Patent Application
20080158724
The field of the present invention relates to disk drive data storage devices. More particularly, embodiments of the present invention are related to altitude sensitivity and reduced drive speed sensitivity of a disk drive.
Disk drives used in small electronic devices such as laptops, MP3 players, GPS, PDA devices and other devices are “mobile drives.” Slider air bearing is a key component of these “mobile drives.” Some of the requirements of these “mobile drives” include “low altitude sensitivity” and “high operational shock” performances.
The low altitude sensitivity means that the slider air bearing has a small fly height (FH) loss at a higher altitude (such as 3000 meters) compared to the FH at sea level. The requirement for a small FH loss becomes more important for current drives with sub 10 nanometer FH. The high operational shock requirement means that the slider air bearing would not collapse and the slider/disk interface damage would not occur during operating state when the drive experiences a very high acceleration such as impact, free drop, etc. The highest acceleration value without the interface damage is called the “op-shock” boundary. Current specification for the op-shock boundary is approximately 200 G and 2 ms duration, however, the specification is getting higher, such as 400 G/2 ms.
To reduce FH loss, a low base recess (low depth etch) or a dimple forward slider is used. However, a low base recess reduces op-shock performance and the dimple forward design degrades the op-shock also. A deeper base recess increases op-shock performance, however, the FH loss suffers drastically. The requirements of high op-shock and low FH loss are at conflict. Conventionally, FH loss has been minimized at the expense of high op-shock degradation.
Embodiments of the present invention include a head slider for a magnetic disk drive. In one embodiment of the invention, the head slider includes a leading edge, a trailing edge, an inner diameter side and an outer diameter side of an air bearing surface. The head slider further includes a first recess on the air bearing surface of the head slider, a second recess on the air bearing surface of the head slider wherein the second recess is deeper than the first recess and a third recess on the air bearing surface of the head slider wherein the third recess is deeper than the second recess and is disposed within the second recess, forming a first pocket.
The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention:
Reference will now be made in detail to the alternative embodiment(s) of the present invention, a slider air bearing for hard disk drives. While the invention will be described in conjunction with the alternative embodiment(s), it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
With reference now to
In the embodiment shown, each arm 125 has extending from it at least one cantilevered load beam and suspension 127. A magnetic read/write transducer or head is mounted on a slider 129 and secured to a flexure that is flexibly mounted to each suspension 127. The read/write heads magnetically read data from and/or magnetically write data to disk 115. The level of integration called the head gimbal assembly (HGA) is head and the slider 129, which are mounted on suspension 127. The slider 129 is usually bonded to the end of suspension 127. The head is typically pico size (approximately 1160×1000×300 microns) and formed from ceramic or intermetallic materials. The head also may be of “femto” size (approximately 850×700×230 microns) and is pre-loaded against the surface of disk 115 (in the range two to ten grams) by suspension 127.
Suspensions 127 have a spring-like quality, which biases or urges the air-bearing surface of the slider 129 against the disk 115 to cause the slider 129 to fly at a precise distance from the disk. A voice coil 133 free to move within a conventional voice coil motor magnet assembly 134 (top pole not shown) is also mounted to arms 125 opposite the head gimbal assemblies. Movement of the actuator 121 (indicated by arrow 135) by controller 119 moves the head gimbal assemblies along radial arcs across tracks on the disk 115 until the heads settle on their respective target tracks. The head gimbal assemblies operate in a conventional manner and always move in unison with one another, unless drive 111 uses multiple independent actuators (not shown) wherein the arms can move independently of one another.
Referring still to
In the embodiment shown, the bypass channel 150 is located between an outer perimeter 116 of the housing 113 and the actuator 121, such that the bypass channel 150 completely circumscribes the actuator 121. Bypass channel 150 further comprises a first opening 151 proximate to upstream side wherein air is conveyed away from the disks 115 and a second opening 152 proximate to downstream side wherein airflow 160 is directed toward the disks 115.
As shown in
Alternatively, or operating in conjunction with the diffuser 153, another embodiment of the drive 111 may include a contraction 154 (e.g., a Venturi). The contraction 154 is also located in the bypass channel 150, but is adjacent to the downstream side of the disk pack or disks 115. Like the diffuser 153, the contraction 154 is typically offset downstream from the disks 115, but in a radial direction 143. Each of the diffuser 153 and the contraction 154 may be spaced apart from the outer edges of the disks 115 in radial directions 142, 143 by, for example, approximately 0.5 mm. The contraction 154 may be provided for re-accelerating bypass airflow 160 to provide efficient energy conversion for the air flow from pressure energy to kinetic energy prior to merging bypass airflow 160 with air flow 141 around the disks 115.
The use of bypass channel 150 has several advantages, including the ability to reduce aerodynamic buffeting of actuator 121 during the servo writing process and/or during normal operation of disk drive system 111. More specifically, bypass channel 150 reduces the pressure build-up on the upstream side of actuator 121 which occurs when drive 111 is operated. Additionally, directing airflow 160 around the actuator 121 decreases the upstream pressure on the actuator, thus reducing force acting on the actuator 121 while reducing the energy of the bluff-body wake of the actuator arm.
In embodiments of the present invention, disk drive system 111 may be filled with a gas (e.g., helium) rather than ambient air. This may be advantageous in that helium is a lighter gas than ambient air and causes less buffeting of actuator 121 when disk drive system 111 is in operation. In embodiments of the present invention, disk drive 111 may be sealed after the servo writing process to keep the helium in the drive. Alternatively, the helium may be removed from disk drive 111 and ambient air is allowed to return into the disk drive prior to sealing first opening 151 and second opening 152.
To improve magnetic head positioning accuracy, it is necessary to write servo information with lower rotational speed than steady state speed. Embodiments of the present invention include an air bearing surface (ABS) design which is insensitive to rotational speed and altitude simultaneously.
Embodiments of the present invention use multiple etch depths on the air bearing surface of a disk drive slider to improve fly height loss at high altitudes and/or reduced operating speeds, especially while writing servo tracks. More particularly, embodiments of the present invention include a disk drive slider with a pocket close to the leading edge of the slider. Embodiments of the present invention are directed towards disk drives for use in portable electronic devices, however, the present invention is well suited to any disk drive system.
In one embodiment of the invention, the first recess comprises two separate recesses, one near the leading edge 210 and one near the trailing edge 220. In this embodiment of the invention, multiple portions of the first recess may be of differing sizes. However, the different portions of the first recess are of the same depth with respect to the air bearing surfaces 202.
In one embodiment of the invention, the slider 200 further includes a second recess 206. In one embodiment of the invention, the second recess 206 is deeper than the first recess 204. In one embodiment of the invention, the second recess 206 creates a negative pressure region on the air bearing side of the slider 200 when the slider is in operation.
In one embodiment of the invention, the slider 200 further includes a third recess 208. In one embodiment of the invention, the third recess 208 is deeper than the second recess 206. In one embodiment of the invention, the third recess 208 is disposed within the area defining the second recess 206. In other words, the third recess 208 defines a pocket within the region of the second recess 206. In one embodiment of the invention, the third recess 208 is located closer to the leading edge 210 than the trailing edge 220 of the slider 200.
In one embodiment of the invention, the third recess 208 is at least one micron deeper than the second recess 206. In another embodiment of the invention, the third recess is at least 2.5 microns deep with respect to the air bearing surface 202. In other embodiments of the present invention, the third recess 208 is at least twice the depth as the second recess 206.
In one embodiment of the invention, the first recess 204 is approximately 0.14 microns deep with respect to the ABS 202, the second recess 206 is approximately 0.7 microns deep with respect to the ABS 202 and the third recess 208 is approximately 2.7 microns deep with respect to the ABS 202. It is appreciated that the above mentioned depths are exemplary and are intended as an example slider configuration in accordance with embodiments of the present invention.
The foregoing descriptions of specific embodiments of the present invention have presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and it's practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
