Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2000-03-10
2003-11-04
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06643088
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-226498, filed Aug. 10, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a load/unload type magnetic disk drive which is constructed in a manner that when a rotation of a magnetic disk is stopped, a magnetic head is mounted on a ramp so as to be unloaded, and when the magnetic disk is rotated, the magnetic head is moved onto the magnetic disk so as to be loaded. In particular, the present invention relates to a magnetic disk drive which can preferably control a movement of carriage for carrying a magnetic head, and to a method of controlling a movement of carriage in an unload operation of a magnetic head.
Conventionally, in general, a contact start and stop method, what we call, a CSS method has been applied to an apparatus which records information in a magnetic disk by a magnetic head, and reproduces the information therefrom, for example, a small-size magnetic disk drive. The above CSS method has the following features.
First, in a CSS type disk drive, in a drive non-operation state, that is, in a state that a magnetic disk functioning as a recording media is not rotated, a magnetic head contacts with the disk. When the magnetic disk is started to rotate, the head receives an air bearing action by an air flow generated between the magnetic disk and the head, so that the head can be floated from the magnetic disk. In the disk drive having the structure as described above, in the initial stage of a rotation start of the magnetic disk and in the final stage of a rotation stop thereof, the head is slid on the magnetic disk in a state of contacting with the magnetic disk. For this reason, there is a possibility that a damage is given to a data area on the magnetic disk. In particular, in the case where an impact or the like is given to the drive from the outside, there is a high possibility that a damage is given to the magnetic disk.
For this reason, in the above CSS type magnetic disk drive, for the duration when the magnetic disk is in a rotation stop state, the head is positioned to a place different from a data zone on the magnetic disk, for example, a ring-like retracting zone for only head, which is secured on an inner peripheral side of the data zone, what we call, a CSS area. In the case where an electric power is supplied to the drive, or in the case where the host system gives an instruction to rotate a spindle motor (i.e., SPM) rotating the magnetic disk at a high speed, the spindle motor rises up by a steady-state speed in a state that the head is positioned to the above CSS area, and thereafter, the head is floated from the magnetic disk. The head is moved to the data zone on the magnetic disk for the first time after being floated. On the other hand, when the host system gives an instruction to stop the spindle motor in a state that the head is positioned to the data zone, the head is retracted to the CSS area, and thereafter, the spindle motor is stopped.
In the case where the head is retracted to the CSS area, by a driving force of a voice coil motor (i.e., VCM), a carriage functioning as a head moving mechanism, that is, an actuator collides with an inner peripheral stopper, and thereby, it is possible to prevent the head from going out of the CSS area.
In recent years, in the light of the concept of improving an impact resistance performance of disk drive and improving a recording density, in place of the aforesaid CSS technique, a head load/unload operation has been proposed such that the head and the magnetic disk have no contact with each other in the case where the magnetic disk is in a rotation stop state. In this load/unload operation, when a rotation of the magnetic disk is stopped, a tab, which is a distal end portion of suspension of the carriage, is slid along a ramp having an inclination provided outside the magnetic disk, and thereby, the head is lifted up from the magnetic disk, then, is retracted outside the disk so as to be unloaded, and thereafter the rotation of the magnetic disk is stopped. Moreover, when a rotation of the magnetic disk is started, that is, in a rotation start state, the rotation of the disk reaches a steady-state speed, and thereafter, the head is moved from the ramp onto the magnetic disk, and thus, is loaded.
In the above load/unload operation, a surface of the magnetic disk, that is, a flatness is improved, and a floating amount of the head is reduced, and thereby, it is possible to improve a recording density of the magnetic disk. In general, in the CSS action, the more the surface, that is, a flatness of the magnetic disk is improved, the head and the magnetic disk contact with each other when the spindle motor is stopped; as a result, the head and the magnetic disk contact with each other, and are mutually attracted. For this reason, there is a problem that it is difficult to apply the above CSS method to a magnetic disk having a high surface accuracy. In order to solve the above problem, it is indispensable to apply a head load/unload operation such that in an operation of the case where the spindle motor is stopped, the head is retracted to the ramp provided outside the magnetic disk so that the head and the magnetic disk becomes a non-contact state.
In such a head load/unload operation, during a head unload operation, the head must be moved at a low speed and at a constant speed so that the head does not contact with the magnetic disk. Usually, in a head load/unload control in the case where a power source is in an on-state, a back (counter) electromotive voltage generated in a voice coil motor is detected, and then, a detection signal is processed by a microprocessor (CPU), and thus, a moving rate or speed &ohgr; of the carriage is controlled to a low desired speed. Conventionally, there is a feedback control system having an unload speed control system block as shown in
FIG. 1
, as a control system for controlling a moving rate or speed &ohgr; of the carriage to a desired speed &ohgr;r.
As well known, in a feedback control system, a follow-up lag is generated. In the head unload operation, the follow-up lag is also generated, and there is a problem that the lag causes the following undesirable results.
First, so long as the head is moved on the magnetic disk to an outer circumferential direction (ramp direction), no external force such as a frictional force or the like acts onto the tab of the distal end of the suspension supporting the head; therefore, an external force acting onto the carriage is small. To the contrary, in a state that the head or the tab is moved on the ramp, a friction is generated between the tab and the ramp, and a load fluctuation (change) acts onto the carriage as a disturbance. In particular, in a head structure using a currently popular negative pressure head as the head, when the head is lifted out of the magnetic disk to the ramp, an external force is required for release a negative pressure generated between the head and the magnetic disk, and this is a load of hindering an unload operation.
As described above, in the above head load/unload type magnetic disk drive, in the head unload operation, when the head is separated from the magnetic disk, an external force of a direction hindering an unload operation rapidly acts onto the carriage. For this reason, there is the following problem in the speed feedback control system as shown in
FIG. 1
applied to the conventional magnetic disk drive according to a speed feedback control which is carried out in the following manner that a back electromotive voltage generated in the voice coil motor is measured, and a moving rate or speed &ohgr; of the head or the carriage is detected, and thus, the moving rate or speed &ohgr; is approximated to a desired speed &ohgr;r. More specifically, in the above speed feedback control system, a follow-up lag is generated; as a result, a moving rate or speed of the head
Gray Cary Ware & Freidenrich LLP
Hudspeth David
Kabushiki Kaisha Toshiba
Tzeng Fred F.
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