Rotational disc type storage device

Embodiments of the present invention help to stabilize a tilt amount of a head gimbal assembly with respect to a magnetic disc. According to one embodiment of the present invention, in a head stack assembly in which a head gimbal assembly, a carriage, and a head gimbal assembly are stacked and fixed by a pivot cartridge, a spring washer and a nut, an annular recess portion having a length in the radial direction of a flange is formed on a contact face of the flange formed at one end of the cartridge, so that two places of a mount plate of the head gimbal assembly may be partially supported in the radial direction of the flange.

CROSS-REFERENCE TO RELATED APPLICATION

The instant nonprovisional patent application claims priority to Japanese Patent Application No. 2006-187901 filed Jul. 7, 2006 and which is incorporated by reference in its entirety herein for all purposes.

BACKGROUND OF THE INVENTION

A magnetic disk device as a rotational disc type storage device is used as a data storage device for a personal computer, a server or the like.

This magnetic disk device includes a disc type magnetic disk that is equipped with a recording face having a magnetic layer formed on the surface thereof and provided rotatably around a spindle shaft, a head stack assembly and a control unit for controlling reading/writing of data from/into a magnetic disk and the operation of the head stack assembly.

The head stack assembly is constructed by a head gimbal assembly, a carriage and a pivot cartridge. In the head gimbal assembly, a suspension load beam is fixed to a mount plate to be mounted on a carriage. The suspension load beam has a magnetic head for reading/writing data with the magnetic disk, and a slider for supplying an air bearing surface (ABS) to which a magnetic head is fixed. A coil support is formed at a part of the carriage, and the coil support holds a voice coil. The coil support is disposed in a magnetic field generated by a voice coil magnet and a voice coil yoke, and the voice coil magnet, the voice coil yoke and the voice coil comprise a voice coil motor (VCM) for generating driving force for rotating the carriage. The pivot cartridge is engagedly fitted in openings provided to the mount plate of the head gimbal assembly and the carriage to laminate the head gimbal assembly and the carriage. The laminated head gimbal assembly and carriage are fixedly pinched by a flange and a nut and fixed to the pivot cartridge. The head stack assembly thus constructed may be rotated around the pivot shaft.

When the magnetic disk is rotated, air flow at the surface forms an air bearing and applies buoyant force to the air bearing surface of the slider, so that the slider is slightly floated from the surface of the magnetic disk. By the driving force of the voice coil motor, the slider is turned around the center of the pivot shaft substantially in the radial direction of the magnetic disk under the state that the slider is slightly floated from the surface of the magnetic disk, whereby the magnetic head may read/write data at a predetermined position of the surface of the disk.

Such a magnetic disk device has been recently used for information electric household appliances and electrical equipment such as a notebook-size personal computer, a portable media player, a portable music player, a digital video camera or the like. In connection with advances in technology, hard disks used as data storage media of magnetic disk devices contained in information electric household appliances and electrical equipment, the magnetic disks are increased in data recording density and also microminiaturized. The promotion of the miniaturization of the magnetic disks performs developments of 2.5 type (2.5 inches (about 6.35 cm) type), and further 1 type (1 inch (about 2.54 cm) type). In the microminiaturized magnetic disk device, dimensional tolerance of the constituent devices are more remarkably small as compared with the conventional devices, and thus the processing precision and the mounting precision have been required to be more rigorously maintained. As an example, a magnetic disk and a head stack assembly are coupled to the base of a disk enclosure as different constituent devices. A slider coupled to a head gimbal assembly is designed so as to be floated from the recording surface of the magnetic disc by a fixed height under operation. Accordingly, the height of the head gimbal assembly with respect to the height of the recording surface of the magnetic disc under the assembly state must be converged within the range of the tolerance. Therefore, it is necessary that the magnetic disc is coupled to the base with high precision and also the head gimbal assembly is fixed to a pivot cartridge while rigorously keeping parallelism.

As such, a magnetic disk device has been proposed with an arcuate contact portion projecting toward a mount plate (arm) to be pinched between a flange and a nut (for example, see Japanese Patent Publication No. 8-203224 “Patent Document 1”). This contact portion is designed in an annular shape having a length in the radial direction of the flange and the nut. According to this magnetic disk device, the respective contact portions of the flange and the nut may keep the linear contact state to the mount plate (arm), and thus the parallelism of each contact face of the flange and the nut may reduce the influence on the mount plate (arm).

However, in conventional magnetic disk devices, the contact portion may be provided at only one place in cross-section in the radial direction of the flange and the nut, and thus the mount plate may be tilted along the shape of the contact portion. The reason why the mount plate is tilted along the shape of the contact portion as described above resides in that the end face of the opening of the mount plate is not supported at the contact portion. When the tilt direction of the mount plate is a separating direction from the magnetic disk, there may be considered a method of absorbing the tilt of the mount plate by adjusting the thickness of the flange or the carriage and approaching only the height position of the tip of the head gimbal assembly to a nominal value. However, according to this method, the clearance between the mount plate and the magnetic disk is reduced to a smaller value as it is nearer to the lamination portion of the mount plate with the flange and the carriage, and thus they interfere with each other with a high probability. Accordingly, it is very difficult to reduce the displacement of the height position by this method.

Furthermore, in order to prevent a situation that the pivot cartridge (hub) cannot be inserted into the opening due to production tolerance, a gap is provided between the pivot cartridge and the opening, and thus there is a case that the position of the mount plate supported at the contact portion is displaced within the range of the gap. When the position of the mount plate is displaced as described above, the height position of the head gimbal assembly is displaced.

BRIEF SUMMARY OF THE INVENTION

Embodiments in accordance with the present invention stabilize a tilt amount of a head gimbal assembly with respect to a magnetic disk. According to the particular embodiment disclosed inFIG. 1, in a head stack assembly4in which a head gimbal assembly, a carriage, and a head gimbal assembly are stacked and fixed by a pivot cartridge, a spring washer and a nut, an annular recess portion having a length in the radial direction of a flange is formed on a contact face of the flange formed at one end of the cartridge so that two places of a mount plate of the head gimbal assembly may be partially supported in the radial direction of the flange.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments in accordance with the present invention relate to a rotational disc type storage device such as a magnetic disk device, a magnetooptical disk device or the like, and particularly to a rotational disc type storage device having a structure that enhances the mounting precision of a head gimbal assembly.

Embodiments of the present invention provide a rotational disc type storage device having a structure that may enhance the precision of the relative positional relationship between a head gimbal assembly and a rotational disc type recording medium when a head stack assembly is installed into the rotational disc type recording device such as a magnetic disk device or the like.

A principle of embodiments of the present invention resides in that a member for pinching and fixing a head gimbal assembly and a carriage with a nut while the head gimbal assembly and the carriage are laminated is provided with a site for supporting the head gimbal assembly at two places in the cross-section in the radial direction of the flange, thereby fixing the head gimbal assembly under a stable state.

A first mode of embodiments according to the present invention comprises, a rotational disc type recording medium, a head gimbal assembly having a slider to which a head for reading data from the rotational disc type recording medium is coupled and having a first opening formed at the rear end portion thereof, a carriage to which the head gimbal assembly is coupled and that has a second opening, and a pivot member containing a flange that is in contact with a laminate surface of the head gimbal assembly, a support structure for supporting the laminate surface at two places in the cross-section in the radial direction of the flange being formed in the flange, and the pivot member penetrating through the first opening and the second opening, wherein the head gimbal assembly and the carriage that are fitted in the pivot member by a screw action are fixed to the pivot member while the head gimbal assembly and the carriage are stacked.

According to the first mode, the support structure formed in the flange partially supports the two places of the head gimbal assembly, and thus the effect of the parallelism of the flange may be eliminated, and the tilt of the head gimbal assembly along the shape of the support structure may be prevented. Accordingly, the height position of the head gimbal assemblies may be stabilized.

A second mode of embodiments according to the present invention comprises a rotational disc type recording medium, a head gimbal assembly having a slider to which a head for reading data from the rotational disc type recording medium is coupled and having a first opening formed at the rear end portion thereof, a carriage to which a plurality of head gimbal assemblies are coupled in connection with a plurality of respective stacked rotational disc type recording media, a second opening being provided to the carriage, a fixing member having a plane formed by spacing two projecting portions from each other at a fixed interval while the two projecting portions are disposed along the surrounding of the first opening so that the two projecting portions are in partial contact with the laminate surface of the head gimbal assembly provided at the uppermost position with respect to the carriage, a rotational member that is provided with the fixing member at one end thereof and with a screw portion at the other end thereof, and penetrates through the first openings of the plural head gimbal assemblies and the second opening of the carriage, and a nut that is screwed into the screw portion of the rotational member by a screw action and fixes the plural head stack assemblies and the carriage to the rotating member by pinching the plural head stack assemblies and the carriage with the fixing member while the plural head stack assemblies and the carriage are stacked.

According to the second mode, the two projecting portions of the fixing member partially support the two places in the radial direction of the upper most head gimbal assembly coupled to the carriage. Therefore, the effect of parallelism of the plane of the fixing member may be eliminated, and the tilt of the head gimbal assembly along the shape of the supporting means may be prevented. Accordingly, the height position of the head gimbal assembly may be stabilized.

According to embodiments of the present invention, there may be provided a rotational disc type storage device having the structure that may enhance the precision of the relative positional relationship between the head gimbal assembly and the rotational disc type storage medium when the head stack assembly is installed in the rotational disc type storage device such as the magnetic disk device or the like.

Certain modes for carrying out a rotational disc type storage device according to embodiments of the present invention will be described hereunder with reference to the drawings.FIG. 1is an exemplary diagram showing a head stack assembly as a main portion of a magnetic disk device according to a first embodiment of the present invention, (A) is a side view, (B) is a perspective view of a pivot cartridge, and (C) is a plan view of the pivot cartridge.FIG. 2is an exemplary plan view showing the schematic construction of the magnetic disk device according to embodiments of the present invention.FIG. 3is a detailed diagram showing a head stack assembly.FIGS. 4(A), (B) are exemplary partial cross-sectional views showing an embodiment of a flange of a pivot cartridge.

In a magnetic disk device as a rotational disc type storage device according to a mode for carrying out the present invention, as shown inFIG. 2, a disc type magnetic disk3as a rotational disc type storage medium, and a head stack assembly4are accommodated in a disk enclosure2having a space defined by a base2A and a cover (not shown) for covering the upper portion of the base2A. A flexible cable5and an external connecting terminal6mounted on the flexible cable5are installed in the base2A, and the external connecting terminal6is connected to a control circuit board (not shown) provided at the outside of the disk enclosure2.

The magnetic disk3has a recording face3aoccupying a major portion at the center for recording data, and a non-recording face3bunused for data recording in the neighborhood of the outer periphery of the recording face, the recording face3aand the non-recording face3bbeing provided on both the adverse and back surfaces. The magnetic disc3as described above is disposed in parallel to the bottom surface of a base2A and fixed to a rotor portion of a spindle motor (not shown) provided to the base2A by screws, and it is rotated around the spindle shaft7by the spindle motor.

As shown inFIG. 1(A),FIG. 2,FIG. 3, the head stack assembly4comprises two head gimbal assemblies10A,10B and one carriage11. The first head gimbal assembly10A is mounted to the upper fixing face11aof the carriage11, and the second head gimbal assembly10B is mounted to the lower fixing face11bof the carriage11. The magnetic disk3is disposed between the head gimbal assembly10A and the head gimbal assembly10B.

Each of the head gimbal assemblies10A,10B comprises a suspension load beam13having a tip portion to which the slider12is fixed, and a mount plate14to which the suspension load beam13is linked and fixed.

A magnetic head (not shown) for reading data from the magnetic disk3is coupled to the tip of the slider12fixed to the tip portion of the suspension load beam13. The slider12to which the magnetic head is coupled is provided to each of the suspension load beams13in connection with both the surfaces of the magnetic disk3. The magnetic head as described above may interactively convert an electrical signal and a magnetic signal to each other, and read/write data from/into the magnetic disk3. The magnetic head may be comprise only a reading magnetic head that does not write data into a data area3aof the magnetic disk3, but reads out a recorded magnetic signal and converts it to an electrical signal to reproduce information. Furthermore, the slider12has an air bearing (ABS) surface formed on the bottom surface thereof, and air flows occurring at the surface of the rotating magnetic disk3impinges against the air bearing surface, whereby buoyant force is applied to the slider12. Accordingly, the slider flies from the surface of the magnetic disk with keeping a slight gap and located at a predetermined position. As described above, the positional relationship between the recording face of the magnetic disk3and the head gimbal assembly10A,10B on which the slider12is mounted is required to be rigorously managed, however, the head gimbal assemblies10A,10B are supported as constituent elements separate from the base2A, so that each head gimbal assembly is manufactured and assembled within the tolerance range thereof.

Furthermore, the suspension load beam13is provided while a tab13aprojects from the tip portion thereof, and the tab13ais held by a ramp8(seeFIG. 2) which is coupled to in the neighborhood of the outside of the magnetic disk3on the base2A. The ramp8is a constituent element used in a load/unload system which is one technique for supplying an evacuation place on the slider12when the rotation of the magnetic disk3is stopped, and it is disclosed in Japanese Patent Publication No. 10-302421, for example.

A fixing portion14ais provided at the rear end portion of the mount plate14, and it has a pivot opening14bin which a pivot cartridge15as a pivot member for rotation around the pivot shaft9(seeFIG. 2) is inserted.

A pivot opening11cin which the pivot cartridge15is inserted is formed at the front portion of the carriage11, and a coil support11dfor holding a voice coil16is formed at the rear portion of the carriage11. Furthermore, the voice coil16is disposed in the space between upper and lower yokes20, and a voice coil magnet (not shown) comprising permanent magnet is coupled to the inside of each of the upper and lower yokes20to form a magnetic space22(seeFIG. 2).

The coil support11d, the voice coil16, the voice coil magnet, and the upper and lower yokes20constitute a voice coil motor. Even when a permanent magnet exists inside only one of the yokes, the voice coil motor may be constructed.

Furthermore, the lower yoke of the upper and lower yokes20is adhesively attached to the base2A, and a pole (not shown) for supporting the upper yoke is provided to the end portion of the lower yoke.

Current flows to the voice coil16held by the coil support11dso that the head stack assembly4is forwardly and backwardly rotated with the pivot cartridge15set as the rotational center. The magnitude and direction of the current flowing in the voice coil16are controlled by a control circuit board, whereby the head stack assembly4may be driven and the sliders12may be located at predetermined positions.

In the magnetic disk device1, the head stack assembly4is moved to the outside of the magnetic disk3before the rotation of the magnetic disk3is stopped, and further the sliders12are evacuated to a slope section of the ramp8while the tab13ais slid against the ramp8.

When the head stack assembly4is turned to a predetermined position and reaches the slope section of the ramp8, the two sliders12,12are held so as to keep a fixed gap therebetween, and thus the sliders12,12are prevented from coming into contact with each other even when such impact force that the two sliders12,12are vertically accelerated is applied to the magnetic disk device1.

In order to restrict the excessively inward or outward movement of the head stack assembly4, an outside crash stop member30and an inside crash stop member31which are formed of rubber for restricting the turn range of the carriage11are provided in the base2A.

The head stack assembly4as the main part of the magnetic disk device1as described above is fixed by the pivot cartridge15, a spring washer18and a nut19while the head gimbal assembly10A, the carriage11and the head gimbal assembly10B are laminated in this order. The spring washer18is interposed between the head gimbal assembly10B and the nut19to prevent the nut19from slacking.

The pivot cartridge15has a rolling ball bearing structure in which an outer wheel15aand an inner wheel15bare provided and plural balls15care provided between both the wheels as shown in FIGS.1(B)-(C). A flange15dis formed at one end of the outer wheel15a, and a spring portion15eis formed at the other end of the outer wheel15a. As shown inFIG. 1(A),FIG. 3, the pivot cartridge15is engagedly fitted in the openings14b,11cand14bof the head gimbal assembly10A, the carriage11and the head gimbal assembly10B in this order. Accordingly, the flange15dis in contact with the mount plate14of the assembly10A, and the spring washer18is in contact with the mount plate14of the head gimbal assembly10B. The openings14b,11cand14bare formed so as to have the same inside diameter. The openings14b,11cand14bare clearance-fitted to prevent disability of insertion of the pivot cartridge15due to production tolerance.

The pivot cartridge15as described above is preferably formed of stainless steel from the viewpoint of corrosion resistance and abrasion. However, the planarization processing of the surface of the flange15dwhich is brought into contact with the mount plate serving as a laminate face of the head gimbal assembly10A is a lathe turning processing. Therefore, in the case of stainless steel, scratches, etc. are liable to occur due to processing blades and thus unevenness is liable to appear on the surface of the flange15d. Accordingly, even if parallelism of the upper fixing face11aof the carriage11is achieved, the head gimbal assembly10A is slightly warped and thus easily inclined when the head gimbal assembly10A is coupled to the carriage11and clinched by the pivot cartridge15, the spring washer18and the nut19. Furthermore, the unevenness does not necessarily appear at the same position of the surface of the flange15d, and thus the height position of the head gimbal assembly10A may be dispersed.

Therefore, the contact side150of the flange15dis designed so that a recess portion151is formed to partially support two places of the mount plate14in the cross-section in the radial direction of the flange15d. The recess portion151is designed in an annular shape having a length in the radial direction of the flange15d. By partially supporting the two places of the mount plate14in the cross-section in the radial direction of the flange15d, the influence of the unevenness appearing at the contact side150of the flange15dmay be reduced. Furthermore, the difference between the highest and lowest sites of the contact side150of the flange15dis preferably equal to 5 μm or more. The lower limit of the height difference is set to 5 μm or more in consideration of the processing roughness of the contact side150of the flange15d. The upper limit of the height difference is determined in accordance with the thickness of the flange15d. That is, the depth of the recess portion151is set so as to keep the strength of the flange15d.

The recess portion151is formed by separating two projecting portions152,153provided to the contact side150of the flange15dfrom each other at a fixed interval. The projecting portion152is formed along the outer periphery of the outer wheel15a, and the projecting portion153is formed on the further outer periphery of the projecting portion152. Accordingly, the projecting portions152,153may partially support the two places of the surrounding of the opening14bof the mount plate14of the head gimbal assembly10A and the outer periphery thereof in the cross-section in the radial direction of the flange15d. Therefore, the effect of the parallelism of the contact side150of the flange15dmay be eliminated, and also the head gimbal assembly may be prevented from being inclined along the shape of the support structure. InFIG. 3, the flange15dof the pivot cartridge15is provided with two notches in which a spanner is fitted to fix the nut19to the pivot cartridge15by a screw. The flange15dis provided with two areas of arcuate recess portions151having a predetermined length in the radial direction because the two notches are provided to the flange15d. These two areas are disposed so as to face each other in the pitch direction of the head gimbal assembly10A with the opening14bat the center therebetween.

In the cross-section in the radial direction of the flange15d, the recess portion151may be constructed between the projecting portion152and the projecting portion153by an arcuate groove. At this time, in the projecting portion152, a site which is in contact with the mount plate14of the head gimbal assembly10B may be set to a plane. By setting the contact site of the projecting portion152to a plane, the position of the mount plate14of the head gimbal assembly10B whose fitting is clearance-fitting is displaced within the range of the gap, the two places of the mount plate14in the cross-section in the radial direction of the flange15dmay be partially supported by the projecting portions152,153. At this time, the projecting portion153is formed so that the tip portion thereof has an acute angle. However, the present invention is not limited to this embodiment, and as in the case of the projecting portion152, a site which is in contact with the mount plate14of the head gimbal assembly10B may be set to a plane as shown inFIG. 4(B), and any shape may be adopted insofar as the two places of the mount plate14may be partially supported by the projecting portions152,153with no tilt of the mount plate14concerned. InFIG. 4(B), the recess portion151is constructed by a rectangular groove between the projecting portion152and the projecting portion153, however, it may be constructed by an arcuate groove as shown inFIG. 4(A).

In order to assemble the magnetic disk device1as described above, the spindle motor is installed into the base2A with which the spindle shaft7, etc. are integrally formed, and the magnetic disk3is fixed to the rotor portion of the spindle motor by a screw. Furthermore, the lower yoke to which the voice coil magnet is coupled is adhesively attached to the base2A.

The pivot cartridge15is mounted to the head gimbal assembly10A, the carriage11and the head gimbal assembly10B, and fixed to them by the spring washer18and the nut19to assemble the head stack assembly4. The head stack assembly4is engagedly fitted to the pivot shaft9by the pivot cartridge15, the carriage11is moved around the pivot shaft9and the magnetic heads coupled to the sliders12are moved to the magnetic disk3. A magnetic head side end portion of an FPC cable (not shown) is mounted on the side surface of the head stack assembly4, and a head wire from the magnetic head and a coil wire from the voice coil16of the carriage11are connected to the magnetic head side end portion. An opposite-side end portion of the FPC cable is connected to the external connecting terminal6through a connector by the flexible cable5.

Finally, the upper and lower yokes20are fixed to the predetermined positions.

As described above, after the magnetic disk3and the head stack assembly4are installed, the outside crash stop member30and the inside crash stop member31are disposed, and the lid of the base2A is coupled to, thereby completing the fabrication.

Next, the operation of the magnetic disk device1as described above will be described.

Under the operation stop state, the tabs13aof the suspension load beams13are located in the slope section of the ramp8. At this time, when the magnetic disk device1is actuated, the spindle motor is driven to rotate the magnetic disk3. Therefore, when the voice coil16is driven to rotate the head stack assembly4toward the magnetic disk, the tabs13aare separated from the ramp8while sliding against the sliding surface of the ramp8. At this time, the sliders12move to the surfaces of the magnetic disk, and air flow occurring due to the rotation of the magnetic disk3flows into the gap between the magnetic disk3and each slider12to form an air bearing. Therefore, the sliders12are floated by using the thus-formed air bearing. At this time, the circular recess portion151is formed along the planar shape of the flange15dat the contact side150of the flange15d. Therefore, in the cross-section in the radial direction of the flange15d, the two places of the surrounding of the opening14bof the mount plate14of the head gimbal assembly10A and the outer periphery thereof may be partially supported. Accordingly, the effect of the parallelism of the contact side150of the flange15dmay be eliminated, and also the head gimbal assembly10A may be prevented from being inclined along the shape of the support structure of the contact side150of the flange15d. Therefore, the parallelism of the head gimbal assemblies10A,10B, particularly, the parallelism in the pitch direction may be maintained.

In order to stop the operation, the voice coil motor is driven to rotate the head stack assembly4toward the ramp until the head stack assembly4reaches the slope section of the ramp8.

The height positions of the head gimbal assemblies of the head stack assembly used for the thus-constructed magnetic disk device according to the present embodiment and the head stack assembly used for the conventional magnetic disk device were measured for comparison.

As the head stack assemblies used for this measurement were used head stack assemblies used for a 1-type magnetic disk device in which a magnetic disk was disposed between two head gimbal assemblies. In a conventional head stack assembly400shown inFIG. 6, the contact surface of a flange403of a pivot cartridge402was subjected to no processing, however, the end portion of the flange403was subjected to chamfering.

A measuring device is a test stand50for three-dimensional dimension measurement as shown inFIG. 5. The test stand50is adjusted in level so that the axial direction of the pivot cartridge15of the head stack assembly4is set to the vertical direction. After the head stack assembly4is set up on the test stand50, the dimension H10, H20between the reference plane50aof the test stand50and each of plural measurement points50b,50crequired to check the parallelism of each of the head gimbal assemblies10A,10B of the head stack assembly4was measured to check the parallelism in the pitch direction of each of the head gimbal assemblies10A,10B. A laser measuring device was used as a measuring instrument.

FIG. 6, andFIGS. 7(A) and 7(B)show the height position of the head gimbal assembly. The abscissa axis represents the distance (mm) from the rotational center of the pivot cartridge in the pitch direction of the head gimbal assembly, and the ordinate axis represents the height position (μm) of the head gimbal assembly. The zero point of the ordinate axis represents a nominal value. 10 sets were measured for the conventional head stack assembly400, and 5 sets were measured for the head stack assembly4of the present embodiment.

A graph shown inFIG. 6is a measurement result of the head gimbal assembly located above the magnetic disk. Comparing this measurement result, it has been confirmed that the head gimbal assembly10A of the head stack assembly4according to this embodiment may suppress the dispersion of the height position more remarkably than the head gimbal assembly401A of the conventional head stack assembly400by partially supporting the two places of the surrounding of the opening14bof the mount plate14of the head gimbal assembly10A and the outer periphery thereof in the cross-section in the radial direction of the flange15dby the projecting portions152,153formed on the flange15dof the pivot cartridge15. Furthermore, the head gimbal assembly10A of the head stack assembly4of the present embodiment may be prevented from being tilted along the shape of the support structure by the two-point supporting of the projecting portions152,153of the flange15dof the pivot cartridge15. Accordingly, the tilt of the head gimbal assembly10A may be reduced over the longitudinal direction of the head gimbal assembly10A of the present embodiment, and thus it has been also found in the graph shown inFIG. 6that the displacement of the height position in the head gimbal assembly10A of the present embodiment is smaller than the conventional head gimbal assembly401A because the measurement points are totally nearer to the nominal value.

Furthermore, in the graph ofFIG. 6, the height position of the conventional head gimbal assembly401A concentrates on the plus direction because the lathe turning processing of the contact face of the flange403of the pivot cartridge402on which the head gimbal assembly401A is laminated is more easily performed in the direction concerned. On the other hand, the height position of the head gimbal assembly10A of the present embodiment concentrates on the minus direction conversely to the conventional head gimbal assembly401A because the projecting portion153formed on the flange15dof the pivot cartridge15projects more than the projecting portion152. When the projecting portion is formed in a circular shape at one place along the planar shape of the flange403on the contact face of the flange403of the pivot cartridge402used in the conventional head stack assembly400, the head gimbal assembly401A cannot be stably supported. Accordingly, the height position of the head gimbal assembly401A is dispersed or the displacement of the height position is remarkable.

A graph ofFIG. 7(A)shows a measurement result of the head gimbal assembly401B located at the lower side of the magnetic disk of the conventional head stack assembly400shown inFIG. 6. A graph ofFIG. 7(B)is a measurement result of the head gimbal assembly10B located at the lower side of the magnetic disk of the head stack assembly4of the present embodiment shown inFIG. 6. Comparing these measurement results, as in the case of the measurement result ofFIG. 6, it has been confirmed that the head gimbal assembly10B of the head stack assembly4of the present embodiment may more greatly suppress the dispersion of the height position than the head gimbal assembly401B of the conventional head stack assembly400by partially supporting the two places of the surrounding of the opening14bof the mount plate14of the head gimbal assembly10B and the outer periphery thereof in the cross-section in the radial direction of the flange15dby the projecting portions152,153formed on the flange15dof the pivot cartridge15. Furthermore, the head gimbal assembly10B of the head stack assembly4of the present embodiment may be prevented from being tilted along the shape of the support structure by the two-point supporting of the projecting portions152,153of the flange15dof the pivot cartridge15. Accordingly, the tilt of the head gimbal assembly10B may be reduced over the longitudinal direction of the head gimbal assembly10B of the present embodiment, and thus it has been also found in the graph shown inFIGS. 7(A) and 7(B)that the displacement of the height position in the head gimbal assembly10B of the present embodiment is smaller than the conventional head gimbal assembly401B because the measurement points are totally nearer to the nominal value. The difference of the measurement results ofFIGS. 7(A) and 7(B)is smaller as compared withFIG. 6because the carriage is formed of plastic resin. That is, the lower head gimbal assembly is stacked on the upper head gimbal assembly through the plastic resin carriage, and fixed to the pivot cartridge, and thus the dispersion of the height position of the head gimbal assembly disposed at the lower side is embedded in the dispersion of the contraction percentage of plastic resin.

In the magnetic disk device1according to an embodiment for carrying out the invention described above, the flange15dis formed in the pivot cartridge15, however, the present invention is not limited to this embodiment. The flange15dmay be detachably fixed to the pivot cartridge15.

In the magnetic disk device1according to a mode for carrying out the invention described above, the two head gimbal assemblies are mounted on one carriage in the head stack assembly. However, the present invention is not limited to this embodiment. One head gimbal assembly may be coupled to only one fixing face of the carriage, or another head gimbal assembly10C may be laminated through a spacer33on the head gimbal assembly10A mounted on the carriage11as shown inFIG. 3. Accordingly, plural head gimbal assemblies and spacers may be alternately stacked on the fixing face of the carriage, and thus the present invention may be adapted to a magnetic disk device in which plural magnetic disks are stacked. However, the greatest effect according to embodiments of the present invention may be achieved by the magnetic disk device1including one magnetic disk3described above.

In the head stack assembly4of the above-described embodiment, the nut19is used because the head gimbal assembly10A, the carriage11and the head gimbal assembly10B are fixed to the pivot cartridge15while the head gimbal assembly10A, the carriage11and the head gimbal assembly10B are stacked. However, the present invention is not limited to this embodiment, and they may be fixed by using an adhesive agent. Furthermore, a female screw hole is formed from the side surface of the carriage11so as to extend to the pivot opening11c, and a locking screw such as a hexagon socket locking screw or a slotted locking screw is screwed into the female screw hole to fix the head gimbal assembly10A, the carriage11and the head gimbal assembly10B to the pivot cartridge15while the head gimbal assembly10A, the carriage11and the head gimbal assembly10B are stacked.

The above-described embodiment has been described by using the load/unload type magnetic disk device, however, the present invention is not limited to this embodiment. The present invention may be applied to a CSS (Contact Start Stop) type magnetic disk device in which the magnetic disk has an evacuation area, and the head stack assembly evacuates a slider having a magnetic head coupled thereto to the evacuation area through a head gimbal assembly.

The present invention has been described by using the specific embodiment shown in the figures. However, it is needless to say that the present invention is not limited to these embodiments shown in the drawings, and any well-known construction may be adopted insofar as the effect of the present invention may be achieved.