JPH0750521B2 - Track erasing method for magnetic recording / reproducing apparatus - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to track erasing in a magnetic recording / reproducing apparatus using a recording medium having a plurality of concentric recording tracks.
Furthermore, the present invention relates to a method of erasing tracks only with a recording / reproducing head without a dedicated erasing head.

[Background of the Invention]

An electronic camera that records and reproduces video signals using a flexible magnetic disk with an outer diameter of approximately 50 mm has a track pitch of 100 μm.
Fifty tracks with a width of approximately 60 μm are recorded concentrically for each m. The radius of the outermost track is 20 mm. The electronic camera has a head for recording / reproducing with a gap width of about 60 μm, and does not have an erasing head. Therefore, in this type of apparatus, a track is formed by recording a signal on an unformatted unrecorded disc in order of 100 μm from the outer periphery. The formed track position relatively changes due to the difference between the recording and reproducing devices and the expansion and contraction due to the temperature and humidity of the disc, and reaches a maximum of ± 20 μm. Therefore, the overlapping amount of the track and the head, that is, the track width reproduced by the head is 60 μm at the maximum and 20 μm at the minimum. In such a state, when erasing the previously recorded track and recording on it, the unerased portion will always occur, and when reproducing such a track,
Since there is a high probability that the newly recorded signal and the unerased portion will be reproduced at the same time, the signal quality was poor with the S / N ratio. By the way, it is said that the S / N ratio of electronic cameras must be 40 dB or more. Since the track width is 60 μm, 1/100 of that
Only the following unerased amount is allowed. Therefore, in the conventional electronic camera system, it is impossible to erase in track units, and in the case of erasing, it is performed in disk units. The electronic camera puts one field image on one truck,
A frame image is composed of two tracks. Therefore, one disc has 25 frame images.
You can put 50 sheets or 50 sheets in the case of field images. When editing this disc, it was a task to prepare another new disc and fill in the desired pictures in order, and the S / N ratio deteriorated due to the analog signal, and the work was difficult.

Further, as a method of erasing a widely recorded track with a head having a narrow width, there is a method disclosed in Japanese Utility Model Publication No. 56-136317. This is a method in which a head is moved slightly in the width direction of a track in which a wide track is written, and then erased little by little. It is clear that this method covers the first written track by moving the head slightly before and after the position of the first written track is constant and known. However, in a floppy disk drive device in which the disk expands and contracts due to temperature and humidity, eccentric every time chucking occurs, and the head positioning is also open loop, the initial track position changes, and therefore its position is unknown. Therefore, according to the conventional example, erasing the tracks of the floppy disk leaves an unerased portion, and the tracks cannot be completely erased.

[Object of the Invention]

It is an object of the present invention to provide a track erasing method for erasing a track that has already been recorded by using a recording / reproducing head without erasing.

[Outline of Invention]

In order to achieve the above-mentioned object, the outline of the track position which has already been written is discriminated by a predetermined discriminating means, and the position and three points before and after the position, or the position and a predetermined amount in one direction from the position. The head is moved to three points where the head is offset, and an erase current is applied to the head at each point,
This is a method of erasing by covering the front and back of the track.

[Embodiment of the Invention] The operation principle of one embodiment of the present invention will be described below with reference to FIGS. 1 to 5. 1 to 5 are explanatory views showing changes in relative positions of the track and the head. Data track recorded on the disc
The head 30 moves in the direction of arrow A with respect to the head 31. The head 31 is dynamically fed by a stepping motor (not shown) to position the head 31 on the target data track 30. However, the disk expands and contracts due to temperature and humidity, and is eccentric due to chucking error because it chucks on the shaft of the disk motor (not shown),
The position of truck 30 was changing. On the other hand, since the feed mechanism of the head 31 also has processing accuracy, it is not always possible to feed the head 31 to the ideal track center.However, the processing accuracy of the feed mechanism is improved so that the head 31 can be positioned to a position where it is practically used to some extent. ing. Therefore, the data track position is positioned with a certain error due to the expansion and contraction and eccentricity of the disk and the accuracy of the header feeding mechanism, and the data track 30 is recorded and reproduced. Although this error is called a head positioning error, an upper limit is set for this head positioning error in order to guarantee disk compatibility. That is, in the case of a recording / reproducing apparatus for an electronic camera having only one head for recording / reproducing, the head
The range in which 31 can be positioned is the boundary 27, 28 between adjacent tracks, that is, the middle point between tracks. This is because if the head is positioned beyond the midpoint, the signal of the adjacent track is reproduced and the S / N ratio deteriorates. Thus, the head positioning error D limit, permitted in other words the head positioning error, the track pitch Pt, the head width as W _H, is given by _{± D = (Pt-W H} ) / 2. In the case of an electronic camera, Pt = 100 μm and _WH = 60 μm, so D
= (100-60) / 2 = 20 μm. Further, there is Pt / 2 = 50 μm from the ideal track center CL to the boundary between adjacent tracks.

FIGS. 1 to 5 show how the position of the data track 30 changes with respect to the ideal track center CL in five stages. Further, the position of the data track 30 is in the state shown by B in FIG. 1, and the position of the head 31 is also represented in five stages representing the variation from the left boundary to the right boundary. The case where the data track 30 and the head 31 move with respect to the ideal track center CL is shown by the head 31 at the position B in FIGS. 1 to 5. Each case is numbered from 1 to 25.

The head 31 shown in FIGS. 1 to 5 has an initial position B.
On the other hand, the outer peripheral side is slightly stepped by the allowable off-track amount D to be the position A, and similarly, the outer peripheral side is slightly stepped by the allowable off-track amount D to be the position C. With respect to the initial position B of the head 31 in cases 1 to 25, the head positions A and C moved by the distance D to the inner and outer circumferences are shown.

FIG. 6 is a block diagram of a head controller when the present invention is implemented. The recording / reproducing switching circuit 32 is switched to the reproducing side by a command from the microcomputer 36. Recording and reproduction of the signal is performed by the head 31, the reproduced signal is amplified by the amplifier 33, the envelope of the carrier signal is detected by the FM detection circuit 34, and converted into a digital signal by the A / D converter 35,
The microcomputer 36 stores the signal level and compares the levels, and issues a head movement command to the best head position to the step motor drive circuit 37. The step motor 38 is applied with the number of pulses corresponding to the command and the step motor 38 is applied. 38
And the step motor 38 steps the head 31 inward or outward by the allowable off-track amount D.
FIG. 7 shows an algorithm of the magnitude comparison discrimination in the microcomputer 36. First, a distance D (allowable off-track amount) is moved from the initial position (B) of the head 31 to the outer peripheral side to be the position (A). Position storing the signal level (V _A) at (A). Next, the head 31 is moved to the position (C) by a distance D from the position (B) to the inner circumference side. Position storing signal level (V _C) at (C). The stored signal levels (V _A ) and (V _C ) are compared, and when the signal level (V _A ) is large, that is, cases 2, 3, 4, 5, 8, 9 in FIG. 1 to FIG. , 1
In the case of 0, 14, 15, and 20, the head 31 is moved to the position (B) for erasing, then the head 31 is moved to the position (A) for erasing, and the head 31 is further on the outer peripheral side from the position (A). Move a distance D to and erase. When the stored signal levels (V _A ) and (V _C ) are compared and the signal level (V _C ) is large, that is, cases 6, 11, 12, 16, 17 in FIGS. , 18,21,22,23,
In the case of 24, the head 31 is moved to the position (C) for erasing, and the head 31 is moved a distance D toward the inner peripheral side from the position (C) for erasing,
Further, the head 31 is returned to the position (B) to erase it. In the comparison of the above signal levels (V _A ) and (V _C ), if they are equal, that is, case 1 in FIG. 1 to FIG.
In the case of 13, 19 and 25, the head 31 is erased with the head 31 still in the position (C), then the head 31 is moved to the position (B) to erase, and the head 31 is moved to the position (A). To erase. By comparing the above signal levels (V _A ) and (V _C )
All the cases 1 to 25 shown in FIG. 5 are judged, and there is no unerased portion. Meanwhile, head 31
Runs out on the adjacent track, so a part of the adjacent track is erased. For the worst case in which the adjacent track touches the adjacent track boundary 27 or 28, the probability that the protruding head 31 erases the adjacent track is calculated to be 8th.
It becomes like the figure. The center is 0 to 10 μm, and the worst is 30 μm
Occurs with a probability of 8%.

FIG. 9 shows an algorithm of the track erasing method of the second embodiment of the present invention, which is a method for controlling the overerased amount of adjacent tracks. That is, the signal level (V _B ) is stored at the position (B). The position (B) is a reference position when the head 31 is stepwise moved from the adjacent track. The head 31 is moved a distance D from the position (B) to the outer peripheral side,
Position (A). Position storing the signal level (V _A) at (A). Next, move the head 31 to the inner side from position (A)
Move 2D (distance D from position (B)) to position (C). Position storing signal level (V _C) at (C). The stored signal levels (V _A ) and (V _B ) are compared, and if the signal level (V _A ) is high, the signal level (V _C ) is further compared, and the signal level (V _A ) is the signal level. If it is larger than 3 times the level (V _C ), the head 31 is moved to the position (B) and erased, the head 31 is moved to the position (A) and erased, and the head 31 is further moved to the position (A). It is moved to the outer peripheral side by a distance D and erased. That is, track erasing is performed at three positions, that is, the position (B), the position (A), and the position moved to the outer periphery by the distance D from the position (A). This case belongs to Case No.4,5,1
It is 0. When the signal level (V _A ) is equal to or smaller than 3 times the signal level (V _C ), the head 31 is moved to three positions (C), (B) and (A), and the respective positions are changed. To erase the track. Cases 3, 9 and 15 belong to this case. Signal level (V _A ) and signal level (V
_B) and compared to a case where the signal level (V _A) is the signal level (V _B) equal to or less compares the signal level (V _B) and the signal level (V _C). When the signal level (V _B ) is higher than the signal level (V _C ), the head 31 is moved to the position (C), the position (B) and the position (A), and the track is erased at each position. The ones that belong to this case are
Case No. 1,2,7,8,12,13,14,19,20,25. Conversely,
Signal level (V _B) If is less than or equal to the signal level (V _C) is 3 further signal level (V _C) and the signal level (V _A)
Compare with fold. When the signal level (V _C ) is greater than 3 times the signal level (V _A ), the head 31 is moved further toward the inner circumference side from the position (C) by a distance D to erase it, and then the head 31 is moved to the position ( Then, the head 31 is moved to position (B) for erasing. That is, track erasing is performed at three positions, that is, position (B), position (C), and a position that is moved inward by a distance D from position (C). Cases 16, 21, and 22 belong to this case. Conversely, if the signal level (V _C) is equal to or smaller than three times the signal level (V _A), the position (C), position (B), to move the head 31 to position (A), track erasure To do. Cases 6, 11, 12, 17, 18, 23, and 24 belong to this case. The reason why the triple number is used in the comparison between the signal levels (V _A ) and (V _C ) is as follows. That is, as described above, in the case of track erasing, the head 31 is moved by the distance D and track erasing is performed at three adjacent positions, but there are three cases in which the head 31 moves. That is, (1) When erasing at three positions (A), (B), and (C), (2)
When erasing at the positions (B), (A) and the position (A ') which is a distance D outside the position (A), (3) the position (B),
There is a case where it is erased at a position (C ′) which is a distance D inward from (C) and the position (C). The condition for shifting from case (1) to case (2) or from case (1) to case (3) is that the head 31 traces directly above the track 30 at position (A) or position (C). Yes (Case No. 3,9,11,15,17,23). On the other hand, in this embodiment, Wh
= 60 μm and D = 20 μm, and the position (A) and the position (C) are separated by a distance 2D, that is, 40 μm,
The signal output ratio of the signal reproduction level at the position (A) and the signal reproduction level at the position (C) is 3. 3 from here
The doubled numbers are used to compare the signal levels (V _A ) and (V _C ). In this second embodiment, the probability that the head 31 will protrude to the adjacent track and erase a part of the adjacent track is shown in FIG. In this case as well, the worst case is that the adjacent tracks touch the boundaries 27 and 28. The average erase width is 0 to 10 μm, and the worst 20 μm occurs at 24%.
There is no overerasure of 20 μm or more.

The most accurate determination and comparison of the signal level is to store the data over the entire circumference and determine the size. However, since the amount of data for the memory for one cycle is large, a RAM (random access. Memory) is required and not practical. The track position fluctuates during one revolution because the track 30 is eccentric. If this eccentric component is removed, the head output becomes a constant value, and even if sampling is performed at least one point per revolution An accurate comparison is possible with. To remove the eccentric component, the track 30 is divided into four equal parts or more and the sampling values of at least four points are arithmetically averaged to cancel the eccentric component. FIG. 11 shows a time chart of four sampling positions, in which the microcomputer 36 detects the trailing edge of one PG pulse generated for one rotation of the disk and the time until the trailing edge of the next PG pulse is detected ( 1 cycle) T is measured by a timer built in the microcomputer 36. One cycle T is divided into four and the time t ₂ is calculated. The time t ₁ from the detection of the falling edge of the PG pulse to the start of the first sampling is set in the microcomputer 36 in advance, and after the falling edge of the PG pulse is detected,
Sampling was performed 4 times at equal intervals (t ₂ ) and each point S ₁ , S ₂ ,
The outputs (V ₁ ), (V ₂ ), (V ₃ ), and (V ₄ ) at S ₃ and S ₄ are captured and stored, and arithmetically averaged to obtain the output (V _n ) (however,
n = A, B, or C). Therefore, the output (V _n ) is a highly accurate value because the influence of eccentricity is eliminated. Further, since one cycle T is fixed, the measurement of one cycle T may be unnecessary.

FIG. 12 shows the head feeding mechanism of the present invention. Place the disc motor 45 on the chassis 48, and
A disc 53 is fitted into 44 and rotated. The head 31 is fixed on a carriage 49, and the carriage 49 slides on a guide rail 50 whose both ends are fixed to the chassis 48. The shaft 44 penetrates the chassis 48 and has a cam body 41 having a large gear 42 on the periphery.
Is rotatably supported. A cam 47 is provided in the cam body 41, and a drive rod 46 fixed to the carriage 49 abuts on the outer peripheral portion of the cam 47. The carriage 49 is constantly urged toward the inner peripheral side by the elastic body 51. A stepping motor 54 is fixed on the chassis 48, and a pin-on gear 43 is fitted on the smoping motor 54. FIG. 13 shows the relationship between the cam body 41 and the pin-on gear 43, which is the large gear 42.
The rotation of the stepping motor 54 is transmitted to the cam body 41, and the carriage 49 is moved in parallel through the drive rod 46 that abuts the cam 47. The relationship between the pinion gear 43 and the large gear 42 is 1:10, and the reduction ratio is 1/10. Also cam
Reference numeral 47 denotes a linear cam having a gradient such that the carriage 49 moves by one track (100 μm) when the stepping motor 54 makes 10 steps. Therefore, it takes two steps to allow the allowable off-track amount D (20 μm), that is, to move the head 31 from the position (B) to the position (A) or (C). The drive rate of the stepping motor 54 is set to 500 PPS (pu
lse per second), 2ms per step,
The time required for two steps is 4 ms. Also, since it takes 10 steps to move to the adjacent track, this time is 20 ms. Since one rotation time of the disk 38 is 3600 rpm, it is 16.7 ms. Therefore, the time required for track erasing is short, 16.7 × 9 = 150.3 ms, and long, 167 ms.

FIG. 14 shows the angular accuracy (single pitch error) of the stepping motor 54 used in this magnetic recording / reproducing apparatus. The stepping motor 54 uses a bipolar two-phase excitation method. The accuracy for each step is ± 16%, but the accuracy for every two steps is as high as ± 4%. Therefore, if it is used in even steps, an inexpensive stepping motor can be used with a precision four times higher.

〔The invention's effect〕

According to the present invention, the head is moved from the initial position to the inner and outer sides by the allowable head-off track amount in two steps, and the track signal levels at the initial position and the inner and outer head positions are sampled. The head position is stored, the size is compared and discriminated, the track position is detected, and the head is moved by a distance D so as to cover the track position.
By erasing the already-recorded tracks at three adjacent positions, it is possible to complete the erasing in a short time without any unerased recorded tracks.

[Brief description of drawings]

1 to 5 are explanatory views showing a relative relationship between a track and a head and a signal sample for illustrating the principle of the tracking system according to the present invention, and FIG. 6 shows a magnetic recording / reproducing apparatus embodying the present invention. FIG. 7 is a block diagram of a head controller, FIG. 7 is a flow chart of a first embodiment of track erasing, FIG. 8 is a probability explanatory diagram of an adjacent track erase width, and FIG. 9 is a flow chart of a second embodiment of track erasing. FIG. 10 is a probability explanatory diagram of the adjacent track erase width, FIG. 11 is a timing chart of signal acquisition at four sampling positions, and FIG. 12 is a front view of a head feeding mechanism of a magnetic recording / reproducing apparatus embodying the present invention. FIG. 13 is a bottom view of the same, and FIG. 14 is a characteristic diagram of a stepping motor used in a magnetic disk storage device embodying the present invention. 30 …… Data track 31 …… Head 32 …… Amplifier 33 …… FM detection circuit 34 …… A / D conversion circuit 35 …… Microcomputer 54 …… Stepping motor 55 …… PG yoke 38 …… Disk 41 …… Cam Body 42 …… Large gear 43 …… Pinion gear 44 …… Stepping motor 46 …… Drive rod 47 …… Cam 49 …… Carriage

Continuation of the front page (56) Reference JP-A-62-31003 (JP, A) JP-A-59-84303 (JP, A) JP-A-58-194109 (JP, A)

Claims (1)

[Claims] 1. A track erasing method of a magnetic recording / reproducing apparatus for erasing a designated track among recording tracks formed concentrically on a recording medium by moving a head in a radial direction. Inner circumference side position,
The recording signal of the specified track is detected by the head at the intermediate position and the outer peripheral side position), the reproduction signal levels at the three positions are mutually compared, and the head is moved to the specified track according to the result of the mutual comparison. The above-mentioned head is moved to any three positions of five consecutive positions (inner-peripheral-side position, inner-peripheral-side position, intermediate position, outer-peripheral-side position, and outer-peripheral-side position) to erase a designated track. Track erasing method for magnetic recording / reproducing apparatus.