JPH0363903A - magnetic recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording/reproducing apparatus using a disk-shaped magnetic recording medium, typified by a video floppy apparatus.

Conventional technology In a magnetic recording/reproducing device that forms a large number of recording tracks on a single magnetic disk, such as a video floppy device, only one of the many recorded tracks is erased and a new one is created. It is necessary to record the signal. Erasing any track is achieved by applying a gradually decreasing alternating magnetic field to the magnetic disk via the magnetic head.

Regarding erasing in this conventional magnetic recording/reproducing device,
For example, it is shown in Japanese Patent Application Laid-Open No. 175905/1983. The timing for erasing is as shown in FIG. 3, and its operation will be explained.

When erasing, a start trigger pulse (a) is generated, and then the level is increased in sequence in synchronization with the PG pulse, which is the pulse for detecting one revolution of the magnetic disk, as shown in Figure 3 (C). Decreasing alternating current (erasing current)
The desired track is erased by switching the polarity of the track.

Problems to be Solved by the Invention However, in the above configuration, the direction (polarity) of the erasing current is switched every time the PG (phase detection pulse (b)) arrives, and therefore the magnetic disk is constantly There would be no problem if this switching is done at the same point and the transient time of this current switching is zero, but in reality there is a delay in the circuit system etc. and it takes time to switch the current, so this is not a problem. In this conventional erasing method, a part of the track (where the current is switched There is a problem in that erasing remains are generated in areas (portions), which become noise in the signal to be recorded next.

In view of the above, an object of the present invention is to provide a magnetic recording/reproducing device that does not leave erased data even when erasing is performed using an alternating current.

Means for Solving the Problems The present invention includes a rotational drive means for bringing a magnetic recording medium into contact with a magnetic head and rotationally driving the magnetic recording medium, and an alternating current generating means for applying an alternating current whose direction is reversed to the magnetic head. , the alternating current generating means is configured to apply the alternating current to the magnetic head, the direction of which is reversed and the current level is decreased, by setting a time longer than the time required for one revolution of the recording medium, and reversing the direction and decreasing the current level at each set time. It is a magnetic recording and reproducing device.

Effect of the present invention With the above-described configuration, when erasing a signal recorded on a magnetic disk, the polarity of the alternating current applied to the magnetic head is not always switched at the same location on the magnetic disk, but at the previous location. Erasing is always performed at a different location from the switching location, thus reducing the occurrence of unerased data.

Embodiment FIG. 1 is a block diagram showing the structure of an erasing circuit of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is an operation waveform diagram showing its operation timing.

In FIG. 1, 1 is a start trigger pulse generation circuit for providing a trigger to start erasing, 2 is a read timing control circuit that controls the read timing of the memory 4, 3 is a read circuit that specifies the read address of the memory, and 4 is a read timing control circuit that controls the read timing of the memory 4. 6 is a memory in which a digital value expressed in two's complement corresponding to an alternating current current pattern that provides good erasing characteristics is stored, and 6 is a memory D that converts the digital value outputted from the memory 4 into an analog current corresponding to the current pattern. /mu converter, 6 is an amplifier for passing the erase current, 7
8 is a magnetic head; 9 is a recording amplifier for recording signals on the magnetic disk; and 10 is amplifying the signal reproduced from the magnetic disk. This is a head amp that does. In FIG. 2, (tL) is the start trigger pulse,
(b) shows the PG (phase detection) pulse, and (C) shows the erase current pattern.

The erasing operation of the magnetic recording/reproducing apparatus of this embodiment configured as described above will be explained below.

When the magnetic disk rotates, a PG pulse (bl), which is a detection pulse for one rotation of the magnetic disk, is obtained by a well-known PG pulse generation circuit (not shown) and input to the terminal 21 of the read timing control circuit 2. After the magnetic head 8 is accessed to erase the desired trunk signal, when a start trigger pulse (tL) is input from the start trigger pulse generation circuit 1 to the terminal 22,
The read timing control circuit 2 operates the read circuit 3 to cause the erase current to flow from the timing of the PG pulse (b) immediately after the input start trigger pulse (2L). The readout circuit 3 outputs the address of the memory 4 in which the digital value corresponding to the erase current function e1 is stored. Then, the memory 4Ii receives the address value and outputs a positive digital value, and sends an initial erase current to the magnetic head 8 in the positive direction (the direction in which current flows into the magnetic head 8) through the D/MU converter 5, amplifier 6, and SW7. . Apply 1. Next, the magnetic disk rotates once and the next PG pulse (device 2
), the readout timing control circuit 2 starts time measurement, and controls the readout circuit 3 to change the current value after 72 hours, as shown in FIG. The readout circuit 3 then has erase current circuits with different polarities. The address of the memory 4 where the digital value corresponding to 2 is stored is output. The memory 4 receives the address value and outputs a negative digital value, and as before, sends a negative direction (direction of sucking current from the magnetic head 8) to the magnetic head 8 through the D/A converter 5, amplifier 6, and 5W7i. An erase current of "152" is applied. When the next PG pulse (unit 3) is input after one more revolution, the read timing control circuit 2 starts measuring time, and after 2 hours have elapsed at 2.
Erase electrician. The readout circuit 3 is controlled in the same manner as in the previous case to flow the signal 3. In this way, the read timing control circuit controls the PG pulse (b) as shown in FIG.
Every time is input, T64 after 2 in 3, I after 4T2. 5, the erase operation is completed repeatedly with the erase current 1s(c) reaching the OV bevel.

Here, the erase current is sequentially decreased, so that
>! 1.21>I"-51>ll-1>I"-1.

! In addition, as can be seen from the figure, the switching period T of the erase current
5 is T5 ``T1 + T2, which is set to be as long as the rotation period of the magnetic disk and also longer than the transient time of switching T2, so the polarity (direction) of the erase current is switched at the same location on the magnetic disk. That will no longer be the case.

As described above, according to this embodiment, the switching of the polarity of the alternating current for erasing is not performed at the blanking point of the magnetic disk, but changes with each rotation, and furthermore, the polarity of the alternating current for erasing is changed from the rotation period of the magnetic disk. Since the switching is also carried out in a long cycle, there will be no residual erasing in the transient portion at the time of switching, unlike in the conventional case.

In this embodiment, a PG pulse is used as a signal to obtain the switching timing of the erase current, but it is also possible to use a signal that is the same as the rotation period of the magnetic disk, such as a vertical synchronization signal that serves as a reference for the rotation phase. .

Furthermore, in this embodiment, the current switching is made periodic for ease of control, but as long as it is longer than the rotation period of the magnetic disk, the present invention can be used even if the current switching is not particularly periodic. It is possible.

As described in detail, according to the present invention, when erasing an arbitrary track, no erased residue is left on the track, and the practical effects thereof are great.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an erasing circuit of a magnetic recording/reproducing device according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram of erasing timing in the same embodiment, and FIG. 3 is an operation of conventional erasing timing. FIG. 2... Read timing control circuit,
3...readout circuit, 4...memory,
6...D/A converter, 8...Magnetic head.

Claims (3)

[Claims] (1) The alternating current generating means includes a rotation driving means for bringing a magnetic recording medium into contact with a magnetic head and rotationally driving the magnetic recording medium, and an alternating current generating means for applying an alternating current whose direction is reversed to the magnetic head, and the alternating current generating means includes: A magnetic recording and reproducing device characterized in that a time period longer than the time required for one rotation of the recording medium is set, and the alternating current whose direction reverses and the current level decreases is applied to the magnetic head every time the alternating current is applied to the magnetic head. Device. 2. The magnetic recording and reproducing apparatus according to claim 1, further comprising means for detecting the rotation of the magnetic recording medium, and the timing for switching the direction of the alternating current is created based on the output of the detecting means. (3) The magnetic recording medium has synchronization signal generation means serving as a reference for the rotational phase of the magnetic recording medium, and the timing for switching the direction of the alternating current is created based on the output of the synchronization signal generation means. magnetic recording and reproducing device.