JPS6162285A - Magnetic recording reproducing device - Google Patents

Abstract

PURPOSE:To erase a signal recorded at a magnetic disk properly without installing an exclusive-use erasing head by connecting a speed reducing mechanism and an erasing signal generating device and impressing an AC current from the erasing signal generating device through a recording and amplifying device to a head. CONSTITUTION:While a magnetic disk is rotated with lower speed at the time of erasing than at the time of recording and reproducing, an AC signal is impressed to a head, an AC magnetic field is essentially added with high frequency, the impressed time is made longer and a signal recorded at the magnetic disk is erased. For example, to a disk motor 1, a reference pulse generating device 7 for driving is connected through a speed reducing mechanism 11 of a driving circuit 8 for normal speed, a driving circuit 9 for low speed and a change-over switch 10, and at the time of recording and reproducing, the driving circuit 8 for normal speed is operated by a Low level signal and a magnetic disk 2 is driven and rotated at the normal speed, and on the other hand, at the time of erasing, the above-mentioned driving circuit 9 for speed is operated and the magnetic disk 2 is driven and rotated with low speed.

Description

[Detailed Description of the Invention] Technical Field> The present invention is for recording and reproducing video signals of landscapes, people, etc., and information signals such as date and time, shooting location, etc., in electronic still cameras, for example. The present invention relates to a magnetic recording/reproducing apparatus that is provided with a drive mechanism that drives and rotates a magnetic disk, and a head that applies an alternating current signal to the magnetic disk in order to record and reproduce video signals and information signals.

Conventional technology In the above device, when erasing a recorded video signal or information signal, the previously recorded signal was not erased but directly overlaid and recorded. This had the disadvantage that the reproduced images could become unclear or errors could occur in the reproduced information due to the influence of residual magnetism caused by the signals that had been transmitted.

Therefore, in general, so-called DC erasure, in which a DC signal is applied to the head to erase the head, has been carried out, but since this erasure saturates in one direction, the noise after erasure is large.
This had the disadvantage of causing distortion in the signals recorded afterwards.

Additionally, some devices are equipped with a dedicated erasing head, but these have the drawback of decreasing mechanical precision, such as the contact between the magnetic disk and the head and the head's track deviation.

<Object of the Invention> In view of the above points, an object of the present invention is to enable signals recorded on a magnetic disk to be erased satisfactorily by applying an alternating current signal without providing a dedicated erasing head.

<Structure of the Invention> In order to achieve the above object, the present invention provides the magnetic recording/reproducing device described at the beginning, in which the driving mechanism changes the driving rotational speed of the magnetic disk to a lower speed than that during recording/reproducing. A speed change mechanism is provided, and an erase signal generator is connected to a recording amplifier for the head, and the speed change mechanism and the erase signal generator are linked to enable the speed change mechanism to generate a low speed rotation state of the magnetic disk. accompany,
An alternating current signal from the erase signal generator is applied to the head via the recording amplifier.

In other words, during erasing, an alternating current signal is applied to the head while rotating the magnetic disk at a lower speed than during recording/playback, an alternating magnetic field is applied at essentially a high frequency, and the application time is lengthened to create a magnetic field. This erases the signals recorded on the disc.

<Example> Next, embodiments of the present invention will be described using the drawings.

@ Figure 1 is a block diagram showing an embodiment of the magnetic recording/reproducing apparatus of the present invention, and Figure 2 is a timing chart, which acts on a magnetic disk 2 driven and rotated by a disk motor 1 as an example of a drive mechanism. A head 3 is provided as shown in FIG. .

Video signals or information signals can be recorded on the track.
-1, and is configured to be able to reproduce those recorded signals.

A reference pulse generator 7 for driving is connected to the disk motor 1 via a speed change mechanism 11 consisting of a normal speed drive circuit 8, a low speed drive circuit 9, and a changeover switch 10. During recording and reproduction, The normal speed drive circuit 8 is actuated by the low level signal to drive and rotate the magnetic disk 2 at the normal speed, and during erasing, the low speed drive circuit 9 is actuated by the H level signal to rotate the magnetic disk 2. 2 is configured to be driven and rotated at a low speed.

That is, an AND circuit 12, an OR circuit 13, and a 17th lip 70 are connected to the drive circuit changeover switch 10.
An erase switch 15 is connected through the ANI circuit 12, and the erase switch 15 is operated to suppress the erase switch 15.
The high level pulse A is input to the 17th lip 70.
AND by high level pulse B from knob 14.
The Hi level pulse C is input from the Iilil path 12 to the OR circuit 13, and the Hi level pulse C is input from the OR circuit 13.
The level pulse E is input to the first flip 70 knob 14, and accordingly, the output is inverted and the 17th flip 70
The Q output F from the 0 knob 14 is input to the drive circuit selector switch 10 at Hi level, and the low speed drive circuit 9
The magnetic disk 2 is driven and rotated at a low speed.

PG pulses are taken out from the disk motor 1;
This PG pulse is input to the F-V converter 16 and its frequency is converted into a DC voltage, and its voltage percentage signal is input to the comparator 17 and compared with the set reference voltage REF.
When the voltage falls below the set reference voltage REF, that is, when the rotation speed changes from normal rotation speed for recording and playback to a specified low rotation speed, a Hi-level pulse G is sent to the 27th lip 70 knob 18.
It is configured to output . In the F-V converter 16, the response of the output voltage change to the input frequency change is slow, and there is a delay time in the conversion time. By effectively using this delay time as a margin time for stabilizing the speed change, the following During the erasing operation, the rotational speed of the disk motor 1 is reliably changed to a predetermined speed.

When a high-level pulse G is input from the comparator 17 to the 27th lip 70 tube 18, a high level pulse H is input from the 27th lip 70 tube 18 to the mono multi-biflator 19, and Pulse (2) is input as a single pulse from the ibrator 19 to the pulse counter 20, and the number of pulses J as a drive signal for the disk motor 1 begins to be counted. and,
Until the number of pulses reaches a specified number, the high level pulses K from the pulse counter 20 are sent to the erase signal generator 2.
1, a large alternating current signal for erasing is amplified by a recording amplifier 5 and applied to the head 3.
The signal recorded on one predetermined track of the track is erased.

Further, the high level pulse K from the pulse counter 20 is also input to the monomultiplier 22,
At the falling edge of this pulse, the mono multivibrator 22 outputs a pulse D, and the OR circuit 1
3, and the Q output F of the 17th lip 70 knob 14 is set to Hi level. llI level, the operation of the low speed drive circuit 9 is stopped, and the normal speed drive circuit 8 is operated.

The speed change mechanism 11 can be configured using various methods, such as attaching a gear type speed change mechanism to the disk motor and changing the drive rotation speed of the magnetic disk 2 between a normal rotation speed and a low rotation speed by gear change. configuration can be adopted.

<Effects of the Invention> As described above, according to the magnetic recording/reproducing device of the present invention,
By rotating the magnetic disk at a slower speed than during recording and playback and applying an AC signal to the head, recording and playback can be performed.
A read head is used to generate a magnetic flux large enough to saturate the magnetic disk in the gap area of the head, and to increase the number of alternating magnetic fluxes in the magnetic field during the decay period to the magnetic element to be sufficiently large. It is possible to use a dedicated erasing spatula.
It has become possible to erase signals recorded on magnetic disks using alternating current signals.

Furthermore, since no erasing head is provided, it is possible to avoid a decrease in mechanical precision caused by the erasing head.

[Brief explanation of drawings]

The drawings show an embodiment of the magnetic recording/reproducing apparatus of the present invention, with FIG. 1 being a block diagram and FIG. 2 being a timing chart. DESCRIPTION OF SYMBOLS 1... Drive mechanism, 2... Magnetic disk, 3... Hella V, 5... Recording amplifier, 11... Speed change mechanism, 21
... Erasing signal generator.

Claims (1)

[Claims] (1) A magnetic recording/reproducing apparatus provided with a drive mechanism for driving and rotating a magnetic disk, and a head for applying an alternating current signal to the magnetic disk in order to record and reproduce video signals and information signals. The drive mechanism is provided with a speed change mechanism that changes the driving rotational speed of the magnetic disk to a lower speed than that during recording and reproduction, and an erase signal generator is connected to a recording amplifier for the head,
The speed change mechanism and the erase signal generator are linked to each other, and when the speed change mechanism causes the magnetic disk to rotate at a low speed, an AC signal from the erase signal generator is transmitted to the head via the recording amplifier. A magnetic recording/reproducing device configured to apply an electric current.