Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-01-12
2001-09-18
Hudspeth, David (Department: 2753)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06292323
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an information recording and reproducing apparatus, and particularly to a system for removing accumulated particles that have adhered to a read/write head during operation.
2. Description of Related Art
In magnetic disk devices, a lubricating oil is used for the spindle motor, voice coil motor, and other components which are contained in a housing, and during operation, the aerosol lubricating oil is floating in the housing. If the magnetic disk device is operated for a long time in such an environment, hydrocarbons, which are a component of the lubricating oil, and internally produced dust and other particles stick to the magnetic head. The accumulated particles that adhere to the magnetic head alter the floating characteristics of the magnetic head on the magnetic disk surface. Further, in magnetic disk devices employing the CSS (Contact Start Stop) starting method, hydrocarbons move around to the underside (the surface facing the disk) of the slider to cause the disk and the slider to stick to each other while the magnetic disk is stationary, hereby causing a phenomenon, referred to as stiction, which can prevent restarting rotation of the disk.
One conventional method for removing accumulated particles that have adhered to the magnetic head is an ADM (Automated Disk Monitor) method in which the magnetic disk device is stopped and restarted by the CSS starting method, and the sliding between the magnetic disk and the magnetic head is used to remove accumulated particles on the magnetic head. However, the ADM method requires that the magnetic disk device stop for 10 to 20 seconds for each operation, and it is increasingly difficult to employ this method in recent computer systems which need to operate continuously. In addition, this method cannot be used in magnetic disk devices in which the CSS method is not employed.
Published Unexamined Japanese Patent Application No. 62-229,514 discloses a magnetic disk device in which, with the magnetic head being positioned at a track, the magnetic head is vibrated by moving it in the seek direction when the data read/write operation is stopped, so as to remove the dust adhering to the slider surface of the core of the magnetic head. However, this publication does not specifically disclose the amplitude and frequency of the oscillator for vibrating the head, nor does it show a vibration mode that is effective in removing the dust.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for removing accumulated particles that have adhered to a head of an information recording and reproducing apparatus, and an information recording and reproducing apparatus employing such method. More specifically, an object of the present invention is to provide a technique for removing accumulated particles only by controlling the seek operation of the actuator arm without requiring adding hardware to a conventional device or adding any special processing.
It is a further object of the present invention to provide a technique for removing accumulated particles in which, when a command comes from a host computer during the removal of accumulated particles, the command can be immediately executed.
In the present invention method for removing accumulated particles by vibrating the head through a seek operation, the amplitude of the vibrations are determined based upon the amount or length of the particles that have accumulated on the head. The amplitude of the head vibrations are selected so as to be close to the length of the accumulated particles. Typically, at the time the head is vibrated the length of the accumulated particles is not accurately known. In the present invention, to provide a vibration amplitude near the length of the accumulated particles, the amplitude is gradually changed to vibrate the head over a range of amplitudes. The head is moved in seek operations by providing a signal to the drive system of the actuator arm.
In one embodiment of the present invention, a read/write operation of the head is stopped, and a seek operation is performed a predetermined number of times for each of a plurality of amplitudes over a predetermined range of amplitudes. Accordingly, amplitudes near the length of the accumulated particles can be included in the series of amplitudes, and thus accumulated particles can be effectively removed. Furthermore, the recording medium itself continues to rotate while the head performs the seek operations to remove the accumulated particles. Thus, if an access command comes from a host computer, the head can be positioned at a predetermined track to execute the command requiring only the time for restarting the read/write operation and performing a seek operation. In the present invention, the amplitude means an inter-peak value determined by the number of cylinders (tracks) the head moves. Furthermore, gradually changing the amplitude includes gradually increasing the amplitude from a small value to a large value, gradually decreasing the amplitude from a large value to a small value, and a combination of increasing and decreasing periods. The number of seek operations at each amplitude may be constant, or varied over the range of amplitudes. Also, although the frequency of vibrations gradually changes as the amplitude for the seek is gradually changed, the frequency of the vibrations is preferably selected in the range of 100 to 600 Hz.
In another embodiment of the present invention, the maximum amplitude of the selected plurality of amplitudes is selected to be at least greater than the length of accumulated particles that have adhered to the slider. Accordingly, it is more likely that an amplitude near the length of the accumulated particles is selected from the plurality of amplitudes. When the operation of removing accumulated particles according to the present invention is performed, the length of accumulated particles should be between the maximum vibration amplitude and the minimum vibration amplitude. In a preferred embodiment, the procedure for removing accumulated particles is executed before the particle accumulation becomes so large that the stiction prevents restarting rotation of the disk. The minimum amplitude value is selected to be a value smaller than an estimated length of the accumulated particles at the point where the stiction caused by the accumulated particles prevents restarting rotation of the disk.
Although the present invention can be implemented by changing the control program of the information recording and reproducing apparatus, alternatively the present invention can also be implemented by adding hardware to a conventional information recording and reproducing apparatus.
REFERENCES:
patent: 4510541 (1985-04-01), Sasamoto
patent: 5461521 (1995-10-01), Ito et al.
patent: 1-30017 (1989-01-01), None
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patent: 2-50312 (1990-02-01), None
patent: 3-183008 (1991-08-01), None
patent: 3-225669 (1991-10-01), None
patent: 6-333378 (1994-12-01), None
patent: 97/19449 (1997-05-01), None
Harada Yoshinao
Sato Masahiko
Satoh Takumi
Tanaka Hidetsugu
Bluestone Randall J.
Habermehl James L
Hudspeth David
International Business Machines - Corporation
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