JPS6348671A - Head positioning mechanism in magnetic disk storage device - Google Patents

Abstract

PURPOSE:To attain high speed accessing by providing the 1st head positioning actuator using a stepping motor as a drive source and the 2nd head positioning actuator mounted on the 1st actuator and using a piezoelectric substance as its drive source. CONSTITUTION:The 2nd head positioning actuator 2 exclusive for microstep is mounted on a swing arm 1 being a component of the 1st head positioning actuator. The 2nd head positioning actuator 2 consists of an asymmetrical bimorph 3 and an Eden spring extension mechanism 4. When a tip of the asymmetrical bimorph 3 is deflected to a fixed edge, the quantity of deflection is expanded by the Eden spring expansion mechanism 4 without friction and play and a head assembly 13 fixed by a screw 10 via a spacer 9 is moved nearly straightforward in a direction of arrow. Thus, the linear movement of the head assembly 13 causes each head to be moved straightforward simultaneously.

Description

[Detailed Description of the Invention] [Industrial Application Field] and [D] The invention is a magnetic disk recording system, in which a read/write head is moved over the magnetic disk to position it at a target track position. The present invention relates to a head positioning mechanism for performing head positioning.

[Conventional technology]

Among many file storage devices, magnetic disk storage devices have a large storage capacity and are highly accessible, so they have traditionally been indispensable as storage devices in computer systems. .

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 devices, the small Winchester-type hard disk drive (hereinafter referred to as HDD) is a device that has achieved rapid development over the past few years, and the main research and development goal of this device is to Improvements in the system and high-accuracy positioning of the RAD enable high-density recording and reproducing, shortening the 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 heads, but the head positioning mechanism is the key to HDDs, including high-density recording of information and shortening of access times. It's technology.

This head positioning machine groove uses a method using a voice coil, a stepping motor and a steel band.
It is broadly divided into combined methods.

Both types use closed-loop servo positioning, and many devices are now being seen that achieve full track densities of 600 to 750 TP.

The voice coil-based method is mainly aimed at shortening access time and increasing track density, but generally both the engine and the query air circuit are complicated, and they generate heat due to mastication.
In terms of shock resistance and perturbation, it required a considerable amount of effort to install, and Shin9 Note also lacked some aspects.

On the other hand, the method using the stepping motor has originally been widely used as a means of positioning the head in an open-loop method, but the drive used in the full open-loop method using the STEMP/G motor has a small storage capacity. The track density was also generally about 250 TPI.

The reason for this is that the stepping motor has a fairly large hysteresis and that the stepping motor continues to ring at a certain level even after its operation has ended.

The biggest problem is off-track caused by thermal expansion and contraction of mechanical parts.

For example, the misalignment that occurs between the base frame used in a 5''/' inch drive and the write/read head is approximately 0.1 μn for a 1°Cl7) temperature change.
1.

Therefore, the only way to solve these problems and realize a drive with high track density is to use a stepping motor as a semi-closed loop or full closed loop positioning system.

The reason why stepping motors are often used even if a closed loop system is adopted is that, in addition to providing stable access operation and high reliability compared to closed loop systems using a voice coil system, 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 vertical track movement of the head can be counted. It is possible to realize a control circuit.

[Problem that the invention seeks to solve]

Now, the stepping motor that is currently widely used in small magnetic disk storage devices is a motor that has a basic step angle of 1, 8, or 0.9 degrees and is controlled by a microstep generating circuit.

In this motor (ζ, theoretically by microstep control), it is possible to subtly shift the value of the winding current between each phase and further subdivide the basic step angle to achieve high track density.

However, in currently available stepping machines, the basic step error is ±3 to 4% and the hysteresis error is about 3%, so 0.45 degree microstep control (half-stellar control) is the practical limit. There was a problem that.

Therefore, this invention was made with attention to the above-mentioned problems, and its purpose is to achieve high accuracy and high tracking using a simple actuator without micro-stepping or driving the stepping motor. An object of the present invention is to provide a head positioning groove in a magnetic disk storage device that enables T degrees.

[Means for solving problems]

The structure of the present invention that meets the above object is to use a step drive of a stepping motor to detect the location where a target track exists.
- a first head positioning actuator that is movable to a reference track position; (The second head positioning actuator moves the first head positioning actuator downward, the first head positioning actuator Trino 3 moves the first head positioning actuator downward, and the second head positioning actuator 3 drives the second head positioning actuator.) head positioning actuator driver;
The gist of the present invention is to describe the first head positioning actuator driver, the second head positioning actuator driver, and the control means for sending the C seek command.

[Effect]

(If you try to move the head over the magnetic disk and position it at the target track position, move the head one rank from the magnetic disk master device.) When the control unit 17' is sent to the control unit (17'j), the control unit calculates the target track, the reference track of a certain zone, and the difference in position between the target track and the reference track, and performs the first head positioning process. A seek command is sent to the actuator driver and the second head positioning actuator driver.

As a result, the first head positioning actuator (actuator) and the stepping motor (step) move the position of the reference track in the self-zone of the target track.

Next, the second head positioning actuator moves the head nine times from the reference track position to the similar track CD position by microstep driving of the piezoelectric body.

Therefore, the above-mentioned problems can be eliminated.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a plan view showing a head positioning groove in a magnetic disk storage device according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a swing arm constituting a first head positioning actuator, and a second head positioning actuator 2 dedicated to microstepping is mounted on this swing arm 1.

This second head positioning actuator 2 is composed of an asymmetric bimorph 3 and an even spring expansion mechanism 4.

One end of the asymmetric bimorph 3 is connected to a screw 6 through a spacer 5.
It is fixed to the swing arm 1 by.

The other end of the asymmetric bimorph 3 also serves as one elastic plate 7 of the even spring expansion mechanism 4, and one bar:d of the other elastic plate 8 of the even spring expansion machine groove 4 is attached to the swing arm 1. It is fixed with screws 12 via 11.

When the tip 11i of the asymmetrical bimorph 3 bends with respect to the fixed end, the amount of bending is even (spring expansion → bond 4), and it expands without friction and play, and is expanded by the screw 10 via the base +j9. The fixed head assembly 13 moves approximately straight in the direction of the arrow.

The head fixing part 14 of the head assembly 13 is provided with a plurality of flexures 15, and each flexure 1
A read/write head 16 is attached to the tip of the head 50.

Therefore, from the direct position of the head assembly 13,
Each head 16:i at the same time, this outline・@i;'pλni■・
15.

FIG. 2 is a perspective view showing the details of the second throat positioning actuator.

This actuator is capable of magnifying and converting the asymmetrical movement of the morph into linear motion of the head via an even spring magnifying mechanism 4.

Specifically, the asymmetric bimorph 3 is made up of a piezoelectric body 17 and an elastic plate 7 joined together, and thin film electrical patterns (not shown) are formed on both sides of the piezoelectric body 17.

In addition, the elastic plate 7 is a component of the asymmetric bimorph 3 and also serves as a component of the even spring mechanism 4. It extends to the enlargement mechanism 41j.

The even spring expansion mechanism 4 connects an elastic plate 7 bent and extending approximately at right angles, the other elastic plate 8, and a spacer 18 of equal thickness interposed between the elastic plates 7 and 8 with screws or the like. It has a structure in which the head fixing part 14) is integrally provided.

Next, the principle of operation of the second head positioning actuator having the above configuration will be explained with reference to FIGS. 3 to 5.

FIG. 3 is an explanatory diagram showing a numerical model of an asymmetric bimorph.

As shown in the figure, when a constant voltage V is applied between both electrodes of the piezoelectric body 17 (thickness hl) that is mounted on the elastic plate 7 (thickness h2), the bimorph part (span l ) Deflection occurs in the bimorph part due to the discontinuity in the stress distribution that occurs in the cross section.

The deflection 1W(x) at this time is expressed by the following formula.

......(1) Here, SIE' is the elastic compliance of the piezoelectric material, d
l is the piezoelectric constant of the piezoelectric body, A1 is the density of the piezoelectric body, A2 is the density of the elastic plate, Pi is the natural angular frequency of the first mode, W4
(x) is the normal function of the first mode of deflection, A1 is the cross section 1
This is the next moment.

The first moment of area A1 is expressed by the following formula.

It is assumed that h(,,hl in equation (2) satisfies the following equation.

Here, the elastic compliance of the S2H elastic plate, ha
is the distance between the joint surface and the neutral plane.

From the above formula, the steady deflection WCl> of the tip is determined as W(1
) is expressed by the following formula.

・・・・・・・・・(4) Here, kl is the electromechanical coupling coefficient, 1111211o
is the second moment of area.

The moment of inertia of area IL II2 and IO are expressed by the following formulas.

FIG. 4 is a plan view showing the operation of the even spring expansion mechanism.

The distance between the two elastic plates 7 and 8 with the spacer 18 interposed is D.
, where the steady deflection of the bimorph tip is W(#) and the equivalent effective length of the elastic plate of the even spring expansion mechanism 4 is L, the head movement amount d4i is expressed by the following equation.

Here, C is a constant.

From equation (6), the steady deflection of the bimorph tip ~V (1)
Even if the distance d is small, a high magnification (decreased displacement d) can be easily obtained by increasing the equivalent effective length L of the elastic plate of the even spring expansion mechanism.

Figure 5 is a graph showing the calculation results using equation (4). In this graph, the vertical axis represents the normalized steady deflection of the asymmetrical Mymorph tip, and the horizontal axis represents the piezoelectric plate and elastic plate. It represents the thickness ratio.

As is clear from equation (4) and the graph, the steady deflection W
(The plate thickness ratio h2/hl increases in proportion to the applied electric field VE/hl, and the plate thickness ratio h2/hl that maximizes the steady deflection W (1)
It can be seen that there is only one h1.

As a result, the plate thickness ratio h2/'h of the bimorph that can most effectively output steady deflection under a constant applied voltage VE is determined.
1 is decided.

Next, a control system for controlling the reciprocating operation of the head positioning mechanism will be explained based on the above operating principle.

When applying a voltage to the piezoelectric body constituting the second head positioning actuator, it is not preferable to apply a voltage in the direction opposite to the polarization direction in which the spontaneous part of the piezoelectric body disappears (i.e., the polarization direction).

Therefore, when actually seeking the head using the second head positioning actuator, it is necessary to apply a voltage in the forward direction with respect to the polarization direction of the piezoelectric material to cause the head to move in the inner or outer circumferential direction. O FIG. 6 shows when the first head positioning actuator 2 and the second head positioning actuator are operated,
FIG. 7 is an explanatory diagram showing the tracks on which information is written and deleted on a magnetic disk; FIG. 1. For purposes of explanation, let the track pitch be I, and let θb be the basic step angle of the stepping motor used for the first positioning actuator.

In addition, the amount d of the head zone (second head positioning actuator) is calculated based on the electrical and mechanical specifications of the piezoelectric body and elastic plate actually used (-1) and (6) above.
Substitute it into the equation and apply the voltage value VE1 to the actuator. VB2 + , , di + for vEr
It is assumed that the calculation is as follows: d 2 +"'d r.

Now, the first head positioning actuator minimizes the basic step angle θb of the stepping motor, and can only obtain a head movement amount that is a multiple of the basic step angle θb.

Here, it is assumed that the following relational expression is satisfied between the track pitch p and the basic step angle θb.

Here, q represents the centering distance of the head per basic two-step angle.

Between the track on the magnetic disk that was positioned by e phase switching of the +-2 step motor in equation (7) and the track on the magnetic disk that was positioned by the 28th phase switching (hereinafter referred to as zone). ) means that the number of tracks is a.

It is quite conceivable that the track density expressed by equation (7) must be achieved under the constraints of the knob, the stepping motor specifications, and the design of the magnetic disk drive, and in such a case, it would be extremely difficult to achieve this. A special magnetic disk device will have to be manufactured.

Therefore, the head positioning mechanism ffL having the second head positioning actuator as a main part according to the present invention is extremely useful.

FIG. 8 is a block diagram showing a control system of this head positioning mechanism.

In the figure, reference numeral 21 denotes a CPU for controlling the positioning of the head, and this CPU 21 has a built-in register 22 for multi-function adjustment, a memory circuit 23, and an up/down count circuit 24.

The off-track register 22 Qi indicates the off-track signal read by the head 16 at the current track position. Processed with 325,,jq! This is a register that stores J.

There is a certain relationship between the amount of movement of the downwardly moving head 16 and the value of the required applied voltage with respect to the second head positioning actuator 2 (the memory circuit 23 controls this relationship). This is a circuit that is stored in advance as a head positioning information table of 2.

The amplifier down count circuit 241j calculates the moving track yr!1. from the difference between the current track position (i position and the target track position) based on the first control signal from the magnetic disk controller.
This is a circuit that counts.

27 is a D/A converter, and this D/A converter 27 receives the control information in the memory circuit 23 corresponding to the moving track from the up-down count circuit 24 and the off-track information stored in the off-track register 22. The voltage amplifier 28 converts the sum information including the track information into an analog signal.
This is what is output to.

The voltage amplifier 28 amplifies the analog signal from the D/A converter 27 into a drive signal and outputs it to the second head positioning actuator 2 .

This second head positioning actuator 2 is mounted on the first head positioning actuator 29, and can move and position the head 16 from the reference track 20k o position to the target track 20ki position by microstep drive of a piezoelectric body. It looks like this.

Next, the operation of the control system for the head positioning mechanism will be explained.

When the head 16 is moved to the target track position on the entire magnetic disk for positioning, the amount of movement of the head 16 (including the off-track correction amount) moved downward by the second head positioning actuator 2 and the movement thereof The value of the applied voltage necessary for the head positioning and the control information regarding the head positioning information are stored in advance in the memory circuit 23 as a second head positioning information table.

At the start of access, move the head 16 to the target track 20k.
A control signal for positioning at point i is sent from the magnetic disk control device to the up/down count circuit 24.

Based on this control signal, the up/down count circuit 24
calculates the number of moving tracks from the difference between the current track position and the target track position, and at the same time holds target track position information.

The off-track signal read by the head 16 at the current track position is processed by the off-track detection circuit 25 and stored in the off-track register 22 in advance.

The CPU 21 calculates the reference track 20kO of the zone 20k where the target track 20ki exists and the difference between the target track 20ki and the reference track 20ko, and calculates the difference between the target track 20ki and the reference track 20ko.
The head positioning actuator 29 of the reference track 2
In order to move the head to 0 kO, a seek command is sent to a first head positioning actuator drive (not shown).

When the first head positioning actuator 29 is performing a seek operation, the CPU 21 controls the target track 20k.
The sum of the position difference information between i and the 20kO track and the off track register 22 (. Microstep voltage control information corresponding to the sum information is sent to the D//A converter 27.

The output voltage converted into an analog signal by the D/converter 27 is amplified by the voltage amplifier 2; The head 16 is positioned at , and the seek operation is completed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, there is provided a first head positioning actuator using a stepping motor as a driving source, and a second head positioning actuator mounted on this actuator and using a piezoelectric body as a driving source. Since the configuration includes the following effects, the following effects can be obtained.

(1) By simply installing a simple and lightweight second head positioning actuator, access can be achieved at a fairly high speed.

(2) Since the second head positioning actuator uses a piezoelectric body operated by application of voltage as a drive source, the second head positioning actuator drive can have an extremely simple configuration.

(3) Electromagnetic noise that tends to occur in electromagnetic actuators does not occur at all in the second head positioning actuator.

As a result, this second head positioning actuator is extremely useful as an actuator for a magnetic disk storage device that is sensitive to external magnetic fields.

(4) In the case of an actuator using a stepping motor or a knob as a drive source, in the conventional technology, the relationship between the minimum track pitch and the basic step angle of the stepping motor is given by the above equation (7), so high track density can be achieved. In order to achieve this, a stepping motor with a small basic step angle was indispensable, whereas in the present invention, high density can be easily achieved by simply installing a second head positioning actuator.

[Brief explanation of drawings]

Figure 1 is a plan view showing the front of the head positioning machine according to the embodiment, Figure 2 is a perspective view showing details of the main parts of the positioning machine, and Figure 3 is a numerical model of the embodiment. FIG. 4 is an explanatory diagram showing the operating principle of the embodiment, FIG. 5 is a graph showing the calculation results, FIG. 6 is an explanatory diagram showing the zone division of the magnetic disk, and FIG. 7 is an explanatory diagram showing the head positioning location. FIG. 8 is a Glock diagram showing the control system of the embodiment. 1... Swing arm 2... Second spatula positioning actuator 3... Asymmetrical permorph 4.
... Even spring 5 dogs @<4 7... Elastic plate 8...
・Elastic plate 13...Head 1 side solid 14...Head width 3i 15...Flexure 16・Head 17・
...Pressure? =21...CPU 22...Off-track register 23...Memory circuit 24...
Amplifier down-count circuit 25... Off-track outgoing path 27...-D//, input converter 28... Positive pressure amplifier 29... Head positioning actuator for millet 1. Patent Applicant Okitoriki Kogyo Co., Ltd. Representative Patent Attorney Takashi Imakura 2 Wataru

Claims (1)

[Claims] 1. A first head positioning actuator that is movable to the position of the reference track in the zone where the target track exists;
a second head positioning actuator that moves the head from the reference track position to the target track position; a first head positioning actuator driver that drives the first head positioning actuator; and a second head positioning actuator that drives the second head positioning actuator. A head positioning mechanism in a magnetic disk storage device, comprising: a second head positioning actuator driver; and a control section that sends a seek command to the first head positioning actuator driver and the second head positioning actuator driver. 2. Claim 1, wherein the first head positioning actuator is a stepping motor that performs step drive.
A head positioning mechanism in the magnetic disk storage device described in 1. 3. A head positioning mechanism in a magnetic disk storage device according to claim 1, wherein the second head positioning actuator is a piezoelectric body that performs microstep drive.