Abstract:
The present invention relates to a magnetic head actuator and a magnetic disk device in which a magnetic head is moved to a predetermined position by actuating an arm on a revolving magnetic disk. A magnetic head actuator comprises an arm in which a suspension for supporting a magnetic head is provided, the arm being actuated to move the magnetic head. A damper material is provided on at least one side of the arm, the damper material comprising a restriction material and a viscoelastic material, the restriction material suppressing vibrations of the arm, and the viscoelastic material absorbing vibrations of the arm.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a U.S. continuation application which is filed under 35 USC 111(a) and claims the benefit under 35 USC 120 and 365(c) of International Application No. PCT/JP2002/011320, filed on Oct. 30, 2002, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention generally relates to a magnetic head actuator and a magnetic disk device, and more particularly to an actuator for a magnetic head and a magnetic disk device having the actuator in which the magnetic head is moved to a predetermined position by driving the arm on the revolving magnetic disk.  
         [0004]     For example, in the magnetic disk device, such as a hard disk drive (HDD), the head slider of the magnetic head is lifted over the surface of the revolving magnetic disk and the magnetic-head element performs reading information from or writing information to the magnetic disk in the lifted state of the head slider. In recent years, in order to increase the recording density of the magnetic disk, reducing the lifting height of the head slider and making the magnetic-head element small have been proposed. In order to accurately position the magnetic-head element to the predetermined track of the magnetic disk whose recording density is thus increased, it is necessary to reduce the vibrations of the arm which is moved over the magnetic disk surface.  
         [0005]     2. Description of the Related Art  
         [0006]      FIG. 1  shows an example of the conventional magnetic disk device  1 . The state of the conventional magnetic disk device  1  in which the top cover is removed is illustrated in  FIG. 1 .  
         [0007]     The magnetic disk device  1  generally comprises the housing  2 , the magnetic disk  3 , the actuator  4  for the magnetic head (called the head actuator  4 ), and the voice-coil motor  5 .  
         [0008]     The housing  2  is provided with the cover which is not illustrated, thereby preventing the inclusion of dirt in the magnetic disk device from the exterior and protecting the respective above-mentioned components  3  and  4  and  5  from damage. Moreover, the magnetic disk  3  is rotated at high speed with a predetermined rotation speed by the spindle motor which is not shown in  FIG. 1 .  
         [0009]     As shown in  FIG. 2  and  FIG. 3 , the head actuator  4  comprises the E-block  14  in which the plurality of actuator arms  6  (in this example, the five actuator arms) are provided. Moreover, the shaft hole  12  in which the shaft  8  embedded in the housing  2  is inserted is formed approximately in the center of the E-block  14 . Furthermore, the coil  13  which constitutes part of the voice-coil motor  5  is arranged in the position which is opposite to the position where the actuator arm  6  is arranged with respect to the position of the shaft hole  12 .  
         [0010]     Each of the actuator arms  6  is a plate-like member which is made of aluminum. The actuator arms  6  are provided on the E-block  14  as mentioned above. The suspension attachment part  11  is provided at the leading edge of each of the actuator arms  6 , and the suspension  7  on which the magnetic head is carried is attached to the suspension attachment part  11 . Usually, the suspension  7  (which is not shown in  FIG. 2  and  FIG. 3 ) is fixed to the suspension attachment part  11  by crimping.  
         [0011]     The voice-coil motor  5  comprises the coil  13  which is provided in the head actuator  4 , the magnet which generates the magnetic force, and the yoke  5   a  which is provided for applying the magnetic force to the coil  13 , etc.  
         [0012]     The magnet is constituted so that the magnetic force generated by the magnet may penetrate the coil  13 . By varying the current supplied to the coil  13 , the force to cause the head actuator  4  to be rotated around the rotation axis of the shaft  8  is generated. Thereby, the head actuator  4  is rotated around the shaft  8  to move the magnetic head, attached to the leading edge of the actuator arm  6  through the suspension  7 , to the predetermined position on the magnetic disk  3 .  
         [0013]     A description will be given of the actuator arm  6 . In order to attain weight reduction of the actuator arm  6 , the slot  15  is formed in the actuator arm  6  as the through hole which penetrates the actuator arm  6  in the direction perpendicular to the paper of the figure. Thus, the moment of inertia of the actuator arm  6  can be reduced by forming the slot  15  in the actuator arm  6 . For this reason, it is possible to attain high-speed accessing of the head actuator  4  with the slot  15  for weight reduction being formed.  
         [0014]     By the way, the actuator arm  6  in which the slot  15  is formed has various oscillation modes in the range from several kHz to several 10 kHz.  FIG. 4  is a diagram for explaining the oscillation characteristic of the head actuator in the conventional magnetic disk device of  FIG. 1 .  
         [0015]     As shown in  FIG. 4 , the damping of the actuator arm  6  to the oscillation modes is very low because the actuator arm is formed by the integral structure of a metallic member. The damping coefficient ξ is on the order of 0.01. In other words, the resonance scale factor at the time of resonance will become about 50 times. This means that a great peak of the resonance occurs at the time of resonance, and the positioning accuracy of the head actuator will deteriorate.  
         [0016]     On the other hand, the recording density of the magnetic disk is doubled every year as mentioned above, and the track density (TPI) is increased at an annual rate of 50% or more. Therefore, in order to increase the track density, it is necessary to raise the positioning accuracy.  
         [0017]     In the latest magnetic disk device, the track pitch of 0.4 micrometers is attained, and the permissible NRRO (the oscillation accuracy) amounts to 50 nm.  
         [0018]     Especially, in the case of the high-speed rotation disk (10,000 rpm, 15,000 rpm), when the air flow generated inside when the magnetic disk  3  is rotated at high speed collides with the actuator arm  6 , the aerodynamic vibrations of the actuator arm  6  occur. The state in which the actuator arm  6  is oscillated by the natural vibration during the aerodynamic vibration is shown at the positions (about 7.6 kHz, 12.0 kHz) indicated by the arrows A and B in  FIG. 4 .  
         [0019]     Although the high-speed accessing of the head actuator  4  is intended by forming the slot  15 , if aerodynamic vibrations occur on the actuator arm  6  and there is the excitation by the natural vibration of the actuator arm  6 , then the positioning accuracy will fall by the vibrations of the actuator arm  6 . For this reason, it is very difficult to accurately position the magnetic head at the predetermined position.  
       SUMMARY OF THE INVENTION  
       [0020]     An object of the present invention is to provide an improved magnetic head actuator and magnetic disk device in which the above-described problems are eliminated.  
         [0021]     Another object of the present invention is to provide a magnetic head actuator which effectively reduces the influences of the aerodynamic vibrations on the arm.  
         [0022]     Another object of the present invention is to provide a magnetic disk device which effectively reduces the influences of the aerodynamic vibrations on the arm.  
         [0023]     The above-mentioned objects of the present invention are achieved by a magnetic head actuator comprising: an arm in which a suspension for supporting a magnetic head is provided, the arm being actuated to move the magnetic head; and a damper material provided on at least one side of the arm, the damper material increasing a rigidity of the arm and absorbing vibrations of the arm.  
         [0024]     According to the present invention, the damper material serves to increase the rigidity of the arm and absorb the vibrations of the arm, even though the aerodynamic oscillation force is applied to the arm by the air flow generated with the rotation of the magnetic disk. For this reason, it is possible to prevent unnecessary vibrations from occurring on the arm, and it is possible to position the magnetic head by the magnetic head actuator with a high level of accuracy.  
         [0025]     Moreover, the above-mentioned objects of the present invention are achieved by a magnetic head actuator comprising: an arm in which a suspension for supporting a magnetic head is provided, the arm being actuated to move the magnetic head; and a damper material provided on at least one side of the arm, the damper material comprising a restriction material and a viscoelastic material, the restriction material suppressing vibrations of the arm, and the viscoelastic material absorbing vibrations of the arm.  
         [0026]     According to the present invention, the restriction material of the damper material serves to suppress the vibrations of the arm and the viscoelastic material of the damper material serves to absorb the vibrations of the arm, even though the aerodynamic oscillation force is applied to the arm by the air flow generated with the rotation of the magnetic disk. For this reason, it is possible to prevent unnecessary vibrations from occurring on the arm, and it is possible to position the magnetic head by the magnetic head actuator with a high level of accuracy.  
         [0027]     Moreover, the magnetic head actuator of the above-mentioned invention may be configured so that the damper material is arranged on both sides of the arm symmetrically.  
         [0028]     Since the damper material is symmetrically arranged on both sides of the arm, the balance of the arm becomes appropriate and it is possible to suppress more effectively the unnecessary vibration from occurring on the arm.  
         [0029]     Moreover, the magnetic head actuator of the above-mentioned invention may be configured so that the arm is formed with a weight-reduction part, and the damper material is arranged on the arm at a position including a position of the arm where the weight-reduction part is formed.  
         [0030]     Since the weight of the arm is reduced and the moment of inertia is also reduced by providing the weight reduction part in the arm, shortening of the seek time can be aimed at by the magnetic head actuator. Moreover, unnecessary vibration occurring in the weight reduction part can be suppressed by arranging the damper material in the position including the formation position of the weight reduction part of the arm.  
         [0031]     That is, in the case of the conventional device in which the weight reduction part is exposed, the air flow enters the weight reduction part, and the arm is subjected to the unnecessary vibrations due to the air flow. However, according to the present invention, the weight reduction part is enclosed by the damper material by arranging the damper material at the position including the formation position of the weight reduction part of the arm. For this reason, the unnecessary vibrations due to the air flow entering the weight reduction part can be suppressed, and it is therefore possible to position the magnetic head by the magnetic head actuator with a high level of accuracy.  
         [0032]     Moreover, the magnetic head actuator of the above-mentioned invention may be configured so that the damper material is arranged on the arm partially.  
         [0033]     According to the above-mentioned composition, it is possible to adjust the vibration-proof effect with the arrangement position and the area of the damper material.  
         [0034]     Moreover, the magnetic head actuator of the above-mentioned invention may be configured so that the damper material is made of a material having a rigidity higher than a rigidity of aluminum. Or the magnetic head actuator of the above-mentioned invention may be configured so that the damper material is made of a stainless steel.  
         [0035]     According to the above-mentioned composition, the damper material has the high rigidity, and it is possible to prevent certainly the vibrations of the arm due to the air flow.  
         [0036]     Moreover, the magnetic head actuator of the above-mentioned invention may be configured so that the arm is formed with a weight reduction part, the damper material is arranged on the arm at a position including a position of the arm where the weight reduction part is formed, and a part of the viscoelastic material located at a position of the damper material opposing the position of the weight reduction part is removed.  
         [0037]     According to the above-mentioned composition, it is possible to prevent the dirt entering the weight reduction part at the time of the assembly from sticking to the viscoelastic material, and therefore the reliability of the magnetic disk device in which the magnetic head actuator is provided can be raised.  
         [0038]     Moreover, the magnetic head actuator of the above-mentioned invention may be configured so that the arm is formed with a weight reduction part, the damper material is arranged on the arm at a position including a position of the arm where the weight reduction part is formed, and an opening is formed at a position of the damper material opposing the position of the weight reduction part.  
         [0039]     According to the above-mentioned composition, the moment of inertia of the arm including the damper material can be reduced while the absorption of the vibrations is aimed at and the rigidity of the arm is raised. Thereby, it is possible to attain the high-speed seek processing and the highly accurate positioning processing of the magnetic head compatibly with the moving processing of the magnetic head.  
         [0040]     Moreover, the magnetic head actuator of the above-mentioned invention may be configured so that a tail part of the suspension is attached to the arm using the viscoelastic material.  
         [0041]     According to the above-mentioned composition, the tail part of the suspension is attached to the arm using the viscoelastic material, and it is no longer necessary to provide the additional composition for fixing the tail part to the actuator arm as in the conventional head actuator, and the composition of the head actuator can be simplified.  
         [0042]     Moreover, the above-mentioned objects of the present invention are achieved by a magnetic disk device including a magnetic disk provided as a recording medium, a rotation unit rotating the magnetic disk, and a magnetic head actuator, the magnetic head actuator comprising: an arm in which a suspension for supporting a magnetic head is provided, the arm being actuated to move the magnetic head; and a damper material provided on at least one side of the arm, the damper material increasing a rigidity of the arm and absorbing vibrations of the arm.  
         [0043]     According to the present invention, the damper material serves to increase the rigidity of the arm and absorb the vibrations of the arm, even though the aerodynamic oscillation force is applied to the arm by the air flow generated with the rotation of the magnetic disk. For this reason, it is possible to prevent unnecessary vibrations from occurring on the arm, it is possible to position the magnetic head by the magnetic head actuator with a high level of accuracy, and the reliability of the magnetic disk device can be raised.  
         [0044]     Moreover, the above-mentioned objects of the present invention are achieved by a magnetic disk device including a magnetic disk provided as a recording medium, a rotation unit rotating the magnetic disk, and a magnetic head actuator, the magnetic head actuator comprising: an arm in which a suspension for supporting a magnetic head is provided, the arm being actuated to move the magnetic head; and a damper material provided on at least one side of the arm, the damper material comprising a restriction material and a viscoelastic material, the restriction material suppressing vibrations of the arm, and the viscoelastic material absorbing vibrations of the arm.  
         [0045]     According to the present invention, the restriction material of the damper material serves to suppress the vibrations of the arm and the viscoelastic material of the damper material serves to absorb the vibrations of the arm, even though the aerodynamic oscillation force is applied to the arm by the air flow generated with the rotation of the magnetic disk. For this reason, it is possible to prevent unnecessary vibrations from occurring on the arm, it is possible to position the magnetic head by the magnetic head actuator with a high level of accuracy, and the reliability of the magnetic disk device can be raised. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0046]     Other objects, features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.  
         [0047]      FIG. 1  is a perspective view of an example of the conventional magnetic disk device in which the head actuator is provided.  
         [0048]      FIG. 2  is an enlarged plan view of the head actuator in the conventional magnetic disk device of  FIG. 1 .  
         [0049]      FIG. 3  is an enlarged front view of the head actuator in the conventional magnetic disk device of  FIG. 1 .  
         [0050]      FIG. 4  is a diagram for explaining the oscillation characteristic of the head actuator in the conventional magnetic disk device of  FIG. 1 .  
         [0051]      FIG. 5  is a perspective view of the magnetic disk device in which the head actuator in the first preferred embodiment of the invention is provided.  
         [0052]      FIG. 6  is an enlarged plan view of the head actuator in the first preferred embodiment of the invention.  
         [0053]      FIG. 7  is an enlarged front view of the head actuator in the first preferred embodiment of the invention.  
         [0054]      FIG. 8  is a cross-sectional view of the head actuator which is taken along the X 1 -X 1  line in  FIG. 6 .  
         [0055]      FIG. 9  is a diagram for explaining the oscillation characteristic of the head actuator in the first preferred embodiment of the invention.  
         [0056]      FIG. 10  is a plan view of the head actuator in the second preferred embodiment of the invention.  
         [0057]      FIG. 11  is a front view of the head actuator in the second preferred embodiment of the invention.  
         [0058]      FIG. 12  is a cross-sectional view of the head actuator in the third preferred embodiment of the invention in the vicinity of the slot for weight reduction of the head actuator.  
         [0059]      FIG. 13  is a front view of the head actuator in the fourth preferred embodiment of the invention.  
         [0060]      FIG. 14  is a cross-sectional view of the head actuator in the fourth preferred embodiment of the invention.  
         [0061]      FIG. 15  is a plan view of the head actuator in the fifth preferred embodiment of the invention.  
         [0062]      FIG. 16  is a front view of the head actuator in the fifth preferred embodiment of the invention.  
         [0063]      FIG. 17  is an enlarged plan view of the head actuator in the fifth preferred embodiment of the invention in the vicinity of the slot for weight reduction of the head actuator.  
         [0064]      FIG. 18  is a plan view of the head actuator in the sixth preferred embodiment of the invention.  
         [0065]      FIG. 19  is a cross-sectional view of the heat actuator which is taken along the X 2 -X 2  line in  FIG. 18 .  
         [0066]      FIG. 20  is a cross-sectional view of the fixed structure of the tail part of a conventional head actuator.  
         [0067]      FIG. 21  is an enlarged plan view of the head actuator in the seventh preferred embodiment of the invention in the vicinity of the slot for weight reduction of the head actuator. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0068]     A description will now be given of the preferred embodiments of the invention with reference to the accompanying drawings.  
         [0069]      FIG. 5  shows the composition of the magnetic disk device  20  in which the head actuator  30 A in the first preferred embodiment of the invention is provided. In addition, the state of the magnetic disk device  20  in which the top cover is removed is illustrated.  
         [0070]     The magnetic disk device  20  generally comprises the housing  22 , the magnetic disk  23 , the actuator  30 A for the magnetic head (called the head actuator  30 A), and the voice-coil motor  25 .  
         [0071]     The housing  22  is provided with the cover which is not illustrated, thereby preventing the inclusion of dirt in the magnetic device from the exterior and protecting the respective above-mentioned components  23 ,  25  and  30 A from damage. Moreover, the magnetic disk  23  is rotated at high speed at a predetermined rotation speed (for example, 10,000 rpm, 15,000 rpm) by the spindle motor which is not shown in  FIG. 5 .  
         [0072]     As shown in  FIG. 6  and  FIG. 7 , the head actuator  30 A comprises the E-block  34  in which the plurality of the actuator arms  26  (in this example, the five actuator arms) are provided. Moreover, the shaft hole  32  in which the shaft  28  embedded in the housing  22  is inserted is formed approximately in the center of the E-block  34 . Furthermore, the coil  33  which constitutes part of the voice-coil motor  25  is arranged in the position which is opposite to the position where the actuator arm  26  is arranged with respect to the position of the shaft hole  32 .  
         [0073]     Each of the actuator arms  26  is a plate-like member which is made of aluminum. The actuator arms  26  are provided on the E-block  34 . The suspension attachment part  31  is provided at the leading edge of each of the actuator arms  26 , and the suspension  27  on which the magnetic head is carried is attached to the suspension attachment part  31 . Usually, the suspension  27  (which is not shown to  FIG. 6  or  FIG. 7 ) is fixed to the suspension attachment part  31  by crimping.  
         [0074]     Moreover, in order to attain weight reduction of the actuator arm  26 , the slot  35  is formed in the actuator arm  26 . In addition, the weight reduction means either making the actuator arm  26  thin in the thickness direction of the actuator arm  26  (which is the up/down direction in  FIG. 7 ), or forming the through hole, penetrating the actuator arm  26  in the up/down direction, in the actuator arm  26  (in this embodiment, the slot  35  penetrating the actuator arm in the up/down direction is given as the example for the weight reduction).  
         [0075]     Thus, the moment of inertia of the actuator arm  26  can be reduced by forming the slot  35  for the weight reduction. For this reason, it is possible to attain high-speed accessing of the head actuator  30 A by forming the slot  35  for the weight reduction.  
         [0076]     However, the actuator arm  26  is formed with the slot  35  which is constituted by the recess or the opening, the actuator arm  26  is easily influenced by the air flow generated at the time of the high-speed rotation of the magnetic disk  23 . That is, the aerodynamic vibrations of the actuator arm  26  are likely to arise.  
         [0077]     The voice-coil motor  25  comprises the coil  33  which is provided in the head actuator  30 A, the magnet (not shown in the figure) which generates the magnetic force, and the yoke  25   a  which is provided for applying the magnetic force to the coil  33 .  
         [0078]     The magnet is constituted so that the magnetic force generated by the magnet may penetrate the coil  33 . By varying the current supplied to the coil  33 , the force to rotate the head actuator  30 A around the shaft  28  is generated. Thereby, the head actuator  30 A is rotated around the rotation axis of the shaft  28  to move the magnetic head, attached to the leading edge of the actuator arm  26  through the suspension  27 , to the predetermined position on the magnetic disk  23 .  
         [0079]     Next, a description will be given of the damper material  40 A. The damper material  40 A in this embodiment (indicated by the dotted area in  FIG. 5  and  FIG. 6 ) is arranged on the actuator arm  26  in the comparatively wide area from the position where the suspension attachment part  31  is formed to the vicinity of the position where the shaft hole  32  is formed. Therefore, the damper material  40 A is formed so as to include the position where the slot  35  is formed. Thereby, the damper material  40 A is provided on the actuator arm  26  so that the damper material  40 A closes the slot  35 . Furthermore, the damper material  40 A in this embodiment is arranged only on one side of the actuator arm  26  as shown in  FIG. 7 .  
         [0080]      FIG. 8  is a cross-section view of the head actuator  30 A which is taken along the X 1 -X 1  line in  FIG. 6 .  
         [0081]     As shown in  FIG. 8 , the damper material  40 A is provided as the laminated structure which includes the restriction material  41  and the viscoelastic material  42 .  
         [0082]     The restriction material  41  is made of a material having a rigidity higher than a rigidity of the aluminum which is the material making the actuator arm  26 . Specifically, the restriction material  41  in this embodiment is made of a stainless steel board with a thickness of about 50 micrometers (in addition, the thickness of the actuator arm  26  is about 0.9 mm).  
         [0083]     Moreover, the viscoelastic material  42  is made of, for example, a double-sided adhesive tape (for example, the trade name: VEM) with a thickness of about 50 micrometers. Specifically, the double-sided adhesive tape is formed with the adhesive applied to both sides of a resin base tape. Therefore, the restriction material  41  is fixed to the actuator arm  26  by the viscoelastic material  42 .  
         [0084]     Moreover, since the resin base tape of the viscoelastic material  42  serves as the base material, the viscoelastic material  42  functions as a damper which absorbs vibrations with the elasticity of the resin base tape.  
         [0085]     Thus, the damper material  40 A in the present embodiment has the compound structure including the restriction material  41  with the high rigidity and the viscoelastic material  42  with the vibration absorbing function, and this damper material  40 A is provided on the actuator arm  26 . Even if the aerodynamic oscillation force is applied to the actuator arm  26  by the air flow generated with the high-speed rotation of the magnetic disk  23 , the rigidity of the actuator arm  26  is raised by the damper material  40 A and the vibrations of the actuator arm  26  can be absorbed.  
         [0086]     Specifically, the vibrations of the actuator arm  26  generated by the aerodynamic vibration force can be suppressed by the restriction material  41  of the damper material  40 A, and the still remaining vibrations of the actuator arm  26  can be absorbed by the viscoelastic material  42  of the damper material  40 A. For this reason, it is possible to prevent unnecessary vibrations from occurring on the actuator arm  26 , and it is therefore possible to position the magnetic head by the head actuator  30 A with a high level of accuracy. Moreover, the reliability of the magnetic disk device  20  can be raised by using the head actuator  30 A.  
         [0087]     In the above-described embodiment, the damper material  40 A is arranged so that the position of the damper material  40 A includes the position where the slot  35  is formed. By this arrangement, it is possible to suppress the occurrence of unnecessary vibrations due to the slot  35  formed in the actuator arm  30 A. Namely, in the case of the conventional magnetic disk device shown in  FIG. 1  to  FIG. 3 , the slot  15  for the weight reduction is exposed, when the air flow enters the slot  15 , the actuator arm  6  is oscillated and unnecessary vibrations of the actuator arm  6  occur.  
         [0088]     However, in the present embodiment, the damper material  40 A is arranged in the position including the position of the actuator arm  26  where the slot  35  for the weight reduction is formed, so that the slot  35  is enclosed by the damper material  40 A. For this reason, it is possible for the present embodiment to prevent unnecessary vibrations from occurring on the actuator arm  26  due to the air flow entering the slot  35 .  
         [0089]      FIG. 9  shows the oscillation characteristic (NRRO spectrum) of the actuator arm  26  in the present embodiment in which the damper material  40 A is provided. In addition,  FIG. 9  shows also the oscillation characteristic (NRRO spectrum) of the conventional actuator arm  6  shown in  FIG. 4 , for the purpose of comparison.  
         [0090]     In the oscillation characteristic of  FIG. 9 , the frequencies at which the actuator arm  26  is oscillated by the natural vibration during the aerodynamic vibration are about 7.6 kHz and about 12.0 kHz, which are indicated by the arrows A and B in  FIG. 9 .  
         [0091]     At the frequency of about 7.6 kHz, the peak of the vibration occurs in the conventional actuator arm  6  as indicated by the letter a 2  in  FIG. 9  while no peak of the vibration occurs in the present embodiment using the damper material  40 A as indicated by the letter a 1  in  FIG. 9 .  
         [0092]     Moreover, at the frequency of about 12.0 kHz, the peak of the vibration occurs in the conventional actuator arm  6  as indicated by the letter b 2  in  FIG. 9  while no peak of the vibration occurs in the present embodiment using the damper material  40 A as indicated by the letter b 1  in  FIG. 9 .  
         [0093]     As is apparent from  FIG. 9 , since the damper material  40 A is arranged on the actuator arm  26 , it is possible to suppress the vibrations of the actuator arm  26  resulting from the aerodynamic vibrations.  
         [0094]     In addition, in the above-described embodiment, the damper material  40 A is arranged on all the plurality of the actuator arms  26 . However, it is not necessarily required to arrange the damper material  40 A on all the actuator arms  26 . Alternatively, the damper material  40 A may be arranged only on the actuator arm  26  which is likely to receive the influences of the aerodynamic vibrations.  
         [0095]     Next, a description will be given of the second preferred embodiment of the invention.  FIG. 10  and  FIG. 11  show the head actuator  30 C in the second preferred embodiment.  
         [0096]     In the previous embodiment, the damper material  40 A is arranged approximately in the whole region of the actuator arm  26 . On the other hand, in the present embodiment, the damper material  40 B is arranged on the actuator arm  26  partially as shown in  FIG. 10 .  
         [0097]     Specifically, in this embodiment, as shown in  FIG. 11 , the damper material  40 B arranged on the actuator arm  26  located in the topmost part and the actuator arm  26  located in the lowermost part is made to have the area smaller than that of the damper material  40 A arranged on the other actuator arms  26 . In the actuator arm  26  in which the damper material  40 B is arranged, only approximately half of the actuator arm  26  is covered by the damper material  40 B as shown in  FIG. 10 .  
         [0098]     It is not necessarily required that the damper material be arranged on all over the actuator arm  26 , and, as in the present embodiment, it is also appropriate that the damper material be arranged on the actuator arm  26  partially.  
         [0099]     By arranging the damper material  40 B on the actuator arm  26  partially, it is possible to adjust the vibration-proof effect of the magnetic disk device in accordance with the position and the area of the damper material  40 B being arranged.  
         [0100]     Next, a description will be given of the third preferred embodiment of the invention.  FIG. 12  shows the head actuator  30 D in the third preferred embodiment.  
         [0101]     In the previous embodiment, the viscoelastic material  42  which constitutes the damper material  40 A or  40 B is provided also at the position opposing the position of the slot  35  as shown in  FIG. 8 .  
         [0102]     On the other hand, the present embodiment is characterized in that part of the viscoelastic material  42  located at the position opposing the position of the damper material  40 C where the slot  35  for the weight reduction is enclosed is removed, and the removal part  37  is formed. According to this composition, it is possible to prevent the dirt entering in the slot  35  from sticking to the viscoelastic material  42  at the time of the assembly, and therefore the reliability of the magnetic disk device in which the head actuator  30 D is provided can be raised.  
         [0103]     Namely, it is likely that dirt enters the slot  35  for the weight reduction, which is constituted by the recess or the opening. In the case where the viscoelastic material  42  (equivalent to the adhesive) is formed in the slot  35  at the position opposing the position of the slot  35 , the dirt entering into the slot  35  will stick to the viscoelastic material  42 .  
         [0104]     And if the head actuator is assembled to the magnetic disk device in this state, the dirt will separate from the viscoelastic material  42  later after the assembly and will float within the magnetic disk device. If the dirt separated from viscoelastic material is included between the magnetic disk  23  and the magnetic head, the recording/reproducing characteristics of the magnetic disk device will deteriorate greatly, and the reliability of the magnetic disk device falls.  
         [0105]     However, according to the present embodiment, the part of the viscoelastic material  42  located at the position opposing the position of the slot  35  is removed, and the removal part  37  is formed, thereby preventing the dirt from sticking to the viscoelastic material  42 .  
         [0106]     For this reason, even after the head actuator  30 D is assembled to the magnetic disk device, the inside of the magnetic disk device can be maintained in the clean state, and therefore the reliability of the magnetic disk device can be raised.  
         [0107]     Next, a description will be given of the fourth preferred embodiment of the invention.  FIG. 13  and  FIG. 14  show the head actuator  30 E in the fourth preferred embodiment.  
         [0108]     In the present embodiment, the above-described damper material  40 A is arranged on both sides of the actuator arm  26  symmetrically. Specifically, the damper materials  40 A of the same form are arranged on the top surface and the bottom surface of each of the actuator arms  26  in the same conditions.  
         [0109]     According to the composition of this embodiment in which the damper material  40 A is arranged on both sides of the actuator arm  26  symmetrically, the balance of the actuator arm  26  becomes appropriate to withstand vibrations, and it is possible to suppress more effectively unnecessary vibrations from occurring on the actuator arm  26 .  
         [0110]     Next, a description will be given of the fifth preferred embodiment of the invention.  FIG. 15  and  FIG. 16  show the head actuator  30 F in the fifth preferred embodiment.  
         [0111]     In the previous embodiment, the damper material  40 A- 40 C is arranged on either the top surface or the bottom surface of the actuator arm  26 . On the other hand, the present embodiment is characterized in that the damper material  40 D is arranged on the side surface  26   a  of the actuator arm  26 .  
         [0112]     This damper material  40 D is of the same composition as the above-mentioned damper material  40 A- 40 C, and, as shown in  FIG. 17 , the damper material  40 D comprises the restriction material  41  and the viscoelastic material  42 .  
         [0113]     The aerodynamic oscillation force, which is applied to the actuator arm  26  when the magnetic disk  23  is rotated, is exerted not only in the directions indicated by the arrows Z 1  and Z 2  in  FIG. 16  but also in the surface directions of the actuator arm  26  indicated by the arrows Y 1  and Y 2  in  FIG. 15 . In order to suppress the aerodynamic oscillation force applied in the directions indicated by the arrows Z 1  and Z 2  in  FIG. 16 , it is effective to arrange the damper material  40 A- 40 C on the top surface and the bottom surface of the actuator arm  26  as in the previous embodiment. However, according to the composition of the previous embodiment, the aerodynamic oscillation force applied in the directions indicated by the arrows Y 1  and Y 2  in  FIG. 15  cannot be adequately suppressed.  
         [0114]     For this reason, the damper material  40 D in this embodiment is arranged on the side surface  26   a  of the actuator arm  26 . According to this embodiment, it is possible to prevent the vibrations from occurring on the actuator arm  26  due to the aerodynamic oscillation force applied in the directions indicated by the arrows Y 1  and Y 2  in  FIG. 15 , and it is possible to suppress the unnecessary vibrations from occurring in the surface directions of the actuator arm  26 .  
         [0115]     In addition, in the present embodiment, the composition in which the damper material  40 D is arranged only on the side surface  26   a  of the actuator arm  26 . It is a matter of course that the composition in which the damper material  40 A- 40 C is additionally arranged on the top surface and the bottom surface of the actuator arm  26  is also appropriate.  
         [0116]     Next, a description will be given of the sixth preferred embodiment of the invention.  FIG. 18  and  FIG. 19  show the head actuator  30 G in the sixth preferred embodiment.  
         [0117]     As shown in  FIG. 18 , the suspension  27  in which the magnetic head  38  is provided is fixed to the leading edge of the actuator arm  26 .  
         [0118]     This magnetic head  38  is arranged so that the flexible wiring (called the wiring FPC) from the magnetic head  38  is extended to the side part of the E-block  34  through the suspension  27  and the actuator arm  26 . The wiring FPC is bonded to the suspension  27  by the adhesive so that the integral structure of the wiring FPC and the suspension  27  is formed.  
         [0119]     Hereinafter, the portion of the wiring FPC which extends from the suspension  27  (which portion is arranged on the actuator arm  26 ) is called the tail part  39  of the suspension  27 .  
         [0120]     In the case of the conventional head actuator, the groove  9  is formed in the side part of the actuator arm  6 , and the tail part  39  of the suspension  7  is fitted in the groove  9  as shown in  FIG. 20 , so that the wiring between the suspension  7  and the E-block is arranged.  
         [0121]     However, according to the composition of the conventional head actuator, the tail part  39  (the flexible wiring) is affected by the aerodynamic vibrations, and as a result the vibrations of the actuator arm  6  occur.  
         [0122]     To obviate the problem, according to the present embodiment, the damper material  40 E is arranged so that it extends sidewise from the actuator arm  26 , the extended part  45  is formed, and the tail part  39  of the suspension  27  arranged in the extended part  45  as shown in  FIG. 19 . Namely, the damper material  40 E is formed with the extended part  45  which extends sidewise from the actuator arm  26 , and the viscoelastic material  42  is exposed to the bottom surface of the extended part  45 .  
         [0123]     The present embodiment is characterized in that the tail part  39  of the suspension  27  is bonded to the exposed viscoelastic material  42 . Thereby, the tail part  39  is attached to the actuator arm  26  by using the viscoelastic material  42 .  
         [0124]     According to the composition of the present embodiment, it is no longer necessary to provide the additional composition (the groove  9 ) for fixing the tail part  39  to the actuator arm  26  as in the conventional head actuator, and the composition of the head actuator  30 G can be simplified.  
         [0125]     Moreover, the tail part  39  is fixed to the damper material  40 E provided with the restriction material  41  having the high rigidity, and it is possible to prevent the unnecessary vibrations from occurring on the actuator arm  26  due to the tail part  39  even if the aerodynamic oscillation force is exerted.  
         [0126]     Next, a description will be given of the seventh preferred embodiment of the invention.  FIG. 21  shows the head actuator  30 H in the seventh preferred embodiment.  
         [0127]     In the present embodiment, the opening  46  is formed in the damper material  40 F at the position opposing the position of the slot  35  for the weight reduction. Therefore, neither the restriction material  41  nor the viscoelastic material  42  exists at the position of the damper material  40 F opposing the position where the slot  35  for the weight reduction is formed.  
         [0128]     When the aerodynamic oscillation force exerted to the actuator arm  26  by the air flow which passes the slot  35  for the weight reduction is small according to the rotation speed of the magnetic disk  23 , the damper material  40 F is formed with the opening  46 , and the moment of inertia of the actuator arm  26  including the damper material  40 F can be reduced.  
         [0129]     Moreover, the parts of the actuator arm  26  other than the position where the slot  35  is formed have the high rigidity raised by the damper material  40 F, and it is possible to suppress the vibrations from occurring on the actuator arm  30 H. This makes it possible to attain the high-speed seek processing and the highly accurate positioning processing of the magnetic head compatibly with the moving processing of the magnetic head.  
         [0130]     The present invention is not limited to the above-described embodiments, and variations and modifications may be made without departing from the scope of the present invention.