Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-12-10
2001-10-09
Hall, Carl E. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C360S078050
Reexamination Certificate
active
06298545
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a mechanism for positioning a transducing head in a disc drive system, and more particularly relates to a piezoelectric microactuator integrated into an actuator arm of a disc drive system to provide high resolution head positioning over a selected track of a rotatable disc.
Concentric data tracks of information are being recorded on discs with increasing track densities, which reduces the margin for error in positioning a transducing head over a selected track due to the reduced radial distance between tracks and the narrow radial width of the tracks themselves. Typical actuator motors lack sufficient resolution to accurately position a head in a system implementing a disc with a high track recording density.
Various proposals have been made to provide a second, high resolution motor, or microactuator, to finely position a head at a radial position over a track, in addition to the low resolution actuator motor. These “dual-stage actuation” systems have taken a variety of forms. Some of the proposed designs would install a microactuator in the head slider itself. These designs require significant changes in the manufacturing of head sliders. A solution that allows existing mass manufacturing techniques for sliders to be used would be more desirable. Other proposed designs would replace a conventional gimbal with a specially designed silicon gimbal having a microactuator formed directly on the gimbal itself. Again, these designs require new, complex gimbal manufacturing techniques, which are less efficient than a solution that utilizes existing disc drive components. Still other proposed designs would mount a microactuator motor where the actuator arm meets the head suspension. While these designs often require only minimal changes in the actuator arm head suspension designs, the connection between the actuator arm and the head suspension must be carefully designed to include the microactuator motor. In addition, none of the proposed designs includes a microactuator having the capability of sensing a position of the head slider based on a state of the microactuator. A solution with this capability, that requires minimal additional design steps to conventional actuator assembly design, would be a significant improvement over the presently proposed dual-stage actuation systems.
The present invention is directed to a piezoelectric microactuator embedded in the actuator arm of a disc drive system. U.S. Pat. No. 4,814,908 to Schmitz discloses a system for radially positioning a transducing head over the center of a track on a rotatable disc by placing a thermal element on one side of the actuator arm. The arm is made of a material which expands upon heating and contracts upon cooling, so that the arm can be expanded or contracted (thereby radially moving the transducing head carried by the arm) in response to controlled heating or cooling of the thermal element. However, the thermal element has a relatively slow response time, making it inadequate for some high performance disc drive systems. Also, expansion of the thermal element in response to a given input stimulus is not sufficiently precise and predictable to serve as an effective high resolution positioning mechanism. The introduction of heat into the actuator arm affects the environmental conditions of the disc drive, which can have significant effects on the operation of the positioning system. Finally, the current state of a thermal element cannot be readily detected, making it difficult to determine the appropriate input stimulus to effect incremental transformation of the microactuator to precisely position the head over a selected track.
SUMMARY OF THE INVENTION
A system is provided by the present invention to position a transducing head in a disc drive device over a selected track of a rotatable disc having a plurality of concentric tracks. The disc drive device includes an actuator arm rotatable about an axis to move a slider carrying a transducing head mounted by a head suspension mechanism to the actuator arm. A low resolution motor moves the actuator arm about the axis to effect coarse movement of the head on the slider between tracks of the rotatable disc. A piezoelectric element is embedded in the actuator arm to distort the arm to effect fine positioning of the head on the slider. Control circuitry distributes electrical signals to selectively operate the low resolution motor and the piezoelectric element.
According to an optional feature of the present invention, the control circuitry includes an input circuit providing a track number corresponding to the selected track, and a feedback loop including a summing circuit comparing the selected track number and a current track number to determine the desired movement of the head, a piezoelectric element controller for operating the piezoelectric element to effect fine movement of the head and distributing the control signals representative of a number of tracks remaining to be traversed, and a low resolution motor controller receiving the control signals from the piezoelectric element controller and operating the low resolution motor in response to the control signals to effect coarse movement of the head.
One aspect of the present invention encompasses a method of manufacturing an actuator arm. A predetermined amount of material is removed from a side portion of the actuator arm to create a space in the actuator arm. A piezoelectric element is bonded into the space in the actuator arm.
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“An Experiment
Barina Jeffrey G.
Fard Anoush M.
Hawwa Muhammad A.
Le Tien Q.
Mohajerani Khosrow
Hall Carl E.
Kinney & Lange , P.A.
Seagate Technology LLC
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