Patent Application
20090154023
The example embodiments herein relate to information recording disk drive devices, and, more particularly, to a locking apparatus that uses electromagnetic damping within a disk drive device to lock an actuator, thereby preventing a head stack assembly movable by the actuator from moving.
One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the media to selectively read from or write to the disk.
The arm 146, which is installed on a base plate (not show) of the disk drive unit, rotates around a pivot hole 148 formed in the middle of the arm. The VCM includes a coil 156 that is coupled with the other end of the arm 146. The elements may be collectively referred to a head stack assembly (HSA). A lower yoke 151 is installed under the coil 156, with the lower yoke 151 being fixed to the base plate of the disk drive unit and spaced a predetermined distance apart from the coil 156. An upper yoke 152 is installed above the coil 156, while a magnet 154 is attached to the bottom surface thereof. In an alternative arrangement, the magnet 154 also may be attached to a top surface of the lower yoke 151.
The VCM is controlled by a servo control system (not shown), which rotates the slider 105 of the actuator from the parking zone to the data zone when the disk drive unit is turned on, and rotates the head (attached to the slider 105) from the data zone to the parking zone when the disk drive unit is turned off.
In a conventional hard disk drive during reading/writing, a lifting force caused by the rotation of the disk 101 and an elastic force generated by the HGA 102 lift the slider 105 to a height at which the lifting force and the elastic force balance each other. Thus, the magnetic head mounted on slider 105 is maintained at a constant distance from the disk 101. When the hard disk drive is turned off and the rotation of the disk 101 stops, however, the lifting force diminishes. Thus, one or more of the following parts may become damaged if the head stack assembly is left in the data zone position or is free to move about: the disk 101, the slider 105, the magnetic head mounted on the slider 105, etc.
One conventional approach to preventing such damage is to move the slider 105 to the parking zone and lock it there. Locking apparatuses may prevent rotations caused by external shocks or vibrations, which could damage the above-mentioned components, by generally preventing a head from escaping from the parking zone and moving to the data zone. The interaction between the current input into the coil 156 and the magnetic field formed by the magnet 154 allows the head to be controlled by the servo through the VCM.
Certain locking apparatuses shown in the enlarged portion of
While such arrangements were improvements over previous techniques, they still suffer several disadvantages. For example, the damping member 164 is an actual, physical element in a hard disk drive, requiring its own complete structure. Thus, the manufacturing and installation costs associated with such mechanisms are comparatively expensive. Another disadvantage relates to the actual process of crash-stopping into the physical damping member 164. Specifically, damping members require physical contact. This additional physical contact may cause additional stresses and/or vibrations. Additional stresses and/or vibrations may, in turn, cause HGA vibration and/or contact with the disk, resulting in damage to the head, disk, etc.
Thus, it will be appreciated that there is a need for an improved system that does not suffer from one or more of the above-mentioned drawbacks.
One aspect of the present invention relates to an electromagnetic damping apparatus for locking an actuator for a head stack assembly including at least one read/write head thereon. In certain example embodiments, the electromagnetic damping apparatus may comprise a magnetic element and a metal element that cooperate in response to an electromagnetic field created by a current to lock the actuator in a predetermined position. One of said magnetic element and said metal element may be fixed, and the other one may be movable by said actuator. The damping apparatus may be operable to selectively apply the current to lock the actuator by preventing the magnetic element and the metal element from moving apart. The current applied preferably will be an eddy current.
In certain example embodiments, the magnetic element will have a magnetic polarization of either north or south. The magnetic element may be located on the head stack assembly, and the metal element may be located behind the magnetic element but not on the head stack assembly. In such embodiments, the metal element may be V-shaped, and the predetermined position may be a position where a center axis of the head stack assembly is aligned with one edge of the metal element.
In certain other example embodiments, the metal element may be located on the head stack assembly, and the magnetic element may be located behind the metal element but not on the head stack assembly. In such embodiments, the magnetic element may be V-shaped, and the predetermined position may be a position where a center axis of the head stack assembly is aligned with one edge of the magnetic element.
Another aspect of the present invention relates to a disk drive device. Certain example embodiments may comprise a head stack assembly including a head gimbal assembly having a slider with a read/write head thereon and a drive arm connected to the head gimbal assembly. A disk operable to be read from and/or written to by said read/write head and a spindle motor operable to spin the disk also may be included. Additionally, an electromagnetic damping apparatus for locking an actuator for the head stack assembly may be included. The electromagnetic damping apparatus may further comprise a magnetic element and a metal element that cooperate in response to an electromagnetic field created by a current to lock the actuator in a predetermined position. One of said magnetic element and said metal element may be fixed and the other one may be movable by the actuator. The damping apparatus may be operable to selectively apply the current to lock the actuator by preventing the magnetic element and the metal element from moving apart. The current applied preferably will be an eddy current.
In certain example embodiments, the electromagnetic damping apparatus may be further operable to cause the actuator to move the head stack assembly from a data zone position corresponding to a position where the read/write head can read data from and/or write data to the disk, to the predetermined position. The predetermined position may be a parking zone where the read/write head cannot read data from and/or write data to the disk.
Other aspects, features, and advantages of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of this invention.
The accompanying drawings facilitate an understanding of the various embodiments of this invention. In such drawings:
Certain example embodiments use magnetic fields to achieve damping, thus eliminating the need for physical damping devices required by conventional locking apparatuses. According to certain example embodiments, damping devices may comprise a metal element and one or more magnetic elements. For example, either the magnetic element or the metal element may be installed at the end of the coil of the VCM, depending on the particular embodiment. Other alternative arrangements, potentially comprising multiple magnetic and/or metal elements are possible, such as, for example, locating metal or magnetic elements on either side of the coil rather than simply at its end. Regardless of the specific embodiment chosen, an electromagnetic damping preferably occurs. This damping prevents the movement of the particular element (either the metal element or the magnetic element, depending on the particular example embodiment) located at the end of the coil of the VCM. Thus, according to certain example embodiments, damping occurs without a physical locking apparatus that requires a crash-stop.
A preferred embodiment may use an eddy current to create an electromagnetic field to perform the damping. Eddy currents may retard motion or cause deceleration within a moving system. An eddy current occurs when a moving magnetic field intersects a conductor, or vice-versa. The relative motion causes a circulating flow of electrons, or current, within the conductor. These circulating eddies of current create electromagnets with magnetic fields that oppose the change in the external magnetic field. In general, the stronger the magnetic field (or the greater the electrical conductivity of the conductor), the greater the currents developed, and thus the greater the opposing force. Resistance within the conductor may cause a dragging effect, which can be used in braking and damping. These techniques are advantageous because, for example, they have substantially no mechanical wear and are capable of producing very precise damping forces. Unlike conventional brakes (which cause friction between moving parts) and conventional damping parts within a hard disk drive (which require physical contact in the form of a crash-stop), kinetic energy may be converted to heat without contact between the moving parts by using eddy current damping techniques.
Referring now more particularly to the accompanying drawings in which like reference numerals indicate like parts throughout the several views,
A metal element 312 is installed in the base 301. Preferably, the metal element 312 is V-shaped and faces the magnetic element 310. The V-shaped metal element 312 may include two parts 312a-b which face the magnetic element 310 when the head is in the data zone and in the landing zone. It will be appreciated that other shapes may be used instead of the V-shape.
Similarly, when the head begins reading data from or writing data to the disk, the head may move towards to the data zone 317. Eddy current damping may occur before the outer track is reached, but the magnetic force between the magnetic element 310 and the metal 312b should be smaller than the VCM moving force generated by the magnetic element 309. The eddy currents may have no (or substantially no) effect on the head when moving form track to track, whereas the electromagnetic damping may continue to increase and achieve the greatest damping effect when moving the head to the outer track of the data zone 317. Also, when the magnetic element 310 faces the part 312a of the metal element 312, the eddy current damping may lock the VCM and prevent the head from moving.
A magnetic element 322 is installed in the base 301. Preferably, the magnetic element 322 is V-shaped and faces the metal element 320. The V-shaped magnetic element 322 may include two parts 322a-b (shown in
A magnetic element 322 with a polarization of magnetic north extends is located on the behind the HSA. When the VCM moves the head from data zone to the landing zone (e.g. when the hard disk drive is turned off), the metal element 320 will move and face part 322b of the magnetic element 322 located at the base of the hard disk drive. Electromagnetic damping between the part 322b of the magnetic element 322 and the metal element 320 will happen, which will quick-stop the end of the HSA 305 having the metal element 320 while also locking the HSA 305 in place.
Similarly, when the head begins reading data from or writing data to the disk, the head may move towards to the data zone 317. Eddy current damping may occur before the outer track is reached, but the magnetic force between the metal element 320 and the part 322b of the magnetic element 322 should be smaller than the VCM moving force generated by the magnetic element 309. The eddy currents may have no (or substantially no) effect on the head when moving form track to track, whereas the electromagnetic damping may continue to increase and achieve the greatest damping effect when moving the head to the outer track of the data zone 317. Also, when the metal element 320 faces the part 322a of the magnetic element 322, the eddy current damping may lock the VCM and prevent the head from moving.
As noted above, the HSA 305 is support by the bearing 304 located in its middle region. The HSA 305 supports the magnetic head and positions in either in the landing zone 315 or the data zone 317. When the power of the hard disk drive is turned off, the head stays in the landing zone 315, while the metal element 320 faces part 322b of the magnetic element 322. For example, the edge of part 322b of the magnetic element 322 may be aligned with a center axis of the HSA 305. Similarly, when the head is in the data zone 317, the metal element 320 will face the magnetic element 322a. For example, the edge of part 322a of the magnetic element 322 may be aligned with a center axis of vertical with the axis of the HSA 305.
While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.
