JP2703073B2 - Conversion element driving device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conversion element driving device of an information recording device such as a magnetic disk device, a magnetic tape device, a magneto-optical disk device, a magnetic card device, and the like. The present invention relates to a conversion element driving device applied to a large-capacity storage device which needs to be positioned on a track with high accuracy, particularly, a high track density.

[Conventional technology]

2. Description of the Related Art In a conventional information recording apparatus, for example, a magnetic disk apparatus, a track density as well as a bit density has been increased with an increase in capacity. Due to the increase in track density, track pitches are now on the order of a few μm, and increasing the accuracy of positioning the transducer (magnetic head) is becoming an increasingly important issue. The conventional servo surface servo method, which has relatively high positioning accuracy, uses a conversion element for reading servo information (hereinafter referred to as "servo head") and a conversion element for reading and writing data due to local temperature changes in the apparatus or deformation of an actuator. (Hereinafter referred to as a data head), a positioning error occurs. Therefore, as one method of increasing the positioning accuracy of the servo system, there is a method of providing positioning means only for the head element portion, separately from the positioning means using the head actuator, as a means for correcting the positional deviation between the servo head and the data head. It is shown in "JP-A-62-250570". This is the traditional
The actuator drive by VCM is used for coarse movement positioning, and a fine movement positioning actuator is arranged near the magnetic head.

[Problems to be solved by the invention]

However, the above technology is based on the premise that a servo surface is provided in addition to the data surface, and the purpose is to compare and correct the head position determined by the servo head with the positional deviation from the actual data track. Therefore, it is necessary to design a track width and a control system in consideration of vibration transfer characteristics between data heads, temperature differences, and the like, and the conditions of a transfer function and a compensation circuit are severe for high track density.

An object of the present invention is to provide a conversion element driving device in which the above-mentioned positional deviation is reduced and transmission characteristics are improved.

[Means for solving the problem]

The above object can be achieved as follows.
A servo head and a data head are mounted on the same slider. Here, the servo head is fixed on the slider, and the data head is configured to be movable relative to the surf head by a microactuator. At this time, the operating characteristics of the microactuator need to be in a wide band of 100 Hz to several tens kHz. On the other hand, the servo band of the coarse actuator has a crossover frequency of several hundred Hz to several kHz at the maximum depending on the size of the movable mass and mechanical characteristics such as friction of the bearing guide. For this reason, a configuration is adopted in which the coarse actuator is in charge of the access, and the micro-actuator is in charge of the settling vibration at the time of settling and the following following operation.

On the other hand, on the data surface, a pattern in which servo information is recorded one track at a time between data zones having a predetermined width is recorded on the medium. Alternatively, in a two-layer film medium, data information and servo information may be recorded on different layers, respectively. The latter is more promising in view of the efficiency of use of the medium surface.

[Action]

The servo head that has received the command to access the target track performs a positioning operation on the target servo track that covers the target data track zone according to a predetermined speed curve. When the servo head has settled to the target position, a command to access the target data track is also issued to the microactuator that moves the data head, and the data head receives the command by the operation of the microactuator based on the predetermined address information. High-speed, high-accuracy settling to the target data track. At the time of following, the servo head follows the servo track according to the transfer characteristic of the coarse actuator, and the data head follows the target data track according to the transfer characteristic of the microactuator.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a basic configuration of the first to third embodiments of the present invention. The servo head 1 is connected to the data head 2 via a fine movement microactuator 3, and these are mounted on one rigid body, for example, a slider 6. The slider 6 is connected to, for example, a VCM actuator 4 for coarse movement via a cymbal spring 7 or the like.
The VCM actuator 4 is directly attached to the housing 5 or a spring 9
Has been fixed through. The servo head 1 and the data head 2 are held at a predetermined interval from a storage medium, for example, a high-speed rotating magnetic disk 8. Here, the servo head 1 is fixed to the slider 6, but the data head 2 can move relative to the slider 6 and the servo head 1 by the fine movement microactuator 3. The desired value of the relative motion stroke is related to the servo information and data information patterns, which will be described below.

FIG. 2 is a diagram schematically showing patterns of servo tracks and data tracks on the magnetic disk 8. The servo tracks 9a, 9b, 9c are regularly arranged at predetermined intervals, and include a data zone including a fixed number n of data tracks.
10a, 10b are arranged between them. The width of the data zone is approximately n × p, where p is the data track pitch.
Is represented by This size is substantially equal to the stroke of the microactuator 3.

In consideration of improving the quality of the servo signal, it is more convenient to make the servo track width relatively wider than the data track width. In this case, since the servo area requires a large area, the efficiency of using the medium surface is deteriorated. Effective use of the medium surface will be described later in detail.

FIG. 3 is a block diagram of a two-stage coupled servo system according to the present invention. The target value X, the displacement of the data head 2 is Xs, the error is Xer, and the characteristic of the compensation circuit 31 for compensating the stability of the fine actuator is G _c1 (s). In the micro-actuator micro-actuator system, _assuming that the output is e _s and the compensation circuit 32 having the characteristic of G _c2 (s), the disturbance Fd added thereto, and the transfer function 33 of the _fine- movement micro-actuator are G _fine (s), Is Xf. On the other hand, the coarse actuator system has a compensation circuit 34 having a characteristic of G _c3 (s).
And the disturbance Fd 'added thereto and the transfer function 35 of the coarse actuator are G _coarse (s), the displacement by the coarse actuator is Xc. The output Xs can be expressed as the sum of the movement amount Xf of the data head by the fine movement actuator and the movement amount Xc of the servo head by the coarse movement actuator. With such a configuration, low-frequency fluctuations such as friction of the actuator and external vibrations can be suppressed by the control loop of the coarse actuator.

Further, for example, when it is required to follow a servo pattern track fixed on a medium surface such as a discrete medium, the coarse movement actuator can follow a low-frequency large-amplitude component which is a main component of the track eccentricity.

FIG. 4 (a) schematically shows the open loop characteristics of a conventional servo surface servo type actuator.
FIG. 7B schematically shows the open-loop characteristics of the coarse actuator according to the present invention, and FIG. 7C schematically shows the open-loop characteristics of the fine actuator according to the present invention. The transfer characteristics of the conventional actuator are such that a crossover frequency 41 of slightly less than 1 kHz has a phase margin of 50 ° or more. In the present invention, the actuator for coarse movement has characteristics close to those shown in FIG.
The gain of is kept high. On the other hand, the actuator for fine movement can have a crossover frequency 43 of several kHz and a phase margin of several tens of degrees. Low frequency range
If the actuator is assigned to the coarse actuator and the high frequency region is assigned to the actuator for fine movement, stable characteristics can always be obtained over a wide band. Therefore, by combining these characteristics (a) and (b), a servo system having a sufficiently large bandwidth can be designed.

FIG. 5 is a diagram schematically showing a slider portion of the first embodiment of the present invention. Servo head 51 is attached to slider 55
The data head 52 is mounted on a movable member 54 via an actuator 53 such as a laminated piezo element. The movable member 54 is supported by the actuator 53 and the shock absorbing material 56, and can move at right angles to the running direction of the slider, that is, the track direction. However, if the laminated piezo element as an actuator is of a size that can be mounted on the slider 55 by the method of this embodiment, the stroke is as small as several μm, and is about submicron due to mechanical vibration and the like. Although it is possible to absorb the positioning error described above, it is not suitable for accessing the data track or following eccentricity.

FIG. 6A is a diagram schematically showing a slider portion according to a second embodiment of the present invention. The servo head 61 is fixed on a slider 64, and the data head 62 is mounted on a microactuator 63. The microactuator 63 is a movable portion of an electrostatic linear motor made by a microfabrication technology using a semiconductor technology. With this actuator, a stroke of several mm can be obtained with a dimension of several mm square, so that it can be sufficiently used as an actuator for access.

FIG. 6B is a diagram schematically showing a slider portion according to a third embodiment of the present invention. The servo head 65 is fixed on a slider 68, and the data heads 66a, 66b, 66c,.
Are mounted on a microactuator 67 similar to the above. If the distance between the angle data heads is an integral multiple of the data track pitch, when one data head is settled to a predetermined track, the other data heads can be settled to the respective data tracks at the same time. . That is, the positioned data heads can be regarded as if they were all on one cylinder. Therefore, with this configuration, an improvement in throughput is expected.

FIG. 7 is a diagram schematically showing an example of a linear electrostatic motor used as the fine movement microactuator of the present invention. FIG. 7 (a) is a first example showing a cross section of a linear electrostatic motor. The servo head 71 is fixed to a slider 73 on a so-called stator portion 74 of the electrostatic motor or together with the stator 74. The data head 72 is formed on a so-called rotor part 75 of the electrostatic motor. The rotor 75 is connected to the slider 73 by a spring member 76 having appropriate rigidity. By storing the electric charges in the stator 74 and the rotor 75, the effective electric field area of the electrodes of the rotor 74 and the stator 75 changes due to the electrostatic force, and the rotor 72 moves while maintaining balance with the spring 76.

FIG. 7 (b) is a second example of the linear electrostatic motor, and is a view of the shape formed on the slider viewed from the front. The data head 77 is formed on a rotor 78 of an electrostatic motor that moves linearly along a guide rail 80, and a stator 79 is fixed on a slider. Electrode 78 formed on rotor 78
, Are electrodes 791,792, formed on the stator.
The phases are slightly shifted from 793,... By sequentially switching the polarities of the adjacent electrodes, so that the rotor 78
Moves. Such a structure can be formed at once with the magnetic head 77 by semiconductor technology.

FIG. 8 is a diagram showing one embodiment of an application method of the present invention. First, addressing a given data track 81
Is issued, the servo head accesses 82 to the servo track serving the zone including the data track while counting the cross track. After the servo head has positioned 83 on the servo track and settled while performing closed loop control, the data head calculates the distance from the position based on the servo head according to the predetermined address information and moves 84 to position, set, and settle. 85. In this method, the servo head is set to the servo track 83 and then the open loop control is performed first, which is not suitable for ultra-high track density.

FIG. 9 is a diagram showing another embodiment of the application method of the present invention. First, the address command to the specified data track
When 91 is issued, the servo head accesses the servo track that covers the zone containing the data track.
I do. The servo head positions 93 to the servo track,
After settling under closed loop control, the data head is moved 94 to a predetermined data track based on sector servo information or embedded servo information in the zone to perform precise positioning, and settled under closed loop control.

FIG. 10 is a diagram showing another embodiment of the application method of the present invention. First, the address command to the specified data track
When 101 is issued, the servo head accesses the servo track that covers the zone containing the data track.
102. Servo head is roughly positioned on servo track 1
03, and settle under closed loop control. At the same time, the data head accesses the specified data track.
Step 4 is performed, and precise positioning is performed while performing closed loop control based on sector servo information or embedded servo information in the zone, and settled.

FIG. 11 is a diagram schematically showing one example of a medium surface format applied to the embodiment shown in FIG. 9 or FIG. The recording information pattern includes a servo track zone 111, sector servo information 112, and a data zone 113 according to the present invention. At the time of access, the servo head counts the cross track of the servo track 111, so that the seek time is greatly reduced as compared with the conventional sector servo system.

FIG. 12 is a diagram showing the structure of another example of the medium applied to the embodiment shown in FIG. 9 or FIG. The structure is such that data 121 is recorded on the surface layer of the medium and servo information 122 is recorded on the lower layer. The servo tracks for each zone are also recorded on the medium surface layer 123. That is,
The servo track 123 is a track for the servo head to follow, and the servo track 122 is a track for the data head to correctly follow on the track.

FIG. 13 is a diagram showing another example of the structure of the medium applied to the embodiment shown in FIG. 9 or FIG. Only the data 131 is recorded on the medium surface layer. in this way,
Data information can also be recorded on the lower-layer servo information 132, and the efficiency of using the medium surface is good. FIG. 12 to FIG. 13
In the case of using the embedded servo system described in the drawing, it is necessary to change the write frequency of the data signal and the servo signal, and to select both signals read at a time by a filter circuit. The quality can be improved by changing the properties of the magnetic films of the data layer and the servo layer, for example, the coercive force and the saturation magnetization, and by appropriately setting the shapes and materials of the data head and the servo head, for example, the gap length and the saturation magnetic flux density. A good servo signal. As an example, the magnetic film of the lower servo layer should be smaller in coercive force than the magnetic film of the upper data layer, and the gap length of the servo head and the saturation magnetic flux density should be equal to the gap length of the data head and the saturation magnetic flux density. Use of a head / medium system having a larger characteristic than that of the above can provide a head / medium system having good characteristics.

In an apparatus in which media are stacked (stacked), a problem occurs in data surface servo. FIG. 14 is a diagram for explaining a problem of the data surface servo system in the stack device. Even if the servo head 141a is positioned at the predetermined servo track 142a, the other servo head 14a
1b and 141c are the servo tracks 142
It is not always the case that it is accurately positioned at b, 142c. If each head is on the same cylinder, the throughput is improved by reading information from each head at once. Therefore, even if the servo head position shifts, each data head only needs to be on the same cylinder. Therefore, even if the servo head is not positioned at the optimum position, it is sufficient that the data head is positioned at a predetermined track, and each servo head determines the position of the data head based on the amount of displacement of each servo head. , For each slider. At this time, if the amount of displacement of the servo head is within the movable range of the data head, the data head can be positioned. However, if the displacement is larger than the movable range of the data head, the data head cannot be positioned.

As another solution to the above-mentioned problem of the data surface servo method, as shown in FIG. 15, a first coarse movement actuator 151 is provided with sliders 156a, 156b floating above magnetic disks 157a, 157b, 157c. , 156c,..., The second coarse actuators 152a, 152b,
, And servo heads 154a, 154b, 154c,..., Fine movement actuators 153a, 153b, 1 provided on each slider.
The data heads 155a, 155b, 155c,... Are individually moved for each slider by the coarse movement actuators 152a, 152b, 152c,. The amount of displacement of each servo head is detected and immediately corrected by the second coarse movement actuator for each slider. At this time, the coarse movement actuators 152a, 152b, 152
c,... move only when the servo head is displaced. Or, a first coarse actuator 151,
, And fine movement actuators 153a, 153b, 153c,..., Respectively, are driven in a low frequency region, a medium frequency region, and a high frequency region, respectively. However, the circuit structure becomes complicated.

〔The invention's effect〕

According to the present invention, for example, the positioning accuracy of a stacked magnetic disk device with respect to a data track can be significantly improved, and an improvement in data access speed at a high TPI can be expected. This is an important technical factor for increasing the possibility of increasing the track density of the magnetic recording file, and greatly contributes to the high performance of the device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the first to third embodiments of the present invention, and FIG. 2 is a diagram schematically showing a basic configuration of a servo track and a data track write pattern of the embodiment of the present invention. FIG. 4 is a block diagram of a two-stage coupled servo system of the present invention, FIG. 4 is a graph showing open loop characteristics of each servo system, and FIG.
FIGS. 6 and 7 are diagrams schematically showing the configuration of a two-stage coupled servo system according to the first to third embodiments of the present invention, and FIG. 7 explains the structure and operation of the fine movement microactuator of the present invention. FIGS. 8 to 10 are schematic diagrams for illustrating a method of applying the embodiment of the present invention, FIGS. 11 and 12, and FIG.
FIG. 14 is a diagram schematically showing various examples of the servo and data track patterns of the present invention. FIG. 14 is a schematic diagram for explaining the problem of applying the present invention to a medium stack device, and FIG.
FIG. 1 is a configuration diagram of an apparatus for explaining an example of a method for solving the above problem. 1 ... servo head, 2 ... data head, 3 ... fine movement microactuator, 4 ... coarse movement microactuator, 5 ... housing, 6 ... slider, 8 ... disk, 9a, 9b, 9c ... servo Track, 10a, 10b… Data track zone, 31, 32, 34… Compensation circuit, 33… Transfer function of fine actuator, 35… Transfer function of coarse actuator, 41… Crossover frequency of conventional device, 43
...... Crossover frequency of the micro-actuator of the present invention, 51, 61, 65 ...... Servo head, 52, 62, 66a, 66b,
66c …… Data head, 53, 63, 67 …… Actuator, 5
5, 64, 68 ... slider, 71 ... servo head, 72, 77 ...
Data head, 74,79 …… Stator, 72,78 …… Rotor,
81,94,111… Address designation, 82,92,112… Access (cross track count), 83,93,113… Servo head set, 84,94,114… Data head seek operation, 85,
95,115… Data head setting, 101,123… Servo track, 102… Sector servo information, 122,132… Embedded servo information, 103,121,131… Data track, 141a, 141b, 1
41c, 154a, 154b, 154c, ... servo heads, 142a, 142b, 142
c: servo track, 151: first actuator for coarse movement, 152a, 152b, 152c,... actuator for second coarse movement, 153a, 153b, 153c, actuator for fine movement.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshinori Miyamura 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Hitachi Central Research Laboratory Co., Ltd. (72) Yoshifumi Matsuda, Inventor 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Tokyo Central Research Laboratory Co., Ltd. Inside the Central Research Laboratory (72) Inventor Takeshi Nakao 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) Reference Reference

Claims (8)

(57) [Claims] 1. A conversion element driving apparatus used in an information recording apparatus for reading or writing information using a conversion element which is arranged on a recording medium on which servo information is written and moves relatively to the recording medium, A conversion element for reading and writing data and a conversion element for reading servo information are mounted on one rigid body, and the data conversion element is configured to move relative to the servo conversion element. A conversion element driving device, characterized in that: 2. The recording medium according to claim 1, wherein the data track on which the information is recorded forms a recording data area with a fixed number of tracks, and a servo track on which servo information is recorded is arranged between each area. A conversion element positioning apparatus for positioning a data conversion element on a predetermined data track by using the conversion element driving device. 3. A servo device for positioning a data read / write conversion element on a recording data area on a recording medium, and a servo conversion for positioning on a servo track having servo information on the recording medium. An element, a data conversion element which is arranged in proximity to the servo conversion element and is relatively movable, and a rigid body on which the servo conversion element and the data conversion element are mounted, and for moving the rigid body. Coarse movement mechanism, first servo means for positioning and setting the servo conversion element on a predetermined servo track on the recording medium, and second servo means for positioning the data conversion element on a predetermined data track. A servo device comprising servo means. 4. A servo track including servo information is provided at a fixed track interval in the recording data area, the servo conversion element follows the servo track, and the data conversion element positions the target data track. 4. The servo device according to claim 1, further comprising means for relatively moving the data conversion element by a predetermined distance based on the position of the servo conversion element. . 5. A plurality of sector areas including servo information are provided in the recording data area, and the servo conversion element follows a servo track, and when the data conversion element is positioned at a target data track, the servo conversion element is used. 4. The servo device according to claim 3, further comprising means for positioning the data conversion element based on the positioning information divided into a plurality of sectors based on the position of the data conversion element. 6. At least the recording data area has a two-layer structure of a layer on which servo information is recorded and a layer on which data is recorded, wherein the servo conversion element follows a servo track.
4. The apparatus according to claim 3, further comprising means for positioning said data conversion element based on the servo layer positioning information with reference to the position of said servo conversion element when the data conversion element positions the target data track. The servo device according to item 1. 7. The data conversion element, which moves relatively to the servo conversion element, is relatively moved by a piezoelectric actuator using a piezoelectric element or an electrostatic motor using fine processing technology or semiconductor technology. The servo device according to any one of claims 1 to 6, characterized in that: 8. The servo device according to claim 1, wherein a plurality of said data conversion elements are mounted on said rigid body.