GB2199442A - Disk driving devices - Google Patents

Description

. C ' n 1,--./,/ 4 4 2 1 V, ' - 1 ij RISK DRIVING DEVICES The present

invention relates to disk driving devices. Disk driving devices are arranged to drive information recording disks consisting of disk-shaped base plates carrying information recording layers on the surfaces thereof to effect information recording or reproduction.

Previously proposed disk driving devices record and/or reproduce information by rotating a magnetic recording medium in the form of a disk (hereinafter called a magnetic disk), for example.

Disk driving devices in the form of "hard disk devices" are particularaly used in small-scaled, large-capacity systems. Such a hard disk device rotates at-high spaced magnetic disks each made of a disk-shaped hard material having magnetic recording layers on surfaces thereof, and with magnetic heads facing the surface of the magnetic disk to record or reproduce signals,thereon.

US Patent (Reissue) No. 32075 discloses a servo-control system. The system uses a data-masked servo sector including track centre line servocontrol data detected by a head to fix the position of the head according to one piece of servo information per one revolution of a magnetic disk. Since this servo- control system invites a decrease in the data recording length by an amount corresponding to the servo information, it is arranged to slightly slow down the revolution to adjust the head transport.

speed. This arrangement, however, may invite an unstable movement of the head and may increase the 6rrorrate. Additionally, since only one piece of servo information is provided in one cycle, it takes a time to detect the servo information after movement of the head.

2 1 USP 4 122 503 discloses another control system using a servo system in which the inner-most and outer-most tracks are used as particular servo tracks. This system is called "ID-OD system" an abbreviation of "inner diameter" and "outer diameter". In this system, the disk apparatus is arranged to first read the outer servo track and then effect fine adjustment to place the head at the centre of the track. Subsequently, the head is moved towards the inner servo track. In this operation, step pulses of the stepping motor in the head driving mechanism are counted, so that when the head reaches the inner servo track, the head positioning mechanism effects precise positioning to bring the head at the centre of the track. While the precise positioning is effected for each servo track, the positioning mechanism is informed of a correction amount necessary for finding the centre of the track. Obtaining the correction amount, the positioning mechanism is enabled to calibrate precise positions of respective tracks according to information about the number of step pulses required for movement between the outer and inner tracks and the fine step correction amount required in each servo track.

Further, the magnetic disk apparatus records information by saturation recording.

Saturation recording 2 is such that the current applied to each head for its information writing is larger than a current value which saturates the magnetization of the magnetized layer of the magnetic disk in one direction. The saturation recording enables new information to be written by "over-writing" which does not require erasure of old information on the disk before writing in the new information. This simplifies the head construction and enables an instantaneous il, k 1 changeover between reading and writing operations.

Therefore, a single track may be divided into multiple sectors so that reading and writing may be effected per each sector, and this contributes to the maximum use:of the recording surfaces without loss.

In order to write or read information on a magnetic disk, it is necessary to make a format in an information recording region on the magnetic disk. The format may be a known format called "floppy-like" format, for example, in which one cycle from first to fourth gap is divided into 32 sectors related to an exterior index signal EIN.

The exterior index signal EIN corresponding to the first gap is settled at a position where a predetermined count number is detected from detection of a first interior index signal IN1 which is supplied from a Hall element or other magnetic detecting means- upon detection of the rotational position of a pulse generating magnet 40 attached to a rotor of the DD motor 3. That is, when the count number is detected after detection of the interior index signal IN1, the exterior index signal EIN is applied to the host computer 26, and this position is regarded as being the beginning of the recording track T.

Such a format is usually formed in the recording regions except those having servo information recorded thereon before shipment of the system, and a formatting is effected by an end user when he-first uses the magnetic disk driving device having the magnetic disk therein to enable information writing in the data field of the format.

In an ID-OD or other system in which servo informationjs provided in limited tracks alone, the 1 positional control of the head is effected based on "ormation which is written in a the servo int relationship with exciting phases of a stepping motor -ing the magnetic head.

or other device for transport Therefore, if the stepping motor mis-steps for any reason, the formatting is written, erasing the servo information. If the formatting is once written over the servo information, the system cannot obtain the servo information thereafter, and cannot position the head accurately.

Further, disk driving devices known heretofore are arranged to detect the zero track of a magnetic disk, using a sensor or other mechanical means, or alternatively using a particular signal specifically written in the radial direction for zero track detection to inhibit rewriting in the region having the particular signal.

However, the use of such a mechanical means increases the manufacturing cost of the system because of the additional cost not only for the sensor and other parts but also because of the more difficult assembling process required by the more complicated zero track positional adjustment. The use of the particular signal to inhibit rewriting thereon necessarily requires a slow-down off the disk rotation to adjuct the transporting speed, and this causes an instability of the head assembly and an increase of the error rate. This problem also remains in the aforegoing USP Re. 32075.

It is therefore an object of the present invention to provide an improved disk driving device.

In the disk driving device to be described the servo information is never erased during formatting. The device also has an information recording disk enabling zero track detection without 1 1 2, 1 1 using a sensor nor particular signal for zero track detection.

The device uses a head position detecting method in which the servo information or other important information is never erased by overwriting on write protected regions, and in which the position of the head assembly on an information recording disk is detected by an electrical means alone without slowing down the rotational speed of the information recording disk.

According to one aspect of the invention there is provided a disk driving device including a rotationally driven information recording disk made from.a disk-shaped base plate and an inforamtion recording layer coated on a surface of the base plate for writing or rewriting information thereon and having tracks concentrically aligned about the rotation axis, and including a head assembly configured to trace said tracks to write or read information thereon, at least two recording areas among multiple recording areas formed with said information recording layer of the information recording disk include mutually related regions originally assigned with identical signals and mutually related regions originally assigned with different signals. The signal assignment involves signal erasure, and it is merely required to specify a particular region on the recording surfaces.

With this arrangement, the signals assigned to respective tracks in the mutually related regions (which may be identical in configuration) on two surfaces can be read by the head assembly, and the signals applied to the same cylinder are compared to each other so that the region in which the head assembly is located is readily specified. Therefore, 1 6 nst informaany reg--on to be -protected agai-. i-on ing can be d-'scrminated by an e'ec-,--.ica" means wr, -. - - 1 - -L in lieu of a mechanical means.

A disk driving device embodying the present invention will now be describedd, by way of example, with reference to the accompanying diagrammatic drawings in which:

Fig. 1 (a) is an explanatory view showing the regions of side I'V' of a magnetic disk; Fig. 1 (b) is an explanatory view showing regions of side "0" of the magnetic disk; Fig. 2 (a) is an explanatory view showing a detail of side I'V' of the magnetic disk; Fig. 2 (b) is an explanatory view showing a detail of side "0" of the magnetic disk; Fig. 3 is a block diagram of a control system of the disk driving device; Fi.g. 4 is an explanatory view showing recording tracks and a configuration of written servo information oil side "1'I ot the magnetic disk; Fig. 5 is a block diagram of the servo circuit of the device; Fig. 6 is a bottom view of the disk driving device to explain index detection.

Fig. 7 is a fflow chart of a seek control of the disk driving device; Fig. 8 is a flow chart of a process of zero track restoration; and Fig. 9 is a fragmentary perspective view of' a previously proposed disk driving device which is partly cut out to expose its interior structure.

The previosuly proposed hard disk device shown in Fig. 9 includes a plurality of magnetic disks 1 on which information is recorded, magnetic format.

heads 2 which record or reproduce in- ion on or - 7 e i;.

P 7 1 --from the magnetic disks 1, a direct drive motor (not shown. Hereinafter called "DD motor") which drives the magnetic disks 1, a head driving mechanism 4 which moves the magnetic heads 2 to predetermined tracks on the magnetic disks 1, a support board 5 which supports a housing sealingly accepting therein the magnetic disks 1, the magnetic heads 2 and other members, a printed board 6 on which a motor driving circuit, control circuit, etc, are printed, and a frame (not shown) which holds the printed board 6 on the support board 5.

The illustrated magnetic disk device includes two magnetic disks 1. Each magnetic disk 1 has two recording surfaces on opposite planar surfacas thereof. Therefore, the illustrated disk mechanism includes four magnetic heads 2 associated with respective recording surfaces of the magnetic disks 1. The magnetic heads are mounted on a swing arm 8 of the head driving mechansim 4 by cantilever springs. The head driving mechanism 4 consists of the swing arm 8, a steel belt 9 mounted on a part of the swing 'arm 8, a pulley 10 on which an intermediate portion of the steel belt engages, and.a stepping motor 11 which has a drive shaft 12 supporting the pulley 10 combined with the steel belt 9, so that when the stepping motor 11 is driven, the swing arm 8 swings about a pivot pin 8a thereof.

The magnetic disks 1, the magnetic heads 2, the swing arm 8, the steel belt 9 and the pulley 10 are accommodated in the easing which consists of the support board 5and a top cover (not shown). To establish an airtight sealing of the housing, gaskets are used at the contact between the support board 5 and the top cover and at the mounting portion of the stepping motor 11. Further, magnetic flui-d is applied around the shaft of the DD motor for the same Q purpose. The swing arm 8 is provided with a shutter 171 extending outwardly away from the magnetic heads 2. Nearer to an airtight chamber of the support board 5 is provided a photo interrupter 18 serving as an outside sensor. The photo interrupter 18 defines an insertion path 18a which receives the shutter 17 loosely. When this magnetic head 2 reaches a zero track position at an outermost circumference, the shutter 17 blocks the light path provided in the insertion path 18a of the photo interrupter 18.

In the arrangement using the stepping motor 11 to transport the magnetic heads 2, the head 4 positio=g is difficult when the track density of the disks is increased. More specifically, since different materials in the hard disk apparatus have different expansion coefficients, there occurs a problem called "thermal off-track" in which the position of the magnetic head 2 relative to the tracks varies with temperature. Therefore, in a 13-33 cm (5.25 inch) type hard disk apparatus, it is difficult to precisely position the magnetic heads 2 beyond 400TIPI unless a servo system is used.

In the disk driving device shown in Figs. 1 to 8 parts similar to those shown in Figure 9 are similarly referenced.

The control system for the disk driving device shown in Figure 3 includes a DD motor 3 for rotating a magnetic disk 1 and a stepping motor 11 piVot4 for Lng a swing arm 8. The control system comprises a driving circuit 22 for signal transmission and reception with respect to a head amplifier 21, a servo circuit 23 which processes servo information detected by the magnetic head 2 and amplified by the head amplifier 21 to supply the driving circuit 22 with an electric signal to effect 4 j servo control, and a controller 25 which controls the driving circuit 22 via an interface 2A. The controller-215 is connected to a host computer 26 by a bus 27 to enable signal proce'ssing of a signal detected by the magnetic head 2 or a signal to be transmitted to the magnetic head 2. - FigUres 1 and 2 show various areas provided on the magnetic disk 1. The magnetic disk 1 comprises an aluminium. plate having a magnetic coating. The magnetic disk 1 has an inhibit zone I and a data zone D. The inhibit zone I is located at a radially innermost position of the magnetic disk 1 and -no data is written on it. The data zone D is located at a radially outer position of the inhibit.zone I and has about six hundred recording trekcks T aligned concentrically. The data zone D is divided into three regions D1, D2 and D3 each having in a central portion thereof a group of servo tracks STG1 (STG2 or STG3) in which four tracks as.shown in Figures 2(a) and 4 form one group. In the servo track groups STG1 through STG3, servo zones SZ1 and SZ2 are provided on which servo signals F are written as servo information at 180 degrees interval.

Figure 4 shows the servo track group STG1. In the same drawings, the servo track group STG1 includes four servo tracks ST1, ST2, ST3 and ST4 on each of which the servo signal F is written alternatingly at a uniform frequency and in a zigzag configuration at positions equally distant from a centre line.C in the length (circumferential) direction, in a relationship with first and second interior index signals IN1 and IN2. They serve as the aforegoing se.rvo zones SZ.1 and SZ2. In this case, since the servo signals P are written by a -si - ngle magnetic head 2, the widths of the servo 1 i 1 5 signals F, the recording tracks T' and the servo 4-racks through ST U L4 coincide with the length of a gap G of the magnetic head 2. An off- track phenomenum occurs when the position of the gap G of the magnetic head 2 deviates from a desired recording track T.

In this embodiment, 180 degrees phase difference is provided between the servo zones SZ1 and SZ2, considering the time required for positional correction of the magnetic head 2 and the time required for one revolution of the magnetic disk 1 More specifically, the time required for one revolution of the magnetic disk 1 is about 16.67msec at 3600 rpm, and the time from energization to deenergization of the stepping motor 11 is about 8msec. Therefore, with the 180-degree phase difference in the servo zones, it is possible to correct the position of the magnetic head by detecting the servo signal F in the servo zone SZ1 associated with the first interior index signal IN1, for example, and immediately after the termination of the correcting operation, it is possible to confirm whether the correcting operation is adequate or not, by detecting the servo signal F in the servo zone SZ2 associated with the second interior index signal IN2. In this case, since the time for one revolution of the magnetic disk 1 has the aforegoing relationship with the energized duration of the stepping motor 11, two servo zones are provided in one cycle at 180 degrees interval. However, according to the type of stepping motor or other driving motor employed and the type of recording medium employed they may be modified, considering the time taken for the positioning motion by the motor and the revolution of the recording medium. Whatever motor or recording j - 11 4 1 medium is employed, the system will sufficiently function with one to several servo zones per cycle.

Further, in the disk driving device, since the servo zones SZ1 and SZ2 are formed at 180 degree intervals, the same phase difference is also required in the first and second interior index signals IN1 and IN2. In this connection, as shown in Figure 6, for example, a magnet 40 (hereinafter called 11PG magnet") serving as a pulse generating means-is provided at an outer circumferential portion of a rotor 3a of the-DD motor 3, so that a magnetic change in the PG magnet 40 is detected by coils, Hall elements, or other detecting means 41a and 41b (hereinafter called 11PG sensor"), for example, provided near the outer circumferential portion of a rotor 3a of the DD motor 3 and symmetrically opposed to each other about the rotation axis of the DD motor 3, in order to use detection pulses as the first and second interior index signals IN1 and IN2.

Four servo tracks form one group for the reason explained below.

In the stepping motor 11, rotating angles in individual steps are not completely uniform due to presence of errors in distances between the magnetic pole teeth or between the magnetized portions of the rotor. Therefore, when a stepping motor of the fourphase unipolar type or the two-phase bipolar type is used, one cycle is established by eight steps totalling four steps in one-phase excitation and four steps in two-phase excitation. It is recognized that errors in the rotation angles by the exciting phases in individual half revolutions exhibit a uniform pattern. Therefore, by arranging to correct the rotating angles of four tracks in a half cycle, maintaining-a close relationship between the rotating i - 12 angle and an exciting voltage, the same control factor also applies to every other four recording tracks.

Figure 4 also shows guard tracks GT provided radially inwardly and outwardly of the servo track group STG1. Individual guard tracks GT and servo tracks ST1 through ST4 include dummy tracks D1. having no servo signals F recorded thereon and are never used as a data region. In Figure 4, reference symbol EIN denotes an exterior index signal. When the first index signal IN1 is detected, as described above, counting is commenced, and when a pre-,'etermined counting number is detected, the exterior index signal EIN is transmitted to the host computer 26. The exterior index signal EIN is used as an index for writing or reading on the recording tracks T in the data zone D.

Radially outside the data zone D, i.e. in the radially outer position than the zero track OT located at the outermost circumference of the data region D3 is provided an outer guard band OGB on which no data is written, i.e. no inverse- magnetized region is formed. Therefore, the magnetic disk 1 is divided into five annular regions of inner guard band 1, first data region D1, second data region D2, third data region D3 and outer guard band OGB in this sequence from the centre thereof. Further, the servo regions STG1, STG2 and STG3 occupy central annular portions of the data regions D1, D2 and D3, respectively. All these regions are concentric about the centre 0 of the magnetic disk 1. Among them, the servo regions STG1, STG2 and STG3 and the outer guard band OGB are write protect regions whereas the first, second and third data zones D1, D2 and D3 are read/write regions on which information is recorded.

1 1 - 13 Since the inner guard band I does not require writeprotection nor is used to read or write signals, it is clearly distinguished from the write protect regions if some signal is written thereon.

The regions having no servo signal F written thereon among the servo regions STG1, STG2 and STG3 and the outer guard band OGB are originally DC-erased as being write-protect regions, and inverse magnetization is not formed thereon on one recording surface la, e.g. side 11111 of the magnetic disk as shown in Figures 1(a) and 2(a).

In contrast, in the data regions D1, D2 and D3 which is the read/write region excluding the servo regions STG1, STG2 and STG3 and the inner guard band I, predetermined signals are originally written, and inverse magnetized regions are formed continuously.

On the other hand, at least one recording s rface 1b, e.g. side 11011 of the magnetic disk 1 is divided into identical regions as those of the recording surface la as shown in Figures 1(b) and 2(b), and no servo signal F nor other signal is written in-the servo regions STG1, STG2 and STG3 nor in the inner guard band I whereas some signal is written in the data-regions D1, D2 and D3 and in the outer band OGBi The signal written on the recording surface lb corresponding to side 11011 may be identical, i.e. identical in frequency to that written on the recording surface la corresponding to -Perent, i.e.

side 11111 or-alternatively it may be dif.

different in frequency from same.

14 - TABLE 1: PRESENCE OR ABSENCE OF DATA ON REGIONS 1 Side "1" (1a) Presence or Present Absent Absence of data Side 11011 Present Data Zone OGB (1b) Absent Servo Region Therefore, when the signal-written regions are selected in the aforegoing fashion, these regions are clearly distinguished by detecting the relationship between the recording surface la of side "111 and the recording surface 1b of side "0" regarding presence or absence of data as shown in Table 1. If the disk driving device is configured to drive two- disk arrangement, side "0", side "2" and side "Y' may be used as the recording surfaces 1b so as to use side I'l" alone as the recording surface la.

With this arrangement, the disk driving system operates as follows.

This type of disk driving system exhibits a relativey large temperature variation between its dormant and activated conditions. The magnetic disk 1 is thermally expanded with time after power supply to the disk driving device, and the thermal expansion causes a thermal off-track. The amount of expansion gradually increases soon after the power supply, and reaches a substantially constant value in 35 minutes approximately.

In this connection, just after a power is entered in the disk driving device, the magnetic head 2 first scans the surface of the magnetic disk 1 to memorize in the RAM --,f the driving circuit 22 the electrical amount concerning exciting phases of the v' Q J1 25.

stepping motor 11 corresponding to respective recording tracks T, and thereby makes the RAM table. Additionally, a positioning correction system considering an increase of the temperature is, originally stored in a microcomputer so that recording or reproduction is performed in accordance with the servo algorithm stored in the microcomputer. More specifically, if the microcomputer gives the driving circuit 22 a servo instruction based on the aforegoing servo algorithm while recording or reproduction of a desired recording track is performed by energization of a predetermined exciting phase indicated by the RAM table, the magnetic head 2 is moved from a recording track T1 (or T5) for example, to a servo track ST1 of Figure 4, for example, in the same exciting phase as the recording T1 (T5) and in a servo zone ST. If the magnetic head 2 is heretofore located at the recording track T2 (T6), it is moved to the servo track ST2. Similarly, if the recording track is T3 (TV or T4 (T8), the servo track will be ST3 or ST4, respectively. In this embodiment,. one dycle of the stepping motor 11 consists of eight steps. Therefore, one servo zone has four trackscorresponding to the number of steps per half cycle of the stepping motor 11. When other form of the stepping motor 11 or other control system is,employed, the number of servo tracks will be changed accordingly.

Assuming that the same exciting phase is energized by the same current value, and the gap G of the magnetic head 2 located at position A in Figure 4 detects a servo signal F, a difference arises between the level of aprecedingly detected servo signal and the level of a subsequently detected servo signal. In this connection, sample holding circuits 38 and 29 3 0 16 of the servo circuit 23 discr 4 minate the signals, and a comDarator compares their signal levels. A servo am-plifier 311 determines a current value for supply to the exciting phases of the stepping motor 11 in accordance with the comparison result to control the stepping motor 11 via the driving circuit 22. In this fashion, the gap G of the magnetic head 2 is moved to position B (Figure 4) which is symmetrical about the centre line 0, and the fine track position is fixed with respect to the servo track S'Ll.

Just after the movement of the magnetic head 2 is terminated, a servo signal F in the second servo zone SZ2 is detected for the aforegoing reason to judge in the second servo zone SZ2 whether the movement is adequate or not. More specifically, if an output from the comparator circuit 30 in the second servo zone SZ2 is lower than a predetermined level, the present movement condition is maintained.

However, if the output is higher than the predetermined level, the stepping motor 11 is driven again to effect the same positional control to bring the magnetic head 2 to a precise track position, i.e. the fine track position.

A current value supplied to an exciting phase of the stepping motor 11 on arrival to the fine track position is stored in the RAM of the driving circuit 22, and the magnetic head 2 returns to its original track T1, referring to the aforegoing RAM table, so that the position of the gat G with respect to the recording track T1 is fixed by the current value stored in the RAM. In this fashion, the fine track position is established also in the recording track T1. In the disk driving device arranged to effect such a servo correction, the DD motor 3 begins - 1 ' 1 7 4 1 its rotation when power is entered, and the magnetic disk 1 rotates responsively. With this rotation, the magnetic head 2 floats at the innermost inhibit zone I, once goes to the outermost zero track OT to confirm the track position, and subsequently'moves to the inputted recording track T.

At this time, there is a possibility that the stepping motor might erroneously step-to the servo track ST which requires write-protection, and that the servo signal F is erased when a write signal is entered, so that servo correction is inhibited thereafter. To avoid this, a control method as shown in the flow chart of Figure 7 is employed.

More specifically, when the driving circuit 22 receives a step pulse from the host computer 26, the seek completion is turned OFF, and the stepping motor 1 is driven to activate the magnetic head 2 for its seeking operation. After the seeking operation is effected, it takes a certain time, i.e. a settling time for the magnetic head 2 to take a stable position in the target recording track,T either in a buffer mode seeking or in a normal'mode seeking. In this connection, it must be confirmed whether the time required at least for the settling has passed or not after the final step. Additionally, after it is confirmed that the settling has been completed or not, it is confirmed that the magnetic head 2 is located in the recording track T of the data regions D1, D2 and D3 or not. This is judged according to whether the magnetic head 2 has detected or not any signal from the recording surface lb of side 11011 of themagnetic disk 1. That is, it is effected by detecting presence or absence of an output from the head 11011 associated with the recording surface lb of side 11011.In absence of-an output from the recording - 18 1 -p surface 1b of side "0" it is meant that the magnetic Y U head 2 is located in one of the servo regions STP, STG2 and STIG3 or in the inner guard band I as will be understood from Figures 1 and 2, and the system deems it to be a seek error and proceeds to an error routine. In the error routine, the magnetic head 2 is moved back to the zero track OT and subsequently moved to the target track to repeat the seeking operation, for example. This treatment is appropriately performed according to a predetermined algorithm and according to the nature of the error.

In presence of an output from the magnetic head 2 on the recording surface 1b of side "0", it is deemed that the magnetic head 2 is located in one of the data regions D1, D2 and D3 or in the outer guard band OGB, and it is judged whether the magneti'C head 2 has detected any signal from the recording surface la of side "1" of the magnetic disk 1. This is judged according to presence or absence of an output from the head "V' associated with the recording surface la of side "1". In absence of an output from the recording surface la of side Ill", it is deemed that the magnetic head 2 is located in the outer guard band OGB as will be understood from Figures 1 and 2, and the system proceeds to a zero track restore routine (described later) to perform zero track restoration and subsequently seek to the target track. In presence of an output from the head Ill", it is meant that a magnetic inversion has occurred.

Therefore, it is deemed that the magnetic head 2 has seeked to the target track of the data regions D1, D2 and D3. That is, it is deemed that the magnetic head 2 has reached the desired track without mis-step.

Accordingly, a seek complete signal is turned on to perform a desired reading or writing.

- 19 f i 1 With this control method, the servo signal F is never erased from the servo tracks ST1 through ST4 while an end user performs the formatting.

Therefore, it data is originally written on the recording track T of the data regions D1, D2 and D3, either signal including a formatting signal necessarily remains on the data regions D1, D2. and D3 after formatting, so that the aforegoing servo control is reliably effected after the formatting as well.

In the aforegoing embodiment, the servo signal F alone is written in the outer guard band OGB. Therefore,_the--zero track OT can be detected by detecting the recording track position adjacent the innermost circumference if the write-protect region having no signal thereon. A process of the zero track restoration is shown in Figure 8 and briefly explained below.

In the described embodiment, the magnetic head 2 is driven by the stepping motor 11, regarding the position of a predetemined exciting phase as the zero track OT. Since the stepping motor 11 has eight steps in one cycle as described above, zero track restoration is performed, regarding eight steps as one unit.

-More specifically, when a zero track restoration instruction is entered into the driving circuit, an exciting phase of the stepping motor 11 corresponding to a track (8N-2 track. N is an integer) located two tracks further out than an exciting phase corresponding to the zero track OT is excited first, and it is judged whether an output is produced or not from the magnetic head 11011 and the magnetic head 11111 corresponding to the recording surface lb of side 111" and the recording surface la of side "1" of the magnetic disk 1. At this time, if an output is detected from the head "0" but not from the head "V', it is considered that the magnetic head 2 is located in the outer guard band OGB. To confirm this, the magnetic head 2 is moved to seek inwardly by eight tracks and reliably positioned in the data region D3.

When an output is detected from both heads "0" and "V', it is deemed that the magnetic head 2 is located in one of the data regions D1, D2 and D3, and the head 2 is moved outwardly to seek every eighth track, acknowledging outputs from the head "0" and 11111 in every eighth track and finally located in the zero track OT within one cycle of the stepping motor 11. At this time, since the exciting phase corresponding to the track (8N-2) alone is excited, the magnetic head 2 is located in the outer guard band OGB which is two tracks further out than the zero track OT. In this fashion, after positional fixture in the zero track OT within one cycle of the stepping motor 11, the exciting phase is changed to position the magnetic head 2 in the (-1) track which is one track further out than the zero track OT. Subsequently, by exciting the exciting phase corresponding to the zero track OT and controlling the current value to be supplied to the exciting phase, the magnetic head 2 is positioned in the zero track OT. Upon completion of the positional fixture in the zero track OT, a zero track signal is supplied to the controller to complete the zero track restoration.

In the zero track restoration, the magnetic head 2 is reliably precisely positioned within one cycle of the stepping motor 11 and brought to the zero track OT by merely detecting an output from the 41 1 1 f 1 - 21 heads "0" and fflff, and it is not required to use information particularly written for the zero track restoration nor to use any mechanical detecting means.

The (8N-2) track is selected in the zero track restoration for the following reasons. That is, when the magnetic head 2 is located in the outer guard band OGB, it takes the (-2) track position, and the nearer it is to the zero track OT, the less mis-step occurs in the final step.

Additionally, this contributes to a speed-up of zero track restoration.

If the (-1) track is selected, the head 2 may detect any undesired signal, and it is compelled to confirm the presence or absence of signal aTter settling. Obviously, this slows down the speed of the zero track restoration.

As described above, the embodiment has the following advantages.

(1) The recording surfaces la and lb of side "I" and side 11011 of the magnetic disk 1 is divided into identical regions of the outer guard band OGB, data regions D1, D2, D3, -servo regions STG1, STG2, STG3 and inner guard band I, so that these regions are readily identified by detecting signals written (or not written) in the respective regions. Therefore, if wr ite-protection is. established in the outer guard band OGB and in the servo regions STG1, STG2, STG3, information is never written in the write-protect regions and never erases the servo information.

(2)-For the same reasons, the zero track position is reliably detected also in absence of a sensor or a particular signal written for the zero track detection.

- 22 (3) Since the servo signals F are not provided in the radial direction of the magnetic disk 1, the rotaltion speed of the magnetic disk 1 need not be slowed down, and this contributes to a stability of the magnetic head 2 and to a decrease in the error rate.

(4) If a mis-step occurs, it is not necessary to resume the positional correcting operation from its initial step as in the ID-OD system. Therefore, it ensures a significant time saving and an efficient operation.

(5) Since the head '1111 alone of the magnetic head assembly 2 is used to detect the servo signal F, it is not necessary to change heads in the magnetic head assembly to detect the servo signal F as in the prior art system in which servo signals F are written in respective magnetic disks 1. Therefore, waiting time for settling after a head changeover is omitted, the servo control circuit is simplified, and the servo control time is reduced.

As descrbed heretofore, according to the invention which prepares mutually related regions on at least two surfaces among multiple recording surfaces of an information recording disk and originally assigns signals to these regions, it is possible to discriminate these regions by detecting these signals. Therefore, write-protect regions can be clearly discriminated by an electrical means alone, and servo information originally written on the write protect regions are never erased by erroneous information writing. Further, since an originally written data can be used to detect the boundary between the write-protected outer guard band and the data region available for the read/write 35) region, the zero track position which is the - 23 m outermost circumference of the data region is detected without using a particular sensor or other mechanical means and without originally writing a particular signal for zero track detection. Beside this, since any positional detection information or the like need not be originally written in the radial direction of the magnetic disk, it is not necessary to slow down the rotation speed of the information recording disk upon positional detection of the magnetic head, and the error rate in information recording or reproduction is significantly reduced.

i 1 1 f.

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Claims (12)

C L A I Ms'

1. A disk driving device comprising a rotary information recording disk having a disk-shaped base plate and a plurality of recording surfaces formed on a surface of the base plate for writing or rewriting information thereon, and a head assembly for tracing tracks on the recording surfaces to write or read signals thereon, at least two of said plurality of recording surfaces on said information recording disk, each being provided with mutually related regions originally assigned with identical signals and mutually related regions originally assigned with different signals.

2. A disk driving device according to Claim 1 wherein said regions are a read/write region for reading or writing signals thereon and a write protect region on which no signal is written.

3. A disk driving device according to Claim 2 wherein said write-protect region includes a servo region consisting of a group of tracks having track centre position for correcting information written thereon and an outer guard band consisting of a group of tracks located radially outside the outermost track of said read/write region, and wherein said read/write region consists of a data region.

4. A disk driving device according to Claim 3 wherein signals are erased in said tracks of said servo region provided in one recording surface except portions having said track centre position correcting information written thereon and in said tracks of said outer guard band, whereas some signals are originally written on all tracks of said data region, and wherein signals are all erased in said tracks of said servo regions provided on the other recording surfaces, whereas some signals are originally written i - 25 on all tracks of said data regionand said outer guard band.

5. A disk driving device according to any preceding claim-wherein said two recording surfaces are selected from a single information recording disk.

6. A disk driving device according to any one of Claims 1 to 4 wherein said two recording surfaces are selected from different information recording disks.

7. A head position detecting method comprising the steps of selecting at least two recording surfaces among a plurality of recording surfaces on a plurality of information recording disks; sectioning said two recording surfaces into predetermined mutually related regions; assigning predetermined signals including signal erasure to respective regions; and detecting a region in which a head assembly is located according to a signal detected from.at least one region of said recording surfaces.

8. A head position detecting method according to Claim 7 wherein said sectioned regions are a read/write region and a write-protect region.

9. A head position detecting method according to Claim 8'wherein said write-protect region includes a servo region consisting of a group of tracks having s-ervo signals written thereon and an outer guard band located radially outside said-read/write region.

10. A head position detecting method according to Claim 9 wherein signals are erased in said tracks of sai d servo region provided on one recording surface except portions having said track centre position correcting information written thereon and in said tracks of said outer guard band, whereas some signals are originally written on all tracks of said 26 i data region, wherein signals are all erased in said tracks of said servo regions provided on the other recording surfaces, whereas some signals are originally written on all tracks of said data region and said outer guard band, and wherein signals are read first from said other recording surfaces, signals are read subsequently from the same cylinder of said one recording surface, and a region in which the head assembly location is detected according to both detected signals.

11. A disk driving device substantially as hereinbefore described with reference to Figures 1 to 8 of the accompanying drawings.

12. A head position detection method substantially as hereinbefore described with reference to Figures 1 to 8 of the accompanying drawings.

Published 1988 at The Pwe.-, Of5ce, State House 66 71 High Holborn, London WClR 4TP Further copies may be obtained from The Patent Of4ce. Sales Branct. St Ma-7 Cray, Orpington, Kent BR5 3RD Printed by Multiplex techxuques ltd. St Mary Cray, Rent Con. 1/87