JPS63122069A - Head positioning system for magnetic disk storage device - Google Patents

Abstract

PURPOSE:To attain high density track by setting a moving quantity from a present track position and an object track position of a magnetic head and applying seek operation in two stages. CONSTITUTION:A present track position of a magnetic head 12 is detected by an off-track detection circuit 60 and stored in an off-track register 33. An up-down circuit 31 calculates the difference between a present track position and an object track position to hold object track position information. Moreover, the circuit 31 calculates a reference track of an object track zone to give a 1st seek instruction to a 1st mechanism so that the head 12 is moved to a reference track. While the mechanism 70 applies seekoperation, a difference between the object track and the reference track is calculated by a CPU 30 and the control information is inputted to a 2nd head mechanism 80 from a memory circuit 32 via the circuit 31 to apply a 2nd seek operation. The seek is executed in a minute step in this way and the high density track is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a head positioning method for a magnetic disk storage device, particularly a hard disk device.

(Prior Art) Among many file storage devices, magnetic disk storage devices have a large storage capacity and can be accessed at high speed, so they have traditionally been indispensable as storage devices in computer systems. ing. Recently, many small-sized magnetic disk storage devices have been used in small-sized information processing systems such as personal computers and office automation equipment.

Among these, the small Winchester-type hard disk drive (HDD) is a device that has undergone rapid development over the past few years, and its current main research and development goals include improving the electromagnetic conversion system and developing a high-precision magnetic head. These include high-density recording and playback through positioning, shortening of head access time, and making the device smaller, thinner, and more robust.

In particular, the increase in density is largely due to the basic technology of magnetic disks and magnetic heads, but the positioning of magnetic heads, that is, the head positioning mechanism, including high-density recording of information and shortening of access time, This is a key technology for hard disk drives.

The head positioning mechanisms that are widely used in current hard disk drives are roughly divided into those that use voice coils and those that use step motors and steel belts. Achieved a track density of

The voice coil method is mainly aimed at shortening access time and increasing track density, but the mechanism and electrical circuits are generally complex, and the design is quite burdensome in terms of heat resistance, shock resistance, and vibration resistance. It takes a lot of time, and it also reduces reliability.

On the other hand, the step motor method is originally widely used as a means for positioning the head using an oven loop method, and hard disk drives using this method generally have a small storage capacity and a track density of 250 TPI.

The reasons for this are that the step motor has a considerable amount of hysteresis, that the step motor continues to ring to a certain extent even after it has finished operating, and that the biggest problem is off-track due to thermal expansion and contraction of the mechanical part. can be given.

For example, the positional deviation that occurs between a pace frame used in a 5174-inch drive and a write/read head is approximately 0.1 μm due to a temperature change of 1° C.

Therefore, the only way to solve this problem and realize a drive with a high track density is to use a step motor as a semi-residual or fully closed loop positioning system. The reason why step motors are often used even when using the closed-loop method is that, in addition to having more stable access operation and higher reliability than the voice coil closed-loop method, the head positioning mechanism is extremely simple. In addition, there is no need to prepare a special count generator such as an encoder, and by counting and managing the number of step pulses, the amount of track movement of the head can be counted, making the control circuit simple and inexpensive. be.

(Problems to be Solved by the Invention) Step motors currently widely used in hard disk drives have a basic step angle of 1, 8, or 0.9 degrees, which is controlled by a microstep generation circuit. Theoretically, this microstep control makes it possible to subtly shift the value of the winding current for each correlation, further subdividing the basic step angle, and achieving high track density. However, currently available step motors have a basic step angle error of 13 to 4%.
Since the hysteresis error is about 3%, microstep control (half-step control I) of 0.45 degrees is considered to be the practical limit.

For this reason, in the case of a hard disk drive using a step motor, there is a certain limit to the track density on the magnetic disk.

The present invention has been made in view of the above circumstances, and its purpose is to provide a head positioning method for a magnetic disk storage device that allows seek operations to be performed in fine steps using a simple mechanism, and that can achieve higher track density. It's about doing.

(Means for Solving the Problems) In order to achieve the above object, a head positioning method for a magnetic disk storage device according to the present invention provides a head positioning method for a magnetic disk storage device in which a first A head moving mechanism, a second head moving mechanism mounted with a magnetic head and attached to be movable relative to the first head moving mechanism, and a first head moving mechanism are moved to a reference track of a zone to which the target track belongs. a first driving means; a second driving means;
a second drive means for moving the head moving mechanism from the reference track to the target track with a smaller speed than the first drive means; and a movement amount of the magnetic head from the current track position of the head and the target track position detected by the magnetic head. and sends a first seek operation command from the current track position to the reference track position to the first drive means, calculates the difference between the target track position and the reference track position, and causes the second drive means to seek the first seek operation from the current track position to the reference track position. and a control means for sending two seek operation commands.

(Operation) With these configurations, the current track position information of the head detected by the magnetic head is once sent to the magnetic disk control device, and from there the current track position and target track position information are sent to the control means.

The control means sets the movement fj m of the magnetic head from the two pieces of information, sends a first seek operation command to the first drive means,
The first driving means once moves the first head moving mechanism to a reference track position of a zone including the target track. Next, the control means calculates the difference between the target track position and the reference track position, and sends a second seek operation command to eliminate this difference to the second drive means. The second driving means moves the second head moving mechanism in finer steps, so that the magnetic head is positioned on the target track.

(Example) FIG. 1 is a plan view of a head mechanism used in the head positioning method of the present invention, in which a swing arm 11 is used as the first head moving mechanism. As is well known, the swing arm 11 moves the magnetic head 12 at the tip in the direction of the arrow, that is, the magnetic disk 10 by the operation of a step motor (not shown).
move in the radial direction.

In the present invention, the second head moving mechanism that operates in microsteps and this drive mechanism are integrally attached to the tip of the swing arm 11, and in this embodiment, the second head moving mechanism has an Eden spring mechanism 13, and the drive mechanism is asymmetrical. bimorph 1
4 is used.

FIG. 2 shows a perspective view of the Eden spring mechanism 13 and the bimorph 14, and shows the Eden spring [! 13 is composed of two leaf springs 15, 16 and a spacer 17 held between them. The leaf spring 15 is attached to the swing arm 11 by a screw 19 via a spacer 18, as shown in FIG.
The leaf spring 16 is bent at a right angle, and its base end is attached to the screw 2 through a spacer 20.
1 is fixed to the top surface of the tip of the swing arm 11.

The tips of the leaf springs 15 and 16 are parallel to each other with a spacer 17 in between, and a fixing block 22 is fixed to the left side of the leaf spring 15, and each element is screwed through a spacer 23 as shown in FIG. They are fixed together by 24. The tip of the fixed block 22 is branched into a plurality of parts (FIG. 2), and the base end of a flexure 25 (FIG. 1) is fixed to each of them, and a magnetic head 12 for reading and writing is attached to the tip of each flexure 25. There is.

Therefore, the magnetic head 12 corresponds to each of the magnetic disks 10 that rotate at high speed in a stacked state on a spindle (not shown), and the flexure 25 elastically supports the magnetic head 12.

The bimorph 14 is constructed by superimposing a piezoelectric body 27 on a leaf spring portion 16A forming the base end of the leaf spring 16,
Thin film electrodes (not shown) are formed on both sides of the piezoelectric body 27 so that deflection occurs due to piezoelectric strain.

This piezoelectric material 27 has been used for a long time as a transducer that mutually converts mechanical signals and electrical signals, and recently PZT, which has high conversion efficiency and excellent mass production, is used as a transducer. Piezoelectric ceramics are advantageous. This piezoelectric body 27 can be used in two types: normal piezoelectric longitudinal effect and piezoelectric transverse effect. The present invention will be explained by taking as an example a bimorph type which has developed the use of the piezoelectric transverse effect, but the present invention is of course not limited to the use of the piezoelectric transverse effect.

FIG. 3 is a principle diagram of the bimorph 14, and FIG. 4 is a plan view showing the relationship between the Eden spring mechanism 13 and the bimorph 14.
For convenience of explanation, the arrangement direction is different from that in FIG. 1.

First, the principle of the bimorph 14 will be explained based on FIG. Bimorph 14 length! When the lead wires 28 are connected to both sides of the piezoelectric body 27 and a voltage VE is applied, the bimorph 14 is deflected due to the discontinuity in the stress distribution that occurs in the cross section.

If the deflection of a portion of the bimorph 14 at a distance of X from the fixed end is W(x), then it is expressed as follows. Here, SE: elastic compliance of the piezoelectric body 27.

dl: piezoelectric constant of the piezoelectric body 27, ρ1. ρ2: piezoelectric body 2
7. Density of leaf spring 16A, pi: natural angular frequency of i-th mode, W(x): normal function of i-mode of tU.

h, 2 t+(s'i/5z)(h2/hυ
...(3) S2: Elastic compliance of leaf spring 16A.

hO: distance between bonding surface and neutral plane, hl: piezoelectric body 27
Thickness, h2: Thickness of the leaf spring 16A.

When the steady deflection of the tip is calculated from the above equation, it is expressed as...(4). Here, 1: electromechanical coupling coefficient, I, I, 12: new surface second moment.

Such steady deflection of the bimorph 14 is magnified by the Eden spring mechanism 13 and transmitted to the magnetic head 12, as shown by imaginary lines in FIG. Here, the magnetic head 12
If the displacement of is d, then W(J) d=CL・□...(6) Here,
C: constant, L: equivalent effective length of leaf spring 15, D: leaf spring 1
The interval is 5.16.

According to the above equation (6), even if the deflection W(1) at the tip of the bimorph is minute, if the interval is made small, a highly magnified displacement d can be easily obtained. FIG. 5 is a graph showing the effect of this calculation, in which the vertical axis represents the normalized steady deflection of the tip of the asymmetric bimorph, and the horizontal axis represents the thickness ratio h2/hl of the piezoelectric body 27 and the leaf spring 16A.

From equation (4) and Fig. 5, it can be seen that the steady deflection W(J) increases in proportion to the applied electric field VE/hl, and that there is only one plate thickness ratio h2/h1 that maximizes the steady deflection. I understand. In this way, a constant applied voltage VE
Under these conditions, the plate thickness ratio h2/h1 can be determined for the bimorph 14 that can most effectively output steady deflection.

Note that when applying a voltage to the piezoelectric body 27, it is not preferable to apply the voltage in a direction in which the spontaneous polarization of the piezoelectric body 27 disappears (in a direction opposite to the branching direction). Therefore, in order to actually cause the magnetic head 12 to seek, it is necessary to apply a voltage in the forward direction with respect to the polarization direction of the piezoelectric body 27 to cause the magnetic head 12 to seek in the inner or outer circumferential direction.

FIG. 6 is a simplified plan view comparing the tracks on the magnetic disk 10 and the track positions where the step motor can stop. As can be seen from this figure, the first head moving mechanism can only minimize the basic step angle θb of the step motor and only move the head corresponding to a multiple thereof.

Here, suppose that e is between track pitch p and Ob.
p □=□ ...(1) Assume that there is a relationship of a δθb. Here, δ represents the distance that the magnetic head 12 moves on the disk per basic step angle.

This equation (7) shows that the magnetic head 12 can be positioned on the track of the magnetic disk 10 every time the step motor changes the phase of rotation e, and the magnetic head 12 can be positioned on the track on the disk positioned at the 20th phase change (zone This means that there are 8 tracks in the file.

In other words, it is quite conceivable that the track density expressed by equation (7) must be achieved due to the specifications of the step motor and the counting constraints of the disk device. will have to be manufactured.

However, even such a case can be sufficiently handled by the Eden spring mechanism 13, which is the second head movement mechanism, and the bimorph 14 that drives the Eden spring mechanism 13.

In other words, the magnetic head 12 seeks f? id is determined by substituting the electrically and mechanically set numbers of the piezoelectric body 27 and leaf spring 16A actually used into the above equations (6) and (4), and applying the applied voltage ■E1. ■、2.・・・・・・dl for Ver.
.

It can be calculated as d2... dr. Therefore, these control information may be stored in advance in a memory circuit, which will be described later, as a plurality of information tables.

FIG. 7 shows a bimorph 14 and an Eden spring mechanism 13.
A positioning control circuit diagram for causing the magnetic head 12 to perform a seek operation to a target track is shown.

This circuit includes a microprocessor (CPU) 30, D/
A converter 40. Voltage amplifier 50. The CPU 30 includes an up/down count circuit 31, a memory circuit 32, and an off-track register 33. Further, the step motor and swing arm are shown as a first head mechanism 70, and the Eden spring mechanism and bimorph are shown as a second head mechanism 80.

The up/down count circuit 31 sends a seek operation command to the first head mechanism 70 and the second head groove 80 based on signals from the magnetic disk controller and the memory circuit 32.

A memory circuit 32 is connected to the up/down count circuit 31, and the memory circuit 32 stores the relationship between the applied voltage (E) to the bimorph 14 and the microstep fad of the head as control information, as described above. Moreover, on the output side of the up/down count circuit 31,
A D/A converter 40 is connected, and a voltage amplifier 50 is connected to the output side of the D/A converter 40.

The bimorph 14 (FIG. 4) of the second head mechanism 80 is connected to the output side of the voltage amplifier 50, and the second head mechanism 80 moves slightly to position the magnetic head 12 on the target track.

An off-track detection circuit 60 is connected to the magnetic head 12, which detects the current track position of the magnetic head 12 and stores this signal in the off-track register 33. The off-track register 33 sends this information to the magnetic disk controller.

Each head mechanism 7 is controlled by the control circuit configured as described above.
0.80 works as follows. For ease of explanation, each track of the magnetic disk 10 is shown in FIG. 8, and in this figure, zones 101, 102, . . . , 10, zones 1010, 1020, . ...0.10 to 10
(k+1)), 10nO is for each track, and 1 in 10
．． 10 to 2. -10kt, 10myo is a truck in zone 10, of which 10kt is the reference track, 10m
Let ki be the target track. Each zone and reference track are settings made by the control device, and no special tracks are formed on the magnetic disk 10.

In head positioning, the current track position of the magnetic head 12 is first detected by the off-track detection circuit 60 shown in FIG. 7, and this information is stored in the off-track register 33.

The information in the off-track register 33 is first processed by an external magnetic disk control device and sent to the up/down count circuit 31 together with a control signal for moving the head to the target track 10ki.

The up/down count circuit 31 calculates the number of moving tracks, which is the difference between the current track position and the target track position, and at the same time holds target track position information.

Further, the up/down count circuit 31 calculates the reference track 10kO in the zone 10 where the target track 10ki exists based on the above-mentioned information, and controls the first head mechanism 7 so that the magnetic head 12 moves to the reference track 10kO.
A first seek command is issued to step motor 0 (not shown). At this time, off-track correction (track servo) is also performed based on the information in the off-track register 33.

When the first head mechanism 70 is performing the first seek operation, the difference between the target track 10ki and the reference track 10kO is calculated by the CPU 30, and control information (voltage
E) is sent. The control information from the up/down count circuit 31 becomes an output voltage VE, is converted into an analog signal by a D/A converter 40, is amplified by a voltage amplifier 50, and is input to the second head mechanism 80.

The tip of the bimorph 14 of the second head mechanism 80 is bent with respect to the fixed end by the applied voltage (2) as shown in the fourth figure.
This deflection ω is amplified by the Eden spring mechanism 13 without causing any friction or play, and the magnetic head 12 at the tip reaches the target track 10ki almost linearly, thereby completing the second seek operation.

Since the bimorph 14 operates only by applying a voltage, the driving circuit can be simplified, and the entire head line drawing can be made lighter. Furthermore, since the bimorph 14 does not generate electromagnetic noise unlike conventional electromagnetic actuators, it is extremely advantageous for magnetic disk storage devices that dislike external magnetic fields.

In this embodiment, the swing arm 11 is used as the first head moving mechanism, but the present invention is also applicable to a carriage that moves linearly. Further, although the Eden spring mechanism 13 is used as the second head moving mechanism and the bimorph 14 is used to drive the head, other driving means can be used as long as it can move in finer steps than the step motor.

(Effects of the Invention) As described above, the present invention includes a first head moving mechanism arranged to be movable in the radial direction of a track formed on a magnetic disk, and a magnetic head mounted on the first head moving mechanism. A second head moving mechanism is mounted to be able to move relative to the first head! a first drive means for moving the PII'g3 structure to a reference track in a zone to which the target track belongs; a second drive means for moving the second head moving mechanism from the reference track to the target track in smaller steps than the first drive means; , setting the amount of movement of the magnetic head from the current track position and target track position of the head detected by the magnetic head, and sending a first seek operation command from the current track position to the reference track position to the first driving means;
The control means calculates the difference between the target track position and the reference track position and sends a second seek operation command to the second drive means to the target track position, so that the second head moving mechanism can move in finer steps. A seek operation will be performed.

Therefore, it is possible to increase the track density of the magnetic disk without requiring a step motor with a particularly small step angle.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the head reorganization used in the head positioning system of the present invention, Fig. 2 is a perspective view of the Eden spring mechanism and bimorph, Fig. 3 is a principle diagram of the bimorph, and Fig. 4 is the same as Fig. 2. A plan view, FIG. 5 is a graph showing the characteristic curve of the bimorph, FIG. 6 is a simplified plan view showing the track and step motor stop position, FIG. 7 is a positioning control circuit diagram of the magnetic head, and FIG. FIG. 3 is a partial plan view showing each track of FIG. 10...Magnetic disk, 11...Swing arm. 12...Magnetic head, 13...Eden spring mechanism,
14... Bimorph, 27... Piezoelectric body, 30...
Microprocessor, 31...Up-down circuit, 3
2... Memory circuit, 60... Off-track detection circuit, 70... First head mechanism, 80... Second head mechanism.

Claims (5)

[Claims] (1) A first head moving mechanism arranged to be movable in the radial direction of a track formed on a magnetic disk, and a second head equipped with a magnetic head and attached to be movable relative to the first head moving mechanism. a moving mechanism; a first driving means for moving the first head moving mechanism to a reference track of a zone to which the target track belongs; and a second driving means for moving the second head moving mechanism from the reference track to the target track in smaller steps than the first driving means. a second driving means; and a second driving means, which sets a moving amount of the magnetic head based on the current track position and target track position of the head detected by the magnetic head;
Sending a first seek operation command from the current track position to the reference track position to the driving means, calculating the difference between the target track position and the reference track position, and transmitting a second seek operation command to the second driving means from the target track position. A head positioning method for a magnetic disk storage device, comprising: a control means for transmitting the data; (2) The head positioning method for a magnetic disk storage device according to claim 1, wherein the first head moving mechanism is a swing arm. (3) The head of the magnetic disk storage device according to claim 1, wherein the second head moving mechanism is an Eden spring mechanism that is composed of two leaf springs and a spacer and amplifies displacement on the input side. Positioning method. (4) A head positioning system for a magnetic disk storage device according to claim 1, wherein the first driving means is a step motor. (5) The head positioning system for a magnetic disk storage device according to claim 1, wherein the second driving means is a bimorph composed of a piezoelectric body and a leaf spring.