JPS6123567B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording/reproducing device for reproducing information signals recorded on a magnetic recording medium such as a magnetic tape or a magnetic card, and in particular uses a magnetoresistive element as a magnetic head for reproduction. By doing so, we propose a technology that enables information signals to be reproduced from the back side of a magnetic recording medium.

Generally, in order to reproduce information signals recorded on various magnetic recording media, a reproducing magnetic head is placed on the surface side of the magnetic recording medium, that is, on the main surface side on which the magnetic layer on which information is written is placed, facing the magnetic layer. The recording signal is read out by extracting an electromotive force corresponding to a change in the magnetic pattern of the magnetic layer through a relative sliding operation between the magnetic recording medium and the magnetic head. The magnetic head is formed by depositing a magnetic layer on one side of a base layer. The arrangement on the surface side of the magnetic recording medium is necessary to avoid an increase in so-called isolation loss, in which the reproduction output decreases as the distance between the magnetic head surface and the magnetic layer, that is, the spacing increases. When a magnetic head is placed on the back side of a magnetic recording medium, that is, on the base layer side, spacing equal to at least the thickness of the base layer cannot be avoided, which increases isolation loss and reduces reproduction output. becomes. However, as is generally well known, the isolation loss is expressed as -54.6d/λ (dB), where d is the spacing and λ is the recording wavelength, and decreases as the recording wavelength becomes longer. Reproduction of a recorded signal having a sufficiently long recording wavelength does not necessarily require placing a magnetic head on the front side of the magnetic recording medium, and it is also possible to reproduce it from the base layer side on the back side. The shortest recording wavelength that can be reproduced from the base layer side is determined based on the recording magnetic field strength, the magnetic layer thickness, the base layer thickness, the gap length of the magnetic head, the reproduction efficiency, etc. Furthermore, in an electromagnetic induction type magnetic head, it depends on the relative movement speed v between the magnetic head and the magnetic recording medium. That is, since the reproduction output from the electromagnetic induction type magnetic head depends on the frequency f=v/λ of the recording signal, the shortest recording wavelength that can be reproduced from the base side changes depending on v. Therefore, when it is difficult to arrange the magnetic head on the surface side of the magnetic recording medium due to the structure of the recorded signal reproducing device, or when a complicated mechanism is required, the above-mentioned electromagnetic induction type magnetic head can be used for magnetic recording. If it is placed on the back side of the medium, it will be subject to various design constraints as mentioned above, and it will be a practical impediment, especially the need to set the value of v to a very large value, making it difficult to use. becomes. That is,
When magnetic tape is used as the magnetic recording medium,
An increase in v means an increase in the moving speed of the magnetic tape or magnetic head during reproduction, leading to a decrease in the information storage capacity of the entire magnetic tape or an increase in the output of the drive system.

On the other hand, when a magnetoresistive element is used as the magnetic head, the shortest recording wavelength can be determined without depending on the relative velocity v between the magnetic head and the magnetic recording medium, since the magnetoresistive element is of a magnetic flux response type, as is well known. be able to. Furthermore, since magnetoresistive elements can obtain approximately 10 times more reproduction output than conventional electromagnetic induction elements, they are more advantageous than electromagnetic induction elements when used as magnetic heads for reproducing signals from the base layer side. It has the conditions. Furthermore, a magnetoresistive element is manufactured by forming a magnetic thin film, a conductive film, and an insulating film on a substrate surface by a vacuum evaporation method, a plating method, etc., and then finely processing the film into a predetermined pattern by a chemical etching method, etc. It has the feature that the size per head can be made much smaller than conventional electromagnetic induction type magnetic heads.

The present invention is equipped with a thin film magnetic head using a magnetoresistive element having the above-mentioned characteristics, and by effectively utilizing the characteristics of the magnetoresistive element, when the running speed changes during rewinding or fast forwarding, etc. Another object of the present invention is to provide a new and useful recorded signal reproducing device that can accurately and easily reproduce position information signals (queue signals) from the back side of a magnetic recording medium.

Hereinafter, one embodiment of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a helical scan type cassette video tape recorder (VTR) device.

A supply reel 3 on which a video tape 2 is wound and a take-up reel 4 for winding the video tape 2 on the supply reel 3 are rotatably housed and held in the cassette 1. Of the supply reel 3 and take-up reel 4, the reel to which the video tape 2 is supplied is alternatively connected to a drive source and driven to rotate. On the running path of the video tape 2, from the side of the supply reel 3, a guide pin 5, a full-width erasing head 6, a rotary head drum 7, an audio erasing head 8, an audio control head 9, a pinch roller 10 for pinching the video tape 2, and a cartridge are arranged in order from the supply reel 3 side. pushtan roller 1
1 and a guide pin 5 on the take-up reel 4 side are arranged at appropriate positions. For example, two or four video heads are arranged circumferentially on the rotating head drum 7, and rotate at 200 to 300 revolutions per second in the opposite direction to the running direction of the video tape 2, that is, in the direction in which the relative speed between the video tape 2 and the video heads becomes faster. The video tape 2 is rotated at a certain speed in contact with or in a non-contact state, and one field is scanned in one rotation. Since the scanning method uses a helical scanning (diagonal scanning) method, the videotape 2 and the rotating drum 7
It comes into diagonal sliding contact with the circumferential surface at a certain angle.

When rewinding or fast-forwarding the videotape 1, the videotape 1 does not need to come into sliding contact with the rotating drum 7, so its running path is between the guide pin 5 on the supply reel 3 side, as shown by the solid line in FIG. It is located at a position that short-circuits the guide pin 5 on the take-up reel 4 side, and on the other hand, during recording and playback, the running path of the video tape 2 is changed, and as shown by the broken line in FIG. , audio erase head 8, and audio control head 9. This change in the running path of the video tape 2 is carried out by changing the position of the loading pole 12, which moves to press the video tape 2 against the rotation drum 7 from both sides of the rotation drum 7. The moving state of the loading pole 12 is indicated by arrows in FIG. At this time, the tension pole 13 placed on the side of the supply reel 3 rotates around one end and comes into contact with the back side of the video tape 2 at the position shown by the broken line in FIG. Gives pressure tension. During recording and playback, the take-up reel 4 is connected to a drive source, so the video tape 2 is sequentially fed out from the supply reel 3 to the take-up reel 4, and recorded and played back by the rotating drum 7. In addition to recording and reproducing, the rotating head drum 7 records video signals using a video head. The full width erase head 6 erases all the signals recorded on the video tape 2, and the audio erase head 8 erases only the audio signals recorded on the video tape 2. The track of the audio signal is formed at the edge of the video tape 2 in a straight line in the same direction as the running direction of the video tape 2. The audio control head 9 detects a control signal recorded on the video tape 2 in order to synchronize the video signal and the audio signal. The pinch roller 10 and the capstan roller 11 pinch the video tape 2 and keep the running speed of the video tape 2 constant on the circumferential surface of the rotating drum 7. The stability (jitter) of the reproduced image is closely related to the stability of the running state of the video tape 2, and in order to obtain this stable tape running, the pinching pressure drive by the pinch roller 10 and the capstan roller 11 and the above-mentioned A constant tension by the tension pole 13 is required.

In a VTR device having such an operating mechanism, a cue signal recorded on the video tape 2 is used to automatically detect the cue for each of a plurality of video and other information signals recorded on the video tape 2. When rewinding or fast-forwarding the video tape 2, the magnetic heads for reproducing cue signals can be installed on the front side of the video tape 2, that is, the outside of the cassette 1, and on the back side of the video tape 2, that is, the outside of the cassette 1. There are two possible mounting positions: inside and inside. However, when a magnetic head is attached to the front side of the video tape 2, the running path of the video tape 2 is changed during recording and playback, so an operating mechanism is required to move the magnetic head to a position where running of the video tape 2 cannot be prevented. becomes. If the magnetic head is attached to the back side of the video tape 2, such an operating mechanism is not necessary. Furthermore, the space in which the magnetic head is installed is generally small, and therefore it is desired that the magnetic head be as small as possible. In consideration of the above points, this embodiment has a structure in which a thin film magnetic head made of a thin film magnetoresistive element is attached to the tip of the tension pole 13 to reproduce cue signals during rewinding or fast forwarding. That is, when the cue signal detection is instructed during rewinding or fast forwarding, the back side of the video tape 2 running is at a position where the guide pin 5 on the supply reel 3 side and the guide pin 5 on the take-up reel 4 side are short-circuited. The tip of the tension pole 13 comes into contact with the thin film magnetic head, and a drive current is supplied to the thin film magnetic head to put it into operation and reproduce the cue signal. The tip of the tension pole 13 may be configured to be in constant contact with the video tape 2 during winding and fast forwarding. It is assumed that the recording of the queue signal is performed using the full width erasing head 6.

Figure 2 shows one example of the configuration of a thin film magnetic head consisting of a magnetoresistive element (MR element) used in this example.
It is a front view showing an example. 3A, B, and C are a side view, a front view, and a plan view, respectively, showing the tip portion of the tension pole 13 shown in FIG. 1.

The thin film magnetic head 20 has a magnetoresistive element 22 mainly made of permalloy (80Ni-Fe) on a substrate 21 made of glass or the like with a film thickness of about 300 Å and a width of about 1 mm.
It is deposited in a strip shape of mm by vapor deposition method or plating method,
Lead conductors 23 are layered on the substrate 21 from both ends of the magnetoresistive element 22 to form an electromotive force extraction section. The tip of the tension pole 13 is made of a rod-shaped body made of a non-magnetic material and has a diameter of about 5 mm, and is made of a thin film so that the thin film magnetoresistive element 22 is placed at a position about 80 μm away from the sliding surface with the video tape 2. A magnetic head 20 is embedded. A lead wire 24 is connected to the lead conductor 23, and the lead wire 24 extends outside the tension pole 13 and is connected to a detection circuit (not shown).

One of the cue signal reproduction waveforms when the cue signal (recording wavelength: about 1 mm, recording track width: about 10 mm) recorded during signal recording by the full-width erasing head 6 is reproduced by the thin film magnetic head 20 during rewinding or fast forwarding. An example is shown in FIG. The horizontal axis is the elapsed time,
The vertical axis represents the reproduction output Vpp (mV). If the base layer thickness of the video tape 2 used is 16 μm, the distance between the thin film magnetoresistive element 22 and the magnetic layer of the video tape 2, that is, the spacing, is about 0.1 mm. The reproduced waveform shown in FIG.
This is the reproduced waveform of the cue signal observed when a detection current of about 5 mA was applied to the 2.2 and no bias magnetic field was applied. As is clear from Figure 4, approximately 1 mV
It is confirmed that the reproduced output is obtained and the S/N ratio is sufficiently good.

For reproducing signals such as queue signals that do not necessarily require high-density recording, it is possible and effective to utilize the characteristics of the thin film magnetoresistive element 22 to reproduce recorded signals from the back surface of the magnetic recording medium. Similar results can be obtained not only by attaching the thin film magnetic head 20 to the tension pole 13 but also by attaching it to the guide pin 5 or other space within the cassette 1 as appropriate. Furthermore, in the above embodiment, the queue signal was recorded by recording the queue signal in the recording band of the video signal using the full-width erasing head 6.
It is likewise possible to record cue signals on the control track via the audio control head 9, as shown in FIG. Other number 10
As long as the signal is recorded with a track width of approximately μm or more, the object of the present invention can be achieved by adjusting the stripe length and mounting position of the thin film magnetoresistive element 22, no matter where the track positions are arranged. .

On the other hand, it is also possible to embed a conventional electromagnetic induction type magnetic head in the tension pole 13 or the like as in the above embodiment and reproduce the cue signal from the back side of the video tape 2, but in this case, as mentioned above, the magnetic head Since it is not a responsive type, it has the disadvantage that the playback output is not constant due to variations in the relative speed with respect to the video tape 2. In general, in a cassette-type VTR device, the running speed of the video tape 2 during rewinding or fast forwarding is not controlled to a constant speed, so for example, the tape running speed near the end of rewinding is the same as when rewinding starts. The average running speed is about 2 to 4 times faster than that of the cassette 1, and the average running speed varies greatly depending on the tape length, the diameter of the reel in the cassette 1, etc. Therefore, it is fully expected that fluctuations in the reproduced output will become large and the system will not be of practical use. However, since the magnetoresistive element is of a magnetic flux responsive type, the reproduction output of a magnetic head using this element is completely independent of the tape running speed and can always provide a constant output. This point is also a major feature of the present invention.

Additionally, since the base layer of magnetic tape is generally made of thin plastic foil such as polyethylene terephthalate (PET), it causes less wear to the contact body than the surface magnetic layer; The present invention also has the feature that there is no fear of damaging the magnetic layer and causing signal dropout.

Furthermore, when an electromagnetic dielectric magnetic head is applied to a magnetic recording device such as a cassette tape recorder, the magnetic head directly touches the tape during rewinding or fast forwarding when the tape is running at high speed, in order to avoid abrasion of the magnetic head. Designed to prevent contact. Therefore, when trying to reproduce a recorded signal such as a cue signal when rewinding or fast forwarding a tape, the conventional method requires a specially controlled device so that the distance between the magnetic head and the tape, that is, the spacing, does not become too large. It is necessary to do so. Moreover, in this case, there is a drawback that the fluctuation range of the spacing due to tape vibration is large, so that the fluctuation of the reproduction output is also large. However, by applying the present invention, for example, by embedding a magnetoresistive element in a guide pin inserted into the back surface of the tape, these drawbacks can be completely eliminated.

According to the present invention as explained in the above embodiments,
Signals with relatively long recording wavelengths such as queue signals,
(1) Regardless of the running speed of the magnetic recording medium, (2) without preventing the original functions of the device, (3) without adding any special operating mechanism, (4) without affecting the magnetic layer by scratches, etc. (5) It is possible to reliably and stably reproduce a good reproduction signal with less wear on the magnetoresistive element.

It is clear that the present invention can be practiced not only on magnetic tapes but also on any magnetic recording medium whose base layer thickness is not extremely thick.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a cassette-type video tape recorder device showing one embodiment of the present invention. FIG. 2 is a front view showing the structure of the thin film magnetic head used in the embodiment of FIG. 1. Figure 3 A, B, C
2 are a side view, a front view, and a plan view, respectively, showing the configuration of the tip portion of the tension pole shown in FIG. 1. FIG. FIG. 4 is a waveform diagram showing an example of the queue signal reproduction waveform reproduced in the embodiment of FIG. 1...Cassette, 2...Video tape, 6...
Full-width erase head, 7...Rotating drum, 8...
...Audio erase head, 9...Audio control head, 12...Loading pole,
13... Tension pole, 20... Thin film magnetic head, 21... Substrate, 22... Magnetoresistive element, 2
3... Lead conductor, 24... Lead wire.

Claims (1)

[Claims] 1. When the running speed of a magnetic recording medium in which a magnetic layer for signal recording is laminated on a base layer changes, such as during rewinding or fast forwarding, the base layer of the magnetic recording medium changes. A thin film magnetic head equipped with a magnetoresistive element is disposed facing the surface of the magnetic recording medium, and a position information signal (queue signal) recorded on the magnetic layer of the magnetic recording medium is reproduced by the thin film magnetic head. Features of magnetic recording signal reproducing device.