Abstract:
The method for manufacturing a suspension for disc drive includes a process for manufacturing a semi-finished suspension product integrally including a base plate, a rigid body portion of a load beam, and a pair of connecting portions connecting the base plate and the rigid body portion. The method also includes a process for fixing a spring member, formed independently of the semi-finished suspension product, to the base plate and the rigid body portion of the semi-finished product, and a process for cutting off the connecting portions, projecting individually from the opposite sides of the spring member, from the base plate and the rigid body portion after the spring member is fixed to the semi-finished suspension product.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a Divisional Application of U.S. patent application Ser. No. 10/732,699 filed Dec. 9, 2003, which is a Divisional Application of U.S. patent application Ser. No. 09/793,410 filed Feb. 26, 2001 (abandoned), which is a Continuation-in-Part application of U.S. patent application Ser. No. 09/450,138 filed Nov. 29, 1999 (abandoned), the entire contents of each of which are incorporated herein by reference. 
     
    
       [0002]     This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-263705, filed Sep. 17, 1999; and No. 2000-054097, filed Feb. 29, 2000, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates to a suspension for disc drive incorporated in an information processing apparatus, such as a personal computer, and a manufacturing method therefor.  
         [0004]     A hard disc drive (HDD) for recording on or retrieving information from a rotating magnetic disc or magneto-optical disc includes a carriage that can turn around a shaft. The carriage is turned around the shaft by means of a positioning motor.  
         [0005]     As described in U.S. Pat. No. 4,167,765, for example, the carriage is provided with an arm, a suspension on the distal end portion of the arm, a head portion including a slider attached to the suspension, etc. When the slider is slightly lifted from the disk as the disk rotates at high speed, an air bearing is formed between the disk and the slider.  
         [0006]     The suspension comprises a load beam formed of a precision thin plate spring, a flexure formed of a very thin plate spring that is fixed to the distal end portion of the load beam by laser welding or the like, and a base plate fixed to the proximal portion of the beam by laser welding or the like. The base plate is fixed to a suspension mounting surface of the arm.  
         [0007]     In modern disk drives of this type, the density of information to be recorded tends to be enhanced, and the disk rotation has an inclination to higher speed. Accordingly, the suspensions for disk drive require a good vibration characteristic such that they can be positioned highly accurately with respect to the recording surface of disks. Further, the suspensions should not be easily influenced by air turbulence that is caused by high-speed rotation of the disks. To meet the demand for various new functions, moreover, the suspensions of this type also tend to be subjected to more complicated machining.  
         [0008]     As the density of information to be stored in each disk increases, the suspensions are expected to have high stiffness and a low spring constant.  FIG. 14  shows one such conventional suspension  1 , which comprises a load beam  2  that integrally includes a rigid body portion  2   a  of length L 1  and a spring portion  2   b  of length L 2 . Conventionally, therefore, the necessary performance (high stiffness) for the rigid body portion  2   a  and the performance (low spring constant) required by the spring portion  2   b  cannot be secured at the same time.  
         [0009]     The material and thickness of the whole rigid body portion  2   a , in particular, are inevitably restricted by the required properties of the spring portion  2   b . In order to enhance the stiffness of the body portion  2   a , therefore, it is necessary to form bent edges  3  by bending the opposite side edges of the rigid body portion  2   a  or to form ribs  4  by embossing. Accordingly, the load beam  2  must be subjected to high-accurately machining, thus entailing a lot of processes for machining, and therefore, high costs.  
         [0010]     The bent edges  3  or ribs  4  on the load beam  2  may hinder a flow of air. When a disc rotates at high speed, therefore, the load beam  2  is easily influenced by air turbulence and flutters. A base plate  5  is fixed to the proximal portion of the load beam  2 . Further, a flexure  6  is fixed to the distal end portion of the load beam  2 . The flexure  6  is fitted with a slider  8  that constitutes a head portion  7 .  
         [0011]     In a load beam described in Jpn. Pat. Appln. KOKAI Publication No. 9-191004, for example, the thickness of a spring portion is partially reduced by partial etching in order to lower the spring constant of the load beam. Since the thickness of the spring portion cannot be accurately controlled by partial etching, however, it is unstable, so that the spring constant is liable to variation.  
         [0012]     In the case of the suspension described in Jpn. Pat. Appln. KOKAI Publication No. 9-128919, a plurality of narrow plate spring portions are formed around a slider mounting portion of a load beam by etching or pressing. The plate spring portions are deformed in the thickness direction. In this prior art example, the plate spring portions should be formed in a narrow region on the distal end of the load beam. Therefore, the load beam requires very delicate machining, so that its shape and spring constant are liable to variation and its quality is unstable.  
       BRIEF SUMMARY OF THE INVENTION  
       [0013]     Accordingly, the object of the present invention is to provide a high-performance suspension for disc drive, capable of ensuring required performance, and a manufacturing method therefor.  
         [0014]     In order to achieve the above object, a suspension for disc drive according to the present invention comprises a base plate, a load beam attached to the base plate, and a flexure attached to the load beam and adapted to be fitted with a head portion. In this suspension, the load beam includes a rigid body portion, independent of the base plate and fixedly fitted with the flexure, and a spring portion formed of a spring member formed independently of the rigid body portion, connecting the body portion and the base plate, and having a spring constant lower than that of the body portion.  
         [0015]     In this suspension, the rigid body portion and the spring portion that constitute the load beam are separate components. In order to obtain the necessary performance for the suspension, therefore, suitable materials, thicknesses, etc. may be selected individually for the rigid body portion and the spring portion. For example, a thick plate is used for the rigid body portion of the load beam, while a high-accuracy spring member with a low spring constant, such as a thin rolled steel sheet is used for the spring portion.  
         [0016]     For example, stainless steel may be used for the rigid body portion of the load beam. If the rigid body portion is formed of an alloy of a light metal (lighter than iron), such as a titanium or aluminum, or a synthetic resin, however, further reduction of weight and higher stiffness can be reconciled. Alternatively, the load beam and other structural components may be made of a laminated member made up of a light metal (e.g., aluminum-based metal, titanium, or the like) and a metal other than the light metal. Instead of the light metal, an alloy containing the light metal as its main ingredient may be used. The “laminated member” referred to in the present specification may be a clad member obtained by forcibly pressing different kinds of metals against one another, or an integral member obtained by bonding different kinds of metals together. In the present specification, the term “aluminum-based metal” is intended to cover not only an aluminum alloy but also pure aluminum. In this manner, the load beam or the arm-type long base plate is made of a laminated member, and this laminated member is formed of an aluminum-based metal, a Ti alloy, or a material containing at least two kinds of light metal alloys. Accordingly, the load beam and/or other structural components is light in weight, and improved in frequency and vibration characteristics. It should be noted that the components may be homogenized by forming the flexure and the spring portion integrally with each other from one continuous metal plate.  
         [0017]     According to the invention, the material and thickness of the rigid body portion that constitutes the load beam cannot be restricted by the spring portion of the load beam. Therefore, suitable materials and thicknesses may be selected individually for the rigid body portion and the spring portion to meet their respective requirements, so that the necessary performance for the suspension can be fulfilled. If the rigid body portion of the load beam is formed of a thick plate, for example, its stiffness can be further enhanced and air resistance against it can be reduced without forming bent edges or ribs on the load beam. Thus, the influence of air turbulence is lessened when a disc rotates at high speed, and suspension fluttering can be restrained.  
         [0018]     According to the suspension of the invention, the spring portion can enjoy a steady low spring constant, and high accuracy of the spring portion can be reconciled with the low spring constant. Since the rigid body portion of the load beam and the spring portion are separate components, the rigid body portion can be formed of a material softer than that of the spring portion. Thus, the rigid body portion can be formed with a higher degree of freedom of work, such as pressing.  
         [0019]     Preferably, according to the invention, the rigid body portion of the load beam is formed of a light metal or synthetic resin. If the load beam is formed of a material with a low specific gravity, such as an aluminum or titanium alloy or synthetic resin, in this case, the load beam is reduced in weight, and its frequency and vibration characteristics are improved. By using the low-gravity material for both the load beam and the base plate, moreover, the whole suspension can be further reduced in weight, and the operation of the disc drive can be speeded up.  
         [0020]     Preferably, moreover, the flexure and the spring portion are formed of one integral metal sheet. With this arrangement, the number of components that constitute the suspension can be reduced, and the accuracy of relative positioning of the flexure and the spring portion can be improved.  
         [0021]     A method for manufacturing a suspension according to the invention uses a semi-finished suspension product, which integrally includes a base plate, a rigid body portion of a load beam, and a pair of connecting portions connecting the base plate and the rigid body portion. The method also uses a spring member that is formed independently of the semi-finished suspension product. The distance between the connecting portions of the semi-finished product is greater than the width of the spring member. After the spring member is fixed to the base plate and the rigid body portion of the semi-finished product, the connecting portions, which project individually from the opposite sides of the spring member, are cut off from the base plate and the rigid body portion. According to this manufacturing method, the base plate and the rigid body portion can be handled as one body in some preceding processes for manufacturing the suspension. Thus, a common material can be used for the base plate and the rigid body portion, so that the number of components used in the suspension can be reduced, and the base plate and the rigid body portion can be positioned with higher accuracy as the spring member is fixed to them.  
         [0022]     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0023]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
         [0024]      FIG. 1  is a perspective view of a suspension for disc drive according to a first embodiment of the present invention;  
         [0025]      FIG. 2  is an exploded perspective view of the suspension shown in  FIG. 1 ;  
         [0026]      FIG. 3  is a side view, partially in section, showing a hard disc drive provided with the suspension shown in  FIG. 1 ;  
         [0027]      FIG. 4  is a perspective view of a suspension for disc drive according to a second embodiment of the invention;  
         [0028]      FIG. 5  is a perspective view of a suspension for disc drive according to a third embodiment of the invention;  
         [0029]      FIG. 6  is a perspective view of a suspension for disc drive according to a fourth embodiment of the invention;  
         [0030]      FIG. 7  is a perspective view of a suspension for disc drive according to a fifth embodiment of the invention;  
         [0031]      FIG. 8  is a perspective view showing a semi-finished suspension product and a spring member used in the suspension shown in  FIG. 7 ;  
         [0032]      FIG. 9  is a perspective view of a suspension for disc drive according to a sixth embodiment of the invention;  
         [0033]      FIG. 10  is an exploded perspective view of a suspension for disc drive according to a seventh embodiment of the invention;  
         [0034]      FIG. 11  is a perspective view of a suspension according to an eighth embodiment of the present invention;  
         [0035]      FIG. 12  is a perspective view of a suspension according to a ninth embodiment of the present invention;  
         [0036]      FIG. 13  is a graph showing resonance characteristics of a SUS/Al Clad-Beam, a SUS-Beam and Al-Beam; and  
         [0037]      FIG. 14  is a perspective view of a conventional disc-drive suspension. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]     A first embodiment of the present invention will now be described with reference to FIGS.  1  to  3 . A hard disc drive (HDD)  10  shown in  FIG. 3  includes a carriage  12  that can turn around a shaft  11 . The carriage  12  is turned around the shaft  11  by means of a positioning motor  13  such as a voice coil motor.  
         [0039]     The carriage  12  is provided with a plurality of arms (actuator arms)  16 , suspensions  17  mounted individually on the respective distal end portions of the arms  16 , head portions  18  provided individually on the respective distal end portions of the suspensions  17 , etc. When the carriage  12  is actuated by the motor  13 , each head portion  18  moves to a desired track of its corresponding disc  19 .  
         [0040]     Each head portion  18  includes a slider  20 , which is situated in a position such that it can face the tracks of the disc  19 , a transducer (not shown) held thereon, etc. When the disc  19  rotates at high speed, the slider  20  is slightly lifted from the disc  19  by air between the two members, whereupon an air bearing is formed between the disc  19  and the slider  20 .  
         [0041]     As shown in  FIG. 1 , each suspension  17  includes a base plate  30 , a load beam  31  attached to the plate  30 , etc. As shown in  FIG. 3 , the base plate  30  is fixed to its corresponding arm  16 . The base plate  30  is formed having a circular hole  33  into which a boss portion (not shown) of the arm  16  is to be inserted.  
         [0042]     As shown in  FIG. 2 , each load beam  31  is provided with a rigid body portion  40 , which is independent of the base plate  30 , and a spring portion  42  formed of a spring member  41  fixed to the body portion  40 . The rigid body portion  40  is thicker than the spring member  41 . That portion of the spring member  41  which corresponds to length L in  FIG. 1  is a region that functions as the spring portion  42 . The spring portion  42  has a spring constant smaller than that of the body portion  40 , and therefore, is more flexible. To reconcile lightweight and high stiffness, the illustrated body portion  40  is formed of a light alloy, such as an aluminum alloy, and is penetrated by apertures  45  in the thickness direction.  
         [0043]     The apertures  45  may be replaced with recesses that are formed by partially reducing the thickness of the rigid body portion  40  by, for example, etching. A light metal (lower in specific gravity than iron), such as a titanium or aluminum alloy, or a synthetic resin may be used when forming the load beam  31 . To be specific, the load beam  31  may be made of a laminated member made up of an Al alloy plate and a stainless steel plate. With use of one such low-gravity material, the load beam  31  can be reduced in weight, and its frequency and vibration characteristics can be improved. If necessary, the load beam  31  may be subjected to bending.  
         [0044]     The plate-like spring member  41  that constitutes the spring portion  42  is formed of a springy rolled stainless-steel sheet, for example. One end portion  41   a  of the spring member  41  is put on and fixed to an end portion  40   a  of the rigid body portion  40  by laser welding or the like. The other end portion  41   b  of the spring member  41  is put on and fixed to the base plate  30  by laser welding or the like.  
         [0045]     The spring member  41  may be fixed to the rigid body portion  40  of the load beam  31  with use of an adhesive in place of welding. In the case where the body portion  40  is formed of a synthetic resin, the spring member  41  may be fixed to it by the so-called in-mold forming. In this in-mold forming, the spring member  41  is set in a mold for molding the rigid body portion  40 , and a resin material is poured into the mold in this state and cured.  
         [0046]     A flexure  50 , a very thin plate spring, is attached to the rigid body portion  40 . The flexure  50 , which is formed of a rolled stainless-steel sheet, for example, is fixed to the load beam  31  by laser welding or the like. As shown in  FIG. 2 , a protuberance  51  is provided on an end portion  40   b  of the body portion  40 . The protuberance  51  is in contact with a tongue portion  52  of the flexure  50 . The protuberance  51  projects toward the tongue portion  52 . The slider  20 , which constitutes each head portion  18 , is mounted on the flexure  50 .  
         [0047]     In the suspension  17  constructed in this manner, the rigid body portion  40  and the spring portion  42  that constitute each load beam  31  are separate components. Suitable materials and thicknesses may be selected individually for the body portion  40  and the spring portion  42 . Accordingly, it is easy to reconcile the necessary performance (e.g., high stiffness) for the body portion  40  and the required performance (e.g., low spring constant) for the spring portion  42 . Since a high-accuracy rolled sheet is used for the spring member  41 , moreover, the spring portion  42  can enjoy a steady low spring constant.  
         [0048]     A thick plate can be used for the load beam  31  according to this embodiment. As compared with the prior art example of  FIG. 14  that is provided with the bent edges and ribs, therefore, the load beam  31  can be shaped so that it cannot easily disturb a flow of air, and stiffness of the load beam  31  is enhanced. Thus, the influence of air turbulence is lessened even though the disc rotates at high speed.  
         [0049]      FIG. 4  shows a suspension  17 A according to a second embodiment of the invention. A spring portion  42  of the suspension  17 A includes bent portions  60 , which are formed by bending the longitudinally intermediate portion of a spring member  41 . For other arrangements, the suspension  17 A resembles the suspension  17  according to the first embodiment, so that common reference numerals are used to designate portions that are common to the first and second embodiments, and a description of those portions is omitted.  
         [0050]      FIG. 5  shows a suspension  17 B according to a third embodiment of the invention. The suspension  17 B has an aperture  61  formed in the central portion of a spring member  41 . The opposite sides of the aperture  61  of the spring member  41  serves as a spring portion  42  with a low spring constant. Bent portions  60  are formed by partially bending the spring member  41 . For other arrangements, the third embodiment resembles the first embodiment, so that common reference numerals are used to designate portions that are common to the first and third embodiments, and a description of those portions is omitted.  
         [0051]      FIG. 6  shows a suspension  17 C according to a fourth embodiment of the invention. The suspension  17 C is provided with a base plate  30 C of the so-called arm type (i.e., a base plate having an arm) and a flexure  50 C which has a wiring board. The wired flexure  50 C includes a metal substrate  65 , such as a springy rolled stainless-steel sheet, an electric insulating layer formed on the surface of the substrate  65 , and conductive lines  66  on the insulating layer. One end of each conductive line  66  is connected electrically to terminals  67  of a head portion  18 , and the other end to terminals  68  on the base plate  30 C. A part of a spring member  41  is formed having bent portions  60  and an aperture  61 . For other arrangements, the fourth embodiment resembles the first embodiment, so that common reference numerals are used to designate portions that are common to the first and fourth embodiments, and a description of those portions is omitted. The arm of the arm-type base plate  30 C may be made of: a light metal such as Ti, Al alloy, or the like (i.e., a metal lower in specific gravity than iron); a laminated member made up of Al and stainless steel; a synthetic resin; or fiber-reinforced plastics. By use of these materials, the weight can be as light as possible, and the frequency and vibration characteristics can be improved.  
         [0052]      FIG. 7  shows a suspension  17 D according to a fifth embodiment of the invention. The suspension  17 D is manufactured using a semi-finished suspension product  70 , such as the one shown in  FIG. 8 . The semi-finished product  70  includes a base plate  30 , a rigid body portion  40  of a load beam  31 , and a pair of connecting portions  71 , right and left, connecting the plate  30  and the body portion  40 . The semi-finished product  70  is formed having the elements  30 ,  40  and  71  by press working, for example. The distance (W 1 ) between the two connecting portions  71  is greater than the width (W 2 ) of the spring member  41 . When the spring member  41  is put on the base plate  30  and the rigid body portion  40 , as shown in  FIG. 7 , the connecting portions  71  project individually from the opposite sides of the member  41 .  
         [0053]     The spring member  41  is put on both the rigid body portion  40  of the semi-finished suspension product  70  and the base plate  30 , and is fixed to the plate  30  and the body portion  40  by laser welding or the like. Thereafter, the connecting portions  71  that project from the opposite sides of the spring member  41  are cut off from the body portion  40  and the base plate  30  by press working or the like.  
         [0054]     According to this embodiment, the base plate  30  and the rigid body portion  40  are connected by means of the connecting portions  71  so that they form one integral part before the spring member  41  is fixed to the semi-finished suspension product  70 . Thus, the base plate  30  and the body portion  40  can be handled with ease, and their relative positions can be regulated more accurately.  
         [0055]      FIG. 9  shows a suspension  17 E according to a sixth embodiment of the invention. The suspension  17 E has a spring portion  42  and a flexure  50  that are formed from one platelike spring member  41 E. In this case, the components can be homogenized by forming the spring portion  42  and the flexure  50  integrally with each other. Further, a rigid body portion  40  and a base plate  30 , like those of the semi-finished suspension product  70  according to the fifth embodiment, are connected by means of a pair of connecting portions  71 . The distance (W 1 ) between the two connecting portions  71  is greater than the width (W 2 ) of the spring member  41 E. After the spring member  41 E is fixed to the semi-finished product  70 , the connecting portions  71  that project individually from the opposite sides of the spring member  41 E are cut off.  
         [0056]      FIG. 10  shows a suspension  17 F according to a seventh embodiment of the invention. In the suspension  17 F, a spring portion  42  and a portion  80  to be put on a base plate  30  are formed integrally on a platelike spring member  41 F that constitutes a flexure  50 F which has a wiring board. The wired flexure  50 F includes an electric insulating layer formed on the surface of a metal substrate  65 , such as a springy rolled stainless-steel sheet, and conductive lines  66  on the insulating layer. One end of each conductive line  66  is connected electrically to terminals  67  of a head portion, and the other end to terminals  68  on the portion  80  that is put on the base plate  30 . A body portion  40  and the base plate  30  according to this embodiment, like those of the semi-finished suspension product  70  according to the fifth embodiment, are connected by means of a pair of connecting portions  71 . After the spring member  41 F is fixed to the semi-finished product  70 , the connecting portions  71  that project individually from the opposite sides of the spring member  41 F are cut off.  
         [0057]      FIG. 11  shows a suspension  17 G of the eighth embodiment of the present invention. According to the eighth embodiment, the rigid body portion  40  of the load beam  31  is a laminated member (referred to as “SUS/Al Clad-beam” herein) made up of: a first plate AL 1  formed of an aluminum alloy and having a thickness of 100 μm, and a second plate ST 1  formed of a stainless steel and having a thickness of 30 μm. Likewise, the base plate  30  is a laminated member made up of: a first plate AL 2  formed of a light alloy such as an aluminum-alloy; and a second plate ST 2  formed of a stainless steel. The spring member  41  is formed of a stainless steel. The spring member  41  is laser-welded to the stainless steel plate ST 1  of the rigid body portion  40  and the stainless steel plate ST 2  of the base plate  30 . In  FIG. 11 , reference symbol “P” indicates the welded portions.  
         [0058]      FIG. 12  shows a suspension  17 H of the ninth embodiment of the present invention. According to the ninth embodiment, the rigid body portion  40  of the load beam  31  is a laminated member (referred to as “SUS/Al Clad-beam” herein) made up of: a first plate ST 3  formed of a stainless steel; and a second plate AL 1  formed of an aluminum alloy. The spring member  42  is made by part of the first plate ST 3 . The base plate  30  is made of a second plate AL 2  formed of a light alloy such as an aluminum alloy. This second plate AL 2  is overlaid with the first plate ST 3  of stainless steel.  
         [0059]      FIG. 13  is a graph showing the first torsion mode resonance frequency. As shown in this graph, the first torsion mode resonance frequency of the SUS/Al Clad-beam is higher than that of the load beam (SUS-beam) formed only of stainless steel. In addition, the SUS/Al Clad-beam is lighter in weight than the SUS-beam whose thickness is 100 μm. Hence, the SUS/Al Clad-beam is reliable in frequency and vibration characteristics. As indicated by the one-dot-chain lines in  FIG. 13 , an Al-beam formed of aluminum alone and having a thickness of 160 μm may show satisfactory frequency characteristics. However, the Al-beam cannot be easily laser-welded to a flexure or base plate formed of stainless steel.  
         [0060]     It is to be understood that the components of the suspension, such as the base plate, load beam, flexure, rigid body portion, spring member, etc., may be suitably modified without departing from the scope or spirit of the invention in carrying out the invention.  
         [0061]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.