Abstract:
The present invention is aimed to provide a head suspension having a high resonant frequency, high shock resistance and low rigidity, which greatly contributes to an improvement of a magnetic disk apparatus. In an oscillation-type actuator, at least a part of a spring arm of the head suspension having a data reading/writing head slider  1  is made of an anisotropic layer whose rigidity varies in accordance with a direction. In this case, the anisotropic layer is laminated so that the high rigidity modulus orientation direction is different according to layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims priority, and incorporate by reference the entire disclosure of Japanese Patent Application No. 2002-38041, filed on Feb. 15, 2002.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a head suspension, and particularly to a structure of a head suspension for supporting a magnetic head to read/write data from and on a magnetic disk in an oscillation-type actuator which is used in a magnetic disk apparatus. The magnetic disk apparatus us used as an external storage device for a computer.  
           [0004]    2. Description of the Prior Art  
           [0005]    Recently, track pitches have been made smaller to increase the storage capacity in a magnetic disk apparatus, and accordingly, the frequency band to control the position of a magnetic head which moves on tracks has become higher. In control using such a high frequency band, it is necessary for the frequency of the mechanical resonance point of the suspension to be high so as not to make the controlling frequency of the head suspension operate the head at the mechanical resonance frequency of the suspension. Namely, a high resonant frequency head suspension is required.  
           [0006]    To enhance the resonante frequency of the head suspension to operate the magnetic head, it has been conventionally proposed to increase the thickness of the head suspension entirely or partially, to welding two plates in order to partially increase the thickness of the head suspension, or to provide ribs on the head suspension. Namely, in the prior art, the frequency of the resonance point is enhanced by increasing a spring constant of the head suspension.  
           [0007]    However, such solution in the prior art increases the mass of the whole suspension, thus resulting in an influence on floating of a magnetic head slider which is attached to a tip of the head suspension. Namely, the rigidity of the head suspension in the upward and downward direction is so large that uneven floating takes place, or the mass of the whole suspension is increased, thus leading to a reduce shock resistance. An increase in the mass of the suspension makes large a drive system to drive the head suspension and increases the power consumption thereof.  
           [0008]    To solve the problems of the prior art, it has been proposed that two anisotropic fiber-reinforced composite layers are used to connect the head slider of the head suspension and a load beam portion of a support of the head slider (see Japanese Kokai No. 8-212741).  
           [0009]    However, in a head suspension structure described in Kokai No. 8-212741 in which the fibers are laminated with the orientations degree intersecting at 90 degrees, no optimization of the laminate structure is obtained. Therefore, the resonance frequency of the head suspension in the seeking direction tends to be lower than that of a conventional head suspension using SUS material. Also, there is a possibility that the rigidity of the head suspension in the upward and downward direction is increased.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is aimed to provide a head suspension of a good shock resistance and high resonance which contributes to development of an improved magnetic disk apparatus, in which the head suspension is made of laminated anisotropic material so that the external flexural rigidity is small and the internal flexural rigidity is large, whereby the rigidity of the head suspension, which has an influence on the floating of a head slider, can be reduced.  
           [0011]    To achieve the above purpose, the present invention can be embodied in the following first to fifth embodiments.  
           [0012]    In a head suspension of an oscillation-type actuator, in a first embodiment, in which a head to read/write data is provided at a tip end of the head suspension, at least a part of the head suspension is made of an anisotropic material whose rigidity varies depending on the direction.  
           [0013]    In a head suspension of a second embodiment, the anisotropic material referred to in the first embodiment forms a lamination structure in which the layers have different orientations of the high rigidity are different in layers.  
           [0014]    In a head suspension of a third embodiment, a pivot is provided near a head mounting position of the head suspension of the first or the second embodiment to apply pressure to the head toward a recording medium from or on which data is read/written by the head.  
           [0015]    In a head suspension of a fourth embodiment, a rigid body is formed on the head suspension in any of first through the third embodiment, by thickening a part of the head suspension more than the other portion thereof.  
           [0016]    In a head suspension of a fifth embodiment, the rigid body of the head suspension of the forth embodiment has a thickness larger than that of the remaining portion, by increasing the number of the anisotropic layers to be laminated.  
           [0017]    In the head suspension of the above described embodiments, the anisotropic layers are laminated so that the external flexural rigidity of the head suspension is small and the internal flexural rigidity is large. Consequently, for example, if an anisotropic material such as a carbon fiber reinforced plastic (CFRP) is used, a three-layer structure can be obtained in which a layer of a carbon fiber reinforced plastic (CFRP) oriented in the longitudinal direction of the suspension is sandwiched between layers of carbon fiber reinforced plastics (CFRP) oriented in the width direction thereof. Thus, a head suspension having low rigid, high resonance, light and good shock resistance can be designed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The present invention will be more clearly understood from the description as set forth below with references to the accompanying drawings, wherein:  
         [0019]    [0019]FIG. 1A is a left side view showing a conventional head actuator having a head suspension.  
         [0020]    [0020]FIG. 1B is a plan view showing a conventional head actuator having a head suspension.  
         [0021]    [0021]FIG. 1C is a right side view showing a conventional head actuator having a head suspension.  
         [0022]    [0022]FIG. 2A is a perspective view showing the first embodiment of a head suspension according to the present invention.  
         [0023]    [0023]FIG. 2B is an enlarged partial view in a part B of FIG. 2A.  
         [0024]    [0024]FIG. 2C is an exploded perspective view showing orientations of three anisotropic layers laminated as shown in FIG. 2B by way of example.  
         [0025]    [0025]FIG. 3 is an exploded perspective view of the same part as FIG. 2C, showing orientations of carbon fibers when the anisotropic layers of the FIG. 2C are made of CFRP.  
         [0026]    [0026]FIG. 4 is a table explaining an effect of a head suspension of the present invention.  
         [0027]    [0027]FIG. 5A is an exploded perspective view explaining orientations of anisotropic layers when the head suspension shown in FIG. 2A has a five-layer structure, by way of example.  
         [0028]    [0028]FIG. 5B is an exploded perspective view showing another example of orientations of anisotropic layers when the head suspension shown in FIG. 2A has a five-layer structure.  
         [0029]    [0029]FIG. 6A is an exploded perspective view showing another example of orientations of anisotropic layers explained in FIG. 2C.  
         [0030]    [0030]FIG. 6B is an exploded perspective view showing an example of orientations of anisotropic layers when the head suspension has a five-layer structure.  
         [0031]    [0031]FIG. 7A is a perspective view of a head suspension structure of a second embodiment of the present invention in which a pivot is provided on the head suspension to press a head slider.  
         [0032]    [0032]FIG. 7B is an enlarged partial view side of a tip end of the head suspension shown in FIG. 7A.  
         [0033]    [0033]FIG. 7C is an explanatory view explaining a rotating direction of a head slider shown in FIG. 7A and FIG. 7B by the pivot.  
         [0034]    [0034]FIG. 8A is a perspective view showing a third embodiment of a head suspension of the present invention.  
         [0035]    [0035]FIG. 8B is an enlarged partial view of a main part of FIG. 8A.  
         [0036]    [0036]FIG. 9A is a perspective view showing a forth embodiment of a head suspension of the present invention.  
         [0037]    [0037]FIG. 9B is an enlarged partial view of a main part of FIG. 9A. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]    Before describing the preferred embodiments, an explanation will be given of a head actuator using a conventional head suspension shown in FIGS. 1A to  1 C.  
         [0039]    [0039]FIGS. 1A through 1C show a structure of a head actuator  60  having a conventional head suspension  74  in a disk apparatus. FIG. 1A is a left side view of the head actuator  60 , FIG. 1B is a plan view of the head actuator  60 , and FIG. 1C is a right side view of the head actuator  60 . The head actuator  60  is attached to a rotation shaft  76 , such as a pin, and oscillates about the rotation shaft  76 . Carriage arms  72  which are in the form of a comb in side view are provided on one side of the rotation shaft  76 . One or two head suspension(s)  74  is(are) attached to the tip end of each carriage arm  72 . At the tip ends of the head suspensions  74 , head sliders  71  having heads to transmit and receive the data to and from a disk medium are provided.  
         [0040]    Two supporting arms  73  are provided on the side opposite to the carriage arm  72  with respect to the rotation shaft  76 , and a flat coil  75  is interposed between the supporting arms  73 . The flat coil  75  is opposed to a magnetic circuit (not shown) provided on the base side of a disk apparatus, so that the head actuator  60  oscillates according to the value of a current flowing in the flat coil  75 .  
         [0041]    A base  70  of each head suspension  74  is joined to the tip end of the corresponding carriage arm  72 . A head fine movement mechanism may be optionally provided on the joint base  70  of each head suspension  74  to finely move the head suspension  74  independently of the oscillation of the head actuator  60 . Ribs  77  are partially provided on the head suspension  74  to enhance the resonance frequency in the conventional head suspension  74 .  
         [0042]    For these reasons, the mass of the entirety of the conventional head suspension  74  is increased, thus resulting in an advance influence on the floating of the head sliders  71  mounted to the tip ends of the head suspensions  74  or in an increase of the rigidity of the head suspensions  74  in the upward and downward directions, leading to uneven floating.  
         [0043]    [0043]FIG. 2A shows a head suspension  11  according to a first embodiment of the present invention, which is attached at the same position as the head suspension  74  shown in FIG. 1A through FIG. 1C. A substantially Ushaped hole  2  is provided at the tip end of the spring arm  5  which constitutes the head suspension  11 . A hinge  3  and a slider mounting portion  4  are formed in the substantially U-shaped hole  2 . A head slider  1  having an inductance head or an MR head is mounted to the slider mounting portion  4 .  
         [0044]    The spring arm  5  in the first embodiment is comprised of three layers of anisotropic material  20  having different rigidities (elasticity moduli) depending on the direction, as shown in FIG. 2B. Each anisotropic layer  20  exhibits a high elasticity modulus in a direction (represented by thick arrows) and a low elasticity modulus in another direction (represented by thin arrows) perpendicular to the first direction, as shown in FIG. 2C. In the first embodiment, the three anisotropic layers  20  are laminated to constitute the spring arm  5 . Intermediate anisotropic layer  20   c  exhibits a high elasticity modulus in a direction identical to the center line C-C of the head suspension  11 . The upper and lower anisotropic layers  20   a  and  20   b  between which the anisotropic material  20   c  is interposed exhibits a high elasticity modulus in a direction perpendicular to the direction in which the intermediate anisotropic layer  20   c  exhibits the high elasticity modulus. (the width direction of the head suspension  11 ).  
         [0045]    If the anisotropic layers  20  which form the spring arm  5  are laminated as shown in FIG. 2C, the flexural rigidity of the spring arm  5  in the upward and downward direction is reduced, so that the rigidity which has an influence on the floating of the head slider  1  can be restricted. Furthermore, the internal flexural rigidity of the spring arm  5  is increased, and the resonance frequency of the head suspension  11  is increased.  
         [0046]    [0046]FIG. 3 shows an embodiment in which anisotropic layers  20 A made of carbon fiber reinforced plastic (CFRP) are used instead of the anisotropic layers  20  shown in FIG. 2C. The anisotropic layers  20 A are each in the form of a plate made of parallel carbon fibers  21  covered with a filler agent  22  such as resin. The direction in which it exhibits a high elasticity modulus extends along the carbon fibers. Therefore, in this embodiment, the anisotropic materials  20 A are oriented, so that the carbon fibers  21  extend in directions in which the corresponding anisotropic layers  20 A to  20 C have high elasticity moduli.  
         [0047]    As described above, the spring arm  5  is formed by a laminate structure in which the carbon fibers  21  of the adjacent upper and lower layers extend in orthogonal directions, and thus, the flexural rigidity direction of the head suspension  11  in the upward and downward direction is reduced and the rigidity which has an influence on the floating of the head slider  1  restricted. Furthermore, the internal flexural rigidity of the spring arm is increased, thus resulting in an increase of the resonance frequency of the head suspension  11 .  
         [0048]    [0048]FIG. 4 shows properties of the head suspension  11  made of the anisotropic layers  20 A, in comparison with those of head suspension made of stainless steel (SUS) which has been conventionally used. As seen in FIG. 4, if the conventional SUS  304  (0.08C-18Cr-8Ni) is used, the resonance frequency is increased, but the rigidity is also increased. Further, the equivalent mass is also increased, and thus, a shock resistance is reduced. On the other hand, if the head suspension  11  is formed by the spring arm  5  which is made of laminated anisotropic layers  20 A, as shown in FIG. 3, it is possible to increase the resonance frequency without increasing the rigidity of the head suspension  1 . Moreover, the equivalent mass is reduced, and therefore, the shock resistance of the head suspension  11  can be improved.  
         [0049]    [0049]FIG. 5A and FIG. 5B shows two examples of orientations of the anisotropic layers  20  when the head suspension shown in FIG. 2 A is comprised of a spring arm  5  of five-layer structure. In an example of FIG. 5A, the anisotropic layers  20   d  and  20   e  are additionally interposed between the upper anisotropic layer  20   a  and the anisotropic layer  20   c  shown in FIG. 2C and between the lower anisotropic layer  20   b  and the anisotropic layer  20 C, respectively. The anisotropic layers  20   d ,  20   e  exhibits the high elasticity modulus in a direction (identical to the direction of the anisotropic layer  20   c  and parallel with the center line of the head suspension  11 ) perpendicular to a direction in which the anisotropic layers  20   a ,  20   b  exhibit the high elasticity modulus.  
         [0050]    To the contrary, in an example in FIG. 5B, the anisotropic layer  20   f  having a high elasticity modulus oriented in the width direction of the head suspension  11  is used as the middle layer of the five layers. Two upper anisotropic layers and two lower anisotropic layers  20   g ,  20   h ,  20   i ,  20   j , are arranged as shown in the drawing, so that their higher elasticity modulus directions are alternatively orthogonal to each other. The example of FIG. 5 A can provide a higher resonance frequency than that of FIG. 5B, however, the example of FIG. 5B could be more advantageous in accordance with the usage.  
         [0051]    [0051]FIG. 6A shows another example of the orientations of the anisotropic material shown in Fig,  2  C. In this example, the high elasticity modulus direction of the intermediate anisotropic layer  20   c  is identical to the center line C-C of the head suspension  11  shown in FIG. 2A. The high elasticity modulus directions of the upper and lower anisotropic layers  20   k  and  20   m  between which the anisotropic layer  20   c  is interposed from 45° with respect to the high elasticity modulus direction of the anisotropic layer  20   c . The high elasticity modulus directions of the anisotropic layers  20   k  and  20   m  are orthogonal to each other.  
         [0052]    In an example of FIG. 6B, the outermost anisotropic layers  20   p  and  20   q  are respectively laminated on the upper and lower anisotropic layers  20   k ,  20   m  between which the anisotropic layer  20   c  shown in FIG. 6A is interposed. The high elasticity modulus directions of the anisotropic layers  20   p  and  20   q  are perpendicular to those of the anisotropic layers  20   k  and  20   m , respectively. The anisotropic layers  20   p  and  20   k  can be replaced with the anisotropic layers  20   m  and  20   q  and vice versa. As can be seen from the foregoing, the high elasticity modulus directions of the anisotropic layers  20  in the present invention are not limited to the direction identical to the center line of the head suspension  11  and the direction perpendicular thereto.  
         [0053]    [0053]FIG. 7A shows a head suspension  12  of a second embodiment of the present invention. The second embodiment differs from the first embodiment in the point that a pivot  6  is provided on the tip end of the head suspension  5  explained with reference to the first embodiment, to press the head slider  1 .  
         [0054]    To provide the pivot  6  on the tip end of the head suspension  5 , the portion of the slider attachment portion  4  opposite to the hinge  3  in the first embodiment is cut away. The substantially U-shaped hole  2 , in the first embodiment, is replaced with a substantially W-shaped hole  8  due to a pivot holding portion  7  on which the pivot  6  is formed.  
         [0055]    The pivot  6  is projected from the pivot holding portion  7  toward the head slider  1 , as shown in FIG. 7B, to thereby press the back of the head slider  1 , so that the head-provided side of the head slider  1  comes close to a magnetic recording medium. The head suspension  12  in the second embodiment can apply the pressing load to the back of the head slider  1 , due to the pivot  6 .  
         [0056]    [0056]FIG. 7C shows a back surface of the head slider  1 , in which the portion to be pressed by the pivot  6  is indicated by X. Due to the pivot  6 , the head slider  1  can rotate in directions indicated by Y and Z about the point X at which the force is applied by the pivot.  
         [0057]    [0057]FIG. 8A shows a head suspension  13  of a third embodiment of the present invention. In the head suspension  13  of the third embodiment, a rigid body  9  is provided on a part of the head suspension  11  of the first embodiment. In the third embodiment, the spring arm  5  is comprised of four anisotropic layers  20 A of CFRP. The rigid body  9  is made of one anisotropic layer  20 A superimposed on each of the upper and lower surfaces of the spring arm  5 .  
         [0058]    [0058]FIG. 8B shows an enlarged view of an end of the rigid body  9 . In the spring arm  5  of the third embodiment, the two intermediate anisotropic layers  20 X in which the carbon fibers  21  are oriented in the longitudinal direction of the head suspension  13  are used, and in the upper and lower anisotropic layers  20 Y in which the carbon fibers  21  are oriented in a direction perpendicular to the longitudinal direction are used. The rigid body  9  is constructed by the anisotropic layers  20 X that have the carbon fibers  21  oriented in the longitudinal direction and that are laminated in the upward and downward direction of the spring arm  5 . Namely, the rigid body  9  is symmetric with respect to the spring arm  5  in the upward and downward direction.  
         [0059]    [0059]FIG. 9A shows a head suspension  14  of a fourth embodiment of the present invention. In the head suspension  14  of the fourth embodiment, a rigid body  10  is provided on a part of the head suspension  11  of the first embodiment. In the fourth embodiment, the spring arm  5  is made of four anisotropic layers  20 A of CFRP. The rigid body  9  is formed by inserting two the anisotropic layer  20 A between the two intermediate layers of the spring arm  5 .  
         [0060]    [0060]FIG. 9B is an enlarged view of tip end of the rigid body  10 . In the spring arm  5  of the fourth embodiment, the two intermediate anisotropic layers  20 X have carbon fibers  21  oriented in the longitudinal direction of the head suspension  13  and the upper and lower anisotropic layers  20 Y have carbon fibers oriented in direction perpendicular to the longitudinal direction of the head suspension  13 . The rigid body  10  is formed of the anisotropic layers  20 X in which the carbon fibers  21  are oriented in the longitudinal direction of the head suspension  13  and which are interposed between the two intermediate layers  20 X of the spring arm  5 . Namely, the rigid body  10  is symmetric with respect to the spring arm  5  in the upward and downward direction.  
         [0061]    Because the thickness of the anisotropic layers  20 X,  20 Y is very small, the rigid body  9  or  10  provided on the head suspension  13  or  14  hardly increases the weight of the head suspension  13  or  14 .  
         [0062]    In the above described embodiments, although the carbon fiber reinforce plastic is used as an anisotropic material, the kind of the anisotropic material is not limited thereto.  
         [0063]    As explained above, in a head suspension of the present invention, since the anisotropic layers are laminated so that the external flexural rigidity of the head suspension is small and the internal flexural rigidity is large, if, for example, the anisotropic material such as CFRP is used, a three-layer structure in which a layer having carbon fibers oriented in the longitudinal direction of the suspension is interposed between layers having carbon fibers oriented in the width direction of the suspension can be obtained. Thus, a magnetic head suspension having a high shock-resistance and a high resonance frequency and a low rigidity having less influence on the floating can be provided, and this greatly contributes to an improvement in a magnetic disk apparatus.