Apparatus for and method of measuring motion characteristics of head gimbal assembly

An apparatus correctly measures motion characteristics a head gimbal assembly exhibits when turned in a radial direction of a hard disk. The apparatus includes an assembly support to fixedly support the head gimbal assembly on a center axis that corresponds to a rotation axis around which the head gimbal assembly is turned in actual use, a disk drive to rotatably support the hard disk and turn around a turn axis that is concentric with the center axis on which the head gimbal assembly is fixedly supported, and a turn unit to turn the disk drive around the turn axis, thereby creating a relative turn of the head gimbal assembly with respect to the hard disk.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for and a method of measuring motion characteristics of a head gimbal assembly incorporated in a hard disk drive (HDD) of an information processing unit such as a computer.

2. Description of Related Art

A hard disk drive includes a hard disk and a head gimbal assembly including a head suspension, a flexure, a slider and the like. When the hard disk is rotated at high speed, the slider of the head gimbal assembly slightly floats from the surface of the hard disk and a transducer incorporated in the slider writes and reads data to and from the hard disk.

The hard disk drive usually employs a load/unload mechanism to load the slider onto tracks of the hard disk when the hard disk is rotated and unload the slider out of the tracks when the hard disk is stopped.

The load/unload mechanism employs a ramp block made of resin and arranged in the vicinity of the periphery of the hard disk. When the hard disk is stopped, the head gimbal assembly is retracted onto the ramp block. At this time, a tab formed on a front end of the head suspension of the head gimbal assembly is guided along a slope of the ramp block, to move the slider away from the hard disk and prevent the slider from contacting the hard disk during the stoppage of the hard disk.

When the tab is guided along the slope of the ramp block, friction between the tab and the ramp block may grind the ramp block to produce fine matter that may badly affect the hard disk. The hard disk is also vulnerable to unexpected behavior of the slider that may occur during the load/unload movement.

The head gimbal assembly is driven by a voice coil motor (VCM) when achieving the load/unload movement, or when moved from a track to another track on the hard disk, or when following a track on the hard disk. To correctly achieve these tasks, motion characteristics the head gimbal assembly exhibits during a turn thereof in a radial direction of the hard disk must be correctly measured and optimized.

For this, there is a need of an apparatus for easily measuring the motion characteristics of a head gimbal assembly.

Apparatuses for measuring the motion characteristics of a head gimbal assembly frequently employ high-speed cameras or laser Doppler velocimeters to observe the behavior of a slider of the head gimbal assembly during a load/unload motion or a track-to-track movement. This type of apparatus is disclosed in, for example, Japanese Unexamined Patent Application Publications No. H11-96527 and No. 2006-244582. These related arts are limited in the correctness of measured data because they obtain the data by turning a head gimbal assembly in a radial direction of a hard disk.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an apparatus for and a method of measuring motion characteristics of a head gimbal assembly, capable of correctly obtaining data on the motion characteristics of the head gimbal assembly.

In order to accomplish the object, an aspect of the present invention provides an apparatus for measuring motion characteristics a head gimbal assembly exhibits when turned in a radial direction of a hard disk. The apparatus includes an assembly support configured to fixedly support the head gimbal assembly on a center axis that corresponds to a rotation axis around which the head gimbal assembly is turned in actual use; a disk drive configured to rotatably support the hard disk and turn around a turn axis that is concentric with the center axis on which the head gimbal assembly is fixedly supported; and a turn unit configured to turn the disk drive around the turn axis, thereby creating a relative turn of the head gimbal assembly with respect to the hard disk.

This aspect of the present invention obtains data on motion characteristics a head gimbal assembly exhibits when turned in a radial direction of a hard disk without turning the head gimbal assembly in the radial direction of the hard disk.

This aspect may employ a high-speed camera to photograph a slider area of the head gimbal assembly, to obtain data on motion characteristics of the head gimbal assembly. The aspect allows the camera to easily focus on the slider area and obtain correct data on movements of the slider.

DETAILED DESCRIPTION OF EMBODIMENTS

An apparatus for measuring motion characteristics of a head gimbal assembly according to an embodiment of the present invention will be explained. The apparatus correctly obtains data on the motion characteristics of a head gimbal assembly by turning a disk drive around a center axis that corresponds to a rotation axis of the head gimbal assembly in actual use to create a relative turn of the head gimbal assembly with respect to a hard disk.

FIG. 1is a block diagram illustrating the apparatus for measuring the motion characteristics of a head gimbal assembly according to an embodiment of the present invention,FIG. 2is a perspective view illustrating the apparatus, andFIG. 3is a perspective view illustrating a turning operation of a disk drive carried out by the apparatus.

The apparatus1illustrated inFIG. 1obtains data on motion characteristics a head gimbal assembly3exhibits when turned in a radial direction of a hard disk7. The head gimbal assembly3includes a slider5that incorporates a transducer to write and read data to and from the hard disk7as well as a head suspension and the like.

The apparatus1has an assembly support9, a disk drive11, and a turn unit13.

The assembly support9fixedly supports the head gimbal assembly3on a center axis that corresponds to a rotation axis around which the head gimbal assembly3is turned in actual use. The assembly support9includes an upper beam19, a torquemeter17, and a fixed shaft15.

In an actual hard disk drive, the head gimbal assembly3is turned by, for example, a voice coil motor around a center axis of the voice coil motor. The center axis on which the assembly support9fixedly supports the head gimbal assembly3corresponds to the center axis of the voice coil motor.

InFIG. 2, the head gimbal assembly3is fixed to the fixed shaft15of the assembly support9. An axial center of the fixed shaft15is the center axis on which the assembly support9fixedly supports the head gimbal assembly3and corresponds to the center axis of the voice coil motor.

The fixed shaft15is joined with the torquemeter17of the assembly support9. The torque meter17is a data monitor to measure torque around the center axis acting on the head gimbal assembly3. The measured torque is data representative of the motion characteristics of the head gimbal assembly3. Namely, the torquemeter17is a data monitor that gathers motion characteristic data acting on the fixed shaft15as torque acting around the center axis of the voice coil motor at the time of turning the head gimbal assembly3to load/unload the slider5to and from the hard disk7in actual use.

The torquemeter17is attached to the upper beam19extending from a base frame21.

The disk drive11is configured like a hard disk drive, to support and drive the hard disk7with a motor. The disk drive11is supported to turn around a turn axis that is concentric with the axial center of the fixed shaft15.

The disk drive11has a ramp block23made of synthetic resin. The ramp block23is positioned adjacent to the periphery of the hard disk7, so that a tab3a(FIG. 11) of the head gimbal assembly3formed in the vicinity of the slider5may run on the ramp block23and be guided along a slope of the ramp block23when the slider5is loaded and unloaded to and from the hard disk7. The disk drive11may exclusively be prepared, or may be one actually used in a hard disk drive. In the latter case, a head gimbal assembly is removed from the hard disk drive and other parts of the hard disk drive including a hard disk, a driving system, and a ramp block are left as they are on the hard disk drive so that the hard disk drive is used as the disk drive11.

The disk drive11is supported by a turn shaft25that is concentric with the fixed shaft15and is coupled with the turn unit13(FIG. 1).

The turn unit13drives the turn shaft25so that the disk drive11turns around the center of the turn shaft25, i.e., the center of the fixed shaft15that corresponds to the rotation axis around which the head gimbal assembly3is turned in actual use. This operation creates a relative turn of the slider5of the head gimbal assembly3in a radial direction with respect to the hard disk7. The turn unit13includes a motor, a reduction gear, and the like.

When the turn unit13turns or sways the disk drive11in directions indicated with arrows inFIG. 2, the disk drive11turns relative to the head gimbal assembly3that is stationary, as indicated with dotted lines inFIG. 3. This is equal to turning the slider5of the head gimbal assembly3in a radial direction of the hard disk7.

At this time, the ramp block23located adjacent to the periphery of the hard disk7also turns relative to the slider5of the head gimbal assembly3.

This allows a correct observation of the behavior the slider5exhibits when moved from the hard disk7onto the ramp block23, or when moved from a track to another track on the hard disk7, or when following a track on the hard disk7.

In this way, the embodiment creates a turn of the slider5, i.e., a turn of the head gimbal assembly3in a radial direction of the hard disk7by turning the hard disk7relative to the head gimbal assembly3. With this, the embodiment correctly obtains data on motion characteristics the head gimbal assembly3exhibits when guided along the slope of the ramp block23or when moved in a radial direction of the hard disk7.

The torquemeter17obtains torque acting on the head gimbal assembly3that is not turned, and therefore, the obtained torque is correct and is correctly usable as data to find a frictional force acting between the head gimbal assembly3and the ramp block23, and the like as the motion characteristics of the head gimbal assembly3.

FIG. 4is a perspective view illustrating the apparatus1ofFIG. 1provided with first and second high-speed cameras27and29serving as data monitors.

The first camera27is arranged to observe a horizontal front view of the slider5area of the head gimbal assembly3. The second camera29is arranged to observe a horizontal side view of the slider5area of the head gimbal assembly3. The cameras27and29photograph the head gimbal assembly3in a direction orthogonal to the center axis on which the assembly support9fixedly supports the head gimbal assembly3.

FIGS. 5A,5B, and6illustrate a relationship between the observation area of the first high-speed camera27and the movement of the head gimbal assembly3, in whichFIGS. 5A and 5Bare of a related art employing the camera27to observe the head gimbal assembly3andFIG. 6is of the embodiment of the present invention employing the camera27to observe the head gimbal assembly3.

The related art ofFIGS. 5A and 5Bturns the head gimbal assembly3with a voice coil motor in a radial direction of the hard disk7and observes a horizontal front view of the slider5of the head gimbal assembly3with the camera27.

According to the related art, the head gimbal assembly3is turned by the voice coil motor toward the observation area27aof the camera27as illustrated inFIGS. 5A and 5B, and therefore, the slider5and tab3aof the head gimbal assembly3horizontally move over the surface of the hard disk7. Once the tab3ais brought onto the ramp block23, the slider5and tab3ashow horizontal and vertical movements. With respect to these movements, the observation area27aof the camera27is stationary as illustrated inFIGS. 5A and 5B.

As a result, the first high-speed camera27usually employing a large magnification lens observes only part of the movements of the slider5and tab3aof the head gimbal assembly3as illustrated inFIG. 5B. Namely, the related art is unable to wholly observe the movements of the head gimbal assembly3.

On the other hand, the embodiment of the present invention illustrated inFIG. 6does not turn the head gimbal assembly3and keeps the same in the observation area27aof the first camera27during the relative turn, and therefore, easily and correctly obtains data about motion characteristics of the head gimbal assembly3for the whole turning motion thereof.

FIG. 7is a plan view illustrating a related art employing a second high-speed camera101(corresponding to the second high-speed camera29ofFIG. 4) for measuring motion characteristics of a head gimbal assembly3.

InFIG. 7, a hard disk drive has a ramp block23in the vicinity of a hard disk7and the head gimbal assembly3is loaded and unloaded between the ramp block23and the hard disk7. The camera101monitors the load/unload movement of the head gimbal assembly3.

FIGS. 8A to 8Hare views illustrating the related art ofFIG. 7, in whichFIGS. 8A,8C,8E, and8G illustrate the head gimbal assembly3observed with the camera101andFIGS. 8B,8D,8F, and8H illustrate positions of the head gimbal assembly3with respect to the hard disk7and ramp block23in the situations ofFIGS. 8A,8C,8E, and8G; respectively.FIGS. 9A and 9Bare views illustrating the embodiment of the present invention, in whichFIG. 9Aillustrates the head gimbal assembly observed with the second high-speed camera29ofFIG. 4andFIG. 9Billustrates the behavior of the head gimbal assembly3.

According to the related art ofFIG. 7, the head gimbal assembly3and the slider5thereof at each of the turn positions illustrated inFIGS. 8B,8F, and8H are defocused in the camera101as illustrated inFIGS. 8A,8E, and8G. Only at the turn position illustrated inFIG. 8D, the related art can observe a focused image of the head gimbal assembly3as illustrated inFIG. 8C.

On the other hand, the embodiment of the present invention does not turn the head gimbal assembly3during the relative turn, and therefore, there is no change in a depth of field for the second high-speed camera29as illustrated inFIG. 9B. Accordingly, the embodiment is able to observe a focused image of the slider5of the head gimbal assembly3at every turn position as illustrated inFIG. 9A.

An observing direction of the head gimbal assembly3by a high-speed camera is not limited to the front or the side of the head gimbal assembly3. Any observing direction is adoptable if it allows to obtain data on motion characteristics of the head gimbal assembly3.

FIG. 10is a perspective view illustrating the apparatus1ofFIG. 1provided with a laser Doppler velocimeter31andFIG. 11is a plan view illustrating laser irradiating positions on the slider5of the head gimbal assembly3to be observed with the apparatus1ofFIG. 10.

InFIG. 10, the laser Doppler velocimeter31serving as a data monitor emits a laser beam to the slider5and receives a reflected beam from the slider5. The emitted laser beam runs in parallel to a rotation axis around which the head gimbal assembly3is turned in actual use.

The laser Doppler velocimeter31emits a laser beam to each of four locations33,35,37, and39on the slider5and receives each reflected beam from the slider5, to thereby obtain data concerning the behavior of the slider5.

The slider5of the head gimbal assembly3that receives a laser beam from the laser Doppler velocimeter31is fixed to the fixed shaft15, although a relative turn is created between the head gimbal assembly3and the disk drive11. Accordingly, the laser Doppler velocimeter31can easily and correctly emit a laser beam to the slider5and receive a reflected beam therefrom, to obtain data about motion characteristics of the head gimbal assembly3.

The laser Doppler velocimeter31may be arranged to emit a laser beam to a side face or any other part of the slider5. Further, it may emit a laser beam to an element of the head gimbal assembly3other than the slider5, to observe the behavior of the element.

In this way, the apparatus1of the above-mentioned embodiment for measuring motion characteristics the head gimbal assembly3exhibits when turned in a radial direction of the hard disk7includes the assembly support9configured to fixedly support the head gimbal assembly3on the center axis that corresponds to the rotation axis around which the head gimbal assembly3is turned in actual use; the disk drive11configured to rotatably support the hard disk7and turn around a turn axis that is concentric with the center axis on which the head gimbal assembly3is fixedly supported; and the turn unit13configured to turn the disk drive11around the turn axis, thereby creating a relative turn of the head gimbal assembly3with respect to the hard disk7.

The apparatus1is capable of creating a situation of turning the head gimbal assembly3in a radial direction of the hard disk7without actually turning the head gimbal assembly3in the radial direction of the hard disk7. Accordingly, the apparatus1is able to easily and correctly obtain data related to the motion characteristics the head gimbal assembly3including the slider5, head suspension and the like exhibits when turned in the radial direction of the hard disk.

The apparatus1may employ the first and second high-speed cameras27and29to photograph the head gimbal assembly3and obtain data on the motion characteristics of the head gimbal assembly3including the slider5, head suspension and the like. At this time, the apparatus1is able to obtain the data on the motion characteristics indicative of the behavior of the slider5, head suspension and the like for the whole range of a turn of the head gimbal assembly3. The apparatus1causes no change in a depth of field for the second camera29. Accordingly, the second camera29is able to easily focus on the slider5, to correctly obtain the data on the motion characteristics of the head gimbal assembly3, in particular, the slider5thereof.

The apparatus1may employ the laser Doppler velocimeter31that emits a laser beam to the slider5of the head gimbal assembly3. Although the head gimbal assembly3is fixed to the fixed shaft15, the apparatus1creates a relative turn between the head gimbal assembly3and the hard disk7. Accordingly, the laser Doppler velocimeter31is allowed to correctly emit a laser beam onto the slider5and receive a reflected beam therefrom, and therefore, the apparatus1can obtain correct data on the motion characteristics of the head gimbal assembly3.

According to the embodiment, the disk drive11has the ramp block23adjacent to the periphery of the hard disk7and the tab3aformed in the vicinity of the slider5of the head gimbal assembly3is guided along a slope of the ramp block23when the head gimbal assembly3is loaded onto and unloaded from the hard disk7. Accordingly, data on motion characteristics the head gimbal assembly3including the slider5, head suspension and the like exhibits when loaded onto or unloaded from the hard disk7is easily and correctly obtainable with the use of the first and second high-speed cameras27,29, the laser Doppler velocimeter31, the torquemeter17, and the like.

Another embodiment of the present invention is a method of measuring motion characteristics the head gimbal assembly3exhibits when turned in a radial direction of the hard disk7. The method includes fixedly supporting the head gimbal assembly3on a center axis that corresponds to a rotation axis around which the head gimbal assembly3is turned in actual use; turning the disk drive11rotatably supporting the hard disk7around a turn axis that is concentric with the center axis on which the head gimbal assembly3is fixedly supported, thereby creating a relative turn of the head gimbal assembly3with respect to the hard disk7; and obtaining data related to the motion characteristics of the head gimbal assembly3.

The method is capable of creating a situation of turning the head gimbal assembly3in a radial direction of the hard disk7without actually turning the head gimbal assembly3in the radial direction of the hard disk7. Accordingly, the method is able to easily and correctly obtain data related to motion characteristics the head gimbal assembly3including the slider5, head suspension and the like exhibit when turned.

According to the method, the disk drive11has the ramp block23adjacent to the periphery of the hard disk7and the tab3aformed in the vicinity of the slider5of the head gimbal assembly3is guided along a slope of the ramp block23when the head gimbal assembly3is loaded onto and unloaded from the hard disk7. The method turns the disk drive11to create a relative movement of the head gimbal assembly3along the slope of the ramp block23and obtains data about the motion characteristics of the head gimbal assembly3. The method may employ the first and second high-speed cameras27,29, the laser Doppler velocimeter31, the torquemeter17, and the like to easily and correctly obtain data on motion characteristics the head gimbal assembly3including the slider5, head suspension and the like exhibits when loaded onto or unloaded from the hard disk7.