Patent Publication Number: US-2003227718-A1

Title: Suspension and disk unit

Description:
[0001] This application is a continuation based on PCT International Application No. PCT/JP00/09081, filed on Dec. 20, 2000, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.  
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates generally to a mechanism for moving a head over a recordable medium, and more particularly to a structure of a suspension that supports the head. The present invention is suitable, for example, for a suspension that supports a magnetic head in a magnetic disc unit.  
       [0003] Recent electronic apparatuses have been increasingly required to handle mass data, such as images and voices. A hard disc drive (“HDD”) used for such electronic apparatuses is a typical mass auxiliary storage that provides random accesses as well as sequential accesses. The HDD typically includes a disc that attaches magnetic materials, a swingable head arm (or sometimes referred to as an actuator), a suspension connected to the head arm, and a magnetic head supported on the suspension. The magnetic head includes a minute head core that records and reproduces signals, and a slider that supports the head core. The arm is attached to a proximal end of the suspension, and the slider is attached to a distal end of the suspension. The suspension also serves as a flat spring that presses the slider against a disc with a certain compression force. When the disc stops, the slider contacts the disc due to the compression force by the suspension. When the disc rotates, the associative airflow occurs between the slider and the disc, and floats the slider from the disc surface. A balance between the floating force and the compression force spaces the floating slider from the disc at a certain distance from the disc. In this state, the arm rotates or seeks to move the magnetic head to a target position on the disc to access (i.e., read and write) the disc.  
       [0004] Winchester, known as a current HDD interface, is characterized, for example, in a medium fixation that cannot exchange a disc, a contact start stop (“CSS”) that enables a head to contact a disc when the disc stops and to float the head from the disc when the disc rotates, and a decreased compression force by a suspension to reduce friction applied to the head at the time of start and stop. Stable recording and reproducing with this interface requires control over a constant head floating amount or improved resonance characteristic (or torsional vibration) of a head. The torsional vibration would offset a position of a head attached to the slider from a target position on the disc, and unstably vary an interval between the head and the disc, causing inaccessibility.  
       [0005] The conventional HDD typically uses a suspension and dynamic pressure fluid lubrication to control the flying height.  
       [0006] A distance between the disc and the head arm is called “Z height”, and the suspension absorbs a fluctuation of a direction of the Z height, i.e., direction Z. A Watlas type suspension as one typical suspension connects a rigid head to a rigid head arm through a flexure (also referred to as a gimbal or another name) and a load beam (also referred to as a load arm or another name). The suspension is a combination of the flexure and the load beam. The load beam includes a (flat) spring section only at its center to apply sufficient compression force in the direction Z. Therefore, the load beam includes a rigid section at its proximal end, the spring section at its center, and a rigid section at its distal end. Since the slider surface follows warp and swell on the disc and should be always parallel to the disc surface, the load beam contacts the flexure through a dimple (also referred to as a pivot or another name), and the magnetic head is designed to softly pitch and roll around the dimple. Thus, the suspension is designed to be soft to Z-height fluctuations, pitching and rolling, and rigid to motions of other shafts. The resonance mode of the rigid section is torsional deformation at the proximal end of the load arm.  
       [0007] The dynamic pressure (fluid) lubrication arranges a head to form a cuneate or wedge aperture in the airflow associated with a rotation of a disc. Since the resonance frequency of an air film during floatation is larger, e.g., 20 to 40 kHz, than that of the suspension, the air film does not resonate prior to the suspension in principle. In addition, even when the air film vibrates, the recording frequency is remarkably larger, e.g., 1 to 15 MHz, than the resonance frequency, and the high-pass filter may easily eliminate the reproduction output oscillation generated from the air flow vibrations.  
       [0008] Conventional methods that minimize the torsional vibration include a method that makes the suspension strong to the torsional rigidity and increases the resonance frequency (see U.S. Pat. No. 5,793,569), and a method that modifies a shape of the suspension to reduce the torsion (see U.S. Pat. Nos. 6,023,574 and 5,991,122), and a method that provides a weight near the head to reduce the torsion at the resonance point (see Japanese Laid-Open Patent Application No. 56-117369).  
       [0009] However, a high seek speed associated with the recent mass storage of the hard disc remarkably increases influence of the torsional vibration on the conventional suspension. The torsional vibration occurs when the proximal end or rigid section of the suspension twists in a direction other than the direction Z and the twist propagates to the flexure although the proximal end does not deform in the direction Z. Even when the resonance frequency of the suspension increases as in the conventional proposals, the torsional vibration necessarily occurs at the resonance frequency. A method using a weight is effective to prevent twisting at the resonance point, but use of the weight would increase the number of components.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010] Accordingly, it is a general object of the present invention to provide a novel and useful suspension and disc unit in which the above disadvantages are eliminated.  
       [0011] Another exemplified and more specific object of the present invention is to provide a suspension and a disc unit in which a head is unsusceptible to any torsion that occurs at the rigid section.  
       [0012] In order to achieve the above objects, a suspension arm as one exemplified embodiment of the present invention includes a load beam that connects a head to a head arm, the head recording data onto and reproducing data from a disc, the head arm moving the head to a target position on the disc, the load beam compressing the head against the disc with a certain compression force, a flexure that supports the head, and a dimple as a projection that enables the load beam to point-contact the flexure, and the head to pitch and roll around the dimple, wherein the load beam includes a spring section that applies the compression force, a rigid section that extends from the spring section to a side opposite to the head arm, and is more rigid than the spring section in a direction that fluctuates a distance between the head arm and the disc; and a balancer section connected to the dimple and more elastic than the rigid section in the direction, the balancer section extending from the rigid section to a side of the rigid section opposite to the spring section. This Watlas type suspension uses the balancer section that is more elastic than the rigid section to absorb torsion generated in the rigid section, and does not propagate the torsion to the head supported by the balancer section. Optionally, the balancer section may be provided with a weight. This weight is provided approximately symmetrical to the head with respect to the balancer section, thereby securing weight balance of the balancer section and mechanically stabilizing the balancer section.  
       [0013] A suspension of another aspect of the present invention provides the above suspension with a preamp chip, connected to the load beam, which amplifies a signal to be sent to the head. This suspension may exhibit operations similar to those of the above suspension provided with the weight and may reduce influence of noises by arranging the head close to the preamp chip. Therefore, similar to the weight, the preamp chip may be provided approximately symmetrical to the head with respect to the balancer section. The suspension may further include wiring, such as an FPC, at a side of the load beam opposite to the disc, to electrically connect the preamp chip with the head, thereby securing weight balance of the balancer section and mechanically stabilizing the balancer section. In this case, the balancer section includes a through-hole, through which the wiring may be electrically connected to the head, thereby securing weight balancing and electrical connections between the head and the preamp chip.  
       [0014] A suspension of still another aspect of the present invention includes a load beam that connects a head to a head arm, the head recording data onto and reproducing data from a disc, the head arm moving the head to a target position on the disc, the load beam compressing the head against the disc with a certain compression force, a flexure that supports the head, a dimple as a projection that enables the load beam to point-contact the flexure, and the head to pitch and roll around the dimple, and a preamp chip, connected to the load beam, which amplifies a signal to be sent to the head, wherein the preamp chip is located symmetrical to the head with respect to the load beam. This suspension has a short distance between the head and the preamp chip, and reduces the influence of noises.  
       [0015] A disc unit of still another aspect of the present invention includes a head that records data onto and reproduces data from a disc, a head arm that moves the head to a target position on the disc, and any of the above suspensions, connected to the head arm, which supports the head. This disc unit includes the above suspension, and exhibits similar operations. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016]FIG. 1 is a schematic perspective view of a suspension of one embodiment according to the present invention.  
     [0017]FIG. 2 is an exploded perspective view of the suspension shown in FIG. 1.  
     [0018]FIG. 3 is a schematic plane view of the inside of a disc unit of another aspect according to the present invention, which includes the suspension shown in FIG. 1.  
     [0019]FIG. 4 is a schematic perspective view of a variation of the suspension shown in FIG. 1.  
     [0020]FIG. 5 is an exploded perspective view of the suspension shown in FIG. 4.  
     [0021]FIG. 6 is a view for explaining a function of a weight of the suspension shown in FIG. 4.  
     [0022]FIG. 7 is a graph that indicates a swinging degree of a head to the weight obtained using a finite element method analysis when the weight of the suspension shown in FIG. 4 moves in a direction X 2 .  
     [0023]FIG. 8 is a schematic perspective view of a load beam as a variation of a load beam in the suspension shown in FIG. 4.  
     [0024]FIG. 9 is a view for explaining weight balancing of the balancer section when the load beam shown in FIG. 8 is applied to the suspension.  
     [0025]FIG. 10 is a graph that indicates a swinging degree of a head obtained using a finite element method analysis when the weight of the suspension shown in FIG. 4 moves in a direction X 2 .  
     [0026]FIG. 11 is a schematic perspective view of a variation of the suspension shown in FIG. 1.  
     [0027]FIG. 12 is a schematic perspective view of a rear side of the suspension shown in FIG. 11.  
     [0028]FIG. 13 is an exploded perspective view of the suspension shown in FIG. 11.  
     [0029]FIG. 14 is an exploded perspective view of a suspension as a variation of an FPC shown in FIG. 5.  
     [0030]FIG. 15 is a schematic perspective view of the suspension shown in FIG. 11 that has a through-hole.  
     [0031]FIG. 16 is a view of a controller of the disc unit shown in FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0032] A description will now be given of a suspension  100  and a disc unit  200  having the suspension  100  of one embodiment according to the present invention, with reference to FIGS.  1  to  3 . FIG. 1 is a schematic perspective view of the suspension  100 . FIG. 2 is an exploded perspective view of the suspension  100 . FIG. 3 is a schematic plane view of an internal construction of a disc unit  200  that includes the suspension  100 . In each figure, those elements which are the same are designated by the same reference numerals, and a duplicated description thereof will be omitted. The same reference numerals with an alphabetic letter attached thereto generally designate a variation of the elements identified by the reference numeral without an alphabetic letter, and reference numerals without an alphabetic letter, unless otherwise specified, comprehensively designate the element identified by the reference numerals with an alphabetic letter.  
     [0033] As best shown in FIG. 2, the suspension  100  is a Watlas type suspension that includes a load beam  110 , a dimple  125 , and a flexure  130 . The load beam  110  is connectible to a head arm  220  shown in FIG. 3, and compresses the head  210  against the disc  240  with a predetermined compression force. The flexure  130  supports the head  210 . The dimple  125  is a projection that enables the load beam  110  to point-contact the flexure  130 , and the head  210  to pitch and roll around the dimple  125 .  
     [0034] The load beam  110  is an approximately triangular plate member, and a side of the connection section  112  is exemplarily wider than the side of the balancer section  116 . Preferably, the load beam  110  is made of elastic members, such as stainless (“SUS”). The instant embodiment makes the load beam  110  of SUS 304. The load beam  110  includes, as shown in FIG. 2, a connection section  112 , a spring section  114 , a rigid section  116 , and a balancer section  120  in a direction X 1 .  
     [0035] The connection section  112  is located at a proximal end of the suspension  100 , which is part attachable to the head arm  220 . The connection section  112  has an area that may stably connect the load beam  110  to the arm  220 . The connection section  112  attached to the head arm  220  is rigid in a direction Z, i.e., directions Z 1  and Z 2 , in which a Z height fluctuates, which is a distance between the head arm  220  and the disc  240  as will be described later, and has a resonance frequency of about 1800 Hz. The connection section  112  is attached to the arm  220  using, for example, a screw.  
     [0036] The spring section  114  is an elastically deformable flat spring that extends from the connection section  112  in the direction X 1 . The spring section  114  applies a certain sufficient compression force, such as about 20 mN, to the head  210  against the disc  240  so that the mass of the head  210 , such as about 15 mg, does not affect the flying height. The spring section  114  has a resonance frequency of about 300 Hz, and has, for example, a flat plate shape. However, this shape is exemplary and nonrestrictive if it may apply the above compression force. For example, the spring section  114  has a shape having a curvature bending and inclining a top of the load beam  110  (or a side of the balancer section  120 ) to the side of the disc  240 , a shape having a neck in the direction Z, or a waveform shape.  
     [0037] The spring section  114  has a certain sized opening  115  at its center. The size of the opening  115  is determined by the elasticity of the spring section  114 : The opening  115  is made large for high elasticity, while the opening  115  is made small for low elasticity. It is optional to provide an opening  115 , and the opening  115  may be omitted if the spring section  114  may serve as the flat spring without the opening  115 .  
     [0038] A provision of the opening  115  at the center of the spring section  114  would reduce its rigidity, and use of its elasticity (or a SUS material) enables the spring section  114  to serve as a flat spring with a certain spring pressure. Since the spring section  114  has the above curvature, when the force is applied in the direction Z 2  to the top of the load beam  110  at the side of X 1  or the balancer section  120 , the load beam  110  repulses in the direction Z 1  due to the spring pressure of the spring section  114 . Therefore, a balance between the compression force applied by the spring section  114  and the floating force of the head  210  associated with a rotation of the disc  240  maintains the flying height of the head  210  from the disc  240  to be constant.  
     [0039] The rigid section  116  extends from the spring section  114  in the direction X 1 , and is more rigid than the spring section  114  in the direction Z. A pair of rib sections  117  that are formed by bending both ends of the rigid section  116  enhance the rigidity of the rigid section  116 . The rigid section  116  with these rib sections  117  has an approximately U-shape section when viewed from the direction X 2 . The rigid section  116  effectuates the compression force by the spring section  114 , and prevents the load beam  110  from easily twisting.  
     [0040] A shape and structure of the rigid section  116  are not limited if they may enhance the rigidity of the load beam  110 . For example, whether the rigid section  116  has the rib sections  117  is optional, and the rib sections  117  may be omitted when the rigid section  116  is made of a highly rigid material in forming the load beam  110 . Alternatively, one or more flat plates each having the same shape as that of the rigid section  116  may be piled on the rigid section  116 , or a rod member may be arranged as a reinforcing member at the rigid section  116 .  
     [0041] The balancer section  120  is located adjacent to the rigid section  116  in the direction X 1 , and opposite to the connection section  112  of the load beam  110 . The balancer section  120  has approximately the same area as or slightly larger area than the head  210 . The rib sections  117  formed on the rigid section  116  do not extend to the balancer section  120 .  
     [0042] As discussed, the balancer section  120  is not provided with the rib sections  117  as on the rigid section  116 , and exposes its elastic feature more remarkably than the balancer section  120 . Therefore, when the load beam  110  twists and the rigid section  116  twists, the elastic feature absorbs torsion and the balancer section  120  is less affected by the propagated torsion. In other words, the reduced rigidity at the tip of the load beam  110  would prevent the torsion from transmitting to the balancer section  120 , and reduce the influence of the torsion, such as swing, on the head  210  above the balancer section  120 .  
     [0043] The thus structured load beam  110  of the inventive suspension  100  controls actions of the head  210  in the direction Z. For example, the inventive load beam  110  obtains the compression force from the spring pressure by the spring section  114 , and may flexibly deform on a few concaves and convexes on the surface of the disc  240 . The rigid section  116  would make rigid actions of the load beam  110  in other axes. The inventive load beam  110  is provided with the balancer section  120  at its tip, may absorb torsion generated in the load beam  110 , and prevent the torsion from transmitting to the head  210 .  
     [0044] The dimple  125  is located as an approximately trigonal pyramid projecting toward the disc  240  at an approximately center of the balancer section  120  in this embodiment. The dimple  125  supports the flexure  130  at its projection tip, and provides the head  210  mounted on the flexure  130  with a degree of freedom of pitching and rolling. More specifically, this structure enables the dimple  125  to point-contact the flexure  130 . Therefore, the flexure  130  and the balancer section  120  have relative degree of freedom around the tip of the dimple  125 . When the head  210  floats from the disc  240 , the load beam  110  swings around the contact with the flexure  130  even when the torsion is applied to the load beam  110 , thereby preventing the influence of the torsion from transmitting to the head  210 . The dimple  125  may have an exemplary cone shape, but the dimple  125  may be shaped like a semi-sphere that provides a degree of freedom to the head  210 .  
     [0045] The flexure  130  is a flat plate member, and typically includes a head mounting section  132 . The flexure  130  is located on a top surface  111  of the load beam  110  so that the head mounting section  132  is located on the dimple  125  on the balancer section  120 . It is basically sufficient that the flexure  130  has an area enough to mount the head  210 , but the instant embodiment provides the flexure  130  with an elongated section  138  that extends in the direction X 2 . The flexure  130  in this embodiment has a wiring pattern  134  on the elongated section  138 . Of course, the flexure  130  does not necessarily include the elongated section  138  and wiring pattern  134 , and this structure is illustrative. The flexure  130  in the instant embodiment is made of the same stainless, e.g., SUS304, similar to the load beam  110 .  
     [0046] The flexure  130  is located between the head  210  and the dimple  125 , and serves as a bottom plate that arranges the head  210  on the dimple  125 . The flexure  130  in the instant embodiment serves as a printed board of the electric wiring  136  that is connected to the head  210  on the above elongated section  138 .  
     [0047] The head mounting section  132  has approximately the same area as the head  210 , and located at the top of the flexure  130  in the direction X 1 . The head mounting section  132  may mount the head  210  onto the flexure  130 . The head mounting section  132  includes a terminal connection section  133  that electrically connects the head core in the head  210  and the wiring pattern  134  to each other. The terminal connection section  133  is connected electrically to an end of the wiring pattern  134  and the head  210  when the head  210  provided with the head core is mounted on the head mounting section  132 . The head mounting section  132  includes a projection contact section  139  at an approximately center of the head mounting section  132  along a center axis (indicated by a dotted line in FIG. 2). The projection contact section  139  contacts the dimple  125  on the above balancer section  120  on the rear surface of the flexure  130  when the flexure  130  is located on the load beam  110 . The projection contact section  139  may be one point on the head mounting section  132 , or a dent that is engaged with the top of the dimple  125 .  
     [0048] The wiring pattern  134  is an aggregate of plural wires  136 , and formed on the elongated section  138  on the top surface  131  of the flexure  130 . One end of the wiring  136  is located at the terminal connection section  133  on the head mounting section  132 . The other end of the wiring  136  extends from the flexure  130  and is connected to the control section  250 . The wiring pattern  134  may use any technology known in the art, and a detailed description will be omitted. The above wiring pattern  134  does not have to be printed on the elongated section  138  on the flexure  130 , and the elongated section  138  may be omitted and the wiring  136  may be printed on the top surface  111  on the load beam  110 .  
     [0049] The suspension  100  arranges the flexure  130  on the top surface  111  on the load beam  110 , and the head  210  and head core, which will be described later, on the head mounting section  132  on the top surface  131  of the flexure  130 . It is understood that the head core is so small that it is not illustrated in the drawing. The suspension  100  is formed symmetrical with respect to a dotted line shown in FIG. 1 so as to prevent the suspension  100  from twisting. The suspension  100  is connected to the head arm  230  of the disc unit  200 , which will be described later, at the side of the top of the slider  122  or the side in the direction X 1 . The suspension  100  serves to compress the head  210  against the disc  240  in the direction Z 1 , balance the floating force, and maintain the interval between the slider  120  and the disc  240  to be constant.  
     [0050] Referring now to FIGS. 4 and 5, a description will be given of a suspension  100 A as a variation of the inventive suspension  100 . Here, FIG. 4 is a schematic perspective view of the suspension  100 A as a variation of the suspension  100  shown in FIG. 1. FIG. 5 is a schematic perspective view of the hierarchical structure of the suspension  100 A shown in FIG. 4. The suspension  100 A has basically the same structure as the suspension  100 , but is different from the suspension  100  in that it has a weight  150 . Other than that, it is the same as the suspension  100 A, and a detailed description will be omitted. The suspension  100 A serves to more effectively prevent the torsion of the suspension  100  associated with seeking.  
     [0051] The weight  150  has a certain mass “m”, and is located opposite to the dimple  125  of the balancer section  120 . The weight “m” of the weight  150  is set for weight balance of the balancer section  120 , as described later. The weight  150  is located just below the head  120  and its vicinity. A shape of the weight  150  is not limited if it may be arranged on the balancer section  120 . The weight  150  serves to maintain the weight balance of the balancer section  120 .  
     [0052] Referring to FIG. 6, a detailed description will be given of this function. Here, FIG. 6 is a view for explaining a function of the weight  150  of the suspension  100 A shown in FIG. 4. The suspension  100 A is excited in a direction S (that generalizes directions S 1  and S 2 ) associated with seeking. For example, when it is excited in the direction S 2  by a force F (with acceleration “a”), the bending moment occurs at the top surface  11  and bottom surface  12  associated with the force F with respect to the excitation reference axis  10  as a basis. The excitation reference axis  10  is an axis through which the force F affects the load beam  110 , and determined by an arrangement among the spring section  110 , rigid section, and a Z height indicative of a position of the head  210 . The Z height is a height of the head  210  from a contact surface between the load beam  110  and the arm  220  to a disc surface  211 . An inertia force F 1  (mass “m s ” of the slider applied to the dimple  125  times “a”) near the top of the dimple  125  causes a bending moment M 1  (F 1 ·h 1  as a height from the excitation reference axis  10  to the tip of the dimple  125 ) on the top surface  11  at the upper side of the excitation reference axis  10 . An inertia force F 2  (mass “m” of the weight  150  times “a”) near the center of gravity of the weight  150  causes a bending moment M 2  (F 2 ·h 2  as a height from the excitation reference axis  10  to the weight  150 ) on the bottom surface  12  at the lower side of the excitation reference axis  10 . Without the weight  150 , M 2 =0 (N·m) and only the bending moment M 1  occurs on the balancer section  120 . The balancer section M 1  causes the torsion of the balancer section  120 .  
     [0053] A provision of the weight  150  would provide the balancer section  120  with the bending moment M 2  opposite to the bending moment M 1 . When the weight “m” of the weight  150  is set so that M 1 =M 2 , the torsion of the balancer section  120  may be made small. M 1 =M 2  may be satisfied by varying a shape of the weight  150  and setting a value of h 2 . The instant specification refers to balanced moments with respect to the excitation reference axis  10  as the weight balance. Referring to FIG. 7, it is understood that the increased weight “m” of the weight  150  would increase the bending moment M 2  opposite to the moment M 1  and decrease the gain. Here, FIG. 7 is a graph that indicates a swinging degree of the head  210  to the weight “m” of the weight  150  obtained using the finite element method analysis in the suspension  100  shown in FIG. 4. In FIG. 7, the abscissa axis is the weight “m” (mg) of the weight  150  while the ordinate axis is a gain “g” (dB). The gain is a value indicative of the swinging degree, which indicates that the larger the value is, the larger the swing is.  
     [0054] The gain is given by the following equation:  
             g   =     log                   (       n   2       n   1       )     ×   20                   (   dB   )               (   1   )                       
 
     [0055] When the equation (1) is applied to the instant embodiment, n 1  is a swing width applied to the suspension  100 A, and n 2  is a swing width of the head  210  corresponding to a swing of n 1 . As discussed, the weight balance of the balancer section  120  would decrease the gain and prevent the torsion.  
     [0056] The instant embodiment uses the weight  150  to realize the weight balance of the balancer section  120 , but the present invention is not limited to this embodiment. No weight  150  is needed if there is a weight balance of the balancer section  120 . For example, as shown in FIGS. 8 and 9, the balancer section  120   a  that is formed lower in the direction Z 2  than the body of the load beam  110  would provide the weight balance. Here, FIG. 8 is a schematic perspective view of the load beam  110   a  as a variation of the load beam  110  in the suspension  100 A shown in FIG. 4. FIG. 9 is a view for explaining weight balancing of the balancer section  120   a  when the load beam  110   a  shown in FIG. 8 is applied to the suspension  100 A. Referring to FIG. 9, the balancer section  120   a  secures the weight balance when a bending moment M 3  (F 3 ·h 3 ) that occurs at the side of the top surface  11   a  of the excitation reference axis  10   a  balances a balancing moment M 4  (F 4 ·h 4 ) that occurs at the side of the bottom surface  12   a.    
     [0057] As apparent from this structure, the weight balance of the balancer section  120  requires a balance between the upper and lower moments with respect to the excitation reference axis. The upper and lower moments with respect to the excitation reference axis may balance using the weight  150  as in the above structure, or the modified shape of the balancer part  120 . On the other hand, a position of the excitation reference axis  10  relatively changes when an arrangement among the spring section  114 , the rigid section  116  and the Z height changes. Therefore, a displacement of any one of the spring section  114 , the rigid section  116  and the Z height would realize the weight balance of the balancer section  120 , and this method also may prevent the torsion.  
     [0058] Referring now to FIG. 10, when the weigh  150  is spaced from the head  210  in the direction X 2 , the gain of the head  210  increases. FIG. 10 is a graph that indicates a swinging degree of the head  210  obtained using the finite element method analysis when the weight  150  of the suspension  100  shown in FIG. 4 moves in the direction X 2 . In FIG. 10, the abscissa axis is a position (mm) of the weight  150  in the direction X 2  while the ordinate axis is a gain “g” (dB). The abscissa axis is a position where the weight  150  and the head  210  have the same center of gravity, and a displacement of the abscissa axis corresponds to a moving distance of the weight  150  in the direction X 2 . Understandably, it is preferable that the weight  150  is located below the head  210  and its vicinity (e.g., 0 to 0.5 mm) via the balancer section  120 .  
     [0059] Referring now to FIGS.  11 - 13 , a description will be given of a suspension  100 B as a variation of the inventive suspension  100 . Here, FIG. 11 is a schematic perspective view of the suspension  100 B as a variation of the suspension  100  shown in FIG. 1. FIG. 12 is a schematic perspective view of the suspension  100 B shown in FIG. 11 when viewed from the rear side. FIG. 13 is a schematic perspective view of the hierarchical structure of the suspension  100 B shown in FIG. 11.  
     [0060] The suspension  100 B uses the preamp IC  160  instead of the weight  150  of the suspension  100 A. The preamp IC is a circuit to amplify an electronic signal. Similar to the weight  150 , the suspension  100 B uses the preamp IC  160  to maintain the weight balance of the balancer section  120 , and improve the electric characteristic to the head  210 . Other than that, the suspension  100 B is not different from the suspension  100 A with respect to operations and functions. Therefore, a description will be given of only differences from the suspension  100 A.  
     [0061] Referring now to FIG. 13, the preamp IC  160  and the head  210  are located opposite to each other with respect to the balancer section  120 . Similar to the weight  150 , the preamp IC  160  is located at a position enough for the weight balance. The electric wiring is arranged on the rear surface  113  of the load beam  110  to connect the head  210  through the preamp IC  160 . The suspension  100 B of the instant embodiment uses an FPC  170  for electric wiring. The FPC  170  extends in the direction X 1  on the rear surface  113  of the load beam  110 , and is folded back at the top of the load beam  110  to the side of the upper surface  111  and connected to the terminal connection section  133  of the head mounting section  132 . This structure may shorten a distance between the terminal connection section  133  connected to the head  210  and the preamp IC  160 , and effectively respond to a feeble signal from the head  210 .  
     [0062] Since the preamp IC  160  is located at a position corresponding to the above weight  150 , a preamp IC contact section  172  is formed in this position of the FPC  170 . The preamp IC contact section  172  is provided with a pair of terminals  173  electrically connected to the preamp IC  160 . The preamp IC  160  is electrically connected to the FPC  170  by attaching the preamp IC contact section  170  to the preamp IC  160 . This structure enables the preamp IC  160  to amplify an electric signal from the head  210  and works similar to the weight  150 .  
     [0063] Alternatively, as shown in FIG. 14, the electric wiring may be printed on the rear surface  113  of the load beam  110  to the preamp IC  160  as shown in FIG. 14, and the FPC  170   a  may be used for part from the preamp IC  160  to the head  210 , which requires folding back. Here, FIG. 14 is a schematic perspective view of a hierarchical structure of the suspension  100 B when the FPC  170  shown in FIG. 13 is replaced with the FPC  170   a  as a variation. This structure is advantageous in that the FPC  170   a  is less damaged in assembly using the short FPC  170   a.    
     [0064] Alternatively, as shown in FIG. 15, a through-hole  123  provided in the balancer section  120  may serve to fold back the electric wiring from the preamp IC  160  to the head  210 . Here, FIG. 15 is a schematic perspective view of the suspension  100 B provided with the through-hole  123 . This structure uses a short distance between the preamp IC  160  and the head  210 , effectively responds to a feeble signal from the head  210 , and advantageously improves the electric characteristics.  
     [0065] Referring to FIGS. 3 and 16, a description will be given of a disc unit  200 . Here, FIG. 16 is a view of the control section  250  in the disc unit  200  shown in FIG. 3. The disc unit  200  includes the suspension  100 , the head  210 , the arm  220 , the arm shaft  230 , the disc  240 , and the control section  250 . The disc unit  200  connects the arm  220  to the arm shaft  230  located near the disc  240 , and provides the suspension  100  at the top of the arm  220 . The head  210  is attached to the suspension  100 . A type of disc unit that floats the slider may use a contact start stop (“CSS”) manner in which the head lands when the disc stops and takes off when the disc starts rotating, and a ramp load manner in which the head retreats on a ramp located outside when the disc stops, but these manners do not limit the inventive disc unit  200 .  
     [0066] The suspension  100  may use any one of the above structures, and a detailed description will be omitted.  
     [0067] The head  210  is a magnetic head, and includes a disc facing surface  211  that faces the disc  240 , and a mounted surface  212  that faces the head mounting section  132 . This mounted surface  212  is located at the side of the flexure  130 , and arranged on the head mounting section  132  of the flexure  130 . The head  210  is located on the head mounting section  132  so that the center of gravity of the head  210  accords with the projection contact section  139  in the direction Z. This structure enables the center of gravity of the head  210  to be located on the dimple  125 , and the compression force by the load beam  110  is uniformly applied to the head  210 .  
     [0068] The head  210  includes a slider  214  and a head core (not shown). The slider generates a certain dynamic pressure due to the airflow along with a rotation of the disc  240 , serves to always maintain the certain flying height with warps and heave of the rotating disc. The head  210  includes a horceshoe magnetic circuit wound by a coil for signal recording and reproducing, and magnetizes the disc  240  with a magnetic flux generated by the coil. According to shapes of the head core, the head  210  is typically classified into three types including a monolithic (referred to as bulk technology) that includes a horceshoe head core and wire winding, a composite type, and a thin film type that uses thin film technology to form winding and a head core. The monolithic type makes the slider  214  and head core of ferrite as mixed oxide including manganese, zinc, and iron, while the composite type includes a composite of ferrite head core and ceramics slider. Of course, the present invention is not limited to these structures, and may use any shape for the head  210 . The head  210  may use any technology known in the art, and a detailed description thereof will be omitted in this specification.  
     [0069] The arm  220  supports the suspension  100  and connects it to the rotary shaft  230 . The arm  220  is an approximately sector plate. Of course, this shape is exemplary, and the arm  220  may use any shape. The arm  220  moves the magnetic head slider  230  to a target position on the disc  240  in cooperation with the arm shaft  230 . The arm  220  may be integrated with the arm shaft  230 , which will be described later.  
     [0070] The arm shaft  230  is located near the disc  240 , and connected to the arm  220 . The arm shaft  230  serves to enable the arm  220  and the head  210  located at the top thereof with seek on the disc  240 . The arm shaft  230  rotates the arm  220  using a drive unit  232  that includes, for example a coil and a permanent magnet for electromagnetic driving. This configuration is exemplary, and the drive unit for moving the arm  220  may use any structure. The arm shaft  230  may use a linear type that reciprocates the head in a direction parallel to the shaft of the suspension  100 , and a swing arm type that draws an arc. The inventive disc unit  100  is suitable for the swing arm type, but does not exclude the linear type. In seek action, the arm shaft  230  moves the head  210  to a target position under instructions by the control section  250 .  
     [0071] The disc  240  is connected rotatably to the motor  242 . The disc  240  is molded from aluminum alloy or glass plate, and evaporated magnetic materials on its surface. The disc unit  200  for use with a desktop personal computer (“PC”) would use the disc  240  with a diameter of a typically 3.5 inches. However, the disc  240  is not limited to this diameter, and may use 2.5 inches for laptop PCs or exceptional 5 inches. Although FIG. 3 shows only one disc  240 , plural discs may be stacked up. Thus, the inventive disc unit  200  does not exclude a disc unit that uses plural discs.  
     [0072] The disc  240  may record data when the head  210  magnetizes the magnetic materials. The disc  240  includes plural tracks that concentrically or spirally divide the disc surface, and plural sectors that divide the tracks in a radial direction. The disc  240  arranges as a minimum unit a cluster that includes plural sectors as one unit for efficient recording.  
     [0073] Referring to FIG. 16, the control section  250  includes, for example, a memory  252 , a control circuit  254 , and a signal processor  256 . Here, FIG. 16 is a view of the control section  250  in the disc unit shown in FIG. 3. The control circuit  254  controls operations of the head  210 , the drive unit  232 , the motor  242 , and the signal processor  256  under control of firmware stored in the memory  252 . The control section  250  reads data from the disc  240  via the head  210 , and sends it to the signal processor  256 . The signal processor  256  is connected to an interface of an external apparatus (not shown), such as a SCSI interface, demodulates data, picks up the original data, and sends it to the external apparatus. The signal processor  256  receives data to be recorded onto the disc, from the external apparatus, and writes the data onto the disc  240  through the head  210 .  
     [0074] In operation, the disc unit  200  uses the control circuit  254  in the control section  250  to drive the motor  242  and rotate the disc  240 . The disc unit  200  forms a fine air film between the head  210  and disc  240  using an airflow associated with a rotation of the disc  240 , and floats the head  210  from the disc  240  surface. The suspension  100  compresses the head  210  with a spring pressure of the suspension  100  in a direction opposite to the floating force of the head  210 . These two forces balance, and maintain a distance to be constant between the head  210  and the disc  240 . Then, the control section  250  controls the drive unit  232  for the arm shaft  230 , rotates the arm  220  and suspension  100 , and moves the head  210  to a target track on the disc  240 . Then, the head  210  reads data from the target track and send it to the signal processor  256  or writes data received from the signal processor  256 , into the target track.  
     [0075] Further, the present invention is not limited to these preferred embodiments, and a various variations and modifications may be made without departing from the spirit and scope of the present invention.  
     [0076] The inventive suspension absorbs the generated torsion at the balancer section that is more elastic than the rigid section, and the torsion does not propagate to the head in the balancer section. A structure that provide a weight approximately below the head with respect to the balancer section, and a structure that bends and spaces the balancer section from the disc may mechanically stabilize the weight balance of the balancer section, and effectively reduce the torsion. Moreover, use of the preamp IC for the weight would be able to improve the electric characteristics.