a  of the respective switching holes  35  in the sliding member  32 , the engaging plates  41  are moved outwards to the left and right, respectively, and are disposed away from each other. Therefore, when the magnetic disk device  1  is mounted to the mounting portion  30 , the engagers  41   a  will not prevent insertion of the magnetic disk device  1 .  
         [0059]     The magnetic disk device  1  having its connector case portion  4  faced forward is inserted into the mounting portion  30  from an insertion opening  101  of the apparatus body  100  shown in  FIG. 2 . In the insertion of the magnetic disk device  1 , the engager  31   d  bent at the left plate  31   b  and the engager  31   e  bent at the right plate  31   c  move into the groove  21  in the left surface  2   b  and the groove  21  in the right surface  2   c  of the lower case portion  2  shown in  FIG. 1 , respectively. While being guided by the engagers  31   d  and  31   e,  the magnetic disk device  1  is inserted. Accordingly, the engagers  31   d  and  31   e  function as guide members when mounting the magnetic disk device  1  to or ejecting it from the mounting portion  30 .  
         [0060]     When the magnetic disk device  1  is inserted, and the front surface of the connector case portion  4  strikes the contacts  32   a  of the sliding member  32  shown in  FIG. 2 , the sliding member  32  thereafter moves forward along with the magnetic disk device  1  by the force that is generated by the insertion of the magnetic disk device  1 .  
         [0061]     When a front end  23   a   1  of the switching protrusion  23   a  protruding in the groove  21  in the left surface  2   b  of the magnetic disk device  1  contacts the first engager portion  31   d   1  at the rear end of the engager  31   d,  or immediately before or after the contact, as shown in  FIG. 3 , the sliding protrusions  42  move into the engaging switching portions  35   b  of the respective switching holes  35  in the sliding member  32 , so that the engaging plates  41  move towards each other. Therefore, as shown in  FIG. 4B , after the switching protrusion  23   a  on the locking member  23  has moved forward along the inner side of the engager  41   a,  when the front end  23   a   1  contacts the first engager portion  31   d   1  or immediately before or after the contact, the engager  41   a  moves into a vertical groove  21   a  in the left surface  2   b  shown in  FIG. 1 , and opposes a rear end  23   a   2  of the switching protrusion  23   a  with a slight gap therebetween.  
         [0062]     When the magnetic disk device  1  is further inserted into the apparatus body  100  towards the body connector  50 , the whole magnetic disk device  1  moves forward while the switching protrusion  23   a  on the locking member  23  engaging the first engager portion  31   d   1  does not move. Therefore, as shown in  FIG. 4B , the protrusion  18  on the driving unit  10  moves from a position  18 - 1  to a position  18 - 2  where it is inserted in the lock groove  23   b . In other words, in the magnetic disk device  1 , the locking member  23  moves backward relative to the case C and reaches the lock position where the driving unit  10  is locked in the case C. The front end of the connector  16  at the front portion of the driving unit  10  is fitted to the body connector  50 .  
         [0063]     Therefore, with the magnetic disk device  1  being mounted to the mounting portion  30 , the driving unit  10  is secured, and recording and reproducing of information are carried out in the magnetic disk device  1 . Here, with the driving unit  10  being locked by the locking member  23  in the case C, the hard disk  12  is rotationally driven to operate the magnetic head unit  14 . Therefore, it is possible to prevent, for example, the recording surface of the hard disk  12  from becoming scratched or the magnetic head chip  14   a  from becoming damaged when the hard disk  12  or the magnetic head unit  14  is inadvertently moved due to, for example, vibration.  
         [0064]     When the magnetic disk device  1  is ejected from the apparatus body  100 , the ejector  45  shown in  FIG. 3  is moved backward, for example, by direct operation of the ejector  45  by the user, or by motor power. At this time, the ejector  45  pushes the protrusion  32   b  backward, causing the sliding member  32  to slide backward. The contacts  32   a  of the sliding member  32  push back the magnetic disk device  1  along with the sliding member  32 , so that the connector  16  of the magnetic disk device  1  is separated from the body connector  50 .  
         [0065]     At this time, the magnetic disk device  1  moves backward while the locking member  23  is stopped by the engagement of the rear end  23   a   2  of the switching protrusion  23   a  of the locking member  23  with the engager  41   a.  Therefore, the protrusion  18  moves from the position  18 - 2  to the position  18 - 1  shown in  FIG. 4B , and moves out of the lock groove  23   b  in the locking member  23 , so that the driving unit  10  is elastically supported by the elastic supporting members  7  and the elastic supporting members  8  in the case C. In other words, in the magnetic disk device  1 , the locking member  23  moves forward relative to the case C and reaches the unlock position.  
         [0066]     Backward movement of the sliding member  32  immediately after the protrusion  18  has moved out of the lock groove  23   b  causes the sliding protrusions  42  to move into the non-engaging switching portions  35   a  of the respective switching holes  35 . This causes the engaging plates  41  to move towards the left and right, respectively, so that the engagers  41   a  move away from their respective switching protrusions  23   a . By this, the magnetic disk device  1  can be removed from the mounting portion  30 . That is, the magnetic disk device  1  can be removed from the insertion opening  101  of the apparatus body  100 .  
         [0067]     The present invention is not limited to the above-described embodiment. Rather, various modifications can be made.  
         [0068]     For example, in the magnetic disk device  1 , when the magnetic disk device  1  is not mounted to the mounting portion  30 , if the locking member  23  is stabilized at the unlock position by the biasing force of the biasing member, such as the pulling coil spring S or the compression coil spring, in the direction in which the protrusion  18  moves out of the lock groove  23   b  (that is, the direction f in  FIG. 4B ), the engager (second engager portion)  41   a  does not necessarily have to be used.  
         [0069]     In this case, if the first engager portions  31   d   1  and  31   e   1  are provided, while the magnetic disk device  1  is being inserted into the mounting portion  30 , the front end  23   a   1  of the switching protrusion  23   a  and a front end  23   a   1  of the switching protrusion  23   a  strike the first engager portions  31   d   1  and  31   e   1 , respectively. Thereafter, by the force produced by inserting the magnetic disk device  1 , the locking members  23  are moved to the lock positions against the biasing force of the corresponding biasing member and that of a corresponding biasing member in the magnetic disk device  1 . Then, when the magnetic disk device  1  is removed from the mounting portion  30 , the locking members  23  automatically move to the unlock positions by the biasing force of the biasing members.  
         [0070]     In this case, it is desirable to provide, for example, a pushing member for holding down the rear surface  2   d  of the mounted magnetic disk device  1  so that, while the magnetic disk device  1  is mounted to the mounting portion  30 , the magnetic disk device  1  is prevented from moving away from the body connector due to opposing force of the biasing members which bias the respective locking members  23 .  
         [0071]     It is to be understood that a wide range of changes and modifications to the embodiments described above will be apparent to those skilled in the art and are contemplated. It is therefore intended that the foregoing detailed description be regarded as illustrative, rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of the invention.